Capacitive Deionization for Water Desalination Aubrey McCutchan, Freshman Research Scholar

Department of Civil and Environmental Engineering with Dr. John Veenstra

Abstract Potable water is a resource essential to human activity and is becoming increasingly difficult to attain as human demand for it grows. Additionally, this problem has been increasingly gaining public awareness considering water shortages such as the one occurring in California. My project focused on investigating and improving possible alternative technologies and the future testing of capacitive deionization. The long term goal is to discover if capacitive deionization can be used for widespread cheap and effective water desalination.

Materials Being able to manufacture these units has consisted largely of reading scientific articles. There are different procedures to construct these units and most articles do not go into much detail of the units and mostly only include results. These are the finalized materials and procedures we will use to make the units.

The supporting parts of the units will be constructed together in a CEAT laboratory. The carbon electrodes will be made using aluminum containers to make the sheets into rectangles to fit the unit and equipment from the chemistry department.

Materials for supporting parts of the unit:

Materials and procedure for the carbon electrode:

•  Carbon powder, polyvinylidene fluoride, and dimethylacetamide.

Methods Data for the desalination rates will be collected using a conductivity meter to record the difference in salt concentration before and after. Additionally, a bulk solution of a decided concentration will be used as a feed for the device and a pump will move the water. A DC power source will be used to vary electrical input and larger chambers will be used to vary water volume within the units.

Future Variables to Test §  Volume of water

§  Size of reactor

§  MDC utilizing CDI

§  Using solar panels or wind turbines as electricity source

§  Electrical input

§  Series of units

This is an emerging technology that has numerous ways to potentially maximize its output to make it more available for practical use. This has turned into a long term project that has many different routes to accomplish its overall goal of finding an alternative method for water desalination.

Literature Cited

1 Y. Zhao, X.M. Hu, B.H. Jiang, L. Li. Optimization of the operational parameters for desalination with response surface methodology during a capacitive deionization process. Desalination, 336 (2014), pp. 66. 2 Youpeng Qu, Yujie Feng, Jia Liu, Weihua He, Xinxin Shi, Qiao Yang, Jiangwei Lv, Bruce E. Logan. Salt removal using multiple microbial desalination cells under continuous flow conditions. Desalination, 317 (2013), pp. 18. 3 Preparation of activated carbon sheet electrode assisted electrosorption process. Journal of the Taiwan Institute of Chemical Engineers 43 (2012), pp. 474.

Acknowledgments I would like to give a special thanks to Dr. John Veenstra for all of the effort and time he has spent helping me develop this project. I would also like to thank Tim O’Neil for all of his help throughout my time in the program. Additional thanks to Dr. Nicholas Materer, Dr. Gregory Wilber, and David Porter.

Potential Uses There are various ways to use this technology if it can be developed. Besides its potential to reduce the salt concentration in water from hydraulic fracturing, it could also be used in third world countries as a cheap way to produce potable water there or even in Oklahoma. Capacitive desalination units have the ability to be a very mobile technology due to their size. This is significant considering traditional methods such as reverse osmosis are far more complicated and require more parts. Furthermore, if they could be used in countries without electricity it is possible that either solar panels or wind turbines could be used to run the units.

Introduction In Oklahoma many water sources contain too high of a salinity content to to be used for crops or drinking water. Additionally water from hydraulic fracturing can contain over 100,000 mg/L of salt, a major pollutant. Initial research pointed to microbial desalination cells being a potential candidate for an effective desalination technique. This technology uses bacteria to oxidize pollutants by freeing electrons to make a positive and negative side of the unit, separating salt ions from the water as shown: Furthermore, recently published articles indicate an even greater technology that simply utilizes carbon electrodes to desalinate. This process known as capacitive deionization is more straightforward and uses an electrical double layer resulting from electricity being sent throughout the electrode. The turnover time is much quicker compared to microbial desalination cells.