Synthesis of porous carbon/zeolite composites by low-temperature acid-alkaline leaching from coal gasification fine slag for adsorption of dye wastewater

The conversion and utilization of coal gasification slag is considered one of the key issues in the development of the modern coal chemical industry. In this work, porous carbon/Na-P1 zeolite composites were successfully prepared by a simple and easy-to-operate acid-alkali leaching method on the basis of the composition of coal gasification fine slag. The synthesized CZ-10 possessed a honeycomb-like porous carbon structure and a typical flower-cluster zeolite structure, with the specific surface area and pore volume reaching 195.68 m2/g and 0.257 m3/g, respectively. CZ-10 showed excellent adsorption performance, with an equilibrium adsorption capacity of 175.93 mg/g on methylene blue (MB) at 300 K. CZ-10 can effectively adsorb MB in a wide pH range, and the increase in pH was favorable for adsorption. According to the results of adsorption kinetics and isothermal adsorption experiments, the adsorption process was in good agreement with PSO model and Sips model. According to the characterization results and adsorption experiments, it was speculated that the adsorption of CZ-10 on MB was mainly chemisorption, and may be affected by various factors such as ion-exchange, electrostatic attraction, hydrogen bonding, π-π bonding and van der Waals forces.