Froth flotation of an Nkomati mineral ore using mixtures of thiol collectors
Nickel, a valuable base metal, is the predominant product from the Nkomati mine in South Africa. High-grade nickel mineral ores (2%) from the Massive Sulphide Body have been depleted leaving those of low grade (0.3%). The beneficiation of this ore presents a challenge to the minerals processing industry. In response, batch froth flotation tests were used to explore the effects of mixtures of potassium amyl xanthate (PAX) and IPETC (Isopropyl ethyl thionocarbamate) on the grades and recoveries of nickel. In the mixtures, the xanthate accounted for 95.5, 90, 85 and 80 mole% respectively. Generally an increase in the nickel grade and recovery was observed with the mixtures relative to PAX. IPETC gave a significant increase in the cumulative water recovery with a significant decrease in cumulative nickel grade relative to PAX. PAX gave the highest cumulative nickel grade for the singular collector tests (1.9%), while obtaining the lowest cumulative recovery (77%). Out of the collector mixtures, mixtures 85% PAX: 15% IPETC and 90% PAX: 10% IPETC produced the joint highest cumulative grades (1.8%). These mixtures both gave recoveries of 82%. Collector mixture 95.5% PAX: 4.5% IPETC gave the second highest grade (1.7%) and the highest nickel recovery (85%). Although there were differences in the cumulative nickel grades and recoveries there were statistically no significant improvements observed with the use of the mixtures of PAX and IPETC in comparison to the industry mixture (95.5% SIBX: 4.5% IPETC). Tests were performed using the three best performing collector mixtures at molar dosages of 1.3, 0.65 and 0.325mmol/t. The highest cumulative nickel grades were obtained at the lowest collector dosages (at a molar dosage of 0.325mmol/t of 95.5% SIBX: 4.5% IPETC) with collector mixture 95.5% PAX: 4.5% IPETC being the most selective with a nickel grade of 2%. It was also observed that an increase in collector dosage, generally increased the cumulative nickel recovery with collector mixture 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmol/t gave the highest cumulative recovery out of the tested mixtures (85%). The study also indicated that an increase in selectivity (i.e. cumulative grade) was at the expense of cumulative recovery. With a decrease in dosage, there was no significant improvement in the cumulative nickel grade and recovery for the tested mixtures compared to the industry mixture. There was however a significant decrease in the water recoveries achieved with PAX and collector mixtures 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmolg/t of as well as mixture 90% PAX: 10% IPETC at a molar dosage of 0.65mmol/t.