Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bacterial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

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A review on the visible light active titanium dioxide photocatalysts for environmental applications

Herein we obtained a chemically bonded TiO2 (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO2−carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO2−carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.

P25-Graphene Composite as a High Performance Photocatalyst

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.

TiO2 nanotubes: synthesis and applications.

https://cyberleninka.org/article/n/999493.pdf

New trends in removing heavy metals from industrial wastewater

Combination of Advanced Oxidation Processes and biological treatments for wastewater decontamination—A review

In this research, a sol-gel technique with dip coating method was used to prepare photocatalytic TiO2 thin films immobilized on glass plates. Titanium(IV) butoxide was used as initial substrate. The solvent was ethanol and the additive substrate was acetyl acetone. Molar ratios of TiO2 to acetyl acetone were varied as studied parameters. This study was aimed to investigate the effect of acetyl acetone on TiO 2 thin film properties that are adher- ence and corrosive property, surface morphology of thin film, TiO 2 molecular structure and photoactivity. It was found that acetyl acetone played an important role on TiO 2 thin film properties. It significantly enhanced the adherence property and provided the smooth surface of TiO2 thin film. On the contrary, acetyl acetone exerted less effect on the crystal structure of TiO 2 film and increased nanoparticle size of TiO 2 , which results in the decreasing of photocatalytic activity of the film. Findings from this research can be benefi- cial for the developments of thin film TiO 2 preparation for environmental application.

Effect of Acetyl Acetone on Property of TiO 2 Thin Film for Photocatalytic Reduction of Chromium(VI) from Aqueous Solution

Editorial: frontier technology for water treatment and pollutant removal is key for securing the present, correcting the past, and sustaining the future.

Plant extract-stabilized nanoiron for the treatment of aqueous paraquat in the presence of H2O2 and UV light

In this work, carbonaceous materials including activated carbon (AC) and carbon black (CB) were used in an enhancement the adsorption capacity of TiO2 particles. The carbon supported TiO2 composite materials denoted as TiO2/AC and TiO2/CB were prepared by sol–gel method and used in photocatalytic process of 2-chlorophenol in aqueous solution. Results reveal that both AC and CB can increase adsorption capacity of TiO2 while AC provided highest adsorption of 2-chlorophenol on its surface. Adsorption isotherms for both materials were well explained by Freundlich equation representing a multilayer of 2-chlorophenol adsorbed on titanium dioxide surface. During the irradiation, TiO2/CB exerted highest removal efficiency and initial reaction rate in 2-chlorophenol degradation among three types of catalysts, TiO2/CB, TiO2/AC and TiO2. The mineralization of 2-chlorophenol was achieved within 200 min for both TiO2/AC and TiO2/CB catalysts.

Adsorption and Degradation of 2-chlorophenol by Tio2/ac and Tio2/cb in Photocatalytic Process

In this paper, a sol-gel technique with dip coating method is used to prepare photocatalytic TiO2 thin films immobilized on glass plates. The structure and morphology of thin films are characterized with X-ray diffraction (XRD) and scanning electron microscope (SEM). The structural characterization of this film shows that the titanium oxide anatase phase is predominant at 400C-700C. The appearance of the rutile phase depends mainly on coating cycle. For example, the rutile phase appeared at 600C with 5 coating cycles. The obtainable thin films from each preparation condition were tested for photoreduction of chromium. Our results show that the photoreduction of chromium(VI) is greatly enhanced. Comparatively, the photoactivity of the prepared TiO2 thin films shows similar activity with TiO2 powder, Degussa P-25. Findings from this research are beneficial for an application of TiO2 thin film in environmental aspects.

Puangrat Kajitvichyanukul

Papers

Effect of Acetyl Acetone on Property of TiO 2 Thin Film for Photocatalytic Reduction of Chromium(VI) from Aqueous Solution

Editorial: frontier technology for water treatment and pollutant removal is key for securing the present, correcting the past, and sustaining the future.

Plant extract-stabilized nanoiron for the treatment of aqueous paraquat in the presence of H2O2 and UV light

Adsorption and Degradation of 2-chlorophenol by Tio2/ac and Tio2/cb in Photocatalytic Process

Preparation and Properties Study of TiO2 Thin Film for Photoreduction of Chromium(VI) in Photocatalysis Process