Thermodynamic Study on Production of High Purity Copper

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In order to estimate the distribution ratios of Se between sodium carbonate-based slag and molten copper, the following measurements have been conducted on the thermodynmic properties of the slags containing Se-oxide at 1423 K to1523 K.(1) Electrochemical measurements of activity of NaO_<0.5> in NaO_<0.5>-CO_2-SeO_2 slag under various partial pressues of CO_2 over the composition range of 1 > N (〕SY.gtoreq.〔) 0.667 {N = n_<Na>/(n_<Na>+n_<Se>), n : the number of moles} by using beta"-alumina as a solid electrolyte.(2) Distribution equilibrium measurements of Se between the slag and molten copper, and(3) Solubility measurements of CO_2 in the slags.Finally based on the results, the equilibrium distribution ratio of Se between the slags and molten copper have been estimated as a function of partial pressures of CO_2 and oxygen and the slag composition at the temperatures of 1423 K and 1523 K.Higher distribution ratios are achieved under conditions of higher partial pressure of oxygen and lower partial pressure of CO_2.Experiments were also conducted for the slag of N * 1 in order to evaluate the effect of partial pressure of oxygen on the distribution ratios. The distribution ratio of Se has two different dependences on the oxygen partial pressure. Under the relatively low oxygen partial pressure, the distribution ratio of both elements decreases with increasing oxygen partial pressure while under the relatively high oxygen partial pressure the distribution ratio of Se increases with increasing the oxygen partial pressure. In both areas, higher distribution ratios are achieved under the condition of lower partial pressure of CO_2.