基于全反射X射线荧光光谱测定污水痕量重金属元素

Determination of Trace Heavy Metal Elements in Sewage by Total Reflection X-Ray Fluorescence Spectrometry

以Ga为内标,探究全反射X射线荧光光谱(TXRF)快速测定多质量梯度浓度多元素重金属溶液Mn、Fe、Co、Ni、Cu、Zn、As、Cd、Sn、Sb和Pb的可行性,并以实际生活污水为研究对象,比较分析了离心、过滤和消解3种预处理方式对测定污水中重金属元素的影响。实验结果表明,Mn、Fe、Co、Ni、Cu、Zn、As和Pb,较适宜用TXRF直接进行定量分析;Pb的Lα与As的Kα谱线重叠,致使As的回收率略高于其它元素;Cd、Sn和Sb元素,仅可用于趋势分析。当质量浓度为40和4 mg/L时,Mn、Fe、Co、Ni、Cu、Zn和Pb元素呈现出较高的准确度和精密度,回收率在99%~117%之间,相对标准偏差(RSD)处于1%~14%。随着质量浓度的逐渐降低,各元素的准确度和精密度表现出不同程度的下降,当质量浓度处于本次试验的最低水平4μg/L时,大部分元素的回收率与RSD已超出定量分析的要求。通过对生活污水的3种预处理方式进行比较,发现污水悬浮颗粒同样携带部分金属元素,经消解后,Mn、Fe、Co、Ni、Cu和Zn这6种元素的准确度和精密度最好,质量浓度范围在36~152μg/L之间,回收率均高于95%,RSD低于5%。综上所述,TXRF可直接对污水样品中的重金属元素进行快速的定性、定量分析,其精确度和准确度在很大程度上取决于元素种类、样品制备程序和待测元素的质量浓度,对于质量浓度低的样品可结合预浓缩技术以提高测量准确率。

In this work,Ga is used as the internal standard to explore the feasibility of rapid determination of multi-mass concentration gradient of multi-element heavy metal solution by Total Reflection X-ray Fluorescence(TXRF)Spectrometry,e.g.Mn,Fe,Co,Ni,Cu,Zn,As,Cd,Sn,Sb,and Pb,and the effects of three pretreatment methods on the determination of heavy metal elements in actual domestic sewage are compared and analyzed.The experimental results show Mn,Fe,Co,Ni,Cu,Zn,As,Pb are more suitable for the direct analysis with TXRF;Overlapping of LαLine of Pb and KαLine of As results in a slightly higher recovery of As than other elements,which does not affect Pb;Cd,Sn and Sb can be used for trend analysis because the recovery and precision can not meet the quantitative requirements in most cases.When the mass concentrations are 40 and 4 mg/L,Mn,Fe,Co,Ni,Cu,Zn and Pb show high accuracy and precision.The recovery rates are 99%~117%and the RSDs are between 1.4%~2.7%.With the gradual decrease of concentration,the accuracy and precision of each element decreases.When the mass concentration is at the lowest level of 4μg/L in this experiment,the recovery rate and RSD of most element exceed the required range.Through the comparison of three pretreatment methods,it is found that the concentration of each element in the sewage after centrifugation and filter membrane filtration and is significantly lower than that of raw water and acid digestion water samples,and the raw water is slightly lower than that of acid digestion water samples,which indicates that the heavy suspended particles of sewage also carry some metal elements.After digestion,the accuracy and precision of the six elements Mn,Fe,Co,Ni,Cu and Zn are the best.The concentration range is 36~152μg/L,and the recovery rates are higher than 95%with RSD lower than 5%.In summary,TXRF can directly achieve rapid and accurate quantitative analysis of sewage samples,and its accuracy and accuracy depend largely on the type of elements,sample preparation procedures and the concentration of elements to be measured.For low concentration samples,preconcentration technology can be combined to improve the accuracy.