Flotation of mixed oxide sulphide copper-cobalt minerals using xanthate, dithiophosphate, thiocarbamate and blended collectors

L.T Tijsseling,Q Dehaine,G.K Rollinson,H.J Glass

doi:10.1016/j.mineng.2019.04.022

Abstract

More than half of the global cobalt supply from primary sources is currently produced in the Democratic Republic of Congo (DRC) from ores containing copper-cobalt oxides or copper-cobalt sulphides. Where oxide and sulphide cobalt-bearing copper minerals occur together, efficient recovery of copper and cobalt is known to be extremely difficult. This study investigates the flotation behaviour of a mixed oxide-sulphide ore where copper is hosted in sulphides phases such as bornite, chalcopyrite and chalcocite, and oxide phases such as malachite and to a lesser extent chrysocolla. Three cobalt-bearing oxide minerals are observed in the mixed ore, i.e. heterogenite, kolwezite and cupro-asbolane, while carrollite is the only cobalt-bearing sulphide mineral. A two-stage rougher-scavenger flotation process is used in which sulphides are extracted from the ore first. In the second stage, oxides are activated using controlled potential sulphidisation followed by their recovery. Tests are performed with a range of collectors, including xanthate, phosphorodithioate, dithiophosphate, thiocarbamate, and a blend type. A dithiophosphate collector proved to the most successful, achieving recovery of 94% of the carrollite, more than 90% of the copper sulphides, and 70% of the copper oxide minerals. The recovery of the cobalt oxides was less successful, with recovery of roughly half the kolwezite and only 20% of the heterogenite and cupro-asbolane. Despite the generally promising recoveries, the selectivity of the flotation process is relatively low with all the concentrates containing a significant amount of carbonate and silicate minerals. This suggests that a number of improvements require further investigation, notably the application of hydroxamate collectors, depressants and reverse flotation.

Highlights

Over the past two years the cobalt price has been volatile, varying by about 300% (London Metal Exhange, 2018) due to speculation that global cobalt consumption will triple in the decade (Burton, 2018)
The evaluation of a range of collectors for concentrating copper and cobalt with flotation from a Democratic Republic of Congo (DRC) ore containing a mixture of oxide and sulphide minerals is reported
The flotation process consists of a sulphide flotation stage followed by an oxide flotation stage with controlled potential sulphidisation

Summary

Introduction

Over the past two years the cobalt price has been volatile, varying by about 300% (London Metal Exhange, 2018) due to speculation that global cobalt consumption will triple in the decade (Burton, 2018). Less is known about processes for copper and cobalt extraction from mixed oxide-sulphide ore (Crundwell et al, 2011). For mixed oxide-sulphide ores, up to 80% of the copper and 60% of the cobalt is recovered in the sulphide concentrate while for the oxide concentrate, only 60% of the copper and 40% of the cobalt are usually recovered (Crundwell et al, 2011). With mixed oxide-sulphide ores, it is accepted practice to concentrate sulphide and oxide minerals in separate flotation processes. While flotation is a common method to concentrate sulphide ore in the DRC, oxide ore requires sulphidisation prior to flotation with xanthate collectors (Crundwell et al, 2011). The net sulphidisation for sodium sulphide can be represented as given in Eq (1) (Clark et al, 2002; Fuerstenau et al, 2007; Newell et al, 2007): M2+A2 + 2Na+ + S2 M2+S2 + 2Na+ + A2

Methods

Results

Conclusion