Solubility of silver in MO (M₂O)-B₂O₃ (M = Ca, Ba and Na) slags

The solubility of silver in MO-B₂O₃ (MO = CaO, BaO and Na₂O) slags at high temperatures was measured in order to understand the dissolution mechanism of silver in the slags, and the effects of CaO, BaO, and Na₂O on the solubility of silver. The solubility of silver in the Na₂O_satd-B₂O₃ system exhibits a minimum value as a function of oxygen partial pressure at about p_O(2) = 8.49×10^-9 Pa. Therefore, the dissolution reaction of silver in basic slags at higher oxygen potential can be estimated by the following equation: Ag(l)+1/2O₂(g)+O^2-(slag) = AgO₂^2-(slag) (p_O(2)≥8.49×10^-9 Pa). The solubility of silver in B₂O₃-bearing slags also exhibits a minimum value as a function of slag composition. The minimum composition shifts to the acidic region following the order of CaO-, BaO-, and Na₂O-B₂O₃ slag. Based on these minimum compositions, i.e., 65 (mol%) CaO, 45 (mol%) BaO, and 35 (mol%) Na₂O, the value of the CaO-equivalence of BaO and that of Na₂O are suggested as 1.44 (= mol% CaO/mol% BaO) and 1.86 (= mol% CaO/mol% Na₂O), respectively.