A simple and novel method to enhance As (V) removal by zero valent iron and activated iron media through air injection at intervals.
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A simple and novel method was developed at first time to enhance As (V) removal by zero valent iron (ZVI) and activated ZVI/Fe3O4 media (AIM) through air injection at intervals. Fe (II) was essential to trigger As (V) removal by ZVI and AIM, and magnetite did not improve As (V) removal. In presence of 0.5mM Fe (II) under anaerobic condition, 10gL-1 ZVI and AIM showed same As (V) removal efficiency including percentage, capacity and rate of >99.999%, 3.0mg/g ZVI/AIM and 0.013mg As (V)/(g min), respectively. Compared to the passivation of ZVI and AIM after one-time air injection, As (V) removal efficiency was significantly improved by intermittent air injection with increased air volume and injection frequency. After third time of 1.0mL air injection at 30min intervals, As (V) removal percentage and capacity remained same remarkable values as that under anaerobic condition, but total removal rate was further improved to 0.033mg As (V)/(g min). XPS results indicated that As (V) was completely reduced to As (III) and As (0) by Fe (0) under anaerobic condition, but quick adsorption/co-precipitation of As (V) followed by reduction to As (III) and As (0) by Fe (0) was the main mechanism under aerobic condition. This study suggests the addition of Fe (II) followed by simple air injection at intervals harnesses the reactivity of traditional ZVI for arsenic removal.
