The recovery of sulphuric acid from the waste anodic aluminum oxidation solution by diffusion dialysis

The recovery of H2SO4 from waste anodic aluminum oxidation solution using diffusion dialysis process was investigated by a series of batch, dynamic and pilot-scale tests. Experimental results from batch tests indicated that to some extent agitation could reduce concentration polarization phenomenon and CuSO4 could enhance proton permeability throughout the DF120 anion exchange membrane. Dynamic experimental results showed that both acid recovery and H+ concentration in recovered acid decreased with flow rate increase when the flow rate ratio of water to feed was kept at 1.0, and the optimal flow rate range of 3.0 × 10−4 m3/h to 5.0 × 10−4 m3/h (corresponding to the membrane flux of 9.4 × 10−5 m3/h m2 to 1.56 × 10−4 m3/h m2) was obtained. Although acid recovery efficiency could be improved by increasing the flow rate ratio, the recovered acid concentration decreased and metal leakage increased. And it is confirmed that the optimal flow rate ratio of water to feed should be controlled at 1.0–1.2. Pilot-scale tests performed very well when using the wastewater from a real anodic aluminum oxidation plant. H2SO4 recovery, recovered acid concentration and Al3+ leakage in steady-state condition were 85.25%, 4.08 mol/L and 4.98%, respectively, suggesting that diffusion dialysis is a cost-effective technique for acid recovery from waste anodic aluminum oxidation solution.