Arsenate remediation using nanosized modified zerovalent iron particles

Arsenate [As (V)] removal kinetics in aqueous solutions using modified nanosized zerovalent iron (Fe-O) particles such as NiFe and PdFe was studied. NiFe and PdFe particles were synthesized by the borohydride reduction of nickel and palladium salts on Fe-O particles. Pseudo-first-order rate equations were found to satisfactorily describe arsenate removal kinetics using Fe-O, NiFe, and PdFe Particles (solids concentration of 2 g L-1) at low arsenate concentrations (1.35 mM). As compared to zerovalent iron (k(obs) of 0. 037 min(-1)), the arsenate removal rate was up to 2.5 times faster (k(obs) of 0.091 min(-1)) using NiFe particles, whereas it was threefold lower in the case of PdFe particles (k(obs) of 0.011 min(-1)). With increasing contact times, deviation from first-order kinetics was observed, presumably arising from the loss of available sites on the solid surface. The surface area normalized pseudo-first-order rate constant k(sa) was 0. 0089 L m-(2) min(-1) for NiFe. Additional experiments were performed to study the influence of initial arsenate concentration (0.67 and 3.38 mM), temperature (25, 45, and 650 C) and competing inorganic anions (sulfate, chloride, nitrate, phosphate, and chromate) on arsenate removal using NiFe particles. Increasing temperatures (25 - 65 degrees C) increased arsenate removal rates, whereas competing sorption of phosphate and sulfate inhibited arsenate removal.