Chitosan and gum arabic nanoparticles for heavy metal adsorption

Chitosan (CT) is a polysaccharide with the ability to adsorb metals on its surface. In this work, CT-based nanoparticles (NPs) are produced by complex formation with gum arabic (GA) to increase their adsorbent potential for removal of heavy metals in aqueous medium. Adsorption efficiency is evaluated as a function of NP composition and polysaccharide concentration. NPs are sized from 250 to 375 nm at a zeta potential up to -25 mV, suggesting stability to adsorb metals. In particular, CTGA56 and CTGA80 NPs adsorbed a substantially higher amount of copper ions than pure CT. Adsorption kinetics studies showed that the reaction process followed a pseudo second-order model and the adsorption isotherm results fit a Langmuir model, highlighting the monolayer adsorption process with prominent adsorption capacity. These findings indicate the adsorbent potential of CTGA NPs and suggest that these particles can be used for removal of metal ions from contaminated water sources

Preparação, modificação quimica e calorimetria do biopolimero quitosana

Orientador: Claudio AiroldiDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de QuimicaResumo: As quitosanas C e F foram preparadas a partir do biopolímero natural quitina de casca de camarão. O efeito interativo de Cu com a quitina, com as quitosanas C e F e com a quitosana comercial A, foi estudado via calorimetria. A quitosana F foi modificada quimicamente com o glutaraldeído e com silanos organofuncionalizados. Foi investigada a capacidade de adsorção de Cu e de imobilização de quatro diferentes enzimas pela quitina, quitosana F e quitosanas modificadas. A energia livre de Gibbs das interações quitina-Cu e quitosanas-Cu demonstram que os processos são favoráveis à interação polímero-Cu .As entalpias dessas interações são exotérmicas, sendo que para as interações quitosanas-Cu são bem superiores à interação quitina-Cu.A entropia da interação quitina-Cu demonstra um aumento na desordem do sistema, o contrário foi observado para as entropias das interações quitosanas-Cu. A concentração do glutaraldeído afeta as propriedades fisicas e químicas das quitosanas modificadas com este reagente formador de ligações cruzadas, gerando uma série de produtos QGX (X = 0,0 a 25,0). Estes possuem maior capacidade em adsorver o Cu que a quitosana original, entretanto, menor que a QG0,0. Conforme aumenta a concentração de glutaraldeído diminui a capacidade de adsorção de Cu. Os híbridos obtidos com agentes sililantes apresentam-se no estado de hidrogel. Depois de secos mostram ser amorfos e insolúveis em solventes orgânicos, em meios alcalinos e ácidos. Com exceção do SiGQ1 os híbridos apresentam superior capacidade de adsorção de Cuem relação à quitosana e esta capacidade aumenta conforme cresce o tamanho da cadeia orgânica do organossilano. Entretanto, um comportamento oposto é observado para a capacidade de imobilizar enzimas, urease, glucose oxidase, catalase e invertase.Abstract: Chitosans C and F were prepared starting from the natural biopolymer chitin of shrimp shell. The interactive effects of Cu with chitin, chitosans C and F and commercial chitosan A were followed via calorimetry. Chitosan F was chemically modified with glutaraldehyde and silylating agents. The capacity of adsorption of Cu and the imobilization of four different enzymes for the chitin, chitosan F and modified chitosans were verified. Gibbs free energy of the chitin-Cuand chitosans-Cu interactions demonstrates that the processes are favorable. The enthalpies of these interactions are exothermic and the enthalpic values of chitosans-Cu interactions are greater than those of chitin-Cu interaction. The entropy of the chitin-Cu interaction indicates a decrease in the order of the system and the opposite was observed for the chitosans-Cu interactions. The concentration of glutaraldehyde affects the physical and chemical properties of the modified chitosans, originating a series of products QGX (X = 0,0 to 25,0). These chitosans had larger capacity in adsorbing Cu than the original chitosan but smaller than that of QG0,0. By increasing of the glutaraldehyde concentration, a decrease of the capacity of adsorption of Cu was observed. The hybrids obtained from chitosan and silylating agents were hidrogels. After drying, a amorphous solid, insoluble in organic solvents and in alkaline and acid solutions, was obtained. With exception of SiGQ1, the other hybrids presented larger capacity of adsorption of Cu in relation to the chitosan. This capacity increased as the size of the organic chain of the silylating agents increased. However, an opposite behaviowr is observed for the capacity of immobilizing enzymes, urease, glucose oxidase, catalase and invertase.Mestrad

Chitosan and gum arabic nanoparticles for heavy metal adsorption

<div><p>Abstract Chitosan (CT) is a polysaccharide with the ability to adsorb metals on its surface. In this work, CT-based nanoparticles (NPs) are produced by complex formation with gum arabic (GA) to increase their adsorbent potential for removal of heavy metals in aqueous medium. Adsorption efficiency is evaluated as a function of NP composition and polysaccharide concentration. NPs are sized from 250 to 375 nm at a zeta potential up to -25 mV, suggesting stability to adsorb metals. In particular, CTGA56 and CTGA80 NPs adsorbed a substantially higher amount of copper ions than pure CT. Adsorption kinetics studies showed that the reaction process followed a pseudo second-order model and the adsorption isotherm results fit a Langmuir model, highlighting the monolayer adsorption process with prominent adsorption capacity. These findings indicate the adsorbent potential of CTGA NPs and suggest that these particles can be used for removal of metal ions from contaminated water sources.</p></div

Chitosan and gum arabic nanoparticles for heavy metal adsorption

<div><p>Abstract Chitosan (CT) is a polysaccharide with the ability to adsorb metals on its surface. In this work, CT-based nanoparticles (NPs) are produced by complex formation with gum arabic (GA) to increase their adsorbent potential for removal of heavy metals in aqueous medium. Adsorption efficiency is evaluated as a function of NP composition and polysaccharide concentration. NPs are sized from 250 to 375 nm at a zeta potential up to -25 mV, suggesting stability to adsorb metals. In particular, CTGA56 and CTGA80 NPs adsorbed a substantially higher amount of copper ions than pure CT. Adsorption kinetics studies showed that the reaction process followed a pseudo second-order model and the adsorption isotherm results fit a Langmuir model, highlighting the monolayer adsorption process with prominent adsorption capacity. These findings indicate the adsorbent potential of CTGA NPs and suggest that these particles can be used for removal of metal ions from contaminated water sources.</p></div