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(4)(+) in zeolite-filled, fixed-bed columns. Breakthrough experiments were performed in single- and multi-sorbate systems with the initial K(+) and NH(4)(+) 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(4)(+) sorption was provided by the Freundlich sorption model (R(2) = 0.99), while unfavorable sorption was determined for K(+) (n(F) = 2.19). Intraparticle diffusion was identified as the rate limiting step for NH(4)(+) 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(4)(+) breakthrough level of 50%. The concentrations of K(+) and of dissolved organic carbon (DOC) were identified as the main parameters that determine NH(4)(+) 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(4)(+) in zeolite-filled, fixed-bed columns.