Comparison Of Gold Recovery From High-Grade Ore Of Gua Musang, Kelantan Using Aqua Regia And Bioleaching Methods

Chemical extraction of gold from refractory gold ore containing gold-bearing minerals has the potential to pollute water, air, and land. Therefore, another method should be developed to overcome this problem. Thus in this study, the bioleaching approach has been studied, which is more environmentally friendly and less expensive than chemical extraction to recover gold from refractory gold ore. The efficiency of Aqua regia as chemical extraction and bioleaching methods was studied by comparing gold recovery in both methods. To conduct the bioleaching process, we were used Shewanella oneidensis MR-1 as bio-reduction agent which is known to reduce Ferric ion (FeSt) to Ferrous ion (Fe2+). The determination of Iron (I) concentration was carried out using a Ferrozine assay at optical density 562m. The mixture of Nitric Acid and Hydrocholoric Acid (1:3; v/v) called Aqua regia was used to digest the gold ore samples. For analysis, Benchtop X-ray powder diffraction (XRD) D2 phaser model was used to characterise the high-grade, high-sulphide gold ore samples, meanwhile Indicatively coupled plasma mass spectrometry (ICP-MS) was used to determine the concentration of Aurum (gold). The result of XRD analysis show the ore was predominantly associated with Quartz, Graphite and Bernilite. The highest gold recovery for bio-reduction methods are on the sample namely MD
0174 ALI which recorded from 56% to 91% compared to Aqua regia methods which recorded only 41%. In addition, we found bio-reduction also influences the degradation of other minerals, which resulting decrease in pyrite mineral in all the samples. As a conclusion, the finding of this study has proven that bio-reduction using S. oneidensis MR-1 can be used to recover gold, however further study should be carried out to develop detailed mechanism of this process.
Keywords: Bioleaching, Bio-reduction, Iron Oxide, X-ray Diffraction (XRD), Indictively Coupled Plasma Mass Spectrometry (ICP-MS).