Desenvolvimento de materiais zeolíticos a base de cinzas de carvão para a adsorção de fosfato e potássio visando a obtenção de fertilizante

Abstract

The synthesis of zeolites from residues (fly ash) is pertinent, since their composition and formation make these materials attractive for application in various areas, such as in the treatment of industrial effluents and in agriculture. The objective of this work was to carry out the loading of different types of zeolites (Na-P1, A and X), obtained by different synthesis processes, with macronutrients (phosphorus and potassium) through synthetic solutions and with industrial effluent, in order to use the material obtained as a fertilizer. For this, tests of nutrient adsorption, desorption, solubility, pelletization and cultivation of Tagetes patula type flowers were carried out. The modification of zeolites with better adsorption performance with CaCl2, FeCl3, LaCl3 was also carried out in order to increase the adsorption capacity of nutrients. The zeolites that showed the best adsorption performance were type X (149 mg P-PO4/g zeolite and 349 mg K/g zeolite), produced by hydrothermal process in pilot scale. The most adequate adsorption kinetic model was the intraparticular one and the equilibrium data were better described by the Freudhlich isotherm. The material modification resulted in adsorption increases of up to 4-times (625 mgP-PO4/g zeolite) for PO4 and 2-times (427 mgK/gzeolite) for K, when compared to unmodified zeolites. Tests performed with industrial effluent showed high removal (> 90%) of the nutrients of interest. In the solubilization tests, the released nutrient concentrations were above those required by legislation (68% for PO4-2 and 33% for K2O) and the soil leaching tests indicated that the release is continuous, being greater in the first hours of contact. The development of Tagete patula was satisfactory, with some dosages resulting in better performance than commercial fertilizers. Pelletization tests were promising, not affecting chemical and crystalline properties. These results indicate that the use of zeolites in the adsorption of nutrients present in effluent is attractive and that the conditions for applying the material as fertilizer are favorable.