Synthesis, characterization and photocatalytic activity of alginate based hybrid material for efficient degradation of organic pollutants under UV light and sunlight irradiation

This study reports the development of alginate based hybrid material (Alg/CuO-gC₃N₄) with copper oxide (CuO) and graphitic carbon nitride (gC₃N₄). The Alg/CuO-gC₃N₄ hydrogel bead was prepared by two step process is as follows: formation of CuO-gC₃N₄ by co-precipitation method and incorporation of CuO-gC₃N₄ in the calcium alginate (Alg) by ionotropic gelation method. The structural and morphological features of the Alg/CuO-gC₃N₄ was characterized using different techniques namely Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), UV Diffuse Reflectance spectroscopy (UV-DRS) and Scanning electron microscopy (SEM). The photocatalytic activity of the Alg/CuO-gC₃N₄ was extensively evaluated by degrading methylene blue (MB) under UV–vis and sunlight irradiation. The influence of various parameters like pollutant type, initial dye concentration, catalyst dosage, effect of pH, light intensity and reusability was investigated. The Alg/CuO-gC₃N₄ achieved a maximum degradation efficiency of 86.26 % and 85.15 % for MB at a dye concentration of 1 × 10−5 M under UV–vis and sunlight irradiation respectively, within 60 min using 0.3 wt% of catalyst dosage. The Alg/CuO-gC₃N₄ exhibited excellent stability and reusability over multiple cycles. Additionally, the incorporation of CuO-gC₃N₄ in alginate facilitates in reducing the bandgap (2.54 to 2.28 eV) for efficient charge separation, further enhancing the overall photocatalytic activity.