New generation of commercial nanofiltration membranes for seawater/brine mining: Experimental evaluation and modelling of membrane selectivity for major and trace elements

The depletion of high-grade ores and the surging demand for raw minerals necessitate sustainable and economically viable approaches for mineral extraction. This study delved into the application of nanofiltration (NF) as a promising solution for selective separation of monovalent elements from divalent ones, enhancing downstream mineral recovery from seawater and seawater reverse osmosis (SWRO) brine. Investigating five distinct commercial NF membranes (NF90, NFS, NFX, VNF1, and DK), the research assesses their capabilities in separating both major and trace elements. Performances of the NF membranes were evaluated as a function of applied pressure from 8 to 30 bar using a flat -sheet configuration. Moreover, experimental data was fitted to the solution-electro-diffusion-film model, aiming to describe ion flux. The study confirmed the efficient rejection of multivalent cations with rejections surpassing 90 % when treating both seawater and SWRO brine with all the tested membranes. Notably, the DK membrane stood out as the most proficient candidate, demonstrating superior permeability and selectivity for multivalent elements over monovalent ones, showcasing its potential for selective pre -concentration of minerals. The study underscored the significance of NF technology in the circular valorization of seawater and SWRO brine, providing insights into its role in addressing economic feasibility concerns associated with mineral extraction from these abundant sources.