Yoshinori Shirane

Activity measurements in the oxide solid solutions of NiOMgO and NiOMgOSiO2 systems in the temperature range between 1073 and 1273 K

Abstract Many activity measurements of components in liquid oxides habe been reported in the field of slag chemistry. However, very little is known about the thermodynamic behavior of components in oxide solid solution. In the present paper, e.m.f.s of the following galvanic cells employing solid electrolyte ZrO2 (CaO) were measured on the entire range of composition of the solid solutions. Pt/Ni −( Mg 1−x Ni x ) O/ZrO 2 ( CaO )/ Ni − NiO/Pt Pt/Ni −( Mg 1−x Ni x ) 2 SiO 4 / ZrO 2 ( CaO )/ Ni − NiO/Pt Pt/Ni −( Mg 1−x Ni x ) SiO 3 / ZrO 2 ( CaO )/ Ni − NiO/Pt Activities of NiO in these solid solutions of (Mg1 − xNix)O and (Mg1 − xNix)2SiO4 (where 0≦x≦1) calculated from the results of e.m.f. measurements show considerable negative deviation from Raoults law, whereas (Mg1 − xNix)SiO3 (where 0≦x≦0.12) is slightly positive in the temperature interval studied in the present investigation, 1073–1273 K. In many nickel extraction processes such as segregation, preliminary reducing, chloridizing-roasting, etc., we may be confronted with very complicated systems of the mineralogical types of garnierite ores involving a number of possible reactions. The present thermodynamic approach to the ternary system enables us to predict the feasibility of a proposed process, and thus may contribute to a considerable saving in its cost.

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.