ABSTRACT

Hexavalent chromium (VI) is a potent carcinogen for humans, while trivalent chromium (III) is an important element in glucose metabolism. In atmospheric water droplets, oxidation of Cr(III) to Cr(VI) by free radicals is a major environmental issue. Laboratory simulation studies of the aqueous phase oxidation-reduction of the couple Cr(III)/Cr(VI) by OH^• and HO₂^•/O₂^•− by applying conductometric pulse radiolysis techniques were carried out in the pH range 3.5–5.5 chosen as characteristic values of atmospheric water droplets acidity. A pK_a of 3.9 was found for the first hydrolysis of Cr(IV). The bimolecular second-order decay of the Cr(V) transient species shows a strong pH dependency consequence of the change of the coordination sphere of the tetrahedral Cr(VI) to the octahedral Cr(III).

摘要

六价铬 (VI) 是一种对人类的强致癌物，而三价铬 (III) 是葡萄糖代谢中的重要元素。在大气水滴中，自由基将 Cr(III) 氧化为 Cr(VI) 是一个主要的环境问题。通过应用电导脉冲辐解技术，在 3.5-5.5 的 pH 值范围内进行了OH ^•和 HO ₂ ^• /O ₂ ^•-对 Cr(III)/Cr(VI) 水相氧化还原的实验室模拟研究被选为大气水滴酸度的特征值。A p K _a发现 Cr(IV) 的第一次水解为 3.9。Cr(V) 瞬态物质的双分子二阶衰变显示出四面体 Cr(VI) 的配位球变化为八面体 Cr(III) 的强 pH 依赖性结果。