Nanoporous Atomically Thin Membranes for Desalination and Rare Earth Materials Recovery

Rare earth elements (REEs) play an indispensable role in new industries including renewable energy, electric vehicle and superconductors. REEs have been identified as critical as published in the federal register by the secretary of the interior. Currently, China produces ~97% of total world supply of these critical elements. It is extremely important for the US to be self-sufficient in these materials so as to be competitive in future. Geothermal brines have been identified as excellent sources of REEs, however at very low concentrations. Extraction of REEs at such concentrations is very challenging. Traditional processes such as adsorption, solvent extraction and ion exchange are uneconomical due to sheer volume of fluids to be processed. Moreover, these processes are not selective and therefore further separation steps are required. This increases the operating as well as capital costs rendering the overall process uneconomical. This project aims to develop transformative nanoporous atomically thin membranes (NATMs) that enable energy-efficient, chemical-resistant, versatile, and cost-effective liquid filtration that is critical rare earth materials recovery and in the long term for water desalination. Atomic-scale pores in the ultrathin and ultrastrong graphene will retain the trivalent REEs, yet permit rapid flow of mono and divalents – potentially constituting a disruptive next-generation membrane for REE recovery. In case of water desalination, the membrane pore size can be tailored to retain monovalent salts while permeating pure water. Prior work has demonstrated that NATMs have the potential for up to 40% improvement in energy efficiency of water desalination, longer membrane life, compact plants with lower operational costs, effective rejection of micropollutants, high chlorine/chemical resistance, higher recovery and less brine waste. The overall objective of the proposed project is to scale-up and demonstrate techno-economic feasibility of REE recovery using graphene NATMs. Upon successful commercialization, the proposed innovation will enable higher energy efficiency, domestic recovery of critical materials and reduced dependence on China.