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The nanosized Fe3O4 catalyst was synthesized via a modified reverse coprecipitation method and characterized by means of a scanning electron microscope (SEM) and an X-ray diffraction (XRD) analysis...

The characteristics and influencing factors for dinitrotoluene degradation by nano-Fe3O4-H2O2 were studied, and the nano-scale Fe3O4 catalyst was prepared by the coprecipitation method, with dinitrotoluene wastewater as the degradation object. The results showed that the catalytic reaction system within the pH value range of 1 to 9 could effectively degrade dinitrotoluene, and the optimal pH value was 3; with the increase of catalyst dosage, the degradation efficiency and the catalytic reaction rate of dinitrotoluene grew as well. The optimal catalyst dosage was 1.0 g/L when the H2O2 dosage was within the range of 0 to 0.8 mL/L; the degradation efficiency and reaction rate grew with the increase of H2O2 dosage. With further increase of H2O2 dosage, degradation efficiency and reaction rate decreased; under the best conditions with the H2O2 dosage of 0.8 mL/L, the catalyst concentration of 1 g/L and the pH value of 3 at room temperature (25 °C), the degradation rate of the 100-mg/L dinitrotoluene in...

The aim of this work was to study the retention and separation of 4BS dye from aqueous solution using N-doped TiO2 (N-TiO2) ceramic membrane. An N-TiO2 sol was synthesized by the sol–gel technique and applied to a ceramic membrane to synthesize a composite membrane. XRD analysis confirmed that the N-TiO2 had an anatase structure. SEM images revealed that the TiO2 particles with a diameter of 7–9 nm had been loaded on a ceramic support to form the nanoporous composites. 4BS dye containing aqueous solution was treated by the composite membranes. The operating conditions studied were the dye concentration, solution pH, the pressure and velocity of cross flow. With the coupling of photocatalysis and membrane separation, the retention rate of 99% for dye and the higher permeation flux (over 96%) were obtained. The composite membranes were found to be stable and to perform reproducibly.

This research measured the effectiveness of Si-FeOOH as a type of heterogeneous Fenton-like catalyst made from alkaline precipitation methods, in catalyzing the degradation of 2,4-dichlorophenol (2,4-DCP) wastewater. Factors including catalyst dosage, pH, and hydrogen peroxide dosage were investigated, showing: with an initial concentration of 2,4-dichlorophenol at 100 mg/L, a dosage of catalyst at 0.1 g/L, a dosage of H2O2 at 1.5 ml/L, pH at 5 and indoors temperature at 25 ± 1 °C, the degradation rate of 2,4-dichlorophenol, CODCr and TOC has reached 94.21%, 83.67%, and 76.11%, separately. Comparisons were made with FeOOH used as catalyst, showing that Fenton-like Si-FeOOH is a better catalyst than FeOOH.

The catalytic activity of carbon nanotubes-supported vanadium oxide (V2O5/CNTs) catalysts in the selective catalytic reduction (SCR) of NO with NH3 at low temperatures (≤ 250 °C) was investigated. The effects of V2O5 loading, reaction temperature, and presence of SO2 on the SCR activity were evaluated. The results show that V2O5/CNTs catalysts exhibit high activity for NO reduction with NH3 at low-temperatures. The catalysts also show very high stability in the presence of SO2. More interestingly, their activities are significantly promoted instead of being poisoned by SO2. The promoting effect of SO2 is distinctly associated with V2O5 loading, particularly maximized at low V2O5 loading, which indicated the role of CNTs support in this effect. The promoting effect of SO2 at low temperatures suggests that V2O5/CNTs catalysts are promising catalytic materials for low-temperature SCR reactions.

The aim of this work was to study the preparation of SiC-supported V2O5 catalysts and the kinetics on selective catalytic reduction for NO with NH3 on the catalysts. Using incipient wetness impregnation methods, vanadium oxide was applied to silicon carbide to prepare a SiC-supported vanadium oxide. X-ray photoelectron spectroscopy analysis confirmed that V2O5 existed in the prepared materials. Using the prepared materials as catalysts, selective catalytic reduction for NO by NH3 has been analyzed, and reaction kinetics on the catalysts was studied at 150–300 °C. The obtained results showed that the reduction reaction on the catalysts is close to zero-order kinetics with respect to NH3, first-order with respect to NO, and half-order to O2. Apparent activation energy for the reduction reaction was found to be 38 kJ mol−1. The prepared materials are stable and reusable.

Carbon nanotube (CNT) supported copper oxide catalysts were prepared, and the morphology and structure of the catalyst were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and temperature-programmed desorption experiments. The CuO/CNT catalysts demonstrated high catalytic activities during the selective catalytic reduction (SCR) of NO with NH3 over a temperature range of 150–250 °C. The amount of NH3 adsorbed on the catalyst surface was greater than that of NO or NO + O2 adsorbed on the catalyst surface. These results suggest that the SCR reaction might proceed on the surface of the CuO/CNT catalysts and occur between the adsorbed ammonia and gas phase NO or weakly adsorbed NO. The CuO/CNT catalysts exhibited good stability at low temperatures, which makes them suitable for potential applications in industry.

Magnetic alginate/γ-Fe2O3/CdS composite photocatalyst (m-alginate/Fe2O3/CdS composite) was synthesized via a simple hydrothermal method, and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM). The photocatalytic activity of m-alginate/Fe2O3/CdS composite was evaluated via the adsorption-photocatalytic removal of aqueous organic dye, i.e. congo red (CR). The m-alginate/Fe2O3/CdS composite can be easily manipulated and separated by a magnetic field, leading to the convenience and feasibility in the removal of aqueous hazardous dye. In addition, the kinetics of photocatalysis of CR has also been performed and found to follow the pseudo-first-order kinetics. These results suggest that m-alginate/Fe2O3/CdS composite can be used as an effective photocatalyst for the removal of hazardous pollutants such as dyes, and the adsorption-photocatalysis of these organic contaminants in wastewater effluents can s...

Titanium dioxide/zinc oxide/chitosan nanocomposite thin films (TiO2/ZnO/chitosan NTFs) were prepared by entrapping zinc ions and nanosized TiO2 in chitosan thin films under mild conditions. The structure, thermal property, and surface morphology of TiO2/ZnO/chitosan NTFs were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The photocatalytic activity of TiO2/ZnO/chitosan NTFs was evaluated by photocatalytic decolorization of methyl orange in aqueous solution as a model pollutant under simulated solar irradiation. The HRTEM results revealed that well-dispersed and uniform TiO2/ZnO nanocomposite with diameters of 5–15 nm were embedded in chitosan films. The TiO2/ZnO/chitosan NTFs exhibited high photocatalytic activity under simulated solar irradiation. After 4 h of irradiation by simulated solar light, over 97% of methyl orange solution (15 mg L− 1) was decolorized with 0.5 g L− 1 of the photocatalyst. The TiO2/ZnO/chitosan NTFs could be reused, which meant that the adsorption-photocatalytic decolorization process could be operated at a relatively low cost. Since this process does not require the addition of hydrogen peroxide and uses solar light, it can be developed as an economically feasible and environmentally friendly method to decolorize or treat dye wastewater using sunlight.

Cadmium sulfide (CdS) semiconducting quantum dots (QDs) were prepared using in situ synthesizing method in crosslinked chitosan hydrogel films under relative mild experimental conditions and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results confirmed that crosslinked chitosan hydrogel films provided a confined matrix for CdS QDs growth in uniform size through chelation and electrostation between cadmium ions and amino groups in chitosan chains. The CdS QDs/chitosan composite films exhibited a highly efficient photocatalytic activity for decolorization of methyl orange (MO) solution under visible light irradiation. The good linearity relationship between ln ( C 0 / C i ) and irradiation time ( t ) indicated that the decolorization of MO dye under present experimental conditions followed pseudo-first-order kinetics. These results suggested that CdS QDs/chitosan composite films were suitable material for potential application in decolorization of organic dye pollutants under visible light irradiation.

Batch experiments were carried out to study the effects of various inorganic anions on the photocatalytic decolorisation of an azo dye (CI Methyl Orange 13025) in the aqueous phase in the presence of cadmium sulphide/polymer nanocomposite films under visible light irradiation. When anion concentrations were low (0.001 m), the inhibition effect on the photocatalytic decolorisation of CI Methyl Orange 13025 caused by these anions was ranked as . The presence of both and baffled the breakage of the benzene ring in the chemical structure of CI Methyl Orange 13025, while the presence of was of benefit to the degradation of the benzene ring. Adsorption experiments indicated that inorganic anions affected the decolorisation of CI Methyl Orange 13025 by competitive adsorption onto the surface of the photocatalyst. The photocatalytic decolorisation of CI Methyl Orange 13025 followed the pseudo-first-order kinetic reaction model well in all experimental cases.

CdS/TiO 2 nanocomposites were prepared via a simple wet chemical method, and characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their ability to degrade Acid Rhodamine B was investigated under visible light irradiation. The results indicate that CdS/TiO 2 nanocomposite with a mass ratio of 4:1(TiO 2 :CdS) showed high photocatalytic activity and the CdS loaded on TiO 2 nanotube surface exhibited a hexagonal phase. The dispersion of CdS on TiO 2 nanotube surface had an important effect on the degradation efficiency of pollutant, which provides a strategy for practical industry application.

SnO2/CuO/polymer flexible thin films were prepared by a solution casting technology and characterized by high-resolution TEM and XRD. The influences of key operational parameters on photocatalytic decolorization of azo dye (Biebrich Scarlet Red, BSR) were investigated systematically. The results showed good crystalline and clear lattice spacings of the novel composite photocatalyst. BSR was bleached effectively and the decolorization efficiency was >98 % in the presence of 1.0 g L–1 photocatalyst under simulated solar light irradiation. The decolorization was more effective in acidic solution with the optimal pH in the range of 4–6. The tested co-anions in general decreased the decolorization rates by decreasing the adsorption of BSR on the surface of the photocatalyst and reacting with positive hole (h+)/hydroxyl radicals (HO·).

Activated carbon/nanosized CdS/chitosan (AC/n-CdS/CS) composites as adsorbent and photoactive catalyst were prepared under low temperature (≤60 °C) and ambient pressure. Methyl orange (MO) was chosen as a model pollutant to evaluate synergistic effect of adsorption and photocatalytic decolorization by this innovative photocatalyst under visible light irradiation. Effects of various parameters such as catalyst amount, initial MO concentration, solution pH and reuse of catalyst on the decolorization of MO were investigated to optimize operational conditions. The decolorization of MO catalyzed by AC/n-CdS/CS fits the Langmuir-Hinshelwood kinetics model, and a surface reaction, where the dyes are absorbed, is the controlling step of the process. Decolorization efficiency of MO is improved with the increase in catalyst amount within a certain range. The photodecolorization of MO is more efficient in acidic media than alkaline media. The decolorization efficiency of MO is still higher than 84% after five cycles and 60 min under visible light irradiation, which confirms the reusability of AC/n-CdS/CS composite catalyst.

The crosslinked chitosan/nano-CdS (CS/n-CdS) composite catalyst prepared by simulating biomineralization process was extensively characterized by FT-IR spectra, XRD, SEM, TEM and TGA. An azo dye, Congo Red (CR), was used as model pollutant to study its photocatalytic activity under visible light irradiation. The influences of catalyst amount, initial CR concentrations, pH of the reaction solution and different anions on CR decolorization and degradation reaction kinetics were investigated. Results of characterization indicated the successful formation of hexagonal phase of CdS on raw chitosan under mild conditions. The photocatalytic degradation was found to follow a pseudo-first-order kinetics according to Langmuir–Hinshelwood (L–H) model. The dye could be decolorized more efficiently in acidic media than alkaline media. The presence of NO3 − accelerated evidently the degradation of CR, while the other chosen anions (Br− ,S O 4 2− and Cl−) had an inhibitory effect on the decolorization of CR, of which the inhibitory effect of Cl − was the most pronounced. UV–vis spectra were analyzed to indicate that degradation of CR in the solution was the break up of the N N bonds and degradation of aromatic fragment in this reaction system. The recycling experiments confirmed the relative stability of the catalyst. © 2009 Elsevier B.V. All rights reserved.