Enhancement of gold agitation leaching by HPGR comminution via microstructural modification of gold ore particles

A comparative study was carried out to investigate the effect of high-pressure grinding rolls (HPGR) comminution on agitation leaching of gold ore in comparison with the conventional jaw crusher (JC) comminution. The HPGR comminution products were evaluated in terms of particle size distribution, specific surface area and average pore volume, and the origin and density of micro-cracks. HPGR comminution produced finer particles with larger specific surface area and average pore volume, more surficial and internal micro-cracks. It was found that intragranular micro-cracks were dominant in JC products while intergranular micro-cracks were favored by HPGR products. Under optimum HPGR conditions (medium pressure of 5.5 N/mm(2)), gold metal recovery during agitation leaching was increased 6.79%-10.93% while cyanide consumption was reduced 5.82%-11.11%. These results suggest that more and narrower micro-cracks included in HPGR products may enhance contact between the leach solution and gold grains which contribute to the enhancement of gold agitation leaching. However, excessive grinding of HPGR products will moderate the advantage of HPGR comminution.