Synthesis of activated carbon from lignocellulosic biomass and its applications in air pollution control—a review

Journal of Environmental Chemical Engineering 1 (2013) 658–666

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Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece

Review

Synthesis of activated carbon from lignocellulosic biomass and its applications in air pollution control—a review Norhusna Mohamad Nor, Lau Lee Chung, Lee Keat Teong, Abdul Rahman Mohamed * School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia

A R T I C L E I N F O

A B S T R A C T

Article history: Received 27 March 2013 Accepted 19 September 2013

This review compiles the work done by various researchers on synthesis of activated carbon from lignocellulosic biomass and its applications in air pollution control. The general methods for preparation of lignocellulosic activated carbon as adsorption materials are discussed. The effect of carbonization and activation parameters such as temperature, heating rate, gas flow rate, activating agent, and residence time toward properties of activated carbon were reviewed. These parameters were related to the utilization of lignocellulosic activated carbon in air pollution control: removal of SO2, removal of NO2, simultaneous removal of SO2 and NOx, removal of H2S, and removal of VOC. Under appropriate activation conditions, it is possible to obtain activated carbon with surface area and pore volume as high as 3000 m2/g and 1.5 cm3/g, respectively, which could be considered as a good sorbent. Converting lignocellulosic biomass into activated carbon could solve environmental problems such as agricultural waste and air pollutions control. ß 2013 Elsevier Ltd. All rights reserved.

Keywords: Activated carbon Adsorption Lignocellulosic biomass Air pollution

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preparation of activated carbon from lignocellulosic biomass. . Carbonization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of activated carbon from lignocellulosic biomass . Removal of SO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Removal of NO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simultaneous removal of SO2 and NOx . . . . . . . . . . . . . . Removal of H2S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Removal of VOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Future of lignocellulosic activated carbons. . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Introduction Utilization of lignocellulosic biomass to produce activated carbon is an important approach in air pollution control strategy. Lignocellulosic biomass can be considered as abundant agricultural wastes. Converting these wastes into value added product such as activated carbon could solve environmental problems such as

* Corresponding author. Tel.: +60 45996410; fax: +60 45941013. E-mail address: [email protected] (A.R. Mohamed). 2213-3437/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jece.2013.09.017

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658 659 659 660 660 660 661 662 663 664 664 665 665 665

accumulation of agricultural waste, air pollution and water pollution. In addition, using activated carbon from lignocellulosic biomass instead of fossil sources such as coal will reduce global warming’s effects. Therefore, the circulation of carbon between atmosphere and pollutant removal process is merely a carbonneutral cycle. Apart from being effective in pollutant removal, lignocellulosic activated carbon is relatively economical, because it is sourced from agricultural sector wastes and is abundantly available. Lignocellulosic biomass derived from agricultural by-products has proven to be a promising type of raw material for producing

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activated carbon, especially due to its availability at a low price. A number of studies on numerous applications of lignocellulosic materials as activated carbon sorbents have been published by various researchers [1–3]. Lignocellulosic biomass generally can be classified into three different components, which are cellulose, hemicellulose, and lignin. Among the three, lignin has been identified as the main component in lignocellulosic biomass responsible for the adsorption process [2]. Lignin based biomass is the most abundant renewable carbon resource on earth after cellulose, with a worldwide production of 40–50 million tons per year [2]. Due to the rich carbon content of lignin, lignocellulosic biomass is a good option to be used as precursor for producing activated carbon [4,5]. Activated carbon with high adsorption capacity can be produced from numerous sources of lignocellulosic biomass, such as durian shell [6–9], coconut shell [10,11], rubberseed shell [12], hazelnut shell [13–15], palm kernel shell [16–27], almond shell [28,29], plum stones [30], cotton stalks [31], rice husk [32,33], pistachio-nut shell [34,35], walnut shell [36], and wood [37]. Activated carbon derived from lignocellulosic biomass is widely used for pollutant removal. Various industrial sectors use lignocellulosic activated carbon in operations such as chemical processes, petroleum refining, wastewater treatment, air pollution treatment and volatile organic compounds (VOC) adsorption [1–5,38]. In addition, activated carbon provides an effective mean for gas phase applications, such as for separation, deodorization, purification, storage and catalysis [39]. Activated carbon is a well-known adsorbent due to its unique and versatile properties that allow the accessible of gas/liquid into internal pore surface and high degree of surface reactivity [40]. The important properties of activated carbon are that it is comprised of high surface area, developed microporous structure and favorable pore size. The performance of activated carbon can be highly improved under appropriate condition. The first step in producing activated carbon is producing char from biomass with a carbonization/ pyrolysis process [3]. Throughout the process, moisture and volatile compounds are removed from the biomass [3]. From this char, activated carbon can be produced using three different processes: physical activation, chemical activation and physiochemical activation. Physical activation involves gas activating agents such as steam and CO2, and chemical activation involves the presence of chemical agents such as metal oxide, alkaline metal and acid [41]. The activation process leads to the production of activated carbon with high porosity, large surface area, and high pore volume. The present study is focused on the synthesis of activated carbon from lignocellulosic biomass and its applications in air pollution control. The study can be divided into two sections. In the first section, preparations of activated carbon from lignocellulosic biomass based from various methods are reviewed in details. The second section reports on the application of activated carbon from

659

lignocellulosic biomass in air pollution control. The effectiveness of activated carbon in gas adsorption activity is compared among different preparation approaches. Properties of the produced activated carbon such as surface area, and micropore volume are discussed and related to preparation conditions from the reported literature. Preparation of activated carbon from lignocellulosic biomass Generally, two main steps are involved in preparation of activated carbon from lignocellulosic biomass. The method is started with carbonization of lignocellulosic biomass at temperature lower than 800 8C in the absence of oxygen [1,12,18,21,39]. The process is then followed by activation process for the development of surface area and pore volume of activated carbon. Activation process can be divided into two different methods, which are physical activation and chemical activation. Carbonization Carbonization process is a phase to enrich carbon content in carbonaceous material by eliminating non-carbon species using thermal decomposition. Initial porosity of char even though still comparatively low, it could be developed in this stage before undergoes further development in activation process. Careful selection of carbonization parameters is important because this process leaves a significant effect on the final product [17]. In this process, the carbonization temperature has the most significant effect, followed by heating rate, nitrogen flow rate, and finally residence time [3,21]. Normally, higher carbonization temperatures (600–700 8C) result in reduced yield of char while increasingthe liquid and gases release rate [3]. Higher temperature will also increaseash and fixed carbon content and lower amount of volatile matter [3,21,31]. Thus, high temperatures result in better quality char but also decrease yield. This is due to the primary decomposition of biomass at higher temperatures and also secondary decomposition of char residue [3]. Thus, as the temperature of primary degradation increased or the residence times of primary vapors inside the cracked particle is shorter, the char yields decrease [31]. According to Ioannidoue and Zabaniotou [3], higher carbonization temperatures also increase ash and fixed carbon content due to the decrease in volatile matter. As a result, a higher temperature yields char with improved quality. In order to obtain low volatilization and a high char yield, low heating rates (10–15 8C/min) should be used. Char has a high fixed carbon content which is important for producing activated carbon. Lower heating rate will increase dehydration and improve the stabilization of the polymeric components [2,3]. However, the microporosity of char has been found to be independent of the precursor composition and the carbonization heating rate [2]. Table 1 presents the proximate and ultimate analysis of several lignocellulosic biomass materials.

Table 1 Ultimate and proximate analysis of lignocellulosic biomass used for air pollution control. Biomass type

Cotton stalks Corn stalks Corn cobs Rice straw Durian shell Palm shell Almond shell Plum stones

Ultimate analysis (db, % w/w)

Proximate analysis (db, % w/w)

Refs.

C

H

O

N

S

Ash

Volatile

Fixed carbon

Moisture

41.2 45.5 46.3 41.8 60.3 50.1 51.4 46.4

5.0 6.2 5.6 4.6 8.5 6.9 6.1 5.5

34.0 41.1 42.2 36.6 28.1 41.2 41.6 48.0

2.6 0.9 0.6 0.7 3.1 1.9 0.3 0.1

0.0 0.13 0.0 0.1 0.1 0.6 –

13.3 6.4 5.3 13.4 2.5 1.1 1.3 0.4

– – – 69.3 69.6 72.5 82.3 80.6

– – – – 22.4 18.7 – –

6.0 0 7.1 25.0 5.5 8.0 – –

[3] [3] [3] [3] [7] [17] [28] [30]

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Table 2 Various activation conditions for preparation of lignocellulosic chars. Activation method

Biomass

Refs.

Physical

Durian peel-based, palm shell, almond shell, pistachio-nut shell Rubber-seed shell, palm shell, nut shell, coconut shell

CO2 Steam

[8,19,21,27,34,40] [12,17,23,25,44,45]

Chemical

Durian shell, pistachio nut shell, plum stones, coconut shell, palm shell Corn cob Coconut shell Coconut shell Wood

KOH ZnCl2 Strong base Cu(NO3)2 H3PO4

[6,20,30,34,46] [39] [47] [48] [37]

Physiochemical

Palm shell Walnut shell Palm shell Almond shell Coconut shell Coconut shell

NaOH/CO2 KOH/CO2 Ce/CO2 CaO/Steam CuO/Steam Metal nitrate/steam

[24] [49] [50,51] [52] [53] [54]

Carbonization parameters give high contribution in the development of initial pore structure in the char, mainly through the release of volatile compounds from the carbon’s matrix. Since pore development in the char has a great influence on the pore characteristics of subsequently produced activated carbon, carbonization parameters should be taken into account prior to activation process.

chemical activation possesses larger surface area and well controlled microporosity in smaller ranges [50,51,56]. Furthermore, the carbon yield of chemical activation is also higher than that of physical activation [41].

Activation

Atmospheric pollutant emissions continue to deteriorate air quality. In fact, air pollution has emerged as one of the major problems caused by rapid development in industrial activities and substantial population growth. Therefore, in order to achieve a sustainable development for future, air pollution control is a crucial step. Currently, scrubbing gaseous pollutants using the adsorption method is widely applied [36–71]. Nevertheless, technological development using adsorption processes is also gaining considerable attention. Adsorption using adsorbents such as activated carbon has been studied [36–71]. Due to the fact that activated carbon provides a suitable pore size for gas adsorption and large surface area for rapid reaction, utilization of activated carbon offers great potential in air pollution control [36–71]. Most gaseous pollutants have a molecular size in the micropore region, i.e. <2 nm [30]. Therefore, activated carbon appears as a suitable adsorbent for gaseous reaction. There are various sources of air pollutants, including flue gas, biogas, natural gas, power plants, fossil fuel combustion, and transportation [46,47,54,60,61]. In order to overcome this problem, activated carbons from various lignocellulosic sources have been widely studied. Instead of successfully diminishing air pollutants by employing activated carbon via adsorption technology, the usefulness of lignocellulosic materials may become recognized and broadly applied. In addition, lignocellulosic activated carbons, mainly from biomass sources, could also be developed and utilized. A summary of gaseous pollutants removal by various lignocellulosic activated carbon such as SO2, NOx, H2S, volatile organic compounds (VOCs) and CO2is presented in Table 3.

The objective of activation process is to enhance the pore volume, enlarge the diameter of pores and increase the porosity of activated carbon. Activation process can be performed by three different methods. They are named physical activation, chemical activation and physiochemical activation (a combination of physical and chemical activation). Physical activation usually uses steam or CO2 while for chemical activation; various chemicals are used [42,43]. Table 2 presents various activation conditions for preparation of activated carbon from lignocellulosic precursors. During the first phase of activation process, unorganized carbon is removed, exposing the lignin to the action of activating agents and lead to the development of microporous structure [2]. In the latter phase of the reaction, existing pores are widened or largesize pores are formed when walls between the pores are completely burnt-off. This results in the increasing transitional pores and macroporosity, whereas the volume of micropores decreases. Thus, the extent of burn-off carbon material or the degree of activation is an important measure in activated carbon production [55]. During activation the temperature is set between 800 and 1000 8C to develop the porosity and surface area of lignocellulosic carbon [42,43]. For physical activation, steam is more effective than CO2, because activated carbon with a relatively higher surface area can be produced. The smaller molecule size of water is responsible to facilitate diffusion within the char’s porous structure effectively [1,25]. Steam activation is reported to be two or three times faster than CO2at the same degree of conversion [36,49]. On the other hand, various chemicals such as ZnCl2, H3PO4, NaOH and KOH have been used for chemical activation [13,30,36,56,57]. These chemical agents develop the porosity based on dehydration and degradation. Generally, chemical activation (300–500 8C) takes place at lower temperature than physical activation [13,56,57]. This improves the development of pore in carbon structure due to the effect of chemical agent [41]. One of the most important advantages of chemical activation over physical activation is the lower treatment temperature and shorter treatment time. In addition, the activated carbon obtained by the

Applications of activated carbon from lignocellulosic biomass

Removal of SO2 SO2 is one of the main precursors for acid rain generation, which is one of the most serious global environment concerns. Basically, application of activated carbon in SO2adsorption offers several advantages compared to the earlier methods [53]. SO2 removal from coal and oil combustion exhaust using activated carbon has been studied [26,37,52,53,58,63,64,72]. Most of this research was done using the impregnated chemicals method, which mostly uses metal oxides in activated carbon synthesis. SO2 removal can occur through physical adsorption and chemical adsorption. Table 4

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Table 3 Preparation method and adsorption capacity of various activated carbons from lignocellulosic biomass. Raw material

Preparation method

Adsorption capacity

Refs.

Coconut Coconut Coconut Coconut Coconut Coconut Coconut Coconut

10% KOH impregnation Strong base impregnation 0.05–0.20 M Cu impregnation Steam activation (800 8C) + 3–10% Cu impregnation Steam activation (800 8C) + 3% metal (Fe, Co, Ni and Cu) impregnation Steam activation (800 8C) + 3% copper impregnation 2% KI impregnation 1–5% Acids (HNO3, H2SO4, HCl, CH3COOH) and 1–5% bases (KOH, NAOH) impregnation

40 mg/g SO2 and 22 mg/g NOx 215.4 mg/g H2S 87.3 mg/g H2S 116 mg/g SO2 Toluene, NO 24 mg/g SO2 64 mg/g H2S Aromatics (benzene, toluene, o-xylene, m-xylene, p-xylene) and alcohols (methanol, ethanol, isopropanol) o-Xylene (305.7 mg/g) 73.7 mg/g SO2 53 mg/g H2S 46, 76, 68 mg/g H2S 165 min SO2 and 115 min NOx 121.7 mg/g SO2, 3.7 mg/g NO 64 mg/g SO2 67 mg/g NO2 120 mg/g SO2 283, 215, 143 mg/g NO2 58.1, 66.3 mg/g NO2 3.65 mg/g H2S 89.6 mg/g SO2 0.255 cm3/g H2S 3.98 mol/kg CO2 0.77 mol/kg CO2 7.3 mol/kg CO2 11.7, 9.6 wt% CO2 capture 11 mmol/g CO2 160 mg/g CO2

[46] [47] [48] [53] [54] [58] [59] [60]

shell shell shell shell shell shell shell shell

Coconut shell Palm shell Palm shell Palm shell Palm shell Palm shell Almond shell Plum stone Wood Wood Walnut shell Peach and apricot stone Pistachio nut shell Red pine wood Peat Peat Wood Almond shell Bamboo chip African palm stone

10 M HNO3, 9 M H2SO4, 7.3 M H3PO4, 10 M NaOH, 6.6 M NH3 impregnation CO2 activation (700–1100 8C) Steam activation CO2 (900 8C), 40% H2SO4, 30% KOH activation CO2 activation (700–1100 8C) + 10% metal impregnation CO2 activation (700–1100 8C) + 5–12% Ce impregnation Steam activation (800 8C) + 2.1–12.2% Ca impregnation KOH activation (800 8C) H3PO4 activation + calcium impregnation 2.3% Na, 10% Ce, or 10% La impregnation CO2/KOH activation (500–800 8C) Steam activation (850 8C) CO2, NaOH activation CO2 activation (800 8C) Steam activation Steam activation H3PO4 activation + amine impregnation CO2, ammonia activation 80% H3PO4 activation 24–48% H3PO4 activation

summarizes characteristics of activated carbon used for removal of SO2. Macias-Perez et al. [37] reported a detailed study on SO2 removal activity using calcium oxide loaded activated carbon prepared from wood and almond shell. In their investigation, various calcium precursors such as Ca(OH)2, CaCO3, CaO, Ca(CH3COO)2 and Ca(C2H5COO)2 and preparation methods including physical mixing, incipient wetness impregnation, rotary evaporator impregnation, complex formation and ionic exchange were used. Their research revealed that high calcium loading and dispersion are important factors to achieve high SO2 removal activity. Activated carbon sample with 3–20 wt% Ca loading must be prepared via the impregnation method in order to obtain a high surface area and a proper analysis of calcium loading on SO2 retention. They further reported on the effect of Ca loading toward activated carbon properties [52]. Higher surface oxygen content was found to improve calcium loading and dispersion and SO2 uptakes up to 123 mg SO2/g was achieved at high calcium loading and dispersion. SO2 removal conditions were also studied in subsequent report for retention and regeneration [77]. According to the study, thermal regeneration of the spent sorbents could be carried out under inert atmosphere at 880 8C with only 20% activity loss for the first regeneration cycle. The activity loss was mainly due to the sintering and formation of CaS. Apart from calcium oxide, copper oxide is a popular chemical used to impregnate with activated carbon. One of lignocellulosic material used was coconut shell that has been impregnated using copper oxide via steam activation [53,58]. The optimum surface area of CuO/AC obtained was 1054 m2/g at 3 wt% of copper oxide [53]. In the study, it was observed that the original activated carbon had high surface area and well developed porosity compared to copper oxide impregnated sample [53]. This was due to the pore blockage caused by copper oxide particles after calcinations at 450 8C. However, CuO/AC was found to have increased SO2 adsorption capacity of 116 mg SO2/g, with copper particles acting as active sites for the oxidation of SO2. Surface

[61] [26] [20] [20] [50] [51] [52] [30] [37] [62] [36] [63] [63,64] [65] [66] [67] [68] [69] [70] [71]

functional groups enhance SO2 removal activity but activated carbon support does not participate in the reaction. SO2 is catalytically oxidized to SO3 and subsequently forms a sulphate with impregnated copper. In this study, spent activated carbon was successfully regenerated by thermal treatment. Coconut shell activated carbon impregnated with copper and cerium oxides were also employed by Wey et al. [72]. High SO2 removal activity was achieved but catalyst deactivation occurred if chloride and Pb were present in the pollutant gas stream. Apart from experimental analysis, a theoretical study of SO2 removal activity by lignocellulosic based materials was also performed by Yang and Lua [34,35,63,64]. Activated carbon was prepared from pistachio shell by physical activation using CO2 and steam at 900 8C, followed bychemical activation, by using NaOH [34,35]. A model was developed in Lua and Yang’s report by incorporating non-equilibrium, non-isothermal and non-adiabatic effects for a single gas adsorbate on a fixed-bed system; the model was solved by finite-difference method [63]. Some other studies were performed to analyze the effect of certain parameters such as the concentration of gas inlets, flow rate, and temperature. These parameters were analyzed and the data were fitted with developed model by Lua and Yang [63]. In another model of adsorption kinetics, micropore, macropore, surface diffusion and nonlinear isotherm at the micropore mouth were incorporated and solved throughthe finite difference method [64]. The model fitwell with experimental results and an adsorption capacity of 89.6 mg SO2/g was achieved. Removal of NO2 Lignocellulosic biomass derived activated carbon has also been used for removing and minimizing the emission of NO2 gas [30,36,62,74]. Application of activated carbon for adsorption of NO2 is driven by its developed pore structure [62]. In addition, surface chemistry represented by the type, number and chemical arrangement of heteroatoms on their surface is also considered to

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Table 4 Physical and chemical activation conditions and characteristics of activated carbon for removal of SO2. Raw material

Activation condition

Palm shell Pistachio nut shell

CO2, 700–1100 8C Steam, 900 8C KOH activation CO2, 800 8C H3PO4 activation Ca impregnation Steam, 800 8C Ca, 2.1–12.2 wt% Steam, 800 8C Cu, 3–10 wt% Steam, 800 8C Cu, 3 wt% CO2 NaOH activation

Pistachio nut shell Wood Almond shell Coconut shell Coconut shell Pistachio nut shell

Inlet concentration (ppm)

SBET (m2/g)

Vmic (cm3/g)

Vt (cm3/g)

– 0.322

0.76 –

2000 2000

984 796

2000 3000

1064 1708

0.21 –

– –

3000

1234

0.36

0.90

–

1077

0.1003

–

200–800

1054

0.092

–

1064

0.16

Sorption capacity (mg/g) 73.7 92

Refs. [26] [34]

94 120

[35] [37]

64

[52]

116

[53]

0.517

24

[58]

0.51

89.6

[63,64]

SBET = total surface area; Vmic = micropore volume; Vt = total pore volume.

be important [36,62]. Kante et al. [62] studied adsorption of NO2 using wood-based activated carbon impregnated with chemicals such as sodium, cerium and lanthanum chlorides. Overall, introducing these chemicals onto the activated carbon surfaceresulted in higher adsorption capacity for NO2. The adsorption capacity of sodium chloride (283 mg NO2/g) was the highest and lanthanum chloride (143 mg NO2/g) showed the lowest adsorption. Impregnation resulted in a significant decrease in the structural arrangement via the addition of nonporous materials. The chlorides were deposited in the pores and decreased the pore volume. In this case, addition of sodium chloride reduced the BET surface area and total pore volume from 2143 to 1952 m2/g and 1.494 to 1.372 cm3/g, respectively [62]. In another study carried out by Nowicki et al. [36], NO2 removal was examined using activated carbon prepared from walnut shell. The produced activated carbon had high surface area of 2305 m2/g and pore volume of 1.15 cm3/g [36]. Comparison of various activation methods revealed that chemical activation with KOH contribute to microporosity development more than physical activation with CO2. Using walnut shell activated carbon in dry condition, NO2adsorption capacity of 66 mg NO2/g was achieved. The data proved the differences in the effectiveness of activation by KOH and CO2, illustrating the influence of the activation method. The adsorption capacities of KOH and CO2 activation are 66.3 mg NO2/g and 58.1 mg NO2/g respectively. The heating rate is lower, so a longer time is needed to increase the temperature. Using this method, well developed porous structure of activated carbon can be achieved. The activated carbon prepared at high temperature (800 8C) had a five time greater surface area and larger total pore volume compared to the sample prepared at lower temperature (400 8C). The optimum data showed that 97–98% of total pore volume was micropores [36]. In subsequent research, Nowicki et al. [30] employed chemical activation using KOH to prepare activated carbon from plum stone. Highly microporous activated carbon with a surface area of

3228 m2/g and pore volume of 1.61 cm3/g was obtained. A NO2 adsorption study revealed the adsorption capacity of 67 mg NO2/g when the experiment was conducted under dry conditions [30]. Dry adsorption process was found to have a better adsorption capacity because the reaction mechanism is significantly changed in the presence of water. This study showed that the micropores of activated carbon produced under optimum condition contributed to up to 96% of total pore volume. Preparation conditions and characteristics of activated carbon for removal of NO2 are summarized in Table 5. Simultaneous removal of SO2 and NOx Currently, simultaneous removal of SO2 and NOx has gained significant attention in research field. It is desirable to remove SO2 and NOx simultaneously in a single unit, leading to lower capital cost for equipment and cutting operating costs. Besides activated carbon [73,82–87], various types of ash [77–81] have been used for simultaneous removal of SO2 and NOx. However, activated carbon application is more favorable because of lower prices and better sorption ability [77–81]. Researchers reported that impregnation of metal oxides into activated carbon is effective for simultaneously removing SO2 and NOx [26,27,50,51,56]. Lee et al. [46] reported the simultaneous removal of SO2 and NOx using coconut shell based activated carbon prepared by KOH impregnation. In the study, KOH impregnation was found to be an important factor for increasing the simultaneous adsorption of SO2 and NOx. SO2 molecules were found to have higher affinity toward active sites compared to NOx molecules, to form sulphates (SO42 ) and sulphites (SO32 ) [46]. Sumathi et al. also extensively studied the simultaneous removal of SO2 and NO using palm shell based activated carbon prepared under different conditions [26,27,50,51,6]. Preparation of microporous activated carbon from palm shell was successfully demonstrated by the group of research. Carbonization at 1100 8C

Table 5 The preparation conditions and characteristics of activated carbon for removal of NO2. Raw material

Activation condition

Inlet concentration (ppm)

SBET (m2/g)

Vmic (cm3/g)

Vt (cm3/g)

Sorption capacity (mg/g)

Refs.

Plum stones Walnut shell Wood Wood Wood Wood

KOH activation (800 8C) CO2/KOH activation (500–800 8C) 2.3% Na, 10% Ce, or 10% La impregnation 5.0 wt% Ag impregnation 5.0 wt% Cu impregnation Dimethylamine impregnation

1000 1000 1000 1000 1000 1000

3228 2305 1952 1772 1930 836

1.57 1.12 0.746 0.11 0.707 0.347

1.61 1.15 1.372 1.09 1.42 0.519

67 58.1/66.3 283/215/143 – – 49

[30] [36] [62] [74] [75] [76]

SBET = total surface area; Vmic = micropore volume; Vt = total pore volume.

N. Mohamad Nor et al. / Journal of Environmental Chemical Engineering 1 (2013) 658–666

under 500 mL/min N2 followed by physical activation using 500 mL/min CO2 at the same temperature for 90 min was determined to be optimum preparation condition. Under this condition activated carbon with high surface area of 1052.9 m2/g was produced. In another study, they incorporated several metals into the structure of activated carbon by wet impregnation method [50]. For this screening work, 4 h of calcination at 400 8C under argon as inert gas was required to obtain the high surface area of metal impregnated activated carbons. From the screening study, cerium was found to be the best metal to be impregnated with activated carbon because it achieved high SO2 and NO removal with surface area and pore volume of 997 m2/g and 0.362 cm3/g, respectively. A detailed study on the activity of cerium impregnated palm shell based activated carbon was subsequently published [51]. Cerium was found to have a synergistic effect on simultaneous SO2 and NO removal. It was concluded that cerium does not take part directly in SO2 removal but acts as an active site to catalytically promote NO adsorption. Sumathi et al. performed a study on effect of humidity, which showed that increasing humidity could enhance SO2 removal; nevertheless, this will also reduce the removal of NO [56]. Higher temperature (up to 250 8C) was found to increase NO removal but SO2 removal started to reduce beyond 150 8C. Adsorption capacity of 121.7 mg/g and 3.7 mg/g was reported for SO2 and NO removal respectively, using cerium impregnated palm shell based activated carbon. Removal of H2S Hydrogen sulfide (H2S) is a colorless gas with an offensive odor. Its toxicity and odor has created a lot of environmental issues. Besides, this harmful gas could also causes serious health problems. In industry, even a low concentration of H2S (1 ppm) has a detrimental effect on a catalyst [47]. H2S can be detected by most people at threshold of 0.0047 ppm [20,47]. Various methods can be used to remove or eliminate H2S emissions from different sources [59,88,89]. However, the most successful and widespread method is application of activated carbon. Lignocellulosic activated carbons used for H2S adsorption are derived from various sources such as red pine wood [65], palm shell [20], peach and apricot stone [90] and coconut shell [59,47,48]. Generally, activated carbon used for H2S adsorption is modified with caustic chemicals such as KOH and NaOH [20] or oxidative agents such as KI and KMnO4 [59], to promote oxidation of H2S to elemental sulphur. Characteristics of activated carbon for removal of H2S are presented in Table 6. Elsayed et al. [47] reported the removal of H2S at high (3000 ppm) and low (10 ppm) concentrations from the air using coconut shell based activated carbon. Their study revealed that H2S adsorption capacity of coconut shell based activated carbon impregnated with strong base and oxidant was strongly affected by the amount of basic groups on the carbon surface. Moisture in the gas stream was found to greatly enhance the H2S adsorption activity, because water is involved in the dissociation of H2S; even a very small quantity can significantly increase the amount of H2S

663

adsorbed. Adsorption capacity of coconut shell activated carbon impregnated with strong base was reported to be lower at low H2S concentration with surface area of 91.1 m2/g compared to higher H2S concentration with surface area of 215.4 m2/g [47]. The amount of H2S adsorbed at both concentrations showed a clear dependence on the amount of basic groups present on the surface. The presence of strong base on the carbon surface increased H2S adsorption capacity even at dry conditions. In this study, sulfur compounds adsorbed on the carbon surface were identified as elemental sulfur, sulfur oxides, carbon sulfide, polysulfides and hydrogen sulfide [47]. In the investigation conducted by Huang et al. [48], coconut shell derived activated carbon was impregnated with copper nitrate by wet impregnation method. The inlet concentration of H2S was set at 3000 ppm. Adsorption capacity of activated carbon was found to increase by tenfold upon copper impregnation, from 0.127 mmol H2S/g to 1.364 mmol H2S/g. In this study, surface area for virgin coconut shell activated carbon was 1050 m2/g, whereas the surface area of the impregnated activated carbon decreased to 789 m2/g. The results suggested that partial pores blockage due to the copper species deposition. It was also revealed that the copper species deposited not only onto the mesopores but also onto the micropores. Huang et al. also found that moisture significantly increases H2S adsorption activity [48]. Their analysis showed that copper species in the form of Cu(OH)2 appeared as important active sites by reacting with H2S and catalyzing a substitution reaction. The adsorption capacity of H2S in the impregnated activated carbon increased with an increase in the amount of Cu species loaded onto activated carbon. The best adsorption performance of coconut shell based activated carbon with impregnation condition of pH 3 and 0.2 M was 10 times larger than that of the virgin coconut shell-based activated carbon. H2S adsorption technology has been applied at a pig farm, as illustrated in the work carried out by Pipatmanomai et al. [59]. Their work showed the potential of applying coconut shell activated carbon in removing H2S from biogas with a 2400 ppm H2S concentration. This may enhance the utilization of the cleaned biogas, mainly methane, in gas enginesfor renewable energy. To boost up the adsorption capacity of H2S, 2 wt% of KI was impregnated onto coconut shell activated carbon. The impregnation of KI enhanced the removal efficiency approaching 100%, with H2S adsorption capacity as high as 64 mg/g in biogas stream with 2400 ppm of H2S. Guo et al. [20] studied the preparation of palm shell based activated carbon using thermal and chemical activation. Dynamic adsorption in a fixed bed configuration showed that the palm shell activated carbons prepared by chemical activation (KOH or H2SO4 impregnation) performed better than those prepared by thermal activation and coconut shell based commercial activated carbon. The adsorption capacity of H2S obtained by KOH and H2SO4 impregnation were 68 and 76 mg H2S/g, respectively, with a comparable surface area and pore volume. An activity study at room temperature was carried out and showed that H2S adsorption can take place through physisorption, chemisorptions and H2S oxidation.

Table 6 The characteristics of activated carbon for removal of H2S. Raw material

Activation condition

Inlet concentration (ppm)

SBET (m2/g)

Vmic (cm3/g)

Vt (cm3/g)

Sorption capacity (mg/g)

Refs.

Palm shell

2000 10–3000

1148 1014 931

0.25 0.28 0.378

– – 0.401

68 76 215.4

[20]

Coconut shell

KOH, 30 wt% H2SO4, 40 wt% Strong base impregnation

Coconut shell Coconut shell Peach and apricot stone

Cu, 0.05–0.2 M KI, 2 wt% Steam, 850 8C

270 2400 –

789 700 1150

– – –

– – 0.44

87.3 64 57

[48] [59] [90]

SBET = total surface area; Vmic = micropore volume; Vt = total pore volume.

[47]

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664

Table 7 The preparation conditions and characteristics of activated carbon for removal of VOC. Raw material

Activation condition

Inlet concentration (ppm)

SBET (m2/g)

Vmic (cm3/g)

Vt (cm3/g)

Sorption capacity (mmol/g)

Refs.

Coconut shell

Steam, 850 8C

2400

2278

0.82

1.13

[45]

Coconut shell

1–5 wt% acids (HNO3, H2SO4, HCl, CH3COOH) 1–5 wt% bases (KOH, NaOH)

10,000–15,000

719

–

–

Coconut shell

10 M HNO3 9 M H2SO4 7.3 M H3PO4 10 M NaOH 6.6 M NH3 Steam, 800 8C 3 wt% metal (Fe, Co, Ni, Cu)

–

868

0.176

–

DCM: 2.69 TEM: 6.89 Benzene: 6.41 Toluene: 4.05 o-Xylene: 4.92 m-Xylene: 4.11 p-Xylene: 5.19 MeOH: 5.65 EtOH: 2.18 i-propanol: 1.92 MEK: 4.02 o-Xylene: 305.70

[61]

150

972

-

-

-

[54]

Coconut shell

[60]

SBET = total surface area; Vmic = micropore volume; Vt = total pore volume.

Removal of VOC Volatile organic compounds (VOCs) are recognized as a source of air pollutants; they include most solvents such as thinner, degreasers, cleaners, lubricants, and liquid fuels [60]. Removal of VOCs by lignocellulosic activated carbon has been studied by various researchers [46,54,60,61,91]. Some modifications and impregnation using selected chemicals onto activated carbon are required to increase the adsorption capacity and improve the selectivity of trapped organic compound. The preparation conditions and characteristics of activated carbon used in removal of VOC are tabulated in Table 7. Cosnier et al. [45] demonstrated dichloromethane and trichloroethylene (chlorinated VOCs) adsorption on coconut shell derived activate carbon. The activated carbon was prepared at 850 8C by steam activation. The performance of the prepared activated carbon was compared with two different types of rayon based carbon fibers that were treated physically using CO2 and chemically using H3PO4. Their study showed that coconut shell activated carbon prepared by steam activation resulted in high adsorption capacity of VOCs and well developed high surface area, 2278 m2/g and pore volume, 1.13 cm3/g [45]. Their study emphasized the effect of moisture on the adsorption of VOCs on activated carbon. The inlet concentration for VOCs has been set up to 2400 ppm, with adsorption capacity of DCM is 2.69 mmol/g and TEM is 6.89 mmol/g respectively. It was assumed that if moisture is pre-adsorbed on activated carbon, VOCs replaces the water molecule and the adsorption capacity remains unchanged; otherwise, competition between water and chlorinated VOCs will occur and reduce adsorption capacity. Due to the competition between the adsorption of water and VOCs, the moisture in the gaseous mixture to be treated tended to modify the adsorption capacities and kinetics. This is because, the higher interaction between water – AC, the stronger the effect of the presence of water on the adsorption of the chlorinated VOCs. Kim et al. [60] studied the performance of acid and base impregnated coconut shell activated carbons in VOC adsorption. Various VOCs such as benzene, toluene, o-, m-, p-xylene, methanol, ethanol, i-propanol, and methyl ethyl ketone (MEK) were adsorbed on the prepared activated carbon. The VOCs adsorption characteristics and chemical properties of the activated carbons were

studied in detail. In their results, 1 wt% phosphoric acid impregnated activated carbon with surface area 719 m2/g showed a high adsorption capacity for VOCs [60]. A high degree of porosity was not observed on the surface of alkali impregnated activated carbon which was attributed to the pore blocking caused by surface deposition of alkali, thereby decreasing the BET surface area from 89 to 719 m2/g. They also concluded that impregnated activated carbon was effective for VOC removal through adsorption process with the potential for repeated use through simple heat treatment for desorption. Li et al. [61] employed coconut shell activated carbon to adsorb o-xylene. Their investigation revealed that alkali impregnated activated carbon had higher adsorption capacity than acid impregnated activated carbon. This was due to the higher surface area (868 m2/g) and pore volume (0.176 cm3/g), and reduction of oxygen containing functional groups. From all chemical agents used for chemical activation, 6.6 M ammonia impregnated activated carbon was reported to have high adsorption capacity of 305.70 mg o-xylene/g [61]. Coconut shells impregnated by transition metals such as Fe, Co, Ni, and Cu were used for simultaneous removal of toluene and NO [54]. NO is not a VOC in itself but it contributes in the reaction of toluene oxidation with O2. Referring to Lu and Wey, 3 wt% of Co impregnated activated carbon at 200 8C activation temperature, with the low presence of O2, gave highest adsorption capacity of toluene [54]. Nevertheless, when the polyol process was applied in preparing the similar activated carbon, Cu impregnated activated carbon was found to have the highest adsorption capacity [54]. Future of lignocellulosic activated carbons A number of studies have been carried out for the synthesis of activated carbon from various lignocellulosic biomasses. However, there are still many types of lignocellulosic biomass from different geographical areas which have not been converted into activated carbons. In fact, air pollutant removal studies with lignocellulosic activated carbon have not been applied widely in the industry. The potential of lignocellulosic activated carbon can be developed more using various types of chemicals or catalyst via impregnation. This is due to different types of chemicals or catalysts give different effects on adsorption of various types of polluted gases.Referring to the above review, chemical impregnation gives greater sorption

N. Mohamad Nor et al. / Journal of Environmental Chemical Engineering 1 (2013) 658–666

capacity of gases if the functional group of the chemical is suitable for certain gas adsorption. Further detailed studies should be concentrated on removing current major air pollutants such as VOCs, nitric oxides and various gases from flue gas. In addition, feasibility of CO2 separation and adsorption using activated carbon should also be studied as global warming has gaining greater attention from the world. Research of CO2 adsorption using lignocellulosic activated carbon may be successful if the suitable chemicals have been found and impregnated into lignocellulosic activated carbon. Conclusion Development of lignocellulosic activated carbon would enhance the conversion of waste into usable products. The production of lignocellulosic activated carbon has been studied for decades. This supports the theoretical study that lignocellulosic materials are suitable precursors for the production of activated carbons with very high surface area and pore volume comparable to the best commercial activated carbon. Successful application of lignocellulosic activated carbon in air pollution control depends strongly on the adsorption capacity of activated carbon. For that, activated carbon needs to undergo modification through either controlling the conditions of activation or by post-activation surface treatments. Acknowledgements The authors gratefully acknowledge Knowledge Transfer Program [grant code I-gt/24(USM-11)], FELDA Palm Industries Bhd., Universiti Sains Malaysia (RU-PRGS) and MyBrain 15 Program for their financial supports. References [1] B. Cagnon, P. Xavier, A. Guillot, F. Stoeckli, G. Chambat, Contributions of hemicellulose, cellulose and lignin to the mass and the porous properties of chars and steam activated carbons from various lignocellulosic precursors, Bioresource Technology 100 (2009) 292–298. [2] P.J.M. Suhas, M.M.L. Carrott, R. Carrott, Lignin – from natural adsorbent to activated carbon: a review, Bioresource Technology 98 (2007) 2301–2312. [3] O. Ioannidou, A. Zabaniotou, Agricultural residues as precursors for activated carbon production – a review, Renewable and Sustainable Energy Reviews 11 (2007) 1966–2005. [4] A. Demirbas, Adsorption of lead and cadmium ions in aqueous solutions onto modified lignin from alkali glycerol delignication, Journal of Hazardous Material 109 (2004) 221–226. [5] S.J. Allen, B. Koumanova, Z. Kircheva, S. Nenkova, Adsorption of 2-nitrophenol by technical hydrolysis lignin: kinetics, mass transfer, and equilibrium studies, Industrial Engineering Chemical Resources 44 (2005) 2281–2287. [6] T.C. Chandra, M.M. Mirna, Y. Sudaryanto, S. Ismadji, Adsorption of basic dye onto activated carbon prepared from durian shell: studies of adsorption equilibrium and kinetics, Chemical Engineering Journal 127 (2007) 121–129. [7] T.C. Chandra, M.M. Mirna, Y. Sudaryanto, S. Ismadji, Activated carbon from durian shell: preparation and characterization, Journal of the Taiwan Institute of Chemical Engineers 40 (2009) 457–462. [8] K. Nuithitikul, S. Srikhun, S. Hirunpraditkoon, Influences of pyrolysis condition and acid treatment on properties of durian peel-based activated carbon, Bioresource Technology 101 (2010) 426–429. [9] Y.J. Tham, P.A. Latif, A.M. Abdullah, A. Shamala-Devi, Y.H. Taufiq-Yap, Performances of toluene removal by activated carbon derived from durian shell, Bioresource Technology 9 (2010), In Press, Corrected Proof. [10] W. Li, K. Yang, J. Peng, L. Zhang, S. Guo, H. Xia, Effects of carbonization temperatures on characteristics of porosity in coconut shell chars and activated carbons derived from carbonized coconut shell chars, Industrial Crops and Products 28 (2008) 190–198. [11] W. Li, J. Peng, L. Zhang, K. Yang, H. Xia, S. Zhang, S.H. Guo, Preparation of activated carbon from coconut shell chars in pilot-scale microwave heating equipment at 60 kW, Waste Management 29 (2009) 756–760. [12] K. Sun, J.C. Jiang, Preparation and characterization of activated carbon from rubber-seed shell by physical activation with steam, Biomass and Bioenergy 34 (2010) 539–544. [13] E. Sayan, Ultrasound-assisted preparation of activated carbon from alkaline impregnated hazelnut shell: an optimization study on removal of Cu2+ from aqueous solution, Chemical Engineering Journal 115 (2006) 213–218.

665

[14] D.D. Milenkovic, P.V. Dasic, V.B. Veljkovic, Ultrasound-assisted adsorption of copper(II) ions on hazelnut shell activated carbon, Ultrasonics Sonochemistry 16 (2009) 557–563. [15] M. Kobya, Removal of Cr(VI) from aqueous solutions by adsorption onto hazelnut shell activated carbon: kinetic and equilibrium studies, Bioresource Technology 91 (2004) 317–321. [16] T. Vitidsant, T. Suravattanasakul, S. Damronglerd, Production of activated carbon from palm-oil shell by pyrolysis and steam activation in a fixed bed reactor, Science Asia 25 (1999) 211–222. [17] W.M.A.W. Daud, W.S.W. Ali, M.Z. Sulaiman, The effects of carbonization temperature on pore development in palm-shell-based activated carbon, Carbon 38 (2000) 1925–1932. [18] W.M.A.W. Daud, W.S.W. Ali, M.Z. Sulaiman, Effect of activation temperature on pore development in activated carbon produced from palm shell, Journal of Chemical Technology & Biotechnology 78 (2003) 1–5. [19] J. Guo, A.C. Lua, Experimental and kinetic studies on pore development during CO2 activation of oil palm shell char, Journal of Porous Materials 8 (2001) 149–157. [20] J. Guo, Y. Luo, A.C. Lua, R. Chi, Y. Chen, X. Bao, S. Xiang, Adsorption of hydrogen sulphide (H2S) by activated carbons derived from oil-palm shell, Carbon 45 (2007) 330–336. [21] A.C. Lua, F.Y. Lau, J. Guo, Influence of pyrolysis conditions on pore development of oil-palm-shell activated carbons, Journal of Analytical and Applied Pyrolysis 76 (2006) 96–102. [22] A.C. Lua, Q. Jia, Adsorption of phenol by oil-palm-shell activated carbons in a fixed bed, Chemical Engineering Journal 150 (2009) 455–461. [23] Q. Jia, A.C. Lua, Effects of pyrolysis conditions on the physical characteristics of oilpalm-shell activated carbons used in aqueous phase phenol adsorption, Journal of Analytical and Applied Pyrolysis 83 (2008) 175–179. [24] B.K. Hamad, A.M. Noor, A.R. Afida, M.N. Mohd Asri, High removal of 4-chloroguaiacol by high surface area of oil palm shell-activated carbon activated with NaOH from aqueous solution, Desalination 257 (2010) 1–7. [25] S. Mak, B. Tey, K. Cheah, W. Siew, K. Tan, The effect of mechanical grinding on the mesoporosity of steam-activated palm kernel shell activated carbons, Journal of Chemical Technology & Biotechnology 84 (2009) 1405–1411. [26] S. Sumathi, S. Bhatia, K.T. Lee, A.R. Mohamed, Optimization of microporous palm shell activated carbon production for flue gas desulphurization: experimental and statistical studies, Bioresource Technology 100 (2009) 1614–1621. [27] S. Sumathi, S. Bhatia, K.T. Lee, A.R. Mohamed, Performance of an activated carbon made from waste palm shell in simultaneous adsorption of SOx and NOx of flue gas at low temperature, Science in China, Series E: Technological Sciences 52 (2009) 198–203. [28] M.G. Plaza, C. Pevida, C.F. Martı´n, J. Fermoso, J.J. Pis, F. Rubiera, Developing almond shell-derived activated carbons as CO2 adsorbents, Separation and Purification Technology 71 (2010) 102–106. [29] A. Marcilla, S. Garcıa-Garcıa, M. Asensio, J.A. Conesa, Influence of thermal treatment regime on the density and reactivity of activated carbons from almond shells, Carbon 38 (2000) 429–440. [30] P. Nowicki, H. Wachowska, R. Pietrzak, Active carbons prepared by chemical activation of plum stones and their application in removal of NO2, Journal of Hazardous Materials 181 (2010) 1088–1094. [31] A.E. Putun, N. Ozbay, E.P. Onal, E. Putun, Fixed-bed pyrolysis of cotton stalk for liquid and solid products, Fuel Process Technology 86 (2005) 1207–1219. [32] I. Dahlan, K.T. Lee, A.H. Kamaruddin, A.R. Mohamed, Key factor in rice husk ash/ CaO sorbent for high flue gas desulfurization activity, Environmental Science & Technology 40 (2006) 6032–6037. [33] N. Yalcın, V. Sevinc, Studies of the surface area and porosity of activated carbons prepared from rice husks, Carbon 38 (2000) 1943–1945. [34] T. Yang, A.C. Lua, Characteristics of activated carbons prepared from pistachio-nut shells by potassium hydroxide activation, Microporous and Mesoporous Materials 63 (2003) 113–124. [35] T. Yang, A.C. Lua, Characteristics of activated carbons prepared from pistachio-nut shells by physical activation, Journal of Colloid and Interface Science 267 (2003) 408–417. [36] P. Nowicki, R. Pietrzak, H. Wachowska, Sorption properties of active carbons obtained from walnut shells by chemical and physical activation, Catalysis Today 150 (2010) 107–114. [37] M.C. Maci´as-Pe´rez, A. Bueno-Lo´pez, M.A. Lillo-Ro´denas, C. Salinas-Marti´nez de Lecea, A. Linares-Solano, SO2 retention on CaO/activated carbon sorbents. Part I: importance of calcium loading and dispersion, Fuel 86 (2007) 677–683. [38] M. Yates, J. Blanco, P. Avila, M.P. Martin, Honeycomb monoliths of activated carbons for effluent gas purification, Microporous and Mesoporous Material 37 (2000) 201–208. [39] W.T. Tsai, C.Y. Chang, S.L. Lee, A low cost adsorbent from agricultural waste corn cob by zinc chloride activation, Bioresource Technology 64 (1998) 211–217. [40] R.C. Bansal, J.B. Donnet, F.F. Stoeckli, Active Carbon, Marcel Dekker Inc., New York, 1988. [41] Y. Sudaryanto, S.B. Hartono, W. Irawaty, H. Hindarso, S. Ismadji, High surface area activated carbon prepared from cassava peel by chemical activation, Bioresource Technology 97 (2006) 734. [42] V.K. Gupta, P.J.M. Suhas, Application of low-cost adsorbents for dye removal – a review, Journal of Environmental Management 90 (2009) 2313–2342. [43] G. Crini, Non-conventional low-cost adsorbents for dye removal: a review, Bioresource Technology 97 (2006) 1061–1085. [44] O.N. Baklanova, G.V. Plaksin, V.A. Drozdov, V.K. Duplyakin, N.V. Chesnokov, B.N. Kuznetsov, Preparation of microporous sorbents from cedar nutshells and hydrolytic lignin, Carbon 42 (2003) 1793–1800.

666

N. Mohamad Nor et al. / Journal of Environmental Chemical Engineering 1 (2013) 658–666

[45] F. Cosnier, A. Celzard, G. Furdin, D. Be´gin, J.F. Mareˆche´, Influence of water on the dynamic adsoprtion of chlorinated VOCs on active carbon: Relative humidity of the gas phase versus pre-adsorbed water, Adsorption Science and Technology 24 (2006) 215–228. [46] Y.W. Lee, H.J. Kim, J.W. Park, B.U. Choi, D.K. Choi, Adsorption and reaction behavior for the simultaneous adsorption of NO–NO2 and SO2 on activated carbon impregnated with KOH, Carbon 41 (2003) 1881–1888. [47] Y. Elsayed, M. Seredych, A. Dallas, T.J. Bandosz, Desulfurization of air at high and low H2S concentrations, Chemical Engineering Journal 155 (2009) 594–602. [48] C.C. Huang, C.H. Chen, S.M. Chiu, Effect of moisture on H2S adsorption by copper impregnated activated carbon, Journal of Hazardous Materials 136 (2006) 866–873. [49] M.G. Plaza, F. Rubiera, J.J. Pis, C. Pevida, Ammoxidation of carbon materials for CO2 capture, Applied Surface Science 256 (2010) 6843–6849. [50] S. Sumathi, S. Bhatia, K.T. Lee, A.R. Mohamed, Selection of best impregnated palm shell activated carbon (PSAC) for simultaneous removal of SO2 and NOx, Journal of Hazardous Materials 176 (2010) 1093–1096. [51] S. Sumathi, S. Bhatia, K.T. Lee, A.R. Mohamed, SO2 and NO simultaneous removal from simulated flue gas over cerium-supported palm shell activated at lower temperatures-role of cerium on NO removal, Energy and Fuels 24 (2010) 427–431. [52] M.C. Maci´as-Pe´rez, A. Bueno-Lo´pez, M.A. Lillo-Ro´denas, C. Salinas-Marti´nez de Lecea, A. Linares-Solano, SO2 retention on CaO/activated carbon sorbents. Part II: effect of the activated carbon support, Fuel 87 (2008) 2544–2550. [53] H.H. Tseng, M.Y. Wey, C.H. Fu, Carbon materials as catalyst supports for SO2 oxidation: Catalytic activity of CuO-AC, Carbon 41 (2003) 139–149. [54] C.Y. Lu, M.Y. Wey, Simultaneous removal of VOC and NO by activated carbon impregnated with transition metal catalysts in combustion flue gas, Fuel Processing Technology 88 (2007) 557–567. [55] A.R. Reed, P.T. William, Thermal processing of biomass natural fiber wastes by pyrolysis, International Journal Energy Resources 28 (2003) 131–145. [56] S. Sumathi, S. Bhatia, K.T. Lee, A.R. Mohamed, Cerium impregnated palm shell activated carbon (Ce/PSAC) sorbent for simultaneous removal of SO2 and NOprocess study, Chemical Engineering Journal 162 (2010) 51–57. [57] N. Bhadusha, T. Ananthabaskaran, Adsorptive removal of methylene blue onto ZnCl2 activated carbon from wood apple outer shell: kinetics and equilibrium studies, E-Journal of Chemistry 8 (2011) 1696–1707. [58] H.H. Tseng, M.Y. Wey, Study of SO2 adsorption and thermal regeneration over activated carbon-supported copper oxide catalysts, Carbon 42 (2004) 2269–2278. [59] S. Pipatmanomai, S. Kaewluan, T. Vitidsant, Economic assessment of biogas-toelectricity generation system with H2S removal by activated carbon in small pig farm, Applied Energy 86 (2009) 669–674. [60] K.J. Kim, C.S. Kang, Y.J. You, M.C. Chung, M.W. Woo, W.I. Jeong, N.C. Park, H.G. Ahn, Adsorption–desorption characteristics of VOCs over impregnated activated carbons, Catalysis Today 111 (2006) 223–228. [61] L. Li, S. Liu, J. Liu, Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal, Journal of Hazardous Materials 192 (2011) 683–690. [62] K. Kante, E. Deliyanni, T.J. Bandosz, Interactions of NO2 with activated carbons modified with cerium, lanthanum and sodium chlorides, Journal of Hazardous Materials 165 (2009) 704–713. [63] A.C. Lua, T. Yang, Theoretical and experimental SO2 adsorption onto pistachionut-shell activated carbon for a fixed-bed column, Chemical Engineering Journal 155 (2009) 175–183. [64] A.C. Lua, T. Yang, Theoretical analysis and experimental study on SO2 adsorption onto pistachio-nut-shell activated carbon, AIChE Journal 55 (2009) 423–433. [65] K. Sakanishi, Z. Wu, A. Matsumura, I. Saito, T. Hanaoka, T. Minowa, M. Tada, T. Iwasaki, Simultaneous removal of H2S and COS using activated carbons and their supported catalysts, Catalysis Today 104 (2005) 94–100. [66] S. Garcı´a, M.V. Gil, C.F. Martı´n, J.J. Pis, F. Rubiera, C. Pevida, Breakthrough adsorption study of a commercial activated carbon for pre-combustion CO2 capture, Chemical Engineering Journal 171 (2011) 549–556. [67] M.G. Plaza, S. Garcı´a, F. Rubiera, J.J. Pis, C. Pevida, Post-combustion CO2 capture with a commercial activated carbon: comparison of different regeneration strategies, Chemical Engineering Journal 163 (2010) 41–47. [68] M.G. Plaza, S. Garcı´a, F. Rubiera, J.J. Pis, C. Pevida, Evaluation of ammonia modified and conventionally activated biomass based carbons as CO2 adsorbents in post combustion conditions, Separation and Purification Technology 80 (2011) 96–104.

[69] M.G. Plaza, S. Garcı´a, A. Arenillas, F. Rubiera, C. Pevida, J.J. Pis, CO2 capture by adsorption with nitrogen enriched carbons, Fuel 86 (2007) 2204–2212. [70] Y. Wang, Y. Zhou, C. Liu, L. Zhou, Comparative studies of CO2 and CH4 sorption on activated carbon in presence of water, Colloids and Surfaces A: Physicochemical and Engineering Aspects 322 (2008) 14–18. [71] D.P. Vargas, L. Giraldo, J. Silvestre-Albero, J.C. Moreno-Piraja´n, CO2 adsorption on binderless activated carbon monoliths, Adsorption 17 (2011) 497–504. [72] M.Y. Wey, C.H. Fu, H.H. Tseng, K.H. Chen, Catalytic oxidization of SO2 from incineration flue gas over bimetallic Cu–Ce catalysts supported on pre-oxidized activated carbon, Fuel 82 (2003) 2285–2290. [73] D. Lo´pez, F. Mondrago´n, R. Buitrago, Simultaneous Catalytic Adsorption of NO and SO2 on Activated Carbons at Low Temperatures, ACS National Meeting Book of Abstracts, 2008. [74] B. Svetlana, D. Deeona, J.B. Teresa, Effect of silver nanoparticles deposited on micro/mesoporous activated carbons on retention of NOx at room temperature, Journal of Colloid and Interface Science 354 (2011) 331–340. [75] L. Benoit, G.L. Eugene, A.R. Joseph, J.B. Teresa, Effect of reduction treatment on copper modified activated carbons on NOx adsorption at room temperature, Langmuir 27 (2011) 5354–5365. [76] D. Eleni, J.B. Teresa, Effect of carbon surface modification with dimethylamine on reactive adsorption of NOx, Langmuir 27 (2011) 1837–1843. [77] I. Dahlan, K.T. Lee, A.H. Kamaruddin, A.R. Mohamed, Selection of metal oxides in the preparation of rice husk ash (RHA)/CaO sorbent for simultaneous SO2 and NO removal, Journal of Hazardous Materials 166 (2009) 1556–1559. [78] C.H. Hung, Y.C. Yu, Simultaneous removal of SO2 and NO from flue gas via dry injection technology using fly ash promoted calcium hydroxide and inorganic additives, World Clean Air Congress 1 (1998). [79] L.C. Lau, K.T. Lee, A.R. Mohamed, Rice husk ash sorbent doped with copper for simultaneous removal of SO2 and NO: optimization study, Journal of Hazardous Materials 183 (2010) 738–745. [80] L.C. Lau, K.T. Lee, A.R. Mohamed, Simultaneous SO2 and NO removal using sorbents derived from rice husks: an optimization study, Fuel 90 (2011) 1811–1817. [81] T. Li, Y. Zhuo, J. Lei, X. Xu, Simultaneous removal of SO2 and NO by low cost sorbent-catalysts prepared by lime, fly ash and industrial waste materials, Korean Journal of Chemical Engineering 24 (2007) 1113–1117. [82] W.J. Zhang, A. Bagreev, F. Rasouli, Reaction of NO2 with activated carbon at ambient temperature, Industrial and Engineering Chemistry Research 47 (2008) 4358–4362. [83] D. Lo´pez, R. Buitrago, A. Sepu´lveda-Escribano, F.F. Rodrı´guez-Reinoso, Mondrago´n, Surface complexes formed during simultaneous catalytic adsorption of NO and SO2 on activated carbons at low temperatures, Journal of Physical Chemistry 111 (2007) 1417–1423. [84] Y.L. Wang, Z.Y. Liu, Effect of binder on simultaneous SO2 removal and NO conversion over activated carbon honeycomb supported V2O5 catalyst, Guocheng Gongcheng Xuebao/The Chinese Journal of Process Engineering 9 (2009) 701–706. [85] Y.L. Wang, L. Zhan, L.C. Ling, Z.Y. Liu, Effect of V2O5 loading on simultaneous SO2 and NO removal activities over an activated carbon honeycomb supported V2O5 catalysts, Huadong Ligong Daxue Xuebao/Journal of East China University of Science and Technology 32 (2006), 497-502+534. [86] Y.L. Wang, L. Zhan, L.C. Ling, Z.Y. Liu, Using NH3 for regeneration of an activated carbon honeycomb supported V2O5 catalyst for simultaneous SO2 and NO removal, Huadong Ligong Daxue Xuebao/Journal of East China University of Science and Technology 33 (2007), 297-300+305. [87] G. Yan-xia, Z. Liu, Y. Li, Q. Liu, NH3 regeneration of SO2-captured V2O5/AC catalystsorbent for simultaneous SO2 and NO removal, Ranliao Huaxue Xuebao/Journal of Fuel Chemistry and Technology 35 (2007) 344–348. [88] M.S. Horikawa, F. Rossi, M.L. Gimenes, C.M.M. Costa, M.J.C. Silva, Chemical absorption of H2S for biogas purification, Brazil Journal of Chemical Engineering 21 (2004) 415–422. [89] J.H. Tsai, F.T. Jeng, H.L. Chiang, Removal of H2S From Exhaust Gas by Use of Alkaline Activated Carbon, Kluwer Academic Publisher, 2001, pp. 357–366. [90] D.V. Brazhnyk, Y.P. Zaitsev, I.V. Bacherikova, V.A. Zazhigalov, J. Stoch, A. Kowal, Oxidation of H2S on activated carbon KAU and influence of the surface state, Applied Catalysis B: Environmental 70 (2007) 557–566. [91] C.Y. Lu, M.Y. Wey, L.I. Chen, Application of polyol process to prepare AC-supported nanocatalyst for VOC oxidation, Applied Catalysis A: General 325 (2007) 163–174.