NH4+-Adsorption Characteristics of Zeolites Synthesized from Fly Ash

In recent years, much attention has been devoted to the synthesis of zeolites from fly ashes and their aAplpthlication for the adsorbents for ammonium ion concerning the effective usage of industrial waste. ogh it is well known that natural zeolites such as clinoptilolite and mordenite have very good ionexchangeability for NH4+, the characteristics of zeolites synthesized from fly ashes have been little known. In this study, NH4+-adsorption characteristics of zeolites synthesizedfrom fly ash were investigated. Phillipsite, analcime and hydroxysodalite were synthesized by hydrothermal treatment of fly ash with NaOH solution, and the amount of NH4+-adsorbed by these zeolites in ammonia solution was measured under various conditions. It was found that only phillipsite has very high ability for NH4+-adsorption among these three kinds of zeolites. Analcime and hydroxysodalite have very poor ability for NH4+-adsorption. The amount of NH4+-adsorption increased linearly with increasing the content of philli. p-site The amount of NH4+-adsorbed by 100% phillipsite was estimated to be 3.5 mmol/g by extrapolation of the linear relationship of NH4+-adsoebed vs. comtent of phillipsite. On the other hand, the amount of NH4+-adsoebed by 100% moedenite or A-type zeolite, Which are known as very good adsorbents for ammonium ion, measured under the similar condition was was 2.6 mmol/g. Therefore, it is concluded that phillipsite has higher ability for NH4+-adsorption than mordenite or A-type zeolite. The amount of NH4+-adsorbed by phillipsite changed with pH of ammonia solution, and showed a maximum at pH=6.5∼9.0.