Publication: Synthesis of carbon quantum dots modified g-c3n4/bioclxbr1-x heterojunctions for photocatalytic degradation of antibiotic and bacteria deactivation
| datacite.subject.fos | oecd::Engineering and technology::Chemical engineering | |
| dc.contributor.author | Mohamed Hussein Abdurahman Mohamed | |
| dc.date.accessioned | 2025-05-13T02:31:02Z | |
| dc.date.available | 2025-05-13T02:31:02Z | |
| dc.date.issued | 2023-01-01 | |
| dc.description.abstract | The g-C3N4/CQD combined with BiOClxBr1-x was successfully synthesized by calcination and hydrothermal method. The FT-IR analysis detected the peak at 807 cm-1 which is the distinctive absorption peak of the triazine ring, and the various peak bands at 1240-1630 cm-1 which are the C=N and C-N rings of heterocyclic stretching vibration. The XRD diffractogram displayed the strong diffraction peak at 27.08° which could be assigned to the (002) interplanar, and the other weak peak at 13.17° corresponds to the (011), which is like the in-plane structure of tri-triazine units. The bandgap of the photocatalysts was found to be slightly reduced at presence of the Br content. The photocatalyst composite has a high specific surface area (26.91 m2/g) compared with the pure g-C3N4 (15.46 m2/g), reflecting a high degree of the formation of the composite during the preparation procedure. The XPS analysis indicated that the N: C ratio of the g-C3N4/CQD/BiOCl0.75Br0.25 (1.362) was lower than that of the g-C3N4/CQD (2.15), suggesting the introduction of nitrogen vacancies. Moreover, due to the presence of Bi-O in g-C3N4/CQD/BiOCl0.75Br0.25, the O: C ratio of g-C3N4/CQD (0.09) increased to 0.27. The atomic ratio of Cl: Br theoretically was 3:1. However, experimentally, it was found to be 2.4:1, which demonstrates the presence of Cl and Br in the composite material. The photocatalytic activity of the g- C3N4/CQD/BiOClxBr1-x was investigated in the photocatalytic degradation of tetracycline (TC), and E. coli under visible light irradiation. Both experimental and characterizations confirmed that the synergistic effects of 1wt% CQDs and g C3N4/BiOCl0.75Br0.25 markedly improved the interfacial charge transfer efficiency and light-harvesting capacity of the composites. The optimum reaction conditions were 10 mg/L (TC concentration), pH 5.8, and 100 mg of catalyst dosage. Under these conditions, the degradation rate of tetracycline over g-C3N4/CQD/BiOCl0.75Br0.25 was 83.4% after 30 min and demonstrated favourable stability with near-initial capacity under visible light irradiation. The effects of various experimental parameters on photocatalytic performance, including the amount of carbon quantum dots (0.5-2wt%), initial concentrations of tetracycline of 5-40 mg/L, catalyst dosages of 50-250 mg/L, solution pH of 3-10, organic and inorganic contaminants such as humic acid, NO3 -, SO4 2-, PO2 3- and CO3 2- were further studied for actual use evaluation. A possible photocatalytic reaction mechanism was proposed based on the analysis of the adsorption, efficient utilization of visible light, and charge transfer. Mass spectrometry was used to analyse the degradation by-products and proposed possible degradation routes. The QSAR analysis indicated that the toxicity of most intermediates was lower than TC. Besides, the g-C3N4/CQD/BiOCl0.75Br0.25 manifested a better photocatalytic disinfection performance towards E. coli than pristine g-C3N4, g-C3N4/CQD, g- C3N4/CQD/BiOCl, respectively. Emphasis was placed on the effect of the solution pH and the presence of organic and inorganic substituents on the disinfection performance. The synergistic effects of enhanced visible light absorption ability, exposed active sites, and improved photogenerated charge separation were responsible for the excellent photocatalytic disinfection activity. The effect of radical scavengers confirmed the major role of h+ and O2 •-. The gradually damaged cell membrane for E. coli was imaged to decipher the antibacterial behaviour. The TOC level in the suspension decreased dramatically from 32.1 mg/L to 4.1 mg/L, whereas the K+ leakage concentration reached its maximum of 2.23 mg/L after 180 minutes of visible light irradiation. This study provides a strategy for fabricating solar-light-driven photocatalyst with excellent photocatalytic activity, furnishing a new insight for interface charge transfer | |
| dc.identifier.uri | https://erepo.usm.my/handle/123456789/21590 | |
| dc.language.iso | en | |
| dc.title | Synthesis of carbon quantum dots modified g-c3n4/bioclxbr1-x heterojunctions for photocatalytic degradation of antibiotic and bacteria deactivation | |
| dc.type | Resource Types::text::thesis::doctoral thesis | |
| dspace.entity.type | Publication | |
| oairecerif.author.affiliation | Universiti Sains Malaysia |