This invention relates to methods for the recovery of precious metals such as gold, silver, platinum, palladium and rare earths from precious metal-bearing materials.
In particular, a method of purifying precious metal from a precious metal-bearing material comprising the steps a) forming an aqueous acidic oxidant mixture from hydrogen peroxide an acid and a source of bromide ion, said acidic oxidant mixture having a pH in the range 0 to 6; b) contacting the acidic oxidant mixture with the precious metal bearing-material to oxidise the metal and form a metal bromide salt solution containing the metal bromide MBrn and/or [MBrn+1]− where n is the valency of the oxidised metal ion Mn+; and c) controlling the metal bromide salt solution to a value in the range 3-7 by providing alkali metal ions A+ in the solution to form an alkali metal/metal bromide solution containing the salt AMBrn+1 in solution.