Determination of hydroxyl radicals in TiO2/Ti photoelectrocatalytic oxidation system using Fe(phen)3 2+ spectrophotometry

A new method of determining the cumulate concentration of hydroxyl radicals in the TiO₂/Ti photoelectrocatalytic(PEC)oxidation system was established by o-phenanthroline-Fe(Ⅱ)(Fe(phen)₃²⁺) spectrophotometry and using anion     

Photocatalytic degradation of organochlorine compounds using TiO2 supported on fiberglass cloth

The feasibility of photocatalytic degradation of organochlorine compounds using TiO₂ supported on fiberglass cloth as a photocatalyst was studied. The results showed that 2.0×10^-4 mol/dm³ of dichloroethylene, trichloroethylene and tetrachloroethylene can be completely photocatalytically degraded within a short time under illumination with a 375W medium pressure mercury lamp. The effects of parameters such as illumination time, initial concentration of organochlorine compounds, amount of air flow and concentration of H₂O₂ on the photocatalytic degradation were investigated. The TiO₂ supported on the fiberglass was not easily detached and after 500h illumination there was no significant loss of photocatalytic activity of TiO₂. The passible mechanisms of photocatalytic degradation were discussed.     

Photocatalytic degradation of phenanthrene on soil surfaces in the presence of nanometer anatase TiO2 under UV-light

The effect of nanometer anatase TiO₂ was investigated on the photocatalytic degradation of phenanthrene on soil surfaces under a variety of conditions. After being spiked with phenanthrene, soil samples loaded with different amounts of TiO₂ (0 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, and 4 wt.%) were exposed to UV-light irradiation for 25 hr. The results indicated that the photocatalytic degradation of phenanthrene followed the pseudo first-order kinetics. TiO₂ significantly accelerated the degradation of phenanthrene with the half-life reduced from 45.90 to 31.36 hr for TiO₂ loading of 0 wt.% and 4 wt.%, respectively. In addition, the effects of H₂O₂, light intensity and humic acid on the degradation of phenanthrene were investigated. The degradation of phenanthrene increased with the concentration of H₂O₂, light intensity and the concentration of humic acids. It has been demonstrated that the photocatalytic method in the presence of nanometer anatase TiO₂ was a very promising technology for the treatments of soil polluted with organic substances in the future.     

Photocatalytic degradation of C. I. Reactive Red 24 solution with K6SiW11O39SnⅡ

Environmental friendly materials, K₆SiW₁₁O₃₉Sn (SiWSn), was synthesized. SiWSn photocatalytic decomposition of C. I. Reactive Red 24 (RR24) with the UV-lamp (253.7 nm, 20 W), Xenon lamp filtered less than 390 nm light (500 W) and sun light was investigated. The results showed that RR24 solution could be effectively decolorized with the SiWSn photocatalyst. The photocatalytic degradation efficiency of RR24 with SiWSn was affected by the initial concentration of RR2 solution, the amount of SiWSn and the photolysis time. It is demonstrated that the process of photodegradation of RR24 with SiWSn is a pesudo first-order reaction, which can be described by Langmuir-Hinshelwood equation. Hydroxyl radicals and holes are both the main oxidants in the photocatalytic reaction of RR24 with SiWSn.     

Photocatalytic degradation of dichlorvos using TiO2 supported on hollow glass microbeads

In this paper, a method for TiO₂ supported on hollow glass microbeads was described and the feasibility of photocatalytic degradation of dichlorvos using supported TiO₂(TiO₂/beads) was studied. The results showed that 1.0×10^-4 mol.dm^-3 of dichlovos could be completely photocatalytically degraded into PO₄^3- after 120 min illumination with a 375 W medium pressure mercury lamp. The effects of the amount of TiO₂/beads and concentration of Cu²⁺ on the photocatalytic degradation were also investigated. Some intemediate products of photocatalytic degradation of dichlorvos were detected.     

Photoelectrocatalytic degradation of high COD dipterex pesticide by using TiO2/Ni photo electrode

A TiO₂ thin film electrode deposited on porous nickel net (TiO₂/Ni) was prepared by the sol-gel method, and the surface morphology, crystal structure features and the grain size were characterized by Field emission scan electron microscopy (FESEM) and X-ray diffraction (XRD). The photoelectrocatalytic system was set up using a UV high-pressure mercury lamp as the light source, TiO₂ coated on foamed nickel as photo anode, Pt sheet as counter electrode and the pesticide dipterex in synthetic wastewater. Various factors that influence the photoelectrocatalytic decomposition of dipterex pesticide have been studied, such as degradation time, the type of electrolyte, current density, original pH value and different degradation methods. The prepared catalysts were employed to photoelectrocatalytically degrade the pesticide dipterex under UV irradiation, comparing the results with photocatalytic degradation and electrochemical oxidation. The results indicated that under the optimal conditions of 0.02 mol/L NaCl as the supporting electrolyte, current density = 2.5 mA/cm², pH 6.0 and dipterex pesticide 40 mg/L, and reaction time 2 hr, dipterex chemical oxygen demand (COD) removal rate and organophosphorous conversion of up to 82.6% and 83.5% were achieved, respectively. The method of photoelectrocatalytic degradation is more efficient than photocatalysis and electrochemical oxidation. The possible roles of the electrolytes on the reactions and probable mechanisms were also discussed.     

Enhanced photoelectrocatalytic decomplexation of Ni-EDTA and simultaneous recovery of metallic nickel via TiO2/Ni-Sb-SnO2 bifunctional photoanode and activated carbon fiber cathode

In order to enhance Ni-EDTA decomplexation and Ni recovery via photoelectrocatalytic (PEC) process, TiO₂/Ni-Sb-SnO₂ bifunctional electrode was fabricated as the photoanode and activated carbon fiber (ACF) was introduced as the cathode. At a cell voltage of 3.5 V and initial solution pH of 6.3, the TiO₂/Ni-Sb-SnO₂ bifunctional photoanode exhibited a synergetic effect on the decomplexation of Ni-EDTA with the pseudo-first-order rate constant of 0.01068 min⁻¹ with 180 min by using stainless steel (SS) cathode, which was 1.5 and 2.4 times higher than that of TiO₂ photoanode and Ni-Sb-SnO₂ anode, respectively. Moreover, both the efficiencies of Ni-EDTA decomplexation and Ni recovery were improved to 98% from 86% and 73% from 41% after replacing SS cathode with ACF cathode, respectively. Influencing factors on Ni-EDTA decomplexation and Ni recovery were investigated and the efficiencies were favored at acidic condition, higher cell voltage and lower initial Ni-EDTA concentration. Ni-EDTA was mainly decomposed via ·OH radicals which generated via the interaction of O₃, H₂O₂, and UV irradiation in the contrasted PEC system. Then, the liberated Ni²⁺ ions which liberated from Ni-EDTA decomplexation were eventually reduced to metallic Ni on the ACF cathode surface. Finally, the stability of the constructed PEC system on Ni-EDTA decomplexation and Ni recovery was exhibited.     

Synthesis and characteristic of polyaniline/Dy2O3 composites：Thermal property and electrochemical performance

A simple route of in situ polymerization by the chemical oxidation method was successfully employed to synthesize polyaniline/dysprosium oxide (PANI/Dy₂O₃) composites. The synthesized materials were characterized by Fourier transform infrared spectra and X-ray diffraction. The thermal stability of the composite was studied by thermogravimetry (TG). The electrochemical performance of the composites was investigated by cyclic voltammetry and alternating current impedance spectroscopy with a three-electrode system. TG results suggested that the thermal stability of PANI/Dy₂O₃ composites showed a tendency to first increase and then decrease with increasing Dy₂O₃ amount. Electrochemical experiments indicated that the composite electrodes showed a lower capacitance than that of pure PANI, which may be attributed to the interaction between PANI and Dy₂O₃ in the composites.     

Radioactive tracer of the photochemical reaction of 14CS2 with OH in the presence of O2

The photochemical reaction of¹⁴CS ₂ with OH has been studied．The results indicated that the main products of the reaction were¹⁴COS and ¹⁴CO with a small amount of ¹⁴CO₂ in the reaction system(¹⁴CS₂-H₂O₂-C₃H₈-N₂-O₂>)．The reaction was promoted by oxygen．¹⁴COS and ¹⁴CO had the similar kinetic curves while ¹⁴CO₂ got a different kind of Curve．The overall rate constant increased with the increasing of oxygen partial pressure．The rate constant for the removal of ¹⁴CS₂ was K=3.4×10^-12cm³/(mO1.s) at 33330 Pa 0₂．The conversion of ¹⁴CS₂ to ¹⁴CO₂ at room temperature was observed and the possible mechanism of the photochemical reaction was disscussed．     

Dielectric barrier discharge plasma-assisted modification of g-C3N4/Ag2O/TiO2-NRs composite enhanced photoelectrocatalytic activity

Dielectric barrier discharge (DBD) plasma applied as surface treatment technology was employed for the modification of Ag₂O and graphitic carbon nitride (g-C₃N₄) powders. Subsequently, the pretreated powders were sequentially loaded onto TiO₂ nanorods (TiO₂-NRs) via electro-deposition, followed by calcination at N₂ atmosphere. The results indicated that at the optimal plasma discharge time of 5 min for modification of g-C₃N₄ and Ag₂O, photocurrent density of ternary composite was 6 times to bare TiO₂-NRs under UV-visible light irradiation. Phenol was degraded by using DBD plasma-modified g-C₃N₄/Ag₂O/TiO₂-NRs electrode to analyze the photoelectrocatalytic performance. The removal rate of phenol for g-C₃N₄-5/Ag₂O-5/TiO₂-NRs electrode was about 3.07 times to that for TiO₂-NRs electrode. During active species scavengers’ analysis, superoxide radicals and hydroxyl radicals were the main oxidation active species for pollutants degradation. A possible electron-hole separation and transfer mechanism of ternary composite with high photoelectrocatalytic performance was proposed.     

Preparation of TiO2/Ti mesh photoelectrode and properties

An innovative photoelectrode,TiO2/Ti mesh electrode,was prepared by anodisation.In anodisation,0.5 mol/L H2SO4 was used as electrolytic solution,the current had been constantly 1A from the beginning of the oxidation until reaching a designed voltage.Results showed that the photocatalytic activity of electrode was better when the designed voltage was 160 V.The morphology and the crystalline texture of the TiO2 film on mesh electrode were examined by scanning electronic microseopy and Raman spectruscopy respectively.The examination results indicated that the structure and properties of the film depended on anodisation rate,and the anatase was the dominant component under the eontrolled experimental conditions.Degradation of Rhodamine B in photocatalytic (PC)and photoelectrocatalytic(PEC) reaction was investigated.     

Photoelectrocatalytic degradation of Rose Bengal

An innovative photoelectrode, TiO2/T1 mesh electrode, was prepared by galvanostaticanodisation. The morphology and the crystalline texture of the TiO2 film on mesh electrode were examined by scanning electronic microscopy and Raman spectroscopy respectively. The examination results indicated that the structure and properties of the film depended on anodisation rate, and the anatase was the dominant component under the controlled experimental conditions. Degradation of Rose Bengal (RB) in photocatalytic (PC) and photoelectrocatalytic (PEC) reaction was investigated, the results demonstrated that electric biasing could improve the efficiency of photecatalytic reaction. The measurement results of TOC in photoelectrocatalytic degradation showed that the mineralisation of RB was complete relatively. The comparison between the degradation efficiency of RB in PEC process and that in aqueous TiO2 dispersion was conducted. The results showed that the apparent first-order rate constant of RB degradation in PEC process was larger than that in aqueous dispersion with 0.1%--0.3% TiO2 powder, but was smaller than that in aaueaus disverslon with 1.0% TiO2.     

Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol(2,4-DCP)was studied in a novel three-electrode photoelectrocatalytic(PEC)integrative oxidation process,and the factors influencing the degradation rate,such as applied current,flow speed of O_2,pH,adscititious voltage and initial 2,4-DCP concentration were investigated and optimized.H_2O_2 was produced nearby cathode and Fe~(2 )continuously generated from Fe anode in solution when current and O_2 were applied,so,main reactions,H_2O_2-assisted TiO_2 PEC oxidation and E-Fenton reaction,occurred during degradation of 2,4-DCP in this integrative system.The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process,while it was only 31% in E-Fenton process and 46% in H_2O_2-assisted TiO_2 PEC process.So,it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect.By the investigation of pH,it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.     

Preparation of TiO_2/Ti mesh photoelectrode and properties

ＩｎｔｒｏｄｕｃｔｉｏｎＭｕｃｈｉｎｖｅｓｔｉｇａｔｉｏｎｓｓｈｏｗｅｄｔｈａｔｐｈｏｔｏｃａｔａｌｙｔｉｃｏｘｉｄａｔｉｏｎｏｆＴｉＯ2 ｐｒｏｖｉｄｅｓａｎｅｆｆｅｃｔｉｖｅｔｅｃｈｎｏｌｏｇｉｃａｌｍｅｔｈｏｄｆｏｒｔｈｅｄｅｇｒａｄａｔｉｏｎｏｆｔｈｅｏｒｇａｎｉｃｃｏｎｔａｍｉｎａｎｔｓｉｎｗａｔｅｒ(Ａｎｄｊｅｌｋａ ,2 0 0 0 ;Ｆｕｊｉｓｈｉｍａ ,1972 ;Ｈｉｄａｋａ ,1992 ;Ｋｅｓｓｅｌｍａｎ ,1997) .Ｉｎｏｒｄｅｒｔｏｏｖｅｒｃｏｍｅｔｈｅｓｈｏｒｔｃｏｍｉｎｇｓｔｈａｔｔｈｅｒｅｃｏｖ…     

TiO2电极光电催化氧化处理水体中的蒽

为了探究光电催化体系对水体中多环芳烃（PAHs）的降解效果,采用TiO₂电极在紫外光照射下进行了光电催化氧化处理多环芳烃——Ant（蒽）的研究.分别比较了光电催化（PEC）、光催化（PC）和电化学氧化（EC）体系对Ant的降解效果.并探究了电流密度、初始pH、初始ρ（Ant）和腐植酸（HA）等对Ant降解效果的影响;同时,采用伪一级动力学对降解反应速率进行了拟合分析并对中间产物的含量及Ant的降解机理进行了研究.结果表明:在相同电流密度和反应时间等条件下,PEC体系对Ant的降解率均高于PC和EO体系;电流密度对Ant降解影响不大,在电流密度为0.05 mA/cm2条件下,反应30 min后,Ant的降解率能达到98.5%,体系中中间产物有蒽酮（AT）、蒽醌（AQ）等物质,其浓度呈现先增加后降低的趋势;初始pH对中间产物AQ的生成影响较大;初始浓度对反应速率影响较大,初始浓度增加3倍,反应速率降低了近44%,但Ant的降解率相差不到1%;HA的存在使得Ant降解率降低了7.5%,反应速率降低了近83%.      

K2S2O8强化g-C3N4薄膜电极光电催化降解Cu(CN)32-并同步回收Cu

采用高温液相生长法制得g-C_3N_4薄膜电极并作为光阳极,以石墨毡作为阴极,建立了光电催化系统.通过对比光电催化体系、K_2S_2O_8体系以及外加K_2S_2O_8到光电催化体系,发现在光电催化系统下外加K_2S_2O_8可以有效地提高光电催化降解Cu(CN)_3~(2-)的效率,并实现了Cu在阴极上的有效回收.探究了K_2S_2O_8投加量对CN-降解率和Cu回收率的影响,发现当K_2S_2O_8浓度为1 mmol·L~(-1),偏压为1.0 V时,CN-的去除率和Cu回收率分别达到86.23%和82.11%.通过SEM、EDS和XPS分析阴阳极表面形貌,发现部分Cu+被氧化以CuO的形式存在于沉淀和阳极表面,大部分铜离子通过电化学还原作用以单质铜的形式沉积于阴极表面,铜离子有效地从体系中去除.电子顺磁共振及淬灭实验分析表明,CN-的氧化去除是硫酸根自由基(SO·-4)氧化和非自由基氧化共同作用.     

电沉积ZnO膜光电催化降解4-硝基酚研究

用硝酸锌水溶液作电解质,采用阴极电沉积法在玻碳电极上制备了具有光电化学活性的氧化锌(ZnO)薄膜。以ZnO膜电极为工作电极对4-硝基酚进行了光电催化降解处理,系统研究了外加偏压、4-硝基酚浓度、电解液浓度以及pH值对4-硝基酚在ZnO膜电极上的光电催化降解效果的影响。结果表明:在外加偏压为1.0V,电解液浓度为0.1mol/L,溶液为近中性条件(pH为6.3)时对0.05mmol/L的4-硝基酚2小时的降解效率达到了98.8%。     

网状Ti/TiO2电极光电催化氧化若丹明B

用阳极氧化法制备出一种网状Ti/TiO₂电极,扫描电镜和拉曼光谱对电极表面TiO₂膜的形貌和晶体结构的检测结果表明:膜的结构和性能受阳极氧化过程中氧化速率的影响,在控制实验条件下,锐钛型TiO₂是其主要结晶形态.若丹明B的光电催化降解和光催化降解的实验结果表明:外加偏压可以有效地提高有机物的光催化降解效率.TOC的测定结果显示,在光电催化氧化过程中,若丹明B几乎完全矿化.若丹明B在光电催化降解过程中,生色基团的破坏与脱乙基作用同时发生.     

Determination of hydroxyl radicals in TiO2/Ti photoelectrocatalytic oxidation system using Fe(phen)3 2+ spectrophotometry

A new method of determining the cumulate concentration of hydroxyl radicals in the TiO2/Ti photoelectrocatalytic(PEC)oxidation system was established by o-phenanthroline-Fe(Ⅱ)(Fe(phen)32+) spectrophotometry and using anion exchange membrane. Fe concentration of hydroxyl radicals can be calculated through determining the change of the Fe(phen)33+ absorbency at 509 nm. In addition, the research results showed the production rate of hydroxyl radicals was affected obviously by pH of solution, the cumulate concentration of hydroxyl radicals was the largest at nearby the initial pH 6.3 (isoelectric point), and the change direction of pH after illumination tended to nearby isoelectric point.     

Photoelectrochemical degradation of Methylene Blue with -PbO2 electrodes driven by visible light irradiation

-PbO2 electrodes were prepared by electro-deposition and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and linear sweep voltammetry. We confirmed pure -PbO2 crystals were on the electrode and it had a high oxygen evolution potential. The photoactivity and photoelectrochemical (PEC) properties of the -PbO2 electrode were investigated under visible light irradiation ( > 420 nm) for the decolorization of Methylene Blue. Pseudo first-order kinetics parameter (Kapp) for dye decolorization using the -PbO2 electrode achieved 6.71×10?4 min?1 under visible light irradiation, which indicated its excellent visible light-induced photoactivity. The Kapp of the PEC process was as much as 1.41×10?3 min?1 and was 1.71 times that of visible light irradiation or electrolysis even in the presence of the -PbO2 electrode. A significant synergetic effect was observed in the PEC system. We also employed TiO2 modified -PbO2 electrodes in this test, which revealed that the TiO2 immobilized on the -PbO2 electrode inhibited the visible light-induced PEC efficiency despite the amount of TiO2 used for electrode preparation. The -PbO2 electrode was also superior to the dimensionally stable anode (Ti/Ru0:3Ti0:7O2) in visible light-induced photoactivity and PEC efficiency.