<i>Vitis vinifera</i> L. Filled Chitosan Composite Microspheres for Adsorption of Toxic Methylene Blue Dye from Aqueous Solutions: Isotherm, Kinetic, Thermodynamic Studies and Error Analysis

This study produced natural, sustainable, and efficient composite microbeads by incorporating Vitis vinifera L. (VF) biomass, regarded as a zero-waste product, and is transformed into chitosan (CS) biopolymer at various ratios, intended for use as an effective adsorbent material for the removal of dye (MB) from aquatic environments. The chitosan/biomass composite (CS-VF) was analyzed using FT-IR, SEM, EDS, XRD, and pHpzc analyses. The dosage (0.01 to 0.30 g), pH (2 to 12), and duration (0 to 150 min) of CS-VF-30 composite microbeads were examined, and the optimal conditions for the adsorption process were established. The impact of salt content on the adsorption process was investigated using monovalent NaCl and divalent CaCl2 salts. The adsorption of MB by CS-VF-30 composite microbeads was accurately characterized by isotherms and adsorption kinetics, validating the Langmuir and pseudo-second-order kinetic models. The qm value was ascertained to be 45.79 mg/g at 298 K by using the Langmuir isotherm model. This results from the electrostatic interaction, H-bonding, and π–π stacking interactions of the MB dye with the CS-VF-30 composite microbeads. Conversely, reusability experiments established that the composite microbeads can be utilized multiple times. This research demonstrates that CS-VF-30 composite microbeads serve as an effective bioadsorbent for the treatment of high-strength dye wastewater. Furthermore, the prepared composite microspheres were found to be highly effective in different water samples and could be reused repeatedly. The results demonstrate a sustainable and eco-friendly method for producing chitosan/biomass composite adsorbents for the extraction of cationic dyes from polluted water.