Chemical Decomposition of Flexible Polyurethane Foam to Generate a Media for Microbial Upcycling
Date of Award
Open Access Master's Thesis
Master of Science in Chemical Engineering (MS)
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Department of Chemical Engineering
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Polyurethane waste is becoming a global concern as a large amount is being disposed of in landfills every year, and only a fraction is being recycled. Several polyurethane recycling techniques exist, of which ammonolysis and base-catalyzed hydrolysis is the least explored. Flexible polyurethane foam (FPUF) decomposition can generate amines that can act as a carbon source for the growth of microbial consortia. This study aims to generate a novel media capable of microbial upcycling via ammonolysis and base-catalyzed hydrolysis of flexible polyurethane foams (FPUFs) using ammonium hydroxide and subsequently determine the reaction conditions for maximum solubilization of polyurethane foam in ammonium hydroxide.
Flexible polyurethane foam (FPUF) samples were decomposed using 16% NH4OH at 6.25%, 10%, 15%, 20%, 25%, and 30% weight percent solids loading for a temperature range of 140°C-200°C with 20°C intervals. Residence times of 30 minutes and 60 minutes were tested. The effectiveness of the decomposition process was determined based on the solubilization of flexible polyurethane foam (FPUF) in ammonium hydroxide. The solid and liquid products were analyzed using FTIR and NMR spectroscopy, respectively, to determine the decomposed products. 2,4-toluenediamine (TDA) was identified as the carbon source in the liquid from the NMR spectra of the liquid product. Aditionally, microbial growth was studied in a media prepared using the liquid product and a minimal media.
This work successfully achieved 95% solubilization of flexible polyurethane foam (FPUF) in NH4OH. 2,4-toluenediamine (TDA), the major chemical used to make 2,4-toluene diisocyanate, which is used in the manufacture of polyurethanes, was identified as a product. Two microbial species - Brevudimonas diminuta and Chelatococcus daeguensis – were comparatively enriched when consortia were grown in media containing pure TDA or FPUF liquid. However, an initial increase in microbial growth in the PUF and TDA media within the first 24 hours was quickly followed by a reduction in OD600, indicating either rapid depletion of the carbon source or generation of a toxic by-product. Future work will attempt to isolate the organisms that may be responsible for TDA metabolism and develop a method to quantify the amount of TDA in the liquid product.
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This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Baruah, Kaushik, "Chemical Decomposition of Flexible Polyurethane Foam to Generate a Media for Microbial Upcycling", Open Access Master's Thesis, Michigan Technological University, 2023.
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