MICROW AVE-ASSISTED SYNTHESIS OF LOW-SILICA/ALUMINA-RATIO ZEOLITES FROM GEOTHERMAL SILICA

Abstract

Zeolites A, X, hydroxysodalite and Iiydroxycancrinite (ZA, ZX, ZS, and ZC, respectively) were obtained using geothermal silica (GS) as a raw material and microwaves (MW) as an energy source. GS is an industrial byproduct from the Cerro Prieto geothermal plant in Baja California, México. It is a potential raw material for zeolite manufacturing because of its chemical composition and its high reactivity given by its small particle size. First, GS was treated with NaOH to generate zeolite precursors; the resulting products were crystallized by MW using sodium alumínate to adjust the SiO2/Al2O3 ratio in the reaction mixture. An experimental design based on an orthogonal array was employed to study the effects of the main factors involved in the zeolitization process of GS. The obtained yields of zeolites ZC, ZA and ZS were 95, 97, and 76.6% respectively. These zeolites were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence (XRF), and their calcium binding capacity (CBC) was determined. The obtained results were similar to those of commercial zeolites.