Photocatalytic degradation of perfluorooctanoic acid with β-Ga2O3 in anoxic aqueous solution

Perfluorooctanoic acid (PFOA) is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical (HO·) due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga₂O₃ in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron (e_cb^-) coming from the β-Ga₂O₃ conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids (PFCAs, C_nF_2n+1COOH, 1 ≤ n ≤ 6) were the dominant products. Furthermore, the concentration of F^- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N₂. The degradation reaction followed first-order kinetics (k = 0.0239 min^-1, t_1/2 = 0.48 hr). PFCAs (C_nF_2n+1COOH, 1 ≤ n ≤ 7) were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves e_cb^- attacking the carboxyl of C_nF_2n+1COOH, resulting in decarboxylation and the generation of C_nF_2n+1·. The produced C_nF_2n+1· reacted with H2O, forming C_nF_2n+1OH, then C_nF_2n+1OH underwent HF loss and hydrolysis to form C_nF_2n+1COOH.     

Kinetics of photoelectrocatalytic degradation of humic acid using B2O3·TiO2/Ti photoelectrode

An innovative photoelectrode, B₂O₃·TiO₂/Ti electrode, was prepared by galvanostaticanodisation. The morphology and crystalline texture of the B₂O₃·TiO₂ film on electrode were examined by acomic force microscopy (AFM) and X-ray diffraction respectively. The examination results indicated that the anatase was the dominant component. The kinetics of photoelectrocatalytic(PEC) degradation of humic acid(HA) was investigated; the results demonstrated that effects from strongness to weakness on the photoelectrocatalytic degraded rate of humic acid: power of UV-lamp, area of TiO₂ film, bias, original concentration of humic acid solution. The optimum conditions were power of UV-lamp 125 W, area of TiO2 film 42.0 cm² , bias 1.4 V, original concentration of humic acid solution 5 mg/L in this PEC reaction system.     

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 remediation of γ-HCH contaminated soil induced by α-Fe2O3 and TiO2

Heterogeneous photocatalytic degradation of γ-HCH on soil surfaces was carded out to evaluate the photocatalytic effectiveness of α-Fe2O3 and TiO2 toward degrading γ-HCH on soil surfaces. After being spiked with γ-HCH, soil samples were loaded with α-Fe2O3 or TiO2 and exposed to UV-light irradiation. Different catalyst loads, 0%, 2%, 5%, 7%, and 10% (wt.)α-Fe2O3 ; 0%, 0.5%, 1%, 2:(Wt.)TiO2, were tested for up to 7 d irradiation. The effects of soil thickness, acidity, and humic substances were also investigated. The obtained results indicated that the γ-HCH photodegradation follows the pseudo-first-order kinetics. The addition of α-Fe2O3 or TiO2 accelerates the photodegradation of γ-HCH, while the photodegradation rate decreases when the content of α-Fe2O3 exceeds 7% (wt.).The degradation rate increases with the soil pH value. Humic substances inhibit the photocatalytic degradation of γ-HCH., and trichlorobenzene are detected as photodegradation intermediates, which are gradually degraded with the photodegradation evolution.     

Photodegradation of 2,4-D induced by NO2- in aqueous solutions：The role of NO2

To elucidate the effect of nitrite ion （NO2^-） on the photodegradation of organic pollutants, a 300 W mercury lamp and Pyrex tubes restricting the transmission of wavelengths below 290nm were used to simulate sunlight, and the photodegradation processes of 2,4-dichlorophenoxyacetic acid （2,4-D） with different concentrations of NO2^- in freshwater and seawater were studied. The effect of reactive oxygen species （ROS） on the photolysis of 2,4-D was also demonstrated using electron paramagnetic resonance （EPR）. The results indicated that the 2,4-D photolysis reaction followed the first-order kinetics in freshwater and seawater under different concentrations of NO2^-. Meanwhile, the photochemical reaction rate of 2,4-D increased with increasing concentration of NO2^-. When the concentration of NO2^- was lower than 23 mg/L, the photodegradation rate of 2,4-D in seawater was higher than that in freshwater. However, when the concentration of NO2^- was reached 230 mg/L, 2,4-D degradation slowed down in seawater. It was important to note that EPR spectra showed NO2 radical was generated in the NO5 solution under simulated sunlight irradiation, indicating that 2,4-D photodegradation could be induced by NO2. These results show the key role of NO2^- in photochemistry and are helpful for better understanding of the phototransformation of environmental contaminants in natural aquatic systems.     

Reaction site and mechanism in the UV or visible light induced TiO2 photodegradation of Orange G

For TiO2 heterogeneous reaction, the reaction site and the detailed mechanism are interesting and controversy topics. In this paper, effects of surface fluorination of TiO2 on the photocatalytic degradation of an azo dye, Orange G（OG） under UV or visible light irradiation were investigated, and the possible reaction site and mechanism were elucidated. The adsorption of OG on TiO2 was nearly inhibited by fluoride but its UV light induced photodegradation rate was greatly increased by a factor of about 2.7, which was due to the more generated free hydroxyl radicals. It supported the views that fluoride could desorb the oxidant species from surface and that the reaction sites could move to the bulk solution. In TiO2/Vis system, the observed inhibition effects of fluorination could be interpreted by the competitive adsorption, which provided additional evidences that the visible light sensitized photodegradation of dye pollutants on the catalyst surface.     

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.     

Photoassisted Fenton degradation of phthalocyanine dyes from wastewater of printing industry using Fe(Ⅱ)/γ-Al2O3 catalyst in up-flow fluidized-bed

Fe(II)/γ-Al2O3 powders synthesized using the dipping method were produced from a mixed aqueous solution containing aluminium oxide(γ-Al2O3) and iron(II)-precursor(FeSO4), and used for photoFenton degradation of phthalocyanine dyes(PCS) under ultraviolet(UV) irradiation in an up-flow fluidized bed. The catalysts were characterized by XRD, ESCA, BET, EDS and SEM. The results showed that Fe2+ion was compounded on the γ-Al2O3 carrier. The effects of different reaction parameters such as catalyst activity, dosage and solution pH on the decolorization of PCS were assessed. Results indicated that maximum decolorization(more than 95%) of PCS occurred with20 wt% Fe(II)/γ-Al2O3 catalyst(dosage of 60 g/L) using a combination of UV irradiation and heterogeneous Fenton system. The degradation efficiency of PCSincreases as pH decreases, exhibiting a maximum efficiency at pH 3.5. The recycled catalyst was capable of repeating three runs without a significant decrease in treatment efficiency, and this demonstrated the stability and reusability of catalyst.     

啶虫脒光催化降解动力学的优化及其降解产物的分析

利用光催化技术通过单因素和中心复合实验对啶虫脒的降解动力学进行了研究.在单因素实验中,探讨了催化剂浓度、底物浓度、温度和p H对其降解动力学的影响.结果表明啶虫脒光催化降解动力学符合Langmuir-Hinshelwood模型,随着温度的升高和底物浓度的降低其降解速率增加,而弱酸和碱性条件有利于啶虫脒的光催化降解.中心复合实验通过研究上述4种因素之间的相互关系得到啶虫脒的光催化降解最优条件为:Ti O2浓度2.30 g·L-1,底物浓度90.0μmol·L-1,温度37.5℃,溶液初始p H值为5.0.最后,HPLC检测到啶脒虫光催化降解产物主要有7个,其中6个降解产物极性大于啶虫脒.     

氙灯/TiO2体系下敌草隆光催化降解动力学的研究

利用光催化技术通过单因素和中心复合实验对敌草隆的降解动力学进行了研究.在单因素实验中,通过Langmuir-Hinshelwood动力学模型对敌草隆的光催化降解进行了模拟,并系统地考察了催化剂用量、溶液初始pH值和温度对其降解动力学的影响,结果表明,敌草隆的光催化降解符合假一级动力学,中性条件有利于敌草隆的光催化降解,并且随着温度的升高敌草隆光催化降解速率增大;而中心复合实验则着重探讨3个单变量之间相互作用的关系,通过建立数学模型得到敌草隆光催化降解的最佳条件为:TiO2浓度2.98 g·L-1,溶液初始pH=7.78,反应温度为40℃.     

三氯乙烯在薄膜催化剂上的光催化降解动力学

研究了不同初始浓度三氯乙烯(TCE)在TiO₂薄膜催化剂上的光催化降解.结果表明,TCE在主波长为254nm的低压汞灯照射下易于发生光降解反应,而TiO₂薄膜催化剂能显著提高TCE的降解.光催化降解反应的伪一级速率常数随初始浓度的增加先升后降.在Langmuir-Hinshelwood方程基础上建立的光催化降解动力学模型包含了发生在薄膜催化剂表面的光催化氧化过程和发生的溶液体相的光降解过程,该动力学模型适用于表达低浓度有机物在薄膜催化剂上的光催化降解动力学.     

含酚废水光催化降解的试验研究

以主波长为254nm的紫外光灯为光源,TiO2为光催化剂,研究了对苯二酚光催化降解。建立了简单的符合拟一级的动力学模型,并进一步研究了其他因素如催化剂的活化温度、TiO2的用量以及酸度对降解率的影响。     

克百威光催化降解动力学的研究

采用TiO2光催化技术对克百威的降解进行了研究,并系统地考察了催化剂用量,溶液初始pH值,底物浓度,活性氧物种和各种阴阳离子对其降解动力学的影响.用Langmuir-Hinshelwood动力学模型对克百威的光催化降解进行了研究,结果表明,克百威在弱碱性条件下降解速率最快,×OH对克百威降解贡献比约为93.4%,h+和其他ROSs的贡献则相对较小.而水溶液中的阴离子BrO3-和S2O82-对克百威的光催化降解有促进作用,I-则有明显的抑制作用,并且水溶液中的K+,Ca2+,Na+,Mg2+和Cu2+等金属阳离子对克百威的降解也均体现了一定程度的抑制作用.     

介孔氮化碳光催化降解诺氟沙星的动力学机制

采用一种简单高效的制备方法,利用SiO₂为模板制备出具有更高催化活性的介孔氮化碳材料（mpg-C₃N₄）,并通过透视电子显微镜（TEM）、X射线衍射（XRD）、氮气吸脱附测试（BET）、傅里叶变换红外光谱（FT-IR）、光电子能谱（XPS）对mpg-C₃N₄的形貌、组成结构进行表征.结果显示,mpg-C₃N₄表面存在大量直径约12nm的孔状结构,与g-C₃N₄相比,比表面积大幅度增大,并因此提供了更多的活性位点从而提高其光催化活性.使用紫外可见漫反射光谱（UV-vis DRS）和荧光光谱（PL）对其光电化学性能进行测试.结果表明介孔材料的引入使得氮化碳的吸收光谱发生红移,并降低了光生电子-空穴对复合率,从而提高对可见光利用效率.通过对诺氟沙星（NOR）的降解与吸附实验研究表明,NOR的光催化降解过程符合一级动力学和Langmuir-Hinshelwood动力学模型,而mpg-C₃N₄对NOR的吸附符合二级动力学,表明NOR的光催化降解主要发生在催化材料的表面且以化学吸附为主.吸附实验表明mpg-C₃N₄在30min内可以吸附56.78%的NOR,降解实验显示,光解1.5h后,超过90%的NOR可被降解.相比体相g-C₃N₄,mpg-C₃N₄表现出良好的吸附性能和光催化性能.pH值影响实验表明pH值约为7.41时达到最佳降解效果,主要归因于药物形态与材料表面电荷作用.淬灭实验表明O₂^·-和h⁺是降解体系中的主要活性物质.     

单偶氮染料AY17的光催化降解动力学及机制

为了研究水体环境中单偶氮染料酸性黄17(AY17)有效地去除方式及其可能的降解途径、转化和归趋等,实验首先探索了AY17在不同深度氧化体系中降解的可行性,研究发现其去除效率的大小按照UV/H_2O_2UV/Na_2S_2O_8≈UV/FeSO_4·7H_2OUV/KHSO_5UV/TiO_2排列.然后选取UV/TiO_2体系,研究了催化剂用量,反应温度,底物浓度以及溶液初始p H值等因素对其光催化降解动力学的影响,结果表明AY17的光催化降解遵循假一级动力学,其降解速率常数为0.011 2 min~(-1);当催化剂TiO_2用量为3 g·L~(-1)时其降解效果最好;高温有利于AY17的光催化降解,而随着底物浓度和溶液初始p H值的升高,其降解速率常数显著下降.最后利用GC/MS对AY17光催化降解中间产物进行了初步鉴定,研究发现在·OH等活性氧物种的作用下偶氮键的断裂、羟基自由基对芳香环上基团的取代以及吡唑环的裂解是其主要降解途径.     

纳米Bi_2O_3-Ni_2O_3的制备及光催化性能研究

采用微乳法制备了镍、铋复合氧化物纳米粒子,以XRD、TG-DTA、XPS及紫外-可见光谱仪对合成材料进行了表征,并以甲苯为目标污染物对其气-固复相光催化性能进行了研究。结果表明:Ni和Bi都显+3价,XRD曲线上分别出现Ni2O3和Bi2O3的特征衍射峰,制备样品是Ni2O3与Bi2O3复合氧化物,对于单一Bi2O3,制备的复合氧化物由于Ni2O3具有较强的电子富集能力,能够快速地传递光照射产生的电子,导致光生电子与空穴分离效率大大提高,促进了氧化反应,显示出了较好的光催化活性。     

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.     

邻-氯酚在TiO2膜上光催化降解及反应动力学特征

以钛酸四丁酯为原料采用Sol Gel法制备了玻璃负载TiO2 膜光催化剂 ,应用XRD表征了不同实验条件下薄膜中TiO2 的晶相结构和粒度。分析了不同层数TiO2 膜的光催化活性和溶液 pH值对邻 氯酚 (2 CP)的影响。结果表明 :处理温度为 50 0℃时不同厚度薄膜中TiO2 均为锐钛矿晶型 ,粒径 8～ 33nm ,5层涂膜光催化活性最高。在高 pH值和低pH值区域 2 CP ,在TiO2 膜上的光催化降解速率较大。 2 CP初始浓度 (C0 )与反应速率 (r0 )的关系符合Langmuir Hinshelwood方程 ,当C0 ≤ 0 .6mmol·L- 1 时 ,降解反应可用一级动力学模式来描述。