Industrial recovery of mixed acid (HF + HNO3) from the titanium spent leaching solutions by diffusion dialysis with a new series of anion exchange membranes

The results of the development of the industrial diffusion dialysis technology and the unit based on it for mixed acid recovery from titanium metal processing have been considered. Mixed acid can be selectively separated from the spent liquor contained mainly HNO3, HF and titanium ions by diffusion dialysis using a new series of anion exchange membranes. The results showed that this separation is seriously affected by the membrane water content and ion exchange capacity (IEC). Some titanium complex anion (TiF6)2− give rise to the difficulty in separation so that the best separation efficiency does not occur at the cases of high water content and IEC of membranes. By controlling the membrane preparation conditions (bromination content and position), a desired membrane for this system has been obtained with both relatively high acid recovery ratio and acid/titanium selectivity.