Aurivillius Perovskite-Rhodamine B as Generic Type-II Heterojunction for Collective Photocatalytic Degradation of Multiple POPs

The photocatalytic activity for wastewater treatment is mainly restricted due to insufficient solar absorption and intense exciton recombination. This article demonstrates an in situ synergistic combination of a photocatalyst and a dye as a type II heterojunction for the collective degradation of water-soluble dyes, pharmaceuticals, and phenolic pollutants. This combination helps to increase visible-light absorption and decrease charge carrier recombination. For this, a series of visible-light-active two-layer Aurivillius perovskites, Bi2.5A0.5Nb1.75Fe0.25O9 (A = Ca, Sr, Ba), was synthesized via the solid-state reaction method. The presence of Fe-doping-induced energy levels is responsible for enhanced visible-light absorption. The semiconductors can efficiently photodegrade bisphenol (BPA), carbamazepine (CBZ), tetracycline (TC), and 4-chlorophenol (4-CP) individually as well as from a mixture by the semiconductors in the presence of RhB. The photocatalytic degradation is driven by a synergistic effect of RhB adsorbed on the surface of the photocatalyst. The RhB-adsorbed semiconductor acts as a type-II heterojunction, which not only enhances light absorption by the photosensitization effect but also improves charge separation and reactive oxygen species (ROS) generation. The strategy will be useful as a sustainable alternative for the degradation of multiple pollutants in wastewater by a unique and straightforward photoexcitation and sensitization process.