Transport of organic dyes through ether-type polyurethane membrane

Transport of various anthraquinone, acidic and basic dyes in aqueous solution through ether-type polyurethane membrane has been studied to better define the factors affecting the removal of organic compounds by the polyurethane membrane and to complement the previously proposed sorption mechanism. The effects of pH, salts, dye geometry and size, initial dye concentration, thickness of the membrane, and solution temperature on the rate of transport were investigated. Transport was found to be dependent upon the pH conditions of the starting and the receiving solutions. An increased rate of transport was observed with increased solution temperature and with the use of a thinner polyurethane membrane. The differences in the rates of transport can be attributed to the relative solubility of the organic dyes in the membrane and in solution, and to the strength and extent of intermolecular interactions with the polymer. Dye concentration, geometry and size, and the presence of salts in solution had no significant effect on the rate of transport. All of the studied dyes were found to exist as neutral species in the membrane.