H_2O_2-Na_2S_2O_3反应对pH和反应物起始浓度比的依赖性

Dependence of the H_2O_2-Na_2S_2O_3 Reaction on pH and [H_2O_2]_0/[Na_2S_2O_3]_0

在H2O2-Na2S2O3反应体系中,pH值和[H2O2]0/[Na2S2O3]0对反应产物的浓度大小起着关键作用.本文通过考察这两种因素对反应产物的影响,以及对反应机理的模拟,得出了pH值和氧化剂与还原剂浓度比影响反应产物浓度的一般规律.结果表明:pH<3时,反应主要生成单质硫,3<pH<6时,S4O62-较为稳定,提高pH和[H2O2]0/[Na2S2O3】0有利于SO42-生成,在中性或弱碱性溶液中S(Ⅳ)(HSO32-或SO32-)物质浓度出现峰值.

In the H2O2-Na2S2O3 reaction system both the pH value and [H2O2]0/ [Na2S2O3]0 are important factors for stability of different intermediates. In this paper, the influences of the two factors on the composition and stability of the products were investigated. The results show that sulfur(0) is the main productat pH < 3, while tetrathionate is stable only in the pH range between 3 and 6. The concentration of sulfate will increase when pH and [H2O2]0/ [Na2S2O3]0 are getting high. In neutral and week base solutions, the concentration of S(△) species shows a peak value.