Diêgo Nunes Faria

This work focuses on the effectiveness of removing ammonium from real municipal wastewater using synthetic faujasite (FAU-type) and β (BEA-type) zeolites and a commercial β (BEA-type) sample. The results demonstrated that synthetic samples presented enhanced performance on ammonium removal in comparison with commercial zeolite due to higher Al content and larger specific surface area, promoting better accessibility to active adsorption sites of the adsorbents. Synthetic FAU-type and BEA-type zeolites achieved a maximum adsorption capacity of 28.87 and 12.62 mg·g⁻¹, respectively, outperforming commercial BEA-type zeolite (6.50 mg·g⁻¹). Adsorption assays, associated with kinetic studies and adsorption isotherms, were better fitted using the pseudo-second order model and the Langmuir model, respectively, suggesting that chemisorption, involving ion exchange, and monolayer formation at the zeolite surface, was the main mechanism involved in the NH₄⁺ adsorption process. After ammonium adsorption, the NH₄⁺-loaded zeolite samples were used to stimulate the growth of tomato seedlings; the results revealed a change in the biomass production for seedlings grown in vitro, especially when the BEA_C_NH₄ sample was employed, leading to a 15% increase in the fresh mass in comparison with the control sample. In contrast, the excess of ammonium adsorbed over the BEA_S_NH₄ and FAU_NH₄ samples probably caused a toxic effect on seedling growth. The elemental analysis results supported the hypothesis that the presence of NH₄⁺-loaded zeolite into the culture medium was important for the release of nitrogen. The obtained results show then that the investigated zeolites are promising both as efficient adsorbents to mitigate the environmental impact of ammonium-contaminated water bodies and as nitrogen-rich fertilizers.