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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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One of the homogeneous catalytic systems proposed for the degradation of organic dyes in wastewater is the Fenton reagent (Fe2+/Fe3+/H2O2). Significant disadvantages of Fenton's reagent are the inability of its regeneration, the narrow intervals of pH at which are oxidative transformations of organic compounds and the necessity of extracting metal ions from the purified water. The use of heterogeneous catalysts, in particular zeolites, separation from water and regeneration which is not particularly difficult, can solve most of these problems. In addition to iron, other transition metals can also catalyze the formation of hydroxyl radicals from H2O2. In turn, the disadvantage of heterogeneous catalysts is their instability in aqueous solutions, as in use there is leaching of active components in solution. The degree of elution depends on the nature of the active components and the carrier, as well as conditions of catalysis. To date, the question of stability of the catalyst remains open. Developing a sustainable catalytic systems containing transition metals, for oxidation of organic contaminants in wastewater is important. General requirements for a heterogeneous catalyst are resistant to oxidizing environments, accessibility for interaction with hydrogen peroxide present in the solution. Such factor as sorption capacity of the solid phase relative to the organic substrate also plays a significant role. It is desirable that the contribution of sorption in the set of all occurring processes in the system was negligible. It would be optimal to formation of hydroxyl radicals was carried out on the surface of the catalyst, and the oxidative degradation of organic compounds takes place in solution, the ions of the transition elements in solution is not passed. On the basis of granulated synthetic zeolites NaY and HY without binders by means of ion exchange followed by heat treatment at 350-500 оС samples of cobalt and iron catalysts were obtained, which showed activity in the oxidation of organic dyes with hydrogen peroxide. By XPS it was shown that cobalt and iron are on the surface of the carrier in the form of ions Co2+ and Fe3+. The experiments showed that the temperature of calcination of zeolites in the studied range has little effect on the degree of discoloration of the dye. According to the results of research of influence of pH on the catalytic oxidation carmoisine found that the catalysts FeHY and CoNaY most effective and stable under the oxidation of the anionic dye carmoisine in weakly acidic and alkaline media. Assume that a heterogeneous Fenton-type process in wastewater treatment technology will be carried out before biological treatment, which is carried out at pH values of 6-9. Therefore, the catalysts CoNaY and FeHY because of their high catalytic activity and stability in weakly acidic and alkaline media may be promising for application in the process of oxidative degradation of organic dyes by hydrogen peroxide with subsequent biological purification.