Solubilities of CO2and redox ratios of Sb and As (nSb3+/nSb5+, nAs3+/nAs5+, n: the number of moles) in NaO0.5–SbOmand NaO0.5AsOm melts were studied. The equilibrium measurements were conducted over the composition range of [formula omitted] under the partial pressures of CO2and O2of 0.01∼0.1 MPa and 0.005∼1000 Pa, respectively, at the temperatures of 1423 and 1523 K. Antimony exists in NaO0.5CO2SbOm melts not only in pentavalent (SbO43-) but also in trivalent (SbO2-) state, their relative proportions depending on the experimental conditions. The CO2solubility in the melts is, therefore, determined by the following reactions: [formula omitted] and [formula omitted]. Arsenic exists predominantly in the form of pentavalent anion (AsO43-) in NaO0.5-CO2AsOm melts. As the pentavalent arsenic is more stable compared with antimony, the redox reaction of arsenic has almost no effect on the CO2 solubility in the melts. Thus CO2 solubility is determined only by the following two reactions: 3CO32-+2AsO2.5=2AsO43-+3CO2 and CO32-=CO2+O2-. However, with increasing content of arsenic oxide in the melts, the evaporation reaction of trivalent arsenic oxide (As4O6), [formula omitted], becomes significant.
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