Síntese e caracterização de nanopartículas de quitosana para adsorção de metais pesados
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Data
2021-12-14
Autores
Kobashigava, Renata Sayuri
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os metais pesados (MPs) são considerados, entre os poluentes, os mais tóxicos devido à sua persistência no ambiente e bioacumulação nos organismos vivos, levando à problemas de saúde quando em altas concentrações. As nanopartículas de quitosana (NQs) possuem muitas aplicações em razão de sua constituição peculiar e propriedades físico-químicas específicas como o tamanho, estabilidade e maior área de superfície. Desta forma, este estudo propôs a síntese de NQs, utilizando a técnica de gelificação iônica, para uso como nanomaterial na adsorção de MPs. As análises de estabilidade físico-química em relação ao tempo e ao pH foram realizadas utilizando o potencial Zeta (ζ), tamanho de partícula (TP) e índice de polidispersividade (PdI) como parâmetros de monitoramento. Além disso, com o objetivo de caracterizar morfologicamente, as NQs foram estudadas por espectroscopia no infravermelho por transformada de Fourier (FTIR) e microscopia eletrônica de varredura (MEV). Concluiu-se que o aumento da concentração de quitosana (QT) resultou em TPs maiores e potenciais ζ insatisfatórios. Considerando as velocidades de mistura, as mais rápidas contribuíram com TPs menores, mas não no intervalo aceitável, e carga de superfície indesejada. Alterando a concentração de QT, razão mássica e tipo de gotejador foi obtido NQs mais adequadas. A partir da análise de estabilidade físico-química em função do tempo, o método utilizando a seringa com agulha como gotejador resultou em NQs mais estáveis com TPs médio, potencial ζ e PdI na região esperada para esta classe de nanomaterial polimérico. As NQs apresentaram TPs médio de 283,3 ± 165,2 nm, PdI de 0,836 ± 0,118 e ζ aproximado de 29 mV (29,1 ± 1,5 mV), as análises foram realizadas no período de 83 dias. O efeito do pH na estabilidade físico-química das NQs mostraram TPs menores em soluções com pH 2 (37,8 ± 6,7 nm) e pH 10 (168,5 ± 7,5 nm) e tamanho aumentado em pH 5,5 (624,7 ± 56,4 nm) e 7 (967,9 nm). O maior potencial ζ obtido foi a pH 5,5 (28,8 ± 0,4 mV) e uma diminuição significativa do potencial ζ foi observada em soluções neutras (11,1 ± 0,6 mV) e alcalinas (4,7 ± 0,1 mV). Nos resultados de FTIR da QT e NQs, notou-se um aumento das ligações de hidrogênio e um aumento no pico do grupo amida I para NQs. Pela MEV, foi possível observar uma morfologia esférica com tamanhos entre 20,6 nm e 29,4 nm das NQs. Por fim, verificou-se que as NQs foram produzidas em TP e ζ satisfatórios e a síntese foi comprovada pelas análises de FTIR e MEV. De acordo com a literatura, notou-se que a adsorção de NQs podem ser bem descritos pela isoterma de Langmuir e modelo de pseudo-segunda ordem.
The heavy metals (HM) are considered, among the different types of pollutants, one of the most toxic and carcinogenic due to their accumulation in the living organism, leading to health problems when in high concentrations. Chitosan nanoparticles (CNs) have a wide functionality due to their characteristic structure and specific physicochemical properties such as size, stability and larger surface area. Therefore, this research aims to synthesize CNs, using the ionic gelation technique, for use as a nanomaterial for the adsorption of HMs. Physicochemical stability over the time and pH analysis were performed using Zeta potential (ζ), particle size (PS) and polydispersity index (PdI) as monitoring parameters. In addition, the CNs were performed with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), with the objective of structural and morphological characterization. It was concluded that the increase in the concentration of chitosan resulted in higher PS and unsatisfactory ζ potentials. Considering the mixing speeds, the faster ones contributed to lower PS, but not within the acceptable range, and unwanted surface charge. Changing the chitosan concentration, mass ratio and type of dropper created suitable CNs. From the analysis of physicochemical stability as a function of time, the method using the syringe with needle as a dripper resulted in stable CNs with average PS, ζ potential and PdI in the region expected for this class of polymeric nanomaterial. The CNs showed average PS of 283.3 ± 165.2 nm, PdI of 0.836 ± 0.118 and ζ around 29 mV (29.1 ± 1.5 mV), the analyses were performed over 83 days. The effect of pH on the physicochemical stability of CNs, showed smaller PS in solutions with pH 2 (37.8 ± 6.7 nm) and pH 10 (168.5 ± 7.5 nm) and increased PS in pH 5.5 (624.7 ± 56.4 nm) and 7 (967.9 nm). The highest ζ potential obtained was at pH 5.5 (28.8 ± 0.4 mV) and a significant decrease in the ζ was observed in neutral (11.1 ± 0.6 mV) and alkaline (4.7 ± 0.1 mV) solutions. In the FTIR analysis of chitosan and CNs, an increase in hydrogen bonds and an increase in the N-H peak of the amide II group for CNs were observed. Using SEM, it was possible to observe a spherical morphology with sizes between 20.6 nm and 29.4 nm of the CNs. Finally, it was found that the NQs were produced in a satisfactory PS and ζ potential and the synthesis was proven by FTIR and SEM analyses. According to the literature, it was noted that NQs adsorption can be well described by the Langmuir isotherm and pseudo second order model.
The heavy metals (HM) are considered, among the different types of pollutants, one of the most toxic and carcinogenic due to their accumulation in the living organism, leading to health problems when in high concentrations. Chitosan nanoparticles (CNs) have a wide functionality due to their characteristic structure and specific physicochemical properties such as size, stability and larger surface area. Therefore, this research aims to synthesize CNs, using the ionic gelation technique, for use as a nanomaterial for the adsorption of HMs. Physicochemical stability over the time and pH analysis were performed using Zeta potential (ζ), particle size (PS) and polydispersity index (PdI) as monitoring parameters. In addition, the CNs were performed with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), with the objective of structural and morphological characterization. It was concluded that the increase in the concentration of chitosan resulted in higher PS and unsatisfactory ζ potentials. Considering the mixing speeds, the faster ones contributed to lower PS, but not within the acceptable range, and unwanted surface charge. Changing the chitosan concentration, mass ratio and type of dropper created suitable CNs. From the analysis of physicochemical stability as a function of time, the method using the syringe with needle as a dripper resulted in stable CNs with average PS, ζ potential and PdI in the region expected for this class of polymeric nanomaterial. The CNs showed average PS of 283.3 ± 165.2 nm, PdI of 0.836 ± 0.118 and ζ around 29 mV (29.1 ± 1.5 mV), the analyses were performed over 83 days. The effect of pH on the physicochemical stability of CNs, showed smaller PS in solutions with pH 2 (37.8 ± 6.7 nm) and pH 10 (168.5 ± 7.5 nm) and increased PS in pH 5.5 (624.7 ± 56.4 nm) and 7 (967.9 nm). The highest ζ potential obtained was at pH 5.5 (28.8 ± 0.4 mV) and a significant decrease in the ζ was observed in neutral (11.1 ± 0.6 mV) and alkaline (4.7 ± 0.1 mV) solutions. In the FTIR analysis of chitosan and CNs, an increase in hydrogen bonds and an increase in the N-H peak of the amide II group for CNs were observed. Using SEM, it was possible to observe a spherical morphology with sizes between 20.6 nm and 29.4 nm of the CNs. Finally, it was found that the NQs were produced in a satisfactory PS and ζ potential and the synthesis was proven by FTIR and SEM analyses. According to the literature, it was noted that NQs adsorption can be well described by the Langmuir isotherm and pseudo second order model.
Descrição
Palavras-chave
Nanotecnologia, Nanopartículas de quitosana, Metais Pesados, Adsorção, Remediação, Nanotechnology, Chitosan nanoparticles, Heavy Metals, Adsorption, Remediation