Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Environmentally Friendly Polyvinyl alcohol−alginate/bentonite Nanocomposite Hydrogel Beads as Efficient Adsorbents for Removal of Toxic Methylene Blue from Aqueous Solution

Version 1 : Received: 3 November 2021 / Approved: 8 November 2021 / Online: 8 November 2021 (14:30:34 CET)

A peer-reviewed article of this Preprint also exists.

Aljar, M.A.A.; Rashdan, S.; Abd El-Fattah, A. Environmentally Friendly Polyvinyl Alcohol−Alginate/Bentonite Semi-Interpenetrating Polymer Network Nanocomposite Hydrogel Beads as An Efficient Adsorbent for the Removal of Methylene Blue from Aqueous Solution. Polymers 2021, 13, 4000. Aljar, M.A.A.; Rashdan, S.; Abd El-Fattah, A. Environmentally Friendly Polyvinyl Alcohol−Alginate/Bentonite Semi-Interpenetrating Polymer Network Nanocomposite Hydrogel Beads as An Efficient Adsorbent for the Removal of Methylene Blue from Aqueous Solution. Polymers 2021, 13, 4000.

Abstract

Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and re-mediation. The present research work is focused on the development` and characterization of the ecofriendly polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as beneficial adsorbents for removal of toxic methylene blue (MB) from industrial water. PVA−Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating batch aqueous solutions. The experimental results indicated that the incorporation of Bent (30 w%) in the nanocomposite formulation sustained porous structure, preserved water uptake, and increased MB removal effi-ciency by 230 % compared to empty beads. Designed beads possessed higher affinity to MB at high pH 8, 30 °C, and fitted well to pseudo-second-order kinetic model a high correlation coefficient. Moreover, designed beads had a good stability and reusability as they exhibited excellent removal efficiency (90%) after six consecutive adsorption-desorption cycles. Adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed PVA−Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.

Keywords

Alginate; polyvinyl alcohol; bentonite clay; nanocomposites hydrogel; cationic dyes; water remediation.

Subject

Chemistry and Materials Science, Applied Chemistry

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