Environmental Science Nano - soil-interface.cn · soil using a magnet. In addition, when BMN was loaded on filter paper, the system of BMN and filter paper could be conveniently used

EnvironmentalScienceNano

PAPER

Cite this: Environ. Sci.: Nano, 2019,

6, 478

Received 8th November 2018,Accepted 11th January 2019

DOI: 10.1039/c8en01257a

rsc.li/es-nano

Oxidation and removal of AsĲIII) from soil usingnovel magnetic nanocomposite derived frombiomass waste†

Jianghu Cui, ‡a Qian Jin,‡b Yadong Li a and Fangbai Li *a

A novel biomass-derived magnetic nanocomposite, named BMN, was fabricated via one-step pyrolysis

process. BMN exhibited excellent AsĲIII) removal capability, high adsorption capacity (16.23 mg g−1), magne-

tism, reusability and low cost. Importantly, when BMN was loaded onto sponges with a microporous struc-

ture, its removal of AsĲIII) from soil capability was improved. The system of BMN and sponges could effi-

ciently remove AsĲIII) from soil and the resulting BMN/sponge/AsĲIII) complex could be easily separated from

soil using a magnet. In addition, when BMN was loaded on filter paper, the system of BMN and filter paper

could be conveniently used as an excellent filter layer to control migration of AsĲIII) in soil. Pot incubations

indicated that BMN could increase the pH of soil and decrease the concentration of available arsenic in

soil. AsĲIII) ion removal by BMN occurred via three pathways: (1) adsorption of AsĲIII) anions via electrostatic

attractions, (2) oxidation of AsĲIII) to AsĲV) by reactive oxygen, and (3) immobilization of AsĲIII) and AsĲV) by

iron nanoparticles. Therefore, this work provides a low-cost method for removal of AsĲIII) from soil, also

promoting recovery and utilization of palm waste.

1. Introduction

Soil pollution by heavy metal ions has been a worldwide con-cern owing to its huge potential harm to animals, plants andhumans.1,2 Trivalent arsenic, AsĲIII), which is one of the mosttoxic heavy metal elements, has caused many environmentalproblems because of its high toxicity and carcinogenicity inhumans.3,4 The continuously intensified and diffused arsenicpollution is mainly caused by anthropogenic activities suchas mining, industrial pollutant discharge and use of arsenicpesticides.5,6 The predominant forms of inorganic arsenic are

AsĲIII) and AsĲV). The more toxic AsĲIII) is the dominant speciesin reductive environments such as paddy soil.7 Therefore, itis urgent to develop effective measures for removing AsĲIII)from soil.

In the past decades, various technologies have been devel-oped in order to remediate the As-contaminated soil, such asamendments stabilization,8 electro-kinetics,9 acid flushing,10

phytoremediation,11 and agronomic mitigation.12 However,electro-kinetics and acid flushing could destroy the soil phys-icochemical properties and cause secondary pollution. Thephytoremediation and agronomic mitigation strategies couldchange traditional cropping mode. Meanwhile, it was diffi-cult to apply these technologies on a large scale because ofhigh cost. Hence, soil amendments are receiving increasingattention in the remediation of soil owing to their simplicityof operation, low cost and high efficiency.13 For example,Moon et al. indicated that addition of lime could reduce mo-bility and bioavailability of arsenic in contaminated soil byforming calcium–arsenic precipitates.14 Deng et al. reported

478 | Environ. Sci.: Nano, 2019, 6, 478–488 This journal is © The Royal Society of Chemistry 2019

aGuangdong Key Laboratory of Integrated Agro-environmental Pollution Control

and Management, Guangdong Institute of Eco-environmental Science & Technol-

ogy, Guangzhou 510650, China. E-mail: [email protected]; Tel: +86 20 37021396bCollege of Agriculture, Shihezi University, Shihezi 832000, Xinjiang, China

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c8en01257a‡ Jianghu Cui and Qian Jin contributed equally to this work.

Environmental significance

Soil pollution by arsenic has been a worldwide concern because of arsenic's carcinogenicity and high toxicity to humans. We developed a novel biomass-derived magnetic nanocomposite (BMN) for the removal of AsĲIII) from soil. The obtained BMN exhibited excellent AsĲIII) removal capability. Importantly,BMN could efficiently remove AsĲIII) from soil and control the migration of AsĲIII) in soil using loading sponges and filter paper, respectively. Furthermore,plot experiments indicated that BMN could remediate the As-contaminated paddy soil via increasing its pH and decreasing the concentration of effective ar-senic. The mechanisms of AsĲIII) removal by BMN are also discussed in detail. This work provides a promising approach for a low cost removal of AsĲIII)from soil and promotes recovery and utilization of biomass wastes.

http://crossmark.crossref.org/dialog/?doi=10.1039/c8en01257a&domain=pdf&date_stamp=2019-02-11

http://orcid.org/0000-0002-0108-837X

http://orcid.org/0000-0002-7166-3261

http://orcid.org/0000-0001-9027-9313

Environ. Sci.: Nano, 2019, 6, 478–488 | 479This journal is © The Royal Society of Chemistry 2019

that application of sepiolite could reduce the mobility andbioavailability of arsenic owing to its strong surface adsorp-tion and ion exchange capacity.15 However, addition of theseminerals could destroy the physicochemical properties of soiland, therefore, greatly hinders their application.

Recently, various iron materials have been employed forthe removal of AsĲIII) from water.16,17 Therein, some iron ma-terials are also used for remediation of As-contaminated soilowing to their high adsorption capacity and abundant redox-active sites.18–20 Our previous studies have also suggestedthat Fe amendments can reduce effectively arsenic mobilityand bioavailability in paddy soils.21,22 In addition, some stud-ies have found that nanoscale iron materials displayed higherremoval efficiency of arsenic because of their unique physicaland chemical properties compared with bulk iron materials,such as large specific surface area, numerous active sites andstrong redox capacity.23,24 For example, addition of nanoscalezero-valent iron to soil could decrease the concentration ofarsenic in leachates, soil pore water and plant shoots by98%, 99% and 84%, respectively.25 Iron oxide nanoparticleswere also successfully used for removal of arsenic in sandysoil owing to their strong adsorption, large retardation factorand resistant desorption.26 However, application of thesepure iron nanomaterials was greatly hindered because of sev-eral disadvantages, such as serious aggregation, difficult sep-aration and high cost.27 Therefore, it is rather important todevelop a new amendment containing iron nanoparticleswith high efficiency, low cost and simple implementation forremediation of As-contaminated soil.

Previous studies suggested that biomass as a renewable re-source was usually used to prepare biochar with a porousstructure and abundant active groups.28 It was widely appliedin the field of soil amendment for the removal of heavymetals.29 However, our previous studies found that additionof biochar could increase the bioavailability of arsenic in thearsenic-contaminated flooded paddy soil by simultaneouslystimulating microbial reduction of AsĲV) and FeĲIII).30,31 Tosolve this problem, a modified-biochar is urgently needed toremove AsĲIII) from soil effectively.

In the present study, a novel biomass-derived magneticnanocomposite (BMN) was fabricated via one-step pyrolysisof iron-impregnated palm fiber. The results showed thatBMN possessed excellent AsĲIII) removal capacity and couldbe reused multiple times. Importantly, a magnetic separationsystem was developed by loading BMN into porous sponge tocollect BMN/sponge–AsĲIII) from soil. The effect of the amountof BMN in sponge on the removal efficiency of AsĲIII) fromsoil was investigated. In addition, BMN, supported by filterpaper, was used to control the migration of AsĲIII) in soil. Potincubations were also carried out to investigate the influenceof BMN on the pH value of soil and the concentrations ofavailable arsenic in soil. Various methods of characterizationwere used to reveal the removal mechanism of AsĲIII) by BMN.This study provides a promising method for the removal ofAsĲIII) from soil, which can be applied on a large scale in thefuture.

2. Materials and methods2.1 Materials

FeCl3 was purchased from Damao Chemical Reagent Com-pany (Tianjin, China). NaAsO2 was purchased from AnpelLaboratory Technologies Company (Shanghai, China). Otherchemicals were provided by Guangzhou Chemical ReagentCompany (Guangzhou, China). All chemicals were of analyti-cal grade and used without further purification. Milli-Q waterwas used for all experiments. Palm fiber was dried at 80 °Cfor 12 h and ground into powder.

2.2 Preparation of BMN nanocomposite

BMN nanocomposite was prepared following a revisedmethod.32 As presented in Fig. 1, 60 g FeCl3 was dissolved in60 mL deionized water. The palm fiber powder was immersedinto the prepared FeCl3 solution for 2 h. The mixture wasdried at 80 °C for 2 h in air, and the obtained iron-impregnated biomass was pyrolyzed in a furnace at a temper-ature of 600 °C in the N2 environment for 1 h. The obtainedsample was thoroughly washed with deionized water severaltimes to remove impurities and then oven-dried at 80 °C. Fi-nally, the obtained BMN powders were collected and sealedin a container before use.

2.3 Characterization of BMN nanocomposite

The morphology of samples was analyzed using scanningelectron microscopy (SEM) and transmission electron micros-copy (TEM) with a JEOL JEM-2100F field emission electronmicroscope equipped with Oxford INCA Energy TEM 200 EDSdevices with an accelerating voltage. The obtained sampleswere analyzed by XRD performed on X-ray diffractometerwith a Cu target in the 2θ range from 5° to 80° (40 kV, 30mA, λ = 1.54051 Å). FTIR spectra of samples was recorded inthe range of 4000–400 cm−1 with KBr as the matrix by using aNicolet 6700 FT-IR spectrophotometer. Dried samples ofBMN after the reaction with AsĲIII) were characterized usingX-ray photoelectron spectroscopy (XPS) performed on aScienta ESCA 300 spectrometer equipped with an 8 kW rotat-ing anode source to provide monochromatic Al Kα (hν =1486.7 eV) radiation. Concentrations of AsĲIII)/AsĲV) were de-termined using atomic florescence spectroscopy (SA-20, JitianInc., Beijing, China), and the concentrations of total arsenicwere analyzed using a hydride generation-atomic fluores-cence spectrometer (AFS-830, Titan Instruments, Beijing,China).

Fig. 1 Illustration of strategy for the preparation of BMNnanocomposite.

Environmental Science: Nano Paper


2.4 AsĲIII) removal experiments

Batch adsorption experiments were carried out in glass vials.A certain amount of BMN (0.02 g) was added to 10 mL AsĲIII)solutions. AsĲIII) solution was freshly prepared from NaAsO2

and deoxygenated by sparging with nitrogen (high purity,>99.9%) for 30 min. NaCl (0.1 M) was introduced into the so-lution as a background electrolyte. The pH of solutions wasadjusted using 0.1 M HCl or NaOH. The stoppered glass vialswere then shaken using a temperature-controlled shaker(HZC-250, Taicang, China) at 200 rpm and 25 °C for 24 h.Shaking time of 24 h was sufficient to ensure adsorptionequilibrium via preliminary kinetic tests. Isotherms experi-ments were carried out at different concentrations of AsĲIII)(0.5 to 50 mg L−1) and pH (4.0, 7.0 and 9.0). Kinetics experi-ments were also carried out under different initial concentra-tions of AsĲIII) (5, 10, 15 and 20 mg L−1) and the pH value ofthe AsĲIII) solution was adjusted to 7.0. After a contact time of24 h, the resulting suspension was centrifuged at 10 000 rpmfor 5 min, and then the concentrations of AsĲIII) in superna-tant was measured. In order to determine the reusability ofthe samples, 0.04 g BMN was added into 20 mL AsĲIII) solu-tion (20 mg L−1, pH = 4.0). Then, the mixture was shaken at200 rpm and 30 °C for 8 h and its contents were separated bya magnet. The separated solid was immersed in 10 mL NaOH(0.1 M) solution for 8 h and washed with distilled water untilneutral pH was reached, then dried at 60 °C for next adsorp-tion. The adsorption capacity (Qe) and removal efficiency(RE) of AsĲIII) from water were calculated following the previ-ous study:33

QC C V

Mee

0 , (1)

RE e% %,

C CC0

0

100 (2)

where C0 and Ce are the initial and remaining AsĲIII) concen-trations (mg L−1), respectively. V and M are the volume of thesolution and the amount of the adsorbent, respectively.

The zeta potential of BMN in AsĲIII) solution at differentpH values was determined by the zeta potential analyzer(Zetasizer Nano ZS90, Malvern Instruments). The oxidationreduction potentials of BMN in AsĲIII) solution at different pHvalues were measured using a multi dual-input meter(HQ40D) with a redox Pt electrode. In addition, during theadsorption kinetics experiment, the H2O2 concentrations ofsolutions were measured using the potassium titaniumĲIV) ox-alate spectrophotometry method.34

2.5 Investigation of AsĲIII) removal efficiency of BMNnanocomposite from soil

2.5.1 Effect of BMN on the leaching behavior of AsĲIII). Drysand (50–100 mesh) was mixed with dry soil (50–100 mesh) ina certain weight ratio (Wsand/Wsoil = 7 : 3). Leaching systems

were prepared as follows. Thirty g sand–soil mixture was di-vided into two parts. One part (20 g) was placed into a centri-fuge tube (60 mL) with a hole (diameter of 2 mm) at the bot-tom. Then, a piece of filter paper with appropriate size wasplaced on the soil–sand mixture and kept a flat, and a givenamount of BMN was placed flat on top of filter paper. Finally,another part of sand–soil mixture (10 g) was also added intothe centrifuge tube. The BMN-loaded filter paper was placedin the middle of the sand–soil mixture. The leachate was col-lected after being sprayed with 50 mL AsĲIII) solution (100 mgL−1, pH = 4.0) and centrifuged for 5 min (4500 rpm). Finally,the concentration of AsĲIII) in the leachate was measured.35 Allexperiments were performed in quintuplicate. The removal ef-ficiency (REleaching) of AsĲIII) was calculated as follows:

REleaching L

C CC0

0

100%, (3)

where C0 and CL are the initial concentrations of AsĲIII) andthe concentration of AsĲIII) in the leachate, respectively.

2.5.2 Removal of AsĲIII) from soil suspension. A certainamount of dry soil (5 g) was mixed with 30 mL of AsĲIII) solu-tion (20 mg L−1, pH = 4.0) in a beaker (50 mL). A givenamount of BMN powder was loaded onto porous sponge (10mg sponge). The detailed methods of preparing BMN-loadedsponges are presented in (ESI†). The obtained BMN/spongewas placed into the soil–AsĲIII) suspension. The resulting sys-tem was shaken at 200 rpm for 24 h, and then the BMN/sponge/As particles were collected with a magnet on a plasticfilter. The rest of the soil suspension was transferred to cen-trifuge tubes, and then centrifuged (4500 rpm) for 5 min. Theconcentrations of AsĲIII) in the supernatant were measured.All experiments were performed in quintuplicate. The re-moval efficiency of AsĲIII) from soil suspension was calculatedas follows:

REsoil t

C CC0

0

100%, (4)

where C0 and Ct are the initial and resulting AsĲIII) concentra-tions, respectively.

2.5.3 Removal of AsĲIII) from sandy soil. Sandy soil (400 g)was mixed with 50 mL AsĲIII) solution (20 mg L−1, pH = 4.0) toobtain the mixture of sandy soil and AsĲIII). A given amount ofBMN (10, 15, 20 and 25 mg) was loaded onto 10 mg of sponge(ESI†). The resulting BMN/sponge particles were placed intothe mixture of sandy soil and AsĲIII). Then the system wasstirred at 200 rpm for 24 h at room temperature and dried at50 °C overnight, and the resulting BMN/sponge/As particleswere collected with a magnet. Subsequently, the remainingsandy soil and the AsĲIII) mixture were placed in 1 L deionizedwater, and the resulting system was shaken for 24 h to desorbAsĲIII) completely. Finally, the collected samples werecentrifuged (4500 rpm) for 5 min, and the concentration ofAsĲIII) in the supernatant was measured using atomic

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florescence spectroscopy (SA-20, Jitian Inc., Beijing, China).All experiments were performed in quintuplicate. The removalefficiency (REsandy soil) of AsĲIII) was calculated as follows:

REsandysoil t t

C V CVC V

0 0

0 0

100%, (5)

where C0 and Ct are the initial and resulting concentrations,respectively. V0 (50 mL) is the initial volume of AsĲIII) solution,and Vt (1 L) is the volume of added deionized water.

2.5.4 Pot incubation. In the experiment, the As-contaminated soil was obtained from a rice field (Fogang,Guangdong) and mixed with BMN at weight ratio of 3%. After3 days, the pH value of the soil was measured using areported method.36 In brief, 5 g soil was put in 25 mL deion-ized water. After being shaken for 24 h, the resulting systemwas centrifuged (4500 rpm) for 5 min, and then the pH valueof the supernatant was measured. The concentrations ofavailable arsenic in soil were determined as described in theprevious study with some modifications.21 In brief, 1.0 g soilwas added to polyethylene centrifugation tubes and thentreated with 25 mL NH4H2PO4 (0.05 M) solution in a 65 °Cwater bath with shaking at 120 rpm for 2 h. The mixture wasthen centrifuged at 2500 rpm for 5 min, and arsenic concen-tration in the supernatant was measured.

3. Results and discussion3.1 Characterization of BMN

The morphology of BMN was determined using SEM andTEM. As seen in Fig. 2A–E, BMN possessed a rough surfacecontaining round particles (Fig. 2A and B). Therein, theseround particles were nanosized with a high density (Fig. 2C).Through pyrolysis treatment, large number of iron nano-particles successfully was loaded onto the surface of BMN,which mainly was composed of iron oxides (maghemite andhematite). The diameter of nanoparticles was about 20 nm(Fig. 2E). Actually, FeĲIII) not only adhered onto the surfacebut also entered inside of BMN and then reacted with bio-mass to form iron oxides with a good dispersion, accordingto the previous study.37 The TEM image shows that BMN al-lows proper spread of iron nanoparticles, thereby, preventingaggregation (Fig. 2D). Meanwhile, composition of BMN wasdetected via elemental mapping and EDS spectroscopy. Asshown in Fig. 2G–I, C, O and Fe atoms are evenly distributedin the elemental maps of BMN. As seen in Fig. 2K, BMNmainly contains three elements: iron, carbon and oxygen,which is consistent with the above elemental mapping re-sults. Iron was the most abundant element on the surface ofBMN, and Cu came from the copper net used during the test.In addition, according to the previous study, the obtainedBMN is stable in water and soil due to strong mechanicalbonding between biomass and iron oxides.32 In light of its

Fig. 2 SEM images (A and B) and TEM images (C–E) of BMN; TEM image of BMN (F), merged image (G) of the distribution maps of C (H), O (I) andFe (J) in BMN; the EDX spectrum (K) of BMN; the effect of pH on zeta potential (L) of BMN.



excellent structural integrity, BMN is suitable as an adsorbentfor the removal of pollutants from water or soil.

The crystalline structure and composition of BMN andpure biochar were investigated by XRD. Two characteristicdiffraction peaks for C(002) and C(101) in the XRD pattern ofpure biochar indicated an amorphous carbon structure. Afterthe pretreatment with FeCl3, the weakening of characteristicpeaks of C(002) and C(101) was due to the enhancedamorphization of BMN during pyrolysis.38

Besides, a similar peak at around 28.5° was observed inXRD patterns of BMN and pure biochar, corresponding to syl-vite that often appears in biochar production from palmwaste.39 The peaks at 44.67° (110) and 65.02° (200) are thecharacteristic peaks of zero-valent iron, suggesting its pres-ence. Additionally, the peaks at 35.5° (311), 43.3° (440), and56.9° (511) are the characteristic peaks of maghemite, indi-cating its presence.40 The peaks at around 40.8 (113) and50.1° (024) are characteristic of hematite.41 Therefore, ironnanoparticles on BMN could contained maghemite, zero-valent iron and hematite.

Functional groups of BMN samples were also character-ized using FTIR analysis. Four typical absorption peaksaround 3439, 1225, 892, and 817 cm−1 can be observed in thespectrum of BMN (Fig. 3B). Also, a new peak around 892cm−1 can be seen in the BMN sample spectrum, which indi-cates that chemical bonds of FeO have appeared in thestructure of BMN.42,43 Meanwhile, the enhanced peak around817 cm−1 comes from the bending vibration of C–H in aro-matic ring, indicating that the presence of iron can enhancethe graphitization degree of biomass. Besides, the peaks at1225 and 1587 cm−1 appeared in the FTIR spectra of BMN, in-dicating that there are more C–O and CO functional groupson the surface of BMN. Therefore, introduction of iron al-tered the surface functional groups of the biomass afterpyrolysis.

The chemical states of BMN was investigated using XPSspectroscopy. The presence of elements Fe, O and C in BMNwas confirmed by XPS analysis with peaks appearing at 709,530 and 284 eV (Fig. 3C), which were attributed to Fe 2p, O1s and C 1s, respectively. Fig. 3D shows the Fe2p peaks atbinding energies of 711.3 and 724.4 eV, with a shakeup satel-lite at 718.2 eV. The dominant peak at 711.3 eV and the satel-lite signal at 718.2 eV can be attributed to Fe3+ and Fe2+, re-spectively. They can be assigned to Fe3+ and Fe2+ inmaghemite (γ-Fe2O3), indicating the presence of magnetismin BMN.44,45 The shoulder peak at 724.4 eV can be assignedto Fe in hematite (α-Fe2O3).

46 The characteristic peak of zero-valent iron at 706.1 eV was not obvious,47 suggesting thatzero-valent iron did not exist on the surface of BMN. The re-sults of XPS analysis were consistent with the results of XRDanalysis, indicating that iron nanoparticles consisted ofmaghemite, hematite, and zero-valent iron.

3.2 AsĲIII) removal by BMN

The removal of AsĲIII) by BMN from water was evaluated viaadsorption isotherms and kinetic experiments. In the adsorp-tion isotherms experiments, the effect of the initial pH valuesof AsĲIII) solutions on the adsorption capacity of BMN was in-vestigated. The pH-dependent adsorption capacity for BMNwas studied in the pH range of 4.0–9.0 (Fig. 4A). When thepH was increased from 4.0 to 9.0, the maximum AsĲIII) ad-sorption capacity of 16.23 mg g−1 was observed at pH 7.0,and AsĲIII) exists predominantly as H3AsO3. The minimumAsĲIII) adsorption capacity of 10.92 mg g−1 was observed at pH9.0, at which AsĲIII) exists predominantly as H2AsO3

−.48 BMNpossesses surface hydroxyl groups and plays an importantrole in the removal of AsĲIII), which can be protonated anddeprotonated in solution depending on the pH. The differ-ence in the adsorption capacities as a function of the solu-tion pH could be explained by the variation of zeta potentialwith the change in the surface charge of the BMN. As shownin Fig. 2L, negative zeta potentials were found for BMN attested pH. Therefore, an increase in the adsorption of AsĲIII)in neutral pH solution indicated that adsorption by BMN oc-curred via surface complexation rather than electrostaticinteraction. Additionally, the adsorption capacity of pure bio-char was significantly lower than that of BMN, and the maxi-mum capacity only reached about 2 mg g−1 without obviouschange at all tested pH values (ESI:† Fig. S1). In order tounderstand AsĲIII) adsorption behavior, Langmuir andFreundlich isotherms were analyzed. The two isotherms arerepresented as follow:

qe = QmaxbCe/(1 + bCe), Langmuir (6)

qe = KfC1/ne , Freundlich (7)

where Ce (mg L−1) is the equilibrium solution concentrationof the adsorbate. Qmax (mg g−1) is the maximum equilibriumconcentration of the adsorbate in the adsorbent; qe (mg g−1)

Fig. 3 (A) XRD analysis of BMN and the pure biochar; (B) FTIR spectraof BMN and the pure biochar; XPS spectra of the BMN: (C) survey, (D)Fe2p.



is the equilibrium concentration of the adsorbate in the ad-sorbent, b (L mg−1) and Kf (mg(1−1/n) L1/n g−1) represent theLangmuir bonding term related to interaction energies andthe Freundlich affinity coefficient, respectively; 1/n is a con-stant known as the heterogeneity factor that is related to thesurface heterogeneity. The adsorption constants obtainedfrom the isotherms at certain experimental conditions arelisted in Table S1.† According the results, the adsorption be-havior of AsĲIII) on BMN was mainly controlled by the Lang-muir surface adsorption mechanisms. These results are con-sistent with several published studies that describedadsorption behavior of AsĲIII) on iron oxides with the help oftwo models.49 It was suggested that AsĲIII) adsorption was

monolayer adsorption, which indicated that it mainly tookplace on surface of BMN without obvious interaction amongadsorption species.45 This could be due to the homogeneousdistribution of surface iron nanoparticles on BMN. In addi-tion, the adsorption capacity of AsĲIII) on BMN is higher thanthat of the reported adsorbents (Table 1).

Adsorption kinetics studies were conducted using differentinitial concentrations of AsĲIII) at pH 7.0. The results indicatedthat more than 23% of the AsĲIII) was removed within the first1 h (Fig. 4B). Then, a slow adsorption followed until the equi-librium was reached. This adsorption behavior of initial rapidadsorption and late slow adsorption was reported in otherstudies.50,51 Some complexes of AsĲIII) could be formed onboth outer- and inner-sphere surface of amorphous iron oxidevia ion exchange and electrostatic reaction.52 A similar reac-tion between BMN and AsĲIII) could occur because of the pres-ence of various valence iron atoms in BMN. Hence, the initialrapid adsorption process was attributed to electrostatic reac-tion and the formation of some complexes on the outer-sphere surface of iron nanoparticles, and the following slowadsorption process was due to the loss of outer-sphere activesites and the formation of complexes on inner-sphere surfaceof iron nanoparticles. In order to investigate the adsorptionmechanism of the removal process, the pseudo-second-orderkinetics model was used for the simulation of AsĲIII) adsorp-tion kinetics. Its linear forms are as follows:

tq k q

tq

1

22e e

, (8)

where q (mg g−1) is the concentration of the adsorbate in theadsorbent at time t (min) and k2 (g mg−1 min−1) is the pseudo-second-order adsorption rate constant. The equation summa-rizes the calculated qe values, pseudo-second-order rate con-stants k2, and correlation coefficient values (R2) (ESI:† TableS2). The adsorption kinetics follows the pseudo-second-ordermodel, indicating that the adsorption behavior of AsĲIII) onBMN is a combined process, which could include surfacechemical adsorption and the inner redox reaction. Therefore,the AsĲIII) adsorption on BMN should be a chemical process.Some similar results had been reported regarding removal ofarsenic by iron-based adsorbents.53

In addition, recyclability is one of the crucial aspects usedto evaluate adsorbent applicability. Reusability of BMN was

Fig. 4 (A): Adsorption isotherms of AsĲIII) on BMN at different pHvalues (pH = 4.0, 7.0 and 9.0); (B): time profile of AsĲIII) removal withBMN (BMN concentration was 2.0 g L−1; the initial AsĲIII) concentrationsranged from 5.0 to 20.0 mg L−1); (C) influence of the recycling andreusing of BMN on the removal efficiency; (D) XPS analysis of As3d inAsĲIII)-adsorbed BMN; (E) zeta potentials and oxidation reductionpotential of BMN in AsĲIII) solution under different pH conditions (AsĲIII)concentration: 10 mg L−1); (F) variation of H2O2 concentration duringthe process of BMN adsorbing AsĲIII) (AsĲIII) concentration: 10 mg L−1).

Table 1 Comparison of maximum AsĲIII) adsorption (Qmax) of different adsorbents

Adsorbents Qmax (mg g−1)

Experimental conditions

ReferenceInitial AsĲIII) concentration (mg L−1) Solution pH

Nanoscale zero-valent iron 3.50 0–1 7.0 57Chitosan resin 2.16 100 6.0 58Calcium-based magnetic biochar 6.34 0.5–20 6.0 59Magnetic kans grass biochar 2.00 0.4–0.8 7.0 60Goethite 10.10 0.66 7.5 61BMN nanocomposites 16.23 0–50 4.0–9.0 This study



also investigated using NaOH (0.1 M) solution. The results in-dicated that the removal efficiency of AsĲIII) by BMN de-creased from 91% (the third cycle) to 82% (the fourth cycle)(Fig. 4C), which may be due to a weakened oxidation and theloss of active sites.54 Even so, the removal efficiency of therecycled BMN was found to stay above 80% after 6 cycles.The removal efficiency remained about 80% in the followingthree cycles, which was attributed mainly to the reversibleand specific adsorption of AsĲIII) fraction to BMN surfacethrough a ligand exchange process. The adsorbed As couldbe desorbed from the surface of BMN via hydroxyl exchange.Besides, the AsĲV) was also found in solution (ESI:† Fig. S2).The concentration of AsĲV) distinctly decreased with the in-creasing cycle times, which could be due to the weakened oxi-dation. This result suggests that BMN has great potential forthe removal of AsĲIII) from aqueous phase in a cost-effectivemanner.

3.3 Removal of AsĲIII) from soil using BMN nanocomposite

Although BMN has excellent capacity of adsorption and mag-netism, it is still difficult to collect BMN/AsĲIII) particles fromthe soil suspension or sandy soil because of the strong forceexisting between BMN/AsĲIII) particles and the soil suspen-sion. In order to improve this separation, BMN particles wereloaded into a porous sponge (Fig. 5D). Then, the sponge wascut into small particles for better adsorption. After treatmentwith AsĲIII), the resulting BMN/sponge/AsĲIII) particles were col-lected by a magnet (Fig. 5B and C). The filter net could pre-vent the wet BMN/sponge/AsĲIII) particles from falling off themagnet. Fig. 5E shows that the removal efficiency increasedwith the increasing amount of BMN on sponge, and the max-imum removal efficiency reached 90% when the amount ofBMN on the sponge was 25 mg. Moreover, BMN/sponge parti-cles could significantly oxidize some of AsĲIII) to AsĲV)

(Fig. 5F). This method provides a promising approach to effi-ciently remove the AsĲIII) from the soil suspension.

Additionally, this method could be used to remove AsĲIII)from sandy soil. Seen from Fig. 6D, the removal efficiency in-creased with the amount of BMN on the sponge. The maxi-mum removal efficiency reached 75%. The BMN/sponge par-ticles could significantly oxidize some of AsĲIII) to AsĲV)(Fig. 6E). After treatment with AsĲIII), the resulting BMN/sponge/AsĲIII) particles were easily collected from the sandysoil by a magnet (Fig. 6A and B). In practice, this technologycould be applied in a field to remediate AsĲIII)-contaminatedsoil. The BMN/sponge mixture could be evenly dispersedthroughout the field, and then the soil could be mixed withthe BMN/sponge mixture by a rotary tiller to insure contact ofBMN/sponge with AsĲIII). After a certain time, a magnetic ro-tary tiller could be used to collect the BMN/sponge/AsĲIII) mix-ture (Fig. 6C).

In order to investigate the practical application of BMN,the pot incubations of remediating As-contaminated soil wereconducted. As shown in Table 2, BMN could slightly increasethe pH value of soil (from 4.7 to 4.9), probably because theformation of a complex between iron nanoparticles and arse-nic, which could facilitate the reduction of the number of H+

ions in soil.55,56 Besides, BMN significantly decreased theconcentration of available arsenic in soil (from 2.96 mg kg−1

to 1.85 mg kg−1), indicating that the bioavailability of arsenicin the soil was effectively reduced. The increased pH valueand the decreased concentration of available arsenic in soilindicated that BMN could remediate the As-contaminatedsoil in a short time.

Considering high concentration of AsĲIII) in some miningareas, it is important to control migration of AsĲIII) in soil.Here, we simulated a leaching system of AsĲIII) in soil byhome-made devices. BMN particles were loaded onto filterpaper. The obtained BMN paper was placed in the mixture ofsoil and sand (Fig. 7A).

Fig. 5 (A–C) Digital photographs of the magnetic collection process ofBMN/sponge/AsĲIII) particles from the soil suspension, with arrows (a–c)corresponding to the BMN/sponge/AsĲIII) particles, filter net, and themagnet, respectively; (D) digital photographs of the sponge and theBMN/sponge; (E) effect of the amount of BMN on removal efficiencyof AsĲIII) in the sand–soil mixture; (F) effect of the amount of BMN onthe concentrations of AsĲIII) and AsĲV) in soil suspension.

Fig. 6 (A and B) Digital photographs of the magnetic collectionprocess of BMN/sponge/AsĲIII) particles from the sandy soil; (C)schematic diagram of separation of BMN/sponge/AsĲIII) from the sandysoil; (D) effect of the amount of BMN on removal efficiency of AsĲIII) inthe sandy soil; (E) effect of the amount of BMN on the concentrationsof AsĲIII) and AsĲV) in sandy soil.



When AsĲIII) solution flowed through the BMN/paper, theAsĲIII) was adsorbed on the BMN/paper or oxidized to AsĲV),which reduced the amount of AsĲIII) in the soil–sand mixtureunder the BMN/paper. These results indicated that the re-moval efficiency of AsĲIII) increased from 18% to 90% withthe increasing amount of BMN on filter paper (Fig. 7B). Be-sides, the AsĲV) concentration in the leachate increased from0.56 mg L−1 to 2.98 mg L−1 (Fig. 7C), indicating that the oxi-dation capacity of BMN was enhanced with the increasingamount of BMN. For practical application, a relatively thickfilter paper, covered by BMN, could be placed into the soil ata depth of 15–20 cm, wherein the filter paper could be re-placed by the nylon net. After protecting the soil for a certainamount of time, BMN could be collected using a magnetic ro-tary tiller, protecting deep soil and underground water fromcontamination by AsĲIII).

3.4 AsĲIII) removal mechanisms

To further investigate the interactions between AsĲIII) andBMN after AsĲIII) uptake by BMN, arsenic speciation on BMNwas probed via XPS analysis. As shown in Fig. 4D, bindingenergies of 43.8, 44.8 and 45.5 eV, displayed in As3d spectraof BMN, corresponded to As–O bonds, As2O3 and As2O5, re-spectively, which indicated that both AsĲIII) and AsĲV) speciescoexisted on the surface of BMN.62,63 Therefore, it was con-cluded that partial oxidation of AsĲIII) to AsĲV) occurred duringthe adsorption process. The removal mechanism of AsĲIII) byBMN, illustrated in Fig. 8, may be described by three path-

ways. First, AsĲIII) is adsorbed on the surface of BMN. Duringthis process, AsĲIII) could be immobilized on the surface ofiron nanoparticles containing iron oxides. It has beenreported that AsĲIII) adsorption onto iron oxides generatedinner-sphere bidentate-mononuclear species.64–66 The possi-ble complexation reaction is as follows:

Fe(II,III)OH + H3AsO3 → Fe(II,III)H2AsO3 + H2O

Second, AsĲIII) is partially oxidized to AsĲV) by reactive oxy-gen. Some reports have demonstrated that the zero-valentiron could react with the dissolved oxygen in water to gener-ate reactive oxygen.67,68 XPS analysis (Fig. 3D) revealed thatBMN contained a small amount of zero-valent iron, whichcould convert soluble oxygen to reactive oxygen species.69

More importantly, FeĲII) could form a complex with AsĲIII),and oxidation of FeĲII)–AsĲIII) complex could promote genera-tion of reactive oxygen.70 Large amount of FeĲII) in the BMNcould promote the process of co-oxidation of AsĲIII) and FeĲII).The generated reactive oxygen could oxidize AsĲIII) to AsĲV).The maximum oxidation reduction potential of BMN wasfound at pH 7.0 with the highest adsorption capacity towardsAsĲIII) (Fig. 4E and ESI:† Table S1). In addition, the H2O2 con-centration decreased during the reaction of BMN and AsĲIII)(Fig. 4F), which could be ascribed to oxidation of AsĲIII). Bothhigh oxidation reduction potential and decreased H2O2 con-centration demonstrate that AsĲIII) in solution could be oxi-dized to AsĲV). Some possible reactions are described by thefollowing equations:

Fe(0) + O2 + 2H+ → Fe3+ + ˙OH + OH−

H3AsO3 + 2˙OH → H3AsO4 + H2O

Fe H AsO O Fe H AsOII III II III, , 2 3 2 2 412

Fe(II,III)OH + H3AsO4 → Fe(II,III)H2AsO4 + H2O

Finally, the generated AsĲV) could be easily adsorbed ontoiron oxide nanoparticles of BMN.64 The three pathways couldactually be summarized as simultaneous oxidation and

Table 2 The effect of BMN on pH and available arsenic content in soil

Treatments CK BMN (3%)

pH 4.7 ± 0.1 4.9 ± 0.1Available arsenic concentration (mg kg−1) 3.0 ± 0.2 1.9 ± 0.1

Fig. 7 (A) Schematic diagram of the leaching system; (B) effect of theamount of BMN on different concentrations of AsĲIII) and AsĲV); (C)effect of the amount of BMN on the removal efficiency of AsĲIII) fromthe sand–soil mixture.

Fig. 8 Schematic illustration of AsĲIII) removal mechanism using BMN.



immobilization of AsĲIII) with the addition of BMN, wherein,oxidation of AsĲIII) was a key pathway in the removal of AsĲIII)from soil. The immobilization of AsĲIII) and AsĲV) by BMNcould reduce the content of arsenic in soil.

The electrostatic attraction between arsenic and BMN wasalso an important factor. Besides, the surface carbon func-tional groups of BMN could play an important role in the ad-sorption of arsenic. Because iron could increase the contentof CO/O–CO (Fig. 3B), these functional groups could en-hance the adsorption of arsenic.32 More characterization andtesting experiments are still needed to prove the above re-moval mechanism of AsĲIII).

4. Conclusion

In this work, a novel biomass-derived magnetic nano-composite (BMN) was successfully fabricated via a simple py-rolysis process of palm waste treated with FeCl3. Our resultsshowed that BMN possessed excellent AsĲIII) removal capabil-ity with high adsorption capacity, magnetism, reusability andlow cost. Importantly, in order to improve the BMN absorp-tion of AsĲIII), BMN can be supported by sponges and filterpaper, which could efficiently remove AsĲIII) from soil andcontrol the migration of AsĲIII) in soil. Meanwhile, the BMN/As/sponge mixture could be collected and separated by amagnet. Magnetic BMN was successfully used for remedia-tion of As-contaminated paddy soil by increasing the pH ofsoil and decreasing the concentration of available arsenic insoil. The removal of AsĲIII) was realized via simultaneous oxi-dation and immobilization of AsĲIII). Therefore, the existenceof Fe(0) and FeĲII) nanoparticles in BMN could promote gen-eration of reactive oxygen and enhance immobilization ofAsĲIII). In summary, this study provides a promising approachto remediate the As-contaminated soil.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was financially supported by National Natural Sci-ence Foundation of China (No. 41877137 and 41420104007),National Key Research and Development Project of China(No. 2016YFD0800700), Science and Technology Planning Pro-ject of Guangdong Province, China (No. 2017A070702015 and2017B030314092), Science and Technology Planning Projectof Guangzhou (201604020039), and Scientific Platform andInnovation Capability Construction Program of GuangdongAcademy of Science (No. 2017GDASCX-0404, 2017GDASCX-0106 and 2016GDASRC-0103).

References

1 L. Zhou, G. Zhang, J. Tian, D. Wang, D. Cai and Z. Wu,Functionalized Fe3O4@C nanospheres with adjustable

structure for efficient hexavalent chromium removal, ACSSustainable Chem. Eng., 2017, 5, 11042–11050.

2 C. Chang, H. Yu, J. Chen, F. Li, H. Zhang and C. Liu,Accumulation of heavy metals in leaf vegetables fromagricultural soils and associated potential health risks in thePearl River Delta, South China, Environ. Monit. Assess.,2014, 186, 1547.

3 S. Bhattacharya and U. C. Ghosh, Environmental, economicand health perspectives of arsenic toxicity in Bengal Delta,World Sci. News, 2015, 10, 111–139.

4 H. Feng, L. Tang, J. Tang, G. Zeng, H. Dong, Y. Deng, L.Wang, Y. Liu, X. Ren and Y. Zhou, Cu-doped Fe@Fe2O3 core-shell nanoparticles shifted oxygen reduction pathway forhigh-efficiency arsenic removal in smelting wastewater, Envi-ron. Sci.: Nano, 2018, 5, 1595–1607.

5 Z. Cheng, F. Fu, D. D. Dionysiou and B. Tang, Adsorption,oxidation, and reduction behavior of arsenic in the removalof aqueous As(III) by mesoporous Fe/Al bimetallic particles,Water Res., 2016, 96, 22–31.

6 D. Ghosh, S. Sarkar, A. K. Sengupta and A. Gupta,Investigation on the long-term storage and fate of arsenicobtained as a treatment residual: a case study, J. Hazard.Mater., 2014, 271, 302–310.

7 J. Zhang, S. Zhao, Y. Xu, W. Zhou, K. Huang, Z. Tang and F. J.Zhao, Nitrate stimulates anaerobic microbial arsenite oxidationin paddy soils, Environ. Sci. Technol., 2017, 51, 4377–4386.

8 J. Li, L. Wang, J. Cui, C. Poon, J. Beiyuan, D. Tsang and X.Li, Effects of low-alkalinity binders on stabilization/solidifi-cation of geogenic As-containing soils: Spectroscopic investi-gation and leaching tests, Sci. Total Environ., 2018, 631-632,1486–1494.

9 N. Balasubramanian, T. Kojima and C. Srinivasakannan,Arsenic removal through electrocoagulation: kinetic andstatistical modeling, Chem. Eng. J., 2009, 155, 76–82.

10 J. Beiyuan, J. Li, T. Dcw, L. Wang, C. Poon, X. Li and S.Fendorf, Fate of arsenic before and after chemical-enhancedwashing of an arsenic-containing soil in Hong Kong, Sci.Total Environ., 2017, 599–600, 679–688.

11 P. Zeng, Z. Guo, X. Xiao, C. Peng, W. Feng, L. Xin and Z. Xu,Phytoextraction potential of Pteris vittata L. co-planted withwoody species for As, Cd, Pb and Zn in contaminated soil,Sci. Total Environ., 2019, 650, 594–603.

12 M. A. Limmer, P. Wise, G. E. Dykes and A. L. Seyfferth,Silicon decreases dimethylarsinic acid concentration in ricegrain and mitigates straighthead disorder, Environ. Sci.Technol., 2018, 52, 4809–4816.

13 J. Kumpiene, A. Lagerkvist and C. Maurice, Stabilization ofAs, Cr, Cu, Pb and Zn in soil using amendments-a review,Waste Manage., 2008, 28, 215–225.

14 D. H. Moon, D. Dermatas and N. Menounou, Arsenicimmobilization by calcium-arsenic precipitates in limetreated soils, Sci. Total Environ., 2004, 330, 171–185.

15 C. Deng, J. Wen, Z. Li, N. Luo, M. Huang and R. Yang,Passivating effect of dehydrated sludge and sepiolite onarsenic contaminated soil, Ecotoxicol. Environ. Saf.,2018, 164, 270–276.



16 Y. Wei, H. Liu, C. Liu, S. Luo, Y. Liu, X. Yu, J. Ma, K. Yin andH. Feng, Fast and efficient removal of As(III) from water byCuFe2O4 with peroxymonosulfate: Effects of oxidation andadsorption, Water Res., 2019, 150, 182–190.

17 Y. Wei, C. Liu, S. Luo, J. Ma, Y. Zhang, H. Feng, K. Yin andQ. He, Deep oxidation and removal of arsenite ingroundwater by rationally positioning oxidation andadsorption sites in binary Fe-Cu oxide/TiO2, Chem. Eng. J.,2018, 354, 825–834.

18 M. Komarek, A. Vanek and V. Ettler, Chemical stabilizationof metals and arsenic in contaminated soils using oxides–areview, Environ. Pollut., 2013, 172, 9–22.

19 D. Wang, Z. Dai, X. Shu, P. Bian, L. Wu, D. Cai and Z. Wu,Functionalized nanocomposite for simultaneous removal ofantibiotics and As(III) in swine urine aqueous solution andsoil, Environ. Sci.: Nano, 2018, 5, 2978–2992.

20 D. Chen, T. Liu, X. Li, F. Li, X. Luo, Y. Wu and Y. Wang,Biological and chemical processes of microbially mediatednitrate-reducing Fe(II) oxidation by Pseudogulbenkiania sp.strain 2002, Chem. Geol., 2018, 476, 59–69.

21 H. Yu, X. Wang, F. Li, B. Li, C. Liu, Q. Wang and J. Lei,Arsenic mobility and bioavailability in paddy soil under ironcompound amendments at different growth stages of rice,Environ. Pollut., 2017, 224, 136–147.

22 C. Liu, H. Yu, C. Liu, F. Li, X. Xu and Q. Wang, Arsenicavailability in rice from a mining area: Is amorphous ironoxide-bound arsenic a source or sink ?, Environ. Pollut.,2015, 199, 95–101.

23 L. Tian, Z. Shi, L. Yang, A. C. Dohnalkova, L. Zhang and D.Zhi, Kinetics of cation and oxyanion adsorption anddesorption on ferrihydrite: roles of ferrihydrite binding sitesand a unified model, Environ. Sci. Technol., 2017, 51,10605–10614.

24 M. Saif, S. M. K. Aboul-Fotouh, S. A. El-Molla, M. M. Ibrahimand L. F. M. Ismail, Nanotechnology for SustainableDevelopment, J. Nanopart. Res., 2014, 15, 149–158.

25 J. Kumpiene, S. Ore, G. Renella, M. Mench, A. Lagerkvistand C. Maurice, Assessment of zerovalent iron forstabilization of chromium, copper, and arsenic in soil,Environ. Pollut., 2006, 144, 62–69.

26 H. J. Shipley, K. E. Engates and A. M. Guettner, Study of ironoxide nanoparticles in soil for remediation of arsenic,J. Nanopart. Res., 2011, 13, 2387–2397.

27 S. Wan, J. Wu, S. Zhou, R. Wang, B. Gao and F. He,Enhanced lead and cadmium removal using biochar-supported hydrated manganese oxide (HMO) nanoparticles:Behavior and mechanism, Sci. Total Environ., 2018, 616,1298–1306.

28 W. Kwapinski, C. M. P. Byrne, E. Kryachko, P. Wolfram, C.Adley, J. J. Leahy, E. H. Novotny and M. H. B. Hayes, Biocharfrom Biomass and Waste, Waste Biomass Valoriz., 2010, 1,177–189.

29 M. Ahmad, A. U. Rajapaksha, J. E. Lim, Z. Ming, N. Bolan, D.Mohan, M. Vithanage, S. L. Sang and S. O. Yong, Biochar asa sorbent for contaminant management in soil and water: Areview, Chemosphere, 2014, 99, 19–33.

30 J. Qiao, X. Li, M. Hu, F. Li, L. Young, W. Sun, W. Huang andJ. Cui, Transcriptional activity of arsenic-reducing bacteriaand genes regulated by lactate and biochar during arsenictransformation in flooded paddy soil, Environ. Sci. Technol.,2017, 52, 61–70.

31 J. Qiao, X. Li and F. Li, Roles of different active metal-reducing bacteria in arsenic release from arsenic-contaminated paddy soil amended with biochar, J. Hazard.Mater., 2017, 344, 958–967.

32 X. Hu, Z. Ding, A. R. Zimmerman, S. Wang and B. Gao,Batch and column sorption of arsenic onto iron-impregnated biochar synthesized through hydrolysis, WaterRes., 2015, 68, 206–216.

33 N. K. Niazi, I. Bibi, M. Shahid, Y. S. Ok, E. D. Burton, H.Wang, S. M. Shaheen, J. Rinklebe and A. Luttge, Arsenicremoval by perilla leaf biochar in aqueous solutions andgroundwater: An integrated spectroscopic and microscopicexamination, Environ. Pollut., 2018, 232, 31–41.

34 Z. Yang, C. Shan, Y. Mei, Z. Jiang, X. Guan and B. Pan,Improving reductive performance of zero valent iron byH2O2 /HCl pretreatment: A case study on nitrate reduction,Chem. Eng. J., 2018, 334, 2255–2263.

35 E. Garciaordiales, S. Covelli, J. M. Rico, N. Roqueñí, G.Fontolan, G. Florblanco, P. Cienfuegos and J. Loredo,Occurrence and speciation of arsenic and mercury inestuarine sediments affected by mining activities (Asturias,northern Spain), Chemosphere, 2018, 198, 281–289.

36 D. Wang, W. Guo, G. Zhang, L. Zhou, M. Wang, Y. Lu, D.Cai and Z. Wu, Remediation of CrĲVI)-contaminated acid soilusing a nanocomposite, ACS Sustainable Chem. Eng., 2017, 5,2246–2254.

37 R. He, Z. Peng, H. Lyu, H. Huang, Q. Nan and J. Tang,Synthesis and characterization of an iron-impregnated bio-char for aqueous arsenic removal, Sci. Total Environ.,2018, 612, 1177–1186.

38 J. Yu, A. M. Dehkhoda and N. Ellis, Development of Biochar-based Catalyst for Transesterification of Canola Oil, EnergyFuels, 2011, 25, 337–344.

39 A. R. A. Usman, A. Abduljabbar, M. Vithanage, Y. S. Ok, M.Ahmad, M. Ahmad, J. Elfaki, S. S. Abdulazeem and M. I. Al-Wabel, Biochar production from date palm waste: Charringtemperature induced changes in composition and surfacechemistry, J. Anal. Appl. Pyrolysis, 2015, 115, 392–400.

40 Z. Li, L. Wang, J. Meng, X. Liu, J. Xu, F. Wang and P.Brookes, Zeolite-supported nanoscale zero-valent iron: Newfindings on simultaneous adsorption of Cd(II), Pb(II), andAs(III) in aqueous solution and soil, J. Hazard. Mater.,2017, 344, 1–11.

41 X. Cui, T. Liu, Z. Zhang, L. Wang, S. Zuo and W. Zhu,Hematite nanorods with tunable porous structure: Facilehydrothermal-calcination route synthesis, optical and photo-catalytic properties, Powder Technol., 2014, 266, 113–119.

42 X. Feng, N. Dementev, W. Feng, R. Vidic and E. Borguet,Detection of low concentration oxygen containing functionalgroups on activated carbon fiber surfaces throughfluorescent labeling, Carbon, 2006, 44, 1203–1209.



43 Y. Lin, S. Xu and J. Li, Fast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particles, Chem. Eng. J., 2013, 225,679–685.

44 X. Zhu, Y. Liu, F. Qian, C. Zhou, S. Zhang and J. Chen,Preparation of magnetic porous carbon from wastehydrochar by simultaneous activation and magnetization fortetracycline removal, Bioresour. Technol., 2014, 154, 209–214.

45 Y. Chen, S. Ho, D. Wang, Z. Wei, J. Chang and N. Ren, Leadremoval by a magnetic biochar derived from persulfate-ZVItreated sludge together with one-pot pyrolysis, Bioresour.Technol., 2018, 247, 463–470.

46 A. P. Grosvenor, B. A. Kobe, M. C. Biesinger and N. S.Mcintyre, Investigation of multiplet splitting of Fe2p XPSspectra and bonding in iron compounds, Surf. InterfaceAnal., 2004, 36, 1564–1574.

47 Y. Mu, H. Wu and Z. Ai, Negative impact of oxygenmolecular activation on Cr (VI) removal with core-shellFe@Fe2O3 nanowires, J. Hazard. Mater., 2015, 298, 1–10.

48 S. Venkateswarlu, D. Lee and M. Yoon, Bioinspired 2D-carbon flakes and Fe3O4 nanoparticles composite for arse-nite removal, ACS Appl. Mater. Interfaces, 2016, 8,23876–23885.

49 M. Zhang, B. Gao, S. Varnoosfaderani, A. Hebard, Y. Yao andM. Inyang, Preparation and characterization of a novelmagnetic biochar for arsenic removal, Bioresour. Technol.,2013, 130, 457–462.

50 P. D. Nemade, A. M. Kadam and H. S. Shankar, Adsorptionof arsenic from aqueous solution on naturally available redsoil, J. Environ. Biol., 2009, 30, 499–504.

51 H. D. Ozsoy and H. Kumbur, Adsorption of Cu(II) ions oncotton boll, J. Hazard. Mater., 2006, 136, 911–916.

52 S. Goldberg and C. T. Johnston, Mechanism of arsenicadsorption on amorphous oxides evaluated usingmacroscopic measurements, vibrational spectroscopy, andsurface complexation modeling, J. Appl. Polym. Sci.,2001, 234, 204–216.

53 F. Meng, B. Yang, B. Wang, S. Duan, Z. Chen and W. Ma,Novel dendrimerlike magnetic biosorbent based onmodified orange peel waste: adsorption-reduction behaviorof arsenic, ACS Sustainable Chem. Eng., 2017, 5, 9692–9700.

54 S. Wang, Y. Tang, C. Chen, J. Wu, Z. Huang, Y. Mo, K.Zhang and J. Chen, Regeneration of magnetic biocharderived from eucalyptus leaf residue for lead(II) removal,Bioresour. Technol., 2015, 186, 360–364.

55 C. Lee and D. L. Sedlak, Enhanced formation of oxidantsfrom bimetallic nickel-iron nanoparticles in the presence ofoxygen, Environ. Sci. Technol., 2008, 42, 8528–8533.

56 S. Pang, J. Jiang and J. Ma, Oxidation of sulfoxides andarsenic (III) in corrosion of nanoscale zero valent iron byoxygen: evidence against ferryl ions (Fe (IV)) as active

intermediates in Fenton reaction, Environ. Sci. Technol.,2010, 45, 307–312.

57 S. R. Kanel, B. Manning, L. Charlet and H. Choi, Removal ofarsenicĲIII) from groundwater by nanoscale zero-valent iron,Environ. Sci. Technol., 2005, 39, 1291–1298.

58 B. Liu, X. Lv, D. Wang, Y. Xu, L. Zhang and Y. Li, Adsorptionbehavior of As(III) onto chitosan resin with As(III) astemplate ions, J. Appl. Polym. Sci., 2012, 125, 246–253.

59 J. Wu, D. Huang, X. Liu, J. Meng, C. Tang and J. Xu,Remediation of As(III) and Cd(II) co-contamination and itsmechanism in aqueous systems by a novel calcium-basedmagnetic biochar, J. Hazard. Mater., 2018, 348, 10–19.

60 S. A. Baig, J. Zhu, N. Muhammad, T. Sheng and X. Xu, Effectof synthesis methods on magnetic Kans grass biochar forenhanced As(III, V) adsorption from aqueous solutions,Biomass Bioenergy, 2014, 71, 299–310.

61 J. Giménez, M. Martínez, P. J. De, M. Rovira and L. Duro,Arsenic sorption onto natural hematite, magnetite, andgoethite, J. Hazard. Mater., 2007, 141, 575–580.

62 S. Bang, M. D. Johnson, G. P. Korfiatis and X. Meng,Chemical reactions between arsenic and zero-valent iron inwater, Water Res., 2005, 39, 763–770.

63 T. D. Çiftçi and E. Henden, Nickel/nickel boridenanoparticles coated resin: A novel adsorbent for arsenicĲIII)and arsenic(V) removal, Powder Technol., 2015, 269, 470–480.

64 X. Zhang, M. Wu, H. Dong, H. Li and B. C. Pan,Simultaneous oxidation and sequestration of As(III) fromwater by using redox polymer-based Fe(III) oxide nano-composite, Environ. Sci. Technol., 2017, 51, 6326–6334.

65 T. D. Sowers, J. M. Harrington, M. L. Polizzotto and O. W.Duckworth, Sorption of arsenic to biogenic iron (oxyhydr)oxides produced in circumneutral environments, Geochim.Cosmochim. Acta, 2017, 198, 194–207.

66 Y. Zhu and E. J. Elzinga, Macroscopic and spectroscopicassessment of the co-sorption of Fe(II) with As(III) and As(V)on Al-oxide, Environ. Sci. Technol., 2015, 49, 13369–13377.

67 Z. Zhao, Y. Jia, L. Xu and S. Zhao, Adsorption andheterogeneous oxidation of As(III) on ferrihydrite, WaterRes., 2011, 45, 6496–6504.

68 S. Bakshi, C. Banik, S. J. Rathke and D. A. Laird, Arsenicsorption on zero-valent iron-biochar complexes, Water Res.,2018, 137, 153.

69 C. Wu, J. Tu, W. Liu, J. Zhang, S. Chu, G. Lu, Z. Lin and Z.Dang, The double influence mechanism of pH on arsenicremoval by nano zero valent iron: electrostatic interactionsand the corrosion of Fe0, Environ. Sci.: Nano, 2017, 4,1544–1552.

70 W. Ding, J. Xu, T. Chen, C. Liu, J. Li and F. Wu, Co-oxidationof As(III) and Fe(II) by oxygen through complexationbetween As(III) and FeĲII)/FeĲIII) species, Water Res.,2018, 143, 599–607.


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Environmental Science Nano - soil-interface.cn · soil using a magnet. In addition, when BMN was loaded on filter paper, the system of BMN and filter paper could be conveniently used