Evaluation of the Photocatalytic Activity of Chitosan-G-C3N4 Composite for Methylene Blue Degradation

Abstract

The growing concern over environmental pollution has driven research into effective, sustainable solutions, particularly in the field of water treatment. This study investigated the photocatalytic activity of a chitosan- g-C3N4 composite, aimed at degrading methylene blue (MB), a prevalent organic dye and pollutant in wastewater. Chitosan (CS) was synthesized from shrimp shells using a series of chemical processes, including demineralization, deproteination, and deacetylation, while graphitic carbon nitride (g-C3N4) was synthesized via thermal treatment of urea. The composite was prepared by mixing varying ratios of CS and g-C3N4, and its photocatalytic efficiency was tested against MB solutions of different concentrations under visible daylight including MB solution, chitosan and MB solution, g-C3N4 and MB solution as controls. Results showed that the chitosan-g-C3N4 composite effectively degraded methylene blue, and the degradation efficiency depends on the composite ratio and MB concentration.  The highest rate constant of 10.6 × 10⁻³ min⁻¹ was obtained with 2 ppm MB solution using 1:1 ratio of CS to g-C3N4, while a 1:2 ratio demonstrated optimal degradation rates for both 4 ppm and 5 ppm MB solutions, achieving a rate constant of 6.5×10⁻³ min⁻¹. The 1:2 ratio of chitosan to g-C3N4 consistently provided one of the most efficient degradation rates across concentrations, especially at 2 ppm. These findings underscore the potential of g-C3N4 and its composites with chitosan, particularly those with higher g-C3N4 content, to significantly improve photocatalytic degradation of MB compared to chitosan alone. The optimum performance was achieved at lower MB concentrations (2 ppm), with the 1:1 and 1:2 ratios being particularly effective. The enhanced photocatalytic activity is attributed to the synergistic interaction between chitosan and g-C3N4, where chitosan’s adsorption properties complement the photocatalytic abilities of g-C3N4 by facilitating the separation of photogenerated electron-hole pairs and reducing recombination. This study highlighted the potential of using chitosan- g-C3N4 composites for wastewater treatment applications. By utilizing waste-derived chitosan, this approach not only enhances photocatalytic processes but also contributes to sustainable material development. The findings suggest that the composite can serve as an eco-friendly, cost effective, and efficient photocatalyst for degrading organic pollutants in wastewater, making it a promising and scalable solution for addressing water contamination challenges.

Keywords: Photocatalysis, Chitosan, g-C3N4, Methylene blue, Wastewater treatment