Concentrating and Separating Analytes via Bipolar Electrode Focusing
Nanotechnologies : Physical Science Apps
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- Richard Crooks, Ph.D. , Chemistry and Biochemistry
- Jan Clausmeyer , Department of Chemistry
- Collin Davies , Department of Chemistry
Clean drinking water is essential to the survival of the human race. While the human population steadily continues to increase, drinking water is a limited resource. Although there is a large volume of water stored on the earth covering 70% of the earth’s surface, most of the water contains salts at high concentrations--making the water unfit for human consumption.
In fact, while roughly 2% of the earth’s water is considered fresh water, less than 1% of the fresh water is easily accessible, with the majority of the resource trapped in glaciers and snowfields. For this reason, exploration of the removal of salt from saltwater, or desalination, seeks to expand the world’s accessible, fresh water supply.
The desalination of saltwater proves to be an energy intensive process. The primary technology for water desalination today relies on high pressure differences across nanoporous membranes, which permit the selective passage of water molecules across the membranes while rejecting salt ions. In addition to operational expenditures, membrane-based techniques are prone to failure in the form of membrane fouling. Considering the operation, maintenance, and infrastructure requirements of present technologies, many in most dire need for fresh water cannot afford to desalinate water.
Researchers at The University of Texas at Austin have developed an electrochemical technique (bipolar electrode focusing) for the manipulation of ionic species in solution. In general, a saltwater solution is directed past an ion intercalation material within a microfluidic system. Under an applied electric field, the ion intercalation material intercalates ions present in solution, reducing the concentration of ionic species downstream of the intercalation material. Consequent to the formation of a local ion depletion zone (IDZ), an elevated electric field gradient forms local to the IDZ and may be used to manipulate ionic species. By altering the design and configuration of the microfluidic system, enrichment, redirection, and separation of ionic species may be achieved.
- Use of intercalation materials offers high selectivity as to which ions are inserted into the material, offering ion extraction from solution and energy storage capabilities.
- Ion intercalation materials fabricated as reported here offer simple and flexible fabrication for system scalability or modification.
- Modular microfluidic design and configuration for the manipulation of ionic species in solution including, but not limited to: analyte enrichment, analyte sorting, water desalination and extraction of rare elements from brines.
- Couples ion separation (desalination) and ion storage (potential energy) in a synergistic manner.
Ion exchange is a critical stage in water purification. Many industries such as semiconductors, pharmaceuticals, and food processing require deionized water for manufacturing and processing. These are multi-billion dollar market segments, each with sustainable growth rates.