Clinker sorption activity in non-ferrous metals leaching

Various reagents can be employed during the hydrometallurgical processing of aged clinker for the sequential dissolution and subsequent extraction of non-ferrous and precious metals into marketable products. However, due to the significant presence of coke in the clinker, the preg-robbing effect occurs. This study investigates the sorption properties of the coke component of clinker with respect to copper and zinc in sulfuric and citric acid solutions and with respect to gold in sodium dichloroisocyanurate, cyanide, and thiocarbamide solutions. The results demonstrate that coke and mineral particles in clinker exhibit different sorption activities toward cations and complex ions of non-ferrous and precious metals depending on the solution type and particle size. The degree of copper sorption in sulfuric acid solutions ranges from 5.03 to 11.6%, depending on the particle size of the coke. For zinc, the range is from 0.27 to 0.81%. In citric acid solutions, the values range from 7.62 to 54.6% for copper and from 7.62 to 28.6% for zinc. The degree of gold sorption fluctuates widely: in cyanide solutions, it ranges from 1.23 to 91.12%; in sodium dichloroisocyanurate solutions, it ranges from 38.8 to 91.16%; and in thiocarbamide solutions, it ranges from 4.76 to 5.7%. As the material is ground and the surface area increases, the preg-robbing effect intensifies predictably. The preg-robbing effect depends on the reagent concentration. In cyanide solutions, the conditional degree of gold sorption increases nearly tenfold as the NaCN concentration varies from 0.5 to 10 g/dm³. Conversely, in sodium dichloroisocyanurate solutions, the degree of gold sorption decreases from 80 to 40% as the reagent concentration increases from 5 to 10 g/dm³. Additionally, sorption kinetics are faster for chlorinated solutions. Within 80 min, gold sorption reached 23.6% from cyanide solutions and 85.6% from chlorinated solutions. It was determined that the preliminary removal of coke through flotation did not yield positive results. Regardless of the degree of clinker grinding, extraction of sorption active carbon into the froth product is incomplete. Flotation tails inevitably contain a significant amount of coke, which results in low gold extraction during the leaching of the tails.