Elucidating the decomposition kinetics of xanthate compounds in mining waters by headspace gas chromatrography-mass spectrometry

Xanthates are a widely used class of floatation reagents used for the recovery of valuable sulphide minerals. Floatation utilizes large quantities of water that lead to rapid hydrolysis of xanthates in circuit leading to a reduction in mineral recovery and an overall decrease in mill efficiency. Currently the knowledge on xanthate degradation is sparse with only a few studies reporting kinetic parameters for xanthate degradation into carbon disulphide (CS2). A headspace GC-MS method was developed to directly measure the presence of CS2 in the gas phase. Kinetic parameters were then established for potassium amyl xanthate (PAX), sodium isobutyl xanthate (SIBX), potassium isopropyl xanthate (PIPX), and sodium ethyl xanthate (SEX) based on the generation of CS2. The decomposition of all xanthate studied followed first order kinetics and the rate constants were determined using a 7650A auto sampler and a PAL3 auto sampler. The rate constants were found to be 7.05 x 10-4, 4.07 x 10-4, 5.11 x 10-4, and 1.48 x 10-4 h-1 for PAX, SIBX, PIPX, and SEX respectively at 25 oC using the 7650A auto sampler. For the PAL3 auto sample the rate constants were found to be 3.71 x 10-6, 4.39 x 10-6, 1.86 x 10-6, and 4.03 x 10-6 h-1 for PAX, SIBX, PIPX, and SEX respectively at 30 oC. The rate constants were found to increase as the temperature was increased. These data were used to calculate the activation energies for each decomposition reaction. The activation energies were found to be 19.83, 10.80, 34.44, and 22.64 kJ/mole for PAX, SIBX, PIPX, and SEX respectively. These data show that the methods presented are viable options for further analytical studies on xanthate decomposition kinetics and for higher throughput applications in industrial settings