Anion exchange membranes used in diffusion dialysis for acid recovery from erosive and organic solutions

Diffusion dialysis (DD) is a process that the solutes pass through the ion exchange membrane from the feed side to water side. Some solutes such as HCl-FeCl2 may be erosive on membrane structure during practical DD process. The erosion effects are investigated by four anion exchange membranes, including commercial membranes DF-120 and 9010, and our previous membranes based on quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO) and polyvinyl alcohol (PVA). Besides, the membranes are also used to separate organic solution containing HCl and glyphosate, which is produced largely during the preparation of glyphosate pesticide. The membrane structures are damaged and their performances are reduced after the erosion of HCl-FeCl2, which are mainly attributed to the loss of -N+(CH3)(3)Br- and -OH groups. The weight loss percent is in the range of 10-21%, the ion exchange capacity decreases but the swelling degree increases. The dialysis coefficient of HCl (UH-1) and separation factor (S-1) reduce to 0.006-0.010 m h(-1) and 13.9-15.5 for commercial membranes, and 0.016-0.024 m h(-1) and 33.2-47.6 for QPPO/PVA membranes, correspondingly. Besides, the membranes without erosion are used to separate organic solution containing HCl and glyphosate. The UH-2 is in the range of 0.0040-0.0062 m h(-1) for commercial membranes, and 0.0094-0.0104 m h(-1) for QPPO/PVA membranes. The UH-2 values are generally stable within 10 h, and the acid concentration in the feed side decreases from 5.82 to 3.16 mol L-1. Hence, the QPPO/PVA membranes can be potentially applied in DD process to recover acid from organic solution containing HCl and glyphosate. (c) 2013 Elsevier B.V. All rights reserved.