Toshiharu Mitsuo

Dilute sulphuric-acid leaching of garnierite ore after magnetic-roasting the ore mixed with iron powder

Abstract In order to investigate sulphuric-acid leaching of garnierite ore rich in magnesia, an attempt was made to selectively extract nickel using the dilute sulphuric acid leaching method after magnetic-roasting the ore mixed with iron powder. In addition, a study was made of the effects of various factors in this process on the extraction percentages of various components. The selective extraction of nickel by dilute sulphuric acid leaching has been made possible by mixing about 5% iron powder with the garnierite and subsequently carrying out magnetic roasting at 1000°C in a water vapor atmosphere for more than 30 min. In order to raise the nickel extraction percentage while keeping low those of magnesia and iron it is advisable to lower the concentration of sulphuric acid (about 1/50), and raise the extraction temperature (about 95°C). When the leaching temperature is comparatively low (about 50°C), a weak agitation exercises more effective influence on the selective extraction of nickel. Under optimum conditions, the extraction percentages of nickel, magnesia and iron are more than 98%, less than 5%, and less than 3%, respectively.