ニッケルけい酸塩に及ぼすマグネシアの影響

ラテライトの処理に関する研究 (第3報)

抄録

In order to obtain the fundamental data for the extraction of nickel from silicate ores, the synthesis of nickel olivine and the reduction of the olivine with hydrogen were studied. A comparison between the results for synthesized materials and those for ores was also revealed.
The results obtained are as follows:
1) The nickel-olivine shows the orthorhombic lattice which has the general formula (Mg_m/2Ni_n/2) ₂SiO₄, where m plus n equals two, and m and n are the integers from zero to two. Ni₂SiO₄ and Mg₂SiO₄ form a complete solid solution at any composition.
2) It is found that the reducibility of Ni₂SiO₄ decreases as the content of Mg₂SiO₄ in the mineral increases.
3) When garnierite is heated in the air, anhydrous nickel silicate, 3 (Mg, Ni) O·2Si0₂, is formed due to the release of the water of crystallization between 460°C and 700°C.
This silicate tends to crystallize at higher temperatures than 800°C, forming forsterite and Si0₂. Nickel oxide in the mineral forms then nickel orthosilicate, and a complete solid solution with forsterite as the synthesized olivine does.
4) The anhydrous nickel silicate is amorphous and reducible. In order to avoid the formation of unreducible compounds of nickel, (Mg_m/2Ni_n/2) ₂SiO₄, a regulated slow cooling of the ores from 460°C up to 800°C under hydrogen reducing atmosphere is preferable.