One step reconstruction of carbon/P zeolite from coal gasification slag and its adsorption mechanism for crystal violet

The efficient resource utilization of coal gasification slag is a key issue that urgently needs to be addressed in the fields of energy, environmental protection, and sustainable development. As the main byproduct of the coal gasification process, the annual emissions of coal gasification fine slag are enormous. However, its traditional processing methods face technical bottlenecks such as difficulty in separating carbon ash, low atomic utilization rate, and severe secondary pollution, which seriously restrict its resource utilization efficiency. This study innovatively developed a one-step reconstruction technology for in-situ activation of coal gasification fine slag, and successfully prepared carbon/P-type zeolite composite materials (CPCMs), achieving efficient synergistic activation of silicon, aluminum, and carbon elements in fine slag under mild conditions. The composite material has a flower shaped multi-level pore structure with a specific surface area of 107 m²/g, mainly composed of mesopores. In addition, by regulating the alkaline leaching time and calcination conditions, P-type zeolite in CPCMs can be directionally converted into sodium cross zeolite. CPCMs exhibit excellent adsorption performance for crystal violet dye in water, with a maximum adsorption capacity of 454.6 mg/g at 303 K. Its adsorption behavior conforms to a quasi second order kinetic model, R² > 0.995, Indicating that chemical adsorption is dominant. The isothermal adsorption data is highly consistent with the Langmuir model, confirming the uniform adsorption characteristics of the monolayer. Thermodynamic analysis shows that the adsorption process is spontaneous endothermic, ΔG < 0, ΔH=33.92 kJ/mol, ΔS > 0. Mechanism studies have shown that adsorption is due to multi mechanism coupling: the mesoporous confinement effect and electrostatic attraction of P-type zeolite, and the adsorption capacity is significantly increased when pH > 7; π - π conjugation of residual carbon components; Ionic exchange and complexation between metal ions and crystalline violet cations in composite materials. It is worth noting that CPCMs maintain stable adsorption performance over a wide salinity range and exhibit good anti-interference ability. This study not only achieved high-value resource utilization of coal gasification fine slag, but also provided economically efficient adsorption materials for industrial wastewater treatment, which has important environmental and economic benefits.