Polymeric Nanocomposite Adsorbent of Cross-linked Chitosan-adipic Acid and SnO₂ Nanoparticles for Adsorption of Methyl Orange Dye: Isotherms, Kinetics, and Response Surface Methodology

In the present work, a polymeric nanocomposite adsorbent of cross-linked chitosan-adipic acid and SnO₂ nanoparticles (CS-ADP/SnO₂) was created for the adsorption of methyl orange (MO) dye from water. Response surface methodology (RSM) was used to examine how three factors affected the adsorption of the dye MO: time C (10–40 min), pH (4–10), and CS-ADP/SnO₂ dosage (0.02–0.08 g/L). The CS-ADP/SnO₂ nanocomposite has a BET surface area of 28.64 m²/g, a total pore volume of 0.0271 cm³/g, and a mean pore diameter of 3.79 nm. The several XRD diffraction peaks and average crystallite size of 31.33 nm of the CS-ADP/SnO₂ nanocomposite indicate that it primarily possesses polycrystalline properties. The MO adsorption by CS-ADP/SnO₂ could be well described by the isotherm model, which was validated by the adsorption kinetics and Freundlich and pseudo-first-order kinetic models. The best circumstances for maximum MO elimination (80.54%) were found to be a pH of 4, a CS-ADP/SnO₂ dosage of 0.055 g/L, and a contact period of 40 min, according to the results of the BBD model. At 25 ^oC, the maximal adsorption capacity of the CS-ADP/SnO₂ nanocomposite toward the MO dye was 344.91 mg/g. The Yoshida H-bonding, electrostatic interaction, hydrogen bonding, and n-π stacking interaction, were postulated as the mechanisms for MO dye adsorption onto CS-ADP/SnO₂ nanocomposite. In summary, this research suggests that the composite has the ability to effectively remove organic dyes from water systems, making it a promising new adsorbent.