In Situ Synthesis of Magnetic Zeolite A From Coal Gangue and Its Adsorption Properties for Cu2+

Due to the abundant SiO2 and Al2O3 content in coal gangue (CG), the synthesis of zeolite from CG has become a route to realize the high-value utilization of CG. However, some impurities contained in CG, such as iron oxide and carbon, have an adverse impact on the crystallization and application of zeolites. In this work, we propose a strategy to directly convert CG into magnetic zeolite without the need for an external magnetic source. Carbon in CG is calcined to in situ reduce iron oxide to magnetite. This is followed by the hydrothermal reaction to synthesize magnetic zeolite A. Effects of m (NaOH)/m (CG), alkali fusion temperature, crystallization temperature, and time on the synthesis of zeolites are investigated. The synthesized zeolite A is magnetic and exhibits the cubic morphology with rounded corners, having a particle size of about 2 mu m. The maximum adsorption capacity and removal ratio of magnetic zeolite A for Cu2+ are 91.74 mg/g and 98.50%, respectively. The solid-liquid separation test after adsorption shows that the magnetic zeolite A could achieve the accelerated solid-liquid separation within 15 min. This work provides a pathway to realize comprehensive utilization of CG and demonstrates a good adsorbent for practical application of highly efficient adsorption separation.