Rapid Degradation of Organic Dyes by Nanostructured Gd<sub>2</sub>O<sub>3</sub> Microspheres
Pollution of freshwater by synthetic organic dyes is a major concern due to their high toxicity and mutagenicity. In this study, the degradation of Congo red (CR) and malachite green (MG) dyes was investigated using nanostructured Gd<sub>2</sub>O<sub>3</sub>. It was prepared...
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
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| Series: | Applied Nano |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2673-3501/6/1/1 |
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| Summary: | Pollution of freshwater by synthetic organic dyes is a major concern due to their high toxicity and mutagenicity. In this study, the degradation of Congo red (CR) and malachite green (MG) dyes was investigated using nanostructured Gd<sub>2</sub>O<sub>3</sub>. It was prepared using the coprecipitation method, using gadolinium nitrate and concentrated formic acid, with subsequent calcination at 600 °C. Its morphology corresponds to hollow porous microspheres with a size between 0.5 and 7.5 μm. The optical bandgap energy was determined by using the Tauc method, giving 4.8 eV. The degradation of the dyes was evaluated by UV-vis spectroscopy, which revealed that dissociative adsorption (in the dark) played a key role. It is explained by the cleavage and fragmentation of the organic molecules by hydroxyl radicals (<sup>•</sup>OH), superoxide radicals (<sup>•</sup><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mrow><mi mathvariant="normal">O</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msubsup></mrow></semantics></math></inline-formula>) and other reactive oxygen species (ROS) produced on the surface of Gd<sub>2</sub>O<sub>3</sub>. For CR, the degradation percentage was ~56%, through dissociative adsorption, while UV light photocatalysis increased it to ~65%. For MG, these values were ~78% and ~91%, respectively. The difference in degradation percentages is explained in terms of the isoelectric point of solid (IEPS) of Gd<sub>2</sub>O<sub>3</sub> and the electrical charge of the dyes. FTIR and XPS spectra provided evidence of the role of ROS in dye degradation. |
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| ISSN: | 2673-3501 |