Overview of biochar production from preservative-treated wood with detailed analysis of biochar characteristics, heavy metals behaviors, and their ecotoxicity

Journal Pre-proof Overview of biochar production from preservative treated wood with detailed analysis of biochar characteristics, heavy metal behavior, and their ecotoxicity Jae-Young Kim, Shinyoung Oh, Young-Kwon Park

PII:

S0304-3894(19)31310-X

DOI:

https://doi.org/10.1016/j.jhazmat.2019.121356

Reference:

HAZMAT 121356

To appear in:

Journal of Hazardous Materials

Received Date:

21 July 2019

Revised Date:

23 September 2019

Accepted Date:

28 September 2019

Please cite this article as: Kim J-Young, Oh S, Park Y-Kwon, Overview of biochar production from preservative treated wood with detailed analysis of biochar characteristics, heavy metal behavior, and their ecotoxicity, Journal of Hazardous Materials (2019), doi: https://doi.org/10.1016/j.jhazmat.2019.121356

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Review article

Overview of biochar production from preservative treated wood with detailed analysis of biochar characteristics, heavy metal

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Jae-Young Kima1, Shinyoung Ohb1, Young-Kwon Parkc*

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behavior, and their ecotoxicity

These authors equally contributed to this study.

a

Division of Wood Chemistry, Forest Products Department, National Institute of Forest

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1

b

Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792,

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Republic of Korea

School of Environmental Engineering, University of Seoul, Seoul 02504, Republic of Korea

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c

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Science, 57 Hoegiro, Dongdaemun-gu, Seoul 02455, Republic of Korea

*Corresponding author.

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E-mail address: [email protected]

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Graphical Abstract

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Abstract

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Recent applications of biochar from preservative-treated wood are introduced. Fate of heavy metals during biochar preparation is discussed in-depth. Environmental impact of heavy metals retained in biochar should be considered. The challenges and future perspective of biochar utilization is proposed.

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   

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Highlights

Concerns over the disposal of preservative-treated wood waste and its related environmental

problems are the main driving forces of research into the recycling of preservative-treated wood. Preservative-treated wood waste composed of cellulose, hemicellulose, and lignin with several types of heavy metals can be recycled in various ways, such as wood-based composites, heavy metal extraction, energy recovery, etc. In particular, thermochemical conversion has attracted

considerable attention recently because energy can be recovered from biomass as liquid fuel and bio-oil, as well as produce bio-char with a high carbon content, which can be applied to valuable products, such as soil amendment, adsorbents, solid fuels, and catalyst supports. On the other hand, environmental issues, such as heavy metal volatilization and heavy metal leaching, are still a challenge. This review reports the state-of-the-art knowledge of biochar production from preservative-treated wood with the main focus on the feedstock, process

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technology, biochar characteristics, application, and environmental issues. This review provides important information for future studies into the recycling of preservative-treated woods into biochar.

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Keywords: Biochar, Pyrolysis, Preservative-treated wood, Arsenic, Chromium, Copper

1. Introduction

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Wood is one of the most valuable natural resources and is used traditionally in outdoor applications and building interiors. On the other hand, wood is an organic material composed

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of cellulose, hemicellulose, and lignin, which are is prone to biological/chemical corruption by both living organisms and abiotic components. Ross et al. reported that 10 % weight loss from

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fungal attack could reduce the strength of wood by almost 50 % [1]. Consequently, many studies have been performed to develop wood preservatives focusing on durability

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improvement and replacement cost reduction [2]. Chromated copper arsenate (CCA)-treated wood impregnated with hexavalent chromium

(Cr), copper (Cu), and pentavalent arsenic (As) is a representative preservative wood used widely in the industrial field, and is classified into three types depending on the metal content [3]. Humar et al. (2004) reported that the disposal amount of CCA-treated wood will reach about 16 x 106 m3 in 2020 [4]. Because CCA is a water-soluble heavy metal, soil and ground

water can be polluted because of their leaching by exposure to rainwater [5]. In particular, it has been reported that As can cause lung cancer in humans [6]. In addition, Cr can increase the risk of lung cancer [7]. Accordingly, CCA-treated wood was regulated in several countries approximately 30 years ago, which led to a rapid worldwide shift to copper-based wood preservatives [8]. Non-chromated arsenical water-borne preservatives, such as alkaline copper quaternary

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(ACQ), copper azole, copper citrate, and copper ethanolamine, have been used in numerous timber applications over the past decade [9]. Among them, ACQ, a mixture of quaternary ammonium compounds (QACs) and copper oxide, is commonly used because of its great biocidal activity against fungal or insect attack [10]. Despite its relative environmentally

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friendly properties compared to CCA, it will eventually be thrown away at the end of its life

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time and its waste management will become a major issue in the near future. Hasan et al. reported that the amount of leached metals was proportional to the degree of retention of the

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treated wood with higher retention degrees resulting in higher quantities in leachates and more mass of metals lost. Accordingly, Cu leached from the ACQ-treated wood is up to 15 times

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higher than the Cu leached from CCA-treated wood, which might result in soil and water pollution by eluted copper [11].

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Preservative-treated wood waste can be recycled as an energy source or other valuable products via a thermochemical conversion process. Pyrolysis is a thermochemical conversion

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process performed near 400 to 500 °C under limited oxygen conditions, which generates biooil as the main liquid product along with biochar (solid) and non-condensable gas [12]. Various types of biomass, including wood waste, agricultural residues, forestry residues, municipal solid waste, and animal manures, have been used as feedstock for biochar production [13]. Preservative-treated wood waste, such as CCA- and ACQ-treated wood, has been suggested as an alternative feedstock for bio-oil and biochar production [14, 15]. Recently, there has been

increasing interest in understanding biochar as a whole, particularly its prospects and applications to environmental management as well as valuable products because it is a multifunctional material related to greenhouse gas reduction, carbon sequestration, soil fertilization, contaminant immobilization, and water filtration [16]. According to previous research, the physicochemical characteristics of biochar are clearly influenced by the pyrolysis variables, including the feedstock type, temperature, residence time, and atmosphere [12].

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Among them, the feedstock characteristics and temperature are the main parameters affecting the biochar yields and characteristics [17, 18].

The environmental issues resulting from preservative-treated, wood-based biochar production should be considered because trace amounts of heavy metals, particularly As, can

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volatilize into the atmosphere when pyrolyzed. Most heavy metals are retained in biochar at

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even higher concentrations than in general soil or contaminated soil [19]. Therefore, heavy metals can leach into the soil and affect the ecosystem, particularly biomass growth [20]. When

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heavy metals are absorbed and transferred into biomass, they can cause metabolic disturbances, arrest cell division, cell death, or alter the structure and functions of various membranes or

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enzymes [21, 22].

Biochar application into valuable products, such as adsorbents, catalyst support, and

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batteries, has undergone rapid development recently [23-27]. Nevertheless, few review papers have introduced the behavior of heavy metals in preservative wood during biochar production

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as well as efficient methods to handle these metals. This paper introduces the state-of-the-art knowledge of the fate of heavy metals in preservative-treated wood during biochar production, including (1) the feedstock characteristics, (2) catalytic effect of heavy metals on the thermal degradation behavior of preservative-treated wood, (3) biochar characteristics from preservative-treated wood, (4) risks that heavy metals pose when they escape into the ecosystem during the biochar production process, and (5) heavy metal removal method from

biochar. Furthermore, the challenges and future prospects for the efficient and eco-friendly utilization of biochar are discussed. This report is expected to offer easy accessibility to an extensive readership and will be an influential reference for future directions of eco-friendly biochar production from preservative-treated wood.

2. Chemical composition of preservative-treated wood

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All woody biomass is composed of holocellulose (cellulose and hemicellulose) and lignin. Cellulose is a homogeneous polysaccharide comprised of ringed glucose through covalent bonding between the oxygen of the C1-hydroxyl group of glucose and the C4 of the adjoining glucose, called a β-1,4 glycosidic bond and is a major constituent of the primary cell walls of

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lignocellulosic biomass [28]. Hemicellulose is heterogeneous polysaccharide with diverse

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structures composed of xyloglucans, xylans, gluco-mannans, mannans, and β-(1,3 and 1,4)glucans [29]. Lignin is a relatively hydrophobic and amorphous aromatic polymer that consists

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of p-coumaryl, coniferyl, and sinapyl alcohols through diverse interunit covalent bonds, such as β-O-4, α-O-4, β-5, and biphenyl [30]. Preservative-treated wood has three main components

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and the inherent structure of lignocellulose is maintained, even after preservative treatment. Many studies have reported that the physicochemical characteristics of biochar are influenced

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by the feedstock type because of the varying proportions of each component [17, 31, 32]. Gai et al. examined the effects of the feedstock type and pyrolysis temperature on the

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physicochemical properties of biochar as well as its adsorption ability for nitrogen compounds [33]. Rutherford et al. compared the physicochemical properties of biochar obtained from cellulose, lignin, and pine wood to reveal the effects of the structural features of the feedstock on biochar production [31]. They concluded that cellulose decomposition would dominate char formation while lignin was more resistant to the charring reaction than cellulose in the low temperature region (< 300 °C). In addition, complex changes occur during the charring reaction

based on the carbon and oxygen content of feedstock by transforming aliphatic carbon to fused ring aromatic carbon. Table 1 lists the chemical and elemental composition of various preservative-treated wood materials. All feedstock presented in Table 1 had similar lignin contents ranging from 28.4 to 30.6 wt.% regardless of the preservative type. The holocellulose content ranged from 56.8 to 73.3 wt.% of biomass. Overall, there were no significant differences between the preservative-

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treated woods in terms of the carbon, hydrogen, and oxygen contents. On the other hand, the ACQ-treated wood contained 1.7 wt.% nitrogen, which was not detected in the other preservative woods. This trend might be caused by the presence of didecyldimethylammonium chloride (DDAC) that is generally coordinated with copper oxide (CuO2) during the

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preparation of the ACQ preservative for enhancing the resistance to fungal or insect attack [34].

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Preservative-treated wood contains not only organic sources, but also impregnated heavy metals, accounting for approximately 1-2 wt.%. Owing to the presence of heavy metals

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involving Cu, Cr, and As, biochar produced from preservative-treated wood retained a small amount of heavy metals that could not be evaporated over the pyrolysis temperature range.

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raw materials.

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Accordingly, it is very important to evaluate the amount of each heavy metal impregnated in

ACQ

CCBb

-

73.3

28.4

45.6

-

-

71.7 39.9 69.4 69.9

30.0 30.1 30.6 30.2 -

ND means not detected.

b

Copper chrome boron

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a

-

-

pr

32.9

6.6

e-

56.8

-

oo

Elemental composition (wt.%) C H N

-

NDa

-

-

44.6 47.9 -

6.4 6.3 -

1.2 0.3 -

48.3

5.9

ND

Pr

CCA

Chemical composition (wt.%) Holocellulose Lignin

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Preservative

f

Table 1. Chemical and elemental composition of preservative treated woods

Heavy metals (wt.%) Cu 0.26 Cr 0.48 As 0.31 Cu 0.28 Cr 0.49 As 0.43 Cu 0.28-0.55 Cr 0.43-0.91 As 0.42-0.76 Cu 1.63 Cu 0.2 Cu 0.19 Cu 0.97 Cu 0.29 Cu 0.96 Cr 0.37 B 0.57

Reference [35]

[15]

[36] [15] [14] [36] [37] [38]

3. Biochar preparation from preservative-treated wood waste 3.1 Thermochemical conversion process for biochar production Biochar can be produced from a range of thermochemical processes, involving fast/slow pyrolysis and gasification. Each process is distinguished by different reaction temperatures, heating rates, residence times of the volatiles, and atmosphere (N2, O2, and air) [39]. Hydrochar is another carbon-rich material possibly produced from lignocellulosic biomass or agricultural residue via a hydrothermal carbonization process (HTC) [40]. This process uses water as the

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reaction media and heat carrier under mild temperature conditions [41]. This review describes the representative biochar production technologies used widely in previous studies.

One of the typical processes studied is fast pyrolysis. The fast pyrolysis of biomass occurs

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under inert conditions within a very short reaction time (1-2 s). Bio-oil (liquid), biochar (solid),

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and non-condensable gas are formed as pyrolysis products. Typically, lower pyrolysis temperatures and longer residence times lead increase in biochar yield. Accordingly, it is

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important to choose the appropriate process parameters based on the purpose of the target product. The distribution of pyrolysis products varies considerably according to the process

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conditions [42]. Moreover, biomass easily undergoes structural alterations resulting in the formation of aromatic rings with increasing pyrolysis temperature [43, 44]. Therefore,

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conceptual approaches to embody the biochar characteristics form the basis for the gradual extension of aromaticity observed during pyrolysis [43].

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In addition to fast pyrolysis, slow pyrolysis is another feasible thermochemical conversion process that produces high‐ quality biochar with reliable and physicochemical characteristics appropriate for various applications [45]. During slow pyrolysis, the biomass is heated under a limited oxygen or inert atmosphere with relatively lower heating rates, between 1 and 30 °C min−1, than fast pyrolysis [46]. Similar to fast pyrolysis, slow pyrolysis is usually performed under atmospheric pressure within the pyrolysis temperature range. Under these conditions, the

biochar yields are relatively higher than those from fast pyrolysis, usually up to 20-40 wt.% based on the dry weight of feedstock, because slow pyrolysis favors the formation of char rather than bio-oil and non-condensable gas production. In particular, the longer residence time of volatiles in a fixed-bed reactor allowed those volatiles to be decomposed further into noncondensable gases [47]. The yield and physicochemical properties of biochar from slow pyrolysis are also dependent on the process parameters, such as the feedstock type, heating rate,

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temperature, and residence time. Gasification is performed at high temperatures, ranging from 700 to 900 °C, and is employed to produce syngas consisting of mainly CO, CO2, and H2 in the presence of other gaseous media, including nitrogen, air, oxygen, steam, or carbon dioxide [48]. Biochar from gasification

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produces higher energy yields with but more stable carbon than that from pyrolysis [49].

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Moreover, the O/C ratio of feedstock is a very important factor for achieving high gasification efficiency. Generally, low O/C ratio feedstock used in gasification leads to high efficiency

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gasification.

HTC has been used to convert organic feedstock with a high moisture content, such as

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lignocellulosic biomass and microalgae, into carbonaceous solid called hydrochar. HTC is based on the use of water as a reaction medium at relatively lower and higher pressures

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compared to pyrolysis (near subcritical region: 180 < T < 373 °C, 1.5 < P < 22 MPa), and has attracted widespread interest in recent years owing to its efficiency and convenience [50].

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Previous studies have shown that a biomass with moisture content can become a carbon abundant hydrochar with a high heating value and low moisture content similar to those a low heating value and high of lignite coal using HTC [51-53]. Typically, the HTC process is performed at high temperatures between 300 and 800 °C to produce carbon materials, such as nanotubes, graphite, and activated carbon [54]. In contrast, a low temperature HTC process carried out under 300 °C is a more environmentally friendly route that can transform several

chemical properties of hydrochar, including sizes, shapes, and surface functional groups [55]. Hydrolysis, dehydration, decarboxylation, aromatization, and condensation are the main reactions during HTC [56]. Nevertheless, the detailed reactions occurring are still unknown, making an investigation of the resulting reaction network impossible. According to Wiedner et al. hydrochars have a less stable structure with a large proportion of alkyl groups than biochars

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dominated by aromatic moieties [57].

3.2 Catalytic effect of metals on the thermal decomposition behavior of preservativetreated wood waste

Owing to the presence of heavy metals in preservative-treated woods, their thermal

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decomposition behaviors as well as their charring features could be different from typical wood

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during the biochar production process. Many studies have reported that biomass impregnated with alkali, alkali earth, and heavy metals remarkable catalytic effects on the distribution of

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pyrolysis products as well as biochar production [58-61]. Olsson et al. examined the emission of alkali metals released from biomass during pyrolysis using a surface ionization method [62].

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They reported that a small quantity of alkali metal was released between 180 to 500 °C due to decomposition of the organic structure, whereas most of the alkali metal had been volatilized

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at temperatures higher than 500 °C. Yip et al. also reported that approximately 10 to 20 wt.% of the alkali and alkaline earth metals had been volatilized during pyrolysis [63]. More than

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50 % of the alkali and alkaline earth metals, particularly K and Na, retained in biochar after pyrolysis existed as ions, whereas most of the Ca (65 %) and Mg (60 %) were bound chemically to organic species [64]. In the case of heavy metals, during the pyrolysis of CCA-treated wood, the amount of arsenic released at the pyrolysis temperature increased via two plausible pathways in the form of arsenic trioxide and arsenic pentoxide [65]. An artificial heavy metal impregnation study by Fu et al. showed that K2Cr2O7 and CuSO4 salts in biomass enhanced the

formation of levoglucosan during pyrolysis, resulting in a compositional difference in the resulting bio-oil. In addition, CrO3 resulted in low tar and high char yields with trace amounts of levoglucosan produced [66]. Kinata et al. examined the effects of Cu, Cr, and B on the pyrolysis of CCB-treated wood and their retention in the pyrolysis products [38]. They reported that Cr, Cu, and B impregnated in CCB-treated wood would induce low tar and high biochar formation. Furthermore, each metal could interact with the wood constituents to generate

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chemical bonds during impregnation. Fu et al. reported the formation of low molecular weight compounds originating from CCA-treated wood as pyrolysis temperature was increased from 275 to 350 ºC. The catalytic effects of Cr and Cu on the yields of pyrolytic products, as well as the chemical composition of bio-oil were also observed [67]. Helsen et al. (1999) examined the

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catalytic effects of the CCA components on the thermal degradation properties of

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lignocellulosic biomass [68]. They showed that Cr, As, and Cu in biomass have catalytic effects on the thermal degradation of cellulose and hemicellulose, resulting in overlap of both signals

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derived from hemicellulose and cellulose on the thermogravimetric analysis curve. Kim et al. showed that heavy metals in ACQ-treated wood and CCA-treated wood could reduce the

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maximum decomposition temperature region in both samples compared to control biomass according to thermogravimetric analysis, which suggested that the active pyrolysis regions

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changed because of the presence of heavy metals (Figure 1) [15]. Kinata et al. examined the catalytic effects of heavy metals on hydrochar formation. They examined the influence of CCB

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salts (Cu, Cr, and B) and process parameters, particularly residence time, on the yield of hydrochar and bio-oil [69]. According to their study, CCB salts could increase the yield of biooil and decrease the level of hydrochar formation during the HTC of CCB treated wood. Similar to the pyrolysis process, CCB salts were distributed between hydrochar and bio-oil. Additionally, the small amount of anion from wood preservative precursors was able to precipitate inside the wood [70], and has possibility to perform as a catalyst during the

thermochemical conversion process. Representatively, Cl, originated from typically used precursor CuCl2, mostly released as a form of HCl during the pyrolysis system reacted with water [71]. Precipitated Cl generally released around 280-400 °C, but has possibility to generate organochlorine (or C-Cl), which affected to volatile content and particle structure [72]. Moreover, Cl bound to surface functionalities on char surface could occur secondary reactions [73]. Sulfur, also contained in the wood preservatives such as creosote, also presented catalytic

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effect during the pyrolysis process. During the pyrolysis process, sulfur released to gas phase around 200-400 °C, but partial SO2 remained in the ash also catalyzed secondary reactions [74]. Meanwhile, it is important to investigate the effects of process parameters during thermochemical conversion process on the retention of heavy metals in biochar. However, few

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researches have been conducted on this issue. Stals et al. (2010) studied the effect of pyrolysis

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temperature on the retention of heavy metals including Zn, Pb, and Cd in biochar. They reported that most of the Zn and Pb was still remained in the char in moderate pyrolysis temperature

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(350 or 450 °C) while Cd was retained in char in lesser extent than Zn and Pb at 450 °C. With increasing pyrolysis temperature, the retention of heavy metals in biochar is significantly

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decreased due to their enhanced volatilization [75]. Previous studies have shown that heavy metals in preservative-treated wood clearly affect

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the thermal degradation features of biomass as well as the biochar yield during the thermochemical conversion process. Therefore, qualitative and quantitative analysis of heavy

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metals impregnated in biomass should be carried out before the biochar preparation process.

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Figure 1. Thermal decomposition behavior of CCA- and ACQ-treated wood measured by

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thermogravimetric analysis (with heating rate of 10 °C/min under N2 flow condition) [15]

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3.3 Biochar characteristics from preservative-treated wood waste and its application Typically, biochar from preservative-treated wood is characterized according to its

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application using elemental analysis, Brunauer–Emmett–Teller (BET) analysis, and inductively coupled plasma emission spectrometry (ICP-ES). Table 2 lists the biochar yield

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and chemical composition (elemental and metal) produced from several preservative-treated woods via pyrolysis or HTC. The yield of biochar from CCA, ACQ, and CCB-treated wood ranged from 16.8 to 41.3 wt.%, whereas that of hydrochar from CCB was 18.3 wt.%. Most heavy metals still remained in biochar or hydrochar, even after the pyrolysis and HTC. In addition to conventional analysis, Hata et al. examined the composition and structure of heavy metals remaining in biochar after the pyrolysis of CCA-treated wood using transmission

electron microscopy (TEM) [10]. They identified CCA derived compounds, including Cr2As4O12 and As2O3, by conventional TEM from the selected area electron diffraction patterns. Many studies related to the thermochemical conversion of preservative-treated wood have been carried out, but few studies focused on the characterization of the pyrolysis products (mainly bio-oil and biochar). In addition, few studies examined the applications of biochar derived from preservative-treated wood as valuable products, even its potential utilization to

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activated carbon or gas/solid adsorbent. One obstacle to the direct application of biochar from preservative-treated wood is the presence of heavy metals after the thermochemical conversion process. Helsen et al. attempted to recycle CCA-treated wood waste by pyrolysis at low temperatures. They reported that 98.0 % and 97.9 % of the Cr and Cu, respectively, had been

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retained in the resulting biochar after the pyrolysis process, whereas only small amount of

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heavy metals had evaporated into the gas phase or were quenched in bio-oil [76]. On the other hand, 82.3 % of As was still retained in the biochar, but the remainder of it was released during

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pyrolysis, particularly to the gas phase (14.7 %). Kim et al. also reported that 29.0 % of As was not captured in biochar or bio-oil because of its high volatility when exposed to heat during

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CCA treated wood pyrolysis [15].

Interestingly, the presence of heavy metals, such as Cr and Cu, in the activated carbon is

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considered an advantage because some metals have a positive effect on CO2 adsorption, as reported previously [77]. This suggests that the loaded metal ion group increases the CO2

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adsorption capacity through physical and chemical interactions [78]. Indeed, Botomé et al. examined the CO2 adsorption ability of activated carbon produced from CCA-treated wood [79]. They performed the chemical activation of biochar with H3PO4 under a CO2 flow to satisfy the microporous structure of activated carbon with pore sizes less than 1 nm. Consequently, the presence of Cr and Cu may have a positive effect on CO2 adsorption. Another biochar application is its use as an amendment for increasing the bioavailability

of retained metals to agricultural soils. Lucchini et al. reported that biochar produced from waste wood contaminated by large amounts of copper could result in different amounts of soil metal bioavailability and phytotoxicity according to the thermochemical conversion process (pyrolysis or combustion) and soil type [80]. They emphasized that qualitative and quantitative analysis of heavy metals in waste feedstock is essential before the large-scale utilization of biochar to soil. Similarly, Jonesa and Quilliam examined the effects of biochar derived from

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the pyrolysis of Cu-based preservative-treated wood on plant growth and soil quality [81]. They observed negative effects on the soil quality and plants with only high Cu-contaminated biochar, and concluded that low levels of Cu in biochar are needed for land applications to minimize the environmental risk.

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Although the pyrolysis and HTC of preservative-treated wood have been studied steadily

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over the past few years, there are still a number of challenges to overcome before biochar can be applied more widely (e.g., removal or control of retained heavy metals in biochar). Section

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5 introduces several technologies with respect to heavy metal control/removal.

ACQ

Slow pyrolysis 370 °C for 20 min

a

b

30

N2 16.8

Hydrothermal carbonization 350 °C, 48 bar 18.3 Tetralin as the hydrogen donating solvent

This is calculated as follow:

This is calculated as follow:

2.4

0.1

-

-

-

Cu 96.4 Cr 74.7 As 71.4 Cu 74.0 Cr 75.4 As 36.4

Application

Reference

Activated carbon for [79] CO2 capture -

Cu 2.2

[15] [80]

Soil amendment -

-

Cu 1.4

72.8

3.0

2.2

Cu 99.8

-

[15]

[81]

-

-

-

Cu 39.6 Cr 60.6 B 54.9

-

[38]

75.1

4.7

-

Cu + Cr + B 20.2

[69]

𝑇ℎ𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑚𝑒𝑡𝑎𝑙𝑠 𝑖𝑛 𝑏𝑖𝑜𝑐ℎ𝑎𝑟 (𝑔)

𝑇ℎ𝑒 𝑤𝑖𝑒ℎ𝑔𝑡 𝑜𝑓 𝑏𝑖𝑜𝑐ℎ𝑎𝑟 (𝑔)

Metal retention (%)a

-

𝑇ℎ𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑚𝑒𝑡𝑎𝑙𝑠 𝑖𝑛 𝑓𝑒𝑒𝑑𝑠𝑡𝑜𝑐𝑘 (𝑔) 𝑇ℎ𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑚𝑒𝑡𝑎𝑙𝑠 𝑖𝑛 𝑏𝑖𝑜𝑐ℎ𝑎𝑟 (𝑔)

0.9

75.5

Pr

-

O2

0.1

e-

N2 23.0

87.7

41.3

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CCB

N2 24.2

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Cu-based

Slow pyrolysis 700 °C under a constant flow (1.5 L/min) Fast pyrolysis 500 °C under a constant flow (10 L/min) Slow pyrolysis 550 °C under a reduced environment Fast pyrolysis 500 °C under a constant flow (10 L/min)

pr

Elemental Biochar yield composition (wt.%) (wt.%) C H N

Preservative Process condition

CCA

f

oo

Table 2. Chemical properties of biochar produced from preservative treated woods

× 100

× 100

4. Fate of heavy metals and their ecotoxicity Generally, biochar could improve the soil quality and reduce soil ecotoxicity by adsorbing potentially toxic trace elements (As, Cd, Cr, Cu, Hg, Ni, and Zn) and organic contaminants (agro-chemicals, antibiotics, and other hydrocarbons) from soil or water [82-90]. Environmentally persistent free radicals (EPFRs), which have an odd number of electrons, can have effects that last for hours to months when present under ambient conditions [91-95], and

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immobilize organic/inorganic contaminants bound to solid particles with resonance-stabilized states [96-103]. During pyrolysis, transition metals adsorb chemically on biomass. The electrons are then transferred to the metal center, and can produce the EPFRs [96, 104]. On the other hand, biochar can leach toxic heavy metals that can impede plant growth and cause a

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huge decline in agricultural production. Generally, biochar produced from biomass pyrolysis

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was presented negative charge, which resulted in the lower As adsorbing capacity than Cu and Zn [80]. Some of previous studies related to the biochar leaching test (toxicity characteristic

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leaching procedure, TCLP) described that heavy metals were easily leached under acidic conditions [105, 106]. Moreover, owing to their non-biodegradability, heavy metal-

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contaminated agriculture commodities can be toxic to humans and animals via the food chain, despite being essential elements (e.g. Cu, Cr, or As) [107-112]. Excessive amounts of heavy

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metals especially affect plant growth through physiological, biochemical, and morphological alterations, which can cause plant death [109, 110, 113, 114]. Moreover, the leached metals

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pollute the ground and surface water used for drinking. Heavy metal leachates are genotoxic, carcinogenic, and dangerous to human beings and animals [115, 116]. Recently, water-born preservative CCA treatments with pressure have been the most common method used to treat wood [117]. CCA-treated wood contains various levels of metals (e.g., 5.2–16.3 mg As g−1, 5.3–19.0 mg Cr g−1, 2.6–9.8 mg Cu g−1) [118, 119]. Because CCA can cause environmental problems, such as leaching and contaminating water or soil [15, 120], ACQ, which is

comprised of a non-toxic metal (62-71 % copper oxide and 29-38 % quaternary ammonium compound), has been proposed as an alternative wood preservative [10, 15]. The detailed ecotoxicity of major metals used in wood preservatives is described as follows.

Table 3. The amount of preservatives derived As, Cr, and Cu - limitation, typical amount in soil and biochar [15, 121]

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CCA treated wood ACQ treated wood Char from CCA treated wood Char from ACQ treated wood

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Soil Agricultural crops Land plants

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WHO/FAO European union standards Indian standard Detection limitation in organism

Guideline for safe limits of heavy metals (ppm) As Cu Cr 140 150 135-270 17.0 5.3 3.0 Composition of typical soil and agricultural crops (ppm) 2-100 5-3,000 4-15 0.2-1.0 0.02-7 4.15 0.2-1.0 Inorganic constituents (ppm) 4,309 2,806 4,944 17 16,255 46 9,483 12,534 22,516 131 11,1903 267

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4.1 Arsenic

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Figure 2. Scheme of fate of heavy metals on plants [21, 22]

Arsenic (As) exists in the environment in a range of oxidation states, e.g., As(V), As(III),

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and As(0). Trace amounts of As are essential for animals, whereas As becomes one of the most toxic and carcinogenic metals to organisms when the amounts of As are over 10 ppb (World

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Health Organization’s standard) [122-124]. Inorganic arsenic, which is a combination of As with oxygen, sulfur and chlorine, is more toxic than organic As (combined with hydrogen and carbon). The general types of As in water, soil or food are As(III) and As(V), whereas As(III) is prevalent in air [125, 126]. In particular, As(III), arsenite, is 60 times more toxic than As(V), arsenate [122, 127]. According to the following equation, the As in CCA-treated wood exists as inorganic arsenic.

2CrO3 + 2CuO + 4H3AsO4 → 2CuHAsO4 + 2CrAsO4 + 5H2O + 3/2O2 [128] Because 30–40 % of As (at 500–600 °C) or 10–20 % of As (at 850–1,500 °C) is volatilized at higher temperatures, concerns about air emissions during combustion or pyrolysis have increased [15]. Concentrated As places a limitation on the reuse of biochar because it is hazardous when exposed directly to humans or leached into the groundwater [117, 128]. Soils contaminated with As are both ecotoxic and carcinogenic [127]. Almost 200 enzymes

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that are related to the cellular energy pathway and DNA are inactivated by various amounts of As, and As can also substitute for phosphate in ATP [122]. In addition, the huge amount of As contamination (leaching from rocks and sediments [129], lacustrine alluvial soil or volcanic deposits [130, 131]) of water, particularly groundwater, has been recognized as a major

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problem.

4.2 Chromium

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Chromium (Cr), the second most common inorganic contaminant followed by Pb, has acute toxicity, mutagenicity, and carcinogenicity [132-134]. Therefore, Cr is hazardous in terrestrial

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environments when its concentration is increased, [135]. In particular, the redox form of hexavalent chromium (Cr(VI)) is more toxic to both humans and the environment than Cr(III),

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because it can readily pass the biological membrane [136], and is difficult to remove in the hydroxide forms [132, 137]. In contrast, the natural form of Cr(VI) is less ecotoxic than Cr(III)

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[138-142]. When the ecotoxicity of Cr(III) and Cr(VI) toward algae was tested with the ISO (International Organization for Standardization) medium, a carbonate and Cr hydroxide complex was formed, which restricted the redox reaction of Cr(III) or Cr(VI) with algal cells (Raphidocelis subcapitata). Modified Cr(III), which is referred to as Cr oxyhydroxides, in the media is potentially bioavailable [140, 143, 144], and the redox interaction between free ionic Cr(III) and algae increase its ecotoxicity [138]. Another study following the OECD guideline

2011 also reported that Cr(III) reduced its ecotoxicity by forming Cr(III) hydroxides with algae, daphnids, and bacteria [133, 138, 144]. Ostmeyer et al. suggested that chromic acid could accomplish oxidative attack or displace two hydrogen ions with the aromatics of lignin and form a stable ester [145, 146]. Carboxylate residues, which are presented in hemicellulose, could also complex easily with metal ions [145]. The reaction between Cr(VI) with a carboxylic acid or lignin aromatic ring is as follows:

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Cr2O72- + 6e- + 14H+ → 2Cr3+ + 7H2O [145] ACC, an alternative preservative to CCA that contains 31.8 % copper oxide and 68.2 % chromium trioxide [147], fixes Cr in preservative-treated wood but Cr can still leach when the

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pH is decreased, resulting in ecotoxic effects [145].

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4.3 Copper

Copper (Cu), an essential micronutrient for most living cells [148], is present in a less mobile

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and bioavailable form in contaminated soils, whereas it is often at higher levels in mineral soils [149]. Excess Cu in top soils can deposit in the labile soil pool and in the tissues of biological

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receptors [150], which might help adapt to the plant cellular Cu homeostasis [151], and affect their growth [152-154]. This could select Cu-tolerant plant species and regulate their

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populations [155], resulting in the reduction of soil biodiversity, e.g., earthworm, bacteria, and fungi [156-159]. In detail, the sites using wood preservation had small quantities of organics

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as nutrients and showed acidic features that are unfavorable for bioavailability [149, 159-162]. Biochar has attracted attention because of its ability to amend soils. When biochar is utilized

as a soil amendment, it improves the soil fertility and enhances plant productivity, but resists chemical or biological degradation. Moreover, the utilization of biochar can increase the cation exchange capacity of soil by improving the pH, water/nutrient retention, and xenobiotics degradation by microbials [163]. Moreover, biochar can immobilize trace elements on its

surface, such as Cu [159, 164, 165]. On the other hand, when the biochar from Cu-based preservative-treated wood is used as a soil amendment, the soil becomes contaminated with large amounts of Cu contained in biochar that disturbs plant growth, despite the high adsorption and desorption capacity of biochar [80, 166, 167]. Therefore, the addition of biochar obtained from preservative-treated wood to soil results in metal leaching, which results in a larger amount of Cu than the regulation limit, as well as increasing the plant nutrient (e.g., K)

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bioavailability. For example, more than 20 g of Cu was detected in one kilogram of biochar obtained from the pyrolysis of Cu-based preservative-treated wood. This amount was 200– 20,000 times higher than that in typical agricultural soils (0.001–0.1 g Cu kg−1). The amount was even higher than the limitation of common organic waste (e.g., biosolids, 0.50–5.0 g Cu

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kg−1; compost, 0.2 g Cu kg−1) [80]. The plant productivity was increased when ash, containing

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up to 25 % Cu contamination, was added to the soil, whereas the amount of free Cu2+ decreased with increasing soil pH, which adversely affected the shoot and root biomass [80, 81]. Alkaline

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copper quaternary compound (ACQ), which is an alternative to CCA, consists of copper oxide (67 %) and a quaternary ammonium compound, which is divided into types ACQ-B, -C, and –

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D [147], and another alternative preservative, ammoniacal copper citrate (CC), is composed of copper oxide (act as fungicide and insecticide) and citric acid to aid in the distribution of Cu

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within the wood structure [147]. Although those preservatives do not contain heavy metals, such as As and Cr, there are still concerns related to leaching and environmental impact [147].

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For example, acidic soil could leach huge amounts of As, Cr, and Cu [11, 168, 169]. In the case of alternative preservative (e.g. ACQ or CA)-treated wood, 4–10 times more Cu was leached compared to CCA-treated wood waste [170]. Therefore, ACQ- and CA-treated wood are more ecotoxic than CCA-treated wood [171, 172].

4.4 Other metals

Borate is also used as a wood preservative but only at places isolated from moisture, water, and ground contact according to the AWPA standard. This is because it consists of sodium salts, such as sodium octaborate, sodium tetraborate, and sodium pentaborate, which dissolve easily in water [147]. When borates are exposed to water, the tetrahydroxyborate ion [B(OH)]4− is formed, and the complex of the ion with polyols causes ecotoxicity, such as extra- and intra-cellular substrate isolation, restricted enzyme activity, or a modified membrane

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function as well as organism destruction [173]. Zinc is a major component of ammoniacal copper zinc arsenate, and zinc borate preservative is utilized in wood or wood-plastic composites [174]. Zn oxide nanoparticles can induce the cell death of eukaryotes, according to the inflammation and cytotoxicity of oxidative stress

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[174, 175]. Moreover Zn dust in concrobium (commercial mold cleaner) might induce the

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death of Reticulitermes flavipes and grain weevils, whereas ZnO (not inert) can cause termite mortality [174, 176]. Moreover, Al, Ca, Mg, and P, which are used in some wood preservatives,

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also limit crop production in acidic soils [82, 177].

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5. Heavy metal removal process from biochar

As mentioned above, heavy metals, which are generally used in wood preservatives, exhibit

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ecotoxicity and have a high boiling point. Cu or Cr are inevitably retained in biochar (small amounts of As can be volatilized) [15, 81]. In particular, according to a previous study,

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liquefaction effectively removes most of the metals (98 % As, 92 % Cr, and 83 % Cu) from the CCA-treated wood, with only approximately 2, 6, and 7 % of As, Cr, and Cu, respectively, remaining in the liquefied residue [178]. Because these heavy metals remaining reduced the bioavailability of the residue and caused ecotoxicity, a range of removal methods, including chemical or bioremediation, have been proposed [178, 179]. When As is combined with other elements, such as Fe [130], it can be converted to insoluble

compounds and be removed easily from drinking water via co-precipitation [123]. Because the biochar with EPFRs can also effectively remove Cr(VI) by reduction to Cr(III) [96, 180, 181], the precipitation of Cu and As was followed by the reduction of Cr(VI) to Cr(III) [178], which can effectively restrict leaching and plant uptake [80]. Therefore, the CCA metals recovered with the appropriate oxidation state can remove heavy metals from biochar efficiently [178, 182]. Typically, sequential extraction is performed to remove the preservative heavy metals

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[178], but neutralization and weak solute–solvent interactions makes the direct extraction of metal ions inefficient [128]. Sequential extraction removes CCA metals by a combination with wood component as an exchangeable/acid extractable form [178]. Chloride ions are usually loaded as an ion exchange resin and exchange with As [130].

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The structural and chemical features of biochar (e.g. porous and polyaromatic structure,

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large specific surface area, various functional groups on the surface, and high cation exchange capacity) can adsorb heavy metals easily and reduce the ecotoxicity of soil or water [43, 85,

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86, 90, 183-185]. Because the biochar from preservative-treated wood already contains adsorbed heavy metals, biochar regeneration (e.g. adsorbate desorption and adsorbate

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decomposition) also helps remove heavy metals from biochar [186]. The regenerated biochar retained its surface functional groups and removed organic carbon [187], whereas only 41.0 %

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of benzopyrene was regenerated even under mild conditions (150 °C) [186, 188]. Another method is solvent regeneration, which breaks the adsorption equilibrium between

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the biochar, solvent, and adsorbate under different temperature or pH conditions [186]. The acid-base regeneration method was also performed to remove adsorbate metals, and the inorganic acids (e.g. HCl and H2SO4) or alkali (e.g. NaOH) showed the most effective results [186]. Supercritical fluid, generally CO2, extraction is also performed to separate heavy metals with a small loss of biochar because of the short operating cycle at low temperatures. This

method can recover the adsorbate without physical or chemical modification [186]. Supercritical CO2 can easily dissolve chelated metal complexes with an organic ligand form, compared to the metal itself [128, 189]. CCA-treated wood retains these complexes or chelates after pyrolysis, which can be removed easily with extractants [178]. Ethylene diamine tetra acetic acid (EDTA) is a well-known efficient chelating agent, but EDTA single extraction is inefficient (As and Cr solubilization with 38 and 36 %, respectively) [190]. Dual extraction of

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As, Cr, and Cu using EDTA, nitrilo-triacetic acid, citric acid, oleic acid, oxalic acid, acetic acid, nitric acid, formic acid, oxalic acid, sulfuric acid, and hydrochloric acid could remove approximately 100 % of Cu and As. More than 90 % of Cr could also be removed by the dual extraction method with acids [191-194]. According to those studies, the leaching process

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successfully recycled the preservative-treated wood under strict conditions (e.g. acid

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concentration, temperature, and leaching retention time) [171].

Noble metal nanoparticles (e.g. Pd, Pt, Au, and Rh) as catalysts for Cr(VI) reduction to

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Cr(III) with HCOOH showed excellent performance that could effectively reduce the ecotoxicity of the heavy metal-containing biochar [132, 195-198].

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Inorganic As can be converted to the detoxified form by methylation [138]. To enhance the As extraction efficiency, the co-existence of metalloids with metals, or additional dissolution

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procedures of Fe/Mn/Al has been suggested [199, 200]. On the other hand, the dissolution of minerals had negative effects on the soil properties because the metal or metalloid become

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more unstable [201].

Generally, coagulation, destabilization of colloids, flocculation, and formation of bridges

between particles are performed to remove As from water [130]. As could be removed effectively when As(III) was oxidized to As(V) with zero-valent iron or an electrocoagulation process [202-205]. The electrokinetic technique, which prevents precipitation to remove heavy metals from CCA-contaminated soil, required nitric acid to neutralize and prevent the

migration of OH− ions into the soil with a low direct current [206].

Table 4. General scheme for behavior of CCA components [207] Reaction

Description Cu2+, CrO42− adsorption to wood

Initial (minutes)

Cr6+ reduction

Fluctuating pH

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Long term (weeks/months)

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Main (hours/days)

Products Cu2+/wood Cr6+/wood CrAsO4 Cu(OH)CrAsO4 CuCrO4 Cr(OH)3 Cr6+/wood complexes Cr3+/wood complexes Cu2+/wood complexes Not studied

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6. Challenges and future perspectives

Recently, biochar obtained from HTC or pyrolysis has been studied widely because

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pyrolysis or incineration is effective in generating energy [80]. The physical (e.g., water holding capacity, O2 content, and moisture level), chemical (e.g., pollutant immobilization and

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carbon sequestration), and biological (e.g., microbial abundance, diversity, and activity) properties of the soils can be improved synergistically by adsorbing various toxic compounds

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by biochar [208, 209]. Moreover, the application of biochar has also attracted interest because of the heavy metal or organic contamination resulting from industrialization [209]. Biochar can

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interact with polar compounds owing to its charged surface functional groups, resulting in the immobilization of heavy metals and agrochemicals, which prevent leaching into the crops [150, 210]. For example, the utilization of biochar as a soil amendment can hinder the uptake of toxic heavy metals (e.g. As, Cr, or Cu) by grain or plants. In addition to soil amendments, biochar also shows effective properties as a catalyst, fuel cells, and supercapacitors [26]. On the other hand, the performance improvement and biochar quality vary according to the feedstock and

pyrolysis conditions [209]. Therefore, a detailed study on the removal mechanisms of toxic compounds from biochar is required. In particular, the biochar produced from the pyrolysis of preservative-treated waste wood, already contains heavy metals (generally As, Cr, or Cu) and has different properties. As discussed above, those major heavy metals in the wood preservatives exhibit ecotoxicity, and are generally pollutants that need to be adsorbed on biochar. In this case, the leaching of those

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heavy metals from biochar should be conducted before biochar can find wider applications. For example, trace amounts of As in preservative-treated waste wood can be volatilized at high temperatures, whereas Cr requires oxidation under strict conditions (e.g. pH or temperature). The reaction conditions for producing biochar (pyrolysis or carbonization) and removing heavy

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metals need to be optimized for specific applications. On the other hand, few studies have

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examined the production or utilization of biochar obtained from preservative-treated waste wood. Therefore, further studies will be needed in this aspect. Because this process is type of

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total utilization of waste product, life-cycle analysis of this process is needed to confirm its benefits and alleviate environmental concerns. This can assist in the cost-effective use of

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7. Conclusions

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biochar from preservative waste wood for effective environmental applications.

The disposal of spent preservative-treated wood becomes more expensive because of strict

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regulations. Therefore, an economical way to recycle waste preservative-treated wood should be investigated. Generally, carbonaceous biochar, which is produced from pyrolysis, can adsorb heavy metals leached in soil or water, and reduce the ecotoxicity of contaminated sites, simultaneously enhancing the bioavailability of contaminated sites. On the other hand, when the preservative-treated wood is pyrolyzed, the biochar produced already contains preservative-derived heavy metals. Toxic trace elements used in wood preservatives, such as

arsenic (As), chromium (Cr), and copper (Cu), show reduced bioavailability in soil or water, which results in a decrease in plant growth or huge losses of agricultural productivity. The heavy metals fixed within the biochar restricted the adsorption efficiency and can leach into the environment. Therefore, the removal of heavy metals from biochar via extraction, methylation, oxidation, or coagulation has been investigated, but more study is needed. Biochar production from preservative-treated wood and its applications are economically promising

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processes in terms of total utilization of waste product, but techno-economic analysis or lifecycle analysis will be needed to confirm the profitability of the process.

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Acknowledgement

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This work was supported by the National Research Foundation of Korea (NRF) grant funded

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by the Korea government (MSIT) (No. 2018R1A2B2001121).

References

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[1] R.J. Ross, Wood handbook: wood as an engineering material, USDA Forest Service, Forest Products Laboratory, General Technical Report FPL-GTR-190, 2010: 509 p. 1 v., 190 (2010). [2] T.-J. Teng, M.N.M. Arip, K. Sudesh, A. Nemoikina, Z. Jalaludin, E.-P. Ng, H.-L. Lee, Conventional Technology and Nanotechnology in Wood Preservation: A Review, BioResources, 13 (2018) 9220-9252. [3] N. Ohgami, O. Yamanoshita, N.D. Thang, I. Yajima, C. Nakano, W. Wenting, S. Ohnuma, M. Kato, Carcinogenic risk of chromium, copper and arsenic in CCA-treated wood, Environmental pollution, 206 (2015) 456-460. [4] M. Humar, M. Bokan, S.A. Amartey, P. Kalan, F. Pohleven, Fungal bioremediation of copper, chromium and boron treated wood as studied by electron paramagnetic resonance, International biodeterioration & biodegradation, 53 (2004) 25-32. [5] M. Aceto, A. Fedele, Rain water effect on the release of arsenic, chromium and copper from treated wood, Fresenius Environmental Bulletin, 3 (1994) 389-394. [6] P.R. Taylor, Y. Qiao, A. Schatzkin, S. Yao, J. Lubin, B. Mao, J. Rao, M. McAdams, X. Xuan, J. Li, Relation of arsenic exposure to lung cancer among tin miners in Yunnan Province, China, Occupational and Environmental Medicine, 46 (1989) 881-886. [7] R. Luippold, K. Mundt, R. Austin, E. Liebig, J. Panko, C. Crump, K. Crump, D. Proctor, Lung cancer mortality among chromate production workers, Occupational and environmental medicine, 60 (2003) 451-457. [8] J. Hingston, C. Collins, R. Murphy, J. Lester, Leaching of chromated copper arsenate wood preservatives: a review, Environmental Pollution, 111 (2001) 53-66. [9] C.A. Bolin, S. Smith, Life cycle assessment of ACQ-treated lumber with comparison to wood plastic composite decking, Journal of Cleaner Production, 19 (2011) 620-629. [10] T. Hata, P. Bronsveld, T. Vystavel, B. Kooi, J.T.M. De Hosson, T. Kakitani, A. Otono, Y. Imamura, Electron microscopic study on pyrolysis of CCA (chromium, copper and arsenic oxide)-treated wood, Journal of Analytical and Applied pyrolysis, 68 (2003) 635-643. [11] A.R. Hasan, L. Hu, H.M. Solo-Gabriele, L. Fieber, Y. Cai, T.G. Townsend, Field-scale leaching of arsenic, chromium and copper from weathered treated wood, Environmental Pollution, 158 (2010) 1479-1486. [12] R. Li, J.J. Wang, L.A. Gaston, B. Zhou, M. Li, R. Xiao, Q. Wang, Z. Zhang, H. Huang, W. Liang, An overview of carbothermal synthesis of metal–biochar composites for the removal of oxyanion contaminants from aqueous solution, Carbon, 129 (2018) 674-687. [13] M.H. Duku, S. Gu, E.B. Hagan, Biochar production potential in Ghana—a review, Renewable and Sustainable Energy Reviews, 15 (2011) 3539-3551. [14] W.-M. Koo, S.-H. Jung, J.-S. Kim, Production of bio-oil with low contents of copper and chlorine by fast pyrolysis of alkaline copper quaternary-treated wood in a fluidized bed reactor, Energy, 68 (2014) 555-561. [15] J.-Y. Kim, T.-S. Kim, I.-Y. Eom, S.M. Kang, T.-S. Cho, I.G. Choi, J.W. Choi, Characterization of pyrolytic products obtained from fast pyrolysis of chromated copper arsenate (CCA)-and alkaline copper quaternary compounds (ACQ)-treated wood biomasses, Journal of hazardous materials, 227 (2012) 445-452. [16] Y.S. Ok, S.M. Uchimiya, S.X. Chang, N. Bolan, Biochar: Production, characterization, and applications, CRC press, 2015. [17] A. Enders, K. Hanley, T. Whitman, S. Joseph, J. Lehmann, Characterization of biochars to evaluate recalcitrance and agronomic performance, Bioresource technology, 114 (2012) 644653. [18] M.I. Bird, C.M. Wurster, P.H. de Paula Silva, A.M. Bass, R. De Nys, Algal biochar– production and properties, Bioresource technology, 102 (2011) 1886-1891.

Jo

ur

na

lP

re

-p

ro of

[19] H. Huang, W. Yao, R. Li, A. Ali, J. Du, D. Guo, R. Xiao, Z. Guo, Z. Zhang, M.K. Awasthi, Effect of pyrolysis temperature on chemical form, behavior and environmental risk of Zn, Pb and Cd in biochar produced from phytoremediation residue, Bioresource technology, 249 (2018) 487-493. [20] R. Li, H. Huang, J.J. Wang, W. Liang, P. Gao, Z. Zhang, R. Xiao, B. Zhou, X. Zhang, Conversion of Cu (II)-polluted biomass into an environmentally benign Cu nanoparticlesembedded biochar composite and its potential use on cyanobacteria inhibition, Journal of cleaner production, 216 (2019) 25-32. [21] A. Dadrasnia, C. Emenike, Remediation of Contaminated Sites, in, 2013, pp. 65-82. [22] H.P. Singh, P. Mahajan, S. Kaur, D.R. Batish, R.K. Kohli, Chromium toxicity and tolerance in plants, Environmental Chemistry Letters, 11 (2013) 229-254. [23] X. Gu, Y. Wang, C. Lai, J. Qiu, S. Li, Y. Hou, W. Martens, N. Mahmood, S. Zhang, Microporous bamboo biochar for lithium-sulfur batteries, Nano Research, 8 (2015) 129-139. [24] D. Mohan, A. Sarswat, Y.S. Ok, C.U. Pittman Jr, Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent–a critical review, Bioresource technology, 160 (2014) 191-202. [25] J. Lee, K.-H. Kim, E.E. Kwon, Biochar as a catalyst, Renewable and Sustainable Energy Reviews, 77 (2017) 70-79. [26] K. Qian, A. Kumar, H. Zhang, D. Bellmer, R. Huhnke, Recent advances in utilization of biochar, Renewable and Sustainable Energy Reviews, 42 (2015) 1055-1064. [27] R. Li, H. Deng, X. Zhang, J.J. Wang, M.K. Awasthi, Q. Wang, R. Xiao, B. Zhou, J. Du, Z. Zhang, High-efficiency removal of Pb (II) and humate by a CeO2–MoS2 hybrid magnetic biochar, Bioresource technology, 273 (2019) 335-340. [28] M. Jarvis, Chemistry: cellulose stacks up, Nature, 426 (2003) 611. [29] H.V. Scheller, P. Ulvskov, Hemicelluloses, Annual review of plant biology, 61 (2010). [30] J.-Y. Kim, S.Y. Park, J.H. Lee, I.-G. Choi, J.W. Choi, Sequential solvent fractionation of lignin for selective production of monoaromatics by Ru catalyzed ethanolysis, RSC Advances, 7 (2017) 53117-53125. [31] D.W. Rutherford, R.L. Wershaw, C.E. Rostad, C.N. Kelly, Effect of formation conditions on biochars: Compositional and structural properties of cellulose, lignin, and pine biochars, Biomass and Bioenergy, 46 (2012) 693-701. [32] L. Luo, C. Xu, Z. Chen, S. Zhang, Properties of biomass-derived biochars: Combined effects of operating conditions and biomass types, Bioresource Technology, 192 (2015) 83-89. [33] X. Gai, H. Wang, J. Liu, L. Zhai, S. Liu, T. Ren, H. Liu, Effects of feedstock and pyrolysis temperature on biochar adsorption of ammonium and nitrate, PloS one, 9 (2014) e113888. [34] C. Tascioglu, P. Cooper, T. Ung, Rate and extent of adsorption of ACQ preservative components in wood, Holzforschung, 59 (2005) 574-580. [35] S.N. Kartal, E. Terzi, H. Yılmaz, B. Goodell, Bioremediation and decay of wood treated with ACQ, micronized ACQ, nano-CuO and CCA wood preservatives, International Biodeterioration & Biodegradation, 99 (2015) 95-101. [36] L. Coudert, J.-F. Blais, G. Mercier, P. Cooper, L. Gastonguay, P. Morris, A. Janin, N. Reynier, Pilot-scale investigation of the robustness and efficiency of a copper-based treated wood wastes recycling process, Journal of hazardous materials, 261 (2013) 277-285. [37] T.L. Eberhardt, S. Lebow, K.G. Reed, Partial dissolution of ACQ-treated wood in lithium chloride/N-methyl-2-pyrrolidinone: Separation of copper from potential lignocellulosic feedstocks, Chemosphere, 86 (2012) 797-801. [38] S.E. Kinata, K. Loubar, M. Paraschiv, A. Bouslamti, C. Belloncle, M. Tazerout, Slow pyrolysis of CCB-treated wood for energy recovery: Influence of chromium, copper and boron on pyrolysis process and optimization, Journal of analytical and applied pyrolysis, 104 (2013)

Jo

ur

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-p

ro of

210-217. [39] S. Meyer, B. Glaser, P. Quicker, Technical, economical, and climate-related aspects of biochar production technologies: a literature review, Environmental science & technology, 45 (2011) 9473-9483. [40] I. Oliveira, D. Blöhse, H.-G. Ramke, Hydrothermal carbonization of agricultural residues, Bioresource technology, 142 (2013) 138-146. [41] H.S. Kambo, A. Dutta, A comparative review of biochar and hydrochar in terms of production, physico-chemical properties and applications, Renewable and Sustainable Energy Reviews, 45 (2015) 359-378. [42] A.V. Bridgwater, Review of fast pyrolysis of biomass and product upgrading, Biomass and bioenergy, 38 (2012) 68-94. [43] M. Keiluweit, P.S. Nico, M.G. Johnson, M. Kleber, Dynamic Molecular Structure of Plant Biomass-Derived Black Carbon (Biochar), Environmental Science & Technology, 44 (2010) 1247-1253. [44] C.A. Masiello, New directions in black carbon organic geochemistry, Marine Chemistry, 92 (2004) 201-213. [45] W. Song, M. Guo, Quality variations of poultry litter biochar generated at different pyrolysis temperatures, Journal of analytical and applied pyrolysis, 94 (2012) 138-145. [46] A.C. Lua, T. Yang, J. Guo, Effects of pyrolysis conditions on the properties of activated carbons prepared from pistachio-nut shells, Journal of analytical and applied pyrolysis, 72 (2004) 279-287. [47] M. Tripathi, J.N. Sahu, P. Ganesan, Effect of process parameters on production of biochar from biomass waste through pyrolysis: a review, Renewable and Sustainable Energy Reviews, 55 (2016) 467-481. [48] D. Neves, H. Thunman, A. Matos, L. Tarelho, A. Gómez-Barea, Characterization and prediction of biomass pyrolysis products, Progress in energy and combustion Science, 37 (2011) 611-630. [49] C.E. Brewer, K. Schmidt‐ Rohr, J.A. Satrio, R.C. Brown, Characterization of biochar from fast pyrolysis and gasification systems, Environmental Progress & Sustainable Energy: An Official Publication of the American Institute of Chemical Engineers, 28 (2009) 386-396. [50] D. Kim, K. Lee, K.Y. Park, Upgrading the characteristics of biochar from cellulose, lignin, and xylan for solid biofuel production from biomass by hydrothermal carbonization, Journal of industrial and engineering chemistry, 42 (2016) 95-100. [51] A.T. Quitain, M. Faisal, K. Kang, H. Daimon, K. Fujie, Low-molecular-weight carboxylic acids produced from hydrothermal treatment of organic wastes, Journal of hazardous materials, 93 (2002) 209-220. [52] M. Sevilla, A.B. Fuertes, The production of carbon materials by hydrothermal carbonization of cellulose, Carbon, 47 (2009) 2281-2289. [53] D. Kim, K. Lee, K.Y. Park, Hydrothermal carbonization of anaerobically digested sludge for solid fuel production and energy recovery, Fuel, 130 (2014) 120-125. [54] T. Hirose, T. Fujino, T. Fan, H. Endo, T. Okabe, M. Yoshimura, Effect of carbonization temperature on the structural changes of woodceramics impregnated with liquefied wood, Carbon, 40 (2002) 761-765. [55] Q. Wang, H. Li, L. Chen, X. Huang, Monodispersed hard carbon spherules with uniform nanopores, Carbon, 39 (2001) 2211-2214. [56] A. Funke, F. Ziegler, Hydrothermal carbonization of biomass: a summary and discussion of chemical mechanisms for process engineering, Biofuels, Bioproducts and Biorefining, 4 (2010) 160-177. [57] K. Wiedner, C. Rumpel, C. Steiner, A. Pozzi, R. Maas, B. Glaser, Chemical evaluation of

Jo

ur

na

lP

re

-p

ro of

chars produced by thermochemical conversion (gasification, pyrolysis and hydrothermal carbonization) of agro-industrial biomass on a commercial scale, Biomass and Bioenergy, 59 (2013) 264-278. [58] R. Fahmi, A. Bridgwater, L. Darvell, J. Jones, N. Yates, S. Thain, I. Donnison, The effect of alkali metals on combustion and pyrolysis of Lolium and Festuca grasses, switchgrass and willow, Fuel, 86 (2007) 1560-1569. [59] R. Fahmi, A. Bridgwater, I. Donnison, N. Yates, J. Jones, The effect of lignin and inorganic species in biomass on pyrolysis oil yields, quality and stability, Fuel, 87 (2008) 1230-1240. [60] I.-Y. Eom, J.-Y. Kim, T.-S. Kim, S.-M. Lee, D. Choi, I.-G. Choi, J.-W. Choi, Effect of essential inorganic metals on primary thermal degradation of lignocellulosic biomass, Bioresource technology, 104 (2012) 687-694. [61] P.R. Patwardhan, J.A. Satrio, R.C. Brown, B.H. Shanks, Influence of inorganic salts on the primary pyrolysis products of cellulose, Bioresource technology, 101 (2010) 4646-4655. [62] J.G. Olsson, U. Jäglid, J.B. Pettersson, P. Hald, Alkali metal emission during pyrolysis of biomass, Energy & Fuels, 11 (1997) 779-784. [63] K. Yip, F. Tian, J.-i. Hayashi, H. Wu, Effect of alkali and alkaline earth metallic species on biochar reactivity and syngas compositions during steam gasification, Energy & Fuels, 24 (2009) 173-181. [64] Y. Zhao, D. Feng, Y. Zhang, Y. Huang, S. Sun, Effect of pyrolysis temperature on char structure and chemical speciation of alkali and alkaline earth metallic species in biochar, Fuel Processing Technology, 141 (2016) 54-60. [65] T. Kakitani, T. Hata, T. Kajimoto, Y. Imamura, Two possible pathways for the release of arsenic during pyrolysis of chromated copper arsenate (CCA)-treated wood, Journal of hazardous materials, 113 (2004) 247-252. [66] Q. Fu, D.S. Argyropoulos, D.C. Tilotta, L.A. Lucia, Understanding the pyrolysis of CCAtreated wood: Part I. Effect of metal ions, Journal of Analytical and Applied Pyrolysis, 81 (2008) 60-64. [67] Q. Fu, D.S. Argyropoulos, D.C. Tilotta, L.A. Lucia, Products and Functional Group Distributions in Pyrolysis Oil of Chromated Copper Arsenate (CCA)-Treated Wood, as Elucidated by Gas Chromatography and a Novel 31P NMR-Based Method, Industrial & engineering chemistry research, 46 (2007) 5258-5264. [68] L. Helsen, E. Van den Bulck, S. Mullens, J. Mullens, Low-temperature pyrolysis of CCAtreated wood: thermogravimetric analysis, Journal of Analytical and Applied Pyrolysis, 52 (1999) 65-86. [69] S.E. Kinata, K. Loubar, M. Paraschiv, M. Tazerout, C. Belloncle, Catalytic hydroliquefaction of charcoal CCB (copper, chromium and boron)-treated wood for bio-oil production: Influence of CCB salts, residence time and catalysts, Applied energy, 115 (2014) 57-64. [70] S.H. Ahn, S.C. Oh, I.-G. Choi, H.-Y. Kim, I. Yang, Efficacy of wood preservatives formulated from okara with copper and/or boron salts, Journal of wood science, 54 (2008) 495501. [71] X. Zou, J. Yao, X. Yang, W. Song, W. Lin, Catalytic effects of metal chlorides on the pyrolysis of lignite, Energy & Fuels, 21 (2007) 619-624. [72] H. Chen, X. Chen, Z. Qiao, H. Liu, Release and transformation behavior of Cl during pyrolysis of torrefied rice straw, Fuel, 183 (2016) 145-154. [73] P.A. Jensen, F. Frandsen, K. Dam-Johansen, B. Sander, Experimental investigation of the transformation and release to gas phase of potassium and chlorine during straw pyrolysis, Energy & Fuels, 14 (2000) 1280-1285. [74] J.N. Knudsen, P.A. Jensen, W. Lin, K. Dam-Johansen, Secondary capture of chlorine and

Jo

ur

na

lP

re

-p

ro of

sulfur during thermal conversion of biomass, Energy & fuels, 19 (2005) 606-617. [75] M. Stals, E. Thijssen, J. Vangronsveld, R. Carleer, S. Schreurs, J. Yperman, Flash pyrolysis of heavy metal contaminated biomass from phytoremediation: influence of temperature, entrained flow and wood/leaves blended pyrolysis on the behaviour of heavy metals, Journal of Analytical and Applied Pyrolysis, 87 (2010) 1-7. [76] L. Helsen, E. Van den Bulck, J. Hery, Total recycling of CCA treated wood waste by lowtemperature pyrolysis, Waste Management, 18 (1998) 571-578. [77] A. Somy, M.R. Mehrnia, H.D. Amrei, A. Ghanizadeh, M. Safari, Adsorption of carbon dioxide using impregnated activated carbon promoted by Zinc, International journal of greenhouse gas control, 3 (2009) 249-254. [78] B.S. Caglayan, A.E. Aksoylu, CO2 adsorption on chemically modified activated carbon, Journal of hazardous materials, 252 (2013) 19-28. [79] M.L. Botomé, P. Poletto, J. Junges, D. Perondi, A. Dettmer, M. Godinho, Preparation and characterization of a metal-rich activated carbon from CCA-treated wood for CO2 capture, Chemical Engineering Journal, 321 (2017) 614-621. [80] P. Lucchini, R. Quilliam, T.H. DeLuca, T. Vamerali, D.L. Jones, Increased bioavailability of metals in two contrasting agricultural soils treated with waste wood-derived biochar and ash, Environmental Science and Pollution Research, 21 (2014) 3230-3240. [81] D.L. Jones, R. Quilliam, Metal contaminated biochar and wood ash negatively affect plant growth and soil quality after land application, Journal of hazardous materials, 276 (2014) 362370. [82] K.N. Palansooriya, Y.S. Ok, Y.M. Awad, S.S. Lee, J.-K. Sung, A. Koutsospyros, D.H. Moon, Impacts of biochar application on upland agriculture: A review, Journal of environmental management, 234 (2019) 52-64. [83] M. Ahmad, S.S. Lee, X. Dou, D. Mohan, J.-K. Sung, J.E. Yang, Y.S. Ok, Effects of pyrolysis temperature on soybean stover-and peanut shell-derived biochar properties and TCE adsorption in water, Bioresource technology, 118 (2012) 536-544. [84] M.I. Inyang, B. Gao, Y. Yao, Y. Xue, A. Zimmerman, A. Mosa, P. Pullammanappallil, Y.S. Ok, X. Cao, A review of biochar as a low-cost adsorbent for aqueous heavy metal removal, Critical Reviews in Environmental Science and Technology, 46 (2016) 406-433. [85] J. Liang, Z. Yang, L. Tang, G. Zeng, M. Yu, X. Li, H. Wu, Y. Qian, X. Li, Y.J.C. Luo, Changes in heavy metal mobility and availability from contaminated wetland soil remediated with combined biochar-compost, 181 (2017) 281-288. [86] L. Beesley, E. Moreno-Jiménez, J.L. Gomez-Eyles, E. Harris, B. Robinson, T. Sizmur, A review of biochars’ potential role in the remediation, revegetation and restoration of contaminated soils, Environmental pollution, 159 (2011) 3269-3282. [87] W.-W. Tang, G.-M. Zeng, J.-L. Gong, Y. Liu, X.-Y. Wang, Y.-Y. Liu, Z.-F. Liu, L. Chen, X.-R. Zhang, D.-Z. Tu, Simultaneous adsorption of atrazine and Cu (II) from wastewater by magnetic multi-walled carbon nanotube, Chemical Engineering Journal, 211 (2012) 470-478. [88] G. Yang, L. Tang, G. Zeng, Y. Cai, J. Tang, Y. Pang, Y. Zhou, Y. Liu, J. Wang, S. Zhang, Simultaneous removal of lead and phenol contamination from water by nitrogen-functionalized magnetic ordered mesoporous carbon, Chemical Engineering Journal, 259 (2015) 854-864. [89] H. Wang, X. Yuan, G. Zeng, Y. Wu, Y. Liu, Q. Jiang, S. Gu, Three dimensional graphene based materials: Synthesis and applications from energy storage and conversion to electrochemical sensor and environmental remediation, Advances in colloid and interface science, 221 (2015) 41-59. [90] P. Wang, L. Tang, X. Wei, G. Zeng, Y. Zhou, Y. Deng, J. Wang, Z. Xie, W. Fang, Synthesis and application of iron and zinc doped biochar for removal of p-nitrophenol in wastewater and assessment of the influence of co-existed Pb (II), Applied Surface Science, 392 (2017) 391-

Jo

ur

na

lP

re

-p

ro of

401. [91] S. Lomnicki, H. Truong, E. Vejerano, B. Dellinger, Copper Oxide-Based Model of Persistent Free Radical Formation on Combustion-Derived Particulate Matter, Environmental Science & Technology, 42 (2008) 4982-4988. [92] E. Vejerano, S. Lomnicki, B. Dellinger, Formation and Stabilization of CombustionGenerated Environmentally Persistent Free Radicals on an Fe(III)2O3/Silica Surface, Environmental Science & Technology, 45 (2011) 589-594. [93] E. Vejerano, S. Lomnicki, B. Dellinger, Lifetime of combustion-generated environmentally persistent free radicals on Zn(ii)O and other transition metal oxides, Journal of Environmental Monitoring, 14 (2012) 2803-2806. [94] E. Vejerano, S.M. Lomnicki, B. Dellinger, Formation and Stabilization of CombustionGenerated, Environmentally Persistent Radicals on Ni(II)O Supported on a Silica Surface, Environmental Science & Technology, 46 (2012) 9406-9411. [95] W. Gehling, B. Dellinger, Environmentally Persistent Free Radicals and Their Lifetimes in PM2.5, Environmental Science & Technology, 47 (2013) 8172-8178. [96] X. Ruan, Y. Sun, W. Du, Y. Tang, Q. Liu, Z. Zhang, W. Doherty, R.L. Frost, G. Qian, D.C. Tsang, Formation, characteristics, and applications of environmentally persistent free radicals in biochars: A review, Bioresource technology, (2019). [97] J. Luo, X. Li, C. Ge, K. Müller, H. Yu, P. Huang, J. Li, D.C. Tsang, N.S. Bolan, J. Rinklebe, Sorption of norfloxacin, sulfamerazine and oxytetracycline by KOH-modified biochar under single and ternary systems, Bioresource technology, 263 (2018) 385-392. [98] Q. Chen, M. Wang, Y. Wang, L. Zhang, J. Xue, H. Sun, Z. Mu, Rapid determination of environmentally persistent free radicals (EPFRs) in atmospheric particles with a quartz sheetbased approach using electron paramagnetic resonance (EPR) spectroscopy, Atmospheric Environment, 184 (2018) 140-145. [99] B. Dellinger, S. Lomnicki, L. Khachatryan, Z. Maskos, R.W. Hall, J. Adounkpe, C. McFerrin, H. Truong, Formation and stabilization of persistent free radicals, Proceedings of the Combustion Institute, 31 (2007) 521-528. [100] X. Yang, I.K.M. Yu, D.-W. Cho, S.S. Chen, D.C.W. Tsang, J. Shang, A.C.K. Yip, L. Wang, Y.S. Ok, Tin-Functionalized Wood Biochar as a Sustainable Solid Catalyst for Glucose Isomerization in Biorefinery, ACS Sustainable Chemistry & Engineering, 7 (2019) 4851-4860. [101] F. Yang, S. Zhang, H. Li, S. Li, K. Cheng, J.-S. Li, D.C.W. Tsang, Corn straw-derived biochar impregnated with α-FeOOH nanorods for highly effective copper removal, Chemical Engineering Journal, 348 (2018) 191-201. [102] F. Yang, S. Zhang, Y. Sun, K. Cheng, J. Li, D.C.W. Tsang, Fabrication and characterization of hydrophilic corn stalk biochar-supported nanoscale zero-valent iron composites for efficient metal removal, Bioresource Technology, 265 (2018) 490-497. [103] F. Yang, S. Zhang, D.-W. Cho, Q. Du, J. Song, D.C.W. Tsang, Porous biochar composite assembled with ternary needle-like iron-manganese-sulphur hybrids for high-efficiency lead removal, Bioresource Technology, 272 (2019) 415-420. [104] G. Fang, J. Gao, C. Liu, D.D. Dionysiou, Y. Wang, D. Zhou, Key Role of Persistent Free Radicals in Hydrogen Peroxide Activation by Biochar: Implications to Organic Contaminant Degradation, Environmental Science & Technology, 48 (2014) 1902-1910. [105] P. Devi, A.K. Saroha, Risk analysis of pyrolyzed biochar made from paper mill effluent treatment plant sludge for bioavailability and eco-toxicity of heavy metals, Bioresource Technology, 162 (2014) 308-315. [106] A.P. Puga, L.C.A. Melo, C.A. de Abreu, A.R. Coscione, J. Paz-Ferreiro, Leaching and fractionation of heavy metals in mining soils amended with biochar, Soil and Tillage Research, 164 (2016) 25-33.

Jo

ur

na

lP

re

-p

ro of

[107] C. Keller, M. Rizwan, J.-C. Davidian, O. Pokrovsky, N. Bovet, P. Chaurand, J.-D. Meunier, Effect of silicon on wheat seedlings (Triticum turgidum L.) grown in hydroponics and exposed to 0 to 30 µM Cu, Planta, 241 (2015) 847-860. [108] I.E. Zaheer, S. Ali, M. Rizwan, M. Farid, M.B. Shakoor, R.A. Gill, U. Najeeb, N. Iqbal, R. Ahmad, Citric acid assisted phytoremediation of copper by Brassica napus L, Ecotoxicology and environmental safety, 120 (2015) 310-317. [109] M. Rizwan, S. Ali, M.F. Qayyum, M. Ibrahim, M. Zia-ur-Rehman, T. Abbas, Y.S. Ok, Mechanisms of biochar-mediated alleviation of toxicity of trace elements in plants: a critical review, Environmental Science and Pollution Research, 23 (2016) 2230-2248. [110] S. Ali, A. Chaudhary, M. Rizwan, H.T. Anwar, M. Adrees, M. Farid, M.K. Irshad, T. Hayat, S.A. Anjum, Alleviation of chromium toxicity by glycinebetaine is related to elevated antioxidant enzymes and suppressed chromium uptake and oxidative stress in wheat (Triticum aestivum L.), Environmental Science and Pollution Research, 22 (2015) 10669-10678. [111] T. Tian, B. Ali, Y. Qin, Z. Malik, R.A. Gill, S. Ali, W. Zhou, Alleviation of lead toxicity by 5-aminolevulinic acid is related to elevated growth, photosynthesis, and suppressed ultrastructural damages in oilseed rape, BioMed research international, 2014 (2014). [112] M. Adrees, S. Ali, M. Rizwan, M. Zia-ur-Rehman, M. Ibrahim, F. Abbas, M. Farid, M.F. Qayyum, M.K. Irshad, Mechanisms of silicon-mediated alleviation of heavy metal toxicity in plants: a review, Ecotoxicology and Environmental Safety, 119 (2015) 186-197. [113] M.A. Farooq, L. Li, B. Ali, R.A. Gill, J. Wang, S. Ali, M.B. Gill, W. Zhou, Oxidative injury and antioxidant enzymes regulation in arsenic-exposed seedlings of four Brassica napus L. cultivars, Environmental Science and Pollution Research, 22 (2015) 10699-10712. [114] M.Z.-u. Rehman, M. Rizwan, A. Ghafoor, A. Naeem, S. Ali, M. Sabir, M.F. Qayyum, Effect of inorganic amendments for in situ stabilization of cadmium in contaminated soils and its phyto-availability to wheat and rice under rotation, Environmental Science and Pollution Research, 22 (2015) 16897-16906. [115] A.H. Moghaddam, C.N. Mulligan, Leaching of heavy metals from chromated copper arsenate (CCA) treated wood after disposal, Waste Management, 28 (2008) 628-637. [116] J.R. Jambeck, T. Townsend, H. Solo-Gabriele, Leaching of chromated copper arsenate (CCA)-treated wood in a simulated monofill and its potential impacts to landfill leachate, Journal of Hazardous Materials, 135 (2006) 21-31. [117] T.M. Tolaymat, T.G. Townsend, H. Solo-Gabriele, Chromated copper arsenate-treated wood in recovered wood, Environmental Engineering Science, 17 (2000) 19-28. [118] A. Janin, J.-F. Blais, G. Mercier, P. Drogui, Optimization of a chemical leaching process for decontamination of CCA-treated wood, Journal of hazardous materials, 169 (2009) 136145. [119] L. Helsen, E. Van den Bulck, Review of disposal technologies for chromated copper arsenate (CCA) treated wood waste, with detailed analyses of thermochemical conversion processes, Environmental pollution, 134 (2005) 301-314. [120] T. Townsend, H. Solo-Gabriele, T. Tolaymat, K. Stook, N. Hosein, Chromium, copper, and arsenic concentrations in soil underneath CCA-treated wood structures, Soil and Sediment Contamination, 12 (2003) 779-798. [121] M.L. Alonso, F.P. Montaña, M. Miranda, C. Castillo, J. Hernández, J.L. Benedito, Interactions between toxic (As, Cd, Hg and Pb) and nutritional essential (Ca, Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, Zn) elements in the tissues of cattle from NW Spain, Biometals, 17 (2004) 389-397. [122] R.N. Ratnaike, Acute and chronic arsenic toxicity, Postgraduate medical journal, 79 (2003) 391-396. [123] V. Chandra, J. Park, Y. Chun, J.W. Lee, I.-C. Hwang, K.S. Kim, Water-dispersible

Jo

ur

na

lP

re

-p

ro of

magnetite-reduced graphene oxide composites for arsenic removal, ACS nano, 4 (2010) 39793986. [124] D. Mohan, C.U. Pittman, Arsenic removal from water/wastewater using adsorbents—A critical review, Journal of Hazardous Materials, 142 (2007) 1-53. [125] K. Jomova, Z. Jenisova, M. Feszterova, S. Baros, J. Liska, D. Hudecova, C. Rhodes, M. Valko, Arsenic: toxicity, oxidative stress and human disease, Journal of Applied Toxicology, 31 (2011) 95-107. [126] M.C.F. Magalhães, Arsenic. An environmental problem limited by solubility, in: Pure and Applied Chemistry, 2002, pp. 1843. [127] L.Q. Ma, K.M. Komar, C. Tu, W. Zhang, Y. Cai, E.D. Kennelley, A fern that hyperaccumulates arsenic, Nature, 409 (2001) 579. [128] S.A. El-Fatah, M. Goto, A. Kodama, T. Hirose, Supercritical fluid extraction of hazardous metals from CCA wood, The Journal of supercritical fluids, 28 (2004) 21-27. [129] F.N. Robertson, Arsenic in ground-water under oxidizing conditions, south-west United States, Environmental Geochemistry and Health, 11 (1989) 171-185. [130] T.S. Choong, T. Chuah, Y. Robiah, F.G. Koay, I. Azni, Arsenic toxicity, health hazards and removal techniques from water: an overview, Desalination, 217 (2007) 139-166. [131] N.E. Korte, Q. Fernando, A review of arsenic (III) in groundwater, Critical Reviews in Environmental Control, 21 (1991) 1-39. [132] W.-J. Liu, L. Ling, Y.-Y. Wang, H. He, Y.-R. He, H.-Q. Yu, H. Jiang, One-pot high yield synthesis of Ag nanoparticle-embedded biochar hybrid materials from waste biomass for catalytic Cr (VI) reduction, Environmental Science: Nano, 3 (2016) 745-753. [133] R. Bencheikh-Latmani, A. Obraztsova, M.R. Mackey, M.H. Ellisman, B.M. Tebo, Toxicity of Cr(III) to Shewanella sp. Strain MR-4 during Cr(VI) Reduction, Environmental Science & Technology, 41 (2007) 214-220. [134] N.-H. Hsu, S.-L. Wang, Y.-C. Lin, G.D. Sheng, J.-F. Lee, Reduction of Cr(VI) by CropResidue-Derived Black Carbon, Environmental Science & Technology, 43 (2009) 8801-8806. [135] K. Lock, C. Janssen, Ecotoxicity of chromium (III) to Eisenia fetida, Enchytraeus albidus, and Folsomia candida, Ecotoxicology and Environmental Safety, 51 (2002) 203-205. [136] T. Norseth, The carcinogenicity of chromium, Environmental health perspectives, 40 (1981) 121-130. [137] A.U. Rajapaksha, M. Vithanage, Y.S. Ok, C. Oze, Cr(VI) Formation Related to Cr(III)Muscovite and Birnessite Interactions in Ultramafic Environments, Environmental Science & Technology, 47 (2013) 9722-9729. [138] I. Aharchaou, J.S. Py, S. Cambier, J.L. Loizeau, G. Cornelis, P. Rousselle, E. Battaglia, D.A. Vignati, Chromium hazard and risk assessment: New insights from a detailed speciation study in a standard test medium, Environmental toxicology and chemistry, 37 (2018) 983-992. [139] S.L. Thompson, F.C.R. Manning, S.M. McColl, Comparison of the Toxicity of Chromium III and Chromium VI to Cyanobacteria, Bulletin of Environmental Contamination and Toxicology, 69 (2002) 286-293. [140] D.A.L. Vignati, J. Dominik, M.L. Beye, M. Pettine, B.J.D. Ferrari, Chromium(VI) is more toxic than chromium(III) to freshwater algae: A paradigm to revise?, Ecotoxicology and Environmental Safety, 73 (2010) 743-749. [141] E. Lira-Silva, I.S. Ramírez-Lima, V. Olín-Sandoval, J.D. García-García, R. GarcíaContreras, R. Moreno-Sánchez, R. Jasso-Chávez, Removal, accumulation and resistance to chromium in heterotrophic Euglena gracilis, Journal of Hazardous Materials, 193 (2011) 216224. [142] J. Kováčik, P. Babula, J. Hedbavny, O. Kryštofová, I. Provaznik, Physiology and methodology of chromium toxicity using alga Scenedesmus quadricauda as model object,

Jo

ur

na

lP

re

-p

ro of

Chemosphere, 120 (2015) 23-30. [143] M. Dazy, E. Béraud, S. Cotelle, E. Meux, J.-F. Masfaraud, J.-F. Férard, Antioxidant enzyme activities as affected by trivalent and hexavalent chromium species in Fontinalis antipyretica Hedw, Chemosphere, 73 (2008) 281-290. [144] B. Ponti, How reliable are data for the ecotoxicity of trivalent chromium to Daphnia magna?, Environmental toxicology and chemistry, v. 33 (2014) pp. 2280-2287-2014 v.2233 no.2210. [145] D. Bull, The chemistry of chromated copper arsenate II. Preservative-wood interactions, Wood Science and Technology, 34 (2001) 459-466. [146] J.G. Ostmeyer, T.J. Elder, J.E. Winandy, Spectroscopic Analysis of Southern Pine Treated with Chromated Copper Arsenate. II. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT), Journal of Wood Chemistry and Technology, 9 (1989) 105-122. [147] S. Lebow, Alternatives to chromated copper arsenate (CCA) for residential construction, in: Proceedings of Environmental Impacts of Preservative-Treated Wood, February 8-11, 2004, Orlando, Florida, USA: Pre-conference Proceedings. Gainesville, Fla: Florida Center for Environmental Solutions, 2004. 1 CD-Rom. 12 pages., 2004. [148] M.H. Freeman, C.R. McIntyre, Copper-based wood preservatives, Forest products journal, 58 (2008) 7. [149] M. Mench, C. Bes, Assessment of Ecotoxicity of Topsoils from a Wood Treatment Site*1 *1Project supported by the French Agency for Environment and Energy (ADEME), Department of Polluted Soils and Sites, Angers, France (No. ADEME 05 72 C0018/INRA 22000033), Pedosphere, 19 (2009) 143-155. [150] N. Bolan, A. Kunhikrishnan, R. Thangarajan, J. Kumpiene, J. Park, T. Makino, M.B. Kirkham, K. Scheckel, Remediation of heavy metal(loid)s contaminated soils – To mobilize or to immobilize?, Journal of Hazardous Materials, 266 (2014) 141-166. [151] K. Ravet, M. Pilon, Copper and Iron Homeostasis in Plants: The Challenges of Oxidative Stress, Antioxidants & Redox Signaling, 19 (2013) 919-932. [152] A. Cuypers, J. Vangronsveld, H. Clijsters, Biphasic effect of copper on the ascorbateglutathione pathway in primary leaves of Phaseolus vulgaris seedlings during the early stages of metal assimilation, Physiologia Plantarum, 110 (2000) 512-517. [153] C.M. Bes, R. Jaunatre, M. Mench, Seed bank of Cu-contaminated topsoils at a wood preservation site: impacts of copper and compost on seed germination, Environmental Monitoring and Assessment, 185 (2013) 2039-2053. [154] A. Kolbas, P. Kidd, J. Guinberteau, R. Jaunatre, R. Herzig, M. Mench, Endophytic bacteria take the challenge to improve Cu phytoextraction by sunflower, Environmental Science and Pollution Research, 22 (2015) 5370-5382. [155] E. Hego, C.M. Bes, F. Bedon, P.M. Palagi, P. Chaumeil, A. Barré, S. Claverol, J.-W. Dupuy, M. Bonneu, C. Lalanne, C. Plomion, M. Mench, Differential accumulation of soluble proteins in roots of metallicolous and nonmetallicolous populations of Agrostis capillaris L. exposed to Cu, PROTEOMICS, 14 (2014) 1746-1758. [156] A. Lagomarsino, M. Mench, R. Marabottini, A. Pignataro, S. Grego, G. Renella, S.R. Stazi, Copper distribution and hydrolase activities in a contaminated soil amended with dolomitic limestone and compost, Ecotoxicology and Environmental Safety, 74 (2011) 20132019. [157] H. Qiu, M.G. Vijver, E. He, W.J.G.M. Peijnenburg, Predicting Copper Toxicity to Different Earthworm Species Using a Multicomponent Freundlich Model, Environmental Science & Technology, 47 (2013) 4796-4803. [158] K.A. Mackie, S. Marhan, F. Ditterich, H.P. Schmidt, E. Kandeler, The effects of biochar and compost amendments on copper immobilization and soil microorganisms in a temperate

Jo

ur

na

lP

re

-p

ro of

vineyard, Agriculture, Ecosystems & Environment, 201 (2015) 58-69. [159] N. Oustriere, L. Marchand, W. Galland, L. Gabbon, N. Lottier, M. Motelica, M. Mench, Influence of biochars, compost and iron grit, alone and in combination, on copper solubility and phytotoxicity in a Cu-contaminated soil from a wood preservation site, Science of the Total Environment, 566 (2016) 816-825. [160] C.M. Bes, M. Mench, M. Aulen, H. Gaste, J. Taberly, Spatial variation of plant communities and shoot Cu concentrations of plant species at a timber treatment site, Plant and Soil, 330 (2010) 267-280. [161] N. Hattab, M. Motelica-Heino, X. Bourrat, M. Mench, Mobility and phytoavailability of Cu, Cr, Zn, and As in a contaminated soil at a wood preservation site after 4 years of aided phytostabilization, Environmental Science and Pollution Research, 21 (2014) 10307-10319. [162] N. Thaler, M. Humar, Copper Leaching from Copper-ethanolamine Treated Wood: Comparison of Field Test Studies and Laboratory Standard Procedures, 2014, 9 (2014) 14. [163] X. Zhang, H. Wang, L. He, K. Lu, A. Sarmah, J. Li, N.S. Bolan, J. Pei, H. Huang, Using biochar for remediation of soils contaminated with heavy metals and organic pollutants, Environmental Science and Pollution Research, 20 (2013) 8472-8483. [164] J.H. Park, G.K. Choppala, N.S. Bolan, J.W. Chung, T. Chuasavathi, Biochar reduces the bioavailability and phytotoxicity of heavy metals, Plant and Soil, 348 (2011) 439. [165] F. Luo, J. Song, W. Xia, M. Dong, M. Chen, P. Soudek, Characterization of contaminants and evaluation of the suitability for land application of maize and sludge biochars, Environmental Science and Pollution Research, 21 (2014) 8707-8717. [166] M. Uchimiya, I.M. Lima, K.T. Klasson, L.H. Wartelle, Contaminant immobilization and nutrient release by biochar soil amendment: Roles of natural organic matter, Chemosphere, 80 (2010) 935-940. [167] M. Uchimiya, I.M. Lima, K. Thomas Klasson, S. Chang, L.H. Wartelle, J.E. Rodgers, Immobilization of Heavy Metal Ions (CuII, CdII, NiII, and PbII) by Broiler Litter-Derived Biochars in Water and Soil, Journal of Agricultural and Food Chemistry, 58 (2010) 5538-5544. [168] T. Townsend, T. Tolaymat, H. Solo-Gabriele, B. Dubey, K. Stook, L. Wadanambi, Leaching of CCA-treated wood: implications for waste disposal, Journal of Hazardous Materials, 114 (2004) 75-91. [169] K. Stook, T. Tolaymat, M. Ward, B. Dubey, T. Townsend, H. Solo-Gabriele, G. Bitton, Relative Leaching and Aquatic Toxicity of Pressure-Treated Wood Products Using Batch Leaching Tests, Environmental Science & Technology, 39 (2005) 155-163. [170] B. Dubey, T. Townsend, H. Solo-Gabriele, Metal loss from treated wood products in contact with municipal solid waste landfill leachate, Journal of Hazardous Materials, 175 (2010) 558-568. [171] L. Coudert, J.-F. Blais, G. Mercier, P. Cooper, P. Morris, L. Gastonguay, A. Janin, F. Zaviska, Optimization of copper removal from ACQ-, CA-, and MCQ-treated wood using an experimental design methodology, Journal of Environmental Engineering, 139 (2012) 576-587. [172] A. Temiz, U.C. Yildiz, T. Nilsson, Comparison of copper emission rates from wood treated with different preservatives to the environment, Building and Environment, 41 (2006) 910-914. [173] D.N. Obanda, T.F. Shupe, H.M. Barnes, Reducing leaching of boron-based wood preservatives – A review of research, Bioresource Technology, 99 (2008) 7312-7322. [174] C.A. Clausen, S.N. Kartal, R.A. Arango, F. Green, The role of particle size of particulate nano-zinc oxide wood preservatives on termite mortality and leach resistance, Nanoscale Research Letters, 6 (2011) 427. [175] A. Aertsen, C.W. Michiels, Stress and How Bacteria Cope with Death and Survival, Critical Reviews in Microbiology, 30 (2004) 263-273.

Jo

ur

na

lP

re

-p

ro of

[176] S.N. Kartal, F. Green, C.A. Clausen, Do the unique properties of nanometals affect leachability or efficacy against fungi and termites?, International Biodeterioration & Biodegradation, 63 (2009) 490-495. [177] S.J. Zheng, Crop production on acidic soils: overcoming aluminium toxicity and phosphorus deficiency, Annals of Botany, 106 (2010) 183-184. [178] H. Pan, C.-Y. Hse, R. Gambrell, T.F. Shupe, Fractionation of heavy metals in liquefied chromated copper arsenate 9-treated wood sludge using a modified BCR-sequential extraction procedure, Chemosphere, 77 (2009) 201-206. [179] C.A. Clausen, Improving the two-step remediation process for CCA-treated wood: Part II. Evaluating bacterial nutrient sources, Waste Management, 24 (2004) 407-411. [180] N. Zhao, Z. Yin, F. Liu, M. Zhang, Y. Lv, Z. Hao, G. Pan, J. Zhang, Environmentally persistent free radicals mediated removal of Cr(VI) from highly saline water by corn straw biochars, Bioresource Technology, 260 (2018) 294-301. [181] D. Zhong, Y. Zhang, L. Wang, J. Chen, Y. Jiang, D.C.W. Tsang, Z. Zhao, S. Ren, Z. Liu, J.C. Crittenden, Mechanistic insights into adsorption and reduction of hexavalent chromium from water using magnetic biochar composite: Key roles of Fe3O4 and persistent free radicals, Environmental Pollution, 243 (2018) 1302-1309. [182] F.K.M. Kazi, P.A. Cooper, Method to recover and reuse chromated copper arsenate wood preservative from spent treated wood, Waste Management, 26 (2006) 182-188. [183] H. Wang, Z. He, Z. Lu, J. Zhou, J.D. Van Nostrand, X. Xu, Z. Zhang, Genetic Linkage of Soil Carbon Pools and Microbial Functions in Subtropical Freshwater Wetlands in Response to Experimental Warming, Applied and Environmental Microbiology, 78 (2012) 7652. [184] H. Wang, X. Yuan, Y. Wu, H. Huang, X. Peng, G. Zeng, H. Zhong, J. Liang, M. Ren, Graphene-based materials: Fabrication, characterization and application for the decontamination of wastewater and wastegas and hydrogen storage/generation, Advances in Colloid and Interface Science, 195-196 (2013) 19-40. [185] L. Tang, G.-D. Yang, G.-M. Zeng, Y. Cai, S.-S. Li, Y.-Y. Zhou, Y. Pang, Y.-Y. Liu, Y. Zhang, B. Luna, Synergistic effect of iron doped ordered mesoporous carbon on adsorptioncoupled reduction of hexavalent chromium and the relative mechanism study, Chemical Engineering Journal, 239 (2014) 114-122. [186] Y. Dai, N. Zhang, C. Xing, Q. Cui, Q. Sun, The adsorption, regeneration and engineering applications of biochar for removal organic pollutants: A review, Chemosphere, (2019). [187] X. He, M. Elkouz, M. Inyang, E. Dickenson, E.C. Wert, Ozone regeneration of granular activated carbon for trihalomethane control, Journal of Hazardous Materials, 326 (2017) 101109. [188] K. Qiao, W. Tian, J. Bai, J. Dong, J. Zhao, X. Gong, S. Liu, Preparation of biochar from Enteromorpha prolifera and its use for the removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous solution, Ecotoxicology and Environmental Safety, 149 (2018) 80-87. [189] Y. Lin, N.G. Smart, C.M. Wai, Supercritical fluid extraction and chromatography of metal chelates and organometallic compounds, TrAC Trends in Analytical Chemistry, 14 (1995) 123133. [190] S. Nami Kartal, Removal of copper, chromium, and arsenic from CCA-C treated wood by EDTA extraction, Waste Management, 23 (2003) 537-546. [191] S.N. Kartal, C. Kose, Remediation of CCA-C treated wood using chelating agents, Holz als Roh- und Werkstoff, 61 (2003) 382-387. [192] E.D. Gezer, U. Yildiz, S. Yildiz, E. Di˙zman, A. Temiz, Removal copper, chromium and arsenic from CCA-treated yellow pine by oleic acid, Building and Environment, 41 (2006) 380-385. [193] R. Sierra-Alvarez, Removal of copper, chromium and arsenic from preservative-treated

Jo

ur

na

lP

re

-p

ro of

wood by chemical extraction-fungal bioleaching, Waste Management, 29 (2009) 1885-1891. [194] A. Janin, L. Coudert, P. Riche, G. Mercier, P. Cooper, J.-F. Blais, Application of a CCAtreated wood waste decontamination process to other copper-based preservative-treated wood after disposal, Journal of Hazardous Materials, 186 (2011) 1880-1887. [195] M. Yadav, Q. Xu, Catalytic chromium reduction using formic acid and metal nanoparticles immobilized in a metal–organic framework, Chemical Communications, 49 (2013) 3327-3329. [196] M.A. Omole, I.O. K’Owino, O.A. Sadik, Palladium nanoparticles for catalytic reduction of Cr(VI) using formic acid, Applied Catalysis B: Environmental, 76 (2007) 158-167. [197] L.-L. Wei, R. Gu, J.-M. Lee, Highly efficient reduction of hexavalent chromium on amino-functionalized palladium nanowires, Applied Catalysis B: Environmental, 176-177 (2015) 325-330. [198] M. Celebi, M. Yurderi, A. Bulut, M. Kaya, M. Zahmakiran, Palladium nanoparticles supported on amine-functionalized SiO2 for the catalytic hexavalent chromium reduction, Applied Catalysis B: Environmental, 180 (2016) 53-64. [199] J. Beiyuan, J.-S. Li, D.C.W. Tsang, L. Wang, C.S. Poon, X.-D. Li, S. Fendorf, Fate of arsenic before and after chemical-enhanced washing of an arsenic-containing soil in Hong Kong, Science of The Total Environment, 599-600 (2017) 679-688. [200] E.J. Kim, E.-K. Jeon, K. Baek, Role of reducing agent in extraction of arsenic and heavy metals from soils by use of EDTA, Chemosphere, 152 (2016) 274-283. [201] J. Beiyuan, A.Y. Lau, D.C. Tsang, W. Zhang, C.-M. Kao, K. Baek, Y.S. Ok, X.-D. Li, Chelant-enhanced washing of CCA-contaminated soil: coupled with selective dissolution or soil stabilization, Science of the total environment, 612 (2018) 1463-1472. [202] P.R. Kumar, S. Chaudhari, K.C. Khilar, S. Mahajan, Removal of arsenic from water by electrocoagulation, Chemosphere, 55 (2004) 1245-1252. [203] J. Farrell, J. Wang, P. O'Day, M. Conklin, Electrochemical and Spectroscopic Study of Arsenate Removal from Water Using Zero-Valent Iron Media, Environmental Science & Technology, 35 (2001) 2026-2032. [204] M.V.B. Krishna, K. Chandrasekaran, D. Karunasagar, J. Arunachalam, A combined treatment approach using Fenton’s reagent and zero valent iron for the removal of arsenic from drinking water, Journal of Hazardous Materials, 84 (2001) 229-240. [205] C. Su, R.W. Puls, Arsenate and Arsenite Removal by Zerovalent Iron:  Kinetics, Redox Transformation, and Implications for in Situ Groundwater Remediation, Environmental Science & Technology, 35 (2001) 1487-1492. [206] P.R. Buchireddy, R.M. Bricka, D.B. Gent, Electrokinetic remediation of wood preservative contaminated soil containing copper, chromium, and arsenic, Journal of hazardous materials, 162 (2009) 490-497. [207] J.A. Hingston, C.D. Collins, R.J. Murphy, J.N. Lester, Leaching of chromated copper arsenate wood preservatives: a review, Environmental Pollution, 111 (2001) 53-66. [208] S. Gul, J.K. Whalen, B.W. Thomas, V. Sachdeva, H. Deng, Physico-chemical properties and microbial responses in biochar-amended soils: Mechanisms and future directions, Agriculture, Ecosystems & Environment, 206 (2015) 46-59. [209] F.R. Oliveira, A.K. Patel, D.P. Jaisi, S. Adhikari, H. Lu, S.K. Khanal, Environmental application of biochar: Current status and perspectives, Bioresource Technology, 246 (2017) 110-122. [210] K.A. Spokas, W.C. Koskinen, J.M. Baker, D.C. Reicosky, Impacts of woodchip biochar additions on greenhouse gas production and sorption/degradation of two herbicides in a Minnesota soil, Chemosphere, 77 (2009) 574-581.