Arsenic (V) adsorption from aqueous solution onto

0 downloads 29 Views 714KB Size Report
Aug 17, 2011 - arsenate adsorption is related to the iron content of adsorbents, and ..... P.H. Emmett, E. Teller, Adsorption of gases in multimolecular layers, J.

Desalination 281 (2011) 93–99

Contents lists available at ScienceDirect

Desalination j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / d e s a l

Arsenic (V) adsorption from aqueous solution onto goethite, hematite, magnetite and zero-valent iron: Effects of pH, concentration and reversibility Yannick Mamindy-Pajany a, b,⁎, Charlotte Hurel a, Nicolas Marmier a, Michèle Roméo b a b

University of Nice Sophia Antipolis, Laboratoire de Radiochimie, Sciences Analytiques et Environnement (LRSAE), Faculty of Sciences, Parc Valrose, 06108 Nice Cedex 02, France University of Nice Sophia-Antipolis, Laboratoire des Ecosystèmes marins côtiers et réponses aux stress (ECOMERS/EA 4228), Faculty of Sciences, Parc Valrose, 06108 Nice Cedex 02, France

a r t i c l e

i n f o

Article history: Received 1 April 2011 Received in revised form 20 July 2011 Accepted 21 July 2011 Available online 17 August 2011 Keywords: Arsenic Adsorption Desorption Iron oxides Zero-valent iron Batch experiments

a b s t r a c t In this paper, adsorption of arsenic (V) was studied under different physico-chemical conditions onto four commercial adsorbents: hematite, goethite, magnetite and zero-valent iron (ZVI). The reversibility of adsorption process was also studied using chlorides and phosphates as competing ions. Results show that arsenate adsorption is related to the iron content of adsorbents, and adsorption rate increases in the following order: goethite b hematite b magnetite b ZVI. The modeling of adsorption isotherms by empirical models show that arsenate adsorption is fitted by the Langmuir model for almost all adsorbents, suggesting a monolayer adsorption of arsenic onto adsorbents. Desorption experiments show that arsenic is strongly adsorbed onto hematite and ZVI. Among adsorbents, hematite appears to be the most suitable for removing arsenate in natural medium since it is effective over large ranges of pH and arsenic concentration. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Arsenic is widely distributed in aquatic ecosystems due to the release from As-enriched minerals and anthropogenic sources including mining and smelting, industrial processes, and agricultural practices. Recent studies have shown that arsenic concentrations in port sediments are higher than recommended level (N50 mg/kg of dried sediment) in Mediterranean region such as Marseilles, Toulon, Cannes [1–3]. Dredging activities from this region can provide large amount of As-contaminated sediments that must be treated before storage in terrestrial disposal site. Within the framework of dredged sediment management, a French expert group proposed sediment quality guidelines (N1 and N2) for arsenic and metals in marine sediments [4]. Below the level N1, the ecological impact is view as negligible. Between N1 and N2, chemical analyses must be supplemented with toxicity tests. When their contamination level is higher than N2, dredged sediments cannot be discharged into the sea and must be treated or stored on terrestrial environment. The terrestrial management of contaminated sediments is a significant issue since the storage or beneficial reuse requires stabilization treatment and risk assessment for environment (contaminants should not be

⁎ Corresponding author at: University of Nice Sophia Antipolis, Laboratoire de Radiochimie, Sciences Analytiques et Environnement (LRSAE), Faculty of Sciences, Parc Valrose, 06108 Nice Cedex 02, France. Tel.: + 33 4 92 07 63 70; fax: + 33 4 92 07 63 64. E-mail address: [email protected] (Y. Mamindy-Pajany). 0011-9164/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2011.07.046

leached in the biosphere). According to Hopenhayn [5], arsenic is probably the contaminant that induces the highest risk of morbidity and mortality worldwide, due to its toxicity level and the number of exposed people. For example chronic toxicity due to drinking arsenic contaminated water has been one of the worst environmental health hazards for several countries like Bangladesh, Taiwan, India, Canada, USA and China [6]. The storage of contaminated sediments can release arsenic in surface or subsurface waters and provoke toxic effects on living organisms [7]. In this context, it is necessary to provide treatment techniques that are technically effective and economically feasible for immobilizing contaminants in sediments [8]. The aim of immobilization technique is to reduce pollutant mobility by adding a stabilization agent [9]. As an example, the Solvay Company patented a treatment using phosphoric acid to form apatite in contaminated sediments to immobilize pollutants. Although this technique can stabilize several metals [10], it increases leaching of anionic pollutants such as As, Cr (VI) and Mo [11]. Arsenic stabilization has been well studied in soil remediation and the most studied amendments are oxides of Fe and to a lesser extent Al and Mn. Zero-valent iron has been widely studied since Fe (0) oxidizes in soil, forming poorly crystalline Fe hydroxides that reduce the mobility of As by formation of amorphous FeAsO4.H2O and/or soluble secondary oxidation minerals such as scorodite (FeAsO4.2H2O). Arsenic occurs mainly as As (III) and As (V) in fresh port sediments [3,11], however, As (V) is the major chemical form in oxidized sediments [11]. In this paper, arsenate adsorption onto ironbased minerals was studied since these materials have shown interesting properties like adsorbents for arsenic [12–14]. The

94

Y. Mamindy-Pajany et al. / Desalination 281 (2011) 93–99

were measured under the same experimental conditions for all minerals using an apparatus Coulter SA 3100 [16]. For iron oxy-hydroxides, the surface charge occurs by direct proton transfer, since the surface hydroxyl group (≡SOH) is amphoteric. Surface ionization (protonation and deprotonation) reactions can be formulated as follows:

Table 1 The main physico-chemical properties of studied adsorbents. Mineral additives

Hematite

Goethite

Zero-valent iron

Magnetite

Supplier D50 (μm) Specific area (m2/g) pKa1 pKa2 pHZPC

Johnson Matthey 53 1.66 ± 0.02 6.38 9.81 8.1

Aldrich 10 11.61 ± 0.19 5.69 8.12 6.9

Fluka 17 0.20 ± 0.03 – – –

Alfa Aesar – 1.60 ± 0.01 4.60 8.20 6.40

þ

þ

≡SOH2 ↔≡SOH þ H Ka1 

þ

≡SOH↔≡SO þ H Ka2

behavior of As (V) onto four mineral adsorbents containing iron (hematite, goethite, magnetite and zero-valent iron) has been studied as a function of pH, arsenic concentration and reversibility effects of chlorides and phosphates to select the most appropriate mineral adsorbent for stabilization of arsenic in contaminated sediments. 2. Experimental section

Potentiometric titrations, at constant ionic strength (0.1 M NaNO3), were performed with hematite, goethite and magnetite to calculate acidity constants and the point of zero charge (pHZPC) [17]. Experiments were carried out using titration techniques described in previous works [18,19]. A computer program (FITEQL) was used to determine chemical equilibrium constants from experimental data. The point of zero charge (pHZPC) is the average of pKa1 and pKa2. The protonation of mineral surface is enhanced at pH lower than pHZPC (positive surface charge), while deprotonation is promoted at pH greater than pHZPC (negative surface charge).

2.1. Materials 2.2. Adsorption experiments

A

120

B 120

100

% As(V) adsorbed

Adsorption experiments were carried out at room temperature in polypropylene tubes (50 mL). A constant mass of solid (0.2 g) was put in contact with 50 cm 3 of arsenate solution at 100 μg L − 1 or 500 μg L − 1. The arsenate As (V) stock solution was prepared by dissolving Na2HAsO4. 7 H2O (Fluka). NaNO3 (0.01 M) was used as background electrolyte. The pH of suspensions was adjusted between 2 and 12 using HNO3 or NaOH (0.01 M). The pH values were measured by WTW pH meter using a combined pH electrode. Calibration was performed with two buffer solutions (pH 4.01 and pH 7.00) at room temperature. Suspensions were elliptically shaken until the adsorption equilibrium is reached [20]. After that, suspensions were centrifuged and filtered through 0.45 μm pore size filters. Acidified supernatants were analyzed for total arsenic concentration using inductively coupled plasma-mass spectrometry (ICP-MS–Elan DRC II–

% As(V) adsorbed

Sorption experiments were conducted with four commercial mineral adsorbents: hematite (Fe2O3), goethite (FeOOH), zero-valent iron (Fe) and magnetite (Fe3O4). The main physico-chemical properties (particle size, specific surface area and acid-base surface acidity constants) of adsorbents are displayed in Table 1. The size of particles (for hematite, goethite and zero-valent iron) was characterized by measuring the average particle diameter (D50 in micrometer) in aqueous suspension with a laser particle sizer Mastersizer 2000 (Malvern). The laser particle size gives the radii of particles between 0.05 and 900 μm with an accuracy of 1% on D50 value. Specific surface area was measured by N2 adsorption onto minerals using BET method developed by Brunauer, Emmett and Teller [15]. After degassing under vacuum at 60 °C, the amount of adsorbed N2 is determined at constant temperature (77 K). Specific surface areas

80 60 40 500 µg/L 20 0

100 µg/L 0

2

4

6

8

10

12

100 80 60 40

0

14

500 µg/L

20

100 µg/L 0

2

4

6

120

D 120

100

100

% As(V) adsorbed

C

80 60 40 500 µg/L 20 0

4

6

8

pH

10

12

14

8

10

12

14

80 60 40 500 µg/L 20

100 µg/L

100 µg/L 2

8

pH

% As(V) adsorbed

pH

10

12

14

0

0

2

4

6

pH

Fig. 1. Adsorption of As(V) onto hematite (A), goethite (B), zero-valent iron (C) and magnetite (D) as a function of pH at two initial concentrations: 100 and 500 μg As(V) /L. Experimental conditions: I = 0.01 M NaNO3, adsorbent concentration: 4 g/L.

[As]0 [As]

Concentration introduced initially Concentration remaining in aqueous solution after adsorption equilibrium

2.3. Adsorption isotherms Adsorption isotherms were performed at pH 6 and room temperature (25 °C) in NaNO3 0.01 M as background electrolyte. In the experiments, a constant mass of solid (0.2 g) was mixed with 50 mL solutions containing As (V) concentrations in the range of 1–200 μmol/ L. Suspensions were shaken until adsorption equilibrium was reached. After that, samples were centrifuged, filtered through 0.45 μm pore size acetate filters, acidified, and analyzed for arsenic concentrations remaining in solution. Among the empirical models, Langmuir and Freunlich models are the most used to describe the adsorption isotherms. These representations allow calculating thermodynamic values induced by the adsorption process. Arsenate adsorption was modeled with Langmuir adsorption isotherm using the following equation:   ½A  ½A  1 = + Γ Γ max Γ max × Kads where, Γ is the amount of adsorbate per unit of surface area (μmol/ m 2), [A] is the concentration of adsorbate (μmol/L) in the solution after equilibrium, Γmax (μmol/m 2) is the maximum adsorption density and Kads (mol/L) is the equilibrium constant for the overall adsorption process. The Freundlich relationship was also used to model arsenic adsorption by reporting log Γ versus log [A] according to the following equation: Γ = KF × [A] n Where KF is the Freundlich constant, and n represents the degree of nonlinearity in the relationship between Γ and [A]. 2.4. Reversibility experiments with MgCl2 and Na2HPO4 Reversibility of As (V) adsorption onto mineral adsorbents was studied using MgCl2 (0.01 M) and Na2HPO4 (0.001 M). These chemicals are usually used in the selective metal extraction protocols to evaluate

95

30

8

6 20 4 10 2

0

0

40

80

120

160

200

µmol/m2 for zero-valent iron

Perkin Elmer). The amount of As (V) adsorbed was calculated by subtracting final concentration in aqueous solution to the initial arsenic concentration. The adsorbed percentage was calculated as follows:  ½As0 −½As % As adsorbed = × 100 ½As0

µmol/m2 for hematite, goethite and magnetite

Y. Mamindy-Pajany et al. / Desalination 281 (2011) 93–99

0

[As(V)] µmol/L hematite

goethite

magnetite

zero-valent iron

Fig. 3. Adsorption isotherms of As (V) onto hematite, goethite, zero-valent iron and magnetite. Experimental conditions: I = 0.01 M NaNO3, pH = 6, adsorbent concentration: 4 g/L.

exchangeable (with MgCl2) [21] and strongly adsorbed (with Na2HPO4) fractions [22]. After adsorption experiments, described in Section 2.3, saturated adsorbents were re-suspended successively with MgCl2 and Na2HPO4 for 24 h. The pH of MgCl2 and Na2HPO4 solutions was set at 6 by adding HNO3 or NaOH. After each desorption step, suspensions were centrifuged and filtered through 0.45 μm pore size acetate filters. Total arsenic concentrations were analyzed in acidified supernatants to determine the amount of As (V) desorbed. 3. Results and discussion 3.1. Effects of pH on arsenic adsorption Arsenate adsorption onto hematite, goethite, magnetite and zerovalent iron (ZVI) was studied as a function of pH at initial concentration of 100 μg As (V) L − 1 (Fig. 1). Arsenate adsorption rate onto hematite reaches 100% in the pH range 2–11 and decreases until 50% above pH 11. For other adsorbents, amount adsorbed arsenate is equal to 100% for pH ranging from 2 to 8. When pH is higher than 8, the percentage of adsorbed arsenate decreases until 20%. These results are in good agreement with literature since they show that As (V) adsorption is pH dependent [20,23–25]. The pH dependence of As (V) adsorption is usually explained in terms of ionization of both adsorbates and adsorbents. According to aqueous arsenate speciation (Fig. 2), negatively charged species (H2AsO4- , HAsO42− , AsO43−) are predominant for pH in the range 2–12. The surface charge of adsorbents is controlled by the transfer reactions of proton between the solution and the mineral surface, the charge can be positive, negative or equal to zero, depending 160 hematite

goethite

magnetite

zero-valent iron

[As(V)]/

120

80

40

0 0

40

80

120

160

200

[As(V)] µmol/L Fig. 2. Arsenate speciation in aqueous solution calculated using the software Hydrochemical equilibrium-constant database (HYDRA).

Fig. 4. Representation of the linear Langmuir relationship for adsorption isotherms of As (V) onto hematite, goethite, zero-valent iron and magnetite.

96

Y. Mamindy-Pajany et al. / Desalination 281 (2011) 93–99

2 hematite

goethite

magnetite

zero-valent iron

Log

1

0 -4

-3

-2

-1

0

1

2

3

-1

-2

Log [As(V)] Fig. 5. Representation of the linear Freundlich relationship for adsorption isotherms of As (V) onto hematite, goethite, zero-valent iron and magnetite.

on the pH value. Iron oxides are characterized by their point of zero charge corresponding to a particular value of pH (pHZPC: pH at the zero point of charge) where the mineral surface charge is equal to zero. Arsenate adsorption is promoted when surface charge of adsorbents is positive (e.g. when pH values are lower than pHZPC of adsorbents). At pH values close to pHZPC (for hematite pHZPC = 8.1, goethite pHZPC = 6.9, and magnetite pHZPC = 6.40), the positive charge density of adsorbents becomes low and arsenate adsorption rate is decreased. At alkaline pH values, the surface of mineral adsorbents is negative (pH N pHZPC of adsorbents) and coulombic repulsions between the negatively charged ion (Fig. 2) and negatively charged surface decrease significantly arsenate adsorption rate. Arsenate adsorption onto ZVI is explained by formation of Fe (II) and Fe (III) corrosion products onto iron particles. Bang et al. [26] showed that arsenic adsorption is favored at pH values lower than 8 because the amount of iron hydroxide formed is high in acid medium. Indeed, in the presence of oxygen, iron particles can rapidly oxidize to form iron hydroxides according to the following reactions: 0

þ

2Fe þ 4H þ O2 ¼ 2Fe 4Fe





Fe

þ



þ 2H2 O



þ 4H þ O2 ¼ 4Fe

þ 2H2 O

þ 3H2 O ¼ FeðOHÞ3 þ 3H

þ

3.2. Effects of initial arsenic concentration Arsenate adsorption was studied at two initial concentrations (100 and 500 μg.L− 1) and results are displayed in Fig. 1. At 100 μg As (V) L− 1, hematite is the most effective adsorbent over a wide pH range between 2 and 11 while other adsorbents are effective over a narrow pH range (pH

ranging from 2 to 8). At 500 μg As (V) L− 1, arsenate adsorption rate onto iron oxides is similar (100% of As (V) adsorbed) in the pH range between 2 and 6. At this initial arsenate concentration, ZVI is the least effective adsorbent since adsorption rate is equal to 100% in the pH range 2–5. Initial arsenate concentration has negligible effect on adsorption reactions onto goethite and magnetite due to their high specific surface areas. Hematite and ZVI have the lowest specific surface areas, and their adsorption profiles are related to the initial arsenic concentration. This result is consistent with literature since several works have showed that the initial arsenic concentration can modify arsenate adsorption rate as a function of pH values for various adsorbents [23,27]. 3.3. Adsorption isotherms Adsorption isotherms of hematite, goethite, ZVI and magnetite are displayed in Fig. 3. Results show that adsorption isotherms reach a stable level, for all adsorbents except hematite, when equilibrium arsenate concentration in solution is higher than 100 μM. At very high arsenate concentration in solution, adsorption processes are explained by the formation of surface precipitated between arsenate and surface sites of hematite. Adsorption above the monolayer is generally explained by surface precipitation of arsenate which was highlighted by several authors at the surface of ferrihydrite [28,29] and schwertmannite [30] in acidic medium. In addition, Duc et al. [31] have showed that selenite (HSeO3−/SeO32−) can precipitate onto hematite at high concentration when all surface sites are saturated. Maximum adsorption capacities were estimated graphically, and results show that ZVI has a maximum adsorption capacity five times higher (Γ max = 26 μmol m − 2 ) than other adsorbents (Γmax magnetite = 5.4 μmol m − 2 N Γ max hematite = 3 μmol m − 2 N Γ max

Table 2 Freundlich and Langmuir parameters obtained from the modeling of arsenate adsorption isotherms onto hematite, goethite, zero-valent iron and magnetite at pH 6 and I = 0.01 M NaNO3. Model

Freundlich model

Parameters

KF

Units

μmol m

Hematite Goethite Zero-valent iron Magnetite

1.31 0.56 4.83 0.76

Langmuir model R2

n −2

μmol L 0.186 0.201 0.356 0.374

−1

Γmax μmol m

0.9859 0.9811 0.9773 0.9892

3.3 1.4 30.1 7.1

Log Kads −2

mol L 5.12 5.56 4.75 4.21

−1

−ΔG0 kJ mol 29.23 31.76 27.14 24.05

R2 −1

0.9945 0.9918 0.9928 0.9847

6,0E+00

4,0E+00

B µmol/m2

A µmol/m2

Y. Mamindy-Pajany et al. / Desalination 281 (2011) 93–99

2,0E+00 Langmuir model

97

1,6E+00 1,2E+00 8,0E-01 4,0E-01

Langmuir model

experimental data

0,0E+00 0

50

100

150

200

experimental data

0,0E+00

250

0

50

100

C

3,0E+01

D

6,0E+00

µmol/m2

2,0E+01

µmol/m2

4,0E+00

1,0E+01

Langmuir model

0

50

100

200

Langmuir model

2,0E+00

experimental data Freundlich model

experimental data

0,0E+00

150

[As (V)] µmol/L

[As (V)] µmol/L

150

0,0E+00

200

0

50

100

150

200

250

[As (V)] µmol/L

[As (V)] µmol/L

Fig. 6. Langmuir adsorption isotherms of As(V) onto hematite (A), goethite (B), zero-valent iron (C) and magnetite (D) at 0.01 M NaNO3 and pH = 6. Symbols represent experimental results and dotted line (Langmuir model) or solid line (Freundlich model) represents theoretical results.

goethite = 1.4 μmol m − 2). The maximum adsorption capacity is related to the iron content of adsorbents since it decreases in the following order: ZVI N magnetite N hematite N goethite. Adsorption isotherms were modeled using Langmuir and Freundlich models, and results are given in Figs. 4 and 5. The thermodynamic parameters were calculated for both models (Langmuir and Freundlich) and are displayed in Table 2. Adsorption equilibrium data are fitted well by the Langmuir model for hematite, goethite and ZVI whereas the Freundlich model is more suitable for magnetite (Fig. 6). These results are consistent with several published studies that described adsorption of As (V) onto iron oxides with Langmuir and Freundlich models [32–36]. Although these empirical models fit well experimental data,

Arsenate desorption isotherms are displayed in Fig. 7 for all adsorbents. Desorption isotherms were modeled using the Langmuir model to determine the maximum adsorption capacities (Table 3). The amount of As (V) desorbed with chlorides (MgCl2) decreases in the following order: magnetite (24%)N hematite (10%)N ZVI (8%)N goethite (4%). Arsenate desorption rate with phosphates (Na2HPO4), decreases in

B

6

4

2 adsorption isotherm after desorption with MgCl2 after desorption with Na2HPO4

0

3.4. Reversibility of arsenic (V) adsorption in presence of chlorides and phosphates

0

50

100

150

200

250

As (V) adsorbed µmol/m2

As (V) adsorbed µmol/m2

A

lateral interactions between adsorbed species are not considered to determine equilibrium constants [37].

2

1 adsorption isotherm after desorption with MgCl2 after desorption with Na2HPO4

0

0

50

[As (V)] µmol/L

D 30

20

adsorption isotherm after desorption with MgCl2 after desorption with Na2HPO4

0

0

50

100

[As (V)] µmol/L

150

200

As (V) adsorbed µmol/m2

As (V) adsorbed µmol/m2

C

10

100

150

200

[As (V)] µmol/L

6

4

adsorption isotherm

2

after desorption with MgCl2 after desorption with Na2HPO4

0

0

50

100

150

200

250

[As (V)] µmol/L

Fig. 7. Adsorption and desorption isotherms of As(V) onto hematite (A), goethite (B), zero-valent iron (C) and magnetite (D). Arsenate was successively desorbed with chlorides (MgCl2) and phosphates (Na2HPO4) at pH = 6.

98

Y. Mamindy-Pajany et al. / Desalination 281 (2011) 93–99

Table 3 Langmuir parameters ( Γmax ) obtained from the modeling of adsorption isotherms of As (V) onto hematite, goethite, zero-valent iron and magnetite, and after desorption experiments with chlorides (MgCl2) and phosphates (Na2HPO4) at pH 6. Mineral additives

Ligands

Γmax μmol/m2

R2

Hematite

Without MgCl2 Na2HPO4 without MgCl2 Na2HPO4 without MgCl2 Na2HPO4 without MgCl2 Na2HPO4

3.30 2.95 2.50 1.41 1.36 0.93 30.10 27.70 25.64 7.10 5.37 4.47

0.9945 0.9868 0.9798 0.9918 0.9925 0.9942 0.9928 0.9959 0.9949 0.9847 0.9942 0.9947

Goethite

Zero-valent iron

Magnetite

the following the order: magnetite (37%)N goethite (34%)N hematite (24%)N ZVI (15%). Desorption isotherms demonstrate that chlorides and phosphates can decrease maximum arsenate adsorption capacities onto adsorbents. Chlorides have a low effect (maximum arsenate adsorption capacities are decreased by 10%) on As (V) desorption for ZVI, goethite and hematite. This result is consistent with published studies showing a low effect of chlorides on arsenic desorption rate [38–40]. The desorption rate is higher with phosphates since 40% of As (V) is desorbed from magnetite and goethite [40]. For goethite, desorption rate is similar with the work of O'Reilly et al. [41] showing that 35% of As (V) are desorbed by a solution of phosphates (HPO4:0.006 M) at pH 6 after 24 h. These results can be explained by the similar chemical structure of arsenates and phosphates. Phosphates are tetrahedral anions that form inner sphere complexes with surface functional groups of iron oxides. Competition between phosphates and arsenates for surface adsorption sites decreases adsorbed arsenic [42,43]. Arsenic desorption experiments from ZVI show that a large amount of arsenic (desorption rateb 15% with phosphates) would be strongly adsorbed, suggesting that arsenic is co-precipitated or specifically adsorbed onto ZVI [44,45]. Jain et al. [46] showed that arsenate was specifically adsorbed onto iron oxides, forming inner sphere complexes by ligand exchange with surface hydroxyl groups. Other studies based on chemical and spectroscopic techniques have also revealed specific interactions between arsenic and iron on the surface of amorphous iron hydroxide [47–49].

4. Conclusions Preliminary study of arsenate adsorption onto adsorbents is the first step before considering stabilization tests with contaminated wastes. For this purpose, adsorption experiments were performed under different physico-chemical conditions (pH, initial arsenic concentration) on four commercial adsorbents: hematite, goethite, magnetite and ZVI. Results showed that arsenate adsorption rate is related to pH values and initial arsenic concentrations. Arsenate adsorption is favored under acidic pH values and rapidly decreases in basic medium. Studied adsorbents are effective over large ranges of pH and arsenic concentration. At 500 μg As (V) L− 1, adsorption reactions are effective over a more limited pH range. Arsenate adsorption rate is related to iron content of adsorbents and it increases in the following order: goethite b hematiteb magnetiteb ZVI. The modeling of adsorption isotherms with empirical models revealed that the Langmuir model is suitable for almost all adsorbents (hematite, goethite, ZVI), indicating a monolayer adsorption. Hematite is the most suitable adsorbent over natural pH (pH 6–9) at high arsenic concentrations. Desorption isotherms revealed that arsenic was stronger attached onto hematite than other adsorbents (goethite or magnetite). Zerovalent iron is also an interesting adsorbent for arsenic stabilization in solid wastes since it has high adsorption capacity and a low arsenate desorption rate. Arsenate adsorption onto ZVI is promoted when the

number of active surface sites is increased by the oxidation of iron particles. Acknowledgement The authors thank Jean-Luc Aqua and Laurent Sannier from the SEDIMARD framework and Pierre Boissery from the “Agence de l'eau PACA” for their financial contributions to this research study. References [1] D. Grosdemange, F. Leveque, D. Drousie, J.L. Aqua, J. Méhu, C. Bazin, The SEDIMARD project: presentation and results, International Symposium on Sediment Management –I2SM, Lille (France), 2008. [2] L. Mancioppi, A. Bénard, P. Hennebert, B. Hazebrouck, Dredged sediments: variability of sediment, feedback on dredging practices and the terrestrial management in France, Coastal and Maritime Mediterranean Conference, Hammamet (Tunisia),2009, pp.133. [3] F. Battaglia-Brunet, C. Joulian, A.G. Guezennec, P. Bataillard, N. Marmier, C. Hurel, A. Barats, V. Philippini, Y. Mamindy-Pajany, M. Roméo, P. Bertin, S. Koechler, F. Séby, A. Moulin, Arsenic in marine sediments: Modeling the link between Biogeochemistry, Bioavailability and Ecotoxicology, Third International Congress on “Arsenic in the Environment”, Taiwan, 2010. [4] C. Alzieu, F. Quiniou, Geodrisk, in CD-ROM Geodrisk, Software to assess risks related to dumping of dredged sediments from maritime harbours, 2001. [5] C. Hopenhayn, Arsenic in drinking water: impact on human health, Elements 2 (2006) 103–107. [6] T.S.Y. Choong, T.G. Chuah, Y. Robiah, F.L. Gregory Koay, I. Azni, Arsenic toxicity, health hazards and removal techniques from water: an overview, Desalination 217 (2007) 139–166. [7] M. Shafiquzzaman, M.S. Azam, J. Nakajima, Q.H. Bari, Arsenic leaching characteristics of the sludges from iron based removal process, Desalination 261 (2010) 41–45. [8] E.O. Kartinen, C.J. Martin, An overview of arsenic removal processes, Desalination 103 (1995) 79–88. [9] C.N. Mulligan, R.N. Yong, B.F. Gibbs, An evaluation of technologies for the heavy metal remediation of dredged sediments, J. Hazard. Mater. 85 (2001) 145–163. [10] L. Zoubeir, S. Adeline, C.S. Laurent, C. Yoann, H.T. Truc, L.G. Benoît, A. Federico, The use of the Novosol process for the treatment of polluted marine sediment, J. Hazard. Mater. 148 (2007) 606–612. [11] F. Séby, C. Benoît-Bonnemason, E. Tessier, C. Alzieu, J.L. Aqua, L. Sannier, O.F.X. Donard, Evolution of metals and their chemical forms in land-disposed dredged marine sediments, Paralia 2 (2009) s3.1–s3.12. [12] V. Zaspalis, A. Pagana, S. Sklari, Arsenic removal from contaminated water by iron oxide sorbents and porous ceramic membranes, Desalination 217 (2007) 167–180. [13] L. Ruiping, S. Lihua, Q. Jiuhui, L. Guibai, Arsenic removal through adsorption, sand filtration and ultrafiltration: in situ precipitated ferric and manganese binary oxides as adsorbents, Desalination 249 (2009) 1233–1237. [14] P. Sabbatini, F. Rossi, G. Thern, A. Marajofsky, M.M.F. de Cortalezzi, Iron oxide adsorbers for arsenic removal: a low cost treatment for rural areas and mobile applications, Desalination 248 (2009) 184–192. [15] S. Brunauer, P.H. Emmett, E. Teller, Adsorption of gases in multimolecular layers, J. Am. Chem. Soc. 60 (1938) 309–319. [16] N. Jordan, C. Lomenech, N. Marmier, E. Giffaut, J.J. Ehrhardt, Sorption of selenium(IV) onto magnetite in the presence of silicic acid, J. Colloid Interface Sci. 329 (2009) 17–23. [17] P. Van Cappellen, L. Charlet, W. Stumm, P. Wersin, A surface complexation model of the carbonate mineral-aqueous solution interface, Geochim. Cosmochim. Acta 57 (1993) 3505–3518. [18] N. Marmier, A. Delisée, F. Fromage, Surface complexation modeling of Yb(III), Ni (II), and Cs(I) sorption on magnetite, J. Colloid Interface Sci. 211 (1999) 54–60. [19] N. Marmier, F. Fromage, Comparing electrostatic and nonelectrostatic surface complexation modeling of the sorption of lanthanum on hematite, J. Colloid Interface Sci. 212 (1999) 252–263. [20] Y. Mamindy-Pajany, C. Hurel, N. Marmier, M. Roméo, Arsenic adsorption onto hematite and goethite, C. R. Chim. 12 (2009) 876–881. [21] P. Quevauviller, G. Rauret, J.F. López-Sánchez, R. Rubio, A. Ure, H. Muntau, Certification of trace metal extractable contents in a sediment reference material (CRM 601) following a three-step sequential extraction procedure, Sci. Total. Environ. 205 (1997) 223–234. [22] N.E. Keon, C.H. Swartz, D.J. Brabander, C. Harvey, H.F. Hemond, Validation of an arsenic sequential extraction method for evaluating mobility in sediments, Environ. Sci. Technol. 35 (2001) 2778–2784. [23] S. Dixit, J.G. Hering, Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: implications for arsenic mobility, Environ. Sci. Technol. 37 (2003) 4182–4189. [24] J. Giménez, M. Martínez, J. de Pablo, M. Rovira, L. Duro, Arsenic sorption onto natural hematite, magnetite, and goethite, J. Hazard. Mater. 141 (2007) 575–580. [25] L. Weng, W.H. Van Riemsdijk, T. Hiemstra, Effects of fulvic and humic acids on arsenate adsorption to goethite: experiments and modeling, Environ. Sci. Technol. 43 (2009) 7198–7204. [26] S. Bang, M.D. Johnson, G.P. Korfiatis, X. Meng, Chemical reactions between arsenic and zero-valent iron in water, Water Res. 39 (2005) 763–770.

Y. Mamindy-Pajany et al. / Desalination 281 (2011) 93–99 [27] X. Sun, H.E. Doner, Adsorption and oxidation of arsenite on goethite, Soil Sci. 163 (1998) 278–287. [28] R. Stanforth, Comment on arsenite and arsenate adsorption on ferrihydrite: surface charge reduction and net OH− release stoichiometry, Environ. Sci. Technol. 33 (1999) 3695–3696. [29] Y. Jia, L. Xu, Z. Fang, G.P. Demopoulos, Observation of surface precipitation of arsenate on ferrihydrite, Environ. Sci. Technol. 40 (2006) 3248–3253. [30] L. Carlson, J.M. Bigham, U. Schwertmann, A. Kyek, F. Wagner, Scavenging of As from acid mine drainage by schwertmannite and ferrihydrite: a comparison with synthetic analogues, Environ. Sci. Technol. 36 (2002) 1712–1719. [31] M. Duc, G. Lefèvre, M. Fédoroff, Sorption of selenite ions on hematite, J. Colloid Interface Sci. 298 (2006) 556–563. [32] P. Lakshmipathiraj, B.R.V. Narasimhan, S. Prabhakar, G. Bhaskar Raju, Adsorption of arsenate on synthetic goethite from aqueous solutions, J. Hazard. Mater. 136 (2006) 281–287. [33] L. Sigg, P. Behra, W. Stumm, Chemistry of Aquatic Ecosystems: Natural water chemistry and interfaces in environment, Paris, 2000. [34] S. Kundu, A.K. Gupta, Adsorption characteristics of As(III) from aqueous solution on iron oxide coated cement (IOCC), J. Hazard. Mater. 142 (2007) 97–104. [35] J.C. Hsu, C.J. Lin, C.H. Liao, S.T. Chen, Removal of As(V) and As(III) by reclaimed iron-oxide coated sands, J. Hazard. Mater. 153 (2008) 817–826. [36] M. Habuda-Stanic, B. Kalajdzic, M. Kules, N. Velic, Arsenite and arsenate sorption by hydrous ferric oxide/polymeric material, Desalination 229 (2008) 1–9. [37] Y. Jeong, M. Fan, S. Singh, C.L. Chuang, B. Saha, J. Hans van Leeuwen, Evaluation of iron oxide and aluminum oxide as potential arsenic(V) adsorbents, Chem. Eng. Process. 46 (2007) 1030–1039. [38] C. Su, R.W. Puls, Arsenate and arsenite removal by zerovalent iron: effects of phosphate, silicate, carbonate, borate, sulfate, chromate, molybdate, and nitrate, relative to chloride, Environ. Sci. Technol. 35 (2001) 4562–4568.

99

[39] K.H. Goh, T.T. Lim, Arsenic fractionation in a fine soil fraction and influence of various anions on its mobility in the subsurface environment, Appl. Geochem. 20 (2005) 229–239. [40] J. Youngran, M. Fan, J. Van Leeuwen, J.F. Belczyk, Effect of competing solutes on arsenic(V) adsorption using iron and aluminum oxides, J. Environ. Sci. 19 (2007) 910–919. [41] S.E. O'Reilly, D.G. Strawn, D.L. Sparks, Residence time effects on arsenate adsorption/ desorption mechanisms on goethite, Soil Sci. Soc. Am. J. 65 (2001) 67–77. [42] B.A. Manning, S. Goldberg, Modeling competitive adsorption of arsenate with phosphate and molybdate on oxide minerals, Soil Sci. Soc. Am. J. 60 (1996) 121–131. [43] B.P. Jackson, W.P. Miller, Effectiveness of phosphate and hydroxide for desorption of arsenic and selenium species from iron oxides, Soil Sci. Soc. Am. J. 64 (2000) 1616–1622. [44] J.A. Lackovic, N.P. Nikolaidis, G.M. Dobbs, Inorganic arsenic removal by zero-valent iron, Environ. Eng. Sci. 17 (2000) 29–39. [45] N.P. Nikolaidis, G.M. Dobbs, J.A. Lackovic, Arsenic removal by zero-valent iron: field, laboratory and modeling studies, Water Res. 37 (2003) 1417–1425. [46] A. Jain, K.P. Raven, R.H. Loeppert, Arsenite and arsenate adsorption on ferrihydrite: surface charge reduction and net OH− release stoichiometry, Environ. Sci. Technol. 33 (1999) 1179–1184. [47] M.L. Pierce, C.B. Moore, Adsorption of arsenite and arsenate on amorphous iron hydroxide, Water Res. 16 (1982) 1247–1253. [48] T.H. Hsia, S.L. Lo, C.F. Lin, D.Y. Lee, Characterization of arsenate adsorption on hydrous iron oxide using chemical and physical methods, Colloids Surf. A 85 (1994) 1–7. [49] G.A. Waychunas, B.A. Rea, C.C. Fuller, J.A. Davis, Surface chemistry of ferrihydrite: Part 1. EXAFS studies of the geometry of coprecipitated and adsorbed arsenate, Geochim. Cosmochim. Acta 57 (1993) 2251–2269.

Suggest Documents