THE FLOTATION OF PYRITE USING MIXTURES OF DITHIOCARBAMATES AND OTHER THIOL COLLECTORS

This paper presents results which show that when mixtures of dithiocar bamates are used to float pyrite each component has a synergistic effe ct on the performance of the others. In particular cyclo-hexyl dithioc arbamate which produced the lowest recovery when used as a pure collec tor had a significantly advantageous effect on recovery and grade when mixed in small quantities with another dithiocarbamate. Different mol ar ratios of cyclo-hexyl (oC6) and di-n-propyl (di-n-C3) dithiocarbama tes (DTC) in the mixtures were tested. In all cases 90:10 and 10:90 mi xtures produced higher recoveries and grades than did 50:50 mixtures o r the pure components. Recoveries increased from 74.0% for pure oC6 DT C and 83.5% for pure di-n-C3 DTC to 89.5% for the 90:10 mixture. Grade s increased from 14.5% for pure oC6 DTC and 18.5% for pure di-n-C3 DTC to 20.5% for the 50:50 mixture. The effect of mixtures was less marke d at higher dosages indicating that for the same performance lower dos ages of mixtures were required compared to those required by the pure components. The mixtures resulted in faster rates of flotation as well as a greater recovery of coarse particles. Increased recoveries and g rades were obtained in the first minute due to an enhancenment in the rate of flotation. When mixtures were used the p50 of the concentrate increased showing that coarser material was collected. This effect was greater in the first concentrate than the final concentrate. Mixtures of dithiocarbamates and other thiol collectors, viz. xanthate, sodium mercaptobenzothiazole and dithiophosphate further enhanced recoveries and grades to a maximum recovery of 96.0% and grade of 21.0% for a mi xture of 90% potassium n-butyl xanthate (PNBX) and 10% oC6 DTC. The me thod (premixing or separate) and sequence of collector addition had li ttle effect on recoveries or grades. The effect of copper sulphate add ition varied. In the case of cyclo-hexyl dithiocarbamate, the addition of copper sulphate dramatically reduced recoveries and grades but whe n other collectors were present this did not occur. Generally the addi tion of copper sulphate slightly enhanced recoveries and grades and gr eatly enhanced water recoveries probably due to a froth stabilization effect.