电化合成DL-高半胱氨酸硫内酯盐酸盐

DL-高半胱氨酸硫内酯盐酸盐是有用的生化试剂,一般用锡和盐酸还原高胱氨酸来制备,但为了除尽产物中的锡离子,必须通入H_2S气体,操作既麻烦,又有碍于人体的健康。Allen等曾报道,在碱性介质中用恒电位电解还原可制备高半胱氨酸的盐。我们试验了在盐酸介质中,用恒电流电解还原直接制备高纯度DL-高半胱氨酸硫内酯盐酸盐的方法。操作更为简便。     

电位滴定法测定钒储能介质中钒(Ⅲ)和全钒

正在全钒氧化还原液流电池体系中,钒储能介质既是能量转换介质更是能量储存的载体,是电池的核心组成之一。钒(Ⅱ)极易被空气氧化,钒(Ⅴ)只能通过电解氧化获得,而且不稳定、易析出~[1],因此通常不以钒(Ⅱ)或钒(Ⅴ)的状态生产、存储钒储能介质;钒(Ⅲ)和钒(Ⅳ)易生产获得,而且稳定性好,所以钒储能介质的初始状态通常为钒(Ⅲ)、钒(Ⅳ)的混合状态,理论上正、负极钒储能介质的初始综合价态为     

Fe(Ⅲ)-草酸-葡萄糖酸钙媒质体系间接电化学还原及棉织物染色的研究

应用循环伏安法研究了Fe(Ⅲ)-草酸-葡萄糖酸钙媒质体系的电化学行为及其可能的反应机理,实验表明Fe(Ⅱ)-葡萄糖酸盐起着最终的还原作用。电解还原时间、工作电压和阴极面积这三个因素影响着电流效率,在Fe(Ⅲ)-草酸-葡萄糖酸钙媒质体系中,还原大红R的电流效率最高可达89%,其电解还原时间10min,工作电压4V,阴极面积40cm2。     

Dy(Ⅲ)离子在LiCl-KCl熔盐中的电化学行为及Dy-Ni金属间化合物的选择性制备

采用循环伏安、方波伏安和开路计时电位等电化学方法研究了Dy(Ⅲ)离子在LiCl-KCl 共晶盐中的电化学行为及Dy-Ni 合金形成的电化学机理. 循环伏安和方波伏安法研究表明, Dy(Ⅲ)离子的电化学还原过程为三个电子转移的一步反应. 与惰性W电极相比, Dy(Ⅲ) 离子在Ni 电极上的循环伏安曲线多出了三对氧化还原峰,是由于Dy与Ni 形成了合金化合物, 导致Dy(Ⅲ)离子在活性Ni 电极发生了欠电位沉积. 采用X射线衍射(XRD)和扫描电子显微镜(SEM)附带能量散射谱(EDS)对恒电位(-1.6, -1.8 和-2.0 V)电解制备的Dy-Ni 合金进行分析, 分别获得了DyNi₅, Dy₂Ni₇和DyNi₂金属间化合物. 实验结果表明, 通过控制电位进行恒电位电解可以有选择性地制备不同的金属间化合物.     

mCMC-PEG-CS双极膜在电还原制备巯基乙酸中的应用

以Fe3+改性羧甲基纤维素(CMC)和聚乙二醇(PEG)共混物为阳膜, 以戊二醛改性壳聚糖(CS)和聚乙二醇共混物为阴膜, 制备了mCMC-PEG-CS双极膜, 并将其用作电解还原制备巯基乙酸(TGA)电解槽中阴阳两室间的隔膜. 以硫代硫酸钠法合成的巯基乙酸(TGA)和二硫代二乙酸(DTDGA)混合物为原料, 研究了酸浓度、温度及电解电流密度对电还原DTDGA制备TGA的生成量和电流效率的影响. 实验结果表明, 在TGA初始合成质量分数为2.79%, 电流密度为10 mA/cm2, 35 ℃电解时, 阴极室电还原产物巯基乙酸的电流效率为74.69%, 电解过程中的平均电流效率为54.02%. 与传统的金属还原法还原DTDGA制备的TGA相比, 不仅避免了昂贵的金属还原剂锌的消耗, 而且消除了反应副产物锌泥对环境的污染.     

在LiCl-KCl共晶熔体中电化学制备钬镍金属间化合物(英文)

采用循环伏安、方波伏安和开路计时电位等方法研究了Ho(Ⅲ)离子在LiCl-KCl共晶熔体中的电化学行为及Ho-Ni合金化机理。在惰性W电极上,Ho(Ⅲ)离子在-2.06 V(vs Ag/Ag Cl)发生电化学还原,该还原过程为3个电子转移的一步反应。与惰性W电极上的循环伏安相比,Ho(Ⅲ)离子在活性Ni电极的循环伏安曲线上还出现了3对氧化还原峰,是Ho与Ni形成了金属间化合物,导致了Ho(Ⅲ)离子在活性Ni电极发生了欠电位沉积。在不同的电位进行恒电位电解制备的3个不同的Ho-Ni合金,采用X-射线衍射(XRD)和扫描电子显微镜-能谱仪(SEM-EDS)等测试手段进行表征,结果表明:制备的3种合金分别是Ho2Ni17,Ho Ni5和Ho Ni23种合金化合物。     

Cu(II)在对甲苯磺酸铜＋DMSO中的电还原

制备了对甲苯磺酸铜并首次用于电化学实验.差示扫描量热和热重曲线测定表明，对甲苯磺酸铜结晶容易脱除全部结晶水，无水盐在空气中不潮解.用循环伏安曲线、计时电流曲线和恒电流电解后的电位-时间曲线研究Cu(Ⅱ)在二甲基亚砜(DMSO)溶液中的电还原.结果表明, Cu(II)电还原为Cu的反应分两步进行，其中第一步是可逆过程.测定了Cu(II)在DMSO溶液中的扩散系数.     

碳载钴酞菁催化剂的一步法制备及其在碱性条件下对氧的电催化还原

通过固相加热,一步合成了以VulcanXC-72(碳黑)为载体的碳载钴酞菁(CoPc/C)复合催化剂,其可用作空气电极的氧还原催化剂。通过X射线衍射、红外光谱等测试技术对催化剂进行了表征。利用极化曲线和交流阻抗(EIS)方法测试了其在碱性介质(6mol/LKOH)中对氧还原的催化性能。结果显示,得到的产物为CoPc/C复合物,平均粒径30nm。以磷酸处理的碳黑为载体,在600℃下制备的CoPc/C复合催化剂表现出最佳的催化活性。以其制备的电极在空气气氛下-0.03V(Hg/HgO)电位时即可产生明显氧还原电流,-0.2V时电流密度达90×10-3A/cm2。     

薄层光谱电化学方法研究[Ag(lO_6)_2]~(7-)和[Cu(lO_6)_2]~(7-)的阴极还原

在碱性介质中只有少数氧化剂如Ag(Ⅲ)及Cu(Ⅲ)仍有较强的氧化性,因此研究Ag(Ⅲ)、Cu(Ⅲ)络合物阴极还原的电极电势、电子转移数及还原机理,对于深入了解它们作为氧化剂时的氧化还原特性是有帮助的.本文用薄层光谱电化学方法测定了二过碘酸合银(Ⅲ)、络离子在不同pH条件下还原反应的E~0′和电子转移数(n),并由此推断阴极还原反应机理,还用同样方法研究了二过碘酸含铜(Ⅲ)络离子的阴极还原.     

Ti表面修饰纳米TiO2膜电极的电催化活性

用电化学合成法在Ti表面修饰一层纳米TiO₂膜,TEM和XRD测试表明晶型为锐钛矿型,晶粒平均尺寸为25nm.用循环伏安法、循环方波伏安法和电解合成法研究了纳米TiO₂膜电极在硫酸介质中的氧化还原行为以及对硝基苯还原的电催化活性。结果表明,纳米TiO₂膜电极具有异相氧化还原催化行为,膜中的Ti(Ⅳ)/Ti(Ⅲ)作为媒质间接电还原硝基苯为对氨基苯酚,收率和电流效率分别达91.6%和95.2%.     

Preparation of uranium(III) by mercury cathode electrolysis and its absorption spectra in hydrochloric acid solution

The reduction of hexavalent to trivalent uranium by mercury cathode electrolysis in hydrochloric acid solution was investigated. The dependence of the reducton ratio on the different media, the acid and uranium concentrations, and on the time of electrolysis was determined. It was found that hexavalent uranium can be reduced quantitatively to trivalent state by mercury cathode electrolysis. The absorption spectra of U(III) and U(IV) in 1M and 9M hydrochloric acid solutions were examined. The molar extinction coefficient of U(III) at 521 nm was 16.7 m²·mol^–1 within the HCl concentration range of 0.5–4.5M. U(IV) practically does not interfere in the photometric determination of U(III) at this wavelength. A good linear dependence of absorbance on the concentration of U(III) was found.     

An experimental investigation of uranium redox reactions in an electrolytic cell with a cation exchange membrane

This paper investigates the simultaneous reduction and oxidation reactions of uranium in hydrochloric acid media. The redox reactions were carried out in a cell fitted with a cation exchange membrane and hexavalent uranium was reduced to the tetravalent state in the cathode chamber. The reverse reaction was carried out in the anode side of the cell. The reaction rate was found to be independent of the uranium concentration and the extent of reaction was linear with time. There is evidence of uranium flux across the membrane.     

Coulometric determination of chromium

This paper describes an accurate and precise method for the determination of chromium by coulometry at controlled potential. A solution of the sample in 6M hydrochloric acid is electrolyzed at a large stirred mercury cathode whose potential is maintained constant at —1.10 V vs. S.C.E. ;this reduces the chromium quantitatively to the +2 state. Copper, lead, and a number of other elements are next eliminated by simply discarding the mercury and replacing it with fresh mercury ;then uranium is re-oxidized to non-interfering uranium(IV) by a second controlled-potential electrolysis at —0.80 V vs. S.C.E.; and finally the solution is electrolyzed at a working electrode potential of —0.40 V vs. S.C.E. This serves to re-oxidize the chromium quantitatively to the +3 state, and the analysis consists of measuring the quantity of electricity consumed in this oxidation.Of the elements commonly associated with chromium, only vanadium (and, when it is present in large amounts, molybdenum) interfere in this procedure.     

进口铜精矿中砷和汞的快速测定

试料经盐酸、硝酸溶解,添加硫脲和抗坏血酸预还原砷,以2%盐酸为载流,1%硼氢化钠和0.5%氢氧化钾溶液为还原剂,在氢化物发生器中,砷与硼氢化钠、盐酸反应生成砷化氢,汞则成为汞蒸气,用氩气导入石英炉原子化器中原子化,以空心阴极灯为激发光源,于原子荧光光谱仪上测量砷和汞的荧光强度。砷的标准偏差为0.0096%;汞的标准偏差为0.00015%,结果准确度较好。方法前处理快速,试剂消耗少,过程简单。     

Extraction of boric acid from breccias of mud volcanoes

Possibility of electrodeposition of gold(III) from dilute solutions of various mineral acids and ammonia by membrane electrolysis in recovery of gold from hydrochloric acid solutions was studied. The effect of the composition of the cathode solution and main electrolysis parameters on the rate of transport and electrodeposition of gold(III) was examined. The optimal process conditions were determined.     

Electrodeposition of gold(III) from cyanide-free electrolytes in membrane systems

Possibility of electrodeposition of gold(III) from dilute solutions of various mineral acids and ammonia by membrane electrolysis in recovery of gold from hydrochloric acid solutions was studied. The effect of the composition of the cathode solution and main electrolysis parameters on the rate of transport and electrodeposition of gold(III) was examined. The optimal process conditions were determined.     

Electrochemistry of uranium in ionic organic media: Ethylammonium nitrate and acetamide-KSCN eutectic

The electrochemical reduction of hexavalent and tetravalent uranium is investigated in ethylammonium nitrate at 298 K and in the acetamide-KSCN eutectic at 400 K. The transient techniques describe a two-step reduction of UO ₂ ²⁺ in acetamide-KSCN while only one step is observed in ethylammonium nitrate. The reduction of tetravalent uranium proceeds in one step giving trivalent uranium in the two media. In any cases, additional kinetic phenomena are the source of difficulties for the understanding of the reactions. In controlled potential electrolysis, side-reactions between the reduced species and the solvent impede completely the mechanism foreseen by transient methods.     

Determination of U(IV) and U(VI) by ion chromatography-inductively coupled plasma mass spectrometry and its application to kinetic studies

The ions normally formed by actinides in aqueous solutions by the oxidation states III-VI are M3-, M4+, MO2+ and MO2(+2), respectively. Oxidation state representatives such as Am3+, Th4+, NpO+ and UO+, which resist oxidation state changes, were used to investigate a method to separate the oxidised species (MO2 and MO2(2+)) from the reduced species (M3+ and M4+). With this method the hexavalent state of uranium could be separated from the tetravalent state of uranium in aqueous media in less than 8 min. Uranium concentrations down to 10(-9) M could be analysed without changing the redox composition during the separation. The oxidation kinetics of the tetravalent uranium for different hydrochloric acid concentrations was investigated. The measurements showed good agreement with values found in the literature, although the uranium concentrations were one million times lower.     

Volumetric determination of small amounts of uranium : Chromous chloride as reducing agent

A volumetric method is proposed for the rapid determination of small amounts of uranium. The hexavalent uranium is reduced to the quadrivalent state by chromous chloride, the excess of which is destroyed by air oxidation. A low potential redox indicator is used to follow the reduction and air oxidation. Ferric sulphate is added to the solution and the resulting ferrous ion titrated with dichromate solution.     

Polarographic behavior of uranium(VI) in malonic acid media determination of uranium in plutonium

The polarographic behavior of the uranium-malonate complex was investigated over the pH range 1.1–6.5. A reversible, one-electron wave was obtained. Below pH 4.9, the rate of disproportionation is nearly instantaneous and gives rise to a pseudo uranium(VI)-uranium(IV) reduction. Above pH 4.8 the concentration of uranium(V) is stable with respect to disproportionation. The half-wave potential is pH-dependent below pH 4.9, but it is independent of the malonate concentration above O.1 M. The diffusion current constant is 2.78 for the conditions described. A procedure for the determination of uranium in plutonium was developed for uranium concentrations greater than 225 p.p.m. Of 21 common impurities found in plutonium metal, only Cu, Fe, Pb, Sb and Ti cause significant interference ; titanium can be removed by ion exchange, and the other interferences by mercury cathode electrolysis.