The extraction of Au(III) from hydrochloric acid solutions by microemulsion was studied. The extraction experiments were carried out using cetyltrimethylammonium bromide (CTAB) as surfactant and isoamyl alcohol as co-surfactant. Au(III) was found to be extracted into the microemulsion phase due to ion pair formation such as AuCl(4)(-)CTA13(+). The influence of temperature on the extraction of Au(III) has been investigated at temperatures ranging from 288 to 313 K. Temperature was found to decrease the distribution of Au(III). Thermodynamic parameters like enthalpy and entropy of the extraction, calculated by applying Van't Hoff equation, were -36.76 kJ mol(-1) and -84.87J mol(-1) K-1, respectively. Furthermore, the influence of the concentrations of hydrogen ion and chloride anion on the extraction efficiency (E%) were verified. Au(III) was extracted quantitatively (E% > 99%) and selectively at the whole range of HCl concentrations (0.2-5 M). Recovery of gold from electrical waste and treatment of CTAB wastewater generated from the extraction were also discussed. Thus, the extraction of Au(III) from hydrochloric acid solutions by microemulsion is an effective approach. (C) 2010 Elsevier B.V. All rights reserved.