Browsing by Author "Leal, Leiddi Laura Maria"
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- Application of Ag-doped carbon nanotubes for wastewater treatment: antimicrobial and catalytic activityPublication . Leal, Leiddi Laura Maria; Gomes, Helder; GionaAn efficient wastewater treatment system provides economic, environmental, and social advantages that positively impact communities. Therefore, this study proposes the application of silver-doped carbon nanotubes obtained by upcycling plastic solid waste for wastewater treatment to evaluate their antimicrobial and catalytic activity. The metallic catalyst used in the chemical vapor deposition of carbon nanotubes was prepared with a composition of 88% alumina phase, 9% nickel oxide phase, and 3% cobalt ferrite phase with a polymer mix (25% low-density polyethylene, 35% high-density polyethylene, and 40% polypropylene). The carbon nanotubes were functionalized with 15.2 M nitric acid and subsequently subjected to two silver doping techniques (0.05 M): one by chemical co-precipitation with 0.05 M sodium borohydride, with 5% and 10% silver and the other by wet impregnation, also with 5% and 10% silver. The results obtained for N2 adsorption isotherms characterize the materials as Type IV, attributed to mesoporous materials. BET, thermogravimetric, and elemental analyses demonstrated that doping by wet impregnation was more efficient than doping by chemical co- precipitation, resulting in higher surface areas, up to 219 m2/g, and higher C/H ratios (1546.7) in the 10% silver wet impregnation doping. CWPO experiments demonstrated that the catalysts doped by wet impregnation with 5% and 10% silver were the only ones capable of reducing 100% of the bisphenol-A concentration (100 ppm) after 8 hours of reaction, with the CNT doped by wet impregnation with 5% silver showing the best overall performance. Adsorption and desorption experiments of the materials recovered from the reaction confirmed that the pollutant was mainly oxidized, not adsorbed, and the adsorptions observed were characterized as physisorptions. The CWPO experiment coupled with the disinfection of an Escherichia coli bacterial strain at an initial concentration of 0.5 on the McFarland scale over a simulated pollutant matrix showed that hydrogen peroxide (537 ppm), as well as the CWPO reaction using 5% silver wet impregnation doped CNT was able to eliminate 99.99% of the microorganisms, demonstrating a bactericidal effect.
- Exposure to Waste Anesthetic Gases Throughout Surgical Interventions: A Case Study in a Portuguese Local Health UnitPublication . Leal, Leiddi Laura Maria; Yamanaka, Vanessa Yukie; Pereira, Ermelinda; Theodoro, Joseane; Domingues, Maria de Fátima; Fernandes, Isabel; Gabriel, Marta Fonseca; Feliciano, ManuelThe accumulation of anesthetic gas residues in surgery units can pose health risks to healthcare professionals, highlighting the need to establish effective protection measures. This study evaluated waste anesthetic gas levels in a local health unit in northern Portugal to identify highexposure areas during surgeries using general anesthesia. Measurements of desflurane, sevoflurane, carbon dioxide, air temperature, and relative humidity were taken during 20 surgeries carried out over approximately six months. The results showed that the thermal conditions were not adequately controlled, particularly the relative humidity levels. The detectedWAG concentrations fluctuated across different locations, with concerning peaks being detected in specific settings. Desflurane levels reached 8.79 ppm in the general surgery room (GSR) and averaged 3.13 ppm in the recovery room (RR), while the sevoflurane levels averaged 2.06 ppm in the RR. High concentrations exceeding the recommendations of the U.S. National Institute for Occupational Safety and Health (NIOSH) were notably observed after endotracheal tube removal. In short surgeries, anesthetic gas levels exceeded safety limits, while long surgeries caused peaks in sevoflurane levels. Longer surgeries and higher occupancy were significantly linked to increased levels of WAG and carbon dioxide, emphasizing the need to improve ventilation and environmental controls to safeguard healthcare professionals.