No abstract

It is important to remove hydrogen sulfide to maintain healthy ecosystems as well as viable aquaculture activities in enclosed water bodies. Granulated coal ash with high adsorption capacity for hydrogen sulfide is a by-product generated from coal combustion processes in coal-fired power plants. The purposes of this study were to (1) verify the regeneration of the adsorption sites for hydrogen sulfide on the granulated coal ash by redox reaction which changes between oxic and anoxic conditions and (2) prove the regeneration mechanisms of the adsorption site which leads to high adsorption capacity for hydrogen sulfide. XAFS analyses of the granulated coal ash revealed that the adsorption site for hydrogen sulfide on the granulated coal ash was regenerated at least 10 times through oxidation of manganese oxide under oxic conditions. A positive correlation (r=0.995) between the peak top energy of manganese XAFS in the GCA collected from field trial sites and the Eh of the sediments applied with the GCA was observed. These results proved that hydrogen sulfide was adsorbed and oxidized by the granulated coal ash during the stratified season. During the vertical mixing seasons, oxygen regenerates the adsorption site for hydrogen sulfide. It is concluded that this 3 regeneration of adsorption site gives the granulated coal ash high adsorption capacity for hydrogen sulfide.

No abstract

Many studies have reported variation in properties of the sediment within electrokinetic treatments (EKTs). However, we aim to reveal the variation in properties of the sediment following EKTs through laboratory experiments. We collected sewage-derived sediment from a littoral region, and passed it through a 2-mm sieve. We used a potentiostat to cause electrical current in EKT. We measured the sediment properties such as pH, redox potential (ORP), and hydrogen sulphide (HS) concentration at the end of EKT and at 30 days following EKT. Results showed decreases in pH, increases in ORP, and decreases in HS concentration at the end of EKT. Compared with the sediment without EKT, the decrease in ORP for the sediment within EKT was higher at 30 days following EKT. These suggest that anaerobic digestion of organic compounds occurs in the sediment following EKT, of which the oxidants produced by EKT serve as electron acceptors and organic compounds serve as electron donors. Furthermore, we found that EKT can remove HS from the sediment and reduce HS production in the sediment within EKT when compared to the case without EKT. These ensure that EKT can be used to remove HS and control HS production in the sediment.