High selectivity and affinity of synthetic Phillipsite compared with natural Phillipsite towards ammonium (NH₄⁺) and its potential as a slow release fertilizer

Abstract

Phillipsite (PHI) was synthesized in Na-K form, ion exchanged with NH₄NO₃ and compared with its natural counterpart. Zeolites were then characterized before and after ion exchange by X-ray diffraction, X-ray fluorescence, Thermo-gravimetric analysis and scanning electron microscopy. Ammonium exchanged Phillipsites were introduced as a soil amendment (2, 4 and 8% zeolite to soil loadings) to study the growth of maize (Zea mays) and compared with a control comprising NPK fertilizer added to soil. The affinity of the zeolite mineral Phillipsite for in the presence of other cations is demonstrated by soil nutrient status. Results demonstrated that synthetic Phillipsite had a very high affinity towards when introduced as a soil amendment, compared with its natural counterpart. Results were promising for ion exchange reactions in a zeolite-soil system, whereby cations present in soil exchanged for K⁺ more freely than present in the synthetic Phillipsite framework.

Keywords:

• synthetic/natural Phillipsite
• ion exchange
• high-selectivity
• high-affinity
• slow/controlled release