AASCIT Journal of Chemistry 2019; 5(2): 14-22 http://www.aascit.org/journal/chemistry Poly (Vinyl Alcohol)/Poly (Acrylic Cid)/TiO 2 /Graphene Oxide Nanocomposite Hydrogels for Photocatalytic Degradation of Organic Pollutants Asmaa El-Zoghby, Rafik Abbas, Wagih Sadik, Abdel Ghaffar El Demerdash Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt Email address Citation Asmaa El-Zoghby, Rafik Abbas, Wagih Sadik, Abdel Ghaffar El Demerdash. Poly (Vinyl Alcohol)/Poly (Acrylic Cid)/TiO 2 /Graphene Oxide Nanocomposite Hydrogels for Photocatalytic Degradation of Organic Pollutants. AASCIT Journal of Chemistry. Vol. 5, No. 2, 2019, pp. 14-22. Received: December 18, 2018; Accepted: June 2, 2019; Published: July 30, 2019 Abstract: Poly (vinyl alcohol)/poly (acrylic acid)/TiO 2 /graphene oxide nanocomposite hydrogels were prepared using radical polymerization and condensation reacti006Fn for the photocatalytic treatment of waste water. Graphene oxide was used as an additive to improve the photocatalytic activity of poly (vinyl alcohol)/poly (acrylic acid)/TiO 2 nanocomposite hydrogels. Both TiO 2 and graphene oxide were immobilized in poly (vinyl alcohol)/poly (acrylic acid) hydrogel matrix for an easier recovery after the waste water treatment. By using different ratio of both TiO 2 and GO to show the best performance for the degradation of MB dye. The photocatalytic activity of poly (vinyl alcohol)/poly (acrylic acid)/TiO 2 /graphene oxide nanocomposite hydrogels was evaluated on the base of the degradation of pollutants by using UV spectrometer. The improved removal of pollutants was due to the two-step mechanism based on the adsorption of pollutants by nanocomposite hydrogel and the effective decomposition of pollutants by TiO 2 and graphene oxide. The highest swelling of nanocomposite hydrogel was observed at pH 10 indicating that poly (vinyl alcohol)/poly (acrylic acid)/TiO 2 /graphene oxide nanocomposite hydrogels were suitable as a promising system for the treatment of basic waste water. Keywords: Graphene Oxide, Photocatalyst, Hydrogel, Poly (Acrylic Acid), Nanocomposite 1. Introduction The waste water treatments have been studied widely as the waste water from textile, paper, leather, ceramic, cosmetics, ink, and food processing industries becomes severer [1]. Synthetic organic dyes present certain hazards and environmental problems. Disposal of these dyes into water can be toxic to aquatic life. They cause a health problem because they may be mutagenic and carcinogenic [2-4]. Methods and effluent treatment for dyes may be divided into three main categories; physical, chemical, and biological. Among them adsorption technology is generally considered to be an effective method for quickly lowering the concentration of dissolved dyes in an effluent. In recent years, polymeric adsorbent have been increasingly used to remove and recover organic pollutants from waste waters [5]. Polymeric hydrogels have been the focus of research for environment scientists due to their characteristic properties such as adsorption- regeneration, economic feasibility and environmental friendly behavior [2]. The most common of these is that hydrogel is hydrophilic 3D polymer networks, that can swell in water or biological fluids and hold a large amount of them more than 20% of their dry weight, up to thousands of times their dry weight [4-5], yet are insoluble because of the presence of physical or chemical crosslinks, entanglements, or crystalline regions [5], produced by the simple reaction of one or more monomers [7]. Smart hydrogels are able to alter their volume and properties in response to environmental stimuli such as pH, temperature, ionic strength, and electric field [8]. To improve the mechanical properties of hydrogel, poly (vinyl alcohol) (PVA) was incorporated with poly (acrylic acid) (PAAc). PVA has attracted attention in the controlled drug delivery, due to the biocompatibility and the strong mechanical properties [9]. PAAc contains pendant carboxylic acid groups which can release proton in response to changes in pH. When the pH of medium is above the pKa of PAAc, the ionized PAAc network could be swelled [10]. Recently, environmental purification using TiO 2 as a photocatalyst has attracted a great deal of attention because of its high activity, chemical stability, robustness against
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AASCIT Journal of Chemistry 2019; 5(2): 14-22
http://www.aascit.org/journal/chemistry
Poly (Vinyl Alcohol)/Poly (Acrylic Cid)/TiO2/Graphene Oxide Nanocomposite Hydrogels for Photocatalytic Degradation of Organic Pollutants
Asmaa El-Zoghby, Rafik Abbas, Wagih Sadik, Abdel Ghaffar El Demerdash
Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt
hydrogel sample was placed in the pH 10.0 buffer solution to
remove any residual pollutant followed by vacuum drying at
60°C for 24.0 h. The cleaned PVA/PAAc/TiO2/GO
nanocomposites hydrogel sample was used consecutively for
the next cycle of photocatalytic decomposition.
As seen in Figure 9. The photocatalytic activity of
PVA/PAAc/TiO2/GO nanocomposite hydrogel decreased as
number of cycles increased. The removal efficiency% at first
cycle and fourth cycle for (TiO2) (0.5 and 1.0) with GO (1.25)
(w/v.%) were (94.0 and 74.0) and (91.0 and 73.0).
Figure 9. Recyclability of PVA/PAAc/TiO2/GO nanocomposite hydrogels for
photocatalytic degradation of MB in pH 10 buffer solution initial
concentration 5.0 mg/L (a) (0.5 and 1.25) and (b) (1.0 and 1.25) (w/v.%).
5. Conclusions
The pH-sensitive PVA/PAAc/TiO2/GO nanocomposite
hydrogels were prepared by radical polymerization and
condensation reac- tion in order to treat the basic waste water
more efficiently. The significant improvement of the swelling
capacities of the nanocomposites containing extremely low
GO content might be mainly due to the fact that the GO sheets
containing plenty of functional groups, such as COOH, C=O,
O-H and C-O-C groups on the surface, could dramatically
increase the density of the hydrophilic groups of the polymer
networks. The favorable electrostatic attraction is the main
interaction between methylene blue and graphene oxide. As
graphene oxide has the special nanostructural properties and
negatively charged surface, the positively charged methylene
blue molecules can be easily adsorbed on it. GO strongly
prevented TiO2 photocatalyst from the recombination of
electron–hole formed under UV irradiation resulting in the
improvement of photocatalytic activity. The best performance
hydrogels which contain 1.25 (wt/vol%) of GO with (0.5 and
1.0) (wt/vol%) of TiO2.
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