[A-GE28] Energy-Environment-Water Nexus and Sustainable Development

[AGE28-P04] Effects of Silicic Acid on Arsenite Leaching from Spent Magnesium-based Arsenic Adsorbents

*Hajime Sugita¹, Terumi Oguma¹, Ming Zhang¹, Junko Hara¹, Yoshishige Kawabe¹ (1.National Institute of Advanced Industrial Science and Technology)

Keywords:Arsenite Leaching, Spent Adsorbent, Magnesium Oxide, Magnesium Hydroxide, Silicic Acid

The spent adsorbents after arsenic removal in arsenic contaminated water itself contain a large amount of arsenic. If they are discarded without appropriate treatment, there is a concern that secondary arsenic pollution may occur due to arsenic leaching from them. In our previous studies, it was suggested silicic acid greatly affects leaching behavior of arsenate from the spent adsorbents. In this study, in order to examine the effects of silicic acid on arsenite leaching from the spent adsorbents, leaching tests with silicic acid solution and 2 kinds of spent magnesium-based adsorbent (MgO and Mg(OH)₂) were carried out. From the experimental results, the arsenite leaching from spent Mg-based adsorbents was found to be inhibited by silicic acid present in the solution. In our previous study on the spent Mg-based adsorbents adsorbed with arsenate, it has been reported that the leaching amount of arsenate was higher as the initial silicic acid concentration in the solution was higher. The leaching behavior of arsenite is significantly different from that of arsenate. Therefore, under the presence of silicic acid, the leaching-precipitation mechanisms of arsenite are considered to be different from those of arsenate.