Efficient removal of methyl orange from water using biofunctional chitosan–cellulose composite: Experimental and DFT insights

In this study, a biofunctional composite, chitosan–GA–cellulose composite (CGAC), was synthesized through a cross-linking process involving chitosan and cellulose, using glutaraldehyde (GA) as the cross-linking agent. The final composite material was tested for the removal of the pollutant methylene orange dye. The structural and chemical properties of the carbohydrate-based composite were investigated using several techniques, including XRD, SEM, EDX, TGA and FTIR. The results show that the synthesized material has good textural properties and high temperature resistance. Equilibrium results were well described by the Langmuir isotherm. Under optimal conditions, specifically, an initial MO concentration of 100 mg/L, a contact time of 80 min, and a pH of 4.4, the maximum removal efficiency of MO reached 98.9 %, with an adsorption capacity of 324.62 mg/g. Even after five regeneration cycles, the removal efficiency remained high at 83.4 %, demonstrating the adsorbent’s strong reusability. To further understand the interfacial interactions and adsorption behavior of methyl orange (MO) on the synthesized CGAC composite, density functional theory (DFT) calculations were employed. These theoretical investigations provided a comprehensive understanding of the adsorption mechanism by elucidating the electronic properties, structural formation, and fundamental bonding interactions between MO and CGAC. The DFT analysis revealed critical insights into charge distribution, donor–acceptor interactions, and adsorption energy, offering a deeper perspective on the stability and efficiency of MO removal by CGAC material. The as-prepared carbohydrate-based composite exhibits significant potential for wastewater treatment because of its high adsorption efficiency, environmentally friendly composition, and sustainable nature.