NSF-BSF Application: Selective Electrosorption for Boron Removal and Recovery from Seawater

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Agricultural irrigation is the largest user of water in the United States, accounting for approximately 80 percent of the Nation’s clean water consumption. Seawater desalination is a drought-proof technology that can address growing demands for water in agriculture and other uses. At present, seawater reverse osmosis (SWRO) is the best available commercially available desalination technology. However, the desalinated seawater cannot be used directly in irrigation due to the limited ability to remove boron. This results from limitations on the boron retention capability of commercial SWRO membranes. Boron adversely impacts plant growth and damages apple, citrus, grapes, and other crops when water containing more than 0.3 mg/L of boron is used in irrigation. Thus, commercial SWRO plants must use an additional purification step to reduce boron concentration to acceptable concentrations. This greatly increases the energy consumption and costs of using desalinated water for agriculture. The proposed research will address the inefficiencies associated with boron removal through the development of a novel selective separation technology based on electrosorption. This new technology will be chemical-free, energy efficient, and capable of recovering a high purity boron stream for beneficial uses. Successful completion of this project will advance the development of the next generation of sustainable SWRO plants, with great potential benefit to society. The project will fruther benefit society by providing research training to graduate and undergraduate students at Yale University. Also, the investigator will promote diversity and enhance the involvement of under-represented groups in science and engineering through engagement in Yale's K-12 outreach activities. A critical and unresolved challenge in SWRO desalination is to produce a permeate water stream suitable for irrigation without additional and costly purification to remove plant-toxic elements such as boron. The overall goal of this project is to develop an innovative flow-through electrosorption process for boron removal and recovery in seawater desalination. To achieve this goal, the PI proposes to carry out an integrated experimental and modeling project structured around the following tasks: 1) fabrication of an ultra-selective positive electrode (anode) using boron-chelating resins as building blocks; 2) performance testing of the fabricated electrodes for selective boron removal and recovery; 3) elucidation of the mechanisms underlying selective boron electrosorption; 4) assessment of the impact of electrochemical reactions on the long-term stability and boron selectivity of the electrodes; and 5) evaluation and modeling of the energy consumption and boron selectivity of the combined SWRO-electrosorption process. The proposed work would be the first to study boron-selective removal and recovery from seawater using a chemical-free method. The successful completion of this research has potential to transform desalination through the development of a more energy efficient and sustainable boron removal and recovery process from SWRO plants.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.