Leaching of Germanium from the Slag of the GECAMINES Factories in Lubumbashi by Oxalic and Sulfuric Acids

Kazadi Oscar Kayembe; Bolande Chantal Mobangolo; Kitambala Marsi Mbayo; Kitule Simon Muhune; Mutombo Emery Kalonda; Kabumana Dieudonné Tshibanda; Simbi Jean-Baptiste Lumbu

Kazadi Oscar Kayembe
Bolande Chantal Mobangolo
Kitambala Marsi Mbayo
Kitule Simon Muhune
Mutombo Emery Kalonda
Kabumana Dieudonné Tshibanda
Simbi Jean-Baptiste Lumbu

Keywords: elimination, leaching, silica, germanium, metal refining, Lubumbashi slag

Abstract

The objective of this study is to contribute to the study of the purification of germanium in the slag of the pyrometallurgy of the GCM factories of Lubumbashi. To do this, a pre-treatment of the slag was done by drying at 105°C for 24 hours and a grindability study using a sieve whose mesh was 75mm maximum for 90 minutes. The moisture content was 0.52%, the grinding time 90 minutes to obtain 89% of passers-by. Initially, the slag assayed 0.02% Ge; 0.008% Ga; 5.4% Cu; 0.21% Co; 10.40% Zn; 10.30% Fe and 10.30% Si.

Our concern to recover the germanium from the slag with the other accompanying metals was to carry out the tests for dissolving the slag with oxalic and sulfuric acids after having characterized it. This slag was shown to be acidic and without a defined crystalline structure. The various dissolution tests were carried out by varying the quantity of oxalic acid for the preparation of the oxalic acid solution (100 to 150g/L), the leaching time (1h to 4h). The ratio between the amount of slag and the acid solvent was 1÷10 respectively. At this stage of our study, the optimal conditions for the dissolution of germanium were 4 hours of leaching at 40°C with one liter of acid solution of 125g/L for 100g of slag to obtain a yield of 98% of the Ge and a low yield of 42% Cu, 41% Co and 11% Zn. The low leaching yield observed for the other metals is explained by the high silica content of 10.30%. Indeed, the silica leads to a gel trapping the metals and preventing them from going into solution.

This is how we considered the elimination of silica by choosing the procedure using citric acid by varying the concentration in g/L of acid and the leaching time.

The optimal conditions were the use of one liter of aqueous citric acid solution consisting of 75g/L for 30 minutes of agitation in contact with 100g of slag to eliminate up to 99% of the silica. This process was followed by sulfuric acid leaching tests. The optimal conditions set was the preparation of one liter of acid solution of 122g of sulfuric acid to leach, in 2 hours, 150g of slag, i.e. a solid-liquid ratio of 15÷100. Leach results were 94% Ge, 91% Cu, 85% Co and 91% Zn.

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