Mining flotation reagents: Quantitative and robust analysis of metal-xanthate complexes in water

Xanthates, common mining flotation reagents, strongly bind thiophilic metals such as copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) and consequentially change their bioavailability and mobility upon their discharge into the environment. However, accurate quantification of the metal-xanthate complexes has remained elusive. This study develops a novel and robust method that realizes the accurate quantification of the metal-xanthate complexes resulted from single and multiple reactions of three typical xanthates (ethyl, isopropyl, and butyl xanthates) and four thiophilic metals (Cu, Pb, Cd, and Zn) in water samples. This method uses sulfur (S^2-) dissociation, followed by tandem solid phase extraction of C₁₈ + PWAX and subsequent LC-MS/MS analysis. It has a wide linearity range (1-1000 μg/L, R² ≥ 0.995), low method detection limits (0.002-0.036 μg/L), and good recoveries (70.6-107.0 %) at 0.01-10 mg/L of xanthates. Applications of this method showed ubiquitous occurrence of the metal-xanthate complexes as the primary species in flotation wastewaters, which the concentrations were 4.6-28.9-fold higher than those previously determined. It is the first quantitative method established for the analysis of metal-xanthate complexes in water samples, which is of great importance to comprehensively understand the fate and risks of xanthates in the environment.