含砷酸性废水中砷的氧化过程研究

研究了含砷酸性废水中As(Ⅲ)的氧化过程,分析了As-H2O系E-p H图,采用电解产生的H2SO5对As(Ⅲ)进行氧化和电解,对硫酸-砷混合体系中的砷进行氧化。试验结果表明,三价砷的氧化电位高于0. 3 V,且低于氧气析出电位,随着pH值的增大,砷的氧化电位逐渐降低。电解电压选取6 V,在此条件下会产生过一硫酸,加入0. 5 g/L硫氰酸铵抑制析氧副反应的发生,提高电流效率。对比了相同条件下单纯利用电解产生的过一硫酸氧化As(Ⅲ)和电解氧化As(Ⅲ)的效果,发现电解氧化As(Ⅲ)的氧化率要高于单纯过一硫酸的氧化率,说明在利用较高电压电解氧化三价砷时,其实质是电化学氧化和电解产生的过一硫酸氧化共同作用的结果。

Study on the Oxidation Process of Arsenic in Acidic Wastewater Containing Arsenic

The oxidation process of As(III) in acidic wastewater containing arsenic was studied. The E-pH diagram of As-H2O was analyzed. The oxidation effects of As(III) oxidized by H2SO5 produced from electrolysis and electrolytic oxidation of arsenic in sulfuric acid - arsenic mixed system were compared. The experimental results show that: the oxidation potential of trivalent arsenic is higher than 0.3V, and it is lower than the oxygen deposition potential. As pH increases, the oxidation potential of arsenic decreases gradually. The experimental electrolysis voltage was selected as 6V. Under this condition, Caro''s acid was generated. The addition of 0.5g/L potassium thiocyanate inhibited the occurrence of oxygen evolution side reactions and improved the current efficiency. Comparing the effect of oxidizing As(III) Caro''s acid produced by electrolysis and under the same conditions the effect of electrolytically oxidizing As(III) at this voltage, It was found that the oxidation rate of electrolytic oxidation As(III) was higher than the oxidation rate of Caro''s acid, indicating that in the case of electrolytic oxidation of trivalent arsenic using a higher voltage, the nature of the oxidation is the combined effect of electrode oxidation and Caro''s acid oxidation produced by electrolysis.