Investigation of the Adsorptive Performance of Chitosan/Halloysite Nanotube/Green Mold Biocomposite Beads for Methylene Blue Removal

Abstract

In this study, chitosan-based composite hydrogel beads were successfully synthesized using halloysite nanotubes and green mold derived from grapefruit (Citrus paradisi) peel. The efficiency of these novel composites in removing methylene blue (MB) from aqueous solutions was evaluated under batch conditions. Comprehensive characterization of the hydrogel beads was carried out using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). The effects of various operational parameters including contact time, pH, initial dye concentration, adsorbent dosage, and temperature on the adsorption performance were systematically investigated. Optimal adsorption conditions were identified as 2.5 g/L adsorbent dosage, 100 mg/L initial dye concentration, pH 7, contact time of 120 minutes, stirring speed of 200 rpm, and a temperature of 25 °C. Adsorption isotherm studies revealed that the Langmuir model best fit the experimental data, suggesting monolayer adsorption with a maximum adsorption capacity of 67.11 mg/g. Kinetic modeling demonstrated that the adsorption process followed the pseudo-second-order model. The primary adsorption mechanisms between MB and the composite are reduction, electrostatic interaction, and chemisorption. Furthermore, thermodynamic analysis confirmed that the adsorption process was spontaneous and exothermic in nature. These findings highlight the potential of the synthesized biocomposite hydrogel beads as an effective and sustainable adsorbent for dye removal from wastewater.