Floating Slimes Essay

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Silver, lead, arsenic, bismuth, antimony, selenium, and nickel are common impurities existing in copper anodes. Some impurities dissolved from the anodes can precipitate, if their concentrations in the electrolytic solution are above saturation levels. Some of these precipitates can settle down but some are floating slimes and can be a source of cathode contamination by their incorporation into the cathode 16.
These floating slimes are amorphous and typically have compositions of Sb-As-O and Bi-As-O, precipitated in the electrolyte, rather than on the surface of anodes 17. Like the small anode slime particles that are liberated from the anode slimes layer, these floating slimes are generally small and, therefore, are suspended in the solution. They can be transported to the cathode by the fluid flow in an electrorefining cell and get entrapped on the cathode. Some studies on its formation and deposition mechanism and associated prevention have been carried out. Antimony is widely considered as a major source of floating slimes. F. Noguchi, H. Itoh and T. Nakamura studied the dissolution mechanism of antimony from the anode and its effect on floating slimes. They intentionally added antimony
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Some of the impurities dissolved from the copper anode including As, Sb and Bi can co-precipitate to the anode slimes from the copper electrolyte in electrorefining as reported 36. The homogeneous co-precipitation of arsenic, antimony and bismuth in the copper electrolytic solution is the basic principal behind the technology of self-purification to reduce the impurity level in the electrolyte. More specifically, bismuth and antimony can precipitate onto the anode slimes with arsenic spontaneously if the concentration of arsenic in electrolyte is at an appropriate level 36. The rate of homogeneous precipitation of impurities in the electrolyte varies depending on process conditions

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