碳酸镉转化制备氢氧化镉及产物光催化降解性

用碳酸钠溶液直接混合硫酸镉溶液制备了沉淀碳酸镉,再以沉淀碳酸镉为基体,氢氧化钠溶液为转化剂,通过阴离子交换制备出氢氧化镉纳米材料。采用X射线衍射仪(XRD)和场发射扫描电子显微镜(FESEM)对沉淀碳酸镉和转化产物的结构和形貌进行了表征。结果表明,沉淀碳酸镉的结构遭到破坏,转化完全所得到的氢氧化镉的形貌完全不同于沉淀碳酸镉,为片状组装的不规则球体。紫外光照射下光催化降解罗丹明B染料测试表明,转化产物比沉淀碳酸镉具有更好的光催化降解性能,转化时间不同的产物表现出不同的降解效率。当20 mg的转化产物分散到50 mL 8 mg/L的罗丹明B染料中,在黑暗环境中磁力搅拌吸附120 min达吸附平衡,开启300 W紫外汞灯后,效率最高的转化产物可在180 min内将染料完全降解。

天然炭纤维负载二氧化钛颗粒的制备与光催化活性

以棉花制备的炭纤维为载体,钛酸丁酯为钛源,采用水热法制备炭纤维负载二氧化钛复合材料(CF/Ti O2),利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对CF/Ti O2复合材料进行结构表征。用紫外-可见光吸收光谱(UV-vis)分析比较了Ti O2、炭纤维和CF/Ti O2,热处理温度以及溶液的p H值在紫外光照下对甲基蓝溶液的光催化降解性的影响,以及对CF/Ti O2复合材料的失活性能研究。结果表明:炭纤维负载Ti O2对甲基蓝光催化降解性较好,有效利用了炭纤维的吸附性与Ti O2的催化活性;当热处理温度为220℃,p H=5时,甲基蓝溶液的吸附-光催化性能最大为85.9%;复合光催化剂使用后在紫外线照射后,其活性恢复,可以循环利用。

Synthesis and highly efficient photocatalytic activity of mixed oxides derived from ZnNiAl layered double hydroxides

ZnO/NiO/ZnAl2O4 mixed-metal oxides were successfully synthesized through a hydrotalcite-like precursor route, in which appropriate amounts of metal salts solutions were mixed to obtain a new series of ZnNiAl layered double hydroxides（LDHs） as precursors, followed by calcination under different temperatures. The as-obtained samples were characterized by SEM, HRTEM, TEM, XRD, BET, TG-DTA, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange（MO） under the simulated sunlight irradiation. The effects of Zn/Ni/Al mole ratio and calcination temperature on the composition, morphology and photocatalytic activity of the samples were investigated in detail. The results indicated that compared with ZnNiAl-LDHs, the mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum of 97.3% photocatalytic decoloration rate within 60 min was achieved from the LDH with the Zn/Ni/Al mole ratio of 2：1：1 and the calcination temperature of 500 ℃, which much exceeded that of Degussa P25 under the same conditions. The possible mechanism of photocatalytic degradation over ZnO/NiO/ZnAl2O4 was discussed.

Preparation, Characterization, Photocatalytic Activity of S and Ag co-Doped Mesoporous Titania Photocatalysts

In order to improve the photocatalytic performance of mesoporous titania under visible light, a series of photocatalysts of S and Ag co-doped mesoporous titania have been successfully prepared by template method using thiourea, AgNO3 and tetrabutyl titanate as precursors and Pluronic P123 （EO20PO70EO20） as template. Scanning electron microscopy （SEM）, X-ray diffraction （XRD）, nitrogen adsorption-desorption measurements, and UV-visible spectroscopy （UV-Vis） were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The microcrystal of the photocatalysts consisted of anatase phase and was approximately present in the form of spherical particle. The photocatalytic performance was studied by photodegradation methyl orange （MO） in water under UV and visible light irradiation. The calcination temperature and the doping content influenced the photoactivity. In addition, the possibility of cyclic usage of co-doped mesoporous titania was also confirmed, the photocatalytic activity of mesoporous titania remained above 89% of that of the fresh sample after being used four times. It was shown that the co-doped mesoporous titania could be activated by visible light and could thus be potentially applied for the treatment of water contaminated by organic pollutants. The synergistic effect of sulfur and silver co-doping played an important role in improving the photocatalytic activity.

Enhanced performance of g-C_3N_4/TiO_2 photocatalysts for degradation of organic pollutants under visible light

Photocatalytic degradation is one of the most promising remediation technologies in terms of advanced oxidation processes(AOPs) for water treatment. In this study, novel graphitic carbon nitride/titanium dioxide(gC3N4/Ti O2) composites were synthesized by a facile sonication method. The physicochemical properties of the photocatalyst with different mass ratios of g-C3N4 to Ti O2 were investigated by X-ray diffraction(XRD), scanning electron microscope(SEM), transmission electron microscopy(TEM), N2 sorption, Fourier transform infrared spectroscopy(FT-IR), X-ray photoelectron spectroscopy(XPS), and UV–vis DRS. The photocatalytic performances were evaluated by degradation of methylene blue. It was found that g-C3N4/Ti O2 with a mass ratio of 1.5:1 exhibited the best degradation performance. Under UV, the degradation rate of g-C3N4/Ti O2 was 6.92 and 2.65 times higher than g-C3N4 and Ti O2, respectively. While under visible light, the enhancement factors became 9.27(to g-C3N4) and 7.03(to Ti O2). The improved photocatalytic activity was ascribed to the interfacial charge transfer between g-C3N4 and Ti O2. This work suggests that hybridization can produce promising solar materials for environmental remediation.

High-humidity tolerance of porous TiO2(B)microspheres in photo thermal catalytic removal of NOx

Semiconductor oxides are widely used to achieve photocatalytic removal of NOx(NO and NO2) species. These materials also exhibit enhanced oxidation ability in thermally assisted photocatalysis;however, many of them tend to be deactivated at high relative humidity(RH) levels. In the case of the benchmark P25 TiO2 photocatalyst, we observe a significant decrease in non-NO2 selectivity from 95.02% to 58.33% when RH increases from 20% to 80%. Interestingly, the porous TiO2(B) microspheres synthesized in this work exhibit 99% selectivity at 20% RH;the selectivity remains as high as 96.18% at 80% RH. The high humidity tolerance of the TiO2(B) sample can be ascribed to its strong water desorption capacity and easy O2 adsorption at elevated temperatures, which reflects the fact that the superoxide radical is the main active species for the deep oxidation of NOx. This work may inspire the design of efficient photothermal catalysts with application in NOx removal in hot and humid environments.

Design of metal-organic frameworks(MOFs)-based photocatalyst for solar fuel production and photo-degradation of pollutants

Metal organic frameworks(MOFs)is a research hotspot in the solar fuel production and photo-degradation of pollutants field due to high surface area,rich metal/organic species,large pore volume,and adjustability of structures and compositions.Therefore,in this review,we first summarized the design factors of photocatalytic materials based on MOF from the perspective of"star"MOF.The modification strategies of MOFs-based photocatalysts were discussed to improve its photocatalytic activity and specific applications were summarized as well,including photocatalytic CO_(2)reduction,photocatalytic water splitting and photo-degradation of pollutants.Finally,the advantages and disadvantages of MOFs-based photocatalysts were discussed,the current challenges were highlighted,and suggestions for future research directions were proposed.

Preparation of TiO_2/SiO_2 Aerogels by Non-supercritical Drying Method and Their Photocatalytic Activity for Degradation of Pyridine

TiO2/SiO2 aerogels with different molar ratio of SiO2/TiO2 were prepared via non-supercritical method using tetrabutyl titanate and silica sols as raw materials. The samples were characterized by TEM, SEM, BET, IR, XRD and so on. The results indicate that the BET surface area of TiO2/SiO2 aerogels calcined at 550℃ which consisted of anatase structure of TiO2 with narrow distribution pores of 5-25 nm is as high as 357.89 m2·g-1. For the photocatalytic degradation of pyridine, the catalytic activities of TiO2/SiO2 aerogels are much higher than that of TiO2 powder. The photocatalytic activity of TiO2/SiO2 aerogels calcined at 800℃ is the optimum. The higher the content of SiO2, the higher the photocatalytic activity of TiO2/SiO2 aerogels. The cost for preparation of the aerogels is greatly reduced by using non-supercritical drying method, and the aerogels are hopefully applied in the treatment of industrial waste water such as coking effluent treatment.

Photocatalytic degradation of textile dyeing wastewater through microwave synthesized Zr-AC,Ni-AC and Zn-AC

The novel zirconium oxide, nickel oxide and zinc oxide nanoparticles supported activated carbons（Zr-AC, Ni-AC, Zn-AC） were successfully fabricated through microwave irradiation method. The synthesized nanoparticles were characterized using XRD, HR-SEM, XPS and BET. The optical properties of Zr-AC, Ni-AC and Zn-AC composites were investigated using UV–Vis diffuse reflectance spectroscopy. The photocatalytic efficiency was verified in the degradation of textile dyeing wastewater（TDW） in UV light irradiation. The chemical oxygen demand（COD） of TDW was observed at regular intervals to calculate the removal rate of COD. Zn-AC composites showed impressive photocatalytic enrichment, which can be ascribed to the enhanced absorbance in the UV light region, the effective adsorptive capacity to dye molecules, the assisted charge transfer and the inhibited recombination of electron-hole pairs. The maximum TDW degradation（82% COD removal） was achieved with Zn-AC. A possible synergy mechanism on the surface of Zn-AC was also designed. Zn-AC could be reused five times without exceptional loss of its activity.

Photocatalytic degradation of dyes by AgBr/Ag_3PO_4 and the ecotoxicities of their degraded products

Ag3PO4 powders were prepared through a precipitation reaction between AgNO3 and precipitating agent solutions that were prepared by adjusting the amount of H3PO4 in the Na3PO4 solutions. The Ag3PO4 powders prepared from the precipitation solution with a pH of 6 showed the highest photocatalytic activity for decolorizing the methylene blue and rhodamine B dyes. These Ag3PO4 powders were further modified by the addition of KBr solutions to obtain AgBr/Ag3PO4 powders and these photocatalysts can decolorize the anionic dyes as reactive orange and methyl orange. The reactive species involved in the photocatalytic degradation process were evaluated for their inhibitory activity using the appropriate scavengers. After photocatalysis, mass spectrometry confirmed that the dyes were degraded to smaller molecules. The ecotoxicities of the dye solutions before and after treatment were evaluated by studying their ability to inhibit the growth of the bioindicator Chlorella vulgaris.

Synthesis and Photocatalytic Activity of One-dimensional ZnO-Zn2SnO4 Mixed Oxide Nanowires

Mixed oxide photocatalysts, ZnO-Zn2SnO4 （ZnO-ZTO） nanowires with different sizes were prepared by a simple thermal evaporation method. The ZnO-ZTO nanowires were characterized with a scanning electron microscope, X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectrom- eter, and X-ray photoelectron spectra. The photocatalytic activity of the ZnO-ZTO mixed nanowires were studied by observing the photodegradation behaviors of methyl orange aqueous solution. The results suggest that the ZnO-ZTO mixed oxide nanowires have a higher photocatalytic activity than pure ZnO and Zn2SnO4 nanowires. The photocatalyst concentration in the solution distinctly affects the degradation rate, and our results show that higher photodegradation efficiency can be achieved with a smaller amount of ZnO-ZTO nanowire catalyst, as compared to the pure ZnO and ZTO nanowires. Moreover, the photocatalytic activity can also be enhanced by reducing the average diameter of the nanowires. The activity of pure ZnO and ZTO nanowires are also enhanced by physically mixing them. These results can be explained by the synergism between the two semiconductors.

Photocatalytic degradation of 2,4-dichlorophenol with V_2O_5-TiO_2 catalysts: Effect of catalyst support and surfactant additives

Binary oxide catalysts with various weight percentage V2O5 loadings were prepared by solid‐state dispersion and the nanocomposites were modified with surfactants. The catalysts were analyzed using X‐ray diffraction, diffuse‐reflectance spectroscopy, Fourier‐transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption‐desorption. The photocatalytic activities of the catalysts were evaluated in the degradation of 2,4‐dichlorophenol under ultraviolet irradiation. The photocatalytic activity of 50 wt%V2O5‐TiO2 （50V2O5‐TiO2） was higher than those of pure V2O5, TiO2, and P25. Interactions between V2O5 and TiO2 affected the photocatalytic efficiencies of the binary oxide catalysts. Cetyltrimethylammonium bromide （CTAB） and hexadecyltrimethylammonium bromide （HTAB） significantly enhanced the efficiency of the 50V2O5‐TiO2 catalyst. The highest per‐centage of 2,4‐dichlorophenol degradation （100%） and highest reaction rate （2.22 mg/（L·min）） were obtained in 30 min with the （50V2O5‐TiO2）‐CTAB catalyst. It is concluded that the addition of a surfactant to the binary oxide significantly enhanced the photocatalytic activity by modifying the optical and electronic properties of V2O5 and TiO2.

High photocatalytic activities of zinc oxide nanotube arrays modified with tungsten trioxide nanoparticles

Well‐aligned zinc oxide(ZnO)nanotube arrays loaded with tungsten trioxide(WO3)nanoparticles were synthesized by a process involving chemical bath deposition in combination with pyrolysis.The prepared ZnO–WO3composites were characterized by X‐ray diffraction,energy dispersive spectrometer,field emission scanning electron microscopy,X‐ray photoelectron spectroscopy,photoluminescence spectroscopy,Fourier transform infrared spectroscopy and UV–vis diffuse reflectance spectroscopy.The photocatalytic activities of the ZnO–WO3composite photocatalysts with different WO3contents for the degradation of the herbicide chlorinated phenoxyacetic acid(MCPA‐Na)under simulated sunlight irradiation were systematically evaluated.It was found that the WO3content had a great effect on the photocatalytic activity of the ZnO–WO3composites.The composite with3%WO3showed the highest photocatalytic activity,with a degradation rate of chlorinated phenoxyacetic acid of98.5%after200min with20mg of photocatalyst.This photodegradation rate was about twice that of the pristine ZnO nanotube array.The recombination of photogenerated electrons and holes was increasingly suppressed with the addition of WO3to ZnO.The high relative content of defects on the surface of the ZnO–WO3composites was beneficial to their photocatalytic activity in the degradation of chlorinated phenoxyacetic acid.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

Preparation and photocatalytic performance of ZnO/ZnGa_2O_4 composite microspheres

ZnO/ZnGa_2O_4 composite microspheres with heterojunction were successfully synthesized by one-pot hydrothermal method.These samples were characterized by TG/DTA,XRD,TEM,HRTEM,UV-vis DRS,FL and BET techniques.The results indicated the as-prepared samples showed better degree of crystalline and large specific surface area.The photocatalytic activity was evaluated by degradation of methyl orange with the concentration of 50 mg/L under the irradiation of simulated sunlight.The effects of molar ratio of Zn to Ga and calcination temperature on the photocatalytic activity were investigated in detail.The results showed that the highest photocatalytic degradation efficiency was observed at the molar ratio of Zn to Ga of 1:0.5 in the starting materials and the calcination temperature of 400 °C.The maximum photocatalytic degradation rate of MO was 97.1% within 60 min under the simulated sunlight irradiation,which is greatly higher than that of ZnO and ZnGa_2O_4.

Effect of Dispersity and Porous Structure of TiO2 Nanopowders on Photocatalytic Destruction of Azodyes in Aqueous Solutions

Photocatalytic activity of TiO2 nanopowders of anatase modification with various particle sizes and specific surface areas has been studied in the process of photocatalytic decolorization of aqueous solutions of methylene blue and direct blue 2C azodyes. By means of scanning electron microscopy and low-temperature N2 adsorption method, it was found that TiO2 nanopowders have the particles size of 5-120 nm with the specific surface area of 15-120 m2·g^-1. The used TiO2 samples are characterized by mesoporous structures with average pore size of 4.3-14.9 nm. The photocatalytic activity of TiO2 was evaluated via decolorization of azodyes solutions. It was shown that the efficiency of decolorization symbatically changes with the dye adsorption value on TiO2 surface and the degree of decolorization rises when the surface area of TiO2 nanopowders increases. It was found that TiO2 photocatalytic activity essentially depends on adsorption interactions between the dye molecules and catalytic active centers on TiO2 surface, and these interactions, in turn, are greatly affected by pH of the solution.

Optimization of Preparation Conditions of ZnO-TiO2 Nanoparticles by Sol-Gel Technique for Photodegradation Indigo Carmine

The results of a laboratory-scale study of an environmentally friendly water treatment method are presented, where the dyes in the industrial textile wastewater were removed by photocatalytic process. ZnO-TiO2 nanoparticles as photocatalyst has been prepared via sol-gel technique. Several factors were studied in order to find the conditions that could be used to synthesize this photocatalyst for optimum degradation of Indigo Carmine dye in aqueous solutions. The optimum condition for preparation of ZnO-TiO2 mixed oxide are 1.5 TiO2/ZnO, 4 C2HsOH/TIP, 4 H20/TIP, 0.3 HNO3/TIP molar ratios, without aging, 550 ℃ calcination temperature for 5 hrs at which the surface area and the photocatalytic activity are 186.1 m^2/g and 96.1, respectively. Generally, the photocatalytic activity of the samples prepared by sol-gel technique is the highest activity. Details of the synthesis procedure and results of the characterization studies of the produced xerogel are presented in this paper.

Efficient degradation of methyl orange via multilayer films of titanium dioxide and silicotungstic acid

We report layer-by-layer （LbL） assembly of TiO2 and H4SiW12O40 （SiW12） multilayer film on silicon wafers and glass slides for photocatalytic degradation of methyl orange （MO）. The photocatalytic efficiency of the obtained multilayer film increases along with the decrease of pH and salt concentration of the incubation solution. The results show that MO can be almost re- moved in pH 2.0 solution without salt addition in the first 60 min incubation when MO concentration is lower than 15 mg/L. Different salts show an apparent inhibitory effect on photocatalytic degradation of MO with the order of ZnC12〉KCI〉 NaC1〉LiCI. The TiO2/SiW12 multilayer film maintains photocatalytic activity even after five degradation cycles. The reaction of MO photodegradation accords with an apparent first-order dynamics.

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.

PbCrO_4 yellow-pigment nanorods: An efficient and stable visible-light-active photocatalyst for O_2 evolution and photodegradation

Here, PbCrO4 nanorods, a commonly used and low-cost yellow pigment, was synthesized via a simple pre-cipitation reaction and can serve as a highly efficient oxygen production and photodegradation photocatalyst. The obtained PbCrO4 nanorods exhibit excellent stability and pho-tocatalytic performance for O2 evolution from water. The production rate is approximately 314.0μmol h^-1 g^-1 under visible light, and the quantum efficiency is approximately 2.16% at 420±10 nm and 0.05% at 600±10 nm. In addition, the PhCrO4 shows good degradation performance for methylene blue, methyl blue, methyl orange and phenol under visible-light irradiation. These results indicate that it is potential to fabricate an effective, robust PbCrO4 photocatalyst by trans-forming heavy-metal pollutants Pb（II） and Cr（VI） into a highly efficient O2 evolution and photodegradation material. This strategy which uses pollutant to produce clean energy and degrade contaminants is completely green and environmentally benign, and thus could be a promising way for practical environmental applications. Keywords： 02 evolution, pollutant, PbCrO4 nanorods, visible-light-active, photocatalyst