Zeolite–Ammonium interactions: the physical-chemistry of the desorption process

Zeolites are naturally occurring volcanogenic minerals formed as a result of complex chemical and physical processes in rocks undergoing various changes in nature [1]. The structural characteristic and mineralogy of the zeolite influence their cation exchange capacity and consequently their ability to remove ammonium (NH4+) from an aqueous solution [2]. Natural zeolites have been explored as an effective adsorbent for nutrient removal from wastewater. Nutrient enriched zeolites may be then reused as slow releasing fertilizer or undergone to a regeneration process to recover nutrient such as NH4 + in a circular economy perspective [3]. The regeneration of zeolites can be carried out by different methods. The most popular regeneration technique is commonly achieved using ionic brines, e.g., sodium chloride (NaCl), where the Na+ ion replaces the adsorbed NH4 + by releasing it into the liquid phase [4]. In this study, the ability of two zeolites with different mineralogy in desorbing ammonium (NH4+) following a treatment with 1 M NaCl solution was assessed. The physicalchemistry of NH4+ desorption process was studied by static desorption tests and desorption kinetics.