Effect of salt on temperature-swing adsorption of nonionic surfactant withpoly(vinylmethyl ether) gel

The effect of salt concentration on temperature-swing adsorption of nonioni c surfactant Triton X-100 with poly(vinylmethylether) gel (PVMEG) was inves tigated with sodium salts of citrate, succinate, sulfate, hydrogen phosphat e, chloride and nitrate. With increasing salt concentration, the amount of Triton X-100 adsorbed on PVMEG increased and the critical temperature range across which the adsorbed amount of Triton X-100 drastically changed shift ed to the lower temperature side. The effects of salt type and concentratio n on temperature-swing adsorption process were evaluated in terms of effect ive adsorbed amount, midpoint temperature and temperature sensitivity. The effective adsorbed amount increased with increasing ionic strength up to a certain critical value depending on salt type, and then sharply decreased a bove the critical value. The dependency of midpoint temperature on ionic st rength below the critical value was different from that above the critical value. The temperature sensitivity became minimum at ionic strength around the critical value, The critical ionic strength was found to be depend main ly on the valence of ion.