Funcionalização de carvão ativado com ligante melamina para adsorção de espécies metálicas de meio aquoso
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Data
2022-09-16
Autores
Silva, Adrielli Cristina Peres da
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Universidade Estadual Paulista (Unesp)
Resumo
Diante da crescente exposição de metais pesados, houve-se a necessidade de um aprofundamento em pesquisas por parte da comunidade científica. Nesta perspectiva, o presente trabalho relata o desenvolvimento de um material adsorvente, feito a partir da folha de Typha sp., a qual foi submetida ao processo de ativação e, posteriormente, à funcionalização por meio do ancoramento de moléculas de 1,3,5-Triazina-2,4,6-triamina (melamina) para aplicação nos estudos de adsorção de Cu(II), Cd(II) e Pb(II) de meio aquoso. A funcionalização do material foi constatada por espectroscopia vibracional em infravermelho, a qual indicou bandas em 3467, 3424 e 1338 cm-1 atribuídas à vibração de estiramento de -NH2, o que pode ser um indicativo sobre a ocorrência do ancoramento do ligante na superfície do material. Análise elementar de nitrogênio corroborou os resultados da espectroscopia na região do infravermelho e apresentou 2,21% de nitrogênio no material funcionalizado, enquanto 1,30% no carvão ativado. Espectroscopia de fotoelétrons excitados por raios X mostrou a modificação da composição da superfície do material após a reação de funcionalização. Quanto aos estudos de adsorção, também se constatou que o material apresenta uma cinética rápida, com maior tendência a ser descrito pelo modelo cinético de pseudo-segunda ordem. Quanto ao pH do meio, cujo valor favorece o processo adsortivo, foi determinado em 6,0, (pHPZC = 7,5), o qual também corresponde ao valor aproximado de águas naturais. A capacidade máxima de adsorção foi de 0,4388, 0,4025 e 0,2792 mmol g-1 para Cu(II), Pb(II) e Cd(II), respectivamente. O modelo que descreve a adsorção do material, foi o modelo de Langmuir, com coeficiente de correlação de 0,99 para as três espécies citadas. Para posterior aplicação em procedimento de pré-concentração, estudos dos parâmetros como massa e vazão foram otimizados. Em análise aos resultados obtidos, o material sintetizado apresenta boas propriedades adsortivas para as espécies metálicas, se destacando dentre os materiais presentes na literatura, o que o caracteriza com grande potencial para a aplicação em remediação de áreas contaminadas.
In the face of the increasing release of heavy metals, arose a need for a more profound research by the scientific community. Based on this perspective, this work reports the production of an adsorbent material to perform the adsorption of Cu(II), Cd(II), and Pb(II) from water. The material was prepared from the activation of the leaves of Typha sp. in a heating oven under nitrogen atmosphere (N2), followed by its chemical functionalization with 1,3,5-triazine-2,4,6-triamine (melamine). The functionalization of the material was demonstrated via infrared vibrational spectroscopy, which exhibited vibrational bands 3467, 3424, and 1338 cm-1. These bands were assigned to the stretching of –NH2 groups, indicating the effective anchoring of the ligand at the surface of the material. The results from the elemental analysis corroborated those obtained by infrared vibrational spectroscopy, demonstrating a nitrogen content of 2,21% for the functionalized material, whereas the activated carbon provided 1,30%. The X-ray photoelectron spectroscopy analysis indicated the modification of the material’s surface after the functionalization step. As for the adsorption studies, it was also found that the material has fast kinetics, with a greater tendency to be described by the pseudosecond order kinetic model. Furthermore, concerning the effect of pH of the medium, we verified that the optimal pH condition for the adsorption of metal species was obtained at 6.0, close to the material’s pHPZC=7,5), is approximately within the range observed for natural waters. The maximum adsorption capacities were 0.4388, 0.4071, and 0.2792 mmol g-1 for Cu(II), Pb(II), and Cd(II), respectively. The model that better describes the adsorption behavior of the adsorbent material was the Langmuir model, which provided a correlation coefficient of 0.99 for the three aforementioned metal species. Prior to the application of the material in pre-concentration experiments, parameters such the mass of the material and flow rate were optimized. Our results demonstrated that the synthesized material presented good adsorptive properties towards metal species, standing out among those present in the literature, consisting of a promising adsorbent for the remediation of contaminated areas.
In the face of the increasing release of heavy metals, arose a need for a more profound research by the scientific community. Based on this perspective, this work reports the production of an adsorbent material to perform the adsorption of Cu(II), Cd(II), and Pb(II) from water. The material was prepared from the activation of the leaves of Typha sp. in a heating oven under nitrogen atmosphere (N2), followed by its chemical functionalization with 1,3,5-triazine-2,4,6-triamine (melamine). The functionalization of the material was demonstrated via infrared vibrational spectroscopy, which exhibited vibrational bands 3467, 3424, and 1338 cm-1. These bands were assigned to the stretching of –NH2 groups, indicating the effective anchoring of the ligand at the surface of the material. The results from the elemental analysis corroborated those obtained by infrared vibrational spectroscopy, demonstrating a nitrogen content of 2,21% for the functionalized material, whereas the activated carbon provided 1,30%. The X-ray photoelectron spectroscopy analysis indicated the modification of the material’s surface after the functionalization step. As for the adsorption studies, it was also found that the material has fast kinetics, with a greater tendency to be described by the pseudosecond order kinetic model. Furthermore, concerning the effect of pH of the medium, we verified that the optimal pH condition for the adsorption of metal species was obtained at 6.0, close to the material’s pHPZC=7,5), is approximately within the range observed for natural waters. The maximum adsorption capacities were 0.4388, 0.4071, and 0.2792 mmol g-1 for Cu(II), Pb(II), and Cd(II), respectively. The model that better describes the adsorption behavior of the adsorbent material was the Langmuir model, which provided a correlation coefficient of 0.99 for the three aforementioned metal species. Prior to the application of the material in pre-concentration experiments, parameters such the mass of the material and flow rate were optimized. Our results demonstrated that the synthesized material presented good adsorptive properties towards metal species, standing out among those present in the literature, consisting of a promising adsorbent for the remediation of contaminated areas.
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Palavras-chave
Carvão ativado, Espécies metálicas, Adsorção, Extração em fase sólida, Activated carbon, Metallic species, Adsorption, Solid-phase extraction