Uphill transport of organic electrolytes using polyethylene films photografted with 2-(dimethylamino)ethyl methacrylate

Abstract

Uphill transport of organic electrolytes, benzoic acid, benzenesulfonic acid, and p-aminobenzoic acid, was examined using polyethylene films photografted with 2-(dimethylamino)ethyl methacrylate (DMA). The transport fractions had the maximum values around the grafted amount of 5.0 mmol/g at which the ungrafted layers in the inside of DMA-grafted PE (PE-g-PDMA) films disappeared. Uphill transport of organic anions from the acidic to the alkaline sides occurred most favorably only when the initial pH value in the alkaline side was adjusted to 12.0 while the initial pH values in the acidic side agreed to the pH values of each aqueous solution of the organic electrolytes at 10 mmol/dm3. Under these conditions each organic electrolyte was concentrated by 1.7–1.8 times the initial concentration. In case either the initial H+ or OH- ion concentration was too high or low, the transport fractions of organic anions decreased. When the initial pH value in the acidic side was decreased to 1.5, p-aminobenzoic electrolytes were transported from the alkaline to the acidic sides and the transport fraction amounted to 80%. It was experimentally confirmed that the pH difference across the PE-g-PDMA films was a driving force for uphill transport of organic anions.