Synergistic preparation of zeolite A from coal gasification coarse slag and red mud for the adsorptive removal of organic dyes

The conversion of industrial solid waste into advanced functional materials is of great importance to the sustainable development of modern industry. In the present work, coal gasification coarse slag and red mud were employed for the synergistic synthesis of zeolite A by hydrothermal crystallization after alkali fusion treatment. The appropriate reaction conditions were systematically explored, and the results demonstrated that the optimum conditions could be achieved with the molar ratio of Si/Al of 1.03, the ash-alkali ratio of 1:1, and the hydrothermal temperature of 358 K. The obtained zeolite A was adopted to purify simulated wastewater by using organic dyes as model pollutants, and the removal efficiency can reach more than 99.9 % for malachite green. The malachite green adsorption behavior followed the Freundlich and Temkin isotherm models and the second-order kinetic model, and the adsorption process was spontaneous and endothermic. Besides, the effects of contact time, temperature, dosage, pH, and interfering ions on the adsorption were investigated in detail. Based on the experimental results, the plausible adsorption mechanisms may include electrostatic interaction, hydrogen bonding, and physical encapsulation. This research provides a novel idea for the upcycling of solid waste to advanced adsorbents and is a valuable reference for wastewater treatment.