Síntese e aplicação de policloreto de vinila (PVC) modificado com extrato da folha de mamona (Ricinus communis L.) e solvente sustentável para remoção de metais do Rio Tietê
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Data
2023-04-26
Autores
Pasta, Paula Chiachia [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Verifica-se a crescente procura por produtos cada vez mais sustentáveis em relação ao desenvolvimento de novos materiais para aplicação em procedimentos de Extração em Fase Sólida (EFS) de metais tóxicos e potencialmente tóxicos. Em virtude da intensa utilização de polímeros à base de policloreto de vinila (PVC), a grande disponibilidade desse material oriundo de resíduos é altamente presente na cadeia produtiva. O PVC possui, na sua estrutura polimérica, átomos de cloro (Cl), os quais podem ser facilmente substituídos em reações orgânicas sem geração de resíduos tóxicos. Um dos objetivos do presente projeto consistiu na modificação do adsorvente à base de PVC com extrato etanólico 70% das folhas de mamona para promover o aumento de sua capacidade adsortiva, sendo caracterizado por meio das técnicas de Espectroscopia na Região do Infravermelho (FTIR), Ressonância Magnética Nuclear (RMN), Espectroscopia de Energia Dispersiva de raios X (EDX), detectando grupos químicos contendo oxigênio por meio de análises de Espectroscopia de fotoelétrons excitados por raios X (XPS). Além disso, constatou-se que valores de pH entre 5,0 e 6,0 foram os mais favoráveis para promover a adsorção. Verificou-se que a adsorção foi rápida, obtendo o equilíbrio a partir de 30 minutos, com adsorção máxima a partir de 40 minutos, aplicando-se o modelo de pseudossegunda ordem o qual se ajustou mais adequadamente à isoterma, corroborando com o tipo de quimissorção. Nos experimentos de capacidade máxima de adsorção, foram atingidos os valores máximos de 0,3329 mmol g-1 para cobre, 0,4154 mmol g-1 para cádmio e 0,4590 mmol g-1 para cobalto. O material adsorvente também foi aplicado em ensaios no sistema em fluxo (em coluna) para recuperação dos metais em amostras com padrão conhecido e em amostra do Rio Tietê, obtendo valores significativos para fator de enriquecimento: no caso do cobre (próximo a 20), e valores de recuperação expressivos para cobre (95,5%) e cobalto (77,5%). Tais dados permitem concluir que foram obtidos valores significativos de adsorção e recuperação dos metais analisados tanto nos estudos preliminares, quanto nas aplicações em amostra real do Rio Tietê.
There is a growing demand for increasingly sustainable products towards the development of new materials for application in Solid Phase Extraction (SPE) procedures for toxic and potentially toxic metals. Due to the intense use of polymers based on polyvinyl chloride (PVC), the wide availability of this material from waste is highly present in the production chain. The molecule of PVC has chlorine atoms (Cl) in its polymeric structure, which can be easily replaced in organic reactions without generating toxic waste. One of the objectives of the present project was to modify the PVC-based adsorbent with 70% ethanolic extract of castor bean leaves to promote an increase in its adsorptive capacity, characterized by means of Infrared Spectroscopy (FTIR), Resonance Nuclear Magnetic (NMR), X-ray Energy Dispersive Spectroscopy (EDX), detecting oxygen chemical groups through X-ray Excited Photoelectron Spectroscopy (XPS) analyses. Furthermore, it was found that pH values between 5.0 and 6.0 were the most favourable to promote adsorption. It was verified that the adsorption was fast, reaching equilibrium after 30 minutes, with maximum adsorption after 40 minutes, and it was applied the pseudo-second order model, which adjusted more adequately to the isotherm, corroborating the type of chemisorption . In the maximum adsorption capacity experiments, the maximum values of 0.3329 mmol g-1 for copper, 0.4154 mmol g-1 for cadmium and 0.4590 mmol g-1 for cobalt were reached. The adsorbent material was also applied in tests in the flow system (in column) for the recovery of metals in samples with a known pattern and in a sample from the Tietê River, obtaining significant values for the enrichment factor: in the case of copper (close to 20), and significant recovery values for copper (95.5%) and cobalt (77.5%). Such data allow us to conclude that significant values of adsorption and recovery of the analyzed metals were obtained both in the preliminary studies and in the applications in a real sample from the Tietê River.
There is a growing demand for increasingly sustainable products towards the development of new materials for application in Solid Phase Extraction (SPE) procedures for toxic and potentially toxic metals. Due to the intense use of polymers based on polyvinyl chloride (PVC), the wide availability of this material from waste is highly present in the production chain. The molecule of PVC has chlorine atoms (Cl) in its polymeric structure, which can be easily replaced in organic reactions without generating toxic waste. One of the objectives of the present project was to modify the PVC-based adsorbent with 70% ethanolic extract of castor bean leaves to promote an increase in its adsorptive capacity, characterized by means of Infrared Spectroscopy (FTIR), Resonance Nuclear Magnetic (NMR), X-ray Energy Dispersive Spectroscopy (EDX), detecting oxygen chemical groups through X-ray Excited Photoelectron Spectroscopy (XPS) analyses. Furthermore, it was found that pH values between 5.0 and 6.0 were the most favourable to promote adsorption. It was verified that the adsorption was fast, reaching equilibrium after 30 minutes, with maximum adsorption after 40 minutes, and it was applied the pseudo-second order model, which adjusted more adequately to the isotherm, corroborating the type of chemisorption . In the maximum adsorption capacity experiments, the maximum values of 0.3329 mmol g-1 for copper, 0.4154 mmol g-1 for cadmium and 0.4590 mmol g-1 for cobalt were reached. The adsorbent material was also applied in tests in the flow system (in column) for the recovery of metals in samples with a known pattern and in a sample from the Tietê River, obtaining significant values for the enrichment factor: in the case of copper (close to 20), and significant recovery values for copper (95.5%) and cobalt (77.5%). Such data allow us to conclude that significant values of adsorption and recovery of the analyzed metals were obtained both in the preliminary studies and in the applications in a real sample from the Tietê River.
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Palavras-chave
Adsorção, Extração em Fase Sólida, Metais, Rio Tietê, Sustentabilidade, Adsorption, Solid Phase Extraction, Metals, Tietê River, Sustainability