Journal of Hazardous Materials 165 (2009) 893–902 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Synthesis, characterization and performance in arsenic removal of iron-doped activated carbons prepared by impregnation with Fe(III) and Fe(II) G. Mu ˜ niz a,d , V. Fierro a,∗ , A. Celzard b , G. Furdin a , G. Gonzalez-Sánchez c , M.L. Ballinas d a Laboratoire de Chimie du Solide Minéral, Nancy-Université, UMR CNRS 7555, BP 239, 54506 Vandœuvre-lès Nancy, France b Laboratoire de Chimie du Solide Minéral, UMR CNRS 7555, Nancy-Université, ENSTIB, 27 rue du Merle Blanc, BP 1041, 88051 Épinal Cedex 9, France c Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chih., 31109 Chihuahua, Mexico d Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito Universitario S/N, Chihuahua, Mexico article info Article history: Received 9 July 2008 Received in revised form 17 October 2008 Accepted 20 October 2008 Available online 28 October 2008 Keywords: Activated carbon Arsenic Iron Natural water Adsorption abstract Arsenic removal from natural well water from the state of Chihuahua (Mexico) is investigated by adsorp- tion using a commercial activated carbon (AC). The latter is used as such, or after oxidation by several chemicals in aqueous solution: nitric acid, hydrogen peroxide, and ammonium persulphate. Raw and oxidised activated carbons are fully characterised (elementary analysis, surface chemistry, pore texture parameters, pH ZC , and TEM observation). Adsorption of As is measured in the aforementioned water, con- taining ca. 300 ppb of arsenic: removal of As is poor with the raw AC, and only the most oxidised carbons exhibit higher performances. By contrast, iron-doped ACs are much more efficient for that purpose, though their As uptake strongly depends on their preparation conditions: a number of samples were synthesised by impregnation of raw and oxidised ACs with HCl aqueous solutions of either FeCl 3 or FeCl 2 at various concentrations and various pH. It is shown that iron(II) chloride is better for obtaining high iron contents in the resultant ACs (up to 8.34 wt.%), leading to high As uptake, close to 0.036 mg As/g C. In these condi- tions, 100% of the As initially present in the natural well water is removed, as soon as the Fe content of the adsorbent is higher than 2 wt.%. © 2009 Published by Elsevier B.V. 1. Introduction The presence of dissolved arsenic in groundwater has provoked an international concern due to its known toxicity [1]. The decrease of the maximum arsenic level in drinking water down to10 gL -1 imposed the modification of more than 4000 water supply systems utilised by 20 millions of people [2]. Therefore, there is a great need for applying efficient methods for arsenic removal from drinking water. So far, a variety of methods have been developed for this purpose. The conventional physico-chemical processes used for arsenic removal can be classified on the basis of the involved separa- tion mechanisms: precipitation, ion exchange, membrane, and adsorption technologies. Precipitation is widely used because of its simplicity and reduced cost; however, in order to remove effi- ciently arsenic at acceptable levels, large amounts of chemicals are necessary. Another disadvantage is that precipitation also creates a great sludge volume, which is not easy to reprocess or cannot be directly disposed. Moreover, arsenic(III) sulphide and calcium or ∗ Corresponding author. Fax: +33 383684619. E-mail address: Vanessa.Fierro@lcsm-uhp.nancy.fr (V. Fierro). ferric arsenates, which are the most common arsenic precipitates, are unstable under some definite conditions and are therefore not suitable for direct disposal, otherwise As could be released in the environment [3]. Ion exchange is the process by which chlorides or other anions bound at the surface of a resin are exchanged with arsenic-based anions from the solution. This process has the disad- vantage of releasing harmful chemicals into the environment when the resin is regenerated [4]. Finally, membrane processes are com- monly employed, but this technology is expensive, mainly because of the high energy requirements [5]. The technology of adsorption is based on materials having a high affinity for dissolved arsenic. Adsorption of arsenic by iron compounds has been established by several authors [6–8]. Elemen- tary iron [9–11], granular iron hydroxides, and ferrihydrites [12–15] have been proposed for the removal of arsenic from water. Most of the adsorption processes investigated so far were reported in the excellent review of Mohan and Pittman [16], whereas the other techniques were considered in that of Choong et al. [17]. Activated carbons (ACs) are by far the most widely used adsor- bents for water purification. AC adsorption are strongly dependent on the physico-chemical properties of the solution, and hence on arsenic speciation; for example, adsorption capacities are very low at high pH [18,19]. Arsenic removal by AC can be improved by dop- 0304-3894/$ – see front matter © 2009 Published by Elsevier B.V. doi:10.1016/j.jhazmat.2008.10.074