Non-Cyanide Flotation Method of Iron Rich Sphalerite in the Processing of Lead-Zinc Ores

The processing of sulphide ores with variable and complex mineral composition and physical properties, such as those processed by two-stage selective flotation scheme in “Erma reka” concentrator, Minstroy Holding JSC, requires excellent selectivity in order to achieve acceptable concentrate grades. The lead-zinc ores from the hydrothermal lead-zinc deposits mainly contain galena (PbS), sphalerite (ZnS), pyrite (FeS) and chalcopyrite (CuFeS2), as well as non-metal minerals such as quartz, carbonates and clinopyroxenes skarns. One of the main impurities present in sphalerite is iron, which is known to be detrimental to the rate of sphalerite flotation and its recovery. The results from the conducted laboratory and industrial tests, presented in the previous study, showed that it is possible to depress the iron rich sphalerite by adding MINFIT® (modified sulfur-oxy depressant) at the pH of approximately 9.5 in rougher lead flotation circuit, leading to reduction of zinc sulphate consumption and complete elimination of cyanides from the flotation process. Furthermore, the consumption of copper sulphate, which reactivates the surface of the zinc minerals, was significantly reduced. Consequently, the optimisation of the reagent regime in the Erma reka concentrator, led to notably improved qualitative (grade, recovery) properties of the final lead and zinc concentrates. Moreover, when comparing the reagents consumption for 2014 and 2016 – when the processing plant have been applying the new optimized reagents regime, comprises the use of MINFIT as the primary depressant, the following results have been achieved: ZnSO4 decreased by 30%; CuSO4 consumption decreased four times and full rejection of cyanides from the process. Finally, this paper provides a state-of-the-art review of the obtained results during the period of application of the new flotation reagents regime in the Erma reka concentrator, Minstroy Holding JSC.