Zinc Electrowinning The Anode Material Preparation And Properties Of Polyaniline / Boron Carbide

At present, the lead-based alloy is always used as insoluble anode in zinc electrowinning industry. However, there were several problems on the lesd-based anode, for example:(1)high oxygen evolution overpotential of anodes (about 860mV) which can increase the energy consumption 1000Kwh/t-Zn. (2) low corrosion resistance and decase of the product quality because of lead dissolved in the electrolyte, (3) low mechanical strength and anti-crawling ability, easy curving and short circuit. A In order to deal with the shortcoming of lead-based anode, many new different anodes had been researched around the word, but due to the short life and high cost problems, they still can not replace the lead-based anode. Therefore, it still is an impotant subject to research new energy saving anode in the metal electrowinnng industry.The PANI/B4C anodes has the specificity polymer structure. They can reduce the anodic overpotential, increase corrosion resistance and prolong the using life of anode, lowder energy consumption and improve the quality of product Zn on cathode. In this paper, the PANI/B4C composites materials were prepared by in-situ polymerization method, the compositing mechanisms were studied and the optimal preparation condutions were got. At the same time,compared with the performances of Pb-Ag(l%wt) alloy anode such as the oxygen evolution overpotential, cell voltage, current efficiency, energy cunsumption, electrode life and zinc quality and so on,.the electrochemical properties of PANI/B4C anode in zinc sulphate of electrolyte systems were discussed systematicly.PANI/B4C composites were characterized by means of FTIR, XRD, SEM, EDS and thermal analysis and so on. The electro-properties of anode have been researched by linear sweep voltammetry, tafel plot, cyclic voltammetry, A.C impedance and oxygen potential. The main results are showed as following:(1) The optimal preparation conditions of PANI/B4C composites are :VH2o=0.2, CAn=0.5mol/L,mB4C:mAn=0.2, Cacid=lmol/L(H2SO4:SSA=4:1), Coxidant=0.5mol/L. The conductivity of PANI/B4C composites are 35.63S/cm. The conductivity and thermal stability of the composites are higher than that of PANI.(2) There are chemical bonds interaction between the B4C particles and PANI molecular chains. The C atom of the B4C doped into polyaniline molecular chains which reduced the density of electron clouds of PANI skeletal and strengthened the charge moving and concluded that the composites conductivity improved.(3) In zinc sulphate of electrolytic system, the corrision resistance and the electro-chemical stability of PANI/B4C were better than that of PANI. The linear sweep voltammetry, A.C impedance and catalytic activity show that the PANI/B4C anode was best.(4) At 500A/m2 current density, oxygen potential of the Pb-Ag(1%wt) alloy anode is 1.864V, PANI anode is 1.575V and PANI/B4C anode is 1.52V. The cell voltage and energy comsumption are less than Pb-Ag(1%wt) alloy anode. At the same time, the life of Pb-Ag(1%wt) alloy anode is 2.37years, PANI is 1.32years and PANI/B4C is 1.6years.(5) The main reasons of deactivation for the PANI/B4C anode was that PANI covered on the surface of the B4C peeled off, which lead the decline of the conductivity of the anode. In addition, the crack were emerged on the surface of the anode made the cutting-out the entire electrode conduct system,and finally lost conductivity.