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环境化学

摘要：为了探索Fe³⁺催化氧化S(Ⅳ)的反应动力学规律,实验考察了pH、Fe³⁺浓度、S(Ⅳ)浓度、温度对反应动力学的影响.结果表明,Fe³⁺催化氧化S(Ⅳ)过程中动力学控制步骤为Fe²⁺的氧化,且pH在0～3范围内,氧化速率随着H+浓度的升高而降低;Fe³⁺浓度为0～0.01mol·L^-1时,氧化速率随Fe³⁺浓度的增加而加快,继续增加Fe³⁺浓度,氧化速率没有明显变化;S(Ⅳ)浓度为0～0.1mol·L^-1时,氧化速率随S(Ⅳ)浓度的增加而加快.由实验数据得到了氧化速率公式.反应速率在20～40℃范围内随温度升高而加快,反应活化能约为13kJ·mol^-1.在实验基础上推测反应为自由基链反应机理.

Abstract：The effect of pH, concentration of Fe³⁺ and S(Ⅳ)and temperature on the kinetics of Fe (Ⅲ) catalyzed oxidation of S(Ⅳ) is presented in the present work. The oxidation of Fe²⁺ was the rate-determining step in the Fe³⁺ catalyzed oxidation of S(Ⅳ). The rate of Fe²⁺ oxidation decreased with increasing concentration of H+ when the pHof the solution was within the range of 0～3, while the rate of Fe²⁺ oxidation increased with increasing concentration of Fe³⁺ within the range of 0～0.01 mol·L^-1. The oxidation rate did not change significantly at higher concentrations of Fe³⁺. The rate of Fe²⁺ oxidation increased with the increasing concentration of S(Ⅳ)within the range 0～0.1 mol·L^-1. The rate of Fe²⁺ oxidation was first order with respect to Fe³⁺ concentration and S(Ⅳ) concentration according to the experimental data. The oxidation rate increased with temperature from 20 to 40℃, and had an activation energy of 13 kJ·mol^-1. The mechanism of Fe (Ⅲ) catalyzed oxidation of S(Ⅳ), a radical chain reaction, is described.