Ion Concentration Polarization - Electrocoagulation Hybrid System for Water Treatment

Technology

The ICP-EC device uses two similar ion-exchange membranes under an applied electric field to create an ion depletion zone and an ion enrichment zone within each channel. For example, when using cation exchange membranes (CEMs), cations are selectively transferred through the CEMs, causing the relocation of anions in order to achieve electro-neutrality. This results in an ion depletion zone with a reduced concentration of ions—including salt ions and charged agents such as proteins and bacteria—and an ion enrichment zone with an increased concentration of ions. Additionally, the electrolysis of the sacrificial metal anode releases metal ions that act as a coagulants, destabilizing colloidal particles from the feed stream. These particles are repelled in the ICP depletion zone. The channel is bifurcated at the end, allowing the flow with reduced ionic species from the depletion zone to be separated into a purified water stream, while the flow with concentrated ionic species from the enrichment zone is separated into a concentrated stream. This method can also be performed with two anion exchange membranes, by relocating cations, where the locations of the desalted/brine flows are converted. By stacking the unit platforms in parallel, the system can be scaled up for larger flow rates.

Problem Addressed 

The increasing global health threat posed by the pollution of drinking water is driving interest in scalable and inexpensive technologies for water desalination, purification, and monitoring. Many desalination systems require either a very high energy input (e.g., thermal evaporation technologies) or complicated pre-treatment steps to remove potential foulants (e.g., membrane-based technologies). Reverse osmosis (RO), the current leading technology for desalination, is highly sensitive to membrane fouling and requires extensive pre-treatment to remove potential foulants, such as suspended solids or bacteria. Another desalination technology is electrodialysis (ED), which removes salt, but not nonionic particles. In both RO and ED, particle removal needs to be done prior to desalination. By combining ICP and EC, the inventors developed a single electrochemical system that enables simultaneous pre-treatment and desalination, reducing membrane fouling as well as voltage drop and energy consumption. 

Advantages 

• Simultaneous removal of salt ions, colloidal pollutant particles and charged bio-agents 

• Offers flexibility to treat various types of wastewater, such as: 

  • brackish groundwater 

  • household water containing bacteria or other biological contaminants 

  • murky water from various suspended solids and/or industrial heavy metal contaminants 

• Requires lower energy than conventional desalination systems and avoids complex pre-treatment steps 

• Potential for scale-up and high flow rates by stacking the unit system or converting from existing ED platforms 

• Operates without a high-pressure system, making it suitable for small-scale localized water treatment 

• Has demonstrated removal of salt, fluorescent microparticles, silica, and E. coli bacteria