Urban mining of precious metals via oxidizing copper smelting

Abstract

Recycling of precious metals from end-of-life electronics is a key factor for sustainable and efficient raw material usage. Simultaneously with the depletion of natural ore resources, the urban mines are storing increasing amounts of valuable and, more importantly, rare metals. To fulfill the targets of sustainability and move towards circular economy, the liberation of these valuables from wastes back to production and use needs to be improved. This study investigates the recoveries and behavior of gold, silver, palladium and platinum in copper smelting conditions at 1300 °C and pO2=10 −5 -10 −7 atm. The investigated system includes a copper alloy with three different type of slags in silica saturation: pure iron silicate, iron silicate with 10 wt% alumina and iron silicate with 10 wt% alumina and 5 wt% lime, providing information on the influence of alumina and lime on precious metal recovery possibilities. A highly advanced equilibration-quenching technique, followed by EPMA and sensitive LA-ICP-MS analyses, has been adopted to execute the experiments. Results show that gold, platinum and palladium are recovered very efficiently in copper, as their distribution coefficients between copper and slag, L Cu/s , were greater than 10 4 under every experimental condition studied and with all slag compositions. Silver distributed 30-60 times more in copper phase than was lost to slag. The addition of alumina into the slag somewhat decreased the distribution coefficient of silver, whereas gold and palladium distribution coefficients were increased. Lime addition improved the recovery of every precious metal (Pt unclear) into the copper phase. The concentrations of platinum in the slags were mainly below the detection limit of the used LA-ICP-MS, providing a minimum distribution coefficient of 10 6 .

Control of Platinum Loss in WEEE Smelting

“…48 It is, therefore, evident that, in the oxidising process steps, platinum also dissolves as PtO 0.5 in copper-containing iron silicate slags used in secondary copper smelting and refining. Thus, the recent experimentally determined concentrations of platinum in metallurgical slags, 33,34,36 as well as the relationships obtained for platinum distributions between the copper and the slag, were distorted by the detection limits of the analytical techniques used in the phase analyses, as considered earlier. 34 In addition, the chemical dissolution of platinum in the slag in this study is lower than stated in our recent papers, 34,36 where concentrations were reported as upper limits only.…”

“…This will allow us to verify the dissolution mechanism investigated earlier in copper-saturated slag systems of WEEE smelting (waste electric and electronic equipment) for dilute platinum concentrations. [32][33][34]…”

Recycling of tellurium via copper smelting processes

“…This conclusion regarding dissolution as neutral, elemental species should trations of tellurium in matte-slag system, adopted from Sukhomlinov et al [24], are shown for comparison be reliable in the sense that the concentrations of tellurium in ISA slags and copper alloy in all experimental conditions were well above the detection limits of LA-ICP-MS and EPMA, respectively. Thus, the calculated distribution coefficient values represent actual coefficients, not minimum ones, such as reported by us for platinum, for example [34]. In oxidizing conditions, 5 wt% potassium oxide in the slag notably increased the deportment of tellurium into the copper alloy, where it can be recovered in later process stages by anode slime treatment.…”

Critical Metals Ga, Ge and In: Experimental Evidence for Smelter Recovery Improvements

“…The drop-quench technique employed in this study is already relatively widely used in phase equilibria studies [23,24], and nowadays also in minor element investigations [25,26]. The critical steps of the technique include (1) sample precursor preparation, (2) equilibration-quenching experiments and (3) EPMA measurements.…”