Fabrication of visible-light-active ZnCr mixed metal oxide/fly ash for photocatalytic activity toward pharmaceutical waste ciprofloxacin

• Published in: Journal of industrial and engineering chemistry (Seoul, Korea) 2022, 108(0), , pp.263-273
• Main Authors: Chuaicham, Chitiphon, Inoue, Takumi, Balakumar, Vellaichamy, Tian, Quanzhi, Sasaki, Keiko
• Format: Article
• Language: English
• Subjects: Ciprofloxacin degradation; Fly ash; Photocatalyst; ZnCr mixed metal oxides; 화학공학
• ISSN: 1226-086X; 1876-794X
• DOI: 10.1016/j.jiec.2022.01.006

[Display omitted] •FA acted as the template for ZnCr-MMO to avoid the agglomeration of ZnCr-MMO.•The ZnCr-MMO-FA heterojunction improved the electron-hole pairs separation.•ZnCr-MMO/FA photocatalyst has excellent CIP degradation under visible light irradiation.•ZnCr-MMO/FA photocatalyst has excellent reusability and stability. Visible active photocatalysts have attracted interest as a potentially efficient and sustainable approach for pollutant degradation treatment. In this work, ZnCr mixed metal oxide/fly ash (ZnCr-MMO/FA) composites were prepared using fly ash (FA) from China coal mining power plants to improve photocatalytic performance. The formation of the ZnCr-MMO/FA composites was proved by XRD results which showed the two-phases combination of FA and MMO. Also, the presence of FA in the ZnCr-MMO/FA composite provided a good arrangement of small particles of ZnCr-MMO on the surface of FA and higher light absorption ability with a lower energy bandgap compared with the pure ZnCr-MMO. The photocatalytic performance of the prepared ZnCr-MMO and ZnCr-MMO/FA composites in different FA contents was evaluated by degradation of ciprofloxacin (CIP), which is an antibiotic and often found in pharmaceutical wastes, under visible light irradiation. Clearly, the ZnCr-MMO/FA composites showed higher photocatalytic decomposition of CIP than pristine ZnCr-MMO, and the highest degradation performance for CIP was obtained from the ZnCr-MMO/FA sample with 0.5 mg FA, which has a reaction rate constant approximately four times greater than that of pure ZnCr-MMO. The improved CIP degradation activity of the ZnCr-MMO/FA composite might not only be due to the good arrangement of ZnCr-MMO particles on the FA surface but also high separation and less recombination of photogenerated electrons-holes pairs, proven by the photoluminescence spectra, photocurrent density, and electrochemical impedance spectroscopy results. The lower recombination of the charge carriers of the ZnCr-MMO/FA composite might be caused by the heterojunction between the ZnCr-MMO as a main photocatalyst and FA. Thus, the proposed ZnCr-MMO/FA composite can be used as an effective photocatalyst for wastewater treatment, including the decomposition of organic pollutants, such as discarded pharmaceuticals.