Ammonium removal from aqueous solutions by zeolite adsorption together with chemical precipitation

The aim of this study was to remove ammonium from aqueous solution and recycle ammonium. Ammonium removal from aqueous solution by natural and pretreated zeolites, breakthrough curve, chemical regeneration of pretreated zeolite, ammonium removal from regeneration solution by chemical precipitation and NH₄⁺ adsorption isotherms were investigated by conducting a series of batch and continuous experiments in this study. Morphologies and structures of zeolites were analyzed by Surface Area and Pore Size analysis, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The NH₄⁺-N removal efficiencies by natural and NaCl-treated zeolite were 30.73% and 85.55% respectively at an initial concentration of 100 mg/L. Breakthrough and exhaustion capacities for adsorption of ammonium ions were 3.36 and 4.26 mg /g (NH₄⁺-N/zeolite), respectively. After chemical regeneration, NH₄⁺-N removal efficiency by NaCl-treated zeolite only reduced 9.95% than previously. NH₄⁺-N concentration of the regeneration solution was reduced from 460 to 74.55 mg/L by chemical precipitation. The Freundlich isotherm provided a slightly more consistent fit to the experimental data of ammonium adsorption on NaCl-treated zeolite than Langmuir. Based on the results, it was concluded that the objective of this study had been well achieved.