The utilization of low-grade clay materials as selective sorbents represents one of the most effective possibilities of As removal from contaminated water reservoirs. The simple pre-treatment of these materials with Fe (Al, Mn) salts can significantly improve their sorption affinity to As oxyanions. The natural kaolin calcined at 550 degrees C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with Fe-II, Fe-III, Al-III and Mn-II salts were used to remove of As from the model anoxic groundwater with As-III concentration about 0.5 and 10 mg L-1. All the pre-treating methods were appropriate for bentonite; the efficiency of As-III sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g(-1). In the case of metakaolin, Fe-II- and Mn-II-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after Fe-III and Al-III pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g(-1). (C) 2008 Elsevier B.V. All rights reserved.