Investigating the Performance of Ghana’s Locally Produced Alcohol (Akpeteshie) in Stripping Gold-Loaded Carbon

Abstract

Gold adsorbed unto activated carbon is recovered downstream via various stripping techniques paramount among which are the Zadra elution method and the Anglo American Research Laboratory (AARL) method before final gold recovery by electrowinning. These conventional stripping systems require a relatively higher temperature and longer elution hours. These are effective but the relatively longer extraction times that accompany them have been a major concern over the years. This has encouraged diverse research operations to ascertain an alternative method of elution that would render the process more economical. One research finding that has been very successful in reducing the extraction time significantly is alcohol stripping. Laboratory produced ethanol, methanol, isopropanol, and ethylene glycol have all proven to be effective in stripping gold from loaded carbon at elevated temperatures. One main hindrance to the usage of this method at the commercial scale is the relatively higher cost of ethanol among other operational and environmental challenges. This work investigates the performance of Ghana’s locally produced alcohol (akpeteshie) in stripping of gold from gold-loaded carbon at lower temperatures with the aim of finding an alternative method for gold stripping which might be cheaper than conventional systems. Cost analysis conducted revealed that akpeteshie is relatively cheaper than laboratory-produced ethanol. This was one of the key motivations of the research work. A range of different strip solutions were used (hydro-ethanol, caustic solution and lastly caustic and ethanol mixture). The experimental work was carried out at the laboratory scale, using gold-loaded carbon at room temperature and at 60 and 70 °C temperatures respectively and up to 8 h extraction time. Hydro-ethanol was the most rapid eluant with 66% Au eluted after 8 h at 70 °C, followed by the ethanol and caustic mixture which yielded 42% extraction after 8 h. Caustic was the least effective with 8 h required for a 20% extraction yield. Interestingly, 92% Au extraction was obtained at 70 °C when hydro-ethanol was used as an eluant to strip fine carbon.