Chitosan-based hydrogels for the sorption of metals and dyes in water: isothermal, kinetic, and thermodynamic evaluation
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Chitosan-based hydrogels for the sorption of metals and dyes in water: isothermal, kinetic, and thermodynamic evaluations Tainara Vieira 1 & Samantha E. S. Artifon 2 & Cassiele T. Cesco 2 & Pâmela B. Vilela 3 & Valter A. Becegato 3 & Alexandre T. Paulino 1,2 Received: 1 May 2020 / Revised: 24 October 2020 / Accepted: 18 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The aim of the present study was to evaluate a chitosan-based hydrogel and chitosan/magnetite-based composite hydrogel as potential matrices for water treatment through sorption experiments involving metals and dyes. Cadmium and methylene blue were used as model pollutants. The best isotherm fits were found using three-parameter isotherms, indicating both the formation of a monolayer and multi-site interactions in the hydrogel networks due to the diffusion of the solutes and macromolecular relaxation of the polymer chains. Maximum methylene blue sorption capacities of the chitosan-based hydrogel and chitosan/magnetite-based composite hydrogel were 23.389 and 23.478 mg g−1, respectively. These values were respectively 90.038 and 80.383 mg g−1 for cadmium sorption. The best kinetic fit for the interaction of methylene blue and cadmium to the chitosan-based hydrogel was the nonlinear pseudo-second-order kinetic model, indicating that a chemical reaction controls the adsorption rate between the hydrogel and pollutant. The opposite was found for interaction with the chitosan/magnetite-based composite hydrogel, suggesting that the active-site occupation rate is proportional to the number of non-occupied active sites. The thermodynamic results revealed that the sorption processes were favorable and endothermic, with the possible occurrence of physical interactions. However, hydrogel swelling can alter the sorption isotherm, kinetics, and thermodynamics. The interaction of methylene blue and cadmium with both hydrogels was confirmed by Fourier-transform infrared spectroscopy and thermogravimetric analyses. Keywords Hydrogel . Interaction . Sorption . Magnetite . Pollutant
Introduction Water pollution due to contamination by dyes and metals is a worldwide environmental problem [1, 2]. Most synthetic dyes and metal cations are carcinogenic and mutagenic, and persist in the environment due to their toxicity, non-biodegradability, bioaccumulation capacity, and solubility [3]. The
* Alexandre T. Paulino [email protected] 1
Postgraduate Program in Applied Chemistry, Santa Catarina State University, Rua Paulo Malschitzki, 200, Joinville, Santa Catarina 89219-710, Brazil
2
Department of Food and Chemical Engineering, Santa Catarina State University, Br 282, km 574, Pinhalzinho, Santa Catarina 89870-000, Brazil
3
Postgraduate Program in Environmental Sciences, Santa Catarina State University, Av. Luiz de Camões, 2090, Conta Dinheiro, Lages, Santa Catarina 88520-000, Brazil
accumulation of cadmium in an organism causes damage to the kidneys, liver, intestine, reproductive system, and central ne
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