Production of zeolitic materials in pilot scale based on coal ash for phosphate and potassium adsorption in order to obtain fertilizer

Abstract

The use of different types of zeolites (X, Na-P1, and 4A) synthesized by different methods and scales were tested in this work to adsorb nutrients present in synthetic solutions and industrial effluents for later application as fertilizer. Modifications with calcium chloride were performed on the zeolite with the best performance to increase its adsorption capacity. The best performing zeolite was type X (ZXH) produced on a pilot scale by the hydrothermal process. Its adsorption capacity without modification was 149 mg P-PO4/g zeolite and 349 mg K/g zeolite. With the change, there was a fourfold increase in these results, which were up to threefold higher than reported in the literature. The kinetic model that best characterized the adsorption process was the intraparticle diffusion model, and the equilibrium isotherm was that of Freundlich. The adsorption tests performed with industrial effluent showed high removal of the nutrients of interest (> 90% for PO43− and > 95% for K+). The desorption tests with zeolites nutrient-loaded from synthetic solutions showed 13 to 24% PO43− and 14 to 47% K+ release within 24 h, while for zeolite nutrient-loaded from effluent the release were 7 and 100% for PO43− and K+, respectively. The results we obtained in this work indicated the potential use of zeolites in the treatment of effluent and its application as a fertilizer.