The selective separation of trace components of interest from various mixtures (e.g., micropollutants from groundwater, lithium or uranium from seawater, carbon dioxide from air) presents an especially pressing technological challenge. Established materials and separation processes seldom meet the performance standards needed to efficiently isolate these trace species for proper disposal or re-use.
To address this issue, researchers at UC Berkeley developed a novel separation strategy in which highly selective and tunable adsorbents or adsorption sites are embedded into membranes. In this approach, the minor target species are selectively captured by the embedded adsorbents or adsorption sites while the species transport through the membrane. Simultaneously, the mixture can be purified through traditional membrane separation mechanisms.
As a proof-of-concept, the researchers incorporated Hg2+-selective adsorbents into electrodialysis membranes that can simultaneously capture Hg2+ via an adsorption mechanism while desalinating water through an electrodialysis mechanism. Adsorption studies demonstrated that the embedded adsorbents maintain rapid, selective, regenerable, and high-capacity Hg2+ binding capabilities within the membrane matrix. Furthermore, when inserted into an electrodialysis setup, the composite membranes successfully capture all Hg2+ from various Hg2+-spiked water sources while permeating all other competing cations to simultaneously enable desalination. Finally, using an array of other ion-selective adsorbents, the Berkeley team showed that this strategy can in principle be applied generally to any target ion present in any water source. This multifunctional separation strategy can be applied to existing membrane processes to efficiently capture targeted species of interest, without the need for additional expensive equipment or processes such as fixed-bed adsorption columns.
This invention can be applied for the selective capture of targeted minor components in essentially any existing industrial process that uses membranes, provided that traditional membranes used in these processes are instead replaced with adsorbent-based membranes as detailed in this invention. Tunable multifunctional membrane processes pioneered by this invention can also obviate the need for additional industrial adsorption units, such as pressure swing adsorption or temperature swing adsorption technologies. Examples of potential applications and variations of the described invention include, but are not limited to, the following:
1. Selective recovery of targeted ions (e.g., organic ions, charged dyes, heavy metals, lithium, charged water pollutants) in liquid mixtures via charge-based separations.
2. Using principles developed in this invention, selective adsorbents can additionally be mixed directly into porous electrodes to capture target ions that transport into the electrodes.
3. Selective recovery of charged or uncharged solutes using a solute-capture diffusion dialysis or solute-capture Donnan Dialysis approach implemented with adsorptive membranes.
4. Selective capture of contaminants in fuel cell operations.
5. Selective removal of contaminants in gas mixtures.
6. Selective capture of CO2 from the atmosphere.
7. Selective capture of dissolved CO2 or CO2-derived compounds (e.g., HCO3−) from water.
8. Selective capture and recovery of target compounds (e.g., contaminants or high-value compounds) in liquid mixtures using adsorbent-modified microfiltration, ultrafiltration, nanofiltration, or reverse osmosis membranes.
9. Selective removal of toxins from blood.
10. Selective capture of target compounds in organic liquid mixtures using adsorbent- modified pervaporation or membrane distillation membranes.
11. As a variation to the materials and processes innovated by this invention, membranes with tunable catalytic sites, rather than tunable adsorption sites, can be developed using principles created in this invention.
12. This invention can also be used as a pretreatment or post-treatment step in various industrial processes, to partially or completely reduce the concentration of targeted components from mixtures.
13. This invention can additionally be applied as a replacement unit to existing fixed-bed adsorption columns for improved separations.
14. As an analogous variation to the adsorbent-based membranes described in this invention, multiple different types of selective adsorbents or adsorption sites can be incorporated into the same membrane.
Highly Selective Separations, Resource Recovery, Water Purification, Dialysis