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Electrochemical behavior of mesh and plate oxide coated anodes during zinc electrowinning

Transactions of Nonferrous Metals Society of China 2016年第2期26卷 589-598页

作者：张伟 Michael ROBICHAUD edward ghali Georges HOULACHI 湖南工业大学冶金工程学院株洲412007 Department of Mining Metallurgy and Material EngineeringLaval UniversitySte-FoyQuebec G1K 7P4 Canada Hydro-Quebec Research Center Shawinigan Quebec G9N 7N5 Canada

The catalytic performance of two oxides coated anodes （OCSs） meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 ℃. Their electrochemical behaviors were compared with that of a conventional Pb-0.7%Ag alloy anode. Electrochemical measurements such as cyclic voltammetric, galvanostatic, potentiodynamic, open-circuit potential （OCP） and in situ electrochemical noise measurements were considered. After 2 h of OCP test, the linear polarization shows that the corrosion current density of the Ti/（IrO2-Ta2O5） mesh electrode is the lowest （3.37μA/cm^2） among the three OCAs and shows excellent performance. Additionally, after 24 h of galvanostatic polarization at 50 mA/cm^2and 38 ℃, the Ti/MnO2mesh anode has the highest potential （1.799 V）, followed by the Ti/（IrO2-Ta2O5） plate （1.775 V） and Ti/（IrO2-Ta2O5） mesh （1.705 V） anodes. After 24 h of galvanostatic polarization followed by 16 h of decay, the linear polarization method confirms the sequence obtained after 2 h of OCP test, and the Ti/（IrO2-Ta2O5） mesh attains the lowest corrosion current density. The Ti/（IrO2-Ta2O5） mesh anode also shows better performance after 24 h of galvanostatic polarization with the overpotential lower than that of the conventional Pb-Ag anode by about 245 mV.

关键词： oxides coated anode mesh plate electrochemical measurement electrochemical behavior

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Passive behavior of gold in sulfuric acid medium

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Transactions of Nonferrous Metals Society of China 2015年第6期25卷 2037-2046页

作者：张伟 Ahmet Deniz BAS edward ghali Yeonuk CHOI Department of Mining Metallurgical and Materials EngineeringLaval University Barrick Gold Corporation

Anodic behavior of pure Au as compared to platinum （Pt） in H2SO4 solutions was considered by different electrochemical techniques for an appropriate insight. Cyclic voltammetry studies showed two oxidation and one film reduction peaks for Au, while one oxygen evolution reaction for Pt. Increasing H2804 concentration （from 0.5 to 1 mol/L） caused 2-fold increases in peak current density of Au. Increase in agitation promoted passive zone of Au, while it was negligible for Pt by potentiodynamic studies. Potentiostatic studies （2 h） at three anodic passive potentials in 1 mol/L H2SO4 showed that the admittance of Au was found to be the lowest at 1.4 V. Electrochemical noise measurements during the decay periods （16 h） after polarization showed that the thin passive film formed during potentiostatic polarization has been dissolved.

关键词： gold passivation sulfuric acid electrochemical noise

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维普期刊数据库

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Active and passive behaviors of gold in cyanide solutions

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Transactions of Nonferrous Metals Society of China 2015年第10期25卷 3442-3453页

作者： Ahmet Deniz BAS Fariba SAFIZADEH Wei ZHANG edward ghali Yeonuk CHOI Department of Mining Metallurgical and Materials EngineeringLaval University Barrick Gold Corporation Suite 3700161 Bay Street P.O.Box 212 TorontoOntario M5J 2S1Canada

Active and passive behaviors of pure gold（Au） and roasted gold ore（RGO） electrodes were investigated at 25 °C in de-aerated agitated cyanide *** voltammetry and potentiodynamic polarization with agitation at 100 r/min in 0.04 mol/L NaCN solution showed different peak positions and current *** tests illustrate that the peak current densities increase greatly with increasing the cyanide *** the pH value from 10 to 11 resultes in a great decrease of current density,while it increases noticeably by decreasing the agitation from 100 to 60 r/*** the presence of oxygen,Au and RGO electrodes show different characteristics of peak positions and corrosion *** potentiostatic studies show that increasing the potential from 1 to 1.4 V at pH value of 11 results in an 80% decrease of current density while decreasing the pH value from 11 to 10 at 1 V gives a 1.7 fold increase of current density,possibly due to more effective passive *** polarization,electrochemical noise measurements（ENM） during decay periods show that Au results in more passive states at high potentials,showing pitting *** ENM results show that this technique can be a promising tool for a better understanding of gold *** XPS studies prove the presence of passive oxides.

关键词： pure gold roasted gold ore cyanide passivation electrochemical noise

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EFFECT OF FORMAMIDINE DISULFIDE ON THE CATHODE POLARIZATION BEHAVIOR OF COPPER CATHODE IN ACID COPPER SULFATE ELECTROLYTE AT 65℃

EFFECT OF FORMAMIDINE DISULFIDE ON THE CATHODE POLARIZATION ...

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21世纪重有色金属冶金高新技术及新材料国际会议

作者： Shize Jin edward ghali Guy St-Amant Department of Mining Metallurgical and Materials Engineering Laval University Sainte-Foy QC Canada G1K 7P4 Department of Mining Metallurgical and Materials Engineering Laval University Sainte-Foy QC Canada G1K 7P4 LTEE Hydro-Quebec 600 Avenue de la Montagne C.P. 900 Shawinigan QC Canada G9N 7N5

Formamidine disulfide (FDS) is a reaction product between cupric ion and thiourea (TU) formed in acid copper sulfate electrolyte during copper electroplating and electrorefining. It was reported that this oxidation product of TU produced a depolarization effect on copper cathodic process. In this work, it is observed that FDS gives a polarizing effect in lower current densities, but exhibits a depolarizing effect in higher current densities. The critical current density that separates the two current regions becomes higher when the FDS concentration in the copper solution increases. For a certain original concentration of FDS, the critical current density decreases with time after the FDS addition. Three methods (potentiodynamic technique, galvanostatic polarization and electrochemical ac impedance spectroscopy) are used for this study and the results obtained with these three methods are well in accordance with each other.

关键词： EFFECT OF FORMAMIDINE DISULFIDE ON THE CATHODE POLARIZATION BEHAVIOR OF COPPER CATHODE IN ACID COPPER SULFATE ELECTROLYTE AT 65

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