Production of a Highly Concentrated Gold Solution from Aqua Regia Gold Leachate Using Sugarcane Bagasse Nanoparticles

This study produced a highly concentrated gold solution using nanoparticles (NPs) synthesized from sugarcane bagasse as an adsorbent for gold(III) recovery from an aqua regia gold leached lean solution. A 100 kg sample of gold ore collected from a mining site in Iperindo was concentrated. Mineralogical characterization and a fire assay test of the ore were carried out. Atmospheric and agitation leaching were conducted using aqua regia. Sugarcane bagasse NPs were prepared and used to study the gold(III) adsorption kinetics. Gold-loaded sugarcane bagasse NPs were desorbed in a 4 M aqua regia solution. The results revealed that the ore has a low water retention capacity which renders it friable. A microscopic examination established the presence of gold particles and pyrite in the ore. Ore leaching was eminently favoured by agitation yielding a weight loss of 6.3 % when an acid concentration of 4 M was used, the temperature was 90 ºC and the leaching time was 30 minutes. Synthesized nanocellulose was able to adsorb gold(III) from the leachate optimally with the following process parameters: 14 mL/g of adsorbent, 106.2 minute-long contact time, a temperature of 56 ºC and an agitation rate of 45 rpm when the concentration of leachate was 84 mg/L. The adsorption efficiency of the sugarcane bagasse NPs is comparable with that of commercial activated carbon, namely 92 and 95 %, respectively. The study concluded that NPs synthesized from sugarcane bagasse could be effectively used when upgrading gold and in purification processes.