Percorrer por autor "Pereira Junior, Tairone Cesar da Silva"
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- Identification and quantification of pesticides in aqueous matrices and removal using olive pit based adsorbentsPublication . Pereira Junior, Tairone Cesar da Silva; Queiroz, Ana; Ribeiro, António E.; Rohde, CristhianeThe widespread use of pesticides in agriculture raises serious environmental and public health concerns. These chemical compounds, persistent in the environment, have the potential to contaminate soils, groundwater, and bodies of water, even at minimal concentrations. Conventional water treatment techniques do not allow for complete elimination of pesticides, highlighting the urgency for more effective remediation methods. This study proposes the development and characterization of adsorbents derived from olive pit for the removal of three pesticides (acetochlor, dimethoate, and heptachlor). Evaluating the capacity of these adsorbents for pesticide removal aims to provide sustainable and effective solutions to mitigate environmental pesticide contamination. The methodology of this work was divided into three parts. The first consisted of the preparation and characterization of adsorbents derived from olive pit, producing two activated carbons: one by chemical activation with phosphoric acid, H3PO4, called CA, and the other by physical activation in a muffle furnace at 800°C, named CP. The second part involved the identification and quantification analyses of pesticides by GC-MS, also utilizing solid-phase microextraction (SPME) technique to select the best extraction fiber for the mentioned pesticides. The third part involved the study of adsorption kinetics at three different temperatures (25°C, 35°C, and 45°C) over 24 hours. Pseudo-first-order (PFO) and pseudo- second-order (PSO) models were fitted to the experimental values, as well as adsorption isotherm models, namely Freundlich, Langmuir, and Radke. Furthermore, activation energy and adsorption equilibrium were analyzed to better understand the pesticide removal process. According to the obtained results, the acidic charcoal achieved a higher carbonization yield, 59.19%, while the physical charcoal obtained 19.40%. Additionally, the acidic charcoal exhibited a higher specific surface area with values of 488.7 for CA and only 379.2 m2/g for CP, and underwent fewer changes in terms of functional groups analyzed by FTIR compared to physically activated charcoal. The best fiber for SPME extraction of pesticides was the blue PDMS/DVB(+OC) (Polydimethylsiloxane/ Divinylbenzene) which better identified dimethoate. Physically activated charcoal proved effective in removing heptachlor, achieving 99% removal in 300 minutes and requiring only 15 mg of adsorbent for 10 ppm of pollutant, while using the same concentration of acetochlor, a removal rate of 98% was achieved, requiring 30 mg of adsorbent in 300 min. The kinetic study results were better fitted to the pseudo-second-order model, with better results observed at 25°C and an equilibrium time of 5 hours; the Radke model allowed for better fitting to the equilibrium isotherms for both pesticides. It was observed that the carbons have great removal potential, and in the future, new conditions can be applied to study the potential of the carbons, as well as the mixture of pesticides.
- Remoção de herbicidas usando carvão ativado produzido a partir de caroço de azeitonaPublication . Pinheiro, Maísa Saldanha; Pereira Junior, Tairone Cesar da Silva; Menezes, Maraísa L.; Queiroz, Ana; Ribeiro, António E.; Brito, PauloOs pesticidas são compostos sintéticos ou biológicos utilizados no controlo de pragas na agricultura. Os herbicidas são uma importante classe de pesticidas, sendo responsáveis por inibir o desenvolvimento de ervas daninhas nocivas, sendo de extrema importância na manutenção sanitária de diferentes culturas agrícolas. O alacloro, o metolacloro e a terbutilazina encontram-se entre os herbicidas mais usados em todo o território nacional, mais especificamente na região do Nordeste e do Alto Trás-os-Montes . O crescente uso de herbicidas tem como consequência, entre outros, a contaminação indesejada de corpos hídricos, como rios, estações de tratamento ou outros ambientes aquáticos. Diferentes estudos já publicados, demonstraram que a concentração dos herbicidas referidos, excedia, em determinado momento, o limite máximo permitido pela legislação Europeia. Em estudos recentes, desenvolvidos dentro do nosso grupo de trabalho, otimizaram-se as metodologias analíticas necessárias para a deteção e quantificação destes pesticidas em matrizes aquosas. No presente trabalho apresentam-se alguns resultados experimentais obtidos no desenvolvimento de um carvão ativado obtido de caroço de azeitona, um resíduo da olivicultura, para a remoção por adsorção de diferentes herbicidas. Os estudos agora desenvolvidos envolvem a preparação, ativação e caracterização do adsorvente assim como alguns resultados de equilíbrio de adsorção e de cinética de adsorção.
- Removal of pesticides from water using activated carbon obtained from olive pitPublication . Pereira Junior, Tairone Cesar da Silva; Pinheiro, Maísa Saldanha; Rohde, Christhiane; Queiroz, Ana; Brito, Paulo; Ribeiro, António E.Currently, there is rampant population growth that requires a proportional increase in food production. In this context, the use of pesticides to improve agricultural productivity stands out. The global annual consumption is about 2 million tons; for example, in Portugal alone in 2020, 9.7 thousand tons were used to combat weeds, pests, pathogens, and other undesirable organisms . This excessive use of pesticides has many environmental impacts, such as soil and water pollution, the selection of resistant organisms, the need for increased concentrations and/or application frequency, as well as the substitution with more toxic products. It also affects non-target organisms and human health. An alternative to reduce contamination at the source and related environmental impacts of pesticides is sustainable agricultural crop management. There are also sustainable remediation methods that can be applied and seek to use active ingredients from natural and recycled sources. In this work, we aim to use the olive pit as a precursor for the production of an adsorbent charcoal for the removal of pesticides such as acetochlor, heptachlor, and dimethoate from aquatic bodies [2]. Based on effective results in removing pharmaceuticals from aqueous effluents and purifying biodiesel with the same material, it was decided to produce charcoal using both physical and chemical activation methods to optimize a removal process, which may include pesticides . Charcoal was produced with acid activation by impregnating it with orthophosphoric acid (H3PO4) for 24 hours at 25ºC on a mechanical stirrer at 160 rpm. It was then filtered through a porous filter using a vacuum pump and dried in an oven at 110ºC. It was carbonized in a muffle furnace at 500ºC for 1.5 hours and then washed with distilled water until reaching a pH between 6 and 7. The same process was applied to basic activation using potassium hydroxide (KOH). Physical activation was done directly in a muffle furnace at 800ºC, then by washing until reaching a pH between 6 and 7 [. Table 1 provides some data related to the charcoal preparation conditions. One of the objectives of this work is to achieve the highest efficiency in removing pesticides from water using the activated charcoal obtained from olive pit. The expected results involve charcoal that can retain the highest amount of the studied pesticides on its surface area.