RESUMO
Tribocatalysis is an emerging advanced oxidation process that utilizes the triboelectric effect, based on friction between dissimilar materials to produce charges that can initiate various catalytic reactions. In this study, pure and rare-earth-modified ZnO powders (La2O3, Eu2O3, 2 mol %) were demonstrated as efficient tribocatalysts for the removal of the tetracycline antibiotic doxycycline (DC). While the pure ZnO samples achieved 49% DC removal within 24 h at a stirring rate of 100 rpm, the addition of Eu2O3 increased the removal efficiency to 67%, and La2O3-modified ZnO powder exhibited the highest removal efficiency, reaching 80% at the same stirring rate. Additionally, increasing the stirring rate to 300 and 500 rpm led to 100% DC removal in the ZnO/La case within 18 h, with the pronounced effect of the stirring rate confirming the tribocatalytic effect. All tribocatalysts exhibited excellent recycling properties, with less than a 3% loss of activity over three cycles. Furthermore, a scavenger assay confirmed the importance of superoxide radical generation for the overall reaction rate. The results of this investigation indicate that the rare-earth-modified ZnO tribocatalysts can effectively utilize mechanical energy to decompose pollutants in contaminated water.
Assuntos
Antibacterianos , Metais Terras Raras , Óxido de Zinco , Óxido de Zinco/química , Antibacterianos/química , Metais Terras Raras/química , Catálise , Tetraciclina/química , Oxirredução , Poluentes Químicos da Água/químicaRESUMO
In this study, pure TiO2 gels were synthesized by applying the sol-gel method, using Ti(IV) butoxide with the addition of two different solvents, namely ethylene glycol (EG) and isopropanol (isop), with only air moisture present. It was established using XRD that the gel prepared with the addition of EG was amorphous even at 400 °C, while the other gel was amorphous up to 300 °C. It was found that TiO2 (anatase) had a dominant crystalline phase during heating to 600 °C, while at 700 °C, TiO2 (rutile) appeared. The as-obtained powdered materials were annealed at 500 °C and subsequently underwent photocatalytic tests with paracetamol. Additionally, the TiO2 samples were modified with Ag+ co-catalysts (10-2 M), using photofixation by UV illumination. The photocatalytic activity of the Ag-modified powders was also tested in the photodegradation of a commonly used paracetamol in aqueous solution under UV light illumination. The obtained data exhibited that the annealed samples had better photocatalytic efficiency and decomposed paracetamol faster in comparison to the non-annealed sol-gel powders. The highest degradation efficiency was observed for the TBT/isop/Ag material, with degradation efficiencies average values of 65.59% and 75.61% paracetamol achieved after the third cycle of photocatalytic treatment. The co-catalytically modified powders had higher photocatalytic efficiency in comparison to the pure nanosized powders. Moreover, the sol-gel powders of TBT/EG, TBT/EG/Ag (10-2 M), TBT/isop, and TBT/isop/Ag (10-2 M) demonstrated the ability to retain their photocatalytic activity even after three cycles of use, suggesting that they could find practical use in the treatment of pharmaceutical wastewater. The observed photocatalytic efficiency and positive impact of silver make the prepared powders a desirable choice for pharmaceutical drug degradation, helping to promote environmentally friendly and effective wastewater treatment technology.
RESUMO
Over the past few years, pharmaceutical drugs have been considered as emerging pollutants due to their continuous input and persistence in the aquatic ecosystem even at low concentrations. They have been detected worldwide in environmental matrices, indicating their ineffective removal from water and wastewaters using conventional methods. In this study we present photocatalytic purification of water from Acetaminophen and Chloramphenicol by ZnO upon UV-light illumination. Commercial ZnO powders are activated thermally (annealed at different temperatures-100, 200, 300, 400 and 500 °C for 1 h) and mechanically (treated for 5, 15, 20, 30, 40 and 60 min). The mechonoactivation is performed varying the atmosphere in air, or in suspension of ethanol and methanol. The changes in the studied material (phase composition, structure and particle size of the samples) and morphology have been investigated by means of X-ray diffraction and Scanning electron microscopy. The ZnO powders annealed at 100 °C show highest photocatalytic efficiency and rate constant of dye degradation, which is due to the smaller size of nanocrystallites and their better developed surface. The degradation rate of Acetaminophen and Chloramphenicol increases with time of mechanical activation up to 30 min and then decreases. The optimal temperature and time of mechanoactivation are experimentally established.