Comparison of different iron oxide adsorbents for combined arsenic, vanadium and fluoride removal from drinking water

Abstract

Contamination of groundwater by arsenic due to natural processes is rather common worldwide and hinders its use for drinking water supply. In many cases, arsenic contamination is found together with high levels of vanadium and fluoride. Therefore, more than one type of treatment is required to reduce concentrations of all these contaminants below non-hazardous levels so to make the source drinkable. The present study investigated the uptake capacity of arsenic, vanadium and fluoride by three iron-based adsorbent media differing for particle size, iron content and specific surface. The aim of the treatment was to achieve the maximum allowable concentration set on drinking water by the law. The removal efficiency was evaluated in single and binary contaminated solutions. All the tested adsorbents demonstrated an efficient and rapid removal process of both arsenic and vanadium in the single and binary solutions, with a higher adsorption capacity for vanadium; by contrast, they were unable to achieve an appreciable reduction in fluoride concentration. The particle size showed to have the highest effect on the removal rate. The best kinetic and isotherm models and the related parameters were determined for each condition. In the binary solutions, the presence of vanadium hindered the uptake of arsenic, whereas fluoride did not have any effect. The results obtained showed that the iron-based adsorbents tested in the present study can be successfully applied for the treatment of drinking water contaminated by arsenic and vanadium, whereas a different medium or process needs to be adopted for the removal of fluoride.