Evaluating the performance of new collectors on feed to Nkana concentrator's flotation circuit

Nkana Concentrator of Zambia Consolidated Copper Mines (ZCCM) treats copper-cobalt sulphide ore using a bulk flotation and segregation flotation flowsheet to produce separate copper and cobalt concentrates.Recently, in an effort to increase mineral recovery as well as improve copper/cobalt separation, various alternative collectors have been considered as replacement for Sodium Ethyl Xanthate (SEX) which has been used for more than 30 years. Three such collectors that were evaluated are Senkol 26, a Xanthic ester, Senkol 45, a blend of alkyl dithiophosphate and Xanthates and Senkol 700, a thionocarbomate type, which were supplied by SENMIN of South Africa.In this work a series of laboratory testworks were conducted on Nkana Concentrator feed materials from four different sources namely, Mindola, Chibuluma, South Ore Body (S.O.B.) and Central shafts to compare the performance of these collectors against the existing SEX collector. Parameters considered in the evaluation were grade-recovery relationships and copper/cobalt kinetics at different collector dosages. Release analysis techniques were also employed to determine the theoretical maximum recovery of copper and cobalt for each of the collectors.It was found that the existing collector SEX showed superior flotation performance as compared to the three Senkol collectors. SEX responded better than Senkol collectors at both bulk and segregation stages of flotation. However, the Senkol collectors, particularly Senkol 45 and Senkol 700 gave very fast flotation kinetics at all dose rates during bulk flotation.Furthermore, it was shown that depression of cobalt minerals using sodium cyanide at the pH of 11.5 is not very effective with Senkol collectors, as a considerable amount of cobalt reports to the copper concentrate, which is not the case with SEX collector.