智能极谱式氧分析仪在煤气测量中的应用

1 工作原理 极谱式氧分析器是利用一定的极化电压下,氧的还原扩散电流与氧的浓度有一定的关系来进行测量的。测量传感器为隔膜式极谱池,铂阴极和银阳极以聚氟乙稀为隔离膜,在极化电压的作用下,气样中的氧分子透过隔膜到达阴极时,在两电极上发生氧化还原反应: 阴极 O_2 2H_2O 4e→4OH~- 阳极 4Ag 4Cl~-→4AgCl 4e 反应迅速达到平衡,同时产生极化扩散电     

电化学技术在陶瓷制备中的应用

介绍了电化学制备陶瓷的各方法原理,主要包括阴极电沉积和阳极电沉积陶瓷薄膜2种方式.其中阴极电沉积陶瓷原理基于胶体化学的DLVO理论,包括电泳沉积（EPD）和电解沉积（ELD）2种方式;而阳极电沉积原理基于阳极氧化理论,主要介绍了阳极氧化、微弧氧化和水热电化学技术.阳极电沉积需要消耗阳极材料,但其陶瓷和基体结合力相对较强.     

Yb2O3/TiO2纳米粒子的制备及其超声波/紫外光协同催化降解邻硝基苯酚的研究

以钛酸丁酯为原料,用溶胶-凝胶(Sol-gel)法制备了Yb2O3/TiO2纳米粒子.采用透射电子显微镜和X光衍射仪对粉体的粒径、物相和形貌进行了表征.研究了超声波/紫外光协同催化氧化水中邻硝基苯酚的降解效果,考察了邻硝基苯酚的起始浓度、超声波声强、反应温度和催化剂投加量对邻硝基苯酚降解速率的影响.研究结果表明,超声波/紫外光协同催化氧化要比单独超声波或光化学处理效果显著,证实了声光联合技术具有明显的协同效应.     

NaCl-KCl熔盐中TiB2阳极溶解和电化学还原行为研究

金属钛清洁提取是近年来的研究热点.提出了以TiB2为可溶性阳极,电解提取金属钛新方法.利用线性扫描、循环伏安和方波伏安等电化学测试技术,分析了TiB2在NaCl-KCl熔盐中的阳极溶解和电化学还原过程.结果表明,TiB2阳极可发生电化学溶解,其中钛被氧化为Ti3+进入熔盐中,而硼则被氧化为B单质.Ti3+迁移至阴极,发...     

氧化铌阴极微观结构对电脱氧制备铌的影响

采用电脱氧法,以Nb2O5烧结片为阴极,石墨棒为阳极,在CaCl2-NaCl混合熔盐中制备金属铌.分别研究了压制压力、烧结温度对阴极片微观结构和电脱氧反应及其产物的影响.实验结果表明,烧结温度和压制压力对Nb2O5烧结片的晶粒尺寸、孔隙度和孔隙尺寸具有明显的影响,从而影响到电脱氧的反应速率和效果.晶粒细、孔隙度高和连通性好的烧结氧化铌阴极能够提高电脱氧的反应速率和效果.研究表明,12MPa压制成型后经1 200℃烧结的阴极片,电脱氧效果最佳.     

熔盐电解法制备CaB6及阳极保护的实验研究

采用CaCl2-NaCl-B2O3体系在750℃,3.5 V槽电压下电解制备出CaB6晶体.对电解阴极产物进行了xRD与sEM及能谱的对比分析.结果表明,使用SiO2-B2O3-Na2CO3混合涂层对石墨阳极进行涂层保护处理,不仅有效减少了阳极的物理破损与化学腐蚀,还显著降低产物中的碳残留,提高了电流效率,可以获得较为理想的CaB6晶体粉末.     

直接电解法制取金属镝的阴极制备工艺研究

以直接电解脱氧法(FFC法)电解氧化镝制取金属镝工艺为主要研究范畴。实验以烧结Dy2O3试样为阴极,高纯石墨棒为阳极,于CaCl2熔盐中电解脱氧。结合电脱氧理论系统研究了试样的成型压力、烧结温度以及烧结时间对所得阴极电解过程及产物脱氧率的影响。同时,结合对各条件下阴极片体的微观形貌的分析结果及电脱氧产物XRD谱图分析,得到了阴极制备工艺的适宜条件。实验结果表明:直接电脱氧法制备金属镝工艺是可行的,微孔阴极中的颗粒连通性好、颗粒尺寸小、孔隙率高均有利于电脱氧进行。实验得到的最佳电极制备条件为:成型压力为15 MPa、烧结温度为1200℃、烧结时间为8 h。     

垃圾渗滤液催化氧化处理技术研究进展

催化氧化技术能有效降解垃圾渗滤液中的难降解有机物.本文对O3类催化氧化、Fenton类催化氧化、电化学氧化、UV/H2O2催化氧化、TiO2光催化氧化等技术的国内外研究进展和发展趋势进行了分析总结,并系统阐述了催化氧化技术降解垃圾渗滤液污染物的作用机理.同时,本文亦对各种新型催化剂的引入对垃圾渗滤液处理的效果进行了探讨,提出新兴高效催化剂的研发和合成是实现渗滤液催化氧化技术发展与应用的关键和核心.     

电脱氧法制取金属铌的研究

以Nb2O5粉末烧结片为阴极、石墨坩埚为阳极,在CaCl2-NaCl熔盐电解质中对Nb2O5阴极进行电脱氧,以制取金属铌。研究了Nb2O5粉末烧结阴极的制取,以及在熔盐电解质中电脱氧Nb2O5的工艺。研究结果表明,在熔盐电解质中电脱氧是通过熔盐电解质渗透到阴极片孔隙中,使Nb2O5粉末烧结片阴极形成良好的导电体,氧化铌被电离,氧离子通过熔盐电解质传导至石墨阳极坩埚,发生反应并以氧气析出。而阴极本身则发生铌离子还原,形成金属铌。研究表明,电脱氧速度和电脱氧效率与电解质与氧化铌接触面大小和电解温度有关,渗透性好、孔隙度高即接触面大的阴极片和高的电解温度将有较高的电脱氧速度和效率。     

纳米钨粉制备浸渍阴极基体的研究

采用常规钨粉、纳米钨粉和掺杂氧化钪纳米钨粉制备了浸渍阴极。利用扫描电镜、压汞仪等测试手段分析了阴极基体的微观结构,用水冷阳极二极管检测了阴极的发射性能。研究表明,采用纳米钨粉制备的阴极基体具有比常规阴极基体更细微的显微结构,阴极的直流发射电流密度为4.6 A/cm2,而常规阴极为4.13 A/cm2。掺杂氧化钪后,阴极的发射性能明显提高,其直流发射电流密度为5.31 A/cm2。     

Purification and characterization of nitrobenzene nitroreductase from Pseudomonas pseudoalcaligenes JS45

Pseudomonas pseudoalcaligenes JS45 grows on nitrobenzene as a sole source of carbon, nitrogen, and energy. The catabolic pathway involves reduction to hydroxylaminobenzene followed by rearrangement to o-amino-phenol and ring fission (S. F. Nishino and J. C. Spain, Appl. Environ. Microbiol. 59:2520, 1993). A nitrobenzene-inducible, oxygen-insensitive nitroreductase was purified from extracts of JS45 by ammonium sulfate precipitation followed by anion-exchange and gel filtration chromatography. A single 33-kDa polypeptide was detected by denaturing gel electrophoresis. The size of the native protein was estimated to be 30 kDa by gel filtration. The enzyme is a flavoprotein with a tightly bound flavin mononucleotide cofactor in a ratio of 2 mol of flavin per mol of protein. The Km for nitrobenzene is 5 microM at an initial NADPH concentration of 0.5 mM. The Km for NADPH at an initial nitrobenzene concentration of 0.1 mM is 183 microM. Nitrosobenzene was not detected as an intermediate of nitrobenzene reduction, but nitrosobenzene is a substrate for the enzyme, and the specific activity for nitrosobenzene is higher than that for nitrobenzene. These results suggest that nitrosobenzene is formed but is immediately reduced to hydroxylaminobenzene. Hydroxylaminobenzene was the only product detected after incubation of the purified enzyme with nitrobenzene and NADPH. Hydroxylaminobenzene does not serve as a substrate for further reduction by this enzyme. The products and intermediates are consistent with two two-electron reductions of the parent compound. Furthermore, the low Km and the inducible control of enzyme synthesis suggest that nitrobenzene is the physiological substrate for this enzyme.     

Effect of baking temperature and anode current density on anode carbon consumption

The electrolytic anode carbon consumption (CC) was studied as a function of anode baking temperature (BT) and anode current density in a closed laboratory cell, where the anode gas was absorbed and also monitored on a CO/CO₂ analyzer. The CC referred to Faraday’s law was determined from the weight loss of the anode, the carbon gasification (CG) from the amount of absorbed anode gas, and the formation of carbon dust (CD) by the difference. The CC decreased by about 9 pct per 100 °C increase in BT, and it increased with decreasing anode current density, particularly at low current densities. The CG and CD showed similar trends. The excess CG, which was attributed to the Boudouard reaction (CO₂ + C = 2CO), showed a relative decrease with increasing current density, although the overall rate of the reaction increased.     

镍元素对炭阳极反应活性的影响

考察了煅后焦中微量元素镍对炭阳极反应活性的影响,并对炭阳极的二氧化碳反应性、空气反应性进行了测试。结果表明,适量的镍元素可以改善炭阳极在CO2中的残极率、粉化率和质量损失率;也能提高炭阳极在空气中的残极率、粉化率和质量损失率。镍元素的添加对炭阳极的CO2反应性和空气反应性均有抑制作用,可改善炭阳极质量,降低炭阳极的额外消耗。     

铝棒低银铅合金表面陶瓷化复合阳极的制备与性能

为获得一种锌电积用低成本、低析氧电位和高催化活性的阳极,在铝棒表面通过挤压复合技术包覆Pb-0.2% Ag合金得到Al棒Pb-0.2% Ag阳极.在含氟的硫酸溶液中,通过阳极氧化在Pb-0.2% Ag合金和Al棒Pb-0.2% Ag合金阳极表面形成具有高催化性能的膜层,采用显微图像分析仪和数显显微硬度计表征了膜层的厚度及硬度,并通过电子拉伸试验对比了两种阳极的极限抗拉强度.采用X射线衍射、扫描电子显微镜、循环伏安法、阳极极化和交流阻抗法等技术手段研究了Al棒Pb-0.2% Ag与Pb-0.2% Ag阳极表面氧化膜层的物相、形貌以及电化学性能.结果表明:Al棒Pb-0.2% Ag阳极相比Pb-0.2% Ag阳极表面易生成致密较厚的氧化膜层,且膜层硬度提升了41.64%,其氧化膜层主要物相均为电催化活性良好的β-PbO₂.新型阳极的极限抗拉强度是传统阳极的1.3倍,大大改善了阳极材料的机械性能.阳极极化曲线数据显示Al棒Pb-0.2% Ag/PbO₂阳极在电积锌体系中具有较低的析氧电位(1.35 V vs MSE,500 A·m-2)和较高的交换电流密度(7.079×10-5 A·m-2).循环伏安曲线和交流阻抗数据显示Al棒Pb-0.2% Ag/PbO₂阳极具有较高的电催化活性、较大的表面粗糙度和较小的电荷传质电阻.在电积锌实验中,栅栏型Al棒Pb-0.2% Ag/PbO₂阳极相比传统Pb-0.2% Ag阳极平均槽电压下降了75 mV,而且大大减少了阳极泥的产生.      

Ir-Ta氧化物涂层阳极在硫酸盐电解溶液中的电化学行为

采用测量极化曲线等电化学方法研究了钛基Ir-Ta氧化物涂层阳极在酸性硫酸盐溶液中的电化学行为。结果表明:酸性硫酸盐溶液中Ir-Ta氧化物涂层阳极上的析氧反应发生电化学极化,但超电势远低于Pb阳极和Pb-Ag阳极而电催化活性好,可以显著降低电解能耗。溶液pH和电解温度升高,Ir-Ta氧化物涂层阳极上析氧反应的超电势降低;溶液中含有不同金属离子时析氧反应的超电势略有不同,但金属离子浓度不影响其超电势。Ir-Ta氧化物涂层阳极在1 mol/L H2SO4溶液和电流密度40000A/m2的条件下的强化寿命可达55天。     

铝电解用NiFe2O4型金属陶瓷惰性阳极的研究进展

介绍了国内外铝电解用NiFe2O4型惰性阳极材料的研究与开发进展情况,指出了该材料具有耐熔盐腐蚀、抗氧化和电阻率低等优点的同时也存在抗热震性能差和电连接困难等缺陷.此外,简要阐述了NiFe2O4型惰性阳极的主要制备工艺.     

PEM水电解用多层钛网析氧阳极制备及性能研究

以钛网为扩散层基体,氯铱酸为前驱体,采用浸渍-热解法制备了IrO₂/Ti 析氧阳极,进一步采用热压法制备膜电极.综合扫描电镜尧循环伏安尧交流阻抗尧单池性能曲线测试及阳极寿命强化测试,研究了不同层数钛网析氧阳极对性能及寿命的影响.结果表明院与单层钛网析氧阳极比较,采用双层钛网析氧阳极,积分电荷由84.27 mC/cm2 增至153.12 mC/cm2,电极电化学反应阻抗由7.38 Ω·cm2 降低至3.03 Ω·cm2,单池性能得到提升.寿命强化测试表明,采用双层钛网析氧阳极在稳定性及寿命方面有显著提升,稳定运行时间由30 h 增加到了53 h.      

Recent update on the PPAR alpha-null mouse

The most important commercially available nitro- and aminobenzenes and the explosive trinitrobenzene were tested for mutagenicity in the Salmonella typhymurium TA 98 and TA 100 both in the absence and presence of S 9. Ten of the 14 compounds tested (71%) were mutagenic. All the substances showed positive results in TA 98 and 4 substances were also mutagenic in TA 100. The three diaminobenzenes and 4-nitroaniline were mutagenic only with metabolic activation. All other compounds did not require the addition of S 9. Only nitrobenzene, 1,2-dinitrobenzene, aniline and 2-nitroaniline were negative in both strains. In summary, all substances that are derived from nitrobenzene or aniline by addition of a nitro group in the meta- or para-position were mutagenic, whereas nitrobenzene and aniline themselves and their ortho-derivates were nonmutagenic. The possible relationships between the position of the substituents and the mutagenicity are discussed.     

Effect of Acidogenic Stage on Aerobic Toxic Organic Removal

A laboratory investigation explored treatment of wastewaters containing nitrobenzene, biphenyl, and polynuclear aromatic hydrocarbons (PAHs) by two aerobic reactors, with and without acidogenic pretreatment. A sequencing batch operation was adopted for both acidogenic-aerobic and aerobic systems. Results indicated that nitrobenzene, biphenyl, and PAHs such as naphthalene and anthracene could be effectively removed by the acidogenic-aerobic system with removal efficiencies of more than 98% for nitrobenzene, 97% for biphenyl, and 96% for the PAHs, with a hydraulic retention time of the acidogenic stage at as low as 8 h. The acidogenic-aerobic system was therefore found to be effective in treating wastewaters containing such complex organics. The relatively low hydraulic retention time required for the acidogenic stage makes the process a potentially cost-effective technology.