Titanium Dioxide/Polyvinyl Alcohol/Cork Nanocomposite: A Floating Photocatalyst for the Degradation of Methylene Blue under Irradiation of a Visible Light Source

Abstract

Photocatalytic degradation by the titanium dioxide (TiO2) photocatalyst attracts tremendous interest due to its promising strategy to eliminate pollutants from wastewater. The floating photocatalysts are explored as potential candidates for practical wastewater treatment applications that could overcome the drawbacks posed by the suspended TiO2 photocatalysis system. The problem occurs when the powdered TiO2 applied directly into the treated solution will form a slurry, making its reuse become a difficult step after treatment. In this study, the immobilization of titanium dioxide nanoparticles (TiO2 NPs) on the floating substrate (cork) employing polyvinyl alcohol (PVA) as a binder to anchor TiO2 NPs on the surface of the cork was carried out. Characterizations such as Fourier transformer infrared, X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), zeta potential, photoluminescence spectroscopy, femtosecond to millisecond time-resolved visible to mid-IR absorption spectroscopy, ion chromatography, and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX) analyses were employed. XRD analysis revealed the formation of anatase-phase TiO2 NPs. The results demonstrated that the crystallite size was 9.36 nm. The band gap energy of TiO2 NPs was determined as 3.0 eV. PL analysis verified that TiO2 NPs possessed a slower recombination rate of electron–hole pairs as compared to anatase TiO2. The result was attributed by the behavior of photogenerated charge carriers on TiO2 NPs, which existed as shallowly trapped electrons that could survive longer than a few milliseconds in this study. Furthermore, SEM–EDX analysis indicated that TiO2 NPs were well distributed on the surface of the cork. At the optimal mole ratio of TiO2/PVA (1:8), the TiO2/PVA/cork floating photocatalyst degraded at 98.43% of methylene blue (MB) under a visible light source which performed better than under sunlight irradiation (77.09% of MB removal) for 120 min. Besides, the mineralization result has measured the presence of sulfate anions after photocatalytic activities, which achieved 86.13% (under a visible light source) and 65.34% (under sunlight). The superior photodegradation performance for MB was mainly controlled by the reactive oxygen species of the superoxide radical (•O2 –). The degradation kinetics of MB followed the first-order kinetics. Meanwhile, the Langmuir isotherm model was fitted for the adsorption isotherm. The floating photocatalyst presented good reusability, resulting in 78.13% of MB removal efficiency even after five cycles. Our TiO2/PVA/cork floating photocatalyst fabrication and high photocatalytic performance are potentially used in wastewater treatment, especially under visible light irradiation.

Immobilization of a TiO2–PEDOT:PSS hybrid heterojunction photocatalyst for degradation of organic effluents

“…11–16 Polyvinyl alcohol (PVA) is a hydrophilic polymer with good flexibility and low cost and could also be potential candidate to immobilize TiO 2 . 17,18 The swelling of PVA after being in contact with an aqueous liquid may facilitate an increase in the interface area between catalyst and effluent 19–21 which would be advantageous compared to conventional substrate ( e.g. , glass, metal etc. )…”

Microfluidic Fabrication of Monodisperse and Recyclable TiO2-Poly(ethylene glycol) Diacrylate Hybrid Microgels for Removal of Methylene Blue from Aqueous Medium

“…Both problems can be addressed successfully by designing a hybrid material composed of polymeric microparticles and TiO 2 NPs. − Consequently, the use of inorganic–organic hybrid materials in adsorption, catalysis, and photocatalysis has become the subject of increasing interest. − For example, Sun et al developed an amino-functionalized TiO 2 surface molecularly imprinted polymeric system using sodium lignosulfonate as a functional monomer for highly selective removal of MB via adsorption and photocatalysis methodologies. Idris et al reported a TiO 2 /poly­(vinyl alcohol)/cork hybrid material for scavenging of MB using adsorption and photocatalysis strategies. Wei et al designed TiO 2 –P­(EGDA) composite film using photopolymerization of P­(EGDA) in the presence of TiO 2 NPs and used the resulting film for adsorptive and photocatalytic removal of Congo red dye from aqueous medium.…”

C,N-Codoped TiO2 Nanoparticles Immobilized on Floating Alginate Beads for Diazinon Removal under Solar Light Irradiation

“…This is because nontoxic and highly stable chemical catalysts are utilized in the photocatalytic reaction. , This technique is also recognized as an efficient and cost-effective treatment technology. , The use of semiconductors in photocatalysis plays a crucial role, as they are photoexcited when radiated under ultraviolet or visible light . ZnO, TiO 2 , and WO 3 are some of the semiconductors employed in the process. For instance, Budarz and co-workers successfully degraded 80% of chlorpyrifos using TiO 2 nanoparticles within 24 h …”

“…Therefore, the designation of a floating photocatalyst is an effective approach to replacing the conventional semiconductor TiO 2 catalyst. Lightweight material such as cork and expanded perlite is utilized as a carrier to immobilize the catalyst and form a photocatalyst that can float. The lightweight material offers the unique benefit of floating on the surface of the water, making it a crucial feature in the fabricated floating photocatalyst .…”