Separation of Osmium from Liquid Media
Osmium is the densest naturally-occurring element and has many important uses ranging from fountain pen tips to precision electrical contacts. Osmium (particularly Os4+) can be grouped with the platinum group metals (PGM) because it forms stable oxyanion complexes.
Many mining projects are underway in which ores are leached under oxidizing and acidic conditions. Under these conditions, DuPont Anion Exchange Resins have proven to be tough, steady performers.
In chloride solutions osmium forms very stable chloroanion complexes which are readily adsorbed on strong base anion exchangers such as AmberSep™ 21K XLT Resin. Interestingly, like the PGMs, osmium is also strongly adsorbed on weakly basic anion exchange resins such as AmberLyst™ A21 Resin. Weakly basic anion exchangers are often effective in their conjugate acid forms (in acidic media) or in their free-base forms (neutral ligand-metal complexes). Elution of osmium from the resin can generally be accomplished with dilute acid solutions that do not elute other platinum group metals. Fuming of osmium loaded resins is not recommended as the volatile osmium can carry away other PGMs.
Additional information about the recovery of precious metals from acidic halogen leach solutions and about fuming can be found by visiting our Answer Center
Caution: Osmium (Os) compounds are generally volatile (some sublime) and are extremely toxic. As with all metal solutions, those containing Os should be handled using appropriate personal protection.