Efficient catalytic removal of organic pollutant for wastewater treatment using a graphitic carbon nitride/guar-gum/ZnO nanocomposite

Abstract

Water contamination from dyes has become an environmental concern, which calls for the development of effective and long-lasting adsorbents. In this work, g-C₃N₄/GG/ZnO nanocomposite was synthesized and its adsorption potential toward Congo red (CR) dye was assessed. Different analytical instruments such as FTIR, FESEM, XRD, HRTEM, BET, UV–Visible-DRS and XPS were used to characterize the modified nanocomposite. BET surface area analysis revealed a significant rise in the specific surface area (43.302 m²/g) of the nanocomposite compared to its individual components, which contributed to enhanced dye adsorption. UV-DRS analysis of g-C₃N₄/GG/ZnO nanocomposite showed a band gap energy of 2.7 eV, confirming the material's optical properties suitable for visible light absorption and potential photocatalytic applications. This study modified g-C₃N₄ with ZnO and GG to increase the removal efficiency of g-C₃N₄ (85.53 ± 0.198 %). The maximum CR removal of 97.76 ± 0.08 % was achieved by g-C₃N₄/GG/ZnO nanocomposite using an optimum dose of 2.4 g/L and 120 min contact time. The Langmuir model was identified as the most effective isotherm model, demonstrating the maximum adsorption capability of 52.6 mg/g. The pseudo-second-order model produced the best correlation with the experimental findings. The material was also evaluated for its adsorptive and photocatalytic dye removal efficiency under a low dosage and short reaction time, achieving a 94.89 % dye removal. Reusability studies revealed that the nanocomposite maintained effective adsorption over three cycles, although a gradual decrease in performance was observed. These results demonstrate that the g-C₃N₄/GG/ZnO nanocomposite is a highly effective adsorbent for dye removal, making it a promising candidate for sustainable wastewater treatment applications.