Abstract
In this paper, the effect of gangue minerals on the hydrophobic recovery of gold is being investigated using ores obtained from the active small scale gold mining sites in Tanzania. Gold ores of different gangue contents were tested. The effects of silica gangue and high sulphide gangue on gold attachment were examined including the effect of surface activators (potassium amyl xanthate) and the possibility of depressing the effects of gangue using reagents. The results were evaluated in terms of gold recovery, volumes and grade of concentrates formed. There was no change in gold recoveries when the amount of oxide gangue (quartz) in the ore was increased, indicating absence of competition between gold and quartz gangue. High sulphide contents in the ore above 6% reduced gold recoveries considerably. It was noted that potassium amyl xanthate surfactants increased the attachment of both gold and the sulphide gangue. Using lime at pH 10 it was possible to depress the sulphide gangue which is mainly pyrite and hence increased gold recoveries considerably.
Highlights
The presence of gangue minerals in gold ores is among the main reasons for the selection of appropriate gold recovery method
The effects of silica gangue and high sulphide gangue on gold attachment were examined including the effect of surface activators and the possibility of depressing the effects of gangue using reagents
The tests were carried out in the following procedures: (i) Wetting 100 g of gold bearing material with 500 ml de-ionized water surfactants such as potassium amyl xanthate was added and/or depressants such as lime was added agitated for 3 - 5 minutes followed by (ii) addition of the agglomerate sample and stirring for a given time; (iii) Screening the mixture on a 0.325 mm sieve in water to separate the gold-loaded agglomerates from the pulp; (v) Drying agglomerates in open air for 6 hrs and weighing them assessing the recovery of gold by analyzing the amount of gold attached to agglomerates
Summary
The presence of gangue minerals in gold ores is among the main reasons for the selection of appropriate gold recovery method. The common gangue minerals which are normally associated with gold ores include quartz, fluorite, calcite, pyrites, chalcopyrites, galena and many others in small amounts e.g. arsenopyrites, fluorites, carbonates and chlorites [1,2]. It is known that some of the gangue minerals that are associated with gold have oleophilic and hydrophobic properties and the presence of such mineral gangue in the ore may be a source of competition during the attachment to agglomerates. Such minerals include mainly the metallic sulphides gangue [3,4]. The presence of low amounts of sulphides in the ore up to 5% chalcopyrite is reported to have little effect on gold recoveries [5,6]
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