Cesium and strontium exchange by the framework potassium titanium silicate K3HTi4O4(SiO4)3 x 4H2O

Potassium titanium silicate with a semicrystalline framework of the formula K3HTi4O4(SiO4)3 x 4H2O has been prepared under mild hydrothermal conditions and its protonic form, H4Ti4O4(SiO4)3 x 8H2O, was obtained by acid treatment of the potassium compound. A comparative ion exchange testing of the H4Ti4O4(SiO4)3 x 8H2O towards alkali and alkaline earth metals in a broad pH and concentration range was carried out. It was found that potassium titanium silicate is a moderately weak cation exchanger, possessing high ion exchange capacity (up to 4-5 meq/g) and showing preference for heavy alkali and alkaline earth metals uptake. The selectivity of K3HTi4O4(SiO4)3 x 4H2O towards Cs+ and Sr2+ ions in alkaline and acid media in the presence of competitive inorganic ions and certain organic compounds was also studied. The data obtained suggest that despite the existence of well defined tunnel structure with parameters fitting for cesium ion in the K3HTi4O4(SiO4)3 x 4H2O, potassium titanium silicate could remove cesium (and strontium) efficiently only under some specific conditions, namely, at pH close to neutral and in the absence of competitive ions and especially of organic complexing agents. (author)