Redox reaction of Fe(0) with As(V) sorbed onto goethite-coated sand under anoxic conditions

Abstract

The objective of this study was to determine the applicability of reductive immobilization of As(V) by Fe(0) [zero valent iron (ZVI)] to the As contaminated soil. The experiments comprised reactions between ZVI and As(V) absorbed onto goethite-coated sand (GCS) simulating heterogeneous soil environment, and reactions between ZVI and dissolved As(V) simulating homogeneous environment. Arsenic(III+V) removal ratio in the heterogeneous system was lower than in the homogeneous system, which was due to the incomplete reduction of As(V) adsorbed onto GCS. Incomplete reduction might be caused by difficulty of desorption of As(V) or lower accessibility of ZVI to As(V) adsorbed onto GCS to react. Almost half of As(V) adsorbed onto GCS was instantly desorbed. Arsenic(III) produced by reaction between As(V) and ZVI was quickly removed by iron hydroxide including As(III). Effect of air injection for As removal in the heterogeneous system was smaller than in the homogeneous system because of difficulty in the oxidation of adsorbed Fe(II) on GCS in the heterogeneous system.