Effects of Coexisting Oxygen and Antimony in Molten Copper on Rate of Arsenic Elimination from the Copper Phase by the Use of Na<SUB>2</SUB>CO<SUB>3</SUB> Slag

Abstract

The rate of As elimination from molten copper by the use of Na 2 CO 3 slag was measured at 1523 K. The results obtained, under the experimental conditions of this study, show that As in molten copper is eliminated in a pentavalent form and that its elimination rate increases with increasing initial oxygen concentration in molten copper. Based on the results obtained in the present study, the overall rate of As elimination is probably controlled by mass transfer in molten copper. The mass-transfer coefficient of As in molten copper at 1523 K was determined to be 1:3ðAE0:4Þ Â 10 À4 mÁs À1 based on the material balances of As and oxygen in the molten copper and slag phases, and the equilibrium relationship of the As elimination reaction at the slag-metal interface. In addition, the behavior of the simultaneous elimination of As and Sb, which coexist as impurities in molten copper at 1523 K, were also investigated from a kinetic viewpoint. The results show that the elimination rate of As is much higher than that of Sb, and two types of elimination behaviors are observed depending on the initial oxygen concentration in molten copper. At relatively low initial oxygen concentrations, As is preferentially eliminated with an initial plateauing of Sb elimination. On the other hand, both elements are eliminated simultaneously at relatively high initial oxygen concentrations. These behaviors were examined from the viewpoint of the oxygen concentration at the slag-metal interface.

A new interpretative approach to the chemistry of copper-alloy objects: source, recycling and technology

“…Bray & A.M. Pollard in certain of its metals depending on how many times it has been reheated, and to what temperature (e.g. Hampton et al 1965;Charles 1980;Pickles 1998;Beeley 2001: 497;Tanahashi et al 2005;Lee et al 2009).…”

Beyond Provenance

“…The importance of such factors is shown by the fact that they are exploited by the modern copper industry in order to oxygen refine the raw copper produced by the smelter (Copper Development Association 2011), and also that such selective oxidations are now an important part of the metal recycling industry, e.g., recovering copper from mobile phones (Kaspar et al 2011). Consequently, there is an extensive literature on oxidation effects in molten metals that is useful for considering in the archaeological context: a copper alloy object will be depleted in certain of its metals depending on how many times it has been reheated, and to what temperature (e.g., Hampton et al 1965;Charles 1980;Pickles 1998;Beeley 2001: 497;Tanahashi et al 2005;Lee et al 2009). Unfortunately, however, the modern metal recycling industry is not interested in the same combinations of trace elements as we find in Bronze Age alloys, so a certain amount of experimental work has been necessary to understand these systems (Sabatini 2017).…”