用萃取-分光光度法测定电镀废水中的铬(Ⅵ)  

Determination of Trace Chromium(Ⅵ) in Electroplating Wastewater by Extraction-Spectrophotometry

作　　者：罗道成[1] 郑李辉[1] 

机构地区：[1]湖南科技大学化学化工学院,湖南湘潭411201

出　　处：《材料保护》2009年第10期75-76,79,共3页Materials Protection

摘　　要：电镀废水中的铬是水质污染的重要监控指标，建立其快速准确的测定方法很有意义。在pH=1．5的NaCl-HCl缓冲溶液中，常温下，铬（Ⅵ）与二苯偶氮羰酰肼（DPCO）反应生成1：2稳定的配合物，在NH4Cl的作用下，该配合物中的铬（Ⅵ）可被聚乙二醇（PEG）相全部萃取。据此建立了测定痕量铬（VI）的萃取光度新方法。试验显示，在PEG相中配合物的最大吸收波长为550nm，铬（VI）含量在0—2．5mg／L内符合比尔定律，方法的表观摩尔吸光系数为3．18×10^4L／（mol·cm），多数常见离子不干扰测定。该方法用于测定电镀废水中的微量铬（Ⅵ），结果与滴定法相符，6次测定值相对标准偏差〈3％，结果令人满意。A new extraction spectrophotometric method,based on the reaction of chromium ( Ⅵ) with diphenvlcarbazone (DPCO) at room temperature in NaCl-HCl buffer solution with a pH vulue of 1.5 forming a stable 1: 2 complex and the complete extraction of the Cr ( Ⅵ)-DPCO complex by polyethylene glycol (PEG) -NH.C1, was established to determine trace chromium ( Ⅵ) in electroplating wastewater.Results show that the maximum absorption wavelength of the complex in PEG is located at 550 urn, and Beer' s law is obeyed in a ranee of 0～ 2.5 mg/L for Cr( Ⅵ).The apparent molar absorptivity was recorded as 3.18 x 10 L/( mol·cm) , and most of common ions had no interference to the determination of chromium ( Ⅵ).The established method was applied to determine trace chromium ( Ⅵ) in electroplating wastewater and was found to be satisfactorily applicable.Namely,the results based on the present method are in good agreement with those provided by titration method, and the relative standard deviation of six repeat test is below 3%.

关 键 词：铬(Ⅵ) 测定 萃取光度法 二苯偶氮羰酰肼 聚乙二醇 

分 类 号：O657.32[理学—分析化学]