Nanocellulose-Based Ecofriendly Nanocomposite for Effective Wastewater Remediation: A Study on Its Process Optimization, Improved Swelling, Adsorption, and Thermal and Mechanical Behavior

A nanocellulose (NC)-based cross-linked adsorbent has been employed herein for the removal of dye pollutants (e.g., methylene blue) from the textile industry. The synthesized hydrogel was optimized to achieve the best concentrations of the adsorbent constituents, i.e., 1.55% guar gum, 1.46% NC, and 0.84% borax for achieving the maximum swelling index (SI, 3741.42%) and higher adsorption capacity (q_e, 24.05 mg g^–1). 98.8% of dye q_e was achieved at optimal conditions of pH 8 within 30 min at 30 °C. Adsorption isotherms and kinetics investigations showed good correlation with the Freundlich adsorption isotherm model (R² > 0.9889; ΔG° = −4.71; ΔH° = −12.30; ΔS° = −0.025) as well as the pseudo-second-order kinetics model, indicating multilayered and intricate adsorption mechanisms for dye removal. The study of thermodynamic parameters confirmed the exothermic nature of the adsorption process. The adsorption–desorption study of the resulting hydrogel exhibited 64.58% dye removal efficiency even after 4 consecutive cycles of reuse. Further, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction analysis revealed the surface morphology, functional moieties, thermal behavior, and crystallinity pattern of the hydrogel. Rheological analysis demonstrated pseudoplastic flow and improved mechanical behavior for the hydrogel. The current study found that the synthesized adsorbent with a higher SI and q_e has a noticeable potential for the removal of dye pollutants from wastewater.