아연 생산 공정에서 발생한 코발트-니켈 케이크 중 유가금속의 회수를 위한 황산침출 및 분리정제에 관한 연구

Abstract

The production of zinc has been generally achieved by hydrometallurgy process. In the process, zinc sulfides(ZnS) are roasted into zinc oxides(ZnO), and then zinc oxide ores are leached with sulfuric acid. Impurities in leach solution are removed during purification step, finally, zinc metal can be electrowon. Purification step is divided into precipitation removed ferric and ferrous ions converting hydroxide compounds and cementation removed noble metal such as cadmium, copper, cobalt, nickel using zinc powder. the cobalt-nickel cake used in this experiments is generated during purification step removed cobalt and nickel by adding excess of zinc powder much higher than the stoichiometric amount needed with copper and antimony as activators. Thus the cobalt-nickel cake contains not only non-reacted zinc and removed cobalt and nickel during cementation but also copper and antimony added as activators. Therefore, it is needed to treat pyrometallurgically and hydrometallurgically. But it is difficult to recover only zinc pyrometallurgically because zinc volatilizes with cadmium when cobalt-nickle cake is roasted at high temperature. Hydrometallurgical difficulty is that zinc is leached with impurities. It is required to remove impurities again in another purification stage. The present study is aimed at investigating the leaching behavior of cadmium, copper, zinc, cobalt, nickle, lead, antimony from cobalt-nickel cake in sulfuric acid and removal of cobalt and nickel from synthetic electrolyte included cobalt, nickel, copper and antimony for recovery of valuable metals.

Cobalt-nickel cake sample was disintegrated and wet-sieved with 150㎛ sieve. Less than 150㎛ size only used in leaching experiments. The effect of reaction time(0-180min), temperature(30-90℃), concentration of sulfuric acid(0.1-1.0M), agitation speed(200-800rpm), pulp density(10-50g/L) was investigated. Cementation experiments used 300mL of synthetic electrolyte were conducted at 70℃ by adding 3g of zinc power. The effects of concentration of copper and antimony(30-480ppm) were also investigated.

The result of leaching experiments were more than 99% of cadmium and zinc were leached in 5min and same ratio of cobalt was leached in 30min, more than 99% of copper, 97% of nickel, 95% of antimony and about 2% of lead were leached in 60min at 50℃ with 400rpm and pulp density 10g/L in 1.0M sulfuric acid. It is possible to remain lead as a precipitate and recover cadmium, zinc, copper, cobalt, nickel, antimony in electrolyte. The result of cementation experiments were 90% of copper and antimony and 30% of cobalt and nickel were removed rapidly from synthetic electrolyte included 60ppm of cobalt, nickel, copper and antimony at 70℃ with pH 4 in 5min. After all of copper and antimony were removed in the early stage of cementation, removal efficiencies of cobalt and antimony increased to 70% and 78%, respectively, slower than before. Because dissolved zinc ions in electrolyte prevent cobalt and nickel ions from contacting with zinc powder surface. The removal efficiency of cobalt has no significant effect on concentration of copper but increased with concentration of antimony and removal efficiency of nickel increased with concentration of copper and antimony.