Carbon-Tunable p-type ZnO Nanoparticles for Enhanced Photocatalytic Removal of Eriochrome Black T

Abstract

Zinc oxide-mediated photocatalysis is a promising alternative to TiO2 photocatalysis, especially for the purpose of removal of recalcitrant organic dye pollutants. Highly crystalline, nanoscopic carbon-doped ZnO was successfully synthesized via combined precipitation and mechanochemical approach and characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and Fourier transform infrared (FTIR) spectrometry. The obtained photocatalysts depict plate-like morphology and hexagonal wurtzite structure. The XRD, SEM, and FTIR analyses were in good agreement with EDX results. The 5wt % C-doped ZnO showed remarkable visible light-photocatalytic activity based on the degradation of Eriochrome Black T (EBT), and exhibits the best point of zero charge (pHpzc) for a favorable adsorption equilibrium. This degradation process was optimized at 97 % using response surface methodology (RSM) using a 0.1 g C-ZnO, 5.00 mg/L EBT and pH 11. The associated kinetic data fit the pseudo-first-order kinetic model. The resulting C-ZnO was a p-type with a good pH at zero-point charge that permits the substantial removal of EBT by C-doped under visible light irradiation over a wide range of initial pH.