From Waste to Added-Value Product: Synthesis of Highly Crystalline LTA Zeolite from Ore Mining Tailings

Abstract

The use of wastes is necessary to contribute to environmental sustainability. In this study, ore mining tailings were used as the raw material and precursor for the synthesis of LTA zeolite, a value-added product. Pre-treated mining tailings were submitted to the synthesis stages under specific established operational conditions. The physicochemical characterization of the synthesized products was performed with XRF, XRD, FTIR and SEM, to identify the most cost-effective synthesis condition. The LTA zeolite quantification and its crystallinity were determined as effects of the SiO2/Al2O3, Na2O/SiO2 and H2O/Na2O molar ratios used, as well as the influence of the synthesis conditions: mining tailing calcination temperature, homogenization, aging and hydrothermal treatment times. The zeolites obtained from the mining tailings were characterized by the LTA zeolite phase accompanied by sodalite. The calcination of mining tailings favored the production of LTA zeolite, and the influence of the molar ratios, aging and hydrothermal treatment times were determined. Highly crystalline LTA zeolite was obtained in the synthesized product at optimized conditions. Higher methylene blue adsorption capacity was associated with the highest crystallinity of synthesized LTA zeolite. The synthesized products were characterized by a well-defined cubic morphology of LTA zeolite and lepispheres of sodalite. The incorporation of lithium hydroxide nanoparticles over LTA zeolite synthesized (ZA-Li+) from mining tailings yielded a material with improved features. The adsorption capacity towards cationic dye was higher than for anionic dye, especially for methylene blue. The potential of using ZA-Li+ in environmental applications related to methylene blue deserves detailed study.