Monitoring zeolite NaY formation from potassium-rich Nigerian kaolinite clay

Abstract

This work focuses on the successful synthesis of NaY zeolite from highly contaminated kaolinite clay, while investigating the effect of metakaolinization temperature and aging on role of potassium in zeolitization. The presence of potassium was observed to be responsible for formation of microcline, kalsite, and nepheline, which were found to depend on metakaolinization temperature and Si/Al ratio. The desirability function approach of the Response Surface Methodological (RSM) was used to optimized the favorable maximal and minimal conditions for metakaolinization and potassium based mineral removal. The intensity of microcline was employed as response, which gave optimal calcination temperature and time of 900 °C and 6 h, respectively. Synthesis of zeolite Y was observed to be favored at higher Na/Na + K ratio, adequate aging, low Si/Al ratio, even in the presence of some trace potassium. The optimal condition for zeolite Y formation was determined to be calcinations at 900 °C at holding time of 6 h, aged for 8 days and synthesized at 95 °C for 72 h. The zeolite NaY had cubicoshape with relative diameter of 15 μm, ion exchange capacity of 4.72–4.94 meq/g and specific surface area of 672 m2/g. Reproducibility study conducted on Elefun kaolinite clay gave a good crystalline phase of NaY type zeolite after 7 days of aging. The starting materials, intermediate and final products were characterized using X-ray florescence (XRF), X-ray diffractograph (XRD), scanning electron microscopy (SEM) and Branner-Emmet-Teller (BET) analyses.