Enhanced flotation of refractory gold ore by using sulfur-oil agglomeration with (NH4)2S2O3 as regulator in weak acidic pulp

Abstract

In this study, a new approach “sulfur-oil agglomeration” for gold flotation was put forward to recover gold particles in laboratory and industrial scale experiments. The optimum recovery of gold was obtained by adding (NH4)2S2O3, oil emulsions and sulfur into the mill, together with butyl xanthate as the collector in weak acidic pulp adjusted by H2SO4.Fundamental concepts of gold flotation were considered, including the sulfur-oil-gold agglomeration mechanisms and the role of (NH4)2S2O3. The possible mechanism had been put forward: (1) nature of (NH4)2S2O3 is complex, it renders the oxidized gold surface cleaned, the exposed fresh surface shows strong natural oleophilicity; (2) in weak acidic pulp, S decomposed from (NH4)2S2O3, a highly hydrophobic/oleophilic material, agglomerated with gold; (3) then the oil droplets overspread the gold surfaces and the collision of these oil wetted particles caused formation of “liquid bridges” each upon them. As a result, the fine gold particles in the beginning were converted to the masses in the form of sulfur-gold-oil which were bonded together by liquid bridges. Meanwhile, the sulfur could strengthen the adsorption of collectors on gold surface, as well as the floating size range of gold is widen, and the recovery of gold is significantly improved.Industrial trials conducted at Yunnan, China showed that an average gold recovery of 87.39% into a concentrate assaying 25.84g/t Au from a feed of 1.8–3.0g/t could be achieved by the aid of sulfur-oil agglomeration method.