Abstract
The present work is focused on the performance of three types of coal-oil agglomerates on recovery of liberated gold from gold bearing materials. Pre-formed agglomerates developed using bio-diesel, castor oil and mineral diesel as liquid hydrophobic phases were used in the study. The influence of the type of liquid hydrophobic phase on the degree of gold recovery and the effect of factors such as gold particle concentration, viscosity, agglomerate size, agglomerate/ore ratios and particle penetration into agglomerates have been studied as a function of time. It is shown that gold recovery rate can be increased by an increase in agglomerate loading, surface area and the viscosity of the hydrophobic phase and high recoveries are attained up to 98.5%. Increase in concentration of gold particles per unit volume of slurry increased attachment rate but did not change the final recoveries attained. It is shown that gold particle penetration occurs mainly in the coarse agglomerates if contact is prolonged beyond 60 minutes. Examination of sections of gold-loaded agglomerates under reflected light microscope showed gold and some silicate particles penetrated in few cracked agglomerates and only gold particles were observed inside the uncracked agglomerates suggesting the possibility of gold selectivity during particles penetration. It was shown that the increase in gold recovery attained at prolonged contact time is due to both gold penetration and oleophilic attachment.
Highlights
Many researchers in the area of extractive metallurgy and chemical engineering have reported the possibility of gold recovery by coal-gold-oil agglomeration method, which is a potential alternative to the mercury amalgamation
B) Gold bearing materials The gold bearing materials used in the study contained classified fine quartz (100% - 150% microns) and metallic gold powder minus 150 microns originating from small scale mining areas in Chunya, Mbeya Region Tanzania. c) Reagents Potassium Amyl Xanthate (KAX) commercial yellow pellet form-water soluble, Hydrochloric acid (HCl) and Nitric acid (HNO3)
The results showed that low agglomerate/ore ratios required prolonged contact time for completion of gold recovery
Summary
Many researchers in the area of extractive metallurgy and chemical engineering have reported the possibility of gold recovery by coal-gold-oil agglomeration method, which is a potential alternative to the mercury amalgamation. The hydrophobic recovery of gold using agglomerates is environmentally seen as the best alternative to mercury amalgamation in small scale mining [3]. The positive results from previous research works on coal-oil-gold agglomeration [4,5,6,7,8,9,10,11] and the promising environmental and technical viabilities of the process [12] have raised the need for adoption of this method in small scale mining in Tanzania where the hazardous use of mercury is still dominant [13], and was the motivation for doing this research. The sophistication of the operation in terms of types of hydrophobic materials used and the handling of the effective variables [8,9,10] compared to mercury amalgamation has been addressed
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