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. 2020 Feb 5;12(2):338.
doi: 10.3390/polym12020338.

Novel Superadsorbent Highly Porous Hydrogel Based on Arabic Gum and Acrylamide Grafts for Fast and Efficient Methylene Blue Removal

Ahmed M Elbedwehy  1 , Ayman M Atta  2
Affiliations

Novel Superadsorbent Highly Porous Hydrogel Based on Arabic Gum and Acrylamide Grafts for Fast and Efficient Methylene Blue Removal

Ahmed M Elbedwehy et al. Polymers (Basel). .

Erratum in

Abstract

Environmental pollution with dyes released from industrial effluent is one of the major and most critical problems in the world. To alleviate this issue, advanced and safe materials with fast and highly efficient dye removal should be designed. Great attention has been paid recently to hydrogels based on polysaccharides such as Arabic Gum (AG) grafted with polyacrylamide (PAM) and polyacrylic acid (PAA). These materials combine the merits of natural polymers such as biodegradability and non-toxicity with the high adsorption ability of PAM and PAA towards cationic dyes such as methylene blue (MB). Many previous works have been done to enhance three-dimensional (3D) structure and swelling ability of the graft copolymers by using a crosslinking agent or even adding nanomaterials as a filler inside the hydrogel matrix. However, these additives may negatively affect the adsorption ability, and few previous studies could reach 2000 mg/g of maximum MB capacity removal within a good period of time. In our work, we synthesized partially hydrolyzed polyacrylamide grafted Arabic gum (AG-g-PAM/PAA) to have both amide and carboxylate groups. The modified water dissolved graft product undergoes water in oil (W/O) emulsion using paraffin oil as the continuous phase and Triton X-100 as a stabilizing agent; then, the system was inversed to oil in water (O/W) emulsion by increasing the shear mixing rate and cross-linked using Epichlorohydrin (ECH). The precipitated graft product showed hierarchically interconnected micro and macropores' sponge like shape with fast water swelling and high MB adsorption capacity (2300 mg g-1) after 45 min at near neutral pH conditions.

Keywords: arabic gum; emulsion inversion; hydrogel; porous; superadsorbent; water retention.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
FT-IR spectra of (a) Acacia gum, (b) PAM-g-AG, and (c) crosslinked AG-g-PAM/PAA.
Scheme 1
Scheme 1
Graft Copolymerization of Acrylamide onto Arabic gum.
Scheme 2
Scheme 2
Crosslinking of AG-g-PAM/PAA.
Figure 2
Figure 2
Scanning electron micrographs of (a) crosslinked AG-g-PAM/PAA with conventional method (b–d) crosslinked AG-g-PAM/PAA prepared in emulsion at different magnification scale.
Scheme 3
Scheme 3
Schematic representation of crosslinked highly porous grafted gum copolymers preparation whereas the far-left side shows the adsorption of 200 ppm of MB in 100 mL distilled water after 10 min using 0.03 g of (a) crosslinked hydrogel prepared by conventional method (b) crosslinked hydrogel prepared by our method.
Figure 3
Figure 3
The swelling curve of (a) Porous AG-g-PAM/PAA hydrogel and (b) Conventional non-porous AG-g-PAM/PAA hydrogel in distilled water at room temperature and near-neutral pH.
Figure 4
Figure 4
Water retention ratio% of (a,b) porous AG-g-PAM/PAM hydrogel and (c,d) Conventional non-porous AG-g-PAM/PAA hydrogel at 45 and 60 °C respectively.
Figure 5
Figure 5
Adsorption isotherm of MB onto AG-g-PAM/PAA porous hydrogel. Adsorbent dose 30 mg/100 mL and shaking time 2 h in pH 7 and at room temperature.
Figure 6
Figure 6
Adsorption isotherm models of MB dye on crosslinked AG–g–PAM/PAA porous hydrogel: (a) Langmuir and (b) Freundlich models.
Figure 7
Figure 7
Kinetic models for adsorption of MB dye (a) pseudo-first order and (b) pseudo-second order.
See this image and copyright information in PMC

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