RECOVERY OF PRECIOUS AND RARE EARTH METALS USING CYCLODEXTRIN

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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+r where n is the valency of the oxidised metal ion Mn+; 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+i in solution; d) adding cyclodextrin to the alkali metal/metal bromide solution to precipitate a metal cyclodextrin complex; and e) recovering the metal cyclodextrin complex.