Development of sustainable and low cost nitrate selective anion exchange polymers from agricultural wastes

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Groundwater is the most important source of freshwater in the world. In the United States, groundwater provides nearly half of the drinking water supply. Nitrate contamination of groundwater is a significant global problem. Consumption of nitrate-contaminated water can cause cancers, neural defects, and thyroid disease. Consequently, the US EPA has set the maximum contaminant level (MCL) for nitrate in drinking water at 10 mg/L nitrate-nitrogen. At present, anion exchange resins are the best commercially available technology for removing nitrate from contaminated groundwater. However, this technology is often too expensive for many public and private systems that rely on groundwater. The goal of this project is to address the need for lower cost materials and technologies for the removal of nitrate from drinking groundwater sources. To achieve this goal, the investigator will synthesize, characterize, and optimize the performance of a new family of low-cost nitrate-selective anion exchange polymers using cellulose extracted from agricultural wastes as building blocks. The successful completion of this project will benefit society through the development of more cost effective and sustainable technologies for nitrate removal to achieve US EPA regulations. Further benefits to society will be achieved through student education and training via the integration of the project findings into undergraduate and graduate course modules on adsorption, groundwater quality, and life cycle assessment. Groundwater contamination by nitrate has become a major problem worldwide. Commercial and selective anion exchange resins used to extract nitrate from contaminated groundwater are expensive. Moreover, their synthesis requires the use of hazardous chemicals including petroleum-derived polymers such as styrene and divinylbenzene. The goal of this research is to develop new and lower cost nitrate-selective anion exchange polymers using cellulose from agricultural wastes. To achieve this goal, the PI will conduct an experimental program structured around four tasks. Task I will investigate the extraction of cellulose from corn cobs and wheat stalks using sodium periodate, a low-cost inorganic salt as oxidant. In Task II, the oxidized functional groups of the extracted cellulose will be converted to amine linkages to enable subsequent polymer crosslinking and functionalization for selective nitrate removal. Functional groups that will be evaluated include quaternary ammonium compounds and tertiary amines with structures and properties optimized for nitrate selectivity. In Task III, batch and column experiments will be conducted to evaluate the nitrate selectivity of the new anion exchange polymers in water matrices containing high concentration of competing sulfate divalent anions. In Task IV, life cycle analysis (LCA) will be carried to assess the environmental impact and sustainability of the new nitrate-selective anion exchange polymers. The successful completion of this research has potential for transformative impact through the development of lower cost and more sustainable anion exchange polymers for the selective removal of nitrate from contaminated drinking groundwater sources.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.