Incorporation of arsenic during the formation of Mg-bearing minerals at alkaline condition

The release of toxic anions during the chemical weathering of alkaline wastes such as blast furnace slag and coal fly ash presents a serious problem to public health and the environment. This study investigated arsenate sorption behavior onto Mg-bearing minerals formed in the Mg–Si–Al system at alkaline pH conditions in order to understand the safe removal and encapsulation of arsenate by Mg-bearing minerals under such conditions. on experiments were performed during and after mineral formation and leaching tests using phosphate bearing solution were conducted to understand arsenic association with the minerals. The results revealed that brucite (Mg(OH)2), hydrotalcite (Mg6Al2(CO3)(OH)16·4(H2O)) and serpentine (MgSi2O5(OH)4) have high uptake capacity for arsenate. However, arsenic incorporation was only observed during the formation of high Al content hydrotalcite and serpentine minerals and was greatly enhanced at higher temperature. This implies that by controlling pore water chemistry of alkaline wastes with high reactivity, the irreversible fixation of arsenic by Mg-bearing minerals in alkaline conditions can be expected.