玫瑰桃红R褪色光度法测定电镀废水中的铬(Ⅵ)

Determination of chromium(Ⅵ) in electroplating wastewater by Bordeaux-R fading spectrophotometry

在0.5mol/LH2SO4介质中,玫瑰桃红R(Bordeaux-R)能与铬(Ⅵ)发生氧化褪色反应,据此建立了新的测定微量铬(Ⅵ)的光度法。结果表明,在实验条件下,褪色后体系的最大吸收波长为520nm,表观摩尔吸光系数为1.78×104L/(mol.cm)。铬(Ⅵ)质量浓度在0～8.0mg/L内符合比尔定律,该法用于测定电镀废水中微量铬(Ⅵ),结果与滴定法相符,6次测定值RSD<3%。

A new spectrophotometric method for the determination of micro-chromium（Ⅵ ） has been developed. It is based on the effect of the oxidation fading reaction of Bordeaux-R with chromium（Ⅵ ） in a medium of sulfuric acid with a concentration of 0.5 mol/L. The results show that after the fading, the maximum absorption wave length of the system is 520 nm and its apparent molar absorption coefficient is 1.78×10^4 L/（mol .cm） under this experimental conditions. When the mass concentration of chromium （Ⅵ） is in the range of 0-8.0 mg/L it accords with Beer＇s law. This method has been applied to the determination of micro-chromium （ Ⅵ ） in eleetroplating wastewater, and its results are in good agreement with those provided by titration method with precision of 〈3% RSD （n=6）.