Arsenate Remediation Using Nanosized Modified Zerovalent Iron Particles

摘要

Arsenate [As (V)J removal kinetics in aqueous solutions using modified nanosized zerovalent iron (Fe~0) 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~0 particles. Pseudo-first-order rate equations were found to satisfactorily describe arsenate removal kinetics using Fe~0, 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 338 mM), temperature (25, 45, and 65℃) and competing inorganic anions (sulfate, chloride, nitrate, phosphate, and chromate) on arsenate removal using NiFe particles. Increasing temperatures (25-65℃) increased arsenate removal rates, whereas competing sorption of phosphate and sulfate inhibited arsenate removal.