溴酸钾氧化甲基绿褪色催化动力学光度法测定痕量铅  

Determination of trace lead by catalytic kinetic spectrophotometry based on fading of methyl green oxidized by potassium bromate

作　　者：张悦 刘斌[1] 杨荟茜 杜燕萍[1] 常薇[1] ZHANG Yue;LIU Bin;YANG Huixi;DU Yanping;CHANG Wei(Xi′an Key Laboratory of Textile Chemical Engineering Auxiliaries,School of Environmental and Chemical Engineering,Xi′an Polytechnic University,Xi′an 710600,China)

机构地区：[1]西安市纺织化工助剂重点实验室,西安工程大学环境与化学工程学院,陕西西安710600

出　　处：《冶金分析》2021年第9期91-95,共5页Metallurgical Analysis

基　　金：国家自然科学基金(21703165);陕西省科技计划项目(2018GY-131)。

摘　　要：在盐酸介质中,氧化剂溴酸钾可氧化甲基绿褪色使其吸光度下降,铅离子对该反应有催化作用,据此,建立了溴酸钾氧化甲基绿褪色催化动力学光度法测定痕量铅的方法。取两支相同规格的具塞玻璃比色管,一支加入2.1mL甲基绿溶液、1.0mL盐酸、0.9mL溴酸钾溶液、一定量铅标准溶液;另一支做空白对照,不加铅溶液。于100℃沸水浴反应10min后,用紫外可见分光光度计分别测定催化体系(含铅)和非催化反应体系(不含铅)在最大波长631nm处的吸光度,计算吸光度差值。结果表明,在0.004~0.12μg/mL范围内,铅质量浓度与吸光度差值有良好的线性关系,相关系数r=0.999 7。催化反应的速率常数为3.5×10^(-1)s^(-1),表观活化能为11.99kJ/mol;方法检出限为2.8×10^(-3)μg/mL,方法定量限为9.5×10^(-3)μg/mL。将实验方法应用于测定生活污水和印染废水中铅,结果的相对标准偏差(RSD,n=6)为1.6%~3.6%,测得结果与原子吸收光谱法基本一致,加标回收率为95%~108%。In the medium of hydrochloric acid,the oxidant of potassium bromate could oxidize methyl green to fade and decrease its absorbance.Lead ions could catalyze the reaction.Based on this,a determination of trace lead was established by catalytic kinetic spectrophotometry based on the fading reaction of methyl green oxidized by potassium bromate.Two stoppered glass colorimetric tubes of the same specification were taken.One was added with 2.1 mL methyl green solution,1.0 mL hydrochloric acid,0.9 mL potassium bromate solution,and a certain amount of lead standard solution,the other was a blank control without lead solution.After reacting in a boiling water bath at 100℃for 10 min,the absorbance of the catalytic system(with lead)and the non-catalytic reaction system(without lead)at the maximum wavelength of 631 nm were determined with an ultraviolet-visible spectrophotometer,and the difference in absorbance was calculated.The results showed that,the lead mass concentration within the range of 0.004-0.12μg/mL had a good linear relationship with the difference in absorbance,and the correlation coefficient was r=0.999 7.The rate constant of the catalytic reaction was 3.5×10^(-1)s^(-1),the apparent activation energy was11.99 kJ/mol;the limit of detection for the method was 2.8×10^(-3)μg/mL,and the limit of quantification was 9.5×10^(-3)μg/mL.The experimental method was applied to the determination of lead in domestic sewage and wastewater of printing and dyeing.The relative standard deviation(RSDs,n=6)of the results were 1.6%-3.6%.The results are basically consistent with atomic absorption spectrometry,and the recoveries were 95%-108%.

关 键 词：催化动力学光度法 铅 溴酸钾 甲基绿 

分 类 号：O657.32[理学—分析化学]