Perchlorate ion is highly mobile natural waters and is difficult to treat. Due to its similar molecular size, it blocks the uptake of iodine by the thyroid gland and can disrupt the ability to produce hormones needed for normal growth, metabolism and development, and, is considered an endocrine disrupter, especially dangerous to children and pregnant women. This GOALI proposal will establish an important collaboration between the PI's group at UC Santa Cruz and Aerojet Rocketdyne. The project will examine a new approach to treating perchlorate contaminated waters and result in a more effective, economical perchlorate remediation than the current single-use processes.
The PI has discovered SLUG-n cationic materials that can exchange nitrate for perchlorate over indefinite cycles. This important advance could lead to the replacement of the single-use ion exchange resins currently used at Aerojet Rocketdyne. The groundwater plume at the Aerojet Rocketdyne site has perchlorate at levels up to 6,000 ppb. The Maximum Contaminant Level (MCL) for perchlorate in California is 4 ppb while the EPA mandates a nitrate MCL of 10 ppm. Release of nitrate is therefore acceptable at 6 ppm. However, a recent breakthrough in the PIs laboratory has been to replace nitrate by acetate, which is environmentally benign. The anions are easily swapped by placing the solid into a solution containing the incoming anion. The process is far more selective, rapid and higher capacity than the extensively studied ion exchange resins layered and double hydroxides. The SLUG-n solids can be reused indefinitely (seven cycles performed as proof-of-concept). The research will focus on several aims: (i) investigation of the anion exchange chemistry: characterization and optimization of the exchange capacity, kinetics and cycling lifetime for the current materials. Competing anions such as sulfate, nitrate and carbonate will be introduced way above the levels typical of the contaminated groundwater to verify the selectivity for perchlorate; (ii) pilot testing at the company?s Groundwater Extraction and Treatment facilities: the most promising perchlorate exchangers will be studied at Aerojet Rocketdynes treatment facility side streams. Both batch and column testing will be conducted in parallel and monitored daily by field specialists. Flow columns will be packed with material and scaling up of the synthesis will be straightforward since the host materials can be synthesized with 99% yield at room temperature; (iii) design of improved anion exchangers: the templating anion, organic linkers and metal building block of the host materials will be varied for isolating structures with improved exchange properties, reduced cost, lower toxicity of the outgoing anion and possible targeting of other anionic pollutants. Aerojet Rocketdyne is interested in partnering with UC Santa Cruz to advance innovative technologies that will improve the ability to capture and treat perchlorate in contaminated groundwater. The company will provide practical experience to students whose career paths will inherit and make significant advance towards a long-term treatment goal. The Groundwater Extraction and Treatment facilities under high security at the Aerojet Rocketdyne Sacramento site will provide a side stream and daily test monitoring of these promising new materials. Aerojet Rocketdyne has the expertise and infrastructure to help guide the research and aid in commercialization when this three-year GOALI study demonstrates the potential of commercial viability. The development of new materials for treatment of oxyanion including chromate and arsenate, in addition to perchlorate, is an important step in achieving remediation and water treatment goals more effectively and at lower cost.