The US Marines must obtain and store enough drinking water to last them during missions without access to clean water. Chris Arges, associate professor of chemical engineering at Penn State, and his team are working on a portable, lightweight, and easy-to-use purification method. He and Christopher Gorski, an associate professor of civil and environmental engineering at Penn State, will use a $570,000, three-year grant from the Office of Naval Research to improve membrane capacitive deionization (MCDI) as a way to clean water.
Although the majority of the world’s desalination takes place in centralized production facilities using the reverse osmosis process, this method is unsuitable for military teams because it necessitates high-pressure piping and equipment and is challenging to use in the field, according to Arges. membrane capacitive deionization, on the other hand, is efficient, portable, and effective.
Membrane capacitive deionization uses porous electrodes and ion-exchange membranes to separate ions like sodium and chloride from water when it is powered by battery or solar energy. The method, in Arges’ opinion, works well for brackish or groundwater but falls short when it comes to more concentrated sources of water, like seawater.
The principle of electrosorption describes how electricity causes sodium ions to move across the cation exchange membrane to a negatively charged electrode and chloride ions to move across the anion exchange membrane to a positively charged electrode. “Deionized water is safe to drink because the ions have been taken out of it.”
The electrodes in the membrane capacitive deionization unit become saturated with salt as more and more water is processed through it, making them less effective at removing salt from the water. The electrodes can then be recovered, according to Arges, by altering the cell’s polarity and slowing the water flow.
“This process step wastes some of the water, but it also generates electrical energy that can be recovered and used to reduce the overall energy burden in the subsequent desalination cycle,” Arges said. This keeps MDCI as an energy-efficient company.
Arges and his team will redesign the electrochemical cell module used in membrane capacitive deionization (MCDI) in order to increase the effectiveness of the device on more concentrated water sources. The researchers will create microscopic wells on the surface of the membrane using equipment from the Nanofabrication Lab of the Penn State Materials Research Institute. By making the area between the membrane and electrodes bigger, this makes the contact better and makes it shorter for sodium and chloride ions to cross the membrane-electrode interface.
The electrode material can store more sodium and chloride ions thanks to the wells as well. As a result, users can purify water for longer periods of time before needing to use regeneration. Arges says that if the improved membrane capacitive deionization (MCDI) unit works, it might be able to clean seawater as well as ground water and brackish water.
In the past, Arges and his team were able to make oxygen and hydrogen in an electrolysis cell by separating hydronium and hydroxide ions from water in bipolar membranes. This was done by making patterns on the membranes that were similar to these.
Arges says, “We think that the increased interfacial area will lower ionic transport resistance, which will lead to cleaner water in larger amounts, because the proposed method for this grant has worked for us in the past.”
