Open Access
Visible-light-driven photocatalytic degradation of organic dyes using a TiO2 and waste-based carbon dots nanocomposite
(Elsevier, 2025-05-20) Sendão, Ricardo M.S.; Algarra González, Manuel; Lázaro-Martínez, Juan; Brandão, Ana T.S.C.; Gil Bravo, Antonio; Pereira, Carlos; Esteves da Silva, Joaquim C.G.; Pinto da Silva, Luís; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
Herein we report a visible-light-active photocatalytic nanocomposite (NC50:50) prepared from carbon dots (CDs) and TiO2 nanoparticles, which was applied to the photodegradation of organic dyes in water. The CDs incorporated corn stover, a major agricultural waste, and were prepared via hydrothermal treatment. Using a visible-light irradiation source and the dye methylene blue as a representative of the organic dyes class, we observed that a 374% enhancement of the catalytic performance was achieved by adding CDs relative to bare TiO2. This was possible due to increased visible-light absorption and better photonic efficiency. Tests using reactive species scavengers indicated that three active species (superoxide anion, hydroxyl radicals, and electrons) were responsible for the photodegradation process, differing from bare TiO2 in which only the hydroxyl radical has a relevant role. Photocatalytic degradation was also observed toward Rhodamine B, Orange II and Methyl Orange. Finally, we performed a life cycle assessment (LCA) study to assess and analyse the associated environmental impacts of NC50:50 compared with other alternatives, which revealed that NC50:50 is the alternative resulting in the least environmental impacts. In summary, NC50:50 could, under visible-light irradiation, efficiently remove different organic dyes while incorporating organic waste materials and reducing the impacts associated with their use. We expect that this study provides a base for a more environmentally sustainable design of visible-light-active photocatalysts via waste upcycling.
Open Access
Use of clays and pillared clays in the catalytic photodegradation of organic compounds in aqueous solutions
(Taylor & Francis, 2024-02-23) Cardona Rodríguez, Yaneth; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak
Conventional wastewater treatment plants do not currently remove all organic compounds, including some emerging pollutants. This has prompted several efforts to develop new methods and materials —or to improve existing ones— to remove such pollutants. The technologies studied to remove contaminants from water include photochemical processes in which the photons activate a material to produce radicals, which go on to initiate a series of reactions that result in oxidation of the pollutant. Several photocatalysts and catalyst supports have been used; these include clays and pillared interlayered clays (PILC), which have shown interesting results in the photodegradation of several organic contaminants. In this review, we describe the studies that have used both clays and PILC for the photodegradation of organic compounds in aqueous solutions. The results reported are summarized and compared, thus confirming that the findings support the use of these systems as photocatalysts and that they are successful and promising materials for the removal of several organic compounds. In this aspect, new synthesis procedures for PILC materials can be proposed from Heterostructures and MOF based on clays.

Gil Bravo, Antonio

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