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Ferric chloride forced hydrolysis is shown to be a good method for increasing the iron content of activated carbons (ACs). Iron content increased linearly with hydrolysis time, and ACs with iron content as high as 9.4wt.% at 24h hydrolysis time could be prepared. The increase in iron content did not produce any modification in the textural parameters determined by nitrogen adsorption at 77K. Iron-based nanoparticles, homogeneous in size and well-dispersed in the carbon matrix, were obtained. Nanoparticles forming iron (hydr)oxide agglomerates at the outer surface of the carbon grains at hydrolysis times higher than 6h were also produced. The AC obtained after 6h of ferric chloride forced hydrolysis removed 94% of the arsenic present in a groundwater from the State of Chihuahua (Mexico), whereas the commercial AC used as precursor allowed the removal of only 14%. The lower performance in arsenic removal observed for AC prepared using long forced hydrolysis time (24h) is probably due to the existence of iron (hydr)oxides nanoparticles agglomerates, which once hydrated could prevent diffusion of arsenate (HAsO(4)(-)) towards the inner surface of the AC grain.

Arsenic removal from natural well water from the state of Chihuahua (Mexico) is investigated by adsorption 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, containing 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 conditions, 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.%.