Comparative Study of Experimental and Modeled Hydrochar Surface Properties

Moran, Max

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Comparative Study of Experimental and Modeled Hydrochar Surface Properties

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According to the United Nations, approximately 931 million tons of food waste were generated globally in 2019 [1]. This large amount of wastes contributes to various societal and environmental problems, including greenhouse gas emissions and other forms of pollution [2, 3]. One approach to addressing negative impacts of food waste is water valorization, a process of converting waste materials into more useful products, such as useful chemicals and materials. Hydrothermal carbonization (HTC) is a valorization process, where wet biomass is converted through a chemical process under elevated temperatures and pressures into a solid hydrothermal char. These chars can be used for a variety of applications, including water purification, gas storage, and soil amendments. One challenge with developing chars for certain applications is that the structure of chars, especially more complex chars from nitrogen bearing waste streams, is not well defined. In this research study, various hydrochars was investigated through different experimental methods in order to develop an understanding of structural properties. The two main methods for gaining structural insight were NMR spectroscopy and Boehm titration. A model structure was created from NMR data by collaborators at Brandeis University and was compared to previous proposed structures from literature. Boehm titrations were carried out in order to gain further experimental insight into the structure/surface properties of the char. The data from these methods were compared to examine whether the methods resulted in agreement on surface site properties. The NMR and titration surface data were also used with a mathematical model to see whether the macroscopic properties of a char, e.g. zeta potential, can be predicted from surface data. The results showed that the NMR and titration data agreed, further validating the proposed NMR model. Also, both the NMR and Boehm titration data were able to create model data fits to certain experimental zeta potential curve characteristics.

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