P10 超音波による酸化作用を利用した廃水中のセレンおよびヒ素の除去

抄録

Selenium (Se(IV), Se(VI)) and arsenic (As(III), As(V)) are toxicity for human body. Therefore, it is necessary to remove these ions from solutions to adsorbents before discharge. To remove selenium and arsenic, oxidation treatment is important. Because Se(VI) and As(V) are lower toxicity than Se(IV) and As(III), respectively. It is well known that the ratio of As removal using iron hydroxide is much higher for As(V) than that for As(III). Therefore, it is crucial to efficiently oxidize As(III) to As(V). On other hand, the main removal method of Se is adsorption of Se(IV) reduced from Se(VI) onto Fe(OH)₃. There are only few reports to treat Se by oxidation method. Therefore, oxidation of Se(IV) using ultrasound irradiation and adsorption of Se(VI) using synthesized maghemite (γ-Fe₂O₃) were studied. We also studied oxidation of As(III) using ultrasound irradiation. Oxidation ratio of As(III) to As(V) showed 100 % for 60 min irradiation. However, oxidation ratio of Se(IV) to Se(VI) showed only 4 % for 60 min irradiation. Finally, we evaluated adsorption capacity of synthesized maghemite. It could adsorb 99.4 % of Se(VI) in the solution (10 ppm, pH 2.0).