Novel biocomposite of ionic cross-linked chitosan and acid-treated potato (Solanum tuberosum L.) peel agro-waste for highly efficient removal of methylene blue dye from water

In this study, a biocomposite material (CS-OXA/PP-SA) composed of ionic crosslinked chitosan-oxalate (CS-OXA) and chemically modified lignocellulosic biomass (potato (Solanum tuberosum L.) peel-H₂SO₄ acid, PP-SA) was synthesized to serve as a bioadsorbent for removing methylene blue (MB) dye from aquatic systems. The research utilized response surface methodology (RSM) to evaluate the effects of three variables: CS-OXA/PP-SA dosage (0.02 to 0.08 g), pH (4 to 10), and duration (10 to 40 min) on MB dye adsorption. The investigation of the BET surface area of the CS-OXA/PP-SA composite revealed that it had a total pore volume of 0.0261 cm³/g, a surface area of 8.26 m²/g, and an average pore diameter of 12.67 nm. The XRD pattern shows a peak at 20.5°, confirming the crystalline CS within the composite, and another at 35°, attributed to the (004) crystal plane of cellulose in PP-SA. These peaks verify the successful integration of CS and PP-SA into the biocomposite. The optimal conditions identified include an adsorbent dose of 0.055 g, a solution pH of approximately 10, and a contact duration of 29.8 min. The optimal MB dye removal efficiency achieved under these parameters was 90.9 %. The results demonstrated that the adsorption of MB onto CS-OXA/PP-SA aligns closely with the pseudo-first-order kinetic model, suggesting a physisorption-dominated process. Additionally, the adsorption isotherm fitting to the Freundlich model highlights the heterogeneous nature of the adsorbent surface and the multilayer adsorption mode. The CS-OXA/PP-SA composite demonstrated a maximum adsorption capacity of 314.92 mg/g for MB dye. The adsorption mechanism is attributed to electrostatic interactions, hydrogen bonding, and n-π stacking interactions. The findings suggest that CS-OXA/PP-SA is a highly effective bioadsorbent for treating dye-contaminated wastewater. This study introduces a sustainable and eco-friendly approach to developing efficient adsorbents for the removal of cationic dyes from contaminated water. The biocomposite demonstrates high adsorption capacity, cost-effective production, and renewable sources, offering an innovative and practical solution for wastewater treatment while adhering to green chemistry principles.