THE CHEMICAL AND MINERAL COMPOSITION OF NATURAL ZEOLITES AND THEIR SORPTION PROPERTIES DURING OZONATION WITH DRAIN WATER FROM NUCLEAR POWER PLANTS

Abstract

The article reveals the regularities of the overall process of ozonolytic destruction of organic components of model drain water from nuclear power plants and sorption of imitators of the main dose-forming radionuclides (Cs — with the isotopic 137Cs label; stable isotopes of Co, Sr, Mn salts) by natural zeolite of the Sokyrnytsky deposit and sorption-reagent compounds — salts of ferrous and manganese (II). The chemical composition of the main elements of zeolite after ozonation with the addition of iron and manganese salts practically does not differ from the composition of natural zeolite. Its phase composition in the ozonation process in the presence of ferrum salts is represented by the main rock-forming mineral clinoptilolite and the secondary mineral — quartz. The main ferrum-containing phase on the zeolite surface is goethite. Secondary phases include Fe(II)-Fe(III) layered double hydroxides (Green Rust) and lepidocrocite, but their relative content is insignificant. For zeolites, after ozonation with the addition of both ferrous and manganese (II) salts, the main phases are clinoptilolite and quartz. Manganese-containing phases on the zeolite surface are represented by hausmannite Mn3O4, manganese (II) oxide, and manganese oxyhydroxide MnO(OH)2. The iron- and manganese-containing phases deposited on the surface of the zeolite in the process of ozonation are mainly characterized by a weakly crystallized or amorphized structure. The main sorbent of dose-forming radionuclides is zeolite, not the iron- and manganese-containing compounds that formed on its surface during ozonolysis. The maximum degree of sorption of 137Cs by zeolite is up to 90% when the concentration of Fe2+ is increased to 50 mg/dm3 or Mn2+ to 100 mg/dm3. The degree of cobalt sorption is 97.5% at the initial typical concentration of competing cations (Fe2+ — 5 mg/dm3; Mn2+ — 10 mg/dm3) and when Mn2+ concentration increases to 100 mg/dm3. The maximum degree of extraction of Sr2+ and Mn2+ is 99.4% and 99.9%, respectively. For effective extraction of 137Cs and Co2+ by zeolite in the ozonation process, an increase in the concentration of competing Fe2+ cations is permissible — 50 mg/dm3; Mn2+ — 100 mg/dm3 in solutions. The efficiency of extraction of Sr2+ and Mn2+ practically does not depend on the concentration of competing cations (Fe2+, Mn2+) in the drain water solutions.