Transparent, stable titanium dioxide sols

摘要

Disclosed is a method for preparing a stable, transparent photocatalytic titanium dioxide sol, comprising: (i) providing a solution comprising a titanium containing compound; (ii) precipitating hydrous titanium dioxide from said solution of a titanium containing compound; (iii) forming an aqueous dispersion of said precipitated hydrous titanium dioxide; (iv) mixing said aqueous dispersion in the presence of one or more alphahydroxy carboxylic acids at a temperature between about 70°C and about 150°C for a period of time between about three hours and about 3 days; with the proviso that said one or more alpha-hydroxy carboxylic acids are essentially free of glycolic acid; thereby providing a sol of titanium dioxide which is stable and transparent at every pH throughout the pH range of 2 to 12; said sol comprising crystallites of titanium dioxide having an average particle size of less than about 10 nm, the majority of said crystallites being in anatase form.