Enhancing gold recovery from refractory bio-oxidised gold concentrates through high intensity milling

ABSTRACT This paper aims at investigating the gold leaching behaviour of refractory, bio-oxidized flotation gold concentrates, before and after high intensity milling, for enhancing gold extraction. Specifically, the role of factors such as milling time and ceramic balls-to-pulp mass ratio, coupled with corresponding physico-chemical changes on gold extraction yield and leaching kinetics was studied. From the results, high intensity milling of the bio-oxidised flotation concentrate reduced the average particle size by increasing the fraction of fines mainly through abrasion/attrition, and increased surface area by both fine particle and crevice production. Furthermore, notable increase in sodium cyanide consumption was observed with an increase in the mechanical stress deployed, consistent generally with degree of mineral relative amorphisation and reactive gangue mineral exposure. About 1.6–1.8 times variable increase in gold yield was observed after 24 h cyanide leaching of activated samples, irrespective of the impacted mechanical stress and degree of mineral amorphisation.