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. 2021 Sep 18;14(18):5394.
doi: 10.3390/ma14185394.

Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites and Their Ultra-Fast Adsorption of Methylene Blue Dye

En-Rui Wang  1 , Kun-Yauh Shih  1
Affiliations

Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites and Their Ultra-Fast Adsorption of Methylene Blue Dye

En-Rui Wang et al. Materials (Basel). .

Abstract

The industry development in the last 200 years has led to to environmental pollution. Dyes emitted by pharmaceutical and other industries are major organic pollutants. Organic dyes are a pollutant that must be removed from the environment. In this work, we adopt a facile microwave hydrothermal method to synthesize ZnFe2O4/rGO (ZFG) adsorbents and investigate the effect of synthesis temperature. The crystal structure, morphology, chemical state, and magnetic property of the nanocomposite are investigated by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and a vibrating sample magnetometer. Furthermore, the synthesized ZFGs are used to remove methylene blue (MB) dye, and the adsorption kinetics, isotherm, mechanism, and reusability of this nanomaterial are studied. The optimal ZFG nanocomposite had a dye removal percentage of almost 100%. The fitting model of adsorption kinetics followed the pseudo-second-order model. The isotherm model followed the Langmuir isotherm and the theoretical maximum adsorption capacity of optimal ZFG calculated by this model was 212.77 mg/g. The π-π stacking and electrostatic interaction resulted in a high adsorption efficiency of ZFG for MB adsorption. In addition, this nanocomposite could be separated by a magnet and maintain its dye removal percentage at almost 100% removal after eight cycles, which indicates its high suitability for utilization in water treatment.

Keywords: ZnFe2O4/rGO; dye adsorption; microwave hydrothermal method.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Scheme of the preparation of ZFG nanomaterial.
Figure 2
Figure 2
(a) XRD pattern and (b) Raman spectra of GO, rGO, ZF, and ZFGs.
Figure 3
Figure 3
(a) FT-IR spectra of GO, rGO, ZF, and ZFG and (b) magnetization hysteresis loops of ZFG and ZF.
Figure 4
Figure 4
TEM image of (a) rGO, (b) ZF, (c) ZFG-14, (d) ZFG-16, (e) ZFG-18, and (f) ZFG-20.
Figure 5
Figure 5
N2 adsorption–desorption isotherm of ZFG and pore size distributions calculated from the BJH model.
Figure 6
Figure 6
ZF, rGO, and ZFGs (a) adsorption capacity and (b) dye removal percentage. Conditions: adsorbent dosage = 10 mg, MB concentration = 10 mg L−1, T = 295 K.
Figure 7
Figure 7
Different kinetic fitting models of MB dye adsorption (a) pseudo-first-order (b) pseudo-second-order (c) Elovich; (d) intra-particle diffusion model of ZFGs. Conditions: adsorbent dosage = 10 mg, MB concentration = 10 mg L−1, T = 295 K.
Figure 8
Figure 8
Linear fitting of (a) Langmuir, (b) Freundlich, and (c) Temkin adsorption isotherm. Conditions: adsorbent dosage = 10 mg, time = 30 min, MB concentration = 10 mg L−1, T = 295 K.
Figure 9
Figure 9
(a) Adsorption behavior of ZFG-18 affected by the dye solution initial pH. (b) Dye adsorption recycle test of ZFG-18. Conditions: adsorbent dosage = 10 mg, time = 30 min, MB concentration = 10 mg L−1, T = 295 K.
Figure 10
Figure 10
(a) Raman and (b) FT-IR spectra of ZFG and ZFG-MB.
Figure 11
Figure 11
Proposed mechanism of MB dye adsorption on ZFG.
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