From waste to resource: A review on biological and physicochemical metal remediation and recovery in the light of the circular economy

Abstract

Remediating metal-contaminated sites, particularly those impacted by the extraction or processing of critical raw materials (CRMs), poses significant environmental and health challenges. This topic has typically been approached from either a physicochemical or a biological perspective, depending on the disciplinary focus. The present review seeks to bridge that gap by integrating both approaches into a unified and comprehensive framework, exploring their interconnections and highlighting the insights that emerge from their synthesis. It describes current advances in both methods groups for the treatment of metal-containing wastes, focusing on the removal of toxic metal(loid)s, and the recovery of CRMs within the framework of the circular economy. Physicochemical techniques play a crucial role in waste decontamination, while biological methods may offer environmentally sustainable alternatives for mitigating metal pollution. Microbial strategies are particularly advantageous due to their high specificity and effectiveness even at low contaminant concentrations, while also facilitating site restoration with minimal ecological damage. Integrating biological and physicochemical treatments may significantly enhance remediation performance, for more efficient and sustainable solutions. In particular, "treatment trains" or sequential treatment approaches combine multiple remediation methods to enhance efficiency while enabling recovery and reuse of valuable metals. Successful implementation of these strategies requires the optimization of treatment conditions and the integration of green remediation practices into large-scale applications. This review highlights the need for more comprehensive and in-depth studies (including field-scale applications) to address critical knowledge gaps and to further develop these potentially cost-effective and more sustainable methods for extracting valuable metals from mining waste.