Abstract: The present invention relates to colloidal suspensions of discrete particles of colloidal zeolite and a method for preparing such zeolite from clear tetraalkylammonium stabilized aluminiumsilicate solutions. Smaller amounts of well defined and controlled metal hydroxide solutions are added to these alumiumsilicate solutions to enable the synthesis of a specific zeolite as well as to control zeolite yield. The colloidal suspensions are characterized by an average particle size of less than 250 nanometers and preferably, less than 200 nanometers together with the fact that the particle size distribution expressed as the geometric standard deviation is less than 1.30 and preferably less than 1.20. Zeolite sols synthesized according to this invention display Tyndall light scattering typical for colloidal suspensions as well as a very low rate of sedimentation due to the small particle size.

Abstract: The invention concerns a process for the synthesis of zeolites based on element(s) T and mesoporous solids based on element(s) T, T being silicon and/or aluminium, comprising the following sequence of steps:i) synthesizing a reaction medium which is a homogeneous source of element(s) T containing:a) at least one source of element(s) T selected from the group formed by aqueous basic solutions of silica or silica and alumina and alcoholic solutions of alkyl tetraorthosilicate and trialkoxyaluminium;b) optionally, at least one structuring agent;c) optionally, seeds of the desired crystalline phase;ii) heating the reaction medium to a temperature in the range 20.degree. C. to 220.degree. C. for a period in the range several minutes and several days;iii) injecting at least one chemical agent at a controlled rate to generate polycondensable species in said medium.

Abstract: A method for immobilizing waste chloride salts containing radionuclides such as cesium and strontium and hazardous materials such as barium. A sodalite intermediate is prepared by mixing appropriate amounts of silica, alumina and sodium hydroxide with respect to sodalite and heating the mixture to form the sodalite intermediate and water. Heating is continued to drive off the water to form a water-free intermediate. The water-free intermediate is mixed with either waste salt or waste salt which has been contacted with zeolite to concentrate the radionuclides and hazardous material. The waste salt-intermediate mixture is then compacted and heated under conditions of heat and pressure to form sodalite with the waste salt, radionuclides and hazardous material trapped within the sodalite cage structure. This provides a final product having excellent leach resistant capabilities.