Occurrence, treatment, and potential recovery of rare earth elements from wastewater in the context of a circular economy

Rare Earth Elements (REEs) are increasingly consumed and released into the environment, leading to REE anomalies in aquatic systems. However, REE extraction is associated with detectable radioactive matter and poses risks to human health, including carcinogenicity, occupational poisoning, and other health effects. REEs have also been shown to have toxic effects on aquatic organisms. This review discusses the levels and occurrence of REEs in wastewater treatment plants, state-of-the-art removal and recovery techniques, and the potential for REE recovery in a circular economy. The study showed that among the light rare earth elements (LREE), Ce had the highest concentration in wastewater, while Gd had the highest concentration among the heavy rare earth elements (HREE). Treatment of REE wastewater has successfully reduced its toxicity and enabled the recovery of valuable components for reuse. In the circular economy, the sustainability of REE mining and application can be improved by converting REEs from wastewater into industrial resources, but limited laboratory and pilot studies make the economic viability of REE recovery uncertain. Therefore, more research is needed to understand wastewater-borne REEs' fate and behavior, in order to develop sustainable and economically feasible recovery methods for a circular economy.