Experimental and Theorical of Adsorption of Methylene Blue by Hydrogels based by Copolymer (Styrene-Co-Maleic anhydride) Cross-linked with PEG

Adsorptive materials must fulfill various criteria, such as application versatility, ease of synthesis, reusability, environmental sustainability, and cost-effectiveness in production. This study focused on synthesizing a dual-polymeric material composed of biocompatible copolymer (styrene-co-maleic anhydride) (SMA) cross-linked with poly (ethylene glycol) (PEG). The obtained copolymer SMA and hydrogels were characterized with several analytical techniques as FTIR, TGA, and UV spectroscopy. The study of methylene blue adsorption included both equilibrium adsorption isotherms and kinetics. The adsorption performance toward methylene blue was investigated through equilibrium isotherms and kinetic studies. The Langmuir isotherm model provided the best fit to the equilibrium data, indicating monolayer adsorption behavior. Among the prepared materials, SMA–PEG1 (based on PEG with a molecular weight of 200 g•mol⁻¹) exhibited the highest maximum adsorption capacity compared to SMA–PEG2 (PEG 6000 g•mol⁻¹) and SMA–PEG3 (PEG 8000 g•mol⁻¹). Furthermore, the geometries of the SMA–PEG hydrogels were optimized using Density Functional Theory (DFT) at the Becke-3-Lee-Yang-Parr hybrid functional (B3LYP/DND )level of theory, and their electronic properties were analyzed through Natural Bond Orbital (NBO) analysis to better understand their adsorption mechanisms.