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| KINETICS OF ANODIC CONVERSION OF GALENA TO LEAD CARBONATE IN AMMONIUM CARBONATE SOLUTIONS |
| CAO Changlin;GONG Qian;CHEN Jiayong Institute of Chemical Metallurgy;Academia Sinica;Beijing |
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Cite this article:
CAO Changlin;GONG Qian;CHEN Jiayong Institute of Chemical Metallurgy;Academia Sinica;Beijing. KINETICS OF ANODIC CONVERSION OF GALENA TO LEAD CARBONATE IN AMMONIUM CARBONATE SOLUTIONS. Acta Metall Sin, 1985, 21(4): 69-80.
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Abstract The kinetics of conversion of galena into lead carbonate in(NH_4)_2CO_3 solu-tions was studied using electrochemical method with a rotating ring-disc electrode.Reaction mechanism was proposed based on the results of transient polarizationstudies.A mathematical model was derived to simulate the steady state polariza-tion curves obtained.The oxidation of sulphide to sulphate should be proceeded in a number ofsteps with the formation of intermediate products,A rotating ring-disc electrodewas used to detect the intermediate products with galena as the disc electrode andAg as the ring electrode.Experimental transient polarization curves with a scan-ning rate of 10 mV/s have shown that at 0.49,0.86 and 1.19V(SHE)curfentpeaks were observed on the disc electrode and ring electrode respectively.Basedon the previous work and the experimental results obtained,it has been assumedlthat the first current peak of polarization represents the oxidation of leadsulphide to elementary S with PbCO_3 and S formed on the electrode surface aspassivation film.It is considered that the 2nd current peak of polarization curves representsthe conversion of S to PbSO_4 with lead carbonate and sulphate as the possiblepassivation film.The 3rd current peak has not been studied thoroughly in thepresent work.On steady polarization curves only one current peak(at 0.28V)was found.A kinetic equation for the anodic reaction based upon the mathema-tical model proposed has been derived as follow:(?)The reaction is 2nd order with respect to the NH_4~+ concentration and 1storder with respect to OH~- concentration respectively.When the electric potentialsapplied are rather low,the last two terms of the denominator may be neglected.Calculation based on this simplified equation has been found to represent theexprimental results satisfactorily.
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Received: 18 April 1985
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1 陆克源,铅锌冶炼的进展,中国金属学会重有色金属冶金学术委员会会议论文集,第五集,1982年,p.114．
2 #12
3 Albery,W.J.;Bruckenstein,S.,Trans.Faraday Sac.,62(1966) ,1920．
4 Pleskov,Yu.V.;Fillinovskii,V.Yu.,The Rotating Disc Electrode,Consultants Bureau,New York,1976．
5 曹家祯,薛涛,化工冶金,(1982) ,№4,9．
6 Bratt,G.C.;Pickering,R.W.,Metall.Trans.,1(1970) ,2141． |
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