Evaluation of iron oxide and aluminum oxide as potential arsenic(V) adsorbents

Iron (Fe2O3) and aluminum oxide (Al2O3) were found to be good and inexpensive adsorbents for As(V) removal in drinking water despite their relatively small surface area. The experimental results for this study suggest that by careful selection of the relative concentration of arsenic, pH, and dosages of Fe2O3 and Al2O3, As(V) removal efficiency as high as 99% can be achieved. At lower pH (<7), and also depending on the dosages of Fe2O3 and Al2O3 and the initial concentration of As(V), over 95% of As(V) adsorption was observed within a contact time of 20–60 min. The adsorption of As(V) on Fe2O3 and Al2O3, like that on other nonporous adsorbents, is mainly controlled by the surface area. The adsorption of As(V) on Fe2O3 and Al2O3 was found to follow the Langmuir isotherm between the pH values of 5 and 9. The maximum As(V) uptake values at pH 6 – the optimal pH value for adsorption – using Fe2O3 and Al2O3, were calculated as 0.66 mg/g and 0.17 mg/g, respectively. No significant variation in the uptake of As(V) on Fe2O3 as compared with Al2O3 was observed at different pH values. The initial sorption rate of Fe2O3 is higher than that of Al2O3. All these factors make Fe2O3 a better adsorbent than Al2O3. Fe2O3 is a useful and effective adsorbent for POE (pint of entry) and POU (point of use) water treatment systems, such as small-scale commercial or individual home water treatment systems. Even though the adsorption capacities of Fe2O3 and Al2O3 for As(V) are quite low compared with those of other absorbents, their low cost makes them useful adsorbents. They may be very useful in arsenic removal from water in endemic areas such as China, India, and Bangladesh.