European research organization VITO, a METGROW+ participant, reports it validated heap leaching of a Cr/Ni-rich sludge in a 1-m³ fully automated setup with recirculation of the leaching solution and continuous pH and redox adjustment.

Critical and economically significant metals such as cobalt and nickel can be recovered profitably from metal refining wastes as well as ores with lower than usual concentrations, according to the results of an European Union study coordinated by VTT Technical Research Centre of Finland.

VTT reported that the recently completed European METGROW+ project identified methods to increase Europe’s self-sufficiency in critical commodities, including cobalt, nickel and zinc, by 10%-20% using only the material streams studied in the project. The developed methods can additionally be used to recover metals from other material streams, according to VTT, which noted that various stakeholders interested in using low-grade ores and waste can evaluate the valorization of raw-material streams with a web tool developed in the project.

The METGROW Calculator web tool is intended to support decision-making by European mines, mining technology developers and others. The user can enter, for example, local laterite ore or jarosite from the zinc industry as a raw material and assess the options for utilizing the raw material stream in relation to local waste and energy prices.

“We developed and compared different methods for recovering metals from metal refining waste sludges as well as from low-grade ores whose metal concentrations have been considered too low for profitable recovery. We paid particular attention to the profitability and environmental impact of the methods. By developing new and combining old methods, we found new ways to increase the recovery of cobalt, nickel and zinc, among others,” VTT Päivi Kinnunen said.

“The potential of low-grade ores, wastes and side streams is now easier to discern as we know the kind of metal concentrations they have, and which methods are suitable for recovering those metals. Even a smaller side stream from a large mine or metallurgical plant can prove to be a significant business for another company,” Kinnunen explained.

According to VTT, some 19 companies, research organizations and universities from nine EU countries joined in the four-year 7.9 million ($8.8-million) project, with R&D activity divided among the participants according to exper-
tise in methods and materials. The research also considered local waste costs and energy sources — factors that can influence profitability and environmental impact of the methods in each country.