Abstract: A new method for purification of trivalent chromium electroplating baths contaminated with cationic metal ions is disclosed. In this purification process, the contaminated trivalent chromium is passed at the pH level of the bath through one or more columns containing an ion-exchange resin having the picolylamine group as the functional moiety. The cationic metal ions are preferentially bound to the resin while the trivalent chromium is passed through the resin with substantially no adsorption thereby purifying the electroplating bath. This process is preferably performed simultaneously with the electroplating process.

Abstract: An improved process for stripping gold cyanide from activated carbon is disclosed. The process involves contact of gold-laden activated carbon with a strong base at ambient temperatures followed by elution with an aqueous solution containing an organic solvent, preferably aqueous acetonitrile or methanol. Gold cyanide is separated from the aqueous/organic solution by ion-exchange technology, preferably using a weak base ion-exchange resin, followed by elution with a strong base.

Abstract: A composition for removing metal ions from aqueous solution is prepared by immobilizing metal ion-binding microorganisms such as algae, washing the immobilized microorganisms, drying the washed immobilized microorganisms and heating the dried immobilized microorganisms to a temperature of about 300.degree. to about 500.degree. C. for a time sufficient to provide a stable composition that is non-swelling in aqueous solution. The composition preferentially adsorbs precious metal ions from an aqueous solution containing concentrations of base metal ions and/or other dissolved materials several orders of magnitude greater than the concentration of the precious metal ions. The composition can also be used to extract precious metal ions from geothermal fluids.