Measuring heavy metals by quantitative thermal vaporization

It is our vision to separate volatile toxic contaminants from waste by thermal treatment. In this context the evaporation behavior of heavy metal traces (Cd, Cu, Pb, and Zn) from model compounds and mixtures, and from fly ash (FA) of municipal solid waste incineration (BCR No. 176) was investigated. In this study we tested a new method which allows on-line detection of heavy metals in hot gases using conventional Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) equipment. A quantitative relation between the amount of evaporated heavy metal traces and the ICP-OES signal was established. In addition, gaseous HCl was successfully used for the total removal of heavy metal traces from non-volatile compounds. The evaporation behavior predicted by speciation calculations were in agreement with the experimental results. The experiments have shown that the method could become a complementary tool for common analytical digestion and measuring methods for the determination of heavy metal traces in solid samples. As our method combines extraction and analytical steps it therefore can shorten conventional procedures. It allows simultaneous, and compared to a conventional digestion and ICP-OES analysis, more sensitive measurements of several elements. The application could become especially powerful for the analysis of contaminated soil and waste residuals.