Quantification of Xanthates Chemisorbed on Solid Mining Wastes by Evolved Gas Analysis Hyphenation Techniques

The site of a former copper mine, in the process of being decontaminated, needed to be screened for xanthates contamination. It is known that potassium amyl xanthate as well as potassium ethyl xanthate were used in flotation process as collectors during the operation of the mine. The use of common analytical methods for organic contaminants, based on solvent extraction, showed no detectable xanthates contamination. As xanthates are strongly adsorbed on some mineral surfaces in the flotation process of the mineral-rich ore, it was suspected that common analytical methods can’t be applied to such situation. Even the use of acidic media with headspace gas chromatography was not able to detect any significant volatile decomposition products from xanthate-spiked soil samples. Then, thermal decomposition of the surface-bounded contamination, followed by an analysis of the generated vapour, showed significant results. A hyphenated system, composed of a thermogravimetric analyzer, an infrared spectrophotometer and a gas phase chromatograph coupled with a mass spectrometer was ultimately considered. With this multi-instrumental system, an analytical method has been developed and it was found that the xanthate contamination was well over 1 ppm for many samples taken from the former mining site. This article will describe the analytical method that was developed on this hyphenated system to detect, quantify and identify xanthates in environmental samples.