Solubility of Silver in MO (M<SUB>2</SUB>O)–B<SUB>2</SUB>O<SUB>3</SUB> (M = Ca, Ba and Na) Slags

Abstract

The solubility of silver in MO-B 2 O 3 (MO = CaO, BaO and Na 2 O) 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 Na 2 O on the solubility of silver. The solubility of silver in the Na 2 O satd -B 2 O 3 system exhibits a minimum value as a function of oxygen partial pressure at about p o2 = 8.49 x 10 -9 Pa. Therefore, the dissolution reaction of silver in basic slags at higher oxygen potential can be estimated by the following equation: Ag(1) + 1/2O 2 (g) + O 2- (slag) = AgO 2- 2 (slag) (p o2 ≥ 8.49 × 10 -9 Pa). The solubility of silver in B 2 O 3 -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 Na 2 O-B 2 O 3 slag. Based on these minimum compositions, i.e., 65 (mol%) CaO, 45 (mol%) BaO, and 35 (mol%) Na 2 O, the value of the CaO-equivalence of BaO and that of Na 2 O are suggested as 1.44 (=mol% CaO/mol% BaO) and 1.86 (=mol% CaO/mol% Na 2 O), respectively.