Bacterial leaching of complex sulphides from mine tailings altered by acid drainage

in Dominic, Esteban (Ed.) Bacterial leaching of complex sulphides from mine tailings altered by acid drainage (2009, May)

An experimental study aimed at re-flotation of laid down tailings from Kipushi (DRC) to bring sulphide concentrate suitable for further processing by hydrometallurgical means has been realized. The ... [more ▼]

An experimental study aimed at re-flotation of laid down tailings from Kipushi (DRC) to bring sulphide concentrate suitable for further processing by hydrometallurgical means has been realized. The results from a bioleaching route chosen to accomplish the later task by use of moderate thermophilic and mesophilic microorganisms are reported. It has been found that due to the complexity of the treated material, the leaching pattern of the two principal metals of interest, copper and zinc vary. Whilst the copper bearing minerals have been leached relatively fast by direct mechanism, the leaching kinetics for the zinc minerals has been moderate involving predominantly an indirect mechanism. The effects of pH and temperature variations and ferrous ions addition upon the extent of copper and zinc dissolution have been examined. The presence of ferrous ions has been found beneficial for the leaching of sphalerite, however the concomitant formation of jarosite precipitates has led to copper leaching hindrance. Similarly, the rapid zinc solubilisation has been counterbalanced by decrease in rate of copper dissolution. [less ▲]

The roles of complexing agents in the sulfidisation and xanthate flotation of cobalt oxy hydroxides of copper-cobalt oxides ores from the Congolese Copperbelt

Conference (2006)

Complex mineralogy combined with a variable chemistry lead to various flotation responses of cobalt oxy-hydroxides present in oxidised and mixed copper-cobalt stratiform deposits of the Central African ... [more ▼]

Complex mineralogy combined with a variable chemistry lead to various flotation responses of cobalt oxy-hydroxides present in oxidised and mixed copper-cobalt stratiform deposits of the Central African Copperbelt. Optimum metallurgical results require very high dosages of reagents and the management of such high chemicals concentrations in the pulp at the plant scale is delicate. The transition period between high reducing conditions during the sulfidisation step and a more oxidising environment prevailing during collector adsorption is particularly critical. This paper demonstrates how the use of copper and cobalt complexing agents can significantly improve the process control and metallurgical performance. The different modes of action of these reagents are presented and mechanisms for the various reactions proposed. Plant results following the introduction of ammonium sulfate at the New Concentrator of Kipushi are discussed. [less ▲]

Ammonium sulphate as promoting agent of the sulphidization process of oxidized Cu-Co ores from the Luiswishi deposit (RDC)

Poster (2003)

The Luiswishi deposit belongs to the Cu-Co deposits of the Southern Group of the Katangian Copper Belt and is operated by a joint venture between EGMF (Entreprises Générales Malta Forrest) and Gecamines ... [more ▼]

The Luiswishi deposit belongs to the Cu-Co deposits of the Southern Group of the Katangian Copper Belt and is operated by a joint venture between EGMF (Entreprises Générales Malta Forrest) and Gecamines (Générale des Carrières et des Mines). The Cu-Co ore is beneficiated by the sulphidization process at the NCK (New Concentrator of Kipushi) at Kipushi. Sulphidization followed by flotation with sulphydryl collectors is a common practice for the treatment of oxidized base metals ores. This process is complex and its application at the industrial scale is quite sensitive. In Central Africa it is also a cost intensive treatment as the sulphidizing agent has to be imported. In order to improve the metallurgical performances and to optimise the economics of the process, a laboratory research program was carried out by the Laboratory of Metallurgy and Mineral Processing (MTM) of the University of Liège in close collaboration with EGMF and Gecamines. This program included the study of various flotation reagents as dispersing, depressing and activating agents. This paper presents the results obtained with the use of ammonium sulphate as activator of the sulphidized xanthate flotation. Although ammonium sulphate has been mentioned in the literature as a promoting agent of the sulphidized xanthate flotation of malachite, its effects on the flotation of cobalt oxides was not known. The testworks were carried out on various oxidized siliceous ore types from the Luiswishi deposit. A 1.7 l Agitair laboratory flotation cell was used. NaHS and potassium amylxanthate were respectively choosen as sulphidizer and collector. A mixture of gasoil and tall oil (90/10) was used as secondary collector. A multistage sulphidization was realised. Values of pH were followed during the different tests and an ion selective electrode Ag/Ag2S was used to control the Es potentiel evolution during the stepwise addition of the sulphidizer. The addition of ammonium suphate [(NH4)2SO4] simultaneously with NaHS led to the following results: -A marked improvement of the sulfidization kinetics leading to shorter conditioning times and limiting the number of sulphidizing stages required to reach maximum recoveries. -The inhibition of the depressive effect on Cu and Co flotation of an excess of hydrosulphide ions in the pulp. -An improvement of the selectivity of the flotation combined with higher cobalt recoveries. The promoting effect is indeed more effective for cobalt than for copper and cobalt recoveries were improved by 4 to 8 %. -A significant decrease of the sulfidizer consumption. These laboratory results were implemented at an industrial scale at the NCK at Kipushi. In close accordance with the laboratory results the sulphidization kinetics were improved and the cobalt recoveries rose by 7 % while maintaining the previous Cu and Co grades of the concentrate. Ammonium sulphate being a low cost and common reagent (it is easily found in the fertiliser industry or as a byproduct of the coke industry), its use significantly improved the economics of the flotation of Cu-Co oxides ores from the Luiswishi deposit. [less ▲]

Utilitation des nodules océaniques polymétalliques en hydrotraitement des coupes pétrolières lourdes avant leur valorisation métallurgique

in L'industrie minérale - Mines et Carrières - Les techniques (1986), 68