A mathematical model for ammonium removal and recovery from real municipal wastewater using a natural zeolite

A study was carried out to remove/recover ammonium (NH4+) from residual effluents in tertiary treatment by sorption/desorption processes onto a natural clinoptilolite zeolite (NZ) in batch and fixed-bed column systems. Batch equilibrium and kinetic experiments were performed at different loading of NZ and contact time intervals, respectively. The results obtained in batch were fitted by the Freundlich and Langmuir isotherms and mass action law model. The Freundlich isotherm showed better agreement with experimental data than the Langmuir model. The isotherm studies revealed a type III with a maximum capacity of 2.8 ± 0.2 mg/g at 40 mgNH4+/L. Moreover, the data from the fixed-bed column studies was well fitted by a mass transfer model, considering the intraparticle diffusion resistance given by the linear driving force model (LDF). Finally, the capacity of NH4+ recovery of activated zeolite was measured experimentally and by a robust dynamic desorption model. The column desorption results demonstrated that higher recoveries (92–99.99%) were observed when increasing the flow rate to 0.12 mL/min. The uniqueness of this study is its capability to simulate both the sorption and desorption processes of the naturally derived sorbent for the effective removal and recovery of NH4+-N from real wastewater stream.