Studies on Electrolytic Refining of Zinc. VI : Application of Xanthate or Tetramethyl Thiuramdisulfide to Purification Process of Leached Zinc Solution
At one of the steps in the purification process of leached zinc sulfate solution, the mixed method of nitroso-β-naphthol and K-isoamyl xanthate (K. A. X.) or tetramethyl thiuramdisulfide (T. M. T.) was applied to the zinc solution whose constituents were as follows : Zn=160g/1, Mn=2g/1, Co=20mg/1, Fe=20mg/1, Pb=9.95 or 1.62mg/1. This procedure indicates that not only lead but also cobalt and iron could effectively be removed even when equivalent weight of β-naphthol and sodium nitrite were added to (Co^<+++>+Fe^<+++>). The purified solution after this treatment shows that the concentrations of undesirable impurities were : Co=1 mg/1, Fe=4-5 mg/1, Pb=0.2mg/1. The residual reagents in zinc solution must be removed by copper sulfate, by following the excess copper treated with the zinc-dust, because these reagents cause troubles in the electrodeposition of zinc. If the procedure of Cu-As method is adopted in eliminating cobalt, it will be of advantage in dealing with residual reagents. In the first treatment, lead is precipitated by K. A. X. or T. M. T., in the second, the residual reagent is treated by using copper sulfate, and in the third, the excess copper in filterd solution is applicable to the Cu-As purification. In this procedure, however, simultaneous precipitation of lead and cobalt is not favorable. The use of T. M. T. is favorable to the solution containing lead in relatively high concentration, but K. A. X. can be used successfully at low concentration such as 1 mg/1 or so. It is possible to precipitate lead almost completely from solution by means of xanthate, provided that the reagent is added as much as ten times the equivalent quantity. However, xanthate is unfavorable for the following reasons : Reagent and precipitated lead salt are very unstable, and precipitation of lead rather sensitive to the reaction conditions and other impurities such as manganese or iron ; furthermore, the electrodeposition of zinc is susceptible to tremendously harmful effect of residual xan-thate, even though extremely small in quantity. T. M. T. is superior to K. A. X. in these points especially in that the deposit of zinc is very smooth and has metallic luster even when it is added as much as 70 mg/1 to the electrolyte solution.
- Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy 11 230-243, 1959