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研究报告

摘要：研究了在紫外光照射下,Fe(Ⅲ)-柠檬酸盐溶液对Cr(Ⅵ)的光还原反应.同时,考察了溶液pH值、Fe(Ⅲ)浓度、柠檬酸盐浓度、Cr(Ⅵ)初始浓度对光还原效率的影响,并分析了光还原反应的动力学.研究结果表明, Fe(Ⅲ)-柠檬酸盐体系能光还原Cr(Ⅵ),在pH为2.0~6.0的范围内,Cr(Ⅵ)的还原率随着溶液初始pH值的降低而增大.当pH值为2.0、Fe(Ⅲ)浓度为10 μmol·L^-1、柠檬酸盐浓度为250 μmol·L^-1及Cr(Ⅵ)初始浓度为19.2 μmol·L^-1时,光照反应8 min后Cr(Ⅵ)的最大还原率达到100%,但当pH值增加到6.0时,Cr(Ⅵ)的最大还原率下降到19%;当Cr(Ⅵ)的初始浓度在9.6~96.0 μmol·L^-1的范围内时, Cr(Ⅵ)光还原反应的初始速率随着Fe(Ⅲ)、柠檬酸盐(cit^3-)、Cr(Ⅵ)初始浓度的增加而增加.表观动力学方程为:-dC_Cr_(Ⅵ)/dt=0.1019 ^0.53 ^0.6 ^0.25.

Abstract：The photoreduction of chromium(Ⅵ) in aqueous solutions in the presence of Fe(Ⅲ)-citrate complexes was investigated with an irradiation of UV in the present study. The effects of initial pH value, initial concentrations of Fe(Ⅲ), citrate, and Cr(Ⅵ) on the photoreduction efficiency, and the kinetic curve of photoreduction were preliminarily studied and analyzed. The results showed that the photoreduction of Cr(Ⅵ) could occur in the iron(Ⅲ)- citrate complexes system. The photo-reduction efficiency of Cr(Ⅵ) increased with the decreasing of pH value of the simulated solution in the range of 2.0~6.0, and it reached up to 100% reduction after 8 min reaction in the case of pH value of 2.0, 10 μmol·L^-1 of Fe(Ⅲ), 250 μmol·L^-1 of citrate, and 19.2 μmol·L^-1 of Cr(Ⅵ). However, it would drop to 19% with pH value of 6.0. The increase of the initial concentrations of Fe(Ⅲ), citrate, and Cr(Ⅵ) in a certain range was favorable for the initial photoreduction rates of Cr(Ⅵ) with the increasing of its initial concentration from 9.0 to 96.0 μmol·L^-1. The apparent kinetic curve of the photoreduction of Cr(Ⅵ) could be expressed by the following equation: -dC_Cr_(Ⅵ₎/dt=0.1019 ^0.53 ^0.6 ^0.25.