Removal of arsenic by alumina. Effects of material size, additives and water contaminants

In this work an investigation on the effects of some characteristics of alumina, as material adsorbent, on the arsenic removal from water is presented. In particular, the effect of the alumina particle size on the arsenic removal effectiveness has been firstly experimentally observed, than studied by means of a diffusive model. The effects of pH and other contaminants into 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 the synthesized composite has been done by X-ray diffraction, BET specific area measurement and SEM. The kinetics and equilibrium experiments of removing arsenic (V) by the synthesized materials were studied in batch mode. The alumina particulate size plays a key role in the adsorption process. In fact, among the tested adsorbent types, that one having the lowest particle size showed the maximum arsenic (V) uptake capacity, which was slightly below 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.