Effect of Spatial Distribution and Aging of ZVI on the Reactivity of Resin–zvi Composites for Arsenite Removal

A zero-valent iron (ZVI)–resin composite (D201–ZVI) has been proven as an effective arsenic removal material. Here, the effect of ZVI distribution and aging on the reactivity of the hybrid composite was investigated by comparing the As(III) removal performances of freshly synthesized and aged D201–ZVI composites. The ZVI distribution and structures of these composites were characterized using X-ray diffraction, X-ray photoelectron spectrometry, and scanning electron microscope equipped with an energy-dispersive X-ray analyzer (SEM-EDX). After aging in aerated water for 96 h, the ZVI distribution in the aged composites did not change significantly, which was confirmed by SEM-EDX. However, the Fe0 content decreased as the aging time increased. Among the as-prepared composites with variant ZVI distributions, the hybrids with more uniform ZVI distribution exhibited higher removal efficiency and faster reaction rate. Experimental results show that the D201–ZVI gradually lost reactivity with an increase in aging time from 24 to 96 h. The effects of aging time on the speciation of As suggest that the reduced As(III) removal efficiency was attributable to the decrease of the Fe0 content. Furthermore, the importance of the ZVI distribution is proposed to explain the aging effect.