Recovery of rare earth elements from waste streams using membrane processes: An overview

Abstract

Recovery of rare earth elements (REEs) has become an attractive process owing to the high costs and limited availabilities of REEs. In addition, the recovery of REEs has become a necessity because of their high toxicity and negative environmental impacts. Conventional processes for the recovery of REEs from waste streams include chemical precipitation, coagulation, flocculation, flotation, ion exchange, adsorption, and electrochemical processes. These processes have various disadvantages such as high consumption of chemicals, high operational costs, and low purity of the extracted elements. Recently, membrane processes have been used for the recovery of REEs. Compared to conventional methods, membrane processes have higher selectivity for REEs and lower energy requirements; moreover, they offer the possibility of zero liquid discharge. Nevertheless, it is still important to evaluate the economic feasibility of using membrane techniques for the recovery of REEs. This review paper provides an overview of the application of membrane techniques for the recovery of REEs from waste streams. Rejection efficiency of several membrane processes and purity of the extracted REEs were analyzed. Economic feasibility of using membrane processes for the recovery of REEs was examined by comparing the capital and operational costs of the processes with the selling prices of REEs.