Synthetization pill-like C-doped ZnO nano-photocatalyst for removing ofloxacin and methylene blue under visible light

Carbon-doped zinc oxides were synthesized with different concentrations corresponding to PVA/Zn2+ molar ratios between 5 and 15% by the hydrothermal method. The XRD and SEM results show that the obtained materials have high crystallinity and a pill-like morphology. Carbon dopant significantly decreased band gap energy (EgCZ3 = 2.77 eV), improving the optical absorption of ZnO in the visible and ultraviolet regions. Generally, the catalyst with carbon doped 1.49% (CZ3), corresponding to the molar ratio of PVA/Zn²⁺ = 15%, showed the highest photocatalytic efficiency of ofloxacin (Ofx) and methylene blue (MB) and was higher than pure ZnO. This is possibly attributed to its morphology with good uniformity and porosity; the specific surface area of SCZ3 is 26 m²/g which is 1.5 times higher than ZnO. Moreover, it is also relative to the stable and highest saturation photocurrent density of CZ3, which is ∼6.4 µA.cm⁻², 4.15 times higher than pure ZnO. In addition, trapping experiments showed that positive holes and hydroxyl radicals were the predominant active agents. Finally, COD and TOC analysis results suggested that the photodegradation progress of MB and Ofx formed organic compounds with smaller structures and proved that over 78% of MB and 66% of Ofx were converted entirely to simple inorganic substances such as CO2, H2O, etc.