The objective of this research project is to remove the impurities (selenium, tellurium, etc) contained in the anodic slimes from copper refining through a combination of pyrometallurgical and hydrometallurgical processes, based on prior treatment of the muds at high temperatures.
Research has been undertaken to establish the flowsheet of a selective leaching process for the elimination of the main impurities contained in the anodic slimes of copper refining in order to obtain a precious metals concentrate free of arsenic, antimony, selenium and tellurium, which may then be treated as common precious metals raw material. By pyrohydrometallurgical treatment, it was possible to selectively eliminate the most important impurities from the anodic slimes and a flowsheet was proposed to present the possibility of eliminating 1, 2, or all impurities according to requests of the market. Thus, if the penalizing impurity is only arsenic, for example, a roasting process is not necessary. In the same way, if the arsenic content of the slimes is correct, the first leaching with potassium hydroxide can be avoided. Consequently, this process can make the anodic slimes fit all the requirements of the market. When the process was completed and most of the impurities eliminated, the results was a precious metals concentrate easy to treat by conventional methods. Therefore, the pyrohydrometallurgical process yielded various marketable solutions containing all the impurities and a precious metals concentrate. By autoclave leaching nearly all the copper and more than 90% of arsenic were dissolved, and selenium, tellurium and antimony only partially dissolved. From the solutions thus obtained most of the elements could be recovered by selective precipitation and the use of resins. With fluosilicic acid and water acetonitrile solutions, copper, arsenic and antimony were selectively leached, leaving a residue enriched in selenium and precious metals. By solvent extraction, enriched copper sulphate solutions were obtained from copper solutions produced in the different processes of treatment of anodic slimes.
This project will establish an alternative route to the known methods for the recovery of nonprecious metals from the anode muds resulting from the electrolytic refining of copper. This new route will be based on 3 main points of interest: obtaining a process with minimum environmental impact, as far as possible separating the components present in order to use them; creating a better yield of the metals present in the muds, especially selenium and tellurium; and establishing a process whose economic interest makes it attractive and worth using.
In the first place, the possibilities of pyrometallurgical and hydrometallurgical treatments will be examined with a view to obtaining complete separations and recyclable liquids. The recovery of selenium, tellurium, arsenic, antimony, bismuth and lead will make it possible to obtain a material which can be melted to give a bullion of precious metals which can be treated by the usual processes. At the same time 3 methods of direct leaching in the autoclave will be studied, with hexafluorosilicic acid and in hydroorganic media and isoacidic solutions.
Funding SchemeCSC - Cost-sharing contracts