Adsorption of Arsenate onto Iron Oxide Coated Activated Carbon in Groundwater

Abstract

Arsenic is an abundant element that exists in both natural and anthropogenic sources, including groundwater in many parts of the world. Adsorption is one of the best technologies for arsenic removal from water, particularly for a small-scale system. The aim of this study was to investigate the arsenate (As(V)) adsorption onto iron oxide coated activated carbon. The physicochemical properties were characterized by scanning electron microcopy (SEM) with energy dispersive X-ray spectroscopy (EDX), porosity and pore size distribution analysis. Batch experiment was conducted to examine the effects of the equilibrium solution pH, adsorbent dosage, contact time and co-existing ions on arsenate removal. The results indicate that the maximum arsenate adsorption efficiency is achieved 90% in the condition of equilibrium pH 5.0, adsorbent dosage of 5 g/L and contact time of 16 h with the initial arsenate (As(V)) concentration of 1 mg/L. Langmuir and Freundlich models were used to determine the adsorbent capacity for arsenate removal by iron oxide coated activated carbon. The Rapid Lab-Scale Column study was carried out by using iron oxide coated granular activated carbon (Fe-GAC) as an adsorbent for the removal of arsenate (As(V)) with flow rate 1 mL/min. The results showed that the breakthrough time was reached at 120 hours. The breakthrough curves showed that the Thomas model gave the best result for the operating condition. Iron oxide coated activated carbon was regenerated by using 0.1M NaOH, it is observed by effect of regeneration cycles that the regenerated adsorbent was almost as efficient as the new adsorbent.