Synthesis of PVA-assisted MnO-CuO-ZnO-g-CN quaternary nanocomposite for the degradation of methylene blue from industrial wastewater.

The pristine phases SS1(ZnO), SS2(MnO), and SS3 (CuO) photocatalysts and mixed phases of ZnO-based nanocomposites were synthesized by the sol-gel method. Whereas SS4 (g-CN) was prepared through polymerization of urea. The synthesized photocatalysts were characterized using TGA-DTA, XRD, DRS, PL, DLS, FTIR, SEM, TEM, and HRTEM. The TGA-DTA result confirmed that the calcination temperature was attained at 400 to decompose PVA after assisting the sample. In this study, band-gap energy, crystallite sizes, charge separation, and surface properties of binary, ternary, and quaternary nanocomposites were modified more when compared with single-phase SS. This enhancement is probably due to the loading of SS2, SS3, and SS4 photocatalysts on the SS1 surface. The photocatalytic activities of all synthesized nanomaterials were explored under visible light radiation. The activity of SS1 photocatalysts is lower than those of all synthesized photocatalysts. The efficiency of the BQ (MnO-CuO-ZnO-CN nanocomposite is 2.2 times higher than that of SS1. This photocatalytic improvement might be ascribed to the cumulative effect of individual photocatalysts. The photocatalytic potential of BQ over Methylene blue (MB) from industrial wastewater was evaluated and its degradation efficiency was 98 % at 3 h. The reusing experiments of BQ nanocomposite were evaluated for four cycles and almost the same performance was observed. Besides, the possible photocatalytic mechanism was proposed. This could offer novel results in designing stable quaternary heterojunction nanocomposites through all single-phase photocatalysts.