Efficiency of Chemical and Biological Leaching of Copper Slag for the Recovery of Metals and Valorisation of the Leach Residue as Raw Material in Cement Production

Abstract

Copper slags produced in vast quantities in smelting operations could be considered as secondary material sources instead of stockpiling them in landfills. This study investigates the recovery of valuable metals from copper slag and the valorisation of the leach residue as construction material in line with the principles of a circular economy. By taking into account that the environmental characterization of the as-received copper slag did not allow its disposal in landfills without prior treatment, chemical and biological leaching were tested for the recovery of metals. Pre-treatment with acids, namely HNO3 and H2SO4, resulted in the extraction of several target metals and the production of an almost inert waste. Despite the clearly better oxidative conditions prevailing in the bioleaching reactors, chemical leaching resulted in the higher dissolution of Cu (71% vs. 51%), Co (70% vs. 36%), and Zn (65% vs. 44%). The acid consumption was much lower during the bioleaching experiments compared to the chemical leaching. The bioleach residue was suitable for its use as supplementary cementitious material, showing a better performance than the reference sample without causing any detrimental effects to the calcium aluminate cement (CAC) quality. The complete valorisation of copper slags is expected to improve the economics of the process, by avoiding landfill costs and producing saleable products with high added value.

Metal Recycling via Biohydrometallurgy

“…Aufgrund der alkalischen Beschaffenheit von Aschen und Schlacken und den oft hohen Gehalten an toxischen Elementen sind diese Abfa ¨lle jedoch eine Herausforderung fu ¨r die Biolaugung unter Verwendung acidophiler Mikroorganismen [47,48]. Zahlreiche Studien beweisen jedoch die Machbarkeit der Biolaugung von Schlacken mit acidophilen Mikroorganismen, sowohl im Schu ¨ttelkolben als auch im Ru ¨hrtankreaktor mit Feststoffgehalten von bis zu 25 % [28,[49][50][51][52]. Im Vergleich ist jedoch ein Ru ¨ckgang des Metallausbringens bei ho ¨heren Feststoffgehalten zu beobachten, was einerseits auf toxische Begleitelemente bzw.…”

Recovery of Iron from Copper Slag Using Coal-Based Direct Reduction: Reduction Characteristics and Kinetics

“…As some papers have reported, in 2019, China's copper output reached 9.8 million tons, and more than 20 million tons of copper slag were produced [6,7]. The accumulated stockpile of copper slag over the years exceeds 120 million tons [8]. The huge stockpile of copper slag encroaches on the land and pollutes the soil and groundwater [9].…”