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Equilibrium Isotherms, Kinetics, and Thermodynamics of the Adsorption of 2,4-Dichlorophenoxyacetic Acid to Chitosan-Based Hydrogels

Authors
  • Vieira, Tainara1
  • Becegato, Valter Antonio2
  • Paulino, Alexandre Tadeu1, 3
  • 1 Santa Catarina State University, Rua Paulo Malschitzki, 200, Joinville, SC, CEP 89219-710, Brazil , Joinville (Brazil)
  • 2 Santa Catarina State University, Av. Luiz de Camões, 2090, Lages, SC, CEP 88520-000, Brazil , Lages (Brazil)
  • 3 Santa Catarina State University, Br 282, km 574, Pinhalzinho, SC, CEP 89870-000, Brazil , Pinhalzinho (Brazil)
Type
Published Article
Journal
Water Air & Soil Pollution
Publisher
Springer-Verlag
Publication Date
Feb 05, 2021
Volume
232
Issue
2
Identifiers
DOI: 10.1007/s11270-021-05021-6
Source
Springer Nature
Keywords
License
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Abstract

The aim of this work was to study the equilibrium isotherms, kinetics, and thermodynamics of the adsorption of 2,4-dichlorophenoxyacetic acid to a chitosan-based hydrogel and chitosan/magnetite-based composite hydrogel containing 1.0% (w/w) magnetite. The hydrogel synthesis and adsorption processes were confirmed by Fourier transform-infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Adsorption was affected by contact time, solution pH, initial 2,4-D concentration, and solution temperature. The maximum 2,4-D adsorption capacities of the chitosan-based hydrogel and chitosan/magnetite-based composite hydrogel were 75.29 and 45.33 mg of pollutant per g of dried hydrogel, respectively, determined by the Sips isotherm model. The calculation of Gibbs free energy, enthalpy, and entropy revealed the occurrence of spontaneous, endothermic, disordered processes. The adsorption mechanism takes place by monolayer formation and multisite intra/intermolecular interactions, according to the nonlinear Sips isotherm model. In conclusion, the adsorption of 2,4-D to the hydrogels takes place by diffusion processes, intra/intermolecular interactions, and macromolecular relaxation of the polymer network. Desorption processes confirmed the adsorption mechanism. The hydrogels synthesized in this work are efficient solid matrices for the removal of 2,4-dichlorophenoxyacetic acid and chemical oxygen demand from polluted water and wastewater.

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