Separation of alumina alkaline solution by electrodialysis: Membrane stack configuration optimization and repeated batch experiments

• NaOH and NaAl(OH)4 are separated through ED.
• The optimal membrane stack configuration is three repeating units configuration.
• Acid cleaning can effectively eliminate the membrane fouling.
• Relatively high alkali recovery ratio and low energy consumption can be achieved.
• Self-prepared AM-QP-30 membrane performs better than commercial membrane FQB.

Alumina alkaline solution containing NaOH and NaAl(OH)4 is separated by electrodialysis (ED), which uses self-prepared anion exchange membrane AM-QP-30. The stack arrangements and number of repeating units are optimized to achieve high alkali recovery ratio and low energy consumption. Meanwhile, repeated batch experiments (RBEs) are carried out to investigate the effect of erosion on membrane stability.The optimal membrane stack configuration is three repeating units configuration. The membrane fouling can be effectively eliminated by acid cleaning during the RBEs. The ED performances are stable and excellent. For instance, the alkali recovery ratio (ηOH-ηOH-) can reach up to 64.9–68.5% and the energy consumption can be reduced to 7.29–7.65 kW h/kg. The performance of AM-QP-30 membrane is superior to commercial FQB membrane in consideration of the lower mass loss ratio, stable ED performances and morphology after erosion. As a result, the ED process is feasible and stable to separate the alumina alkaline solution.