Modified aluminosilicates as low-cost sorbents of As(III) from anoxic groundwater

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 °C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with FeII, FeIII, AlIII and MnII salts were used to remove of As from the model anoxic groundwater with AsIII concentration about 0.5 and 10 mg L−1. All the pre-treating methods were appropriate for bentonite; the efficiency of AsIII sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g−1. In the case of metakaolin, FeII- and MnII-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after FeIII and AlIII pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g−1.