SYNTHESIS OF PILLARED SMECTITES FROM HYDROUS METAL-OXIDE SOL SMECTITEMIXTURES UNDER REFLUX CONDITIONS

A novel method for the synthesis of pillared smectites (cross linked i ntercalated smectites) by refluxing a mixture of bentonite (2 wt%) and nano hydroxy aluminium oxide (boehmite, Al-O-OH) sol in aqueous mediu m is reported. Mixed sol containing boehmite and hydrous cerium oxide has resulted in mixed oxide pillared smectites. The various conditions of the intercalation are reported and the characteristics of the inte rcalated smectites have been evaluated using XRD, surface area analysi s and thermogravimetric techniques' The present method is shown to be effective in reducing the time of pillaring. High order of intercalati on 20 angstrom and specific surface area of 260 m2 g-1 are achieved by this method. Further, the possibility of handling a higher concentrat ion of the smectite, which has been a limiting factor in the usual met hods, is highlighted. The dielectric constants of the dried smectites after intercalation by reflux are compared with those prepared by usua l methods. The present technique of refluxing a mixture of mono ion ex changed smectite and hydrous metal oxide sols is novel due to its capa bility to intercalate smectites having high surface area, increased in terlayer spacing and also enhanced thermal stability.