The dynamics and equilibrium of ammonium removal from aqueous solution by Na-Y zeolite

Abstract

The ammonium removal from aqueous solution using Na-Y zeolite was investigated. The Na-Y zeolite was selected from a group of Beta, A, X, and Y zeolites, which were first screened to identify the best candidate for the ammonium removal. Among the considered zeolites, Na-Y and Na-X zeolites had the highest adsorption efficiencies, presumably due to a combination of their qualifying characteristics such as low Si/Al ratio, high surface area, and large pore size. The order at which the different investigated Y zeolites showed affinity for ammonium uptake was Na-Y >> Cs-Y ≈ K-Y > Mg-Y = Ca-Y > H-Y. For the Na-Y zeolite, it was found that the ammonium removal dynamics followed a pseudo-second-order kinetic model while the Langmuir adsorption isotherm fitted the equilibrium data well. Furthermore, it was deduced that the ammonium removal proceeded through two mechanisms: ion exchange and molecular adsorption. Three regeneration methods for restoring the adsorption efficiency of the spent zeolites were examined, and the best approach was found to be a combination of two methods, namely washing by saline water followed by distilled water. In brief, Na-Y zeolite was found to be a promising adsorbent for the removal of ammonium from freshwater.

Keywords:

• Y zeolite
• Ammonium removal
• Ammonium ion exchange
• Adsorption isotherm
• Adsorption dynamics
• Adsorbent regeneration

Acknowledgments

The authors express their appreciation to the Deanship of Scientific Research at the University of Bahrain for its financial support of the work conducted at the University of Bahrain.