Photocatalytic Degradation of Congo Red Dye via Multi-Walled Carbon Nanotubes Modified CuO and ZnO Nanoparticles under Visible Light Irradiation

Abstract

The photocatalytic degradation of congo red dye (CR) using nanocomposites materials of multi-walled carbon nanotubes combined with some transition metal oxide under visible light irradiation was studied. Multi-walled carbon nanotubes were prepared via chemical vapor synthesis (CVS) and loaded with some transition elements as Cu, Zn, and Cu0.1Zn0.9O nanoparticles, where the ratio of metal was kept constant in all catalysts (20% M). Various Characteristic techniques were adopted such as X-Ray Diffraction (XRD), Nitrogen adsorption-desorption, Transmission Electron Microscope (TEM), Fourier Transform Infra-Red (FT-IR), Ultra Violet reflectance analysis (UV), Scanning Electron Microscope (SEM), Energy dispersive X-ray Spectroscopy (EDX), Photoluminescence (PL) Spectroscopy and Raman spectroscopy. The results proved that the mother carbon nanotubes have a high surface area and total pore volume and are found to be 247m2/g and 0.569 cm3/g, respectively, and its surface area decreased upon loading the metal nanoparticles. Pore size distribution curve (PSD) exhibited a wide mesopore centered at 30 nm. TEM results revealed that Cu and Zn metals are randomly distributed and located at the nanotube's surface and the tips of the tube via the tip-growth mechanism. It is obviously seen that the Zn/CNTs have a homogenously uniform diameter as compared to the neat CNTs. The nanocomposites' photodegradation% rank was Zn/CNT > Cu/CNT > Cu-Zn/CNT, which related mainly to the chemical composition of Zn/CNT composite. Zn/CNT composite showed the highest degradation efficiency among the prepared composites, which achieved 97.7% after 70 minutes under visible light irradiation. The mechanism of the photocatalytic degradation of congo red dye under visible light irradiation was discussed.