Effect of varying deposition conditions of magnetite on sawdust on the physiochemical properties of the prepared composites

Journal Pre-proof Effect of varying deposition conditions of magnetite on sawdust on the physiochemical properties of the prepared composites Amjad H. El-Sheikh, Rawan M. Al-Salamin, Hiba S. Alshamaly, Dua’a M. Tahboub, Yahya S. Al-Degs, Ismail I. Fasfous, Nabil N. Al-Hashimi, Jafar I. Abdelghani

PII:

S2213-3437(19)30620-7

DOI:

https://doi.org/10.1016/j.jece.2019.103497

Reference:

JECE 103497

To appear in:

Journal of Environmental Chemical Engineering

Received Date:

4 September 2019

Revised Date:

14 October 2019

Accepted Date:

18 October 2019

Please cite this article as: El-Sheikh AH, Al-Salamin RM, Alshamaly HS, Tahboub DM, Al-Degs YS, Fasfous II, Al-Hashimi NN, Abdelghani JI, Effect of varying deposition conditions of magnetite on sawdust on the physiochemical properties of the prepared composites, Journal of Environmental Chemical Engineering (2019), doi: https://doi.org/10.1016/j.jece.2019.103497

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Effect of varying deposition conditions of magnetite on sawdust on the physiochemical properties of the prepared composites Amjad H. El-Sheikh*, a, Rawan M. Al-Salamina, Hiba S. Alshamalya, Dua’a M. Tahbouba, Yahya S. Al-Degsa, Ismail I. Fasfousa, b, Nabil N. Al-Hashimic, Jafar I. Abdelghania a:

Department of Chemistry, Faculty of Science, The Hashemite University, P.O. Box 150459,

Al-Zarqa (13115), Jordan. Tel: +962-5-3903333, Fax: + 962-5-382-6613. present address: College of Sciences and Health professions, King Saud bin Abdulaziz

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b:

University for Health Sciences, Jeddah, Saudi Arabia.

Faculty of pharmacy, The Hashemite University, P.O. Box 150459, Al-Zarqa (13115), Jordan.

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c:

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Tel: +962-5-3903333, Fax: + 962-5-382-6613.

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*: corresponding author, e-mail: [email protected] or [email protected]

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Graphical abstract

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Lead adsorption

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Mag-OW1 Mag-OW2

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Mag-OW3

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Mag-OW4 Mag-OW6

24 20

Mag-OW5

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Mag

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qe (mg g-1)

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OW

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8 4 0

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6

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0 8

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Mag-OW7

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Ce (mg L -1)

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Research highlights

Magnetite-wood composites were prepared and tested for Pb2+ removal

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PCA indicated surface area & Pb uptake were significant for samples grouping.

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Various deposition conditions gave various amounts of iron oxides & magnetite.

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Magnetite deposition raised thermal stability & SABET, decreased SAMB & Pb uptake.

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Lead uptake was the highest by the adsorbent prepared by longer stirring time

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Abstract

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This work reports a novel study for deposition of magnetite (Mag) on olive wood sawdust (OW) by the coprecipitation-hydrothermal method under dominating deposition factors including deposition temperature of magnetite by OW, agitation time, magnetite deposition in presence/absence of OW, magnetite/OW mass ratio, pyrolysis of final composites. The 2

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composites were characterized by IR, XRD, TGA, surface area (by N2 and methylene blue adsorption test) and lead uptake The effect of experimental factors on physicochemical properties were addressed. Principal component analysis (PCA) was found effective for understanding the differences among composites. It was found that magnetite deposition has relatively increased the stability of OW against degradation. XRD and IR data showed that not only various deposition conditions caused deposition of various amounts of iron oxides and

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magnetite on wood surface; but also the amount of deposited iron oxides exceeded that of

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magnetite. Pb ions adsorption was significantly affected by the deposition conditions in which deposition time was the most dominant among the tested factors as 5 hrs stirring (at 50ºC)

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achieved the best lead uptake. In general, deposition of magnetite by OW reduced porosity of

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composites. The prepared composites were effective for Pb removal with capacitates 22-49 mg gat pH 7.0. Not all physicochemical parameters were effective for composites grouping. Surface

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areas and Pb uptake were most responsive for experimental conditions.

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Key words: Magnetite; Olive wood sawdust; Magnetic wood; Physicochemical properties; coprecipitation-hydrothermal method; Principal component analysis.

Introduction

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1.

Adsorption is the most common method for water treatment [1-3]. Other treatment methods were also reported such as photocatalytic [4] and microwave methods [5]. Recently the use of magnetic adsorbents for adsorption and magnetic solid phase extraction (MSPE) of pollutants achieved a great interest [6-9]. . 3

Many authors reported the use of lignocellulosic material (such as olive wood sawdust and olive waste material) as biosorbents for uptake of toxic metals from water [10-13]. Wood can be modified to produce a new promissing material that can be used for special applications [14]. Indeed, magnetization of wood may alter its adsorption performance but will produce magnetic wood that can be easily isolated [15, 16]. Sawdust is a naturally occurring material that is usually thrown away and its disposal is hard. It

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also has many active functional groups capable of metals uptake [10-13]. The use of sawdust is

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of economic and environmental importance. The deposition of magnetite on sawdust surface will give the adsorbent magnetic properties and improve its separation after the adsorption process

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[15, 16]. It will also add more functional groups to the surface. Recently, adsorption via

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magnetic biosorbents has been reported as an effective method for heavy metals removal from water. For example, uptake of cadmium by sawdust modified with magnetic nanoparticle was

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reported by Shah et al. [17]. Liu, et al. [18] prepared magnetite cellulose-chitosan hydrogel microspheres sorbent which exhibited selective affinity towards Cu (II), Fe (II), and Pb (II) ions.

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Other works were also reported [6, 15, 16, 19-23] 233342 Several methods were reported in the literature for magnetite preparation. The best preparation method of magnetite is coprecipitaion-hydrothermal method. This method consists of ageing stoichiometric mixtures of ferrous and ferric hydroxides in aqueous media. Although

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coprecipitaion-hydrothermal method is well-known, however it is necessary to be optimized since deposition procedure may affect its properties. Some authors reported that bared magnetite (Mag) is hydrophobic, and thus it is unstable and tends to form aggregates [24]. So that magnetite can be deposited on appropriate material to increase its stability in the extraction medium and to give magnetic properties to the substrate [25, 26]. Optimization of the deposition 4

process of magnetite on lignocellulosic material is necessary to deposit the optimum amount of magnetite on it to get the optimum adsorption and magnetic properties. Mikhaylova et al. [27] reported that in the process of producing magnetite, maghemite (γ-Fe2O3) may be formed as a byproduct. So that the preparation procedure should be carefully conducted and optimized. Deposition of magnetite by wood particles is a multi-factor process that often conducted at

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different experimental factors including: mass ratio of ingredients, deposition time, reaction temperature, stirring time, and pyrolysis of adsorbent [15]. Accordingly, the physicochemical

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properties (such as surface area, thermal properties, adsorption of metals, etc.) are highly

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dependent on the initial preparation conditions. Generally, the classical univaraite analysis is often adopted to interrelate the physiochemical variables. However, principle component

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analysis (PCA) has found many applications in adsorption studies including samples clustering and process modeling [28]. Moreover, principle component analysis was adopted to find out the

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significance of experimental factors on pollutants removal [29, 30]. The principal goal of the current research, in fact, was to investigate the effect of various

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preparation conditions magnetite-olive wood composites and the potential influence on the final surface properties including Pb ions removal from water. The optimization of magnetite deposition on olive wood sawdust included temperature, time of stirring, magnetite preparation

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in the presence/absence of substrate, pyrolysis and mass ratio of magnetite/sawdust. The surfaces were characterized by Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), thermal gravimetric analysis (TGA), BET specific surface area by nitrogen gas adsorption (SABET) and relative surface area by methylene blue adsorption (SAMB) to figure out the consequences of varying preparation conditions on the textural properties of designed

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composites. Principal component analysis is applied to assess the overall influence of preparation conditions on the physiochemical chemical properties of fabricated composites.

Materials and methods

2.1.

Chemicals, reagents and materials

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Olive wood branches were collected from Al-Mafraq / Jordan. All chemicals were purchased

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from Sigma-Aldrich in analytical grade. Distilled water was used throughout this work. pH of the

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solutions was adjusted by using diluted hydrochloric acid or diluted sodium hydroxide solutions. Iron (II) chloride tetra hydrate and Iron (III) chloride hexahydrate were used for magnetite

Instruments and equipment

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2.2.

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preparation. Lead nitrate was employed in the adsorption studies.

Absorbance measurements of methylene blue were recorded using UV-Visible

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spectrophotometer (UV-1700 pharmaSpec, Shimadzu Corporation, Japan). pH meter (inoLab pH level 1, WTW GmbH & Co, Germany) was used for pH measurements. An isothermal water bath shaker (1083 GFL, Germany) was used in equilibrium adsorption experiments. An IKA mill (model MF 10B, Germany) was used for grinding the raw olive wood sorbents. Sonication of

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solutions was carried out using an ultrasonic water bath (soniclean, PTY, LTD, Australia). A furnace (BARNSTEAD/ Thermolyne, temperature range: room temperature-1200°C, Dubuque, IOWA) was used for heating the adsorbents under inert atmosphere. An atomic absorption spectrometer (Analyst Thermo ICE 3000) was used for the quantitative determination of metals under the following operational conditions: 75 mA, slit width 0.5 nm, burner height 7 mm, 6

acetylene flow 1 L min-1, air flow 10 L min-1, wavelength: 217.1 nm. ATR-FT-IR spectra for the adsorbents were measured using infrared spectrometer (vertex 70, Bruker Ltd, Massachusetts, USA). Powder X-ray diffraction was performed using X-ray diffractometer (Ultima IV, Rigaku, Japan). Elemental analysis was carried out using Eurovector model E.A.3000 instrument (Italy) using copper sample-tubes. Nitrogen adsorption at 77 K was conducted with a NOVA-2200 VER. 6.11 for the determination of BET surface area. Thermal gravimetric analysis was

Preparation of magnite-wood composites

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2.3.

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conducted by using NETZSCH STA 409 PC/PG with a heating rate of 10°C min-1.

As described earlier by El-Sheikh et al. [15], olive wood branches were passed through an

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electric sawing machine after removing the bark. The flakes were then dried at 80°C for 24 hours

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and then ground using a mill and then passed through 1 mm sieve. The obtained olive wood sawdust was washed with ethanol thirteen times and the obtained product was labeled as OW.

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Magnetic olive wood sorbents were prepared by using coprecipitation/ hydrothermal method as described earlier by El-Sheikh et al. [15]. The purpose of the present work was to design

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magnitude-wood composites under different experimental factors to investigate the influence of factors on the final physicochemical natures of magnetic olive wood sorbents. Following a univaraite optimization test toward Pb ions uptake, many composites were designed while changing the factors presented in Table 1. The best combinations of factors giving the highest

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Pb removal from solution are presented. Table 1 presents various experimental conditions involved in each adsorbent preparation. Typically: Iron (II) chloride tetra hydrate and Iron (III) chloride hexahydrate were added to a 100 mL distilled water previously bubbled with nitrogen. The desired mass of OW was then added to get the desired (magnetite : OW) mass ratio (1 : 3 or 1 : 7). The mixture was stirred for the desired time (30 min or 5 hrs) at the desired temperature 7

(25 or 50 or 80°C). Then, 5.0 mL ammonia solution (25%) was added either in the presence or absence of woody-substrate. Pyrolysis negatively affected Pb removal and only one composite (heated at 200°C) is provided. The magnetic adsorbents were separated using an external magnet and then washed repeatedly with distilled water and then dried in a drying oven overnight at 100°C. The products were labeled as described in Table 1. Magnetite (Mag) was prepared in a

Characterization of composites

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similar procedure (heating at 50ºC and stirring for 30 min) but without adding sawdust.

The adsorbents were characterized by the following techniques: Fourier transform infrared

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(ATR-FT-IR) spectrometry, powder x-ray diffraction (XRD), thermal gravimetric analysis (TGA) and elemental analysis. Nitrogen adsorption experiments were conducted at 77 K to

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measure the BET specific surface area (SABET). Methylene blue adsorption experiments were

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conducted as described earlier by El-Sheikh et al. [11, 13] to measure relative surface area (SAMB).

Adsorption behavior of Pb ions

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2.5.

Adsorption studies were conducted by adding 25 mg of the adsorbent to 25 mL solutions of various concentrations of lead and the pH was maintained at 7. The selected pH was based on preliminary studies. The solutions were shaken in an isothermal water bath shaker at 30°C for 3

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hours and the remaining concentrations of metals were analyzed by AAS. The adsorbed lead was calculated by the equation: qe = (Co-Ce).V/m where Co: initial concentration of the metal in the solution (mg L-1); Ce: equilibrium concentration of metal in the solution (mg L-1); qe: equilibrium concentration of metal on solid sorbent (mg g-1), V: volume of the solution (L), m: mass of the adsorbent (g). 8

Adsorption data were then modelled by Langmuir equation which can be written in the following linear form [31, 32]: Ce/qe = 1/(KL.Qmax) + (1/Qmax).Ce where Qmax (mg g-1) is the amount of adsorbate at complete monolayer coverage, and KL (L mg1

) is a Langmuir constant that is related to adsorption favority.

2.6.

Principal component analysis (PCA)

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Principal Component Analysis (PCA) is a powerful tool for the interpretation of large data

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tables. PCA is a data compression method based on the correlation among variables [29, 30]. It aims to group those correlated variables, while replacing the original ones by a new set, called

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the principal components (PCs), onto which the data are projected. These PCs are completely

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uncorrelated and are built as a simple linear combination of the original variables. It is important to point out here that the PCs contain most of the variability in the data set, albeit in a much

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lower dimensional space. The first principal component, PC1, is defined in the direction of maximum variance of the whole data set. PC2 is the direction that describes the maximum

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variance in the orthogonal subspace to PC1. The subsequent components are taken orthogonal to those previously chosen, and describe the maximum of the remaining variance. In this work, data matrix X (9×7) (i.e. 9 composites × 7 physiochemical parameters) is decomposed into two matrices, T (score matrix) and L (loading matrix) using suitable PCA algorithm. The first step in

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PCA is the computation of loadings. Mathematically, the loadings are the Eigen vectors of the matrix (XXT). There are several methods to estimate the Eigen vectors, such as singular value decomposition (SVD) and NIPALS (non-linear iterative partial least-squares) in the order of explained proportion of the variations in X, until a certain pre-established number of components. The loadings are grouped into a matrix L. The collected loadings are orthonormal, 9

meaning that they are both orthogonal and normalized. In fact, hierarchical clustering analysis HCA is often carried and it is often applied along with PCA for samples clustering. The main strategy of PCA and HCA are based on cluster analysis where the composites are aggregated stepwise according to similarity of their features or variables (i.e., physiochemical properties). As a result, hierarchically ordered clusters are created. In HCA, the collected data is displayed in a certain way to emphasize their natural clusters and patterns in a two dimensional space. The

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results are often presented in the form of a dendrogram which allow quick visualization of

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clusters and correlations among fabricated composites. Data acquisition and processing were conducted using Chemstation version B.04.01 software. The statistical analysis including

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principal component analysis PCA and hierarchical cluster analysis HCA Chemoface 1.61

Results and discussion

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3.

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software which work under Matlab® (Mathworks, 8.6, USA).

Preparation of magnetite-wood composites is rather a complex process which is highly

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dependent on certain operational factors including temperature, magnetite/wood ratio, stirring time, and final pyrolysis [15]. In the meantime, our research revealed that deposition of magnetite in the presence or absence of the substrate (olive wood in the current case) is rather a

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dominating factor. By adopting univaraite optimization tests toward Pb ions uptake, many magnetite-wood composites were prepared under different operational conditions. The best composite is the one favorably interacting with Pb ions. Moreover, correlation studies among factors will be necessary to detect the significant factor(s) toward certain application. Following coprecipitation-hydrothermal procedure, number of composites were designed and those exhibited high affinity toward Pb were provided in Table 1 along with experimental details. As 10

shown in Table 1, the best composite, outperformed other ones toward Pb ions, was used for comparison purposes (Mag-OW4). The effect of reaction temperature for deposition of magnetite on olive wood was investigated by heating the reaction mixture at various temperatures: 25, 50 and 80°C (samples Mag-OW1, Mag-OW2, Mag-OW3). The effect of stirring time of the deposition mixture was studied by stirring the reaction mixture for various times: 30 minutes (Mag-OW2) and 5 hours (Mag-OW4). The effect of Mag-to-OW ratio was

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investigated by designing two composites: Mag-OW2 and Mag-OW6. The influence of

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substrate particles on the magnetite-wood composite was addressed by comparing the

performance of Mag-OW2 (no substrate) and Mag-OW5 (with substrate). Effect of pyrolysis

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was by heating one of the composites at 200oC (Mag-OW7). In addition to the earlier

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composites, magnetite Mag and olive wood sawdust OW were also characterized for comparison purposes. Among tested composites, both Mag-OW2 and Mag-OW4 would be taken as

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references to the rest of materials. For Mag-OW2, most of composites were prepared under comparable experiential conditions (same temperature, mass ratio, and stirring time) and hence

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this composite was taken as reference for the rest of composites. In the meantime, Mag-OW4 shall be taken as a reference materials regarding Pb uptake (the best one for Pb uptake)

3.1.

Characterization of the adsorbents

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Characterization of the magnetic adsorbents was conducted by FT-IR (Fig. 1), XRD (Fig. 2), N2 adsorption-desorption for determination of SABET, total pore volume (V) and average pore diameter (P) (Fig. 3 and Table 1), TGA (Fig. 4.a), elemental analysis (Table 1), SAMB (Table 1). Adsorption performance of the adsorbents towards lead was also studied at pH 7 as a priori pollutant. The lead adsorption results are given in Fig. 4.b while Qmax values (from Langmuir 11

equation) are given in Table 1. Summary of various physiochemical properties of the adsorbents are given in Table 1 and plotted in Fig. 5. PCA and HCA outputs are provided in Fig 6. Elemental analysis The mass percent of each element may change as a result of deposition of magnetite under different conditions. For example, more iron oxides mean less carbon; pyrolysis may reduce the

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carbon percentage and these may affect the properties of the adsorbent. The elemental analysis

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(Table 1 and Fig. 5) showed that OW contained 47.4%C. After magnetite deposition, carbon content has generally decreased. The %C in various prepared adsorbents was within the range

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40.2-47.2%. The %C has increased after adsorbent pyrolysis (adsorbent Mag-OW7) due to

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degradation of oxygen containing groups. FT-IR

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The purpose of this section was to provide a semi-quantitative measurement of magnetite deposited on olive wood sawdust. Furthermore, it was reported in the literature that deposition

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conditions of magnetite may affect its IR spectrum [33-35]. In the present work, the IR spectrum of magnetite (Fig. 1) showed a strong absorption band at 545 cm-1 (Fe-O-Fe stretching), a shoulder at 575 cm-1 and a weak band at 1630 cm-1 (Fe-OH deformation). After deposition of magnetite on wood, the band at 545 cm-1 shifted to 555 cm-1. In the literature, IR absorption

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bands of magnetite appeared at 590 and 450 cm-1 (Fe-O bond in tetrahedral and octahedral positions) [33]). Liese [34] and Li et al. [35] reported strong absorption band at 570 cm-1 with a shoulder at 700 cm-1. O–H stretching (3411 cm−1) and O–H deformation (1630 cm−1) were also reported by Iyengar et al. [33] due to adsorbed water molecules on magnetite surface.

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The FT-IR spectrum of olive wood (OW) (Fig. 1) showed strong absorption band at 1030 cm-1 (C-O stretching vibration in cellulose, hemi-cellulose and lignin). Other bands appeared at 1730 cm-1 (C=O stretching in hemicelluloses); 1610 cm-1 (C=O stretching in lignin); 1505 cm-1 (aromatic C=C in lignin); 1155 cm-1 (shoulder) (C-O-C antisymmetric vibration in cellulose and hemicelluloses); 1115 cm-1 (inflection) (O-H association band in cellulose and hemicellulose and C-O stretching). Detailed peak positions and assignments of wood were given in the literature by

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Fabiyi and Ogunleye [36], Chen et al. [37], Ofomaja and Naidoo [38, 39], Rahman and Islam

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[40].

In the present study, the height of the IR absorption peak at 1030 cm-1 (related to C-O stretching

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in OW) was abbreviated as W. The height of the IR absorption peak at 555 cm-1 (related to Fe-O-

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Fe) was abbreviated as Fe. The ratio (Fe/W)IR was calculated and the values are shown in Table 1 and in Fig. 5. This ratio indicated the relative presence of iron oxide in magnetic olive wood

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adsorbents. It was noted that heating the reaction mixture at 50°C gave the highest iron oxides amount while stirring the mixture for 5.0 hours and pyrolysis gave the lowest amount of iron

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oxides. Of course the composite (Mag-OW6, mass ratio 1:7) gave lower iron salts as a result of reducing the starting amounts of iron salts. XRD

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In the literature, many iron oxides and hydroxides may form during the hydrolysis process. This includes wustite (FeO), magnetite (Fe3O4), Fe4O5, Fe5O6, Fe5O7, Fe25O32, Fe13O19, hematite (αFe2O3), β-Fe2O3), maghemite (γ-Fe2O3), ε-Fe2O3, goethite (α-FeOOH), akaganéite (β-FeOOH), lepidocrocite (γ-FeOOH), feroxyhyte (δ-FeOOH), ferrihydrite. So that this issue should be considered when preparing magnetite. Other forms of iron oxide/hydroxide may not have magnetic properties. The only forms of iron oxides that have magnetic properties are magnetite 13

and maghemite. While magnetite is black, maghemite is brown [41]. The purpose of performing XRD experiments was to confirm magnetite formation. The XRD pattern of olive wood sawdust OW (Fig. 2) showed the main diffraction lines of cellulose at 2θ = 16 and 22°, which agreed with those reported by Singh et al. [42]. The diffraction lines of magnetite Mag appeared at 2θ = 30, 35 (strong), 58 and 62° (Fig. 2). All the prepared magnetic wood sorbents (Fig. 2) showed diffraction lines at 2θ = 16, 22, 30, 35, 58 and 62°, which confirms magnetite formation in all the

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prepared magnetic sorbents. From the XRD patterns of the magnetic adsorbents, the height of the

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main magnetite diffraction line (at 2θ = 35°) was abbreviated as Fe while the height of the main diffraction line of wood (at 2θ = 22°) was abbreviated as W. The ratio (Fe/W)XRD was calculated

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(Table 1 and Fig. 5) and it was considered as a relative indicator of the magnetite formation in

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the prepared adsorbents. Obviously there was clear differences in (Fe/W)XRD ratios between magnetic wood sorbents prepared under different experimental conditions. In PMOW, it seems

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that partial degradation of cellulose at 200°C caused an increase in the ratio (Fe/W)XRD relative to other magnetic sorbents. Similar observation and explanation may be recorded for the

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adsorbent prepared at 80°C. In all magnetic sorbents, it was clear that the (Fe/W)XRD was generally lower than (Fe/W)IR which may suggest that not all iron oxides exist as magnetite. Preparation of magnetite in presence or absence of the woody substrate resulted in some interesting results needed to be commented on. To have a fair comparison on this issue, the

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outputs of Mag-OW2 and Mag-OW5 were compared as the former prepared in absence of wood while later in the presence of wood. In fact, preparation of magnetite particles in absence of wood particles may not allowed uniform distribution over woody particles. On the other hand, the presence of active sites in wood can strongly attract more magnetite if deposition was accomplished in the presence of substrate. Characterization tests indicated that both materials 14

have comparable affinity toward Pb ions. The main differences were in SABET and (Fe/W)XRD indices. For Mag-OW2, the SABET was 6 times higher than Mag-OW5 which prepared in the presence of substrate which attributed to the blocking of wood pores by magnetite. The other interesting point was the higher magnetite content (compared to Fe-oxides) when preparation was made in the absence of wood. It seems that wood particles prevent formation of magnetite

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and hence the index (Fe/W)XRD was reduced to 0.23.

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TGA

TGA usually gives an indication of the relative stability of the adsorbent surface against

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degradation by thermal heating at high temperature. In the present study, the presence of Mag on wood surface may protect it and retard degradation of wood components. This is indicated by the

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TGA pattern of Mag (Fig. 4.a) where the final % mass loss (by TGA) values are given in Table

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1 and Fig. 5. It was generally noted that deposition of magnetite on olive wood has generally given more thermal stability to wood against degradation. This observation was confirmed by noting that less thermal mass loss in the 1:3 adsorbent relative to 1:7 adsorbent. More thermal

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stability was also observed in the sorbent prepared at 80°C and slightly in the pyrolyzed sample relative to Mag-OW2 composite. It seems that formation of magnetite in the presence (MagOW2) or absence (Mag-OW5) of woody substrate was not influential on thermal stability or Pb

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uptake (Table 1).

Surface area (SABET and SAMB) The results of N2 adsorption-desorption isotherms at 77 K are shown in Fig. 3 from which SABET surface area, total pore volume (V) and average pore diameter (P) were estimated [43] (See Table 1). From the average pore diameter, it is clear that all our materials are mesoporous (meso15

porous material has a pore diameter between 5-50 nm). The isotherms followed type IV isotherm according to IUPAC classification where a hysteresis loop appeared. In mesoporous material, a hysteresis loop usually appears due to capillary condensation phenomenon [44]. It also indicates that Langmuir model is not obeyed and adsorption sites are not identical. Another explanation is that desorption is slower than adsorption [44].

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Table 1 and Fig. 5 summarises SABET and SAMB. It is important to mention that while SABET indicates the specific surface area based on the porosity of the adsorbent; however SAMB may be

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more related to the surface chemistry of the adsorbent in addition to the sorbent porosity. This is

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in addition to the fact that methylene blue adsorption is condcuted in solution and thus it is closer to real situation. It was noted that the highest SABET and the lowest SAMB were reported for Mag.

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The opposite observation was reported for OW, i.e. the lowest SABET and the highest SAMB were reported for OW. This indicated that deposition of Mag on OW surface is responsible for the

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Adsorption of Pb at pH 7.0

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decreasing SAMB of most composites and increasing the corresponding SABET for all composites.

The results of lead adsorption on various adsorbents (at pH7) are shown in Fig. 4.b. It was reported by Yeneneh et al. [45] that Pb(II) adsorption by lignocellulosic material is usually due to interaction with the predominant functional groups (such as carboxyl, hydroxyl, carbonyl and

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phenolic on the adsorbent surface. So that it is expected that ion exchange mechanism plays an important job in Pb(II) sorption. A study by Wang et al. [46] also stated that at medium pH values, positively charged metal ionic species (such as Pb2+) may replace the surface protons of carboxylic or phenolic groups. So that the following surface reaction may occur (where OWSOH is the surface functional groups): 16

OWS─OH + Pb2+ ⇌ OWS─OPb+ + H+ It was interesting to note that while the minimum lead uptake (Qmax) was recorded for Mag, however, the maximum Qmax of lead was recorded for the magnetic adsorbent that was prepared by stirring the mixture for 5 hours. This adsorbent gave almost the same values of (Fe/W)IR and (Fe/W)XRD which may suggest that all iron oxides were deposited as magnetite. Indeed, this sorbent also gave Qmax even higher than OW itself. So that we cannot attribute the high lead

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uptake to OW, but it seems that a high-lead-uptake sorbent was produced by this deposition

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procedure (5 hours). Indeed, this sorbent gave normal SABET but gave the smallest SAMB value relative to other wood-based magnetic sorbents. Other deposition parameters did not greatly

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affect Qmax values but pyrolysis had almost negative impact on Qmax due to functional group

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degradation upon pyrolysis. It was generally noted that Qmax of lead has an inverse relationship

3.2.

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with SABET and a direct relationship with SAMB as will be discussed later.

Effect of magnetite deposition conditions on physiochemical properties

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The effect of various deposition parameters of magnetite on olive wood sawdust properties are shown in Fig. 5. In this section, Mag-OW2 was considered as the reference adsorbent for comparison purposes. The effect of temperature showed that heating the mixture at 50°C gave the highest SABET, SAMB and iron oxide formation (Fe/W)IR. Heating at 80°C decreased SABET

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and increased thermal stability (less %mass loss (TGA)) and magnetite formation (Fe/W)XRD. It was noted that extending the time of stirring to 5 hours had negative effect on SAMB, SABET and iron oxide formation (Fe/W)IR while magnetite formation (Fe/W)XRD and lead uptake (Qmax) significantly increased. Reducing the Mag-to-OW ratio to 1:7 reduced the SABET and of course reduced both iron oxide (Fe/W)IR and magnetite (Fe/W)XRD while thermal stability decreased 17

(more %mass loss (TGA)). This is a logical result since Mag itself has a relatively higher SABET than OW. The effect of magnetite deposition in the presence/absence of woody substrate showed that the presence of wood while magnetite deposition (i.e. adding ammonia after mixing wood with iron salts) reduced significantly the SABET, iron oxides (Fe/W)IR and magnetite (Fe/W)XRD. This may indicate that iron oxides and magnetite formation was inhibited in this case probably due to interaction of iron ions with wood surface. The effect of pyrolysis of magnetic olive

of

wood showed an increase in %C and magnetite (Fe/W)XRD and a decrease in SAMB, lead uptake

ro

(Qmax) and iron oxides (Fe/W)IR.

-p

The following issues would be drawn regarding the dominating factors on designing magnetitewood composites: a) adding ammonia in the presence of substrate resulted in a negative

re

influence on the SABET, b) deposition of magnetite on wood surface has generally slight effect on SAMB except when the reaction mixture was heated for 5.0 hours, the SAMB noticeably decreased

lP

while Pb removal was two-fold increased, c) heating reaction at 50°C gave the highest SAMB, SABET and iron oxides deposition on wood (Fe/W)IR, d) reducing the Mag-to-OW ratio to 1:7

ur na

(Mag-OW6) had reduced the SABET which confirmed the major effect of magnetite in the SABET of the magnetic adsorbent, e) pyrolysis at 200°C has enhanced the magnetite formation (Fe/W)XRD which retained the same SABET as the reference adsorbent but SAMB and lead uptake (Qmax) had been reduced due to possible degradation of surface functional groups. In all

Jo

composites, it was clear that the (Fe/W)XRD were generally lower than (Fe/W)IR which suggested that not all iron oxides were available as magnetite. Although there was no systematic relationship between (Fe/W)IR and (Fe/W)XRD, however it was noted that the composite that was stirred for 5 hrs (Mag-OW4) gave almost the same values of (Fe/W)IR and (Fe/W)XRD and it gave the highest Qmax value. 18

3.3.

Significance of experimental factors on properties of composites: PCA and HCA

Beside the above discussed univaraite analysis among factors and their influence on physiochemical properties of composites, both PCA and HCA were also applied for better assessment of the collected data. The measured parameters were collected in data matrix X (9×7) and subjected to PCA and HCA and results are provided in Fig 6. Before running PCA, the data

of

was mean centered due to the large variations in the variables like surface areas and (Fe/W)XRD

ro

or (Fe/W)IR ratios which is necessary to get better or informative outputs. As shown in Fig 6A, the physiochemical data for the composites was presented by two PC factors with accumulative

-p

variance of more than 92% which, in fact, allow for classification of composites and figure out the importance of the seven physiochemical variables for samples separation. As shown in Fig

re

6A, Mag and Mag-OW4 behaved in a different manner as they separated for the rest of

lP

composites. Moreover, the composites (Mag-OW2 & Mag-OW3) were positioned very close to each other which reflected their comparable physiochemical properties and increasing

ur na

temperature from 50 to 80°C did not notably affect the final properties of both composites. The unique position of Mag-OW4 would be attributed to either high affinity for Pb or preparation conditions as substrate was added after magnetite formation. The position of Mag in the plot was expected as this material exhibited the lowest Pb uptake and lowest SAMB (Table 1). The

Jo

influence of variables on composites separation is depicted in Fig 6B. The plot indicated that Qmax and SAMB were the most significant physiochemical variables and oppositely correlated in the same time. The variables SABET and TGA/C% were also negatively correlated in the composites. Interestingly, the indices (Fe/W)XRD and (Fe/W)IR have very small influence compared to the rest of variables. In other words, changing preparation conditions did not 19

significantly affect the earlier indices. The anticorrelation SABET and TGA% would suggest that less thermally stable sorbent has more SABET. In fact, the poor correlation among Pb adsorption (or Qmax) and SABET /SAMB (Fig. 6B) would support the fact that Pb removal from solution was not a pure physical process. In fact, very interesting outputs would be deduced from the bi-plot or Fig 6C. Simply, the unique position of Mag-OW4 (Fig 6A) is attributed to its high affinity for Pb ions while the very modest SABET (3 m2 g-1) is the reason for the position of Mag. In the

of

meantime, the comparable performance of Mag-OW2 and Mag-OW3 was attributed to the

ro

higher SABET values. The plot also indicated that variations in C% and TGA% were not

significant while changing experimental conditions. Based on the measured physiochemical

-p

parameters, HCA revealed that the seven composites would be clustered into four main groups:

re

(Mag), (OW, Mag-OW5, Mag-OW6), (Mag-OW4) and (Mag-OW1, Mag-OW2, Mag-OW3, Mag-OW6, Mag-OW7). It was interesting to notice that OW was grouped with the composites

lP

Mag-OW5 & Mag-OW6 which may be attributed to comparable Pb uptake and surface areas for the materials. However, both composites are of higher industrial value due to simple

ur na

separation from solution. It was also interesting to notice that Mag-OW6 and Mag-OW7 were grouped together as the later one was prepared at higher magnetite ratio (1:7).

Conclusions

Jo

Deposition of magnetite on olive wood sawdust by the coprecipitation-hydrothermal method under different conditions has various effects and caused various changes on physiochemical and lead adsorption properties of the produced magnetic adsorbents. Some correlations between some magnetic wood properties could be constructed. Deposition of magnetite on olive wood sawdust has generally increased the thermal stability of the wood, increased SABET, decreased 20

SAMB and decreased lead uptake. However, the adsorbent prepared by stirring the reaction mixture for 5 hours significantly improved the lead uptake by the produced magnetic wood sorbent. The IR can be used as a semi-quantitative method for relative estimation of iron oxide deposition on wood surface, while XRD can be used as a semi-quantitative method of estimating magnetite formation in wood surface. All the preparation conditions gave magnetite as indicated by similar XRD diffraction lines, but IR data showed that various conditions produced various

of

amounts of deposited iron oxides and magnetite on olive wood sawdust. IR and XRD data also

ro

showed that not all the deposited iron oxides was in the form of magnetite. Preparation of

composites in the presence of woody substrate resulted in lower magnetite and higher iron oxides

-p

and much lower SABET. PCA analysis indicated that the behavior of Mag and Mag-OW4 were

re

notably different from the rest composites. However, SABET, SAMB, and Pb removal were more

lP

significant parameters than (Fe/W)XRD and (Fe/W)IR for assessing composites.

Conflict of interest statement

declare.

ur na

On behalf of all authors, the corresponding author states that there is no conflict of interest to

Jo

Acknowledgements

The authors are grateful for the financial support from the Deanship of Scientific Research/The Hashemite University. Composites were prepared by R. Al-Salamin & I. Fasfous. FT-IR analysis was conducted by N. Al-Hashimi & D. Tahboub. Lead adsorption was conducted by H. Alshamaly. PCA and XRD were conducted by Y. Al-Degs & J. Abdelghani. 21

References

Jo

ur na

lP

re

-p

ro

of

[1] Y. Wang, B. Du, J. Wang, Y. Wang, H. Gu, X. Zhang, Synthesis and characterization of a high capacity ionic modified hydrogel adsorbent and its application in the removal of Cr(VI) from aqueous solution, Journal of Environmental Chemical Engineering, 6 (2018) 6881-6890. [2] X. Zhang, Y. Yang, X. Lv, Y. Wang, N. Liu, D. Chen, L. Cui, Adsorption/desorption kinetics and breakthrough of gaseous toluene for modified microporous-mesoporous UiO-66 metal organic framework, Journal of Hazardous Materials, 366 (2019) 140-150. [3] X. Zhang, X. Lv, X. Shi, Y. Yang, Y. Yang, Enhanced hydrophobic UiO-66 (University of Oslo 66) metal-organic framework with high capacity and selectivity for toluene capture from high humid air, Journal of Colloid and Interface Science, 539 (2019) 152-160. [4] X. Zhang, Y. Yang, W. Huang, Y. Yang, Y. Wang, C. He, N. Liu, M. Wu, L. Tang, gC3N4/UiO-66 nanohybrids with enhanced photocatalytic activities for the oxidation of dye under visible light irradiation, Materials Research Bulletin, 99 (2018) 349-358. [5] Y. Wang, Y. Wang, L. Yu, J. Wang, B. Du, X. Zhang, Enhanced catalytic activity of templated-double perovskite with 3D network structure for salicylic acid degradation under microwave irradiation: Insight into the catalytic mechanism, Chemical Engineering Journal, 368 (2019) 115-128. [6] S. Daneshfozoun, M.A. Abdullah, B. Abdullah, Preparation and characterization of magnetic biosorbent based on oil palm empty fruit bunch fibers, cellulose and Ceiba pentandra for heavy metal ions removal, Industrial Crops and Products, 105 (2017) 93–103. [7] S.F. Yaacob, N.S. Abd Razak, T.T. Aun, S.K. Rozi, A.K. Jamil, S. Mohamad, Synthesis and characterizations of magnetic bio-material sporopollenin for the removal of oil from aqueous environment, Industrial Crops and Products, 124 (2018) 442-448. [8] W. Wei, L. Ang, P. Shanshan, W. Qilin, Z. Lu, Y. Jixian, M. Fang, N. Bing-Jie, Synthesis of core-shell magnetic nano-composite Fe3O4@ Microbial extracellular polymeric substances for simultaneous redox sorption and recovery of silver ions as silver nanoparticles, ACS Sustainable Chemistry & Engineering, 6 (2018) 749-756. [9] A.H. El-Sheikh and J.A. Sweileh, Recent applications of carbon nanotubes in solid phase extraction and preconcentration: a review, Jordan Journal of Chemistry, 6 (2011) 1-16. [10] A. El-Sheikh, J. Sweileh, M. Saleh, Partially pyrolyzed olive pomace sorbent of high permeability for preconcentration of metals from environmental waters, Journal of hazardous materials, 169 (2009) 58-64. [11] A. El-Sheikh, A. Newman, A. Said, A. Alzawahreh, M. Abu-Helal, Improving the adsorption efficiency of phenolic compounds into olive wood biosorbents by pre-washing with organic solvents: Equilibrium, kinetic and thermodynamic aspects, Journal of Environmental Management, 118 (2013) 1-10. [12] A. El-Sheikh, M. Abu Hilal, J. Sweileh, Bio-separation, speciation and determination of chromium in water using partially pyrolyzed olive pomace sorbent, Bioresource Technology, 102 (2011) 5749-5756. 22

Jo

ur na

lP

re

-p

ro

of

[13] A. El-Sheikh, A. Alzawahreh, J. Sweileh, Preparation of an efficient sorbent by washing then pyrolysis of olive wood for simultaneous solid phase extraction of chloro-phenols and nitrophenols from water, Talanta, 85 (2011) 1034 – 1042. [14] B. Wang, J. Wen, S. Sun, H, Wang, S. Wang, Q. Liu, A. Charlton, R. Sun, Chemosynthesis and structural characterization of a novel lignin-based bio-sorbent and its strong adsorption for Pb (II), Industrial Crops and Products, 108 (2017) 72-80. [15] A.H. El-Sheikh, I.I. Fasfous, R.M. Al-Salamin, A.P. Newman, Immobilization of citric acid and magnetite on sawdust for competitive adsorption and extraction of metal ions from environmental waters, Journal of Environmental Chemical Engineering, 6 (2018) 5186-5195. [16] A.H. El-Sheikh, A.M. Shudayfat, I.I. Fasfous, Preparation of magnetic biosorbents based on Cypress wood that was pretreated by heating or TiO2 deposition, Industrial Crops and Products, 129 (2019) 105-113. [17] J. Shah, M. Jan, M. Khan, S. Amir, Removal and recovery of cadmium from aqueous solutions using magnetic nanoparticle-modified sawdust: kinetics and adsorption isotherm studies, Desalination and Water Treatment, 57 (2015) 9736-9744. [18] Z. Liu, H. Wang, C. Liu, Y. Jiang, G. Yu, X. Mu, X. Wang, Magnetic cellulose–chitosan hydrogels prepared from ionic liquids as reusable adsorbent for removal of heavy metal ions, Chemical Communications, 48 (2012) 7350. [19] J.-X. Yu, L.-Y. Wang, R.-A. Chi, Y.-F. Zhang, Z.-G. Xu, J. Guo, Competitive adsorption of Pb2+ and Cd2+ on magnetic modified sugarcane bagasse prepared by two simple steps, Applied Surface Science, 268 (2013) 163–170. [20] M. Zhang, B. Gao, S. Varnoosfaderani, A. Hebard, Y. Yao, M. Inyang, Preparation and characterization of a novel magnetic biochar for arsenic removal, Bioresource Technology, 130 (2013) 457–462. [21] H.K. Reddy, S.-M. Lee, Magnetic biochar composite: Facile synthesis, characterization, and application for heavy metal removal, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 454 (2014) 96–103. [22] D. Mohan, H. Kumar, A. Sarswat, M. Alexandre-Franco, C.U. Pittman, Cadmium and lead remediation using magnetic oak wood and oak bark fast pyrolysis bio-chars, Chemical Engineering Journal, 236 (2014) 513–528. [23] X. Luo, X. Lei, N. Cai, X. Xie, Y. Xue, F. Yu, Removal of Heavy Metal Ions from Water by Magnetic Cellulose-Based Beads with Embedded Chemically Modified Magnetite Nanoparticles and Activated Carbon, ACS Sustainable Chemistry & Engineering, 4 (2016) 3960–3969. [24] E. Cheraghipour, A.M. Tamaddon, S. Javadpour, I.J. Bruce, PEG conjugated citrate-capped magnetite nanoparticles for biomedical applications, Journal of Magnetism and Magnetic Materials, 328 (2013) 91-95. [25] L. Li, K.Y. Mak, C.W. Leung, K.Y. Chan, W.K. Chan, W. Zhong, P.W.T. Pong, Effect of synthesis conditions on the properties of citric-acid coated iron oxide nanoparticles, Microelectronic Engineering, 110 (2013) 329-334. [26] M. Racuciu, D.E. Creanga, A. Airinei, Citric-acid–coated magnetite nanoparticles for biological Applications, The European Physical Journal E 21 (2006) 117-121. [27] A. Mikhaylova, V. Sirotinkin, M. Fedotov, V. Korneyev, B. Shamray, L. Kovalenko, Quantitative determination of content of magnetite and maghemite in their mixtures by X-Ray diffraction methods inorganic materials, Applied Research, 7 (2016) 130–136. [28] R.G. Brereton, Chemometrics: Data Analysis for the Laboratory and Chemical Plant, First Edition (2003), Oxford Press, UK. 23

Jo

ur na

lP

re

-p

ro

of

[29] Y.S. Al-Degs, R. Abu-El-Halawa, S.S. Abu-Alrub, Analyzing adsorption data of erythrosine dye using principal component analysis. Chemical Engineering Journal, 191 (2012) 185-194. [30] Y.S. Al-Degs, A.H. El-Sheikh, S. Jaber, Application of heated date seeds as a novel extractant for diuron from water. The Arabian Journal of Chemistry, 6 (2012) 121-129. [31] J.A. Sweileh, K.Y. Misef, A.H. El-Sheikh, M.S. Sunjuk, Development of a new method for determination of Al in Jordanian foods and drinks: solid phase extraction and adsorption of Al3+D-mannitol on carbon nanotubes, Journal of Food Composition and Analysis 33 (2014) 6-13. [32] A.H. El-Sheikh, M.K. Al-Jafari, J.A. Sweileh, Solid phase extraction and uptake properties of multi-walled carbon nanotubes of different dimensions towards some nitro-phenols and chloro-phenols from water. International Journal of Environmental Analytical Chemistry 92 (2012) 190–209. [33] S. Iyengar, M. Joy, C. Ghosh, S. Dey, R. Kotnalad, S. Ghosh, Magnetic, X-ray and Mossbauer studies on magnetite/maghemite core-shell nanostructures fabricated through aqueous route, RSC Advances 4 (2014) 64919-64929. [34] H. Liese, An infrared absorption analysis of magnetite, The American Mineralogist 52 (1967) 1198-1205. [35] Y-S. Li, J. Church, A. Woodhead, Raman spectroscopic studies on iron oxide magnetic nano- particles and their surface modifications, journal of magnetism and magnetic materials 324 (2012) 1543-1550. [36] J. Fabiyi, B. Ogunleye, Mid-infrared spectroscopy and dynamic mechanical analysis of heat treated obeche (Triplochiton scleroxylon) wood, Maderas: Ciencia y Technologia 17 (2015) 516. [37] H. Chen, C. Ferrari, M. Angiuli, J. Yao, C. Raspi, E. Bramanti, Qualitative and quantitative analysis of wood samples by Fourier transform infrared spectroscopy and multivariate analysis, Carbohydrate Polymers 82 (2010) 772–778. [38] A. Ofomaja, E. Naidoo, Biosorption of lead(II) onto pine cone powder: Studies on biosorption performance and process design to minimize biosorbent mass, Carbohydrate Polymers 82 (2010) 1031–1042. [39] A. Ofomaja, E. Naidoo, Biosorption of copper from aqueous solution by chemically activated pine cone:A kinetic study, Chemical Engineering Journal 175 (2011) 260– 270. [40] M. Rahman, M. Islam, Effects of pH on isotherms modeling for Cu(II) ions adsorption using maple wood sawdust, Chemical Engineering Journal 149 (2009) 273–280. [41] U. Schertmann, R. M. Cornell, Iron oxides in the laboratory, preparation and characterization, 2nd ed 2000, Wiley-VCH, Germany. [42] S. Singh, G. Cheng, N. Sathitsuksanoh, D. Wu, P. Varanasi, A. George, V. Balan, X. Gao, R. Kumar, B. Dale, C. Wyman, B. Simmons, Comparison of different biomass pretreatment techniques and their impact on chemistry and structure, Frontiers in Energy Research 2 (2014) 62. [43] X. Zhang, Y. Yang, L. Song, J. Chen, Y. Yang, Y. Wang, Enhanced adsorption performance of gaseous toluene on defective UiO-66 metal organic framework: Equilibrium and kinetic studies, Journal of Hazardous Materials, 365 (2019) 597-605. [44] J. M. Thomas, W. J. Thomas, Principles and Practice of Heterogeneous Catalysis, Weinheim, 1997. [45] A.M. Yeneneh, S. Maitra, U. Eldemerdash, Study on biosorption of heavy metals by modified lignocellulosic waste, Journal of Applied Sciences, 11 (2011) 3555-3562. 24

Jo

ur na

lP

re

-p

ro

of

[46] Q. Wang, J. Li, C. Chen, X. Ren, J. Hu, X. Wang, Removal of cobalt from aqueous solution by magnetic multiwalled carbon nanotube/iron oxide composites, Chemical Engineering Journal, 174 (2011) 126-133.

25

1.02

0.98

0.96 0.94

0.92

Transmittance

1

of

0.9

0.88

1400

1200

1000

800

600

Mag-OW3

1.02

re

Mag-OW2

-p

Wavenumber (cm-1) Mag-OW1

400

1

1600

Jo

1800

ur na

lP

0.98

1400

Mag-OW4

1200

0.96 0.94 0.92 0.9 0.88

0.86 1000

800

600

400

Wavenumber (cm-1) Mag-OW6

Mag-OW5

26

Mag-OW7

Transmittance

1600

ro

1800

0.96 0.92

0.88

of

0.84

Transmittance

1

3600

2800

2000

1200

Jo

ur na

lP

Fig. 1: FT-IR spectra of the adsorbents.

Mag

re

OW

-p

Wavenumber (cm-1)

ro

0.8

27

400

10000

Intensity (a.u.)

8000

6000

2000

15

20

25

30

2 θ (°) Mag-OW2

Mag-OW3

6000

2000

Mag-OW6

lP

8000

ur na

Intensity (a.u.)

10000

4000

40

re

12000

Mag-OW4

-p

Mag-OW1

35

ro

10

of

4000

Jo

10

15

20

Mag

OW

25

30

35

40

2 θ (°) Mag-OW7

Mag-OW5

Fig. 2: XRD patterns of the magnetic adsorbents prepared under different deposition conditions

28

250

Volume adsorbed (cm3 g-1)

Mag 200

150

100

50

0

0.2

0.4

0.6

0.8

of

0 1

ro

Relative presuure (P/Po) 40 Mag-OW1

Mag-OW6

Mag-OW5

OW

-p

30 25

re

20 15 10 5 0 0

0.2

0.4

lP

Volume adsorbed (cm3 g-1)

35

0.6

0.8

1

ur na

Relative presuure (P/Po) 60

Mag-OW3

Mag-OW4

40 30

Jo

Volume adsorbed (cm3 g-1)

Mag-OW2

50

20 10

0 0

0.2

0.4

0.6

0.8

1

Relative presuure (P/Po)

Fig. 3: N2 adsorption-desorption isotherms at 77 K of the adsorbents. 29

140 120

Mag-OW1

Mag-OW2

Mag-OW3

Mag-OW4

Mag-OW5

Mag

OW

Mag-OW7

Mag-OW6

100

Mass (%)

Mag

80 60 Mag-OW3

of

40 20

0

100

200

300

44 40 32

28

Mag-OW2 Mag-OW3 Mag-OW4

Mag-OW6

lP

24 20 16 8 4 0 0

ur na

12

2

4

6

8

Mag-OW5 Mag OW

Mag-OW7

10

12

14

16

Ce (mg L -1)

Jo

Fig. 4: a) TGA and b) adsorption isotherms of Pb (II) on various adsorbents at pH 7

30

600

Mag-OW1

re

36

qe (mg g-1)

500

-p

a)

b)

400

Temperature ( C)

Mag-OW5

ro

OW

0

18

SA BET (m2 g-1)

SA MB (m2 g-1)

C (%)

% mass loss (TGA)

160 140

100 80 60

of

Arbitrary units

120

40

0

ro

20

Mag-OW1 Mag-OW2 Mag-OW3 Mag-OW4 Mag-OW6 Mag-OW5 Mag-OW7

OW

Mag

OW

(Fe/W)XRD*100 160

100

60 40 20 0

ur na

Arbitrary units

120

80

(Fe1/W1)IR*100

Qmax (mg g-1)

lP

140

re

-p

Adsorbent

Mag

Jo

Mag-OW1 Mag-OW2 Mag-OW3 Mag-OW4 Mag-OW6 Mag-OW5 Mag-OW7

Adsorbent

Fig. 5: Effect of various conditions for deposition of magnetite on olive wood sawdust on various adsorbent properties.

31

B)

of

ro

-p

re

lP

ur na

Jo A)

32

D)

of ur na

lP

re

-p

ro

C)

Fig 6: PCA of physicochemical properties of composites.

Jo

(A: Score/composites plot B: Loading/ physicochemical properties plot C: Biplot D: Dendrogram)

33

Table 1: Prepared composites with characterization parameters under different deposition conditions %C Conditions %mas SAaBE Operational

MagOW4

MagOW5

MagOW6

MagOW7

Jo

Mag OW

a.

b. c. d. e.

(m2 g-1)

SAM

(Fe/W)XR

B

D

d

(Fe/W)I R

e

(m2 g-1)

Langmuir Qma r2 x

74.4

34

0.04 7

5.5

99

0.56

1.0

23

0.91 9

40. 2

75.1

48

0.09 2

7.7

120

0.45

1.40

26

0.92 1

42. 1

56.7

31

0.06 2

8.0

120

0.71

42. 1

72.3

30

0.06 9

42. 9

74.1

8

45. 6

0.03 3

89.6

of

41. 9

1.23

23

0.92 1

ro -p

MagOW3

T

Pc (nm )

lP

MagOW2

No substrate, T: 25 oC, ST: 30 min, Ratio: 1:3, PYR: No No substrate, T: 50 oC, ST: 30 min, Ratio: 1:3, PYR: No No substrate, T: 80 oC, ST: 30 min, Ratio: 1:3, PYR: No No substrate, T: 50 oC, ST: 5.0 hr, Ratio: 1:3, PYR: No With substrate, T: 50 oC, ST: 30 min, Ratio: 1:3, PYR: No No substrate, T: 50 oC, ST: 30 min, Ratio: 1:7, PYR: No No substrate, T: 50 oC, ST: 30 min, Ratio: 1:3, PYR: 200 oC T: 50 oC, ST: 30 min

ur na

MagOW1

s loss (TGA )

Vb (cc g-1)

9.2

88

re

Abbreviati on

0.76

0.72

49

0.93 2

16. 5

115

0.23

0.92

23

0.92 9

17

0.01 8

4.2

120

0.22

0.56

22

0.91 9

47. 2

69.5

48

0.09 2

7.7

102

0.84

0.47

19

0.92 0

0.7 0 47. 4

9.1

139

-

-

12

3

10. 3 8.0

54

99.9

0.36 1 0.00 6

122

-

-

29

0.89 8 0.98 1

No substrate: magnetite was formed in the absence of substrate, with substrate: magnetite was formed in the presence of substrate, T: temperature of magnetite formation, ST: stirring time for deposition of magnetite by wood, ratio: mass ratio of magnetite to wood, PYR: pyrolysis temperature. Total pore volume (V) was measured at P/Po=0.99 Average pore diameter (P) = 4 V / SABET The ratio (Fe/W)XRD was considered as a relative indicator of magnetite formation The ratio (Fe/W)IR was considered as a relative indicator of iron oxides formation

34