Preparation of sillenite-type Bi12MnO20 with enhanced photocatalytic activity for removal of organic pollutants via superoxide radicals
(1. School of Metallurgy and Environment, Central South University, Changsha 410083, China;
2. Hunan Rare Earth Metal Material Research Institute, Changsha 410083, China)
2. Hunan Rare Earth Metal Material Research Institute, Changsha 410083, China)
Abstract: Sillenite-type photocatalytic material Bi12MnO20 with photo-absorptive ability in the spectrum range of 200-2200 nm was prepared by wet ball milling followed by calcination. The crystal structure of Bi12MnO20 can be viewed as the metastable cubic γ-Bi2O3 with the incorporation of Mn4+ into tetrahedral sites. The entry of Mn4+ into γ-Bi2O3 crystal creates a sub-bandgap of 1.25 eV appearing in the energy band structure of Bi12MnO20. The Bi12MnO20 photocatalyst can accelerate the transformation of O2 in solution into superoxide radicals (·O2-), thereby improving charge separation and transfer during photocatalytic degradation. As a result, the degradation rate of over 95% to the malachite green (MG) with a concentration of 10 mg/L in the pH=8 solution by Bi12MnO20 is achieved under simulated sunlight. After four cycles of photo-degradation, the removal rate of MG by Bi12MnO20 remains at 74.9%.
Key words: Bi12MnO20; photocatalysis; degradation; energy band; superoxide radical