Solvent-free extraction of metal ions from highly toxic aqueous waste streams

A method for generation and use of polymeric capsules for solvent-free extraction of metal ions in applications such as waste remediation, metal recycling, etc.
Technology No. 2019-384
IP Status: US Patent Application Filed; Application #: 17/003,538


  • Separation of metal ions from solution
    • Waste remediation, including nuclear waste
    • Metal production
    • Metal recycling

Key Benefits & Differentiators

  • Organic-solvent-free processing: use of facilitated transport membranes eliminates additional safety and environmental concerns posed by organic solvents.
  • Sharply reduced mass requirements: Modeling demonstrates nearly 10,000-fold less ligand is required than for solvent extraction
  • Ability to use size-based separation: Following capture of target metal ions, non-target ions could be rapidly and completely separated via membrane filtration
  • Ability to pack in columns: Microcapsules can be readily packed in columns to allow for simple and rapid flow-through processing
  • Does not require heat-based pyrometallurgical processes that are environmentally hostile
  • Potential to recover multiple metals in a single device: Future developments could include customizing polymeric capsules to enable multiple metal recovery

Limitations of current metal extraction methods

When dissolved as ions in water, metals can be highly hazardous to human and environmental health (e.g., lead, mercury, radioactive species). Selective separations of metals are critical to efficient metal production and environmental management. Liquid-liquid extraction is the state of the art for selective separations of metals in aqueous solutions; however, it requires hazardous organic solvents, is susceptible to significant loss of solvent and ligand, and is limited by the equilibrium established during extraction and stripping steps. While facilitated transport is considered as a better alternative, currently available methods are highly unstable.

Solvent-free metal-selective polymeric capsules

Prof. Marc Hillmyer’s group at the University of Minnesota has developed a novel solvent-free metal ion extraction method using stable polymeric capsules to achieve facilitated transport. The capsule has inner aqueous chamber(s) containing strip solution surrounded by a polymeric shell containing lipophilic ligand. Presence of lipophilic ligands in the shell allows for selective transport of target ions from the external solution to the inner chamber(s). This method theoretically requires up to 10,000-fold less metal-specific ligand, enables subsequent use of size-based separation techniques, and eliminates the need for any organic solvents. Modeling suggests significant increases in efficiency, with approximately 99% extraction of target metal ions in minutes. Experimental prototypes with copper-selective microcapsules packed in columns enabled >99% copper removal with a column residence time of ~2 minutes. Owing to the facilitated transport approach, total copper removal was up to ~75-fold greater than possible for extraction with the corresponding ligand mass. This approach has the capacity to transform metal production/recycling and waste remediation, especially with regard to nuclear waste.

Phase of Development

TRL: 3-4
Modeling has demonstrated the viability of the technology and an experimental prototype has been developed. A manuscript describing the experimental prototype is in preparation.

Desired Partnerships

This technology is now available for:
  • License
  • Sponsored research
  • Co-development

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