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Rapid Degradation of Organic Dyes by Nanostructured Gd₂O₃ Microspheres

by Carlos R. Michel

Appl. Nano 2025, 6(1), 1; https://doi.org/10.3390/applnano6010001 - 13 Jan 2025

Cited by 1 | Viewed by 2417

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 Gd₂O₃. 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 (^•OH), superoxide radicals (^•

O_{2}^{-}

) and other reactive oxygen species (ROS) produced on the surface of Gd₂O₃. 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 Gd₂O₃ and the electrical charge of the dyes. FTIR and XPS spectra provided evidence of the role of ROS in dye degradation. Full article

(This article belongs to the Special Issue Nanoscale Solutions: Transformative Applications of Functionalized Nanomaterials in Environmental Remediation)

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8 pages, 9434 KB

Open AccessArticle

Preparation and Characterization of Nanostructured Hollow MgO Spheres

by Jishuo Han, Guohua Li and Lin Yuan

Materials 2019, 12(3), 537; https://doi.org/10.3390/ma12030537 - 11 Feb 2019

Cited by 2 | Viewed by 4683

Abstract

Nanostructured hollow MgO microspheres were prepared by the template method. First, D-Anhydrous glucose was polymerized by the hydrothermal method to form a template. Second, a colorless solution was obtained by mixing magnesite with hydrochloric acid in a 1:2 proportion and heating in an 80 °C water bath for 2 h. Finally, the template from the first step was placed in the colorless solution, and the resulting precipitate was calcined at 550 °C for 2 h. The phase composition and microstructure of the calcined samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results indicated that the main crystal is periclase. The SEM results indicates that the template carbon microsphere surface is smooth, and the its size is uniform and concentrated in the range of 100–200 nm. The diameters of the samples range from 60 to 90 nm, which is smaller than the size of the carbon microsphere. The TEM results indicates that the sample is hollow with a shell thickness of about 6–10 nm. The specific surface area of the calcined hollow sphere is 59.5 m²·g⁻¹. Full article

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