Natural Zeolites for the Sorption of Ammonium: Breakthrough Curve Evaluation and Modeling.

The excessive use of ammonium fertilizer and its associated leakage threatens aquatic environments around the world. With a focus on the treatment of drinking water, the scope of this study was to evaluate and model the breakthrough curves for NH in zeolite-filled, fixed-bed columns. Breakthrough experiments were performed in single- and multi-sorbate systems with the initial K and NH concentrations set to 0.7 mmol/L. Breakthrough curves were successfully modeled by applying the linear driving force (LDF) and Thomas models. Batch experiments revealed that a good description of NH sorption was provided by the Freundlich sorption model (R = 0.99), while unfavorable sorption was determined for K (n = 2.19). Intraparticle diffusion was identified as the rate limiting step for NH and K during breakthrough. Compared to ultrapure water, the use of tap, river, and groundwater matrices decreased the treated bed volumes by between 25% and 69%-as measured at a NH breakthrough level of 50%. The concentrations of K and of dissolved organic carbon (DOC) were identified as the main parameters that determine NH sorption in zeolite-filled, fixed-bed columns. Based on our results, the LDF and Thomas models are promising tools to predict the breakthrough curves of NH in zeolite-filled, fixed-bed columns.