Abstract
It has been shown that a film of electroless Cu on the surface of polyvinyl chloride particles (Cu/PVC) imparts significant electrochemical activity onto the PVC surface. Microscopic inspection revealed adequate adhesion between the Cu-film and the PVC substrate. Particles of Cu/PVC were used as an electrode material for the electrowinning of zinc from alkaline zincate solutions over a temperature range from 30 to 55 C. These particles were used in the form of a packed bed electrode through which the alkaline zincate electrolyte was made to flow. Such a system furnished extremely high rates of electrowinning (up to 700 mA cm exp )2 ) which are several-fold greater than those obtainable on planar electrodes. This study compared the Cu/PVC with bulk Cu electrodes in terms of polarization behavior, coulombic efficiency, cell voltage, and power consumption. The Cu /PVC electrode behaved in essentially the same way as the bulk Cu electrode. However, its coulombic efficiency is somewhat lower (74 vs. 88% for bulk Cu at 30 C) and hence its specific power consumption is somewhat higher (5.0 vs. 4.7 kW h/kg Zn for bulk Cu). The Cu/PVC electrode performed quite well in a highly caustic environment (3M KOH, at 30-55 C). In fact, the performance improved upon temperature increase in this range. However, > 55 C, the polarization requirement started to increase. Inspection of the particles of Cu/PCV revealed that this was due to local flaking of the Cu-film from the PVC surface, which was accompanied by loss of interparticle conductivity.