Photocatalytic Removal of Eriochrome Black T Dye over ZnO Nanoparticles Doped with Pr, Ce or Eu

Abstract

Wastewaters coming from textile industries produce serious problems because they contain a lot of pollutants such as organic dyes. Heterogeneous photocatalysis is a promising and efficient approach to remove dye pollutants from wastewater. ZnO is an excellent and promising photocatalytic material to decompose organic pollutants by transforming them into CO2 and H2O. In order to enhance the photocatalytic activity, ZnO could be doped with metal and non-metal ions. In this work, the doping with chemical elements belonging to the lanthanide group, such as praseodymium (Pr), cerium (Ce) and europium (Eu) is reported. ZnO nanoparticles doped with Pr or Ce or Eu were prepared by a modified precipitation method. The chemical-physical characterization data evidenced that that dopant ions were successfully incorporated into the ZnO lattice because the doped ZnO samples presented band-gap values of about 3.0 eV, lower than undoped ZnO (3.3 eV). Photocatalytic activities of the synthesized samples under UV or visible irradiation were investigated in the degradation of Eriochrome Black T (EBT) in aqueous solutions. Photocatalytic results showed that the total EBT discoloration was reached after 120 min under UV irradiation for all the photocatalysts and the complete mineralization was achieved after 180 min only for the Pr and Ce doped ZnO samples. The best photocatalytic performances in terms of EBT discoloration and mineralization have been found for Pr doped- ZnO photocatalyst, both under UV and visible light.