Enhanced degradation of crystal violet dye under solar light by zirconium phosphate-decorated graphitic carbon nitride

Solar light-induced aqueous crystal violet (CV) dye degradation was carried out on α-zirconium phosphate/graphitic carbon nitride (α-ZrP/g-C₃N₄) nanocomposite. α-ZrP was synthesized by direct precipitation of zirconium oxychloride with phosphoric acid. g-C₃N₄ was prepared by thermal decomposition of melamine. α-ZrP/g-C₃N₄ nanocomposite was synthesized by the direct precipitation of zirconium phosphate on the surface of g-C₃N₄.

Powder X-ray diffraction pattern confirmed the formation of pure α-ZrP, g-C₃N₄, and α-ZrP/g-C₃N₄ nanocomposites with crystallite sizes of 51.3 nm, 8.9 nm, and 46.4 nm, respectively. SEM images of α-ZrP showed plate-like morphology and g-C₃N₄ showed a layered structure with buckled and backfolded edges. XPS and EDX spectrum of the α-ZrP/g-C₃N₄ nanocomposite shows the presence of Zr, P, N, C, and O elements. The optical absorption wavelength/band gap of the α-ZrP, g-C₃N₄, and α-ZrP/g-C₃N₄ nanocomposites were 394.7 nm/3.33 eV, 494.3 nm/2.66 eV, and 457.5 nm/2.85 eV, respectively. The degradation efficiency toward CV dye was found in the order of α-ZrP < g-C₃N₄ < α-ZrP/g-C₃N₄ nanocomposite. The degradation efficiency increases with an increase in time, and the pseudo-first-order kinetics model was fitted well. The rate constant of the α-ZrP/g-C₃N₄ nanocomposite was found four times higher than that of g-C₃N₄ and ten times of the α-ZrP. The photocatalytic degradation of CV dye under solar light occurred via oxidation by hydroxyl radical and was maximum at pH 6. The photocatalytic degradation efficiency decreases in the presence of anions. α-ZrP/g-C₃N₄ nanocomposite is easy to synthesize, low-cost, and has high degradation efficiency, making it a promising photocatalyst to clean water containing CV dye under solar light.