Deriving Ag_3PO_4–CaO composite as a stable and solar light photocatalyst for efficient ammonia degradation from wastewater

A novel Ag3PO4-CaO composite photocatalyst with enhanced photocatalytic activity was synthesized and utilized for degradation of ammonia from aqueous solution under sunlight. Ag3PO4 was prepared by pre- cipitation method, and the composite of AgjPO4-CaO was prepared via impregnation method. Utilization of eggshell for CaO synthesis provided a cost-effective and environmental friendly way for the hetero- geneous catalyst production. The as-prepared photocatalysts were characterized by FT-IR, FE-SEM, TEM, EDX, UV-vis and PL Results show that the Ag3PO4-CaO samples have excellent photocatalytic perfor- mances in the wide visible-light region. The effect of operating parameters like the content of Ag3PO4 in composite, initial ammonia concentration, pH of solution, catalyst dosage and oxygen supply was investi- gated. The photoeatalyst with 60 wt% content of Ag3PO4 had a high photocatalytic performance, because a low content of Ag3PO4 causes weak light absorption, and the excess amount of it results in serious electron-hole recombination due to the aggregation of AgjPO4 particles. The maximum ammonia degra- dation （about 70%） was achieved in 340 mg/L of ammonia, pH 11, and 1.25 g/L of catalyst in the presence of pure oxygen. In comparison to Ag3PO4, 60 wt% AgjPO4-CaO had a good stability and it could have been easily separated from the solution for recycling.

Fe/C Modified TiO_2 Photocatalyst and Photodegradation of 4-t-octylphenol

[Objective]The research aimed to study synthesis of the TiO2 photocatalyst modified by Fe/C and photodegradation of 4-t-octylphenol.[Method]Fe/C modified TiO2 photocatalyst was made by sol-gel and solvothermal synthesis methods.4-t-octylphenol as test object,photocatalytic performance of the catalyst was investigated.Influences of the Fe doping amount,catalyst amount,pH and sun-light irradiation on reaction were discussed.Moreover,catalyst performance under the condition of interfering ion existence was studied.[Result]When Fe/C doping amount was 0.6%,under the reaction condition of 25 ℃,pH =9.0,300 W mercury lamp and 1.0 g/L of catalyst amount,4-t-octylphenol concentration decreased from 1.00 to 0.02 mg/L by degradation for 100 min.Rises of pH and light intensity could improve catalyst efficiency.The existences of Na ＋,K ＋ and Ca2＋ had no effect on degradation activity of the catalyst.[Conclusion]Fe/C modified TiO2 photocatalyst had better degradation effect on environmental hormone in the sewage.

Structural and photocatalytic properties of TiO_2 films fabricated on silicon substrates by MOCVD method

Silicon(111) and Silicon(100) were employed for fabrication of TiO 2 films by metal organic chemical vapor deposition(MOCVD). Titanium(IV) isopropoxide(Ti[O(C 3H 7) 4]) was used as a precursor. The as deposited TiO 2 films were characterized with FE\|SEM, XRD and AFM. The photocatalytic properties were investigated by decomposition of aqueous OrangeⅡ. And UV VIS photospectrometer was used for checking the absorption characteristics and photocatalytic degradation activity. The crystalline and structural properties of TiO 2 film had crucial influences on the photodegradation efficiency. For MOCVD in situ deposited films on Si substrates, the photoactivities varied following a shape of “M': at lower(350℃), middle(500℃) and higher(800℃) temperature of deposition, relative lower photodegradation activities were observed. At 400℃ and 700℃ of deposition, relative higher efficiencies of degradation were obtained, because one predominant crystallite orientation could be obtained as deposition at the temperature of two levels, especially a single anatase crystalline TiO 2 film could be obtained at 700℃.

Fabrication and Photocatalytic Characteristics of TiO_2 Films on Silicon Substrates

Silicon (111) and Silicon (100) have been employed for fabrication of TiO_2films by metal organic chemical vapor deposition (MOCVD). Titanium (IV) isopropoxide (Ti[O(C_3H_7)_4]) was used as a precursor. The as-deposited TiO_2 films have been characterized withField emission scanning electron microscopy (FE-SEM), X ray diffraction (XRD) and atomic forcemicroscopy (AFM). The photocatalytic properties were investigated by decomposition of aqueous orangeII. The crystalline and structural propertiesof TiO_2 film had crucial influences on thephotodegradation efficiency. For MOCVD in-situ deposited films on Si substrates, the photoactivitiesvaried following a shape of 'M': At lower (350 °C ) middle (500 °C) and higher (800 °C)temperature of deposition, relative lower photodegradation activities have been observed. At 400 °Cand 700 'C of deposition, relative higher efficiencies of degradation have been obtained, becauseone predominant crystallite orientation could be obtained as deposition at those two temperatures,especially a single anatase crystalline TiO_2 film could be obtained at 700 °C growth.

Photocatalytic Activity of Porous Magnesium Oxychloride Cement Combined with AC/TiO2 Composites

As a decorative material, magnesium oxychloride cement was used as a photocatalyst supporter to purify the pollutants indoors. Due to excellent adsorption properties of activated carbon（AC）, the photocatalytic composties, TiO2/AC, were prepared and introduced into the porous magnesium oxychloride cement（PMOC） substrate to composite a sort of photocatalytic cementitious material（PCM）. The optimal composite processes were assessed by gas chromatograph, using toluene as the target. By comparing the perspective of toluene purification and thorough decomposition, it can be found that the optimal mass ratio for TiO2/AC composites is 4/25, and the heat treatment to TiO2/AC sample at 350 ℃ can play the optimal synergetic role of adsorbents in photocatalytic process. The synergistic effect of TiO2, AC and magnesium oxychloride cement（MOC） was also evaluated by gas chromatograph. One-take molding process was adopted to introduce the TiO2/AC into PMOC substrate, and its optimal mass fraction was 4 wt%, while the appropriate density of substrate was 0.35 g/cm3. Toluene degradation showed that the prepared PCM can degrade pollutants efficiently. The appropriate treatment process of TiO2/AC, mass of TiO2/AC, substrate density, and stable pore structure should be coordinated to maximize the adsorption-photodegradation performance. The combination of photocatalytic materials, adsorbents, and building materials provided a new idea for the application of photocatalysis.

Ultrasonic-assisted synthesis of plasmonic Z-scheme Ag/AgCl/WO_3-nanoflakes photocatalyst in geothermal water with enhanced visible-light photocatalytic performance

In this study, the Ag/Ag Cl/WO3 plasmonic Z-scheme photocatalysts with different contents of Ag/Ag Cl nanoparticles（NPs） were prepared through a facile ultrasonic precipitation method in geothermal water,wherein the geothermal water served as the chlorine source. Then the photocatalytic activity was investigated by degradation of 4-Aminobenzoic acid（4-ABA） under visible-light irradiation. It was found that the as-prepared 50 wt% Ag/Ag Cl/WO3 photocatalyst showed the highest photocatalytic efficiency with 25.12 and 3.53 times higher than those of pure WO3 and Ag/Ag Cl, respectively. The active species trapping experiments indicated that h＋and ·O2-were key factors in 4-ABA photodegradation process. The possible plasmonic Z-scheme photocatalytic mechanism of photocatalytic reaction for 4-ABA degradation was proposed based on systematical characterizations. We hope this paper could give new ideas for further exploiting geothermal energy to design and fabricate highly efficient visible-light-driven photocatalysts for environmental remediation.

Internalization of Foreign Ions into Meta-stable Lattices:a Case Study of Transition-metal-doped Brookite

The connections between the building units of meta-stable lattice were generally considered to be easily disturbed during the doping process, causing serious hindrances blocking the development of functional doped materials. In this work, the synthesis of doped brookite, a typical meta-stable phase of TiO2, has been explored novelly by in-situ adding of cations of VIIIB and IB,IIB elements in the 3rd period（Fe, Co, Ni, Cu, Zn） during the urea-lactate aided low-basicity hydrothermal process. The results showed that only Cu-doped brookite could be successfully synthesized with trace amount of copper intensively internalized into the brookite lattice, while the other dopants lead to the formation of anatase TiO2. Extensive characterizations indicated a two-step doping process, where copper ions were firstly dispersed in an amorphous layer on the lattice surface and then they were internalized into brookite lattice. Cu-doped brookite exhibited significantly enhanced photocatalytic activity in the phenol degradation under visible light compared to bare brookite. The enhancement of catalytic performance was assigned to the impurity band gap and the reduction of charge carriers＇ recombination introduced by the internalization of Cu ions. The investigation reported herein contributes to the understanding of complex ion-doping effects on the structures of meta-stable materials, and provides hints for obtaining other functional doped materials.

Synthesis,characterization and application of ZnO-Ag as a nanophotocatalyst for organic compounds degradation,mechanism and economic study

The current work deals with ZnO-Ag nanocomposites（in the wide range of x in the Zn1-x O-Ag x chemical composition） synthesized using microwave assisted solution combustion method.The structural, morphological and optical properties of the samples were characterized by XRD（X-ray diffraction）, FTIR（Fourier transform infrared spectrometry）, SEM（scanning electron microscopy technique）, EDX（energy dispersive X-ray spectrum）, ICP（inductively coupled plasma technique）, TEM（transmission electron microscopy）, BET（Brunauer–Emmett–Teller method）, UV–Vis（ultraviolet–visible spectrophotometer） and photoluminescence spectrophotometer. The photocatalytic activity of the ZnO-Ag was investigated by photo-degradation of Acid Blue 113（AB 113） under UV illumination in a semi-batch reactor. This experiment showed that ZnO-Ag has much more excellent photocatalytic properties than ZnO synthesized by the same method. The enhanced photocatalytic activity was due to the decrease in recombination of photogenerated electron-holes. The results showed the improvement of ZnO photocatalytic activity and there is an optimum amount of Ag（3.5 mol%） that needs to be doped with ZnO.The effect of operating parameters such as p H, catalyst dose and dye concentration were investigated. The reaction byproducts were identified by LC/MS（liquid chromatography/mass spectrometry） analysis and a pathway was proposed as well. Kinetic studies indicated that the decolorization process follows the first order kinetics. Also, the degradation percentage of AB113 was determined using a total organic carbon（TOC） analyzer. Additionally, cost analysis of the process, the mechanism and the role of Ag were discussed.

ZnO nanopowders and their excellent solar light/UV photocatalytic activity on degradation of dye in wastewater

Low-cost and scalable preparation,high photocatalytic activity,and convenient recycle of Zn O nanopowders(NPs)would determine their practical application in purifying wastewater.In this contribution,ZnO NPs were scalably synthesized via the simple reaction of Zn powder with H_2O vapor in autoclave.The structural,morphological and optical properties of the samples were systematically characterized by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectra,transmission electron microscopy,Micro-Raman,photoluminescence,and ultraviolet-visible spectroscopy.The as-prepared Zn O NPs are composed of nanoparticles with 100–150 nm in diameter,and have a small Brunauer-Emmett-Teller surface area of 6.85 m^2/g.The formation of Zn O nanoparticles is relative to the peeling of H_2 release.Furthermore,the product has big strain-stress leading to the red-shift in the band gap of product,and shows a strong green emission centered at 515 nm revealing enough atomic defects in Zn O NPs.As a comparison with P25,the obtained dust gray Zn O NPs have a strong absorbance in the region of 200–700 nm,suggesting the wide wave-band utilization in sunlight.Based on the traits above,the Zn O NPs show excellent photocatalytic activity on the degradation of rhodamine B(Rh-B)under solar light irradiation,close to that under UV irradiation.Importantly,the Zn O NPs could be well recycled in water due to the quick sedimentation in themselves in solution.The low-cost and scalable preparation,high photocatalytic activity,and convenient recycle of Zn O NPs endow themselves with promising application in purifying wastewater.