Green synthesis of zeolite and its regeneration for adsorption of ammonia nitrogen in water

This study presents a novel green approach for the preparation of zeolite material from fly ash using a combination of mechanochemical method. Compared to traditional methods, this approach reduces energy consumption, minimizes reagent usage, and facilitates the efficient recycling of fly ash. The physicochemical properties of the synthesized zeolite, including crystal structure and porosity, were systematically investigated. The synthesized zeolite was employed for the adsorption of ammonia nitrogen from aqueous solutions, and their adsorption kinetics and thermodynamics were comprehensively studied. The results revealed that the adsorption of ammonia nitrogen onto the zeolite follows the Langmuir adsorption model. Additionally, the zeolite exhibited strong selective adsorption and remarkable resistance to interference from coexisting cations in the aqueous solution. Finally, regeneration experiments were conducted using NaCl, NaClO, and their mixtures to desorb ammonia nitrogen from the spent zeolite. A total of 17 regeneration cycles were performed until the adsorption capacity of the zeolites was exhausted. The adsorption performance of the regenerated zeolite was evaluated to assess the impact of different reagents and regeneration cycles on adsorption efficiency. The optimal regeneration method was identified, leading to the successful valorization of fly ash into zeolite for ammonia adsorption and the development of effective regeneration strategies for spent zeolite.