Prototype Experiments Assessing Arsenic and Iron Removal Efficiencies through Adsorption Using Natural Skye Sand

Abstract

Based on earlier batch and column experimental results, it was established that Skye sand is suitable for removing arsenic from water through adsorption. As a real-size prototype may not always replicate results from batch and column experiments, this paper presents experimental results on arsenic removal through a prototype arsenic filter using the same Skye sand used in the batch and column experiments. As arsenic-contaminated water is often associated with a high concentration of iron, which causes blockage of the filter system, this study also investigates the removal of iron from the water through the same filter media. First, several physical properties of the Skye sand were established through XRF, XRD, SEM and EDX analyses. Then, a real-size prototype was made based on an earlier design of a similar filter made of iron oxide-coated sand (IOCS). It was found that the current filter is capable of removing arsenic consistently to a level below the detection limit (0.05 µg/L) for a considerable period (up to 150 bed volumes). Additionally, the same filter is capable of removing iron to a level below the WHO-acceptable limit (0.3 mg/L). Analytical calculation suggests that the current prototype filter with Skye sand can produce arsenic-free water continuously for 600 days (100 L per day) with a feed arsenic concentration of 500 µg/L.