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. 2023 Jun 2;28(11):4526.
doi: 10.3390/molecules28114526.

Methylene Blue Dye Adsorption on Iron Oxide-Hydrochar Composite Synthesized via a Facile Microwave-Assisted Hydrothermal Carbonization of Pomegranate Peels' Waste

Manal Hessien  1
Affiliations

Methylene Blue Dye Adsorption on Iron Oxide-Hydrochar Composite Synthesized via a Facile Microwave-Assisted Hydrothermal Carbonization of Pomegranate Peels' Waste

Manal Hessien. Molecules. .

Abstract

The toxicity of dyes has a long-lasting negative impact on aquatic life. Adsorption is an inexpensive, simple, and straightforward technique for eliminating pollutants. One of the challenges facing adsorption is that it is hard to collect the adsorbents after the adsorption. Adding a magnetic property to the adsorbents makes it easier to collect the adsorbents. The current work reports the synthesis of an iron oxide-hydrochar composite (FHC) and an iron oxide-activated hydrochar composite (FAC) through the microwave-assisted hydrothermal carbonization (MHC) technique, which is known as a timesaving and energy-efficient method. The synthesized composites were characterized using various techniques, such as FT-IR, XRD, SEM, TEM, and N2 isotherm. The prepared composites were applied in the adsorption of cationic methylene blue dye (MB). The composites were formed of crystalline iron oxide and amorphous hydrochar, with a porous structure for the hydrochar and a rod-like structure for the iron oxide. The pH of the point of zero charge (pHpzc) of the iron oxide-hydrochar composite and the iron oxide-activated hydrochar composite were 5.3 and 5.6, respectively. Approximately 556 mg and 50 mg of MB dye was adsorbed on the surface of 1 g of the FHC and FAC, respectively, according to the maximum adsorption capacity calculated using the Langmuir model.

Keywords: adsorption; iron oxide-hydrochar composites; methylene blue dye; microwave-assisted hydrothermal carbonization method; pomegranate peels.

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Conflict of interest statement

The author declares no conflict of interest.

Figures

Figure 1
Figure 1
FT-IR spectra of (a) iron oxide (F), (b) iron oxide-hydrochar composite (FHC), and (c) iron oxide-activated hydrochar composite (FAC).
Figure 2
Figure 2
XRD of (a) iron oxide (F), (b) iron oxide-hydrochar composite (FHC), and (c) iron oxide-activated hydrochar composite (FAC).
Figure 3
Figure 3
SEM images of (a,b) iron oxide, (c,d) iron oxide-hydrochar composite, (e,f) iron oxide-activated hydrochar composite.
Figure 4
Figure 4
TEM images of (a–c) iron oxide, (d–f) iron oxide-hydrochar composites, (g–i) iron oxide-activated hydrochar composite.
Figure 5
Figure 5
pH of point of zero charge of FHC and FAC.
Figure 6
Figure 6
The relationship between (a) equilibrium adsorption capacity and initial MB dye concentration, (b) removal efficiency and initial MB dye concentration, (c) FHC experimental results and fitting models, (d) FAC experimental results and fitting models, (e) FHC Dubinin–Radushkevich fitting model, and (f) FAC Dubinin–Radushkevich fitting model.
Figure 7
Figure 7
FT-IR spectra of (a) iron oxide-hydrochar composite (FHC) after MB adsorption and (b) iron oxide-activated hydrochar composite (FAC) after MB adsorption.
Figure 8
Figure 8
(a)The N2 adsorption-desorption isotherms of FHC and FAC and (b) the pore size distribution of FHC and FAC.
Scheme 1
Scheme 1
Iron oxide-hydrochar composite (FHC) prepared by MHC treatment of pomegranate peels’ waste.
See this image and copyright information in PMC

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