Removal of arsenic from liquid copper by use of sodium carbonate
Abstract
Two new trends, an increasing arsenic content in raw material and the development of the continuous processes, make the removal of arsenic from copper more important and more difficult. Because of the very low activity coefficient of arsenic in copper, the conventional slags used in the copper-making process cannot remove arsenic effectively. New methods and fluxes for removal of arsenic from liquid copper are required. The thermodynamic aspects of removing arsenic by use of sodium carbonate have been studied and the distribution coefficient of arsenic between sodium carbonate and liquid copper has been measured. It is more than one order larger than that of ferrite, silicate and calcium slags. The products of the de-arsenization reaction by use of sodium carbonate are mainly sodium arsenate, which contains five valent arsenic, and lower valent arsenic oxide. The ratio of high valent arsenic to low valent arsenic in the reaction products is controlled by the reaction temperature and the oxygen partial pressure. Assuming regular solution behavior for copper-arsenic alloys, the activity coefficient of arsenic in the slag has been derived. This is also a function of temperature and oxygen partial pressure. Using the arsenic capacity as a parameter to measure the ability of removing arsenic, several slags are compared and a qualitative relation between optical basicity and arsenic capacity is confirmed. To further correlate the arsenic capacity to the slag composition, more details of the reaction mechanism and the interaction between reagents and products should be studied.
Degree
Ph.D.
Advisors
Gaskell, Purdue University.
Subject Area
Metallurgy
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