eNews July 2019

NMSU Graduate Student Synthesizing Highly Porous Monoliths to Adsorb Chromium Ions from Groundwater

By Catherine Ortega Klett, NM WRRI Senior Program Manager

Last year, Zahra Abbasian, a graduate student in the NMSU Department of Chemical and Material Engineering, received an NM WRRI Student Water Research Grant entitled: Recyclable Monolithic Aerogels as Efficient Adsorbents for Chromium VI Removal from Rural Ground-Water Resources. The award was funded through the Bureau of Reclamation-NMSU Cooperative Agreement, Center for the Development and Use of Alternative Water Supplies. Zahra is working under the guidance of her faculty advisor Dr. Reza Foudazi, Associate Professor of Chemical and Material Engineering at NMSU. She presented her student grant research in Las Cruces at NM WRRI’s 63rd Annual New Mexico Water Conference in October 2018 and commented, “Attending the conference gave me a great opportunity to interact with local water experts in person.” She added that she has become more connected with relevant academic research being conducted in the area and has been able to share research challenges and ways to tackle her research project.

In July 2017, the Los Alamos National Laboratory detected chromium, Cr, in their sole source regional groundwater aquifer at a level that was five times the amount designated as safe according to the groundwater standards for New Mexico. This was due to the presence of the highest oxidation state of chromium ions, Cr(VI), which is a highly toxic carcinogen.

The most common conventional method for removal of Cr(VI) is to lower the oxidation state and use lime to precipitate out the chromium as insoluble chromium hydroxide. This approach is not very cost effective because it produces a large amount of sludge. Other approaches are based on the adsorption of Cr(VI) by a variety of natural and synthetic materials such as activated carbon, biological materials, porous minerals such as zeolites, and industrial wastes. The focus of Zahra’s research is the synthesis of a porous monolith by using polymerized high internal phase emulsions, polyHIPEs, containing polypyrrole. The result is a nanocomposite porous monolith that is an efficient and recyclable adsorber of Cr(VI). In addition to common synthetic polymers, chitosan will also be used. Chitosan is obtained from chitin, which is the natural structural chemical used to build exoskeletons in crustaceans like shrimp, crabs, and lobsters. It is easily made by treating chitin with an alkaline substance like sodium hydroxide (lye); the result is an inexpensive water-soluble polymer. Polypyrrole is a key component in Cr(VI) removal. In her experimental method, Zahra oxidizes pyrrole in solution with chitosan or polyHIPEs in the presence of a dye, methyl orange, which promotes the formation of nanotubes in the resulting porous monolith.

Results to date suggest these porous monoliths act as a high capacity adsorber of Cr(VI). Furthermore, they are synthesized out of relatively eco-friendly and inexpensive materials. Compared to other existing adsorbents, it also has the advantages of being recyclable, and its production generates a relatively small amount of waste material. It is anticipated that this approach to Cr(VI) removal will have a beneficial impact on the general problem of providing safe drinking water by the removal of metal ion contaminants.

Zahra expects to complete her studies and graduate from NMSU with a PhD in chemical engineering in August of 2021. She received her BS degree (2005) from Shiraz University, and her MS degree (2009) from Iran University of Science & Technology (IUST), both located in her home country of Iran. Given the growing demand for drinking water worldwide, and the concomitant growth in the production of industrial wastes, Zahra hopes to make a significant contribution, in academia or industry, in the disciplines of water quality and wastewater treatment.