Browsing by Author "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.