Effects of Soils on Environmental Stability of Spent Mg-Based and Ca-Based Adsorbents Containing Arsenite.

Spent adsorbents used in As removal treatment may re-leach As. In this study, the effects of soil on spent Mg-based and Ca-based adsorbents were investigated. The spent adsorbents containing arsenite (As(III)) were prepared by adsorbing As(III) on MgO, Mg(OH)₂, CaO, and Ca(OH)₂ powder reagents. Kuroboku soil (Ku), yellow-brown forest soil (YF), Kanuma soil (Ka), river sand (RS), and mountain sand (MS) were used as soil samples. The As leaching ratio was examined in coexistence with soil via shaking tests, and the results were compared with those of a previous study on adsorbents containing arsenate (As(V)). The environmental stability of the spent adsorbents was found to vary greatly depending on the combination of the As valence, adsorbent type, and soil type. However, regardless of the adsorbent or soil type, the spent adsorbents containing As(III) were more likely to leach As than those containing As(V). Additionally, the As leaching ratio was generally lower in Ku and YF and higher in Ka, RS, and MS. For environmentally friendly and sustainable As removal treatment, disposal, and management, the selection of MgO as the adsorbent and treatment involving the oxidation treatment of As(III) to As(V) before adsorbing As onto adsorbents are recommended. [ABSTRACT FROM AUTHOR]