Ammonia Adsorption and Desorption by Zeolite: The Effect of Particle Size and Flow Rate at the Case Study of Palermo University Water Resource Recovery Facility

The global population's continuous growth increased the agricultural output to meet escalating food requirements. Consequently, farmers resort to intensive fertilization practices, prominently featuring nitrogen as a key component. Moreover, many applied nitrogen fertilisers leach into freshwater systems, accelerating eutrophication and ecological disruptions. Addressing these challenges involves exploring solutions for nitrogen recovery from treated wastewater, rich in nutrient content, particularly ammonium (NH4+). Various chemical, biological, and physical techniques, including adsorption processes, offer potential solutions. Among them, zeolite-based adsorption is promising due to its high NH4+ adsorption capacity and environmental sustainability. In view of the above, this study aims to assess the adsorption capacity of zeolite with differing particle sizes and evaluate the impact of particle diameter on NH4+ adsorption efficiency from treated wastewater. Two zeolite sizes (0.5-1 and 2-5 mm) and three flow rates (1.18, 1.57 and 2.36 L/h) were tested, followed by desorption tests to validate material performance. The results demonstrated that increasing the flow rate enhances the adsorption capacity of both zeolites. Moreover, the 0.5-1 mm zeolite adsorbed approximately 60 mg more nitrogen than the 2.5 mm zeolite, highlighting the influence of particle size on adsorption capacity. A rapid nitrogen release and a slower progression over time characterised the desorption test.