The role of organic compounds in the recovery of valuable metals from primary and secondary sources: a mini-review

Abstract

Growing quantities of end-of-life batteries, increasing demand for critical metals and the depleting reserve of high grade ores have necessitated the need to explore secondary sources such as spent lithium ion batteries (LiBs). Among various processes developed for the recovery of materials from the LiBs, the hydrometallurgical approach is mainstream due to its flexibility and efficiency. However, the cost and environmental impacts of hydrometallurgical approaches depend on the reagents used. Organic compounds such as organic acids and biomasses as lixiviants and reductants are considered cheaper and more eco-friendly alternatives to their inorganic counterparts conventionally used. This review summarises the progresses made in the use of organic based substances as reductants in reductive leaching of spent LiBs and low grade ores. It also discusses factors affecting leaching mechanisms, possible reaction chemistries and kinetics. Analysis of the available data in the literature suggests that the use of organic-based compounds could achieve comparable recovery but with much reduced adverse environmental impacts in the extraction of metals from spent LiBs. Further, technology development in the area will benefit from application of key knowledge on the recovery of metals from low grade ores. The review concludes with a summary of current challenges facing the industrial application of organic compounds and highlights future perspectives on organic acids as lixiviants in a mixed acid leaching system.