Effect of different collector dose rates on cobalt segregation

Nkana Concentrator is the mast important mineral processing unit of Zambia Consolidated Copper Mines (ZCCM) (soon to be privatised) which contributes about 65% of cobalt concentrates treated at the Nkana and Chambeshi Cobalt plants to produce high purity cobalt metal. However, it has of late been ex periencing problems with the segregation of the bulk concentrates which con tain an appreciable amount of copper which overloads the performance of the cobalt tankhouses. In an effort to improve the copper/cobalt separation at segregation stage, a number of new collectors have been put on trial tests with a view of repl acing the traditional Sodium Ethyl Xanthate (SEX) which has been in use sin ce the sixties. The intention is to possibly isolate a collector that will give improved recoveries and grades of both copper and cobalt to their resp ective concentrates at different flotation stages. In this work, a series of laboratory testworks were conducted using Senkol 26 a Xanthic ester, Senkol 45 a blend of alkyl dithiophosphate and Xanthate s and Senkol 700, a thionocarbomate type, which were supplied by SENMIN of South Africa on Nkana Concentrator feed materials. The feed materials are f rom four different sources namely; Mindola, Chibuluma, South Ore Body (S.O. B.) and Central shafts. The tests were carried our to compare the performan ce of the collectors based on their dose rates and later their performance compared to the collector currently being used at Nkana Concentrator. SEX at the dose rates of 20 and 30 g/t gave lower cobalt loses of 17 and 11 .2 %TCo respectively, whilst grades were also very low at 0.25 and 0.19 %TC o respectively. The Senkol collectors exhibited poor separation of cobalt from copper at al l dose rates except for Senkol 26 which gave loses of 8 %TCo at grade 0.14 %TCo at 50 g/t of collector which was much better than the SEX. This work has also shown that there is no incentive in increasing the dose rate of SEX beyond 30 g/t as there was no improved separation of cobalt fro m copper at an optimum depressant dosage and pH. On the other hand, the sep aration performance of Senkol 26 improved with increasing collector dose ra te. Senkol 45 exhibited an increase in the amount of cobalt lost to the cop per concentrate as the dose rate of the collector increased while no signif icant changes were noted with Senkol 700. (C) 1999 Elsevier Science Ltd All rights reserved.