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 (radical dotOH) 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 ∼40 wt% H2O2; the process was studied at 25 °C, 30 °C and 35 °C. CMS-7 displayed a higher flux than CMS-3; a reverse trend was observed for water–H2O2 selectivity for the same feed concentration. The highest water–H2O2 selectivity of ∼12 was observed in CMS-3 membrane at an H2O2 concentration of 43 wt% with a total flux of 6.15 × 10−3 g/h cm2; for CMS-7, values of 9.2 and 9.6 × 10−3 g/h cm2 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.