Highly porous coral-like mesoporous carbon aluminosilicate composite from red mud waste and its ability towards methylene blue adsorption

This study describes the processing of red mud waste into carbon-aluminosilicate composites for the removal of methylene blue from wastewater. The composites were synthesized using the dual-hydrothermal method with cetyltrimethylammonium bromide surfactant and calcined in a nitrogen environment. The characterization results indicated the uniform and high porosity of the carbon-aluminosilicate composite with coral-like nanostructures. The adsorption ability of the composite was assessed under various conditions, encompassing adsorbent dosage, contact time, and starting adsorbate concentration. The results supported the adsorption isotherm of the Sips model, with a maximum capacity for adsorption (q_max) of 94.02 mg/g. The adsorption process exhibited a better fit with the Elovich and pseudo-second order kinetic models, confirming heterogeneous surfaces and that chemisorption regulated the adsorption process rather than physical adsorption. The parameter of thermodynamics revealed that the adsorption process occurred spontaneously and absorbed heat, indicating its endothermic nature. Notably, after five cycles, the adsorbent retained 82.26% of its capacity for MB, demonstrating the remarkable stability of the carbon-aluminosilicate composite. Spectroscopic investigations suggested that the primary interactions influencing adsorption are hydrogen bonding, π-π interaction, and electrostatic interaction. These results show that the carbon-aluminosilicate composite has the possibility of development as an economical adsorbent for dye removal.