以氢氧化钠和硫化钠为沉淀剂采用共沉淀法同时富集水体中的Cr, Cd和Pb, 通过对Cr(OH)3, Cd(OH)2和PbS沉淀均匀悬浮液抽滤以制成Cr, Cd和Pb均匀分布的薄膜样品并进行能量色散XRF光谱测量, 以实现水体中Cr, Cd和Pb的同时快速分析与检测。 研究了富集过程中的反应时间和反应物摩尔比对薄膜样品XRF光谱强度的影响, 确定了富集过程的最佳反应条件为沉淀反应时间为5 min, OH-与Cr3+的最佳摩尔比为50, OH-与Cd2+的最佳摩尔比为50, S2-与Pb2+的最佳摩尔比为2; 对富集后不同浓度的薄膜样品进行了均匀性检验, 富集区域6个不同位置荧光强度的相对标准偏差均小于48%, 说明富集后的薄膜样品具有较好的均匀性; 将不同浓度薄膜样品的理论浓度值与ICP-MS方法测得的浓度值进行对比分析, 验证了该富集方法对水样中Cr, Cd和Pb的富集率均能达到90%以上; 根据薄膜样品的荧光强度与ICP-MS测得的浓度值, 建立了基于该富集方法的水体中Cr, Cd和Pb的X射线荧光光谱定量分析方法, Cr, Cd和Pb校准曲线的线性相关系数分别为0997 3, 0995 0和0999 8, 当实际采集水样体积为50 mL时, Cr, Cd和Pb的检出限分别为74, 296和85 μg·L-1, 均低于《污水综合排放标准 GB 8978—1996》中Cr, Cd和Pb的最高允许排放浓度, 因此该方法能够实现工业生产及生活排放污水中Cr, Cd和Pb的同时快速分析与检测。 该研究为基于X射线荧光光谱法的水体多种重金属同时快速在线监测提供依据。

Coprecipitation method was adopted for simultaneous enrichment Cr, Cd and Pb in water by using sodium hydroxide and sodium sulfide as precipitant. The precipitation homogeneous suspension of Cr(OH)3, Cd(OH)2 and PbS was filtered to prepare uniform Cr, Cd and Pb thin film samples. The energy dispersive XRF spectra of thin film samples were measured in order to realize simultaneous and rapid analysis and determination of Cr, Cd and Pb in water. The influence of reaction time and molar ratio of reactants in the process of enrichment to the XRF spectrum intensity of thin film samples was studied. The precipitation reaction time for 5 min, the best mole ratios of OH- with Cr3+ for 50, OH- with Cd2+ for 50, and S2- with Pb2+ for 20 were the optimum reaction conditions. The homogeneity of thin film samples with different concentrations after enrichment was tested. All the relative standard deviations of fluorescence intensity at six different positions at enrichment area were less than 48%, which indicates that all the thin film samples are in good uniformity. The theoretical concentration of thin film samples with different concentrations was compared with measured concentration with ICP-MS method, which confirms that the enrichment rate of this enrichment method for Cr, Cd and Pb in water can reach more than 90%. According to the fluorescence intensity of the thin film samples and the concentration measurements with ICP-MS, the quantitative analysis method of X-ray fluorescence spectrum for Cr, Cd and Pb in water based on the above enrichment was established. The linear correlation coefficients of Cr, Cd and Pb calibration curve were 0997 3, 0995 0 and 0999 8, respectively. When the volume of actually collecting water sample for 50ml, the detection limits of Cr, Cd and Pb were 74, 296 and 85 μg·L-1, respectively. All the detection limits are lower than the maximum allowable emission concentration of Cr, Cd and Pb in (Integrated wastewater discharge standard GB 8978—1996). So this method can realize the simultaneous and rapid analysis and determination of Cr, Cd and Pb in the discharged wastewater of industrial production and life. This study provides a basis for simultaneous and rapid on-line monitoring of a variety of heavy metals in water for X-ray fluorescence spectrometry.