基于碳点变色性能的紫外-可见分光光度法测定脱硫液和废水中硫离子的含量

Determination of Sulfur Ion in Desulfurization Solution and Waste Water by UV-Vis Spectrophotometry Based on Carbon Dots with Discoloration Property

以柠檬酸为碳源,尿素为氮源,采用水热法合成了具有变色性能的碳点(CDs),利用该CDs与S^(2-)的褪色反应,提出了紫外-可见分光光度法(UV-Vis)测定脱硫液和废水中S^(2-)含量的方法。通过循环预处理系统分离样品中的S^(2-),分取0.5 mL待测样品溶液和4.5 mL 100 mg·L^(-1)CDs溶液,混匀,将酸度调节至pH 8,于30℃反应15 min,快速冷却至室温,采用UV-Vis测定反应前后体系在610 nm处的吸光度。结果表明,该CDs变色是氧化导致的。在pH 8条件下,S^(2-)使CDs发生选择性褪色反应;S^(2-)的质量浓度在0.05~1.00 mg·L^(-1)和1.00~15.00 mg·L^(-1)内与对应的吸光度差值呈线性关系,检出限(3S/N)为0.043 mg·L^(-1)和0.073 mg·L^(-1);对实际样品进行加标回收试验,回收率为98.0%~106%,测定值的相对标准偏差(n=6)为0.92%~1.1%。方法用于实际脱硫液和废水样品分析,并与国家标准GB/T 16489-1996进行比对,结果显示两种方法的测定结果无显著性差异。

The carbon dots(CDs)with discoloration property was synthesized by hydrothermal method using citric acid as carbon source and urea as nitrogen source.Based on the discoloring reaction between CDs and S^(2-),a method for the determination of S^(2-)in desulfurization solution and waste water by UV-Vis spectrophotometry was proposed.The cyclic pretreatment system was used to separate S^(2-)from the sample.An aliquot(0.5 mL)of the sample solution for test and 4.5 mL of 100 mg·L^(-1)CDs solution were mixed well,and the acidity was adjusted to pH 8 for reaction at 30℃for 15 min,then the mixed solution was rapidly cooled to room temperature.The absorbance of the system at 610 nm was determined by UV-Vis spectrophotometry before and after the reaction.It was shown that the discoloration of CDs was caused by oxidation,and the selective discoloring reaction of CDs was induced by S^(2-)at pH 8.Linear relationships between values of mass concentration of S^(2-)and corresponding difference of absorbance were kept in the ranges of 0.05-1.00 mg·L^(-1)and 1.00-15.00 mg·L^(-1),with detection limits(3S/N)of 0.043 mg·L^(-1)and 0.073 mg·L^(-1).Test for recovery was made on the actual samples,giving results of in the range of 98.0%-106%,with RSDs(n=6)of the determined values ranged from 0.92%to 1.1%.This method was applied to the analysis of the actual desulfurization solution and waste water samples,and there was no significant difference with GB/T 16489-1996.