关于钢在酸性溶液中的钝化

在酸性溶液中,钢是活泼的,随着阳极过程的进行而发生腐蚀．但是,由于一些因素的作用,使阳级过程受到强烈的阻滞,同样可进入钝化状态．微酸性除铜钝化工艺是利用在亚硝酸钠－柠檬酸溶液中,钢的钝化区间扩大,钝化电流变小,钝化电位负移,同时铜溶解产生的强氧化电流使钢的阳极过程受到阻滞,从而进入钝化状态．     

镀镍溶液中铜杂质的快速测定

铜是镀镍溶液中有害杂质之一,其量一般不能超过0.02g/L,因而,必须经常加以测定。常用的双环已酮草酰二腙(BCO)法不适用,因为大量的Ni~(2+)也会同试剂反应,虽然无色,但消耗大量试剂,致使吸光度始终达不到正常的数值。铜试剂(DDTC)法也不适用,大量的Ni~(2+)同样干扰,虽然可以加入EDTA—Mg配位体缓冲掩蔽剂掩蔽Ni~(2+),但吸光度仍较正常值为低且不稳定,DDTC试剂的另一个缺点便是有毒,有难闻的气味,对于某些样品易发生浑浊,须增加一道氯仿萃取工序[1]。文献[2]采用氯仿萃取—络合滴定法测铜;文献[3]采用硫化氢沉淀重量法测铜;文献[1]还采用原子吸收分光光度法测定微量铜。上述方法不是操作冗长,便是要接触有机溶剂,或是     

镀镍溶液中铜杂质的分析方法

利用铜试剂与Cu2+生成黄棕色络合物的特效显色反应,用分光光度法测定镀镍溶液中的铜杂质.用EDTA掩蔽镍离子和铁离子,在氨碱性条件下显色,显色液pH≈9.2.以镀液底色作参比,在λ=450 nm处测定.实验表明,测定结果的相对平均偏差为2%,能够满足监控镀镍溶液中铜杂质的要求.     

酸性镀铜液中铜的测定

１　前　言基于Ｃｕ（Ⅱ）的氧化性测定铜,已有不少分析方法。根据Ｃｕ（Ⅱ）与ＥＤＴＡ形成配合物而建立起的滴定方法,以ＰＡＮ为指示剂,已应用于工厂镀铜液中铜的测定。ＰＡＮ作指示剂终点由蓝色变为绿色判断终点较难,滴定误差较大。用ＰＡＲ作指示剂,以标准ＥＤＴＡ滴定,终点由深红变为暗绿色易判断。该法简便、快速,用于酸性镀铜液中铜的测定,结果满意。２　实验部分２．１　主要仪器试剂ＥＤＴＡ标准溶液（分析纯）　０．０４３ｍｏｌ／ＬＰＡＲ４－（２－吡啶偶氮－间苯二酚）　称取０．１ｇＰＡＲ溶于１００ｍＬ乙醇中。氨性…     

纤维素铜氨溶液的溶解性能及流变性能

研究了纤维素在铜氨溶液中不同溶解条件下的溶解特性,以及纤维素铜氨溶液的流变性能。结果表明:当溶解温度为-10℃,Cu2+浓度为1.4 mol/L,溶解时间1 h时,纤维素在铜氨溶液中有较大的溶解度;纤维素铜氨溶液为假塑性流体,其黏度随温度的升高而降低,随纤维素含量的升高而增大,当纤维素含量较高时,其黏度随温度的变化幅度较大。     

退镀铜溶液中铜的测定

采用原子吸收分光光谱法建立了测定退镀铜溶液中铜的分析方法。分析了共存物质和高氯酸对铜测定的影响,进行了精密度分析及样品合成等试验。结果表明,共存物质硫酸对测定无影响,铬酸酐质量浓度超过40 g/L对测定有负干扰,加入高氯酸可消除影响。高氯酸可加热冒烟消除。该方法的相对偏差小于1.00%(n=5),此分析方法的精密度好、准确度高。     

酸性镀铜溶液中锌杂质的分析方法

在电镀生产中,监控镀液中金属杂质是十分必要的。制定了酸性镀铜溶液中锌杂质的分析方法。用碘量法测定硫酸铜,用EDTA容量法测定硫酸铜和锌杂质的总量,从总量中减去硫酸铜的量得到锌杂质的质量浓度。方法准确,能够满足监控酸性镀铜溶液的要求。     

金在碱性硫脲溶液中溶解的电化学动力学

研究了金在碱性硫脲溶液中阳极溶解的电化学行为及动力学. 结果表明,硫脲浓度由0增加至0.2 mol/L时,开路电势由-130 mV移至-280 mV,达到稳态的时间由400 s延长至800 s. 循环伏安曲线上正向扫描时700 mV的电流峰为金的阳极氧化峰,850 mV之后阳极电流急速上升为氧气的大量析出,反扫时220 mV处为溶液中金离子的还原峰. 溶液中加入硫脲使金的阳极氧化峰电势负移了30 mV,峰电流则提高了15.5倍. 由于硫脲的分解及其产物对金电极表面的钝化,硫脲浓度由0.05 mol/L增加至0.20 mol/L时,阳极峰电势由655 mV负移至480 mV,峰电流则由1.985 mA降至0.09528 mA. pH值升高有利于金在碱性硫脲溶液中的阳极溶解. 温度由25℃升高至35℃时,峰电流由0.761 mA迅速增加至4.387 mA,峰电势由655 mV负移至596 mV,有利于金的溶解;但温度太高会增加硫脲自身的氧化分解. 金的阳极溶解为不可逆电荷转移反应.     

酸性镀锌溶液中氯化锌的分析方法

制定了测定酸性镀锌溶液中氯化锌的新方法。在pH=5.4的条件下用抗坏血酸掩蔽镀液中的亚铁离子,用氟化铵掩蔽铝离子,用硫脲掩蔽铜离子,以二甲酚橙作指示剂,用EDTA标准滴定溶液滴定锌。实验表明,本法的相对平均偏差为0.09%,回收率为99.24%,精密度和回收率都较高。     

电化学诱发羟基自由基降解水中酚类污染物

DMPO（5,5-dimethyl-1-pyrroline-N-oxide）为自旋捕集剂,采用电子自旋共振技术（electron spin resonance spectroscopy,ESR）直接证实了经氟树脂改性的β PbO₂阳极和不锈钢网阴极构成的电化学体系中产生的羟基自由基（·OH）。通过电化学氧化水中含酚类及其前驱体污染物,发现环状结构化合物受电化学产生的羟基自由基攻击而发生开环反应产生易生物降解的有机酸,如反丁烯二酸和草酸,直至完全矿化为CO₂和水分子,苯醌是酚类污染物开环前产生的共同稳态中间体。该类污染物的电化学降解共性规律为电化学氧化技术的工业化应用和提高其处理工艺的经济性提供了理论依据。     

Peroxyl and hydroxyl radical scavenging activity of some natural phenolic antioxidants

The autoxidation of linoleic acid dispersed in an aqueous media and the antioxidant effect of hydroxytyrosol, oleuropein, caffeic acid and tyrosol were studied. Linoleic acid autoxidation rate was estimated by the increase of conjugated diene level and by the decrease of linoleic acid content in the samples. The phenolic compounds exhibited an antioxidant activity which increased in the order: tyrosol < caffeic acid < oleuropein < hydroxytyrosol. The analysis of the hydroperoxide isomers pointed out that hydroxytyrosol, oleuropein and caffeic acid at a concentration of 10⁻⁴M inhibited the formation oftrans- trans isomers in the increasing order: caffeic acid < oleuropein < hydroxytyrosol. This inhibition could be related to the ability of phenolic compounds to scavenge peroxyl radical. Tyrosol did not inhibit the formation oftranstrans isomers. Phenolic compounds were degraded as a consequence of their antioxidant activity and their degradation rate was positively correlated to their antioxidant efficacy. These phenolic compounds, at a concentration of 6 × 10⁻³M, also scavenged hydroxyl radical, with an efficiency which increased in the order: tyrosol < hydroxytyrosol < oleuropein < caffeic acid. Polar substituents at the para position, such as in caffeic acid and oleuropein, were correlated with higher hydroxyl radical quenching ability.     

羟自由基化学发光体系测定抗坏血酸

研究发现,铁(Ⅲ)与过氧化氢在酸性条件下生成羟自由基(·OH),羟自由基(·OH)和罗丹明6G(Rh6G)混合可以产生微弱的化学发光,抗坏血酸可以增敏其微弱化学发光,结合流动注射技术,建立了一种新的抗坏血酸化学发光分析法.增敏的化学发光强度与2.0×10-6～8.0×10-4 mg/mL范围内的抗坏血酸呈良好线性,检出限为1×10-6 mg/mL(3σ),对5.0×10-5mg/mL的抗坏血酸平行测定11次,其相对标准偏差为3.1%.文章最后对其反应的可能机理进行了探讨.     

Use of a PbO2 electrode of a lead-acid battery for the electrochemical degradation of methylene blue

In this work, the electrochemical degradation efficiency of synthetic azo dye, methylene blue, at positive electrode PbO₂ of lead-acid battery was investigated. The structure and morphology of the electrode was investigated by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectrometry. The influence of several operating parameters on electro-oxidation of 100 mL of methylene blue solution 100 mg/L was studied. Results indicated that lead-acid battery electrode is effective for removing color and chemical oxygen demand (COD). It is found that current density, the stirring speed, and the supporting electrolyte concentration have a positive effect on decolorization and mineralization, and no significant effect of the distance between the electrodes on methylene blue degradation and COD removal was observed. By contrast, the percentage of color and COD removal decreases with increasing of pH. Kinetic analysis of the results revealed that the COD removal follows a pseudo-first-order kinetics.     

The anodic dissolution of copper in hydrochloric acid solutions

The electrodissolution of copper in hydrochloric acid solutions at the rotating ring-disk electrode was found to be controlled by both mass transfer and reaction in the apparent-Tafel region in HCl concentrations of between 0.1 and 1.0 M. The proposed mechanism describes the adsorption of CuCl_ads on the corroding copper surface and the diffusion of CuCl⁻₂ from the copper surface. The reaction in the limiting-current region was found to be controlled by the diffusion of Cl⁻ to the copper surface through a porous CuCl layer that forms on the surface. The thickness of this porous layer is dependent on the stirring conditions, and independent of the Cl⁻ concentration. Cu²⁺ is also produced at the Cu surface during electrodissolution. A mechanism describing the formation of a porous film of CuCl on the surface, the diffusion of Cl⁻ through this film and the formation of Cu²⁺ has been proposed.     

间硝基苯甲酸在硫酸介质中的电还原特性

采用循环伏安法研究了硫酸介质中电极材料、扫描速度、反应温度和添加剂等对间硝基苯甲酸(mNBA)电解还原的影响。结果表明：在该体系中最合适的阴极材料为铜电极;在电还原过程中,随着扫描速度和温度增大,mNBA电还原反应的峰电流不断增大,其电极过程受扩散控制,电还原反应伴有不可逆随后化学反应;在溶液中加入无机盐SnCl2对mNBA的电解还原有明显的助催化作用。     

黄山贡菊提取物对羟自由基清除作用

采用邻二氮菲—Fe(Ⅱ) /H2 O2 体系产生羟自由基(·OH) ,用分光光度法(波长5 36nm)研究了黄山贡菊提取物对·OH的抑制和清除作用。结果表明:黄山贡菊提取物对·OH具有显著的抑制和清除作用。     

Production of nanoparticles of copper compounds by anodic dissolution of copper in organic solvents

The anodic behaviour of copper was investigated in ethanol solution containing LiClO₄, LiCl electrolyte and water. The type of electrolyte and the water content influences the mechanism of the anodic process and the formation of anodic products. In LiClO₄ electrolyte the dissolution of copper is related to the oxidation of Cu(I) to Cu(II). In solutions of LiCl the etching of copper begins with the creation of soluble complexes of Cu(I) with chloride ions and solvent molecules. At potentials above 0.4 V the formation of alkoxides was observed in both solutions, characterized by a yellow tint. On the other hand, above 0.8 V (i.e. above the equilibrium potential of alcohol oxidation) copper dissolution is accompanied by the formation of a blue colloidal suspension of Cu (II) copper salt. Anodic etching of copper in solutions containing 3% H₂O at potentials higher than 0.4 V leads to the formation of colloidal suspension of copper oxide nanoparticles.