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• 基金项目：

• 王立军
• 中国科学院地理研究所

• 章申
• 中国科学院地理研究所

• 王勤生
• 浙江大学地质系

• 朱扬明
• 浙江大学地质系

• 摘要：本文模拟研究了地表水及土壤水介质中Cr(Ⅵ)在硫系统作用下的氧化还原反应动力学.在通常的pH及夏、秋温度和厌氧还原条件下进行动力学实验,采用了流动注射技术分析测定.初步确定了在一定的温度及pH条件下,当Cr(Ⅵ)与硫化物浓度相近时,二者之间的氧化还原反应为二级反应,其反应速率与Cr(Ⅵ)及总硫化物浓度的一次方乘积成正比.其速率常数随温度升高而增大,随pH升高却产生较为复杂的变化,总的说来,在pH5.5-7.0范围内速率常数较大.而在pH>7时反应很慢,近于停止了.当硫化物浓度远大于Cr(Ⅵ)时,二者之间的反应为准一级反应,Cr(Ⅵ)的还原速率与Cr(Ⅵ)浓度的一次方成正比,其反应速率常数随温度升高而增大,在pH5.0-7.8范围内速率常数随pH升高而逐渐减小.

• Abstract：This paper is written on investigation of redox reaction kinetics between Cr(Ⅵ) and ΣS^2-- in natural waters under ambient temperature and pH and anaerobic condition. Results obtained are summarized as follows:1. Cr(Ⅵ)-ΣS^2-- reaction is of second-order, according to experimental data, which so demonstrate by integral diagrammatic method.2. Rate expression for Cr (Ⅵ)-ΣS^2-- reaction is of the form,v=-dc/dt=K ·C_cr(vI)·C_ΣS^2- 3. Both solution temperature and pH value have significant effect on Cr(Ⅵ)-ΣS^2--reaction rate. Curve of K vs. T and that of K vs. pH value were plotted through integral diagrammatic method. Plot of K-T illustrates that K increases as increasing of the temperature. K-pH plot illustrates that changes of K are in a more complicated manner increasing with pH. The largest value of K occurs when pH is between 6.0 and 6.5, and the rate changes slowly or even comes to stop as pH>7.This kinetic equation is found useful under anaerobic environment where PH<7.

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