Visible improvements: Owing to the plasmon resonance of silver nanoparticles deposited on the surface of AgBr, the newly-prepared plasmonic photocatalyst Ag§AgBr has a strong absorption in the visible region (see picture) and shows high efficiency in the photodegradation of organic pollutants under visible light.

Highly Efficient Visible-Light Plasmonic Photocatalyst Ag@AgBr

In view of the situation that environmental issues become more serious day by day, recent studies on practical applications of TiO 2 photocatalysis for environmental purification are reviewed. Although the fundamental aspects and the mechanisms of TiO 2 photocatalysis have recently become quite well understood, effective photocatalytic environmental purifier, especially water purifier, could not be developed to the stage of real industrial technology. The removal rate of gaseous or aqueous contaminants is influenced by numerous parameters; UV light intensity, substrate concentration, O 2 partial pressure, humidity, substrate type, and so on. Moreover, TiO 2 photocatalyst essentially has a difficulty in decomposition of large amount of contaminants or refractory chemicals. As the solutions of these problems, combination with other processes such as advanced oxidation processes and improvement of the design of photocatalytic environmental purification systems are described. During the past several years, the strategies for effective design of the system are well discussed and evaluated. The reactor design for air- or water-purification can be classified into two main strategies: (1) enlargement of reactive surface area and (2) improvement of mass transfer. Based on these insights, very recent achievements for development of photocatalytic environmental purification system with our contribution in each aspect and future research directions are reviewed.

Photoelectrochemical properties of TiO2 photocatalyst and its applications for environmental purification

Three-dimensional electrochemical process for wastewater treatment: A general review

A novel visible-light-active BiOCl/BiVO4 photocatalyst with a p–n heterojunction structure was prepared using a hydrothermal method. The photocatalytic activity of the heterojunction was investigated by monitoring the change in methyl orange (MO) concentration under visible-light irradiation. The results reveal that the composite exhibited markedly improved efficiency for MO photodegradation in comparison with pure BiVO4, BiOCl, and Degussa P25. This is ascribed to the B-type heterojunction structure with a strong oxidative ability and efficient charge separation and transfer across the BiOCl/BiVO4 p–n junction. The highest activity was obtained in the BiOCl/BiVO4 heterojunction using a composite of 13 mol % BiOCl and 87 mol % BiVO4. The removal of MO was mainly initiated by valence-band holes, but dissolved oxygen also played a crucial role in consuming the conduction-band electrons. This was verified by the effects of scavengers and N2 purging.

BiOCl/BiVO4 p–n Heterojunction with Enhanced Photocatalytic Activity under Visible-Light Irradiation

SnS2 nanocrystals with adjustable sizes were synthesized via a hydrothermal method from the aqueous solution of common and inexpensive SnCl4·5H2O, thioacetamide and citric acid, simply by varying the reaction temperature and reaction time. The structures, Brunauer–Emmett–Teller (BET) specific surface areas and optical properties of the resultant SnS2 nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption/desorption isotherms, and UV–vis diffuse reflectance spectra. Besides, their photocatalytic properties were tested for the reduction of aqueous Cr(VI) under visible light (λ > 420 nm) irradiation. It was found that the photocatalytic activities of SnS2 nanocrystals in aqueous suspension depended on their synthesis conditions. The product synthesized under suitable hydrothermal conditions (for example, at 150 °C for 12 h) not only showed high visible light-driven photocatalytic activity in the reduction of aqueous Cr(VI), but also showed good photocatalytic st...

Size-tunable hydrothermal synthesis of SnS2 nanocrystals with high performance in visible light-driven photocatalytic reduction of aqueous Cr(VI).

A TiO2-boron doped diamond (TiO2−BDD) heterojunction was employed as a photocatalyst to simultaneously oxidize an azo dye C.I. reactive yellow 15 (RY15) and reduce hexavalent chromium (Cr(VI)). This heterojunction was fabricated first by depositing a BDD film on a Ti sheet in a hot filament chemical vapor deposition reactor, followed by covering a layer of TiO2 in a metal−organic chemical vapor deposition system. The morphology of this heterojunction was characterized by using a scanning electron microscope (SEM). X-ray diffraction (XRD), Raman spectroscopy, and current–voltage (I−V) measurement were used to characterize its structures. Additionally, the characterization of surface photovoltage showed that the TiO2−BDD heterojunction exhibited a higher photovoltage response and a better ability for charge separation than the photocatalyst of TiO2 directly deposited on a Ti sheet (TiO2−Ti). The photocatalytic experiments revealed that the kinetic constants for the oxidation of RY15 and the reduction of Cr(...

Fabrication of a TiO2-BDD heterojunction and its application as a photocatalyst for the simultaneous oxidation of an azo dye and reduction of Cr(VI).

Amperometric determination of chemical oxygen demand using boron-doped diamond (BDD) sensor

A simple, environmentally friendly and continuous flow method was developed for the determination of COD based on a flow injection analysis (FIA) system, in which a BDD electrode was employed as the detecting element. The structure and the electrochemical behavior of BDD were investigated by a scanning electron microscope, Raman spectroscopy, and cyclic voltammetry, respectively. The results demonstrated that the high-quality BDD film prepared here was suitable to be used as an electrode, with which the COD measurement could be conducted. The effect of several important experimental parameters, such as applied potentials, pH, flow rates, and supporting electrolyte concentrations, on the analytical performance was investigated. Under optimized testing conditions, the proposed method was successfully applied in the COD analysis of synthetic samples. The linear range and the detection limit were 2−175 and 1 mg L−1, respectively. In addition, the COD values determined by the proposed method compared well with...

Flow Injection Analysis of Chemical Oxygen Demand (COD) by Using a Boron-Doped Diamond (BDD) Electrode

A laboratory-scale two-stage moving bed biofilm reactor was used to remove medium-strength ammonium (50–400 mg NH4+-N/L) from synthetic wastewater and pretreated monosodium glutamate wastewater, re...

Medium-Strength Ammonium Removal Using a Two-Stage Moving Bed Biofilm Reactor System

The invention relates to a device and a method for measuring the chemical oxygen demand in water based on flowing injection sampling feeding, which belongs to the technical field of environment monitoring. The measuring device is composed of a flowing injection sampler feeder, a three-electrode system electrochemical circulation detecting pool and an electrochemical working station. The inventionis characterized in that a working electrode of the electrochemical circulation detecting pool is a boron-doped diamond film electrode and is fixed on an inlet channel by a fastening bolt and is lined with a lock ring. The inlet channel, a reference electrode mounting channel and an outlet channel enlightened on an insulating, hard and corrosion-resistant pool body are mutually communicated. Whenin measurement, the pH value of a carrier liquid is 3 to 10 and the concentration thereof is 0.05 to 0.5 mol/l. When the reference electrode adopts a saturated calomel electrode or an Ag/ AgCl electrode, a positive voltage applied on the working electrode of the boron-doped diamond film electrode is 2.2 to 3.2V. The invention realizes the fast and accurate measurement of COD with no pollution.

Hongbin Yu

Papers

Fabrication of a TiO2-BDD heterojunction and its application as a photocatalyst for the simultaneous oxidation of an azo dye and reduction of Cr(VI).

Amperometric determination of chemical oxygen demand using boron-doped diamond (BDD) sensor

Flow Injection Analysis of Chemical Oxygen Demand (COD) by Using a Boron-Doped Diamond (BDD) Electrode

Medium-Strength Ammonium Removal Using a Two-Stage Moving Bed Biofilm Reactor System

Subaqueous chemical oxygen demand measuring apparatus and method and method based on flow injection sampling