Analysis of Toxic Trace Elements in Wastewater

Introduction

Toxic elements such as Cd, As, Pb are contained in the wastewater drained from industrial factories. Organic and inorganic components in wastewater cause physical interference in induced coupled plasma optical emission spectrometry (ICP-OES) analysis. Therefore, acid decomposition or desalting processes of matrix components in wastewater are needed in ICP-OES analysis. On the other hand, total reflection X-ray fluorescence (TXRF) analysis has an advantage in that there is less effect of matrix components compared to ICP-OES. In this report, the analysis of toxic trace elements in wastewater by TXRF is introduced.  

Measurement and results

Analytical results of undiluted and 100-fold diluted aliquots of the 140-025-037 EnvironMAT wastewater reference material supplied from SCP SCIENCE are shown in Figure 1. The analytical values show good agreement with standard values in both concentration levels of undiluted and diluted aliquots for 140-025-037. Lower limits of detection (LLDs) calculated from both samples are shown in Table 1. The LLDs in the diluted solution are  lower than those of the undiluted sample. The TXRF spectrum of undiluted solution with added Ag as internal standard from 21 to 24 keV is shown in Figure 2.

In NANOHUNTER II, K-lines of elements with high energies can be excited efficiently by using a double-stacked multilayer mirror. Therefore, Ag-Kα and Cd-Kα can be observed clearly. LLD of Cd in the diluted sample was 6.3 µg/L, which is lower than the standard value of wastewater. A TXRF spectrometer can be applied as analysis method of wastewater and components with wide concentration ranges from parts per billion to parts per million without special sample preparation. 

Figure 1:  Correlation graph between standard and analytical values of all elements for 140-025-037 EnvironMAT wastewater reference material 

Figure 2:  TXRF spectrum of 140-025-037 EnvironMAT wastewater reference material in high-energy range (undiluted sample) 

Table 1: LLDs of harmful elements in 140-025-037 EnvironMAT wastewater reference material, Diluted 100 times