Review of rhenium extraction and recycling technologies from primary and secondary resources

Rhenium is a scarce and highly important metal, which is widely used in high-temperature superalloys and platinum–rhenium catalysts due to its unique physicochemical properties. The substitution of rhenium in its applications is very limited, and there is no suitable substitute without losing essential performance. Furthermore, global extractable primary rhenium resources are predicted to deplete within 130 years. In this paper, rhenium extraction and recycling technologies from primary and secondary resources are critically classified and reviewed. Rhenium is primarily produced as a by-product in molybdenum, copper, lead and uranium production from the concentrates and ores. Rhenium is extracted from roasting fume and dust, leaching residue, and aqueous solution to produce a rhenium bearing solution. Subsequently, rhenium rich solution is generated by separation with solvent extraction, ion exchange, adsorption, membrane techniques or chemical precipitation. Finally, rhenium is produced via crystallization and reduction steps. Recycling rhenium from spent alloys and catalysts is a multi-step process combining pyrometallurgical and hydrometallurgical techniques, where its separation and the subsequent steps are similar to that of extracting rhenium from primary resources. The main challenges in rhenium extraction and recycling are the enrichment of rhenium in the production and the collection and classification of spent rhenium scrap, to identify suitable processes to recover the rhenium with a high recovery. This paper contributes to better understanding the rhenium extraction and recycling processes and enhances sustainability of rhenium production.