In situ synthesis of zeolite FeZSM-5 derived from coal gangue for phenol degradation

Abstract

Coal gangue (CG) is a waste product generated during coal mining, the comprehensive utilization of which plays a critical role in the sustainable development of the coal chemical industry. By fully utilizing silicon, aluminum, and iron sources present within CG, CG was directly converted to zeolite FeZSM-5 by an in situ hydrothermal method, avoiding the complicated operation of adding additional iron sources. The effects of n(Na₂O)/n(SiO₂), n(H₂O)/n(SiO₂), crystallization temperature and crystallization time on the synthesis of zeolite FeZSM-5 were studied. The obtained coffin-shaped zeolite FeZSM-5 had a particle size of about 5 µm and a high crystallinity. Compared with zeolite FeZSM-5 synthesized using chemical reagents, zeolite FeZSM-5 synthesized from CG had higher active iron content and a larger specific surface area and pore volume, which provide more active sites with their accessibility for phenol degradation. The synthesized zeolite FeZSM-5 was employed to catalyze phenol degradation. The effects of pH, reaction temperature, H₂O₂ concentration and zeolite dosage on the removal ratio of phenol were investigated. The results showed that the phenol removal ratio of zeolite FeZSM-5 was 97.43 ± 0.21%, and the recovery stability was evaluated. This work gives a new insight into comprehensive utilization of CG and exemplifies the environmentally friendly principle of waste control by waste.