Electrochemical behaviour and electrowinning of rhodium in acidic chloride solution

The electrochemical behaviour and recovery of rhodium in an acidic solution were investigated using a rotating disc electrode system and a modified electrochemical cyclone cell, respectively. The electrochemical polarization data indicated that the Rh³⁺ ions were reduced to metallic Rh below ?0.1 V, and the limiting current density for rhodium deposition was observed at around ?0.3 V (vs. SCE) with a diffusion coefficient of 6.3 × 10^?6 cm² s^?1 using the Levich equation. The effects of the applied voltage and the initial concentration of rhodium were examined using the modified cyclone cell, and more than 91 % of the rhodium in solution was recovered within 2 h under the optimal conditions.     

Preparation of aluminum ultrafine particles by anodizing aluminum foil in acidic electrolyte containing chloride ions

Anodization of aluminum in acidic electrolyte containing chloride ions was used to prepare aluminum ultrafine particles (Al UFPs) for the first time. In addition, the influence of different acid electrolyte was investigated and the mechanism of generating Al UFPs is analyzed. It is found that the pitting corrosion of chloride ions plays an important role in preparing Al UFPs and the acidification of the electrolyte is in favor of the preparation. Al UFPs with different shape and size distribution were obtained via changing the type of acid. Finally, the model of generating Al UFPs via this method is proposed.     

铟置换液制备聚硅酸氯化铝及其脱色性能研究

以铟置换液(Al2O3,质量分数为5.35%)和工业水玻璃为原料,以盐酸为活化剂和调节剂制备聚硅酸氯化铝絮凝剂,考察了聚硅酸氯化铝制备过程中铝硅比、pH、温度和陈化时间对脱色性能的影响.其优化工艺条件为:铝硅比为1,pH为1.8.聚合温度30℃,聚合时间14 h.在此条件下制得铝质量分数为1.13%、盐基度为51%的聚硅酸氯化铝净水剂.其对蔗渣造纸中段废水的脱色率为95%以上.     

Protection of copper surface in acidic chloride solution by non-toxic thiadiazole derivative

This paper deals with electrochemical properties of copper in the presence of the non-toxic compound 2-amino- 5-ethyl- 1,3,4-thiadiazole (AETDA) in acidic chloride solution. Electrochemical techniques: open circuit potential measurements, linear potentiodynamic measurements, cyclic voltammetry measurements and chronoamperometric measurements in addition to SEM–EDS analysis were used during the work. Results show that inhibition efficiency of 2-amino-5-ethyl-1,3,4-thiadiazole depends on inhibitor concentration and immersion time of copper electrode in inhibitor solution. Cyclic voltammetry and linear potentiodynamic measurements beside chronoamperometric measurements indicate formation of protective layer on copper surface. Moreover, results obtained by electrochemical measurements point out that the stability of formed layer depends primarily on the concentration of inhibitor and of potential values at which protective film is formed. Also, potentiodynamic measurements show that AETDA in acidic chloride solutions acts as mixed-type inhibitor. Inhibition mechanism of 2-amino-5-ethyl-1,3,4-thiadiazole includes adsorption of inhibitor on active sites on electrode surface which was confirmed by SEM–EDS analysis of the electrode surface. Adsorption of the AETDA in HCl solution obeys Langmuir adsorption isotherm.     

The application of electrochemical impedance techniques to aluminium corrosion in acidic chloride solution

Electrochemical impedance techniques are applied to the study of aluminium corrosion in hydrochloric acid solution in the passive region. Impedance spectra are obtained in stationary solution and in solution moving due to electrode rotation. The form of the spectra shows the importance of multistep dissolution, ionic migration through the oxide layer, relaxation effects and the influence of chloride ion.     

Voltametry and EQCM study of copper oxidation in acidic solution in presence of chloride ions

Cyclic voltametry experiments coupled with electrochemical quartz crystal microbalance (EQCM) measurements showed the corrosion mechanism of electrodeposited copper in presence of chloride ions. The oxidation of copper in acidic solution containing high concentration of Cl⁻ begins with formation of Cu⁺ ions. The Cu⁺ concentration at the vicinity of the electrode increasing, the small solubility product of CuCl is then exceeded, leading to a CuCl precipitation on the gold covered quartz crystal used as working electrode. For highest anodic potentials, the oxidation of electrodeposited copper or CuCl precipitate phases could occur. A combination with structural techniques like SEM, EDAX, AFM and DRX gives insight into the morphology and the nature of these CuCl precipitates.     

Corrosion resistance of aluminum oxide film and electrolytically coloured film in sodium chloride solution

The main interest of this study is to compare the corrosion resistance of aluminum anodic oxide film anodized in sulfuric acid bath with that of preanodized and electrolytically coloured film.Examinations have been carried out referring to (1) potentiostatted polarization curves shown on the specimens in 0.5 M sodium chloride solution, (2) impedance diagrams of the specimens and barrier thickness by Hunter's method and (3) optical metallographical observations of the aspects of pitting corrosion which took place on these specimens, and dipping test in corrosive solution.The results obtained are summarized as follows: (1) Typical difference was observed in regard to the potentiostatted polarization curves (i-t curves) between the two types of specimens in 0.5 M sodium chloride solution. The corrosion current caused by pitting corrosion of the electrolytically coloured specimens was smaller than that of anodized ones on the measurement by i-t curves. (2) The survey through the interfacial impedance diagrams of the specimens made clear that the impedance of the electrolytically coloured film was larger than that of uncoloured anodic oxide film, especially this greater increasing part of impedance was achieved in 15 s. This tendency was similar for the measurement of barrier thickness by Hunter's method. (3) The optical metallographical observations have demonstrated that there were far more advanced pitting corrosion on the anodic oxide film than on the electrolytically coloured film. In the dipping test, uncoloured anodized aluminum showed high extent of pitting corrosion, while electrolytically coloured aluminum performed well during colouring. So the total result of above examinations reveals that electrolytically coloured films are definitely more resistive to corrosion than anodic oxide films and this is due to the thick barrier layer of the former films.     

钛及其合金在氯化钠溶液中的腐蚀

分析了不同工况(如浓度、温度、p H值)下,钛及其合金在氯化钠盐水溶液中的腐蚀情况,并给出它们在氯碱工业盐水系统的使用建议。     

我国聚氯化铝的生产技术与质量控制问题

聚氯化铝是目前使用最广泛的高效混凝剂,具有用量少、产生污泥少、除浊效率高、对出水p H影响小等优点,在技术和原料方面都有很大优势。根据我国水处理行业对该产品的要求及其在水处理中的实际应用情况,从重金属含量、盐基度和不溶物含量出发,对聚氯化铝的生产技术和质量控制问题进行分析,并提出了关于国家标准方面的改进意见。     

Effect of aluminum chloride and Pt/ TiO2 on the thermal degradation of poly(vinyl chloride) in solution

The effect of two catalysts, Pt/TiO₂ and aluminum chloride, on the degradation of poly (vinyl chloride) (PVC) in solution was investigated at various temperatures. The molecular weight distribution of the polymer was obtained by analyzing the samples by gel permeation chromatography. Experimental data indicated that the catalysts enhanced the degradation rate of PVC compared to the thermal degradation of PVC. Continuous distribution kinetic models were used to evaluate the degradation rate coefficients. The activation energy, calculated from the temperature dependence of rate coefficients, was 26.5, 31.5, and 43.7 kcal/mol for the thermal degradation of PVC in solution, in the presence of Pt/TiO₂ and in the presence of AlCl₃, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3532–3535, 2003     

利用酸性含铝废液制备工业硫酸铝

采用活性白土工艺废酸液补加硫酸和铝矾土的方法制备工业硫酸铝,既消除活性白土工艺废酸液排放造成的污染问题,又回收了废酸液中的硫酸和硫酸铝。通过实验得到最佳工艺条件：pH=3.0、铝矾土量为每100 mL废酸液加入15 g、浓硫酸用量为10%（质量分数）。研究了结晶法与硫化钡法除铁,可分别得到硫酸铝产品,一等品中Al2O3和Fe3+的质量分数分别为16.5%（±0.06%）和0.095%（±0.18%）,合格品中Al2O3和Fe3+的质量分数分别为16%和0.308%,符合标准HG/T 2225-2010中工业硫酸铝Ⅱ类产品质量指标要求。     

Pitting corrosion of friction stir welded aluminum alloy thick plate in alkaline chloride solution

The pitting corrosion of different positions (Top, Middle and Bottom) of weld nugget zone (WNZ) along thickness plate in friction stir welded 2219-O aluminum alloy in alkaline chloride solution was investigated by using open circuit potential, cyclic polarization, scanning electron microscopy and atomic force microscope. The results indicate that the material presents significant passivation, the top has highest corrosion potential, pitting potential and re-passivation potential compared with the bottom and base material. With the increase of traverse speed from 60 to 100 mm/min or rotary speed from 500 to 600 rpm, the corrosion resistance decreases.     

Electrochemical study of corrosion behavior of graphene coatings on copper and aluminum in a chloride solution

Electrochemical characteristics and corrosion behavior of graphene coatings on Cu and Al in a 0.1 M NaCl solution were investigated. The graphene coatings were deposited on a Cu surface by chemical vapor deposition. Multiple graphene layers were then mechanically transferred from the growth substrate, Cu, onto Al surface by a transfer technique. The corrosion stability of graphene coatings was determined by electrochemical impedance spectroscopy and open circuit potential, while the corrosion rate was evaluated using potentiodynamic sweep measurements. Surface morphologies of the graphene coatings were analyzed by scanning electron microscopy and energy dispersive spectroscopy. Obtained results indicate that Cu coated with graphene grown using chemical vapor deposition shows corrosion-inhibiting properties in 0.1 M NaCl. On the other hand, Al coated with a multilayer graphene film mechanically transferred from the Cu surface exhibits electrochemical characteristics similar to an Al oxide on bare Al. Better protective properties of graphene coating on Cu compared to the graphene coating on Al were observed, probably due to the breakage of Al oxide film, causing the corrosion of Al to proceed rapidly in the presence of chloride electrolyte.     

Pyridine and its derivatives as inhibitors of aluminium corrosion in chloride solution

Pyridine and its selected derivatives (symmetric collidine and 2,5-dibrompyridine) have been studied as corrosion inhibitors for high purity aluminium in a 2m NaCl solution at 25°C and 35°C using d.c. polarization techniques. The investigations were carried out with a wide range of concentrations of the compounds examined (from 0.5×10–5m to 1×10–3m). The results show that the derivatives are adsorbed on aluminium according to the Freundlich isotherm. The values of the standard free energy of adsorption suggest that the adsorptive properties of the compounds under consideration approach the physical type. The polarization curves show that the compounds act as cathodic-type inhibitors.     

Effect of heterocyclic organic inhibitors on corrosion behavior of aluminum in 3.5% sodium chloride solution

添加有机缓蚀剂可以减缓或防止铝合金在3.5%NaCl溶液中的腐蚀。用失重法和电化学法分别研究了7种有机化合物对7075铝合金在3.5%NaCl溶液中的缓蚀行为,并用扫描电子显微镜(SEM)对铝合金样品在不同缓蚀介质中的腐蚀形貌进行了观测。失重法实验结果和Tafel极化测试结果均表明,这些有机化合物对铝合金有不同程度的缓蚀作用,其中7-氮杂吲哚的缓蚀效果最好,通过对铝合金样品表面孔蚀特征及电化学测量结果的分析,确定其缓蚀机理为阳极过程控制为主的成膜缓蚀剂。     

Inhibition of copper corrosion in acidic chloride solution by methionine combined with cetrimonium bromide/cetylpyridinium bromide

Methionine (MET) is non-toxic and easily biodegradable so that it is an alternative corrosion inhibitor in the water treatment and industrial pickling process. In this article, the inhibition behavior of MET combined with cetrimonium bromide (CTAB) and cetylpyridinium bromide (CPB) for copper corrosion in 0.5 M HCl solution has been investigated by using the electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and polarization curve methods. It shows that combination of MET with CTAB or CPB improves the inhibition performance effectively, and produces strong synergistic inhibition effect. The combined inhibitors suppress cathodic reaction and shift the corrosion potential toward more negative values. The mixed CTAB/MET has a better synergistic effect compared with the mixed CPB/MET. The quantum chemical parameters were calculated by PM3 semi-empirical quantum method. The better synergistic inhibition between MET and CTAB is attributed to their stronger electrostatic interaction.     

降低氯化钕溶液中铝离子的工艺研究

由于采购的稀土精矿品位的下降,稀土精矿中铝含量的增加影响了稀土产品的质量,稀土氯化钕溶液中铝离子的增幅高达5-7倍。为了降低稀土产品中铝的含量,通过正交实验,对影响氯化钕溶液中铝离子的主要因素进行分析,确定出3个控制因素,即氯化钕溶液的温度、絮凝剂的加入量、碳酸氢铵的加入量。得出的最佳工艺条件是：将氯化钕溶液的温度控制在55-60℃,絮凝剂加入量控制在0.1 g/L,碳酸氢铵的加入量（碳酸氢铵相对于沉淀出的稀土氧化物的质量分数）控制在5%左右。在此工艺条件下得到的沉淀物为胶状的白色沉淀氢氧化铝,氯化钕溶液经陈化、过滤可除去氢氧化铝。此工艺生产出的氧化钕中三氧化二铝质量分数〈0.0005%,达到了氧化钕产品的质量要求。     

Intercalation of carbons by aluminum chloride

A technique is described which will distinguish between the amount of AlCl₃ that is intercalated by a carbon and the amount that adds in other ways. The method is applied to a variety of carbons and the results are compared with those reported for the reactions of K-Cs vapors with these same carbons.     

餐厨垃圾酸性发酵及其产物的脱氮特性研究

利用餐厨垃圾为基质进行酸性发酵并利用其发酵产物作为反硝化碳源,结果发现餐厨垃圾酸性发酵过程中具有明显的阶段性。利用不同阶段的发酵液作为反硝化碳源,得出以乳酸为主的发酵液与乙酸钠相似,具有良好的反硝化能力和较快的反硝化速率的结论。而以VFAs为主的发酵液能够彻底实现反硝化,但容易导致NO2--N积累。