锌电积用惰性阳极材料的研究现状

阐述了国内外铅及铅合金阳极、钛基二氧化铅阳极等锌电积用惰性阳极材料的研究现状,并对未来锌电积用惰性阳极材料的发展趋势进行了展望.     

锌电积用Pb-Ag-Bi阳极的电化学行为

制备了一种新型的锌电积用阳极Pb-Ag(0.8%,ω)-Bi(0～5.0%,ω),测试了该三元合金的电化学性能并与工业用Pb-Ag(0.8%,ω)阳极进行了对比.结果表明,阳极过电位随着合金中Bi含量的提高而降低,当Bi含量为1.0%(ω)和5.0%(ω)时,其阳极过电位比Pb-Ag(0.8%,ω)阳极分别低了40～50 mV和60～80 mV.用LSV法检测了阳极表面氧化膜的形成过程,并用XRD和SEM技术分析了膜的成分和形貌.2种阳极的表面氧化膜都主要由α-PbO2和β-PbO2组成,但具有不同的结构.与Pb-Ag(0.8%,ω)阳极相比,Pb-Ag(0.8%,ω)-Bi(1.0%,ω)阳极的表面膜结构更加规则、细致,但Pb-Ag(0.8%,ω)-Bi(3.0%,ω)阳极的表面膜又表现出与基体结合不紧密,呈疏松碎片状结构的特点.     

锌电积用惰性阳极材料的研究现状及发展趋势

综述了锌电积用惰性阳极材料的研究现状,着重阐述了锌电积用惰性阳极材料研究的主要改进方式:新型基体的使用,脉冲电镀和复合电镀技术的运用,梯度惰性阳极的制备,以及表面层掺杂.展望了未来锌电积用惰性阳极材料的发展趋势.     

铜电积用惰性阳极材料的研究现状

根据基体材料的不同,综述了国内外铜电积用惰性阳极材料的研究现状,重点阐述了铅及铅合金阳极、铅基涂层阳极、钛基涂层阳极等的制备、电化学性能及优缺点。     

Pb-Ag-SiC阳极在锌电积中的性能

为制备一种具有更高耐腐蚀性,高催化活性的锌电积阳极,在传统Pb-Ag[w(Ag)=0.25%]阳极表面用SiC进行活化处理得到Pb-Ag-SiC阳极。并通过电化学测试分析了Pb-Ag-SiC阳极在锌电积过程中的性能。阳极极化曲线和塔菲尔曲线的数据分析显示Pb-Ag-SiC阳极与传统Pb-Ag阳极相比具有更好的耐腐蚀性,阳极极化曲线和循环伏安曲线数据分析显示Pb-Ag-SiC阳极与传统Pb-Ag阳极相比具有更高的电催化活性。     

锌电积用PbO_2复合惰性阳极材料制备及性能研究

以3Cr13不锈钢为基体,在由PbO45g/L和NaOH160g/L组成的镀液中加入20g/LCeO2(平均粒径30nm)或/和20g/LB4C(平均粒径6μm),采用阳极电沉积的方法制备了α-PbO2–B4C、α-PbO2–CeO2、α-PbO2–CeO2–B4C等3种复合惰性阳极材料,观察了其表面微观组织特征,测试了其电沉积时的阳极极化曲线以及在ZnSO4–H2SO4溶液中的循环伏安曲线和塔菲尔曲线,并与纯α-PbO2电极进行了对比。结果表明,CeO2、B4C或其两者与α-PbO2的共沉积改变了阳极沉积电位和α-PbO2的电结晶形貌,使晶粒尺寸减小,并导致α-PbO2在ZnSO4–H2SO4溶液中的阴极还原峰电位正移,及有助于提高α-PbO2的耐蚀性。α-PbO2–CeO2和α-PbO2–CeO2–B4C复合惰性阳极材料分别在低电位区和高电位区具有良好的析氧电催化活性。     

电积用析氧阳极的研究进展

从铅阳极合金化、金属基复合阳极和其他新型阳极三方面综述了金属电沉积中析氧阳极材料的研究现状,展望了新型析氧阳极材料的发展趋势。指出新型阳极在降低电耗、推动金属电沉积行业发展方面具有重大意义。     

锌电积过程中聚苯胺/碳化钨阳极的结构变化及失效行为

研究了锌电积过程中聚苯胺/碳化钨(PANI/WC)阳极的结构变化和失效行为,采用加速电解寿命测试和仪器分析考察了PANI/WC阳极在锌电积过程中表面形貌和结构的变化. 结果表明,整个电解过程中槽电压从3.71 V降到3.57 V后急剧升高到10 V,即经历活化、稳定、迅速升高阶段. 随锌电积进行,阳极表面出现脱落、开裂,迅速进入失效阶段,而微观结构无明显变化. PANI/WC阳极失效主要是由包覆WC的PANI大量剥蚀而使WC裸露和阳极开裂导致的.     

Utilization of gas-diffusion electrodes catalysed with tungsten carbide as anodes for zinc electrowinning

Gas-diffusion electrodes with varying amounts of tungsten carbide catalyst are studied, and their feasibility as suitable anodes for zinc electrowinning is demonstrated. The energy savings achievable with the use of such anodes are evaluated.     

Corrosion rates of lead based anodes for zinc electrowinning at high current densities

The corrosion rates of anodes made from various lead/silver alloys have been determined during electrolysis in sulphuric acid solution, pure and containing additives, using current densities in the range 2500 to 10 000 A m^–2. An increase in acid concentration, and in some cases temperature, caused an increase in the corrosion rate. In the absence of manganese in the bath, the corrosion rate was effectively independent of current density in the range studied, whereas in the presence of manganese, the corrosion rate decreased with decreasing current density. The corrosion rates of various calcium, tin and thallium alloys of lead were also determined. The presence of chloride ions in the electrolyte increases the corrosion rate, whereas potassium ions and strontium carbonate have a negligible effect. Pre-treating silver/lead anodes with a solution of acidic potassium fluoride at 500 A m^–2 prior to testing markedly decreased the corrosion rate in the presence of manganese, but increased the corrosion rate with manganese absent. The effect of zinc on the corrosion rate in synthetic electrolyte solutions, with and without manganese present, has also been determined for silver/lead alloys at 10 000 A m^–2. At zinc levels over 1 M, the corrosion rate increased with and without added manganese. As the work has been undertaken in an attempt to improve the electrowinning of zinc, an electrolyte based on acidified industrial solution has also been tested. The rates observed were similar to those obtained for synthetic zinc-containing solutions.     

Electrochemical noise studies of the corrosion behaviour of lead anodes during zinc electrowinning maintenance

Following anodic polarisation of lead anodes with different silver contents (0.5-0.7%) during Zn electrowinning, the discharge and corrosion of lead anode during the decay period at open circuit potential in sulphuric acid bath have been studied by electrochemical noise analysis (ENA) method. Potential and current decay behaviour over 16 h shows 4 and 2 main characteristic regions, respectively. The wavelet transform has been employed to analyse the ENA data. The results of wavelets have demonstrated that energy distribution plot “EDP” was a powerful tool to provide useful information about the dominant process for different discharge and corrosion stages and mechanisms. The discharge is predominant than corrosion for all anodes for the regions I, II and III, and ENA feature of events changes from large timescale to low timescale, diffusion control or exfoliation to metastable pitting and pit growth, respectively. Region IV, only observed for 0.6% and 0.7%Ag, corresponds to general and metastable pitting corrosion under diffusion control. It has been found that anode containing lower silver content have more corrosion products even after 16 h of decay (discharge and attack dominated by pitting corrosion type with the highest corrosion due to the longest period of pitting during the 16 h).     

Influence of Co2+ and Mn2+ ions on the kinetics of lead anodes for zinc electrowinning

The influence of Co²⁺ and Mn²⁺ ions on the kinetics of lead and lead–silver alloy anodes is analysed using impedance spectroscopy and steady-state polarisation curves. With lead–silver anodes, increasing the Mn²⁺ concentration catalyses the oxygen evolution current by stimulating the reaction rate. Impedance data reveal a transient inhibition of the reaction, ascribed to the adsorption of a silver-salt containing manganese. The addition of Co²⁺ catalyses oxygen evolution, mainly on the pure lead anode. For lead–silver anodes, the small catalytic effect of Co²⁺ ions implies an increase in the Tafel coefficient for the oxygen reaction. The transient inhibiting process suggests the formation of a cobalt-containing adsorbate on the pure lead anode.     

Gas-diffusion electrodes catalysed with tungsten carbide as anodes for nickel electrowinning

The characteristics of gas-diffusion electrodes catalysed with tungsten carbide have been investigated under the conditions of nickel electrowinning. It is shown that their use as anodes in this process leads to a considerable decrease of the energy consumption and the nickel produced is free of heavy metal impurities.     

Performance of catalytically activated anodes in the electrowinning of metals

The performance of titanium anodes coated with oxides of Ir–Co or Ir–Ta has been compared using long term polarization techniques under simulated electrowinning conditions. Possible reasons for anode failure are explained from SEM and XRD. Potentiodynamic studies in 2m H2SO4 indicate that approximately 450mV reduction in anode potential can be achieved with Ti/(Ir–Co) as against lead. This anode is also suitable in chloride contaminated sulfate electrolyte. The anode potential measurements in different electrowinning electrolytes indicate that a potential saving up to 370– 420mV can be achieved. It is interesting to note that mixed electrolyte containing sulfate and chloride behaves similarly to pure chloride electrolyte with respect to anode potential.     

A validated mathematical model for a zinc electrowinning cell

A set of (95) equations forming a dynamic, nonlinear model of an industrial pilot-plant scale zinc electrowinning cell fed with high purity electrolyte is presented. Only the solution of the steady-state model is considered in this paper. Values for unknown model parameters have either been obtained from the literature or else estimated using experimental data taken from the pilot-plant cell. Sensitivity studies showed that uncertainties in the temperature dependency of the zinc and hydrogen reaction exchange current densities and the exchange coefficient for the hydrogen reaction have a major effect on the model predictions. Excellent agreement between predicted and experimental results was obtained, provided that cathodic mass transfer effects were included in the model. Both parameter estimation and solution of the steady-state model were carried out using the SPEEDUP flowsheeting package.