Nitrite, a common drinking water contaminant, is regulated to a maximum contaminant level of 1 mg/L by the EPA. Removal of nitrite contamination of drinking water currently requires energy intensive physical separation techniques including ion exchange and reverse osmosis. These techniques generate a concentrated brine which requires further disposal. Alternative methods, such as catalytic hydrogenation, may reduce energy costs for nitrite treatment and prevent formation of waste brine. Current hydrogenation technology relies on noble metal catalysts, which are expensive and rare. Significant improvement to the economic outlook of this technique can be realized by development of earth abundant catalysts with catalytic activity towards nitrite hydrogenation. MoS2, a well-known hydrodesulfurization catalyst in the bulk phase, shows significant activity for the hydrogen evolution reaction at crystalline edge sites when nanostructured. As hydrogen activation is the key step in nitrite hydrogenation, MoS2 is a good candidate for earth abundant nitrite hydrogenation catalysis. This study investigates the application of nanostructured MoS2 for the hydrogenation of nitrite in aqueous solution. Nanostructured MoS2 was synthesized by novel hydrothermal technique and coated with a carbon shell for improved aqueous stability. TEM analysis shows high density of MoS2 nanosheets with crystalline edge sites. Activity of the synthesized catalyst was evaluated in a semi-batch hydrogenation reactor at atmospheric conditions through kinetic studies of nitrite removal. Ammonia concentrations were analyzed throughout the reaction period to determine by-product selectivity (N2 vs NH3). Preliminary results indicate that nanostructured MoS2 effectively reduces nitrite with comparable activity to conventional nitrite hydrogenation catalyst 5%Pd/Al2O3, while commercial bulk MoS2 is inactive for nitrite hydrogenation. This study shows that catalyst nanostructure is crucial to the activity of MoS2 for nitrite hydrogenation and that MoS2 is a candidate earth-abundant catalyst for nitrite removal from drinking water.

Investigation of nanostructured MoS2 as an earth abundant catalyst for nitrite hydrogenation

255th National Meeting (2018)

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