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. 2022 Nov 29;14(23):5196.
doi: 10.3390/polym14235196.

Removal of Heavy Metal Ions from Wastewater with Poly-ε-Caprolactone-Reinforced Chitosan Composite

Manuel E Martínez  1 , José René Rangel-Méndez  2 , Miquel Gimeno  3 , Alberto Tecante  3 , Gretchen T Lapidus  4 , Keiko Shirai  1
Affiliations

Removal of Heavy Metal Ions from Wastewater with Poly-ε-Caprolactone-Reinforced Chitosan Composite

Manuel E Martínez et al. Polymers (Basel). .

Abstract

Currently, the requirements for adsorbent materials are based on their environmentally friendly production and biodegradability. However, they are also related to the design of materials to sustain many cycles in pursuit of low cost and profitable devices for water treatments. In this regard, a chitosan reinforced with poly-ε-caprolactone thermoplastic composite was prepared and characterized by scanning electron microscopy; Fourier transforms infrared spectroscopy, X-ray diffraction analysis, mechanical properties, as well as erosion and swelling assays. The isotherm and kinetic data were fitted with Freundlich and pseudo-second-order models, respectively. The adsorption equilibrium capacities at pH 6 of Zn(II), Cu(II), Fe(II), and Al(III) were 165.59 ± 3.41 mg/g, 3.91 ± 0.02 mg/g, 10.72 ± 0.11 mg/g, and 1.99 ± 0.22 mg/g, respectively. The adsorbent material lost approximately 6% of the initial mass in the adsorption-desorption processes.

Keywords: adsorption; chitosan; composite; metal ions removal; poly-ε-caprolactone.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure A1
Figure A1
Heavy metal adsorption efficiency of the MCP formulations.
Figure A2
Figure A2
N2 physisorption isotherm of MCP.
Figure A3
Figure A3
FTIR spectrum of PCL.
Figure A4
Figure A4
Predicted species distribution curves for (A) Cu(II) and (B) Al(III) in the synthetic solution as a function of pH at 25 °C, elaborated with the MEDUSA software suite. Concentrations: [Cu(NO3)2] = 1.6 × 10−4 M, [FeSO4] = 3.9 × 10−4 M, [ZnSO4] = 5.1 × 10−3 M, [Cd(NO3)2] = 8.8 × 10−6 M, [Pb(NO3)2] = 2.4 × 10−5 M and [Al(NO3)3] = 1.5 × 10−4 M.
Figure A5
Figure A5
Time course of water swelling at 25 °C and RH of 45% (a) and MCP erosion behavior in acidic solution (pH 4) (b).
Figure A6
Figure A6
The pH of adsorption equilibrium solutions. Initial and final histograms with different letter mean significant differences according to Tukey-Kramer multiple comparison test (p ≤ 0.05).
Figure A7
Figure A7
The εdes of Fe, Zn and Al with 10 mL of HCl (a), HNO3 (b) and EDTA 15% + NaOH 0.5 N (c) solutions after 120 min at agitation of 50 rpm. Different letters means differences according to Tukey-Kramer multiple comparison test (p < 0.05).
Figure A7
Figure A7
The εdes of Fe, Zn and Al with 10 mL of HCl (a), HNO3 (b) and EDTA 15% + NaOH 0.5 N (c) solutions after 120 min at agitation of 50 rpm. Different letters means differences according to Tukey-Kramer multiple comparison test (p < 0.05).
Figure A8
Figure A8
The desorption efficiency of Zn(II) ions changing the desorption solution for fresh EDTA/NaOH 0.5 N volume.
Figure A9
Figure A9
EDS for MCP sample before (a) and after (b) water treatment.
Figure 1
Figure 1
CS-reinforced with PCL (a,c) and stained with CW (b,d). Arrows show Ch.
Figure 2
Figure 2
SEM micrographs for CS (a), PCL (b), MCP (c), binary image of MCP (d), analysis of particles by ImageJ (e) and average pore size distribution (f).
Figure 3
Figure 3
XRD patterns of PCL, CS and MCP.
Figure 4
Figure 4
Proton binding curve of MCP.
Figure 5
Figure 5
FTIR spectra of CS, PCL, and MCP, before and after adsorption treatment (MCPA) (a), 1650–1400 cm−1 (b), and 650–550 cm−1 regions (c), and proposed adsorption mechanism (d). The grey box represents N-H bending vibrations. The black box shows the stretching vibrations of the metal ion-MCP complex.
Figure 6
Figure 6
Adsorption experimental data fitted to isotherm models Freundlich (a), Langmuir (b), Dubinin-Radushkevich (c) and their equilibrium parameters (d).
Figure 7
Figure 7
Adsorption experimental data fitted to PSO (a) and kinetic parameters for the adsorption of heavy metals in synthetic water into MCP (b).
Figure 8
Figure 8
FTIR spectra of MCPA after desorption treatment with an EDTA solution and 0.25 or 0.5 N of NaOH (a); 1650–1400 cm−1 region (b); proposed desorption mechanism for Cu (II) (c); Fe (II) (d) and Zn (II) (e).
Figure 9
Figure 9
Desorption efficiencies of metal ions from MCPA.
Figure 10
Figure 10
(a) Adsorption (εads) and (b) desorption (εdes) efficiencies of Cu (black); Pb (red); Zn (green); Fe (yellow); Cd (blue) and Al (pink).
Figure 10
Figure 10
(a) Adsorption (εads) and (b) desorption (εdes) efficiencies of Cu (black); Pb (red); Zn (green); Fe (yellow); Cd (blue) and Al (pink).
See this image and copyright information in PMC

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