Simultaneous Partitioning of Divalent Metal Ions between Alabandite and 1 mol/L (Ni, Mg, Co, Zn, Fe)Cl₂ Aqueous Solutions under Supercritical Conditions

To clarify the element partitioning behavior between minerals and aqueous chloride solutions, we conducted experiments to investigate simultaneous partitioning of Ni²⁺, Mg²⁺, Co²⁺, Zn²⁺, Fe²⁺, and Mn²⁺ ions between alabandite (MnS) and 1 mol/L (Ni, Mg, Co, Zn, Fe)Cl₂ aqueous solutions at 500–800 °C and 100 MPa. The bulk partition coefficients calculated using the following equation were in the order of Fe²⁺ > Co²⁺ > Ni²⁺ ≈ Zn²⁺ > Mn²⁺ >> Mg²⁺; K_PN = (x_MeS/m_Meaq)/(x_MnS/m_Mnaq). A partition coefficient-ionic radius (PC-IR) curve was plotted with the logarithmic value of the partition coefficient on the y-axis and the ionic radius at the six-fold coordinated site on the x-axis. The peak of this curve was located near the ionic radius of Fe²⁺ and not near the ionic radius of Mn²⁺. Zn²⁺ showed a slight negative partitioning anomaly, which increased in the order of sulfide minerals < arsenic sulfide minerals < arsenide minerals as the covalent bond became stronger. Ni²⁺ showed a positive partitioning anomaly, which indicated that it preferred an octahedral structure. The width of the PC-IR curve decreased in the order of sulfide minerals > arsenic sulfide minerals > arsenide minerals as the covalent bond became stronger, that is, the ion selectivity became stronger. View Full-Text