Critical parameters of silica supported ion exchange resins: the effect of pore size of silica on the surface area of the composite

摘要

Highly cross-linked (19-30percent) porous ion-exchange resin/ silica composites (cation as well as anion) wereprepared by dispersing monomers like styrene, 4-vinylpyridine, anddivinylbenzene together with diluents into the pore matrix of silica.Extensive work has been done to find out the effect of porevolume and average pore diameter (APD) of the silica support onthe surface area and porosity of the resulting organic composite. Itwas found that at the APD of >400A of silica there was anincrease in the surface area of the composite compared to thestarting material. also there was a cross-over region of the silicapores (~400A) where the surface area of the starting material doesnot change when it is converted into the organic composite. Theseresults are explained on the basis of smaller pores being cloggedand the formation of a porous structure within the organic polymercoated on the inner surfaces of the wide pore silica. The variationin the micro void volume ratio (#gamma#) of the resin with thepore size of the silica matrix is also described. These ion-exchangers have displayed high ~22Na~+/~23Na~+ self diffusioncoefficients of the order of 10~-7 cm~2/s. The composite apartfrom being determined for their pore volume (Vp), average porediameter (APD), surface area (S), porosity (#alpha#), and capacitywere specifically characterized for their outer resin volume ration(#mu#) and micro void volume ratio (#gamma#).