Study on Recovering High-Concentration Lithium Salt from Lithium-Containing Wastewater Using a Hybrid Reverse Osmosis (RO)–Electrodialysis (ED) Process

A novel industrial lithium-containing wastewater depth concentrating process integrating reverse osmosis (RO) and electrodialysis (ED) into a system is presented. A systematic analytical study was accomplished to optimize the studied parameters and minimize the energy consumption. The tested parameters were as follows: RO recovery by adding pressure, ED voltage drop, the concentration of RO retentate in ED feed solution, ED volume ratio, and ED operating mode. By using RO retentate instead of initial wastewater in the ED process, water energy consumption was reduced by 3.41 times from 26.67 to 7.81 kW h/m3, while optimizing the RO retentate concentration for the ED feed solution reduced the cost to 0.47 $/kg. The results showed that RO is crucial to preconcentrate lithium salt and save energy. Furthermore, the final LiCl concentration can approach as high as 87.09 g/L with the secondary ED process (Vd:Vc = 3:1), while the energy consumption can be saved as 7.71 kW h/m3 when the experiments stopped in region 1. The concentration factor of 12.32 can be achieved to justify the feasibility of integration of a high volume ratio concentrating with a mutistage concentrating protocol. As a consequence, the hybrid RO–ED process allows for lithium salt extraction and concentrating from industrial lithium-containing wastewater, which is appropriate for industrial applications.