Flexible textural design of ZSM-5 zeolite adsorbent from coal fly ash via solvent-free method for toluene elimination

Abstract

It is feasible and profitable to figure out multidiscipline environmental issues synergistically. Coal fly ash based adsorbent materials are widely used in the emission control of volatile organic compounds. A solvent-free method which was more environmental-friendly for ZSM-5 zeolites synthesis from coal fly ash was proposed to eliminate toluene. The results indicated that ZSM-5 zeolites were successfully synthesized from the precursor gel of coal fly ash with 30–60 wt% moisture contents. The SiO2/Al2O3 mole ratio of gel was up to 99 after the pretreatment of alkali roasting and acid precipitation. During the synthesis process, the appropriate Na2CO3-to-SiO2 ratio was 0.3, and the mesoporous formation would be facilitated along with the moisture content of gel. On the tendency of adsorption testing, the microporous structure was prone to the toluene adsorption, and the desorption was dependent on the mesoporous structure. The maximum adsorption capacity of 75.1 mg·g−1 was observed on S-40 sample, and the minimum desorption activation energy of 39.97 kJ·mol−1 was found on S-60 sample. The humid condition can reduce the toluene adsorption performance, and the maximum adsorption capacity was down to 63.7 mg·g−1. Additionally, the synthetic ZSM-5 zeolites still have some superiority in economics and ecology when compared with commercial zeolites. The novel synthesis method, preparing controllable ZSM-5 zeolites from coal fly ash with the advantages of low cost and environmental friendliness, exhibited the tremendous application potential in environmental field.