Solvent extraction and ion exchange
Solvent extraction and ion exchange are both very powerful separation and purification methods used for the recovery of metals. While solvent extraction is a very simple, rapid, and selective method involving organic solvents, ion exchange uses resin technology to selectively recover metals down to very low concentrations. These proven separation technologies have and continue to play a significant role in mining, refining and effluent treatment industries. The efficiency of solvent extraction and ion exchange can be optimized based on specific solution compositions and operational objectives.
Ion exchange processes allow for purification and concentration of targeted ions from solutions for selective recovery. Examples include separation of nickel from cobalt, separation of palladium from silver, copper from chlorides or mine waste waters and nickel from electroless nickel solutions. In most cases the ion exchange units are self-contained, skid mounted and controlled by PLC. The relatively simple operation of ion exchange on a small scale vs solvent extraction makes the technology ideally suited for rapid set up in small to medium sized operations.
Variations such as continuous ion exchange and fluid bed ion exchange offer advantages over conventional fixed bed ion exchange for solutions with suspended solids and minimizing rinse waters used in the ion exchange process.
Solvent extraction has been used for over 50 years in the copper industry for concentration of purification of copper solutions for electrowinning. Many different extractants and diluents are available to suit a wide variety of target metals and solutions.