炭酸カルシウムの結晶析出におけるNi²⁺, Co²⁺, Mn²⁺, Fe³⁺イオンの添加効果

抄録

Crystallization of CaCO₃ from Ca (NO₃) ₂ aqueous solution by mixing Na₂CO₃ aqueous solution and homogeneous precipitation methods were investigated in the presence of Ni²⁺, Co²⁺, Mn²⁺ and Fe³⁺ ions on the morphology and color of deposit. The results are follows :
(1) In solution mixing method at 35°C, Ni²⁺ ions accelerated transformation from vaterite to aragonite and Mn²⁺ ions did that to calcite, whereas Fe³⁺ ions stabilized vaterite.
(2) In homogeneous precipitation method at 90°C, all additives stabilized aragonite, and the stabilizing effect decreased in order of Mn²⁺, Co²⁺>Ni²⁺>Fe³⁺ ions. The larger the effect was, the smaller the aragonite particle size was.
(3) Lattice constants, ao, of pure calcite by homogeneous precipitation method at 90°C was smaller than that by solution mixing method at 35°C. The addition of Ni²⁺ and Mn²⁺ ions decreased both ao and co, suggesting their substitution of Ca²⁺ ions in calcite. The lattice constants changed little by addition of Fe³⁺ ions.
(4) On lattice constants of aragonite, the addition of Mn²⁺ ions decreased ao and co, but increased bo in solution mixing method at 90°C. In homogeneous precipitation method at 90°C, lattice constants changed little in the presence of Mn²⁺, Ni²⁺ and Co²⁺ ions.