催化高压脉冲放电降解水中苯酚

采用向高压脉冲放电反应器中投加催化剂的方式来强化降解苯酚的效果,并考察了不同催化剂及其投量对苯酚处理效果的影响。与单独高压脉冲放电进行比较,Fe2+投量为0.05 mmol/L时,催化效果最好,可以使苯酚的去除率由15.45%提高到94.94%,其次是Fe3+,投量为0.061mmol/L时,苯酚的去除率提高了3倍。这主要是因为Fe2+和Fe3+诱发放电过程中产生的H2O2发生芬顿和类芬顿反应,生成HO.。另外,由于放电过程中紫外光解的作用,投加0.1mmol/LH2O2可以使苯酚的去除率提高1倍。粉末活性炭的良好吸附性能也使它具有一定的催化作用,投量5 mg/L可使苯酚的去除率提高1.3倍。     

The evaluation of the polarization resistance in a tubular electrode and its application to the hydrogen electrode reaction

An alternative method for the determination of the kinetic parameters involved in the elementary steps of the reaction mechanism of the hydrogen electrode reaction is proposed. It is based on the determination of the variation of the polarization resistance in a tubular platinum electrode with a laminar flow of electrolyte as a function of the activity of protons of the electrolyte solution. A theoretical expression that relates the experimental variables and the equilibrium polarization resistance is developed, which takes into account the current distribution along the electrode surface. The results are compared with others obtained previously, contributing to the verification of the kinetic mechanism through a completely different experimental procedure.     

针-板式高压脉冲气液两相放电降解废水中的苯酚

为了提高脉冲放电对有机物的降解效果,以苯酚为处理对象建立了单针-板电极形式的脉冲放电体系,考察了各因素对苯酚降解的影响并分析了降解过程中间产物及其浓度变化。结果表明,脉冲电压、电极间距、针-液间距、脉冲频率、曝气量等影响因素对苯酚降解率有很大影响;随着脉冲电压的增大,苯酚降解率增大,电压达到一定值后,苯酚降解率增大不再明显,趋于稳定;随着电极间距、针-液间距、脉冲频率、曝气量的增大,苯酚降解率增大,但当这些因素达到一定值后继续增大,苯酚降解率反而降低。100mL浓度为100mg/L的苯酚废水在电极间距10mm、针-液间距7.5mm、脉冲电压26kV、脉冲频率70Hz、曝气量1.5L/min的最佳条件下,放电60min时苯酚降解率为64.63%,放电140min时达到了85.02%。中间产物间苯二酚、对苯二酚、对苯醌、邻苯二酚在放电过程中浓度随着放电时间的延长先增大后减小,最后浓度都趋于零。其中,间苯二酚浓度最低并且分段出现,对苯醌浓度最大,邻苯二酚最先消失,考察产物变化规律以提高苯酚降解的彻底性。     

水中高压脉冲放电机理与效能

水中高压脉冲放电是一种具有潜力的新型水处理技术，这是由于高压脉冲放电具有许多独特的性质。放电过程中会产生许多有利于去除污染物的复杂的物理以及化学反应。作者介绍了一些基本原理，同时综述了近来国内外高压脉冲放电水处理技术的研究发展状况，高压脉冲放电过程的催化强化去除污染物的机理以及灭菌去除污染物的效能。     

高压脉冲液相放电降解水中邻氯苯酚

研究了高压脉冲液相放电降解水中邻氯苯酚的特性脉冲峰压的升高、电极距离的缩短、脉冲频率的加大均使邻氯苯酚的降解速率增加.在脉冲峰压为30 kV、电极距离为2 cm、脉冲频率为150 Hz条件下,o-CP的降解率约为98.7%.较高输入电压下,溶液初始离子含量的增加,会使放电形式由火花放电→流柱放电→电晕放电转变.在火花放电和流柱放电条件下,邻氯苯酚降解率无明显变化,但在电晕放电时,降解率有所降低.邻氯苯酚受羟基的攻击,生成2-氯-对苯二酚,并进一步被氧化生成2-氯-1,4-对苯醌,2-氯-1,4-对苯醌开环后,进一步被氧化,自由基最终生成丙酸、草酸、乙酸以及甲酸等低分子有机酸.     

Effect of cations in solution on the oxidation of methanol on the surface of platinum electrode

The effect of metal cations in solution on the oxidation of methanol on the electrode surface of platinum is a neglected aspect to direct methanol fuel cell (DMFC). In this paper, a smooth platinum electrode absorbing metal cations as the working electrode was applied to investigate the methanol oxidation with the cyclic voltammetry (CV) in 1.0 mol L⁻¹ H₂SO₄. From the analysis of experiment, it is found that the cations, Li⁺, Ce⁴⁺, Mn²⁺, Ni²⁺, Cu²⁺, have some negative effect on the catalytic oxidation of methanol on the surface of platinum. The degree of the effect from different cations was analyzed.     

碳材料在电双层电容器电极应用的最新研究

电容器与二次电池相比,有着显著的优点,尤其是高功率并能提供大电流的电双层（超级）电容器正是时代所需。对目前已用做电双层电容器电极材料的活性碳纤维、纳米碳管和膨胀性石墨的研究情况分别做了论述。与膨胀性石墨相比,如何发挥活性碳纤维和碳纳米管的实际电容效率是目前研究的重点。     

The role of platinum oxide in the electrode system Pt(O2)/yttria-stabilized zirconia

The existence and role of platinum oxide in the solid state electrode system Pt(O₂)/yttria-stabilized zirconia is discussed. Covering and porous model-type Pt film electrodes on YSZ single crystals are investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and in situ scanning photoelectron microscopy. The formation of Pt oxide and its amount strongly depend on the experimental conditions, such as temperature, oxygen partial pressure, and oxygen flux towards the electrode during anodic polarization. Electrode activation and deactivation processes can be explained by formation and decomposition of Pt oxide, which is reducing or inhibiting the oxygen exchange rate.     

高压脉冲电场中活性氧化铝滴滤床对印染废水脱色的效能

研究了一种新型的用于去除液相污染物的方法———高压脉冲电场中活性氧化铝滴滤床去除有机物,并考察了其对印染废水脱色的效能。结果表明在高压脉冲电场与活性氧化铝的相互作用下和其他合适的条件下亚甲基蓝去除率可达67.68%。随着电压的增加、流速的减小、初始质量浓度的减小、pH的增加和空气的通入,亚甲基蓝的分解效率都得到了增加。在脉冲电场作用下,活性氧化铝表面产生局部放电,提高了亚甲基蓝的降解率;同时放电过程也增强了氧化铝对于亚甲基蓝的吸附,二者的相互作用促进了亚甲基蓝的降解。     

Application of channel flow double electrode to the study on platinum dissolution during potential cycling in sulfuric acid solution

The applicability of a channel flow double electrode (CFDE) as an in situ monitoring method of Pt dissolution during potential cycling in 0.5 M H₂SO₄ solution at 25 °C was investigated. In the CFDE, Pt ions (Ptⁿ⁺) dissolved from a platinum working electrode were detected by reducing them to Pt on a gold collector electrode which was placed at the downstream. The detection of the Pt dissolution by the collector current was confirmed by EPMA analysis of the collector electrode surface. In anodic scan, a rise of the collector current above 1.05 V clearly indicated the platinum dissolution. The collector current showed two different rates of dissolution, i.e. a lower rate from 1.05 to 1.3 V where only one layer of oxide (PtO) is formed and the higher rate from 1.3 to 1.46 V where two layers of oxides (probably PtO/PtO₂) are formed. The collector current, in the cathodic scan, clearly showed two different reduction peaks due to the Pt deposition, which was confirmed by EPMA analysis. On the basis of collector current, the rate and potential range of the Pt dissolution are discussed.     

Identification of the reaction mechanism of the Pt,O2/La(Sr)Ga(Mg)O3−α electrode system

By means of impedance spectroscopic measurements, the electrode conductivity near the equilibrium potential was determined for the Pt,O₂/La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 electrode system as a function of the oxygen partial pressure (3-105 Pa) and temperature (816-1147 K). A model of two parallel processes proceeding in the electrode system is proposed. It is assumed that one of the reaction routes is localized at the platinum-gas interface and is limited by the diffusion of adsorbed oxygen on the platinum surface towards the three-phase “electrode-electrolyte-gas” boundary. The other route is localized at the “electrolyte-gas” interface and its rate is determined by the diffusion of electron holes in the electrolyte. The results of a calculation based on the proposed model are in accordance with the experimental data. The calculated values of the enthalpy and entropy of oxygen adsorption on platinum, the activation energy of oxygen diffusion along the platinum surface, and the activation energy of the hole transport in the electrolyte agree with literature data.     

A study of the electrochemical oxidation of hydrogen peroxide on a platinum rotating disk electrode in the presence of calcium ions using Michaelis-Menten kinetics and binding isotherm analysis

The present work demonstrates a potential suppression in the electrochemical signal of H₂O₂ oxidation due to the presence of Ca²⁺ ions. A mechanistic scheme was proposed to include a reversible interaction of Ca²⁺ ions with either the electrode surface binding sites (competitive) or the complex sites (non-competitive). The degree of inhibition was inspected by evaluating the kinetic currents as a function of [Ca²⁺] applying Koutecky-Levich kinetics. These observations were further supported with models based on enzyme kinetics such as Michaelis-Menten model applying Lineweaver-Burk plot along with non-linear least-square fitting analysis. The experimental results suggests that the strength of the complex binding sites decreases considerably with increasing [Ca²⁺] and that a single H₂O₂ molecule is required to combine with one available active binding site.     

Anodic electrode reaction of p-type silicon in 1-ethyl-3-methylimidazolium fluorohydrogenate room-temperature ionic liquid

The anodic electrode behavior for a p-type silicon single crystal electrode ((1 0 0), ρ = 0.01-0.02 Ω cm, boron doped) was examined in the 1-ethyl-3-methylimidazolium fluorohydrogenate, EtMeIm(FH)_2.3F, room-temperature ionic liquid (RTIL). The electrochemical behavior was very similar to that in conventional HF aqueous solution. After the anodic electrode reaction, the Si electrode was uniformly covered with a mesoporous Si layer having a pore size of ∼25 nm. The mesoporous layer did not exhibit a photoluminescence spectrum in the visible region due to the lack of Si-H termination. However, after chemical treatment with an ethanolic HF solution, a subset of the porous Si samples showed a very weak photoluminescence.     

Investigation of the reaction zone in heterogeneous explosives substances using an electrical conductivity method

A technique for measuring the electrical conductivity profile behind a detonation wave front with a resolution of about 0.1 mm was used to analyze the reaction zone in heterogeneous explosives. TNT-RDX mixtures, RDX with additives of water, NaCl, and a saturated aqueous solution of NaCl, and pure RDX of low density were studied. It was shown that the particle size of the explosive can have a significant effect on the structure of the reaction zone. The most narrow conducting zone (0.22 mm) was observed in fine RDX of density 1.2 g/cm³. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 2, pp. 109–115, March–April, 2008.     

Fabrication of polymer‐dispersed liquid crystals with low driving voltage based on the thiol‐ene click reaction

Polymer‐dispersed liquid crystals (PDLCs ) with a well‐defined polymer matrix were successfully fabricated by the thiol‐ene click reaction based on poly(ethylene glycol) diacrylate (PEGDA ) and trimethylolpropanetris‐(3‐mercaptopropionate) (TMTP ). UV ?visible spectrophotometry, Fourier transform IR spectroscopy, SEM and polarized optical microscopy were employed to explore the PDLC films obtained. Electro‐optical properties were studied with a UV ?visible spectrophotometer. It was found that the PDLC films with optimal thiol content fabricated by the thiol‐ene click reaction showed high transmittance, low driving voltage and a low memory effect. It was concluded that the driving voltage change of PDLCs with different thiol concentrations was caused by the polymerization rate and the structure of the polymer matrix. © 2017 Society of Chemical Industry     

Study of the water gas shift reaction on Fe in a high temperature proton conducting cell

The water gas shift (WGS) reaction was studied in a double-chamber high temperature proton conducting cell (HTPC). The proton conductor was a strontia–ceria–ytterbia (SCY) disk of the form: SrCe_0.95Yb_0.05O₃₋ and the working electrode was a polycrystalline Fe film. The reaction temperature and the inlet partial pressure of CO varied between 823 and 973 K, and between 1.0 and 10.6 kPa, respectively. The inlet partial pressure of steam (P_H2O) was kept constant at 2.3 kPa. An increase in the production of H₂ was observed upon “pumping” protons away from the catalyst surface. The Faradaic efficiency (Λ) was lower than unity, indicating a sub-Faradaic effect. The highest value of rate enhancement ratio (ρ) was approximately 3.2, at T = 823 K. The proton transport number (PTN) varied between 0.45 and 1.0. An up to 99% of the produced H₂ was electrochemically separated from the reaction mixture.     

A wall-jet electrode reactor and its application to the study of electrode reaction mechanisms Part III: Study of the mechanism of the a.c. electrolytic graining of aluminium in hydrochloric acid

The mechanism of the a.c. electrolytic graining of aluminium in hydrochloric acid is determined from the analysis of the potentiostatic transient behaviour of the system aluminium–electrolyte under anodic and cathodic polarization and comparison of experimentally determined transients with calculated values derived from a candidate mechanistic scheme. It has been established, that the oxidation of aluminium in the development of a distinct surface morphology occurs according to the Al3+ ions being dissolved from the surface and removed to the bulk of the solution, hence forming pits. Al(Cl)3 is a solid intermediate. The morphology developed, is determined by the excess of Cl– ions created at the electrode surface, with respect to the bulk concentration. The accumulation of Cl– ions is governed by the ratio between the rate constant for the formation of Al(Cl)3, set by the flux of charges forced across the electrode–solution interface per unit surface area taking part in the active dissolution of aluminium and the mass transport rate of the Cl– ions. The reduction of H+ ions in the cathodic half period of the applied alternating current is mass transport controlled. The concomitant rise in interfacial pH causes Al3+ ions formed in the preceding anodic half period, which are not yet removed from the electrode–solution interface, to precipitate as aluminium.     

The role of iron in the prevention of nickel electrode deactivation in alkaline electrolysis

There is some uncertainty concerning the role of iron deposits on the surface of nickel electrodes with respect to electrode activity during alkaline water electrolysis. Iron deposits variously have been reported to enhance nickel electrode activity by providing additional surface area from electrolytic deposition of solution phase iron species or to depassivate nickel electrodes via a surface interaction effect. In this study, nickel electrodes were sputtered with a smooth iron layer to determine the effect of metallic iron on the electrode surface without significantly changing the electrode surface area. A permeation cell with 8 mol/L KOH at 70 °C was used to follow nickel electrode potentials during hydrogen evolution while the permeation current was used to detect changes in the electrode structure.Short term measurements reveal no difference in behavior of coated and non-coated electrodes. Longer term results showed that a metallic iron coating on nickel electrodes prevented deactivation of the electrodes. The deactivation effect was associated with an increased hydrogen flux through the electrodes indicative of an elevated hydrogen concentration at the electrode surface. This high surface concentration is concluded to be the result of nickel hydride phase formation at the surface of the nickel electrodes. The iron coating prevents this surface phase from forming and hence prevents deactivation of the electrode.     

The occurrence of the hexagonal phase in two long chain monodisperse carboxylic acids at high pressure

High-pressure differential thermal analysis (DTA) experiments have allowed the pressure-temperature phase diagrams to be constructed for the monoacid CH₃-(CH₂)₁₉₀-COOH and the diacid HOOC-(CH₂)₁₉₂-COOH. The current work follows on from previous work concerning the high-pressure phase of various monodisperse n-alkanes. The use of a diamond anvil cell calibrated from DTA data has allowed the morphology of each sample to be investigated as a function of pressure and temperature and for the crystallization, melting and hexagonal/orthorhombic transitions to be examined directly. It was shown that the monoacid displayed a similar behaviour to the n-alkane of twice its chain length due to end group pairing, whereas the diacid shows a wider hexagonal stable region, which extends to pressures as low as 0.35 GPa. This enhanced stability is thought to be due to increased configurational entropy due to unlimited end group association.     

间歇式聚丙烯装置产品熔体流动指数的控制

针对间歇式液相本体法聚丙烯装置的生产特点,根据实际生产经验,从原料、催化剂的选择与配方、升温操作、氢调、设备维护等对如何控制聚丙烯粉料熔体流动指数进行了分析。结果表明:只要控制得当,间歇式聚丙烯装置产品的熔体流动指数可以控制在(n±1.5)g/10min(n为预定值)的稳定范围。