Awaruite (Ni3Fe) as a nickel resource—leaching with ammoniacal–ammonium solution containing citrate and thiosulfate

A method was developed for extraction of nickel from ultramafic rocks containing awaruite, an alloy of nickel and iron (nominally Ni3Fe). The leaching solution contained ammonia, ammonium, citrate and thiosulfate at moderately alkaline pH. Leaching studies were carried out on synthetic Ni3Fe, josephinite (a naturally occurring material consisting mainly of awaruite from Oregon, USA) and serpentinite containing low levels of awaruite from British Columbia, Canada. In addition to citrate, several other carboxylic acid ligands were also found to be suitable for this process.