Thesis (M.Tech.) / The electrochemical refining of copper was investigated at different temperatures,
distances between electrodes, different levels of overvoltage, current density, metal
impurities, smootheners, electrode-active area and concentration of electrolyte using the
parallel-plate model. The purpose of the investigation was to evaluate the effect of
smootheners, impurities and other factors on the recovery of copper from solutions.
The results showed that the metal impurities, with more negative oxidation potentials,
did not affect the electro-deposition of copper whilst metals with oxidation potentials
close and equal to that of copper reduced the current efficiency. The current density
increased with the increase in temperature, overvoltage and concentration of electrolyte.
The increase in overvoltage and current density above limiting values produced
increased rates of deposition resulting in efficiencies greater than 100% to be attained.
The increase in the limiting current density at concentration below 10.8g/L produced
low values of current efficiency ranging from 100 to 30%. The 2 and 3cm distance
between electrodes produced stable efficiencies of between 92-100% and 96-100%
respectively. The temperature was found to have indirect effect on the current
efficiency but direct effect on the dissociation of electrolyte in solution, current density
and overvoltage. An increase of 20cm2 of electrode active area reduced the current
efficiency by about 40%. The increase in concentration of electrolyte produced an
increase in the current density and efficiency ranging from 75-100%. The use of
smootheners; thiourea and EDTA (Ethylenediaminetetraacetic acid) reduced the current
density and current efficiency (100>CE>30%). However increased concentration of Kglue,
B-glue and G-Arabic in conjunction with EDTA or thiourea and NaCl improved
the current efficiency even at increased levels of overvoltage to levels of 96-100%,
100% and 90-100% respectively. Therefore, the presence of impurities, the use of high
current densities, inadequate distance between electrodes, and too low concentration of
electrolyte and the absence of glue disadvantaged the recovery process while the
presence of K-glue and B-glue reduced the inhibition effects of thiourea and EDTA and
thus improved the recovery of copper from solutions.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:umkn-dsp01.int.unisa.ac.za:10500/2762 |
| Date | 12 1900 |
| Creators | Ntengwa, Felix William |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 1 online resource (xv, 191 leaves (some col.) |
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