塩水電解による塩素酸及び過塩素酸の生成特性と電極材質に関する検討

摘要

塩水電解における次亜塩素酸の生成における塩素酸，過塩素酸の特性を把握するための検討を行った。6種類の異なる電極(主たる成分A:RuO_2-TiO_2,B:RuO_2-IrO_2-TiO_2,C:IrO_2-SnO_2,D:IrO_2-Pt，E:Pt,F:PbO_2)を用いて塩水電解を行ったところ，生成装置の電極の材質により反応時の電位が異なり，次亜塩素酸の生成にともなって生成する塩素酸，過塩素酸の生成量が異なることが分かった。電流値が一定の条件では，端子間電圧が高い電極で電圧が高く,塩素（次亜塩素酸）の生成量が少なく，塩素酸,過塩素酸の生成量が多くなった。特に，白金電極（E)や二酸化鉛電極（F)において，次亜塩素酸あたりの過塩素酸の生成が顕著であった。電解における電位の違いにより，塩素酸，過塩素酸の濃度が高くなるため，次亜塩素酸を生成する工程，工場における電解等でも注意が必要である。%Chlorate and perchlorate are oxidized substances of chloride, and they exist in the form of anions in water and toxic contaminants that should be controlled, especially in drinking water. To control and minimize the formation of perchlorate in the water purification process, the formation of chlorate and perchlorate in chlorine generation process was studied in electrolysis of salt water. Six electrodes with different properties (main components: A: RuO_2-TiO_2; B: RuO_2-IrO_2-TiO_2; C: IrO_2-SnO_2; D: IrO_2-Pt; E: Pt; and F: PbO_2) were tested. Electric voltage differed among electrodes and the generation of chlorate and perchlorate depended on their electric voltage. When electric current is constant, those electrodes of higher terminal voltage generally showed lower production of chlorine and higher generation of chlorate and perchlorate. It is noted the electrodes, E: Pt and F: PbO_2 are prominent in the generation of chlorate and perchlorate. Therefore, the generation of chlorate and perchlorate should be controlled with the consideration of electrode material, the especially in on-site generation of hypochlorite, industrial electrolysis, water purification devices, and hypochlorite generation devices that involve electrolysis.