Yoshitaka Nakahiro

Consideration for Some Problems and Improved Measures of Separation of Cu-Zn Ores

It is well known that the separation of copper and zinc minerals in the complex sulphide ores flotation is very difficult. On the other hand, it is also important to recover sphalerite entrained in the copper concentrate which is produced from the concentrators treating Cu-Pyrite ores and to recover chalcopyrite entrained in the zinc concentrate which is produced from the concentrators treating the Pb-Zn ores. Thus, the separation technique of Cu-Zn ores includes many difficult problems which have to improve.In this paper, the authors considered on many problems for the separation of Cu-Zn ores and discussed on how to separate the above minerals from the research works of the previous papers of the authors and others. There are many reasons why the separation of Cu-Zn ores is very difficult. One of them is the copper ions existing in the flotation pulp. Accordingly, the prevention and deactivation of the copper-activated sphalerite were discussed in order to separate the Cu-Zn ores.Among the previous research works which were carried out by the authors, the prevention and deactivation of copper activation for sphalerite were most effective by the use of sodium sulphide and ferric ion solution containing sulphuric acid. The effect of sodium sulphide on the prevention of copper activation for sphalerite was studied in the presence of sulphurous acid or sodium cyanide used as a depressant of sphalerite. From the results obtained, it may be considered that the copper activation of sphalerite is prevented perfectly by the use of sodium sulphide. Then the deactivation of the copper-activated sphalerite was investigated in a series of the laboratory experiments by the use of ferric ion solution containing sulphuric acid. From the results obtained, it was recognized that the deactivation of copper-activated sphalerite could be attained remarkably by the treatment of 980 mg/l Fe+++ solution containing over 4 vol. % of H2SO4. O2 gas accelerates the deactivation of the copper-activated sphalerite by the treatment of the above both solution. The temperature is one of the important factors for the deactivation. Using the flotation machine, the differential flotation test of Cu-Zn ore were carried out. The separation of Cu-Zn ore was successful by the deactivation treatment for Cu-Zn ore.From the recent paper by R. M. Manser and P. R. A. Andrews, a new reagent, Kr6D, as a depressant for sphalerite in a differential sulphide flotation stage was introduced in this paper. Small-scale laboratory flotation tests on such pure sulphide minerals as sphalerite and chacopyrite indicated that the Kr6D is capable of depressing sphalerite when used in small doses. At higher concentrations, chalcopyrite is also depressed. Single-stage batch-scale flotation tests were carried out on bulk concentrates containing the sulphide minerals. The Kr6D was compared with starch as a depressant both in the presence and in the absence of sulphur dioxide. In each case the new modifier was shown to be more effective.In addition to the above methods for the separation of Cu-Zn ores, the authors considered the possibility of improving selective flotation of bulk flotation concentrates from the previous papers of some other authors, including the abrasive action of high temperature and electric current for the adsorption collector layer on sphalerite and chalcopyrite. The desorption of collector layer on the Cu-Zn bulk concentrate by the use of sodium sulphide was discussed.

On the Separation of Pyrrhotite and Sphalerite

The depression of pyrrhotite containing sphalerite is very difficult on account of the copper ion activation during the zinc flotation process. Accordingly, the mineral particles to be floated by the copper ion activation are so many that the flotation machine overloads. Thus, the grade and recovery of zinc in the zinc concentrates are remarkably lowered. Therefore, it has been said that the zinc flotation is disturbed considerably in the case where pyrrhotite exists in Sphalerite.In this paper, the authors pursued on many problems for the separation of sphalerite and pyrrhotite and discussed on how to separate the above minerals from the detailed investigation of the past paper.At first, the authors attempted to discuss on the copper ion adsorption of sphalerite and pyrrhotite. As compared the copper ion adsorption on sphalerite with the copper ion adsorption on pyrrhotite, it is recognized that the copper ion adsorption on sphalerite proceeds in all pH values, but the copper ion adsorption on pyrrhotite depends remarkably on the pH value. With the increase of the iron contents in sphalerite, the copper ion adsorption on sphalerite decreases in the case where oxygen is sufficiently dissolved in the flotation pulp and the pH is high enough. On the other hand, the copper ion adsorption on pyrrhotite scarecely proceeds in the above-stated conditions. Bushell and his collaborators carried out the flotation tests for the separation of sphalerite and pyrrhotite by using oxygen. They confirmed that the separation of sphalerite and pyrrhotite is possible. As a reason, they surmised that the copper ion adsorption is hindered because of the formation of the insoluble and protective film such as ferric hydroxide, ferric oxide, or basic iron salt in the case where the pH is high enough and oxygen is sufficiently dissolved in the flotation pulp to oxidize iron of mineral surface.As the above mentioned, it is considered that the dissolved oxygen in the flotation pulp is one of the most important factors.