Modulation of xanthate action by sulphite ions in pyrrhotite deactivation/depression

Interactions of sulphite ions (introduced via sodium metabisulphite, SMBS), butyl xanthate and triethylenetetramine (TETA) in a pyrrhotite suspension have been investigated. Using UV spectroscopic analysis, the butyl xanthate has been found to adsorb on pyrrhotite to form estimated 1.3 to 3.1 equivalent monolayers at initial concentrations of 5 to 10 ppm, respectively. SMBS is found to be capable of decomposing xanthate to carbon disulphide in pyrrhotite suspension bringing the number of equivalent monolayer down to less than 0.5. A highly significant level of xanthate elimination in the pyrrhotite slurry has been observed. The same phenomenon has also been observed in the presence of TETA as an effective chelator for metal ions suspected of inadvertent activation. Under such conditions, dixanthogen cannot form on pyrrhotite as a sustainable hydrophobic species. TETA itself also appears to be reactive towards xanthated pyrrhotite surface causing release of sequestered surface species into the aqueous phase. However, this effect is not destructive for xanthate and the results suggest re-adsorption of the released species in time. It is concluded that the modulating effect exerted on xanthate as a collector and on potential metal ion activity is a critical part of the joint action of the sulphite ions and polyamines, respectively.