Removal of Arsenic by Alumina: Effects of Material Size, Additives, and Water Contaminants

Effects of some characteristics of alumina as material adsorbent on arsenic removal from water are presented. In particular, the effect of the alumina particle size has been firstly experimentally observed, then studied by means of a diffusive model. The effects of pH and other contaminants in the aqueous solution have been also measured. Finally, an improvement of the arsenic adsorption performances has been attempted by using a TiO2 coating of commercial alumina. The characterization of alumina in the different forms has been done by X-ray diffraction, Brunauer–Emmett–Teller specific area measurement and scanning electron microscopy. The kinetics and equilibrium experiments of arsenic(V) removal by the adsorbent materials were studied in a batch mode. The alumina particulate size showed to play a key role in the adsorption process. In fact, among the tested adsorbent types, that material with the lowest particle size (i.e., 20 μm) showed the maximum arsenic(V) uptake capacity, which was slightly <20 mg/g as calculated according to the Langmuir isotherm. The competitive anions, such as phosphate and silica, negatively affected the adsorption process determining a lower maximum uptake capacity of arsenic(V), whereas sulfate ions had a moderate positive effect within the typical groundwater arsenic concentration range. All the tested materials demonstrated to be capable of reducing the arsenic concentration below 10 µg/L, which is the limit to be respected by drinking water according to the World Health Organization recommendations.