The reactivity of Mixed sulfide (MS: mixture of nickel and cobalt sulfides) in the conventional media remains insufficient and may be
further improved. The authors have developed a novel leaching method using organic aqua regia, i.e. dimethyl sulfoxide (DMSO) solutions of
copper chloride (CuCl2). In this work, the organic aqua regia was applied for the leaching of MS. Then, the recovery of Ni from the leachate
was conducted by a biphasic extraction, during which commercial extractants of PC–88A were used. It was found that the extraction of Ni and
Co at a given time was faster than that of conventional media, e.g. 94ÿ in 1 h at 393 K. One of the advantages of DMSO as a solvent is its
high boiling point, which allows a high operating temperature at ambient pressure, leading to high extraction rate. The results of the biphasic
extraction show that approximately 80ÿ of Cu remains in the leachate whereas 70ÿ of Ni goes to PC–88A. The leaching by organic aqua regia
followed by the biphasic extraction could be a novel and attractive method to recovery Ni from MS.