Froth flotation study of Pb-Zn ore under different temperature constraints

• The responses of Pb-Zn ore lab flotation were significantly impacted by temperature. • At higher temperatures, a weaker and less stable froth was observed. • Increased air recovery and froth stability at lower temperatures. • This difference corresponded to a lower zinc grade. Variations in temperature are known to affect the metallurgical responses of sulfide flotation. Different studies have identified that sphalerite recovery and grade are impacted by temperature with flotation reagent efficiency being responsible for fluctuations in primary concentration (selective attachment of valuable mineral particles to air bubbles) while the effects on secondary concentration (froth drainage processes that remove excess water and gangue, improving concentrate quality) remain largely underexplored. No study has tried to evaluate if temperature-induced variations in flotation are driven by pulp zone mechanisms or secondary concentration effects in the froth zone. Ore flotation experiments resulted in the highest variability for sphalerite, which corresponds well with the literature (comparable trends of the concentrate grade change with temperature as well as the magnitude of this change were observed). The effectiveness of flotation modifiers such as copper sulfate pentahydrate and zinc sulfate heptahydrate have been studied in a selective flotation circuit using the central composite design of the experiment along with temperature. Apart from the variations in the metallurgical response with temperature, the results showed variations in the bubble size on the froth surface, bubble burst rate, froth speed, froth height over the lip and water recovery. Higher gangue entrainment (quartz and baryte) was likely originated from higher water recoveries and more stable froth at colder temperatures. It presumably explains the observed lower zinc concentrate grade. Performed numerical simulations confirmed an increasing froth drainage rate at higher temperatures, which is in line with water recovery, gangue recovery, and sphalerite grade trends observed in the tests. Findings of this research and the data from the literature underscore the critical need to assess the temperature impact on sphalerite flotation for effective mine planning and feasibility studies.