Combination of hydrous iron oxide precipitation with zeolite filtration to remove arsenic from contaminated water

Abstract

Groundwater arsenic contamination imposes a great threat to people worldwide. Thus, developing new and cost-effective methods to remove arsenic from groundwater and drinking water becomes imminent. With several patents granted, using hydrous iron/aluminum hydroxides (HFO/HAO) to remove arsenic from water is a proven technology. The method involved in addition of ferric iron or alumina to induce precipitation for arsenic sorption. Currently used filtration media were limited to sand, granular activated carbon, granular activated alumina. In this research, a natural clinoptilolite zeolite was used as the filtration media to remove arsenic-containing HFO/HAO co-precipitates. The results showed that removal of As from water can be achieved relatively effectively using zeolites as filtration media after HFO precipitation and As sorption on precipitated HFO. The As(III) and As(V) sorption capacities on precipitated HFO were 48 and 68 mg/g, respectively. The optimal pH for maximum As removal was in neutral range between 6.5 and 9. Depending on the initial As concentration and redox conditions, the minimal Fe(III) needed to reduce the As concentration below standard would be around 10 mg/L. The method could achieve better results when the water was under oxic condition, particularly in the presence of extensive dissolved Fe.