Synthesis of new phosphonate ester resins for adsorption of gold from alkaline cyanide solution

Resin ion-exchange technology is a possible alternative to well-established gold recovery processes of carbon adsorption and zinc-dust cementation. The search for a suitable resin for gold recovery from alkaline cyanide solution continues at several research centers. Recent discoveries involving alkyl phosphorus esters for selective gold solvent extraction from alkaline cyanide solution suggest that similar chemistry on a resin substrate might likewise be effective. In this regard, polystyrene-supported phosphonate ester-based resins were synthesized from the poly(styrene/divinylbenzene) copolymers. Gold adsorption/desorption characteristics were established for these resins with respect to functional group chemistry, pH, ionic strength, and temperature. Gold loading was found to be promoted at increased ionic strength with fair selectivity over various cyanoanions. Stripping was possible at higher temperatures and/or low ionic strength of the strip solution. Solvation extraction of an alkali cation/aurocyanide anion ion pair seems to explain the adsorption/desorption phenomena which are discussed in terms of the variables studied.