Improvement of Photocatalytic Degradation of Naphthol Green B Under Solar Light Using Aluminum Doping of Zinc Oxide Nanoparticles

The photocatalytic degradation of dyes under sunlight irradiation has received much attention not only because the attempt is aimed at decomposition of pollutants but also at finding methods of making use of solar energy. Following this line, zinc oxide nano-particles were prepared using solvent thermal method in order to decompose Naphthol Green B in presence of sunlight. Complete mineralization and decolorization of Naphthol Green B were achieved in 14 h. In order to reduce the band gap of zinc oxide and increase its photocatalytic activity in sunlight, it was doped with different concentrations of aluminum (1 %, 3 %, 5 %, and 10 %). The obtained band gap energy of the Al-doped ZnO nanoparticles was investigated as a function of Al content. Reduction of band gap energy for the heavily doped ZnO nanoparticles (10 % Al) was observed from 3.29 to 3.23 eV leading to fast transfer for electron from the excited state of dye to conduction band of ZnO. Therefore, by using the 10 % Al-doped ZnO nanoparticles, the complete mineralization and decolorization of Naphthol Green B were achieved in 6 h under sunlight. These results suggested that the heavily doped ZnO nanoparticles with aluminum has a positive effect towards photocatalytic reactions with dye under solar energy.