Electrowinning Copper Using Polyaniline / Cobalt Tetroxide Composite Anode

At present, the Pb-Ca-Sn anodes are widely used in industrial copper electrowinning, which can basically meet the needs of industrical production, because of its relatively inexpensive and forming PbO2 protective layer during the electrowinning process. However, from the energy consumption and environmental considerations, the Pb alloy anodes have a high oxygen over potential(600mV) in electrolysis process, that consume 30 percent of cell energy, and the Pb alloy anodic dissolution affects the quality of cathode copper, in order to solve these problems, people are committed to the development of better performance anode materials.PANI composites have very prospect of application with high conductivity, catal-ytic activity and environment-friendly. PANI base energy saving anodes were used as replaced anode in this article, the PANI/Co3O4 composites with high conductivity and catalytic activity were prepared by in situ polymerization, the effect of synthesis conditions on the conductivity of composite was researched, the structure and surface morphology of the composite were characterized by means of FT-IR, XRD,TGA-DTG, and SEM. The required anodes were preparation by molded forming technology. The electrochemical performance of PANI/Co3O4 composite anodes in copper sulfate electrolysis liquid system and hydrochloride solution were systemic researched, and the constant current polarization, cell voltage, anodes life and power consumption were also researched during copper electrowinning process, the failure of PANI based anodes was analysised at last. Based on that, and pure PANI and Pb-Ag (1%) anodes were used for comparison, research results following:(1) The optimum technological conditions for preparation of PANI/Co3O4 composites were determined:CAn=0.5mol-L"1, Coxidant=0.5mol·L-1, Cacid=1mol-L-1, the ratio of SSA and H2SO4 is 2.5:10. The joined Co3O4 can enhance the charge delocalization of PANI chain and improve the compactness of system, thereby improving the conductivity of composite materials, when mCo304:An=5%, the conductivity of up to 4.56S/cm.(2) Chemical bonds interaction is existed between two particles in composites, the composites are more thermally stable, and the stability of both PANI and PANI/Co3O4 composites can be able to remain below 200℃. The particle size distribution of PANI/Co3O4 composites is more uniform, Co3O4 is basically packaged by PANI through a organized core-shell structure.(3) PANI based anodes have good corrosion resistance in sulfuric acid system than in hydrochloric acid, in the same system, the corrosion resistance of anodes is following as:PANI<PANI/Co3O4(3%)<PANI/Co3O4(10%)<PANI/Co3O4(5%), the corrosion resistance of PANI with defined amount of Co3O4 could be improved, PANI/Co3O4(5%) anode has better properties of charge-transfer and mass transfer diffusion.(4) The apparent activation energy of PANI/Co3O4 anode is only 15.71kJ·mol-1 showing the best of catalytic activity, and PANI/Co3O4 anode can significantly reduce anode polarization potential, so that composite anodes achieve better energy saving effect and electrochemical stability.(5) Under the conditions of current density of 200A/m2, the anodic potential of PANI based anodes is significantly smaller than the Pb-Ag (1%), cell voltage reducing 0.26～0.36V, that can save energy 13.92～19.27%, of which PANI/Co3O4(5%) anodes show the most obvious effect energy saving that the unit energy consumption electrolytic copper was 1364.21 kwh/t-Cu.(6) The structure of PANI is still eigenstate after electrolysis, so catalytic activity was not completely lost, that prove the failure of PANI based anodes related primarily to cracking of the anodes.