Solvent Extraction of Gold from Hydrochloric Acid-Leached Nigerian Gold Ore by Tributylphosphate

This paper presents an experimental study on the dissolution kinetics and solvent extraction of total gold from Ijero-ekiti (Nigeria) gold ore deposit by hydrochloric acid leaching followed by extraction with Tributylphosphate (TBP) in kerosene. The leaching investigation showed that the gold ore dissolution in HCl solution increases with increasing acid concentration, temperature and with decrease in particle diameter at a stirring rate of 300rpm.The kinetics data has been analyzed and was found to follow diffusion control mechanism with surface chemical reaction as the rate limiting step. About 81.27% of the initial 10g/L of the ore concentrate was dissolved within 120 minutes by 2M HCl solution at 80C using 0.09<Φ<0.12mm particle diameter. The analysis of the residual product (18.73% of the initial gold ore) shows that it consists primary of α–quartz. Furthermore, the solvent extraction studies revealed the extraction efficiency of about 85.28% by TBP in kerosene. This was determined by analyzing the orange-red complex of gold with 4-(2-pyridylazo) resorcinol (PAR) spectrophotometrically at 450 nm from the ore leach liquor at optimal conditions. Finally, the calculated enthalpy and entropy change of 3.56kJ/mol and -21.83J/mol/K were obtained for the extraction system, respectively.