eNews November 2018

NMT Hydrology Student Studying Leaching at Old Uranium Mine Sites

by Thomas Guengerich, NM Tech Office of Communication and Marketing

SOCORRO, N.M. – New Mexico Tech doctoral student Alexandra Pearce is using an NM WRRI grant this year to study the potential for revamped uranium mining in northwest New Mexico.

The New Mexico Water Resources Research Institute, located at New Mexico State University, funded Pearce with a $6,000 grant. She is gathering and examining samples collected from deposits in the Grants Uranium District, which stretches from east of Laguna to west of Gallup. The district, though dormant since 2002, remains seventh in the world in uranium production. It supplied over a third of the United States’ uranium over 50 years, generating $4.7 billion in revenue.

“This grant has been an immense help because it should tide me over to cover all the analyses I have to do,” she said. “The NM WRRI funding covers a big part of the electron microprobe, leaching tests, and sundry other tests. This grant was a God-send. I am really grateful because I was wondering how I was going to fund this project.”

Pearce had previously received competitive scholarships and grants from N.M. EPSCoR, the N.M.  Geological Society, and SRK Consulting.

Pearce is combining in-depth mineralogical and geochemical characterizations with results from batch leaching tests to better understand the fundamental controls on metal leaching.

“There’s a lot of uranium remaining in New Mexico and it’s a multimillion dollar industry,” Pearce said. “In situ recovery is the best option for mining because there are no pits or tailings. If you have a good understanding of the hydrology, you can keep it pretty controlled. In situ recovery is the predominant method of uranium mining and it could be great for the state of New Mexico.”

Pearce has collected some samples from the Saint Anthony mine in Laguna, which is in the process of remediation. The majority of her samples are from cores drilled in the 1970s and 1980s, held by the N.M. Bureau of Geology’s core archives in Socorro.

She is characterizing her samples using thin-section petrography, electron microprobe analysis, infrared spectroscopy, and bulk geochemistry analyses.

So far, her work has shown that samples higher in organic matter release far less of their total uranium than those lower in organic matter. The next step in her research is to determine how to increase uranium yield from these high organic matter deposits.

A native of South Africa, Pearce earned two bachelor’s degrees from Penn State University in geobiology and geosciences with a hydrogeology option. She earned her master’s degree from St. Louis University in geoscience. She expects to graduate in May 2020.

eNews November 2018

NMSU Student Studying Membrane Distillation with Photocatalysis for Use in Alternative and Brackish Water Restoration

by Catherine Ortega Klett, NM WRRI Program Manager

Lin Chen is a graduate student in the NMSU Department of Civil Engineering, and he is working on his PhD in environmental engineering. He is also
a recipient of a 2018 NM WRRI Student Water Research Grant entitled, “Water Reuse and Desalination with Self-cleaning Photocatalytic Membrane Distillation.”

As an arid region in the United States, New Mexico faces a significant challenge in water resources management due to increasing fresh water demand, economic growth, and chronic droughts. A potential solution to address the water challenge is to develop a highly functional desalination technology, driven by renewable energy, to treat alternative waters (e.g., wastewater, brackish water, etc.). Membrane distillation (MD) is an emerging thermal-driven membrane separation process that utilizes low-grade heat (e.g., solar thermal) for vapor transport. Photocatalysis is another attractive emerging technology that uses solar irradiation to decompose organic pollutants and inactivate microbes. By integrating photocatalysis with MD (PMD), the hybrid membrane can fully utilize solar irradiation to stimulate photocatalytic degradation of organic contaminants in wastewater as well as to heat the feed solution for the MD process. Lin and his faculty advisor Dr. Pei Xu, Associate Professor of the Civil Engineering Department at NMSU, are working together on the development and analysis of high performance PMD membranes.

The overarching goal of the study is to develop a multi-functional self-cleaning PMD system driven by solar energy to deliver potable-quality water and enhance desalination performance. The specific tasks underway include: (1) Development of high-performance membranes, based on their previous work on photocatalysis and superhydrophobic coatings. To this end, silica and TiO2 nanoparticles are being layered onto a ceramic underlying membrane surface. (2) Evaluation of PMD system performance on a bench-scale with synthesized flat-sheet membranes to treat synthetic and real wastewater under solar light irradiation to evaluate system performance. The water quality of feed and product water, and membrane fouling potential are being studied and characterized.

The project may ultimately lead to the development of alternative water supplies in a low-cost, energy-neutral, and environmentally sustainable manner. The novel membrane photoreactor can potentially make the hybrid photocatalysis and membrane distillation a critical technology for integrated water resources management. It could have important applications such as providing safe drinking water for populations living in remote areas, and it may also provide an economically viable means to carry out such important tasks as water reuse, the desalination of brackish water and seawater, and the onsite treatment of oil and natural gas wastewater.

Lin is expecting to graduate with a doctoral degree in environmental engineering in May 2020. He is from China and received undergraduate and master’s degrees from Nanjing Forestry University in Jiangsu Province, China. Lin said recently, “I am lucky to be involved in the project, and I got help from others such as my classmates. I learned a lot from communicating with them on experiment methods, arrangement of study, etc.” He indicated the NM WRRI student grant has been of great assistance, and he presented a poster on his project at the institute’s October annual water conference. Lin Chen says his career goal is to become a professor like his advisor, Dr. Pei Xu.