Selective leaching of copper and zinc from primary ores and secondary mineral residues using biogenic ammonia

Abstract

With the number of easily accessible ores depleting, alternate primary and secondary sources are required to meet the increasing demand of economically important metals. Whilst highly abundant, these materials are of lower grade with respect to traditional ores, thus highly selective and sustainable metal extraction technologies are needed to reduce processing costs. Here, we investigated the metal leaching potential of biogenic ammonia produced by a ureolytic strain of Lysinibacillus sphaericus on eight primary and secondary materials, comprised of mining and metallurgical residues, sludges and automotive shredder residues (ASR). For the majority of materials, moderate to high yields (30–70%) and very high selectivity (>97% against iron) of copper and zinc were obtained with 1 mol L−1 total ammonia. Optimal leaching was achieved and further refined for the ASR in a two-step indirect leaching system with biogenic ammonia. Copper leaching was the result of local corrosion and differences in leaching against the synthetic (NH4)2CO3 control could be accounted for by pH shifts from microbial metabolism, subsequently altering free NH3 required for coordination. These results provide important findings for future sustainable metal recovery technologies from secondary materials. ; This work was conducted under the financial support of the Strategic Initiative Materials in Flanders (SIM) (SBO-SMART: Sustainable Metal Extraction from Tailings, grant no. HBC.2016.0456) and the European Union's Horizon 2020 research and innovation programme, Metal Re-covery from Low-Grade Ores and Wastes Plus (METGROW+, grant no. 690088) . FV acknowledges support by the Flemish Agency for Inno-vation and Entrepreneurship (Vlaio) via a Baekeland PhD fellowship (HBC.2017.0224) and by the Research & Development Umicore Group. We would like to thank Pieter Ostermeyer and Karel Folens for assis-tance with thermodynamic modelling and CMET and ECOCHEM group members and SMART/METGROW+partners for valuable discussions throughout the projec.