Polyaniline anode for zinc electrowinning from sulfate electrolytes

Polyaniline (Pani) anode is tested to highlight the feasibility of reduction of both energy consumption and capital costs in zinc electrowinning from sulfate solution without any modification to the existing plant. Current density, electrolyte temperature, added gelatin, added Mn2+, oxygen-evolution potential, cell potential and long duration tests were investigated. The zinc deposits were also studied by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that current density and added gelatin change the preferred crystal orientations of the zinc deposits. Compared with Pb-Ag(1%) anode used in industry, the cell voltage decreases by 0.15-0.30 V, energy consumption of Zn is 2.46-2.70 kW.h/kg which results in 20% energy savings. Long duration tests show that Pani anode can represent a good alterative ability for zinc electrowinning. Zinc deposits obtained have no Pb pollution. The additions of Mn2+ ions and gelatin also change the surface morphology and deposit quality of the electrodeposited zinc, affecting the crystal orientation. These researches demonstrate that Pani anode has distinct advantages over acidic electrowinning process.