Narrowing band gap of ZnO codoping (Al+Mn) as a photocatalyst candidate for degraded textile dye wastewater

Photocatalyst degradation is one method to reduce industrial textile dye pollution in water. In this study, ZnO material was synthesized by codoping Al and Mn using the chemical coprecipitation method to determine the structural and optical properties of the material. This research found that the structure of ZnO after codoping Al and Mn did not change the hexagonal wurtzite phase but changed in other lattice parameters. The addition of Mn and Al codoping is reported to affect the intensity of XRD peaks, especially on the 101 lattice. The higher the scattering peak, the more angular the shift, indicating the magnitude of oxygen vacancies. The addition of Mn with 0% concentration shows the smallest lattice parameter among the other four samples. This indicates that the oxygen vacancy of the sample without Mn is more significant than that with codoping Mn. The reflectance measurement results show that the energy gap value of ZnO (Al+Mn), with a 0% Mn percentage, reaches an immense value, which is 3.290 eV. The smallest energy gap is ZnO (Al+Mn) with 4% codoping Mn which is 3.258 eV. With this consideration, ZnO (Al+Mn) with 0% Mn percentage is suitable to be applied as a Congo Red photodegradation agent, and ZnO (Al+Mn) with 4% codoping Mn is appropriate to be used as a Methylene Green photodegradation agent.