Resource Recovery from High-Salinity Rare Earth Metallurgy Wastewater by Coupling Electrolysis and Membrane Processes

The treatment of high-salinity wastewater generated from the use of sodium hydroxide (NaOH) in rare-earth metallurgy poses significant environmental and resource-recovery challenges. Conventional methods are often economically unfeasible due to their high energy consumption and limited value recovery. To address these limitations, this study proposes an innovative integrated electrochemical process designed not only to desalinate the wastewater efficiently but also to valorize it through the simultaneous co-production of NaOH, chlorine (Cl2), and hydrogen (H2). Systematic optimization reveals a critical trade-off between ion transport efficiency and side reactions, with optimal performance achieved at 2 mol L−1 NaCl, 80 mA cm−2 current density, 2 mm electrode spacing, 30 mL min−1 flow rate, and 5000 mg L−1 initial NaOH concentration. The system maintains exceptional long-term stability, sustaining 97.5% Cl− removal over 4410 min of continuous operation without membrane fouling, a key advantage over conventional processes. Validation with authentic rare earth wastewater achieves 90.3% desalination within 5 h. Techno-economic analysis shows that the market value of recovered NaOH nearly offsets the energy cost, achieving near-cost-neutrality. This work establishes electrolysis–membrane coupling as a technically viable and economically attractive strategy for transforming high-salinity industrial waste streams into valuable resources.