Anthraquinone and its derivatives as a recyclable photocatalyst for Efficient Photocatalytic Degradation of Rhodamine B in Water under visible light

Abstract

Abstract This study presents findings that suggest it is possible to fine-tune and enhance the optical properties of anthraquinone (AQ) and its photocatalytic performance in the degradation of rhodamine B (RhB) at the molecular level through varying its keleton substituents. Specifically, the electron-withdrawing substituent demonstrates a more pronounced improvement effect compared to the electron-donating substituent. Among them, 2-carboxyanthraquinone (AQ-COOH) demonstrated the most exceptional photocatalytic activity, affording 99.9% degradation rate under visible light irradiation for 30 min. It is noteworthy that a hydrochloric acid solution with a concentration of 0.5 mmol·L− 1 has a considerable promoting impact on the photodegradation of RhB catalyzed by AQ-COOH, and that the total degradation of RhB can be accomplished in 15 min. In addition, AQ-COOH also has good applicability for the degradation of tetracycline, methylene blue, and methyl orange. As a recyclable solid catalyst, the catalytic activity of AQ-COOH remained mostly unchanged after being used five times. Additionally, AQ-COOH did not undergo degradation when exposed to visible light, indicating its excellent stability in the process of catalyzing RhB degradation. According to quenching experiments and EPR spectrum characterizations, the photo-generated active species oxygen vacancies (h+), photogenerated electrons (e−), superoxide free radicals (O2•−), singlet oxygen (1O2) and hydroxyl radical (•OH) are involved in the hypothesized photo-catalytic degradation mechanism.