光度滴定在线分析系统测定锌电解液中硫酸及锌离子含量

Determination of sulfuric acid and zinc ion content in zinc electrolyte by photometric titration on⁃line analysis system

锌电解液中硫酸和锌离子含量直接影响到锌的纯度及产品质量,目前电解液中硫酸和锌离子含量的检测均依赖于离线检测,自动化程度较低,联合测定装置的研究应用较少。本文对光度滴定在线检测系统进行了介绍,并通过优化检测参数,利用吸光度突变对硫酸和锌离子含量进行测定。在取样速度为30 mL/min、取液后等待时间2 s的条件下,可保证样品取样精度;锌离子测定采用EDTA络合滴定,以二甲酚橙作为指示剂,用量为0.2 mL,六次甲基四胺缓冲溶液用量为50 mL,在525 nm波长下对锌离子测定;硫酸测定采用酸碱滴定,以甲基红-次甲基蓝指示剂,用量为0.2 mL,控制在420 nm波长下测定,通过指示剂颜色变化判定滴定终点。试验结果表明,以优化后的试验条件运行,利用光度传感器采集信号,根据吸光度突变判定滴定终点方法可行,试验中分别对标准样品进行稳定性测试,实际值与认定值基本相符,表明装置及方法准确可靠,按照方法进行实际样品精密度(n=7)及加标回收率测试,并对比人工离线检测,其精密度整体RSD<1.2%,加标回收率分别为98.4%~101%和99.1%~99.8%。使用t检验证明,仪器测试结果与人工检测并无差异性,该装置可实现自动化分析,操作简单,分析项目同时进行,可满足在线连续生产检测需求。

The content of sulfuric acid and zinc ion in zinc electrolyte directly affects the purity and product quality of zinc.At present,the detection of sulfuric acid and zinc ion content in electrolyte depends on offline detection,the degree of automation is low,and the research and application of combined determination device is less.In this paper,the photometric titration on⁃line analysis system is introduced,and the content of sulfuric acid and zinc ion is determined by optimizing the detection parameters and the absorbance mutation.Under the conditions of sampling speed of 30 mL/min and waiting time of 2 s after liquid extraction,the sampling accuracy of the sample can be guaranteed.Zinc ion was determined by EDTA complexometric titration,with xylenol orange as the indicator,the amount of 0.2 mL,the amount of hexamethylenetetramine buffer solution was 50 mL,and the zinc ion was determined at the wavelength of 525 nm.Sulfuric acid was determined by acid⁃base titration with methyl red⁃methylene blue indicator at a dosage of 0.2 mL,and the wavelength was controlled at 420 nm.The titration end point was determined by the color change of the indicator.The results showed that it was feasible to determine the titration end point according to the absorbance mutation by using the photometric sensor to collect the signal under the optimized experimental conditions.The stability test of the standard sample was carried out in the experiment,and the actual value was basically consistent with the identified value,indicating that the device and method were accurate and reliable.According to the method,the precision of the actual sample(n=7)and the recovery rate of the standard addition were tested and compared with the manual off⁃line detection.The overall RSD of the precision was less than 1.2%,and the recovery rate of the standard addition was 98.4%~101%and 99.1%~99.8%,respectively.The t test proves that there is no difference between the instrument test results and the manual test.The device can realize automatic analysis,simple operation,and the analysis items are carried out at the same time,which can meet the needs of online continuous production detection.