Sustainable removal of congo red from tannery effluents using sugarcane bagasse-derived cellulose/bentonite composites: combined experimental, DFT, and molecular dynamics study.

/g. Batch adsorption experiments showed optimal CR removal at pH 4 using 30 mg of adsorbent, achieving a maximum adsorption capacity of 167.25 mg/g, significantly higher than raw bentonite (95.72 mg/g). Adsorption equilibrium and kinetics followed the Langmuir isotherm and pseudo-second-order model, while thermodynamic analysis indicated a spontaneous and endothermic process. Density functional theory (DFT) and molecular dynamics (MD) simulations revealed adsorption governed by n-π interactions, electrostatic attraction, and hydrogen bonding. The composite retained over 75% efficiency after five regeneration cycles and achieved 98% CR removal from real tannery wastewater, demonstrating its potential as a sustainable adsorbent for industrial effluent treatment.