超臨界条件下における硫砒鉄鉱および輝コバルト鉱と 塩化物水溶液間における2 価金属イオンの同時分配実験

Experiments on the partitioning of cations between arsenopyrite and (Zn²⁺,Co²⁺,Ni²⁺,Mn²⁺, Mg²⁺)Cl₂ aqueous solution were conducted at 500 and 600 °C, 1 kb. The cations tended to concentrate into arsenopyrite in the following order: Co²⁺ ＞ Ni²⁺ ≥ Fe²⁺ ＞ Zn²⁺ ＞ Mg²⁺ ＞ Mn²⁺. The optimum ionic radius for arsenopyrite is situated between Co²⁺ and Fe²⁺ (around 0.77 Å). Experiments on the partitioning of the cations between cobaltite and (Zn²⁺,Ni²⁺,Fe²⁺, Mn²⁺,Mg²⁺)Cl₂ aqueous solution were also conducted at 500-800 °C, 1 kb. The concentration tendency of the cations into cobaltite was as follows: Co²⁺ ＞ Ni²⁺ ＞ Fe²⁺ ≥ Zn²⁺ ≥ Mg²⁺ ＞ Mn²⁺. This order is the nearly same as that of arsenopyrite. However, cobaltite shows larger diŠerence in the partition coeŠicient between Co²⁺ and Fe²⁺ than arsenopyrite. This is because the optimum ionic radius for arsenopyrite is situated somewhat in the Fe²⁺ side than cobaltite (around 0.76 Å). The partition coeŠicient -ionic radius (PC-IR) curves for arsenopyrite and cobaltite are steeper than those for silicate and multiple oxide minerals. This suggests that the selectivity of sulˆde minerals to the cations is stronger than silicate and multiple oxide minerals. Zn²⁺ shows a negative anomaly, re‰ecting that Zn²⁺ prefers a 4-fold coordinated site. Although Ni²⁺ shows a positive anomaly, the degree of anomaly is smaller than that of the multiple oxide minerals having the peak of the PC-IR curves near Fe²⁺. Because the peaks of the PC- IR curves for maˆc silicate minerals are situated in the vicinity of Ni²⁺ and they does not show a remarkable anomaly, it is considered that the magnitude of the anomaly of Ni²⁺ is proportional to the distance between the ionic radius of Ni²⁺ and the position of the optimum ionic radius of the mineral.