Graduate Thesis Or Dissertation
 

Degradation of N-Nitrosodimethylamine Using Photo-Catalysis and Microreactor Technology : Experimentation and Modeling

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/v692t868x

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  • The cleanliness of water is a major issue with regards to humanity's continued survival. The chlorination and chloro-amination of water is essential to the creation of microbiologically clean water. However these processes also give rise to oxidative byproducts such as nitrosamines. In particular, due to its high toxicity, N-Nitrosodimethylamine (NDMA) is of high concern for many communities. As a consequence, the destruction of small concentration of NDMA from drinking water can be considered a priority. This work investigates the degradation of N-nitrosodimethylamine (NDMA) through experimentation in a microreactor and develops a computational model based on the results. The microreactor developed for this study was a 2 cm in length, 1 cm in width and 200 µm deep microchannel. One of the walls of the microreactor was coated with TiO₂, a semi-conductor photo-catalyst, and activated through the use of lower energy UV-A light. Reactor effluent was characterized using a cationic and anionic ion chromatograph. The results showed superior degradation of NDMA when compared to similar studies which utilized more conventional suspended particle batch reactors, with the microreactor degrading NDMA by approximately 90% in 5 minutes. Measurements of dimethylamine, NO⁺, and methylamine products showed strong correlation to NDMA consumption. Methanol could not be detected using the analytical tool employed and its existence could not be confirmed. Results of the microreactor modeling in COMSOL Multiphysics showed good trend correspondence. The model fit the degradation mechanics of NDMA well but differences between the modelling results and experimental results can be attributed to a shift from a reaction limited reactor to a diffusion limited reactor. The model did not fit the experimental data for methylamine, the experimental data insinuates another reaction consuming methylamine. Based on the modeling results a thinner microchannel would be important for optimal degradation in a microreactor.
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