Enhanced removal of As(III) by heterogeneous catalytic oxidation of As(III) on Fe-biochar fibers with H2O2 and hydroxylamine

Abstract

Iron oxide-modified biochars are increasingly recognized as a promising arsenic adsorbent. However, most of them face serious challenges in the rapid and efficient removal of As(III). Herein, we integrated the iron oxide nanoneedles vertically covered biochar fibers (Fe-BFs) with H2O2 and Hydroxylamine (HA) to construct a heterogeneous catalytic system for the rapid oxidation and deep removal of As(III) from water. The system oxidized the As(III) to As(V) with high efficiency, and then the generated As(V) could be rapidly removed by adsorption onto Fe-BFs. The removal efficiency of As(III) by Fe-BFs/H2O2/HA at 120 min reached up to 98.93%, which is much higher than that of by Fe-BFs (69.20%) and Fe-BFs/H2O2 (92.32%). The system could work reliably in a wide pH range (4–10). Moreover, fixed-bed column experiments demonstrated that the addition of H2O2 and HA could increase the effective treatment volume from ~350 bed volume (BV) to ~700 BV to meet the drinking water standard (<10 μg/L). The introduction of HA induced the reduction of surface Fe(III) of Fe-BFs to surface Fe(II), which reacted with H2O2 to produce OH. The OH played a very important role in promoting the removal of As(III). This study offers a new strategy to enhance the applicability of Fe modified biochar for As(III) removal.