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 new process for removal of a metal ion from an anionic complex, including a first chelating agent and a metal ion, such as copper, nickel or cobalt ion, in electroless plating bath rinse streams utilizes a cation exchange resin to extract the metal ion from the rinse stream after the metal ion has been removed from the anionic complex and complexed with a second chelating agent.In another embodiment, a competing chelating agent is not added to the electroless plating bath waste stream, but rather, another metal ion (B), which has a higher affinity for the chelating agent than the metal ion (A) of interest and which is nontoxic, is added to the waste stream. Metal ion B is selected so that under predetermined conditions, metal ion B forms a stronger complex with the chelating agent than does metal ion A. Also, the complex of the chelating agent and nontoxic metal ion B is anionic. A cation exchange resin is used to extract metal ion A from the treated waste stream.

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.

Abstract: The present invention relates to a method for the selective extraction of the metals gold, silver, platinum or mercury ions or colloidal gold, from an aqueous solution containing at least one of these metal ions which comprises contacting the solution, at a pH of 2 or less, with cells or cell extracts of a microorganism capable of binding these metals for a period of time and under conditions sufficient to allow binding of the metals to the cells or cell extracts.

Abstract: The present invention comprises a simple multi-purpose on-line system for monitoring the concentration and/or the total amount of an organic analyte species or inorganic analyte species in an aqueous solution. The on-line detection system comprises a detection column and a sensor mounted around the detection column. The sensor consists of an electromagnetic radiation source (typically a light source) and an appropriate detector for the electromagnetic radiation. The response from the detector drives an electric circuit, which provides a signal to a recorder as well as a means to trip an alarm system and/or a process system.