Removal of Heavy Metals by Polymer Inclusion Membranes

Heavy metals cannot be biodegraded and they remain in the environment until being removed. Thus, the removal of heavy metals from contaminated water is of special concern for the protection of human and aquatic lives. Studies on polymer inclusion membranes (PIMs) started more than 50 years ago and have shown outstanding separation performance of metal ions. The potential and capabilities of PIMs have made it more favorable than ion exchange and liquid-liquid extraction process. To achieve efficient transport of metal ions, different types of extractant with compatible base polymer have been successfully used along with suitable targeted metal ions. However, selectivity of metal ion is only limited to one type of metal ion based on the extractant used in PIMs. The present review describes the current literature on heavy metal removal using PIMs for the past 3 years. The compatibility of extractant with base polymer and plasticizer is discussed. Most of PIM studies used cellulose triacetate (CTA) and polyvinyl chloride (PVC) as the base polymer, and only a few studies have used other base polymers. These new base polymers have shown better PIMs in terms of stability and separation performance compared to the CTA- and PVC-based PIMs. Moreover, a new invention of dual PIM separation system has allowed simultaneous separation of multiple metal ions. Such improvement in PIM technology can speed up commercialization process and make it viable for large scale and industrial use especially in hydrometallurgy and wastewater treatment.