Concentration of aqueous hydrogen peroxide solution by pervaporation

Pervaporative separation of corrosive liquids is always challenging in terms of finding a suitable polymeric membrane that can withstand the harsh environment especially when concentrating an aqueous solution of a highly oxidizing liquid such as hydrogen peroxide (H2O2). H2O2 is one of the most powerful oxidizers known and is a stronger oxidant than chlorine, chlorine dioxide and potassium permanganate; hydroxyl radical (*OH) generated from H2O2 has a very high reactivity. The choice of membrane material is potentially limited to fluoro polymers and perfluoro polymers considering membrane stability in such a harsh system. Perfluorodimethyldioxole-tetrafluoroethylene (PDD-TFE) copolymer membranes (CMS-3 and CMS-7) were used to concentrate hydrogen peroxide from its aqueous solutions. The feed solution composition was varied between 4 and similar to 40 wt% H2O2; the process was studied at 25 degrees C, 30 degrees C and 35 degrees C. CMS-7 displayed a higher flux than CMS-3; a reverse trend was observed for water-H202 selectivity for the same feed concentration. The highest water-H2O2 selectivity of similar to 12 was observed in CMS-3 membrane at an H2O2 concentration of 43 wt% with a total flux of 6.15 x 10-3 g/h cm(2); for CMS-7, values of 9.2 and 9.6 x 10(-3) g/h cm(2) were found for water-H2O2 selectivity and total flux, respectively, at the same H2O2 concentration. The total permeated flux increased with temperature at the cost of selectivity for both membranes. Extended-term behaviors of CMS-3 and CMS-7 membranes studied at 35 wt% H2O2 concentration indicated that both are quite stable for tests carried out over periods of 162 and 145 days respectively. (C) 2011 Elsevier B.V. All rights reserved.