Gold stripping by hydro-alcoholic solutions from activated carbon: experimental results and data analysis by a semi-empirical model

The aim of this work was to study gold stripping from activated carbon using a range of different alcohols (isopropanol, ethanol and ethylene glycol). The experimental work was carried out on a laboratory scale, using activated coconut carbon, at 40 to 80 °C and up to 8 h extraction time. Isopropanol was the most rapid eluent with N98% Au eluted after 1 h at 80 °C, ethylene glycol had a similar extraction after 2 h, ethanol was the least effective with 5 h required for N95% extraction. Interestingly, 77% Au extraction was obtained at 40 °C using ethylene glycol. A second order semi-empirical model was used to successfully describe the stripping. The activation energies were N57 kJ/mol, indicating that desorption was rate determining. The following order of the estimated kinetic constants has been observed at any investigated temperature: KisopropanolNKethylene glycolNKethanol indicating that isopropanol was the best organic compound for the gold stripping process among the selected compounds investigated in this work. From a practical viewpoint, the non-flammability of ethylene glycol makes it the most attractive.