Mechanochemical activation of chalcopyrite by high-intensity milling: Comparison between ceramic ball milling, vibration milling and vertical stirred ball milling.

In this work, we investigated the mechanochemical activation of a chalcopyrite concentrate by three high-intensity grinding techniques: ceramic ball milling, vibration milling and vertical stirred ball milling. The thee grinding methods were investigated under different operating conditions in terms chalcopyrite to grinding media weight ratio and amount of quartz sand as additive to increase the grinding surface. As for the grinding media, the ceramic ball mill was tested with aluminum and zirconium grinding balls whilst a tungsten stone and zirconium balls were used respectively as grinding media in vibration milling and vertical stirred ball milling. The influence of fine grinding on the particle size distribution, surface area and phase composition/crystallinity of the chalcopyrite concentrate was elucidated by laser diffraction particle size analyzer (SALAD), scansion electron microscopy (FE-SEM) and x-ray diffraction (XRD). The effectiveness of grinding towards the mechanochemical activation of the chalcopyrite concentrate was also assessed by performing leaching experiments with H ₂ SO ₄ at room temperature. All the three investigated grinding methods determined a dramatic decrease of particle size along with the amorphization of chalcopyririte. However, the use of the vertical stirred ball mill with quartz sand resulted also in the partial oxidation of chalcopyrite, especially when feeding the chalcopyrite concentrate with a 30% _w of quartz sand. In leaching, the extraction yield of copper increased from about 15% without mechanochemical activation up to over 60% by using the vertical stirred ball mill with zirconium balls and quartz sand. The dissolution rate of copper, along with the results showing the amorphization and, in some cases, the partial oxidation of chalcopyrite, suggests that the leaching occurs through a two-step process where first the amorphousized chalcopyrite and then the residual crystalline chalcopyrite undergo dissolution.