Recovery of hydrochloric acid from simulated chemosynthesis aluminum foil wastewater by spiral wound diffusion dialysis (SWDD) membrane module

Recovering hydrochloric acid from simulated chemosynthesis aluminum foil wastewater by spiral wound diffusion dialysis (SWDD) membrane module was studied. Effects of flow rate intensity, diffusate flow rate intensity, dialysate flow rate intensity, and initial feed composition (HCl and AlCl3 concentration) on diffusion performance were investigated. The results showed that the acid recovery ratio and aluminum leakage ratio decreased with an increase in the flow rate intensity. And for a diffusion dialysis process, an appropriate flow rate intensity ratio (diffusate:dialysate) was found to be approximately 1.0. The HCl concentration in the feed was observed to have little influence on the diffusion performance of SWDD membrane module, while the acid recovery ratio and aluminum leakage ratio increased as the AlCl3 concentration in the feed increased. More than 95% HCl were recovered from the simulated wastewater which contained 2.12 mol/L HCl and 0.8 mol/L AlCl3 at the flow rate intensity of 0.48 L/(m2 h). When compared with plate-and-frame diffusion dialysis (PFDD) membrane module, the SWDD membrane module has a higher acid recovery ratio, lower metal leakage ratio, higher loading density, and similar time to reach the equilibrium. Preliminary economic evaluation revealed that an investment in this process could be recovered within 16.5 months.