Synergistic effect in 3D chitosan scaffold reinforced with nanocellulose and magnetic bentonite for the adsorption of Reactive Red 31 (RR31) dye pollutant.

Industrial effluents containing toxic compounds pose serious environmental threats, including ecosystem disruption, bioaccumulation in aquatic organisms, and long-term soil and water contamination when discharged untreated into natural water bodies. In this study, a multifunctional chitosan (CH) scaffold with a mesoporous structure was developed as an affordable and sustainable adsorbent system for the removal of organic dyes from wastewater. The proposed approach involved integrating the CH-scaffold with suitable fillers, such as spherical nanocellulose (SN), bentonite (BT), and magnetic bentonite (MBT) during fabrication to enhance adsorption capacity. The resulting materials were thoroughly characterized using XPS, FTIR, XRD, DC magnetic measurements, morphological analysis, particle size distribution, ζ-potential, EDX, and WCA to confirm the structural features of the CH-scaffolds. The systematic investigation and optimization of key dye removal parameters, including initial dye concentration (25-200 mg/L), contact time (15-1440 min), adsorbent dosage (0.625-5.000 g/L), solution pH (3-11), and temperature (298-328 K), were performed. Adsorption effectiveness increased with an increase in time, adsorbent dose, and temperature for Reactive Red 31 (RR31). Reactive Red 31 (RR31) and methylene blue (MB) were selected as model dye pollutants representing anionic and cationic dye classes, respectively, to evaluate the adsorption performance of the chitosan-based scaffold composites. The proposed adsorption mechanism of dyes onto the CH/SN/MBT scaffold involves synergistic electrostatic interactions, hydrogen bonding, π-π interactions, and surface coordination via Fe3+. The rate and mechanism of RR31 adsorption were evaluated using various nonlinear kinetic adsorption models, including the pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich, intraparticle diffusion (IPD), and Bangham models. Additionally, four nonlinear isotherm models were employed to characterize the equilibrium adsorption behavior: Langmuir, Freundlich, Temkin, and Sips. The fabricated scaffolds show excellent regeneration ability remains with RR31 underapplying our experimental conditions for several cycles.