Visible-light-driven photocatalytic degradation of different organic pollutants using Cu doped ZnO-MWCNT nanocomposites

Abstract

Photocatalytic degradation of organic pollutants has been established as one of the most effective and affordable technique to solve the environmental contamination issues. The present work was focused on the development of Cu doped ZnO-MWCNT nanocomposites designated for photodegradation of three water organic pollutants namely rhodamine (RhB) dye, phenol and oxytetracycline (OTC) antibiotic. The nanocomposite samples, with MWCNTs: ZnOCu weight ratios of 1:1, 1:3 and 1:5 were prepared and characterized using modern techniques. XRD revealed the presence of both MWCNT and ZnO crystalline phases in composites. The specific bands of MWCNT and ZnO composite components were highlighted by FT-IR. EPR and XPS spectroscopy showed the presence of Cu2+ ions inside the ZnO lattice. SEM and TEM images provided evidence of the attaching and distribution along the nanotubes of Cu doped ZnO nanoparticles with spherical form and diameter around 20 nm. The energy band gap of nanocomposites decreased with the increase of MWCNT amount. The PL emissions gradually quenched by increasing MWCNT content due to electron-hole recombination delays, which favors photocatalytic activity. Evaluation of nanocomposites as photocatalysts for degradation of the three types of pollutant solutions under visible irradiation demonstrated that all samples possessed photocatalytic activity. The best photocatalytic performance was acquired using MWCNT-ZnOCu-3 sample with degradation rates of 76%, 55% and 91% for RhB, OTC and phenol solutions, respectively. The mechanism of photocatalytic activity was elucidated based on the scavenger experiments, reactive oxygen species involved in this process and in correlation with energy bands alignment and gap states. The degree of mineralization of pollutant solutions obtained via total organic carbon analysis was evaluated.