USE OF ION EXCHANGE COMPOSITES BASED ON NATURAL ZEOLITES FOR CLEANING OF WATER SOLUTIONS WITH PURPOSE TO CREATE ENVIRONMENTAL SAFE TECHNOLOGIES
Advancing the chemical engineering fundamentals
Electrochemical Engineering - I (T2-14a)
Keywords: zeolites, synthesis, radioactive elements, sorption, cleaning.
In many cases creation of the effective systems for the cleaning of water solutions, polluted with radioactive elements and heavy metals, for example, realization of processes of extraction of radionuclides from waste, deactivation and cleaning of waste waters, water preparation, is connected with necessity of use of sorption materials with given properties. Sorption processes have the advantages before other methods (for example, such as evaporation and precipitation), as they are more effective at large volumes of solution, do not bring in the difficulties, caused by corrosion of the equipment and in majority of cases provide additional clearing of corrosive impurity and products of division.
This work is devoted to development of methods of a controlled synthesis, the study of properties and the application of ions exchanging composites on the basis of cheap natural zeolites with the structure of clinoptilolite, but having better characteristics in comparison with them. Existing data on ion exchange properties of clinoptilolites show that these zeolites can be used for extraction of ions of heavy metals from water solutions, radionuclides of cesium and strontium. And capacity of clinoptilolite on cesium, for example, is almost 30 times as high as that one of ion-exchanged resins.
By modifying chemical structure of natural zeolites, namely clinoptilolites of two effusion-sedimental deposits (Dzegvi and Tedzami – Georgia) by the ion exchanging method calcium, magnesium, ammonium and hydrogenous forms with different degree of replacement of cation exchange were synthesized. To predict the superficial adsorption interactions for obtaining sorbents with the given properties and the target-oriented performance of sorptions processes from water solutions taking into account Lewis’s and Brensted’s theory, the investigation of the origin of distribution of acid-base centers and their concentration on the surface of synthesized sorbents has been done with the help of an indicator method. The comparative characteristic of sorption properties of ion exchanging verities of natural zeolites and their initial forms is received. Prospects of using a number of cation-replaced forms of clinoptilolites are shown for extraction cesium and strontium from water solutions at low concentrations of these elements.
On the basis of the fulfilled researches it has become possible to make practical recommendations for replacement of natural clinoptilolites on their ion-exchanged derivatives in various ion exchange technologies. In connection with huge scales of such branches as water preparation, clearing of turnaround and waste waters with the help of cheap natural zeolites can greatly provide the growing industrial needs of ion exchange materials. Besides that natural zeolites can be widely used in processes not dealing with sorbent regeneration because of their low cost. Having high radiating stability and resistance to leaching synthesized ion exchangers represent also practical interest for providing safety of an environment in case of their burial after utilization. It is also necessary to take into account ample opportunities of simultaneous multitarget use of natural zeolites not only as ionite but also as adsorbent and filtering material in various technological processes and environmental protection measures.
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Presented Tuesday 18, 12:00 to 12:20, in session Electrochemical Engineering - I (T2-14a).
