Task 4.1. – Optimization of the alkaline hydrometallurgical process (M18-M24)

This task will consist in implementing selective unit operations propped up on the chemical nature of the non-ferrous metals from steel slags. The scientific approach will consist in adapting the medium of selective lixiviation and the complexation/separation/recovery methods in order to optimize the “Strategic Metals”(SMs) extraction yields. Special attention will be paid on choosing conditions and environments that do not present side effects and allow a minimization of the environmental impacts.

Laboratory tests will be conducted on the WP3 samples collected to determine the highest recovery of SMs and the optimum hydrometallurgical circuit. Testing will be performed in the ARMINES/SPIN laboratories with additional experimentation of leaching methods by the partner also specialized in this field (BRGM). Optimum leaching conditions will be identified for each physically  pretreated (WP3) sample, related to its specific mineralogy and the SMs (Cr, V, Mo, etc.) to be extracted. Study of the experimental conditions will identify the influence of the main parameters. In particular, the following experimental conditions will be addressed: alkaline leaching agent concentration, particle size, leaching time, liquid/solid ratio, pulp density, pressure and/or temperature conditions and stirring rate. The process conditions will be also optimized in terms of maximizing liquid reagent recycling and extraction  vields, while minimizing base consumption, energy consumption and environmental impact. To determine the leaching behavior of WP3 samples under specified conditions, European standardized methodologies (NF EN 12457 and NF EN 12920) will be performed in batch reactors. Additional methods to determine the influence of pH on the leachibility of inorganic constituents (NF EN 14997) will also be conducted. This step will constitute a first scale-up of the process and will form the basis for the laboratory pilot tests to be conducted in task 4.2..


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