鉄の抽出を目的としたファヤライトおよびその水素還元生成物の塩酸処理

抄録

It was previously reported that the hydrogen-reduction product of Fayalite was the iron crystals surrounded with the silica crystals, having no Si-O-Fe-O-Si bond. The extraction of Fe from Fayalite with HCl is much easier than from the hydrogen-reduction product. 100% of Fe was extracted from Fayalite with boiling 6 N HCl, while only 85% of Fe was extracted with boiling 6 N HCl from hydrogen-reduction product.
Both residues were examined with the X-ray diffraction method: The residues of the hydrogen-reduction products show the decrease of α-Fe alone with the advance of the extraction process, leaving a small amount of α-Fe and amorph silica as residues at the later stage of extraction. The residues of Fayalite show the decrease of orthorhombic Fayalite in the early stage.
In later stage of extraction, the X-ray diffraction patterns of a cubic Fayalite spinel-like substance appeared. When extracted all of Fe in Fayalite, no diffraction patterns were detected. About residues of HCl extraction with two series of samples, the infra-red absorptions were measured. Residues of the H₂-reduced product showed only the infra-red absorption of SiO₂ in the early stage, and in later stage the absorption due to the hydration of SiO₂ appeared together with the absorption of SiO₂.
In the case of the residues of Fayalite, with the advance of the HCl extraction process, the absorption of orthorhombic Fayalite disappeared, but that of SiO₂ with OH-bond appeared.
No absorption of the cubic Fayalite spinel was detected. The process of the Fe²⁺ extraction in the orthorhombic Fayalite with HCl has been discussed to account for the formation of fine colloidal silica.