Removal of As3plus cations from water by activated carbon, bentonite and zeolite in a batch system at different pH

Adsorption of As3+ cations by natural materials is a relatively well-studied problem although much remains to be learned about it. As a consequence of pollution, remarkably high arsenic content has been reported in numerous natural waters. The subject of this paper is the adsorption of As3+ cations by granulated activated carbon (GAC), bentonite and zeolite (0.1-0.3 g), which could be used prospectively as potential supplement to other materials. The quantitative analysis of all samples was performed by Inductively Coupled Plasma-Optical Emission Spectrometry. The results indicate that the amount of As3+ cations in a solution decreases with time for all the three adsorbents. The research also showed that 0.2 g of GAC and bentonite is an optimum adsorbent amount at pH 6.5. The same amount of zeolite has the best adsorption capacity at pH 3.5. Parallel testing of these materials showed that GAC had the highest adsorption potential (50%) compared to bentonite and zeolite (11.7% and 26.5%). Most of the adsorption process by GAC takes place at the first 45 min; in the case of bentonite it is the first 30 min and for zeolites the first 15 min (best starting; 19.5%). The reason for the lower adsorption of As3+ cations by bentonite is its instability in acidic environment, while zeolite shows reduced isomorphic replacement ability due to different charges compared to potentially convertible cations. The adsorption of arsenic on these natural materials has proven to be one of the most efficient and economical method of arsenic removal