X射线光电子能谱法研究UV_(254nm)光催化、O_3强化UV_(254nm)光催化和真空紫外光催化降解甲醛中Pt-TiO_2薄膜的表面性质(英文)

以Pt-TiO2为光催化剂,研究了气相甲醛分别在35 h连续UV254 nm光催化、O3强化UV254 nm(O3+UV254 nm)光催化和真空紫外(UV254+185 nm)光催化中的降解效率,考察了副产物O3的去除率,采用X射线光电子能谱(XPS)法分析Pt-TiO2在不同光催化前后Pt的电子态和累积有机产物,研究纳米Pt对甲醛降解和O3去除的强化机理.连续光催化降解实验表明,以纳米Pt改性TiO2可以同时增强甲醛和O3的去除率,特别是O3的去除率可提高3.1–3.4倍.对催化剂C 1s和O 1s峰分别经分峰拟合处理后,发现Pt-TiO2上累积的含羰基和羟基的有机物含量按以下顺序减少:UV254 nm光催化O3强化UV254 nm光催化真空紫外光催化,而在连续35 h光催化降解过程中,催化剂的失活现象却按相反的方向变得越来越不明显.负载的金属Pt在O3+UV254 nm和UV254+185nm光催化过程中被氧化成PtOads和Pt4+物种,而在UV254 nm光催化过程中金属Pt未被氧化,所以推测是气相中的O3和羟基自由基参与金属Pt的氧化过程.Pt-TiO2表面高价态的Pt氧化物种可作为光生电子捕获中心,强化光生载流子的分离过程,增强Pt-TiO2的光催化活性.Pt氧化物种可作为O3分解的活化中心,使Pt-TiO2对O3的分解效率远高于纯TiO2.以XPS对比研究在三种不同光催化环境中Pt-TiO2表面性质,可以解释在UV254+185 nm光催化过程中纳米Pt对甲醛和O3同时去除的强化机理,并说明了催化剂不失活的内在原因.     

声电协同氧化2-氯酚的机理及动力学研究

为提高有机物的降解效率, 提出了超声波协同电催化的集成一体化反应体系. 在声电协同反应器中, 研究了2-氯酚(2-CP)的去除效果, 探讨了声电协同工艺降解2-CP的机理, 建立了声电协同作用的动力学模型. 降解途径研究表明, 2-CP降解经历了羟基对位氧化、开环分解、形成小分子有机酸等过程. 数据拟合显示, 在电流密度20 mA·cm^-2、声频率20 kHz、声强0.27 W·cm^-2、2-CP初始浓度200 mg·L^-1等实验条件下, 声电协同氧化2-CP表观速率常数表示的增强因子达1.324, 表明协同效应存在. 根据反应动力学方程和Langmuir表面吸附理论, 推导出的动力学模型, 能较准确地描述声电协同体系中2-CP的初期降解情况, 模型数值解与实验值总体吻合良好, 模型参数取值与反应条件相关联.     

Co-Fe/SBA-15与过一硫酸盐联用非均相催化降解水中染料罗丹明B（英文）

由于硫酸根自由基(SO·-4)的强氧化性,基于SO·-4的高级氧化技术受到人们的高度关注.采用过渡金属活化过一硫酸盐(PMS)产生SO·-4用以分解有机物,反应体系简单,反应条件温和,且不需要额外的能量供给,因此,成为人们优先选用的方法,其中,采用高效、环境友好的非均相过渡金属催化剂活化PMS处理难降解有机物成为研究热点.本文研究了非均相CoFe/SBA-15-PMS体系对水中难降解染料罗丹明B(RhB)的降解.以SBA-15为载体,Co(NO3)2·6H2O和Fe(NO3)3·9H2O为前驱物,采用一步等体积浸渍法制备了CoFe/SBA-15,通过X射线衍射(XRD)、N2吸附-脱附、扫描电镜(SEM)、能谱(EDS)、透射电镜(TEM)和振动样品磁强计(VSM)等对其进行了表征.考察了焙烧温度、Co与Fe的负载量对CoFe/SBA-15催化性能的影响和该催化剂的重复使用性能,还考察了RhB降解动力学及催化剂CoF e/SBA-15投加量、氧化剂PMS投加量和反应物(Rh B和PMS)初始浓度对其性能的影响,探讨了Rh B的降解机理.结果表明:对于催化剂CoFe/SBA-15,合成焙烧后在SBA-15上负载的Fe、Co化合物主要是CoFe2O4复合物,它作为催化剂的活性中心负载在SBA-15的孔道内外.制备的焙烧温度对Co Fe/SBA-15催化性能几乎无影响,但对Co浸出影响显著.与SBA-15相比,催化剂10Co9.5Fe/SBA-15-700(Co和Fe负载量分别为10 wt%和9.5 wt%,焙烧温度700 oC)的比表面积、孔体积和孔径均减小,分别为506.1 m2/g,0.669 cm3/g和7.4 nm,但仍然保持SBA-15的有序六方介孔结构.该催化剂以棒状体的聚集态存在,聚集体直径大于0.25μm,其磁化强度为8.3 emu/g,因此,可通过外磁铁容易地从水中分离.相比之下,10Co9.5Fe/SBA-15-700具有最佳的催化性能和稳定性,可使Rh B的降解率达到96%以上,Co的浸出量小于32.4μg/L.在CoFe/SBA-15和PMS共存下,RhB的降解符合一级动力学方程,Rh B降解速率随CoFe/SBA-15和PMS投加量的增加和初始反应物浓度的减小而提高.淬灭实验结果表明,在Co Fe/SBA-15,PMS和RhB水溶液体系中,存在的主要活性自由基为SO·-4,它是由CoFe/SBA-15活化PMS产生的,对RhB的降解起决定性的作用.RhB降解过程的UV-vis结果表明,RhB的降解途径主要是蒽环打开,SO·-4优先攻击RhB的有色芳香烃环,然后RhB进一步分解为小分子有机物.CoF e/SBA-15循环使用10次仍能保持高催化活性和稳定性,在每次反应中RhB的降解率均大于84%,Co和Fe的浸出量均分别小于72.1和35μg/L.CoFe/SBA-15作为高效、环境友好的非均相催化剂可有效地活化PMS产生SO·-4降解水中RhB,具有实际应用的潜力.     

稻壳灰吸附剂对罗丹明B的吸附性能研究

以发电废弃物稻壳灰为原料,以NaOH为活化剂制备了稻壳灰吸附剂,并将其用于去除水中罗丹明B(Rhodamine B,Rh B)染料。系统考察了溶液pH值、初始浓度、吸附时间、吸附温度以及溶液离子强度对其吸附性能的影响。结果表明:pH=3时,稻壳灰吸附剂对水中Rh B的吸附效果最佳,饱和吸附容量q_m为322. 6mg·g~(-1);吸附热力学研究表明,吸附过程符合Langmuir等温吸附模型。吸附过程焓变ΔH为7. 67 kJ·mol~(-1),ΔS为24. 92 J·mol~(-1)·K~(-1),ΔG0,表明稻壳灰吸附剂对Rh B的吸附过程是自发的吸热熵增过程;吸附过程可在20 min内达到平衡,符合准二级动力学模型;吸附过程的活化能E_a为24. 1 kJ·mol~(-1)。吸附容量随着溶液离子强度的增大而减小,说明其吸附是以静电作用为主的吸附过程。10次循环使用后稻壳灰吸附剂对Rh B的吸附效率仍能保持91%以上,表明该材料可以多次循环使用,是潜在的高效吸附材料。     

氮缺陷石墨相氮化碳的制备及其光催化降解环境有机污染物性能（英文）

通过在三聚氰胺热分解过程中加入NaHCO_3制备出具有氮缺陷的石墨相氮化碳(g-C_3N_4),利用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、N2吸附-脱附、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-vis DRS)和固体荧光光谱(PL)等方法对其进行表征,并在可见光(λ420 nm)照射下,以水相中罗丹明B(Rh B)的降解为模型反应,研究了该氮缺陷g-C_3N_4对有机污染物降解的光催化活性。结果表明,引入氮缺陷可以提高g-C_3N_4对可见光的吸收以及电子-空穴对的分离效率,进而提高g-C_3N_4的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30 min内对Rh B的降解率分别为79.8%、100.0%和87.6%;而在相同条件下,没有氮缺陷的g-C_3N_4对RhB的降解率仅为59.8%。     

Sm-N-P-TiO_2纳米光催化剂在模拟太阳光下光催化降解4-氯酚的动力学

采用改进的溶胶-水热技术,制备了新型高性能Sm-N-P-TiO2纳米光催化剂。考察了条件因素对4-氯酚(4-CP)溶液在模拟太阳光下光催化降解的影响规律,并对不同催化剂的光活性进行了对比研究。结果表明,在实验条件下,4-CP光催化降解行为符合准一级动力学规律;随着4-CP溶液浓度增大,一级反应速率常数不断降低。在4-CP溶液初始浓度40 mg/L、催化剂用量1.5 g/L、溶液pH=5.2、溶液温度36℃、500 W氙灯照射2 h条件下,4-CP完全分解,表观速率常数Kapp为5.32×10-2min-1,Sm-N-P-TiO2的光催化活性是混晶型纳米TiO2(P25)的3.49倍;TOC去除率达到96.8%。     

[Bmim]BF4-NaH2PO4双水相萃取-高效液相色谱法测定水中痕量氯酚类内分泌干扰物

利用离子液体双水相萃取-高效液相色谱(HPLC)法测定了水中痕量氯酚类内分泌干扰物.以2,4-二氯酚(2,4-DCP)、2,6-二氯酚(2,6-DCP)和对氯苯酚(4-CP)为目标分析物,考察了影响离子液体双水相萃取率的主要因素,如分相盐的浓度、水相pH值、萃取时间及离子液体加人量.当NaH2PO4的浓度为0.5 g/...     

铜纳米粒子的制备及其对环境污染物的催化降解

本文以CuCl_2·2H_2O为铜源,在室温下合成了新的铜纳米粒子,并用X射线衍射仪(XRD)、X射线光电子能谱(XPS)、场发射扫描电镜(FESEM)以及透射电子显微镜(TEM)对合成的产物进行分析和表征。研究发现在合成的过程中氨水和苯酚的加入对铜纳米粒子的形成具有一定的保护作用,使合成的铜纳米粒子不易被氧化;同时探究了铜纳米粒子作为催化剂降解环境中的有机污染物,如对硝基苯酚(4-NP)、罗丹明B(Rh B)、亚甲基蓝(MB)和甲基橙(MO),和不同反应温度下催化剂对降解环境污染物的影响。运用朗伯比尔定律和准一级动力学公式计算不同温度下的降解速率及反应速率常数,结果显示合成的铜纳米粒子具有很好的催化性能。     

BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂的制备及光催化性能研究

以Bi(NO_3)_3·5H_2O和NH_4VO_3为原料,控制水溶液介质p H及反应时间,采用水热合成法制备钒酸铋(BiVO_4)及其复合物(BiVO_4/Bi_6O_6(OH)_3(NO_3)_3).利用X-射线粉末衍射、扫描电子显微镜和紫外-可见漫反射吸收光谱等手段对制备的样品进行了物理表征,结果表明,在控制反应时间为1 h,介质p H值在1.14~9.01之间时,制备的样品为BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合物,当p H值增加至10.92时为纯BiVO_4;控制介质p H为7.17,反应时间在1~12 h之间时得到BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂,反应时间为18 h时为纯BiVO_4.在可见光(λ≥400 nm)照射下,以有机染料罗丹明B(Rhodamine B,Rh B)为底物,研究不同条件制备的BiVO_4或者复合物为光催化剂的光催化特性,发现p H=7.17,水热反应12 h得到的催化剂(BiVO_4/Bi_6O_6(OH)_3(NO_3)_3)光催化降解活性高于对照制备的纯BiVO_4.同时在可见光照射下,BiVO_4/Bi_6O_6(OH)_3(NO_3)_3亦可以有效降解无色小分子2,4-二氯苯酚(2,4-Dichlorophenol,2,4-DCP),说明氧化过程涉及到光催化过程.分析BiVO_4/Bi_6O_6(OH)_3(NO_3)_3复合光催化剂对Rh B光催化降解过程中活性物种,表明在降解过程中主要涉及空穴和超氧氧化,O_2·~-起主要作用.     

NO2-存在条件下冰相中对氯苯酚的光转化

以125 W高压汞灯为光源, 在低温(-12—-14 ℃)条件下研究了冰相中有亚硝酸盐存在时对氯苯酚(4-CP)的光转化反应. 考察了各种因素对冰相中4-CP光转化的影响以及冰相中4-CP光转化的动力学和机理. 实验结果表明, 4-CP初始浓度、亚硝酸盐初始浓度、pH值和光强对冰相中4-CP光转化均有较大影响. 在180 min内, 4-CP和总有机碳(TOC)的转化率分别达到80%和32%, 在实验条件下, NO2-的存在能够改变4-CP在冰相中光转化的产物和机理.     

The electrochemical determination of phenolic derivates using multiple pulsed amperometry with graphite based electrodes

The electrochemical determinations of 4-chlorophenol (4-CP) and 4-nitrophenol (4-NP) by chronoamperometry (CA) and multiple pulsed amperometry (MPA) using expanded graphite-epoxy composite (EG-Epoxy) and rotating spectral graphite disc (SG) electrodes are reported. The electrochemical behaviours of both electrodes in the presence of organics informed about oxidation peak potential and the electrode fouling with organics concentration increasing. Setting up the oxidation peak potential as detection potential, only SG gave good electroanalytical performance using CA. However, by MPA applying both electrodes exhibited the capability to assess electrochemically and quantitatively the pollutants from aqueous solutions. UV spectrometric method detecting 4-CP and 4-NP at λ = 280 nm and λ = 398 nm wavelength, respectively was used for validation and parallel determinations.     

Visible-light-induced photocatalytic degradation of 4-chlorophenol and phenolic compounds in aqueous suspension of pure titania: demonstrating the existence of a surface-complex-mediated path

The visible-light-induced degradation reaction of 4-chlorophenol (4-CP) was investigated in aqueous suspension of pure TiO2. Contrary to common expectations, 4-CP could be degraded under visible illumination (lambda > 420 nm), generating chlorides and CO2 concomitantly. The observed visible reactivity was not due to the presence of trace UV light since the visible-light-induced reactions exhibited behaviors distinguished from those of UV-induced reactions. Dichloroacetate could not be degraded under visible light, whereas it degraded with a much faster rate than 4-CP under UV irradiation. The addition of tert-butyl alcohol, a common OH radical scavenger, did not affect the visible reactivity of 4-CP, which indicates that OH radicals are not involved. Other phenolic compounds such as phenol and 2,4-dichlorophenol were similarly degraded under visible light. The surface complexation between phenolic compounds and TiO2 appears to be responsible for the visible light reactivity. Diffuse reflectance UV-vis spectra showed that 4-CP adsorbed on TiO2 powder induced visible light absorption. The visible light reactivity among several TiO2 samples was apparently correlated with the surface area of TiO2. The visible-light-induced photocurrents on a TiO2 electrode could be obtained only in the presence of 4-CP. It is proposed that a direct electron transfer from surface-complexed phenol to the conduction band of TiO2 upon absorbing visible light (through ligand-to-metal charge transfer) initiates the oxidative degradation of phenolic compounds. When the surface complex formation was hindered by surface fluorination, surface platinization, and high pH, the visible-light-induced degradation of 4-CP was inhibited. The evidence of visible-light-induced reactions and the experimental conditions affecting the visible reactivity were discussed in detail.     

Solid phase extraction and uptake properties of multi-walled carbon nanotubes of different dimensions towards some nitro-phenols and chloro-phenols from water

Equilibrium sorption studies and solid phase extraction (SPE) of various phenols (Phenol (Ph), 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP)) on oxidized and raw multi-walled carbon nanotubes (MWCNTs) of various external diameters (10–20, 10–30, 20–40, 40–60 and 60–100?nm) and various lengths (short: 1–2?µm and long: 5–15?µm) were tested. Equilibrium sorption studies showed that 2-NP fits the Langmuir isotherm model (LIM), while the other phenolic compounds fit the Freundlich isotherm model (FIM). There was generally an inverse relation between external diameter of MWCNT and its sorption capacity towards phenolic compounds. Long MWCNT showed higher sorption capacity than short MWCNT. Thus dimensions of MWCNT play a role in retaining the sorbed molecules. Oxidation of MWCNT caused a decrease in sorption capacity of phenolic compounds of lower acidity where hydrophobic interaction is predominant, while it caused an increase in sorption capacity of phenolic compounds of higher acidity where H-bonding is predominant. The dependence of sorption on the acidity of phenols (pK_a values) indicates that the basic groups (pyrone-like groups) on the MWCNT surface play a role in the sorption process. In SPE experiments, it was found that hydrogen peroxide-oxidized MWCNT of external diameter 40–60?nm and length 5–15?µm was the best extractant at pH 6.5 using acetonitrile as eluting solvent. The optimized SPE procedure gave detection limits range: 0.027–0.202?ng?mL^?1 within the studied concentration range (10–100?ng?mL^?1). Application of the optimum SPE method on spiked tap water, reservoir water and stream water gave recovery range of 84.3–100% for 2-CP, 3-CP and 4-CP (%RSD range 2.8–9.2%); while Ph, 2-NP, 4-NP, and 2,4-DNP gave recoveries <67.6%.     

Photodegradation of rhodamine B dye using a microwave electrodeless UV lamp (MWUVL)

The photodegradation of organic dye rhodamine B (RhB) in an aqueous solution was studied using a microwave electrodeless UV lamp (MWUVL). The 185 nm vacuum UV (VUV) intensity of the MWUVL amounted to 12% of the total UV output, about 1.7 times as high as that of the con ventional low-pressure mercury lamp. An acidic condition was preferred for the degradation of RhB. Precipitate was generated during RhB degradation when the initial concentration of RhB solution was above 60 mg · L⁻¹. For 100 mg · L⁻¹ RhB at pH 4.0, the mass of precipitate produced was nearly half of the initial amount of RhB in the solution after irradi ation for 75 min. The corresponding degradation ratio of RhB reached up to 99.4% and COD reduced 77.4%. The photo degradation of RhB is mainly achieved by direct photolysis of RhB by 185 nm and OH radical oxidation. __________ Translated from Journal of Fudan University (Natural Science), 2006, 45(6): 726–731 [译自: 复旦学报 (自然科学版)]     

Sampling 4-chlorophenol in water by DGT technique with molecularly imprinted polymer as binding agent and nylon membrane as diffusive layer

For the first time, a diffusive gradients in thin films (DGT) device using molecularly imprinted polymer (MIP) as the binding agent and nylon membrane (NM) as the diffusive layer (NM-MIP-DGT) has been developed for sampling 4-chlorophenol (4-CP) in water. The MIP was prepared by precipitation polymerization with methacrylic acid as monomer and ethyleneglycoldimethacrylate as cross-linker. The diffusion coefficient of 4-CP through NM was obtained to be 0.788 ± 0.040 μ cm² s⁻¹ by diffusion cell method. The ratio was 1.01 ± 0.05 (mean ± standard deviation) for the concentration of 4-CP sampled by NM-MIP-DGT and analyzed by HPLC method to the total concentration of 4-CP in the synthetic solution where free 4-CP species dominated. The results showed that NM-MIP-DGT could sample 4-CP in synthetic solution accurately. The performance of NM-MIP-DGT for sampling 4-CP was independent of pH in the range of 3–7 and ionic strength in the range of 0.0001–0.1 mol L⁻¹ NaCl solution. The concentration of free form of 4-CP sampled by NM-MIP-DGT decreased with the increasing concentration of dissolved organic carbon in different water samples due to the electrostatic interaction of natural organic compounds with 4-CP. 1.8 mg L⁻¹ of the free form of 4-CP was determined by HPLC which was sampled by NM-MIP-DGT in an intermediate untreated industrial effluent. The NM-MIP-DGT can be a potential passive tool for sampling the free form of 4-CP in water.     

Degradation of 4-Chlorophenol using a Gas–Liquid Gliding Arc Discharge Plasma Reactor

The gas–liquid gliding arc discharge plasma is used directly to study degradation and dechlorination of 4-Chlorophenol (4-CP) in solution. The typical AC waveforms of discharge voltage and current revealed that the discharge behavior was not definitely periodic. The chemical oxygen demand (COD) abatement of 4-CP solution with stainless steel electrode is higher than that with aluminum or brass electrode; When air was used as carrier gas the COD abated from 1,679.2 to 190 mg/L (i.e., 88.68% abatement) after 76 min plasma treatment; Increasing gas–liquid mixing rate could also increase the degradation of 4-CP; adding appropriate amounts of Fe²⁺ or iron chips to the solution were found to be favorable for 4-CP degradation. The main intermediates of 4-CP degradation are p-benzoquinone, hydroquinone, 4-chlorocatechol, p-chloronitrobenzene, and ring cleavage products (acetic acid, glycol, propanone, and others). Furthermore, possible pathways of 4-CP degradation in solution are proposed.     

Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation

The degradation of 4-chlorophenol (4-CP) by using gamma rays generated by a ⁶⁰Co source in the presence of O₃ was investigated. The radiolysis of 4-CP and the kinetics of 4-CP mineralization were analyzed based on the determination of total organic carbon (TOC). The influence of initial 4-CP concentration and the free radicals scavengers (such as NaHCO₃ and t-butanol) on the 4-CP degradation was also studied. The results showed that when the radiation rate was 336 Gy·min⁻¹, 4-chlorophenol at concentration of 10 mg·L⁻¹ could be completely degraded at the radiation dose of 2 kGy. The degradation of 4-chlorophenol could be described by a first-order reaction model, the rate constant of 4-CP degradation by combined ozonation and radiation was 0.1016 min⁻¹, which was 2.4 times higher than the sum of radiation (0.0294 min⁻¹) and ozonation (0.0137 min⁻¹). It revealed that the combination of radiation and ozonation resulted in synergistic effect, which can remarkably increase the degradation efficiency of 4-CP.     

Photochemical degradation of environmentally persistent perfluorooctanoic acid (PFOA) in the presence of Fe(III)

Environmentally persistent and bioaccumulative perfluorooctanic acid (PFOA) was difficult to be decomposed under the irradiation of 254 nm UV light. However, in the presence of 80μmol /L Fe(III), 80% of PFOA with initial concentration of 48μmol/L (20 mg/L) was effectively degraded and 47.8% of fluorine atoms in PFOA molecule were transformed into inorganic fluoride ion after 4 h reaction. Shorter chain perfluorocarboxylic acids bearing C3-C7 and fluoride ion were detected and identified by LC/MS and IC as the degradation products in the aqueous solution. It was proposed that complexes of PFOA with Fe(III) initiated degradation of PFOA irradiated with 254 nm UV light.     

On-line solid-phase extraction with molecularly imprinted polymers to selectively extract substituted 4-chlorophenols and 4-nitrophenol from water

Three polymers have been synthesised using 4-chlorophenol (4-CP) as the template, following different protocols (non-covalent and semi-covalent) and using different functional co-monomers, 4-vinylpyridine (4-VP) and methacrylic acid (MAA). The polymers were evaluated to check their selectivity as molecularly imprinted polymers (MIPs) in solid-phase extraction (SPE) coupled on-line to liquid chromatography. The solid-phase extraction procedure using MIPs (MISPE), including the clean-up step to remove any interferences, was optimised. The 4-VP non-covalent polymer was the only one which showed a clear imprint effect. This MIP also showed cross-reactivity for the 4-chloro-substituted phenols and for 4-nitrophenol (4-NP) from a mixture containing the 11 priority EPA (Environmental Protection Agency) phenolic compounds and 4-chlorophenol. The MIP was applied to selectively extract the 4-chloro-substituted compounds and 4-NP from river water samples.