Use of fibrous and granular ion exchangers for obtaining micro- and nanodispersions of silica

Abstract

The article is devoted to obtaining micro- and nanodispersions of silica using fibrous and granular ionites. Experiments using cationite КУ-2-8, sulfocarbon, Fiban K-1 and wood (coniferous) sulfate cellulose previously modified by the authors by phosphorylation have been carried out. Systems based on liquid glass and distilled water containing 3, 6, 10, 20 and 30% (by weight) SiO₂ were used for the experiments. Silica sols were obtained by the ion exchange method in static and dynamic modes with different ratio “liquid glass : ionite”. In order to study the behavior peculiarities of silica sols obtained in dynamic mode the kinematic viscosity changing was estimated within 2 months after their preparation. Additionally, experiments using cationite КУ-2-8 regenerated with 10 % H₂SO₄ followed by washing to neutral рН have been carried out. The silica sols stability was estimated visually and by turbidimetrical method. The particle size of obtained samples was determined by laser diffraction method, the morphology of xerogels SiO₂ was studied by scanning electron microscopy. The results of IR-spectroscopy indicate the presence of bands generally characteristic of amorphous hydroxylated silica in obtained samples. It has been shown that more stable dispersions based on “liquid glass –water” systems containing 6% (by weight) SiO₂ were formed. It has been found that the particle size of silica sols depended on the ionite type: fibrous cationites allowed obtaining colloidal systems with a smaller particle size and greater homogeneity compared to granular ones. It has been showed that modified cellulose was a promising material for obtaining nanodispersions of silica. The possibility of regenerated cationite using has been demonstrated. The latter is an advantage from an economic point of view. It has been shown that the viscosity of solutions when silica sols obtaining in dynamic mode could be managed by taking a certain volume of solution at the outlet of ion exchange column. The practical significance of obtained results lies in the expansion of range of polishing compositions based on SiO₂ for their application in electronic industry for chemical-mechanical polishing of semiconductor wafers. It makes possible to abandon expensive imported materials in the future and to reduce the cost of final product manufacturing.