MSE Masters Thesis Presentation: Jiadong Gu

MSE Master’s Final Thesis Presentation: Jiadong Gu

TITLE: Investigating Mass Transport in Temperature Responsive Amine-Infused Hydrogels for Carbon Capture

ADVISOR: Chuanhua Duan (ME, MSE)

COMMITTEE: Joerg Werner (ME, MSE, Chemistry)

ABSTRACT: This master's thesis investigates how structural design influences carbon dioxide transport and adsorption-desorption behavior in temperature-responsive amine-infused hydrogels, with particular emphasis on the difference between plain hydrogels and hydrogels featuring microporous structures. The core argument of this work is that the performance of hydrogel sorbents cannot be evaluated solely by equilibrium uptake. In these materials, internal transport pathways, diffusion processes, and chemical reactions play critical roles in determining how rapidly CO2 reaches active sites, how effectively the material is utilized, and how it can be regenerated. This study combines staged COMSOL modeling with a transport-centered comparison between planar and microporous structures. One-dimensional planar reaction-diffusion models first establish the baseline signatures of one-sided CO2 penetration, moving reaction fronts, and species redistribution in unstructured hydrogels. The simulation was then extended to a microporous hydrogel structure to compare CO2 distribution, penetration depth, and transport under different conditions. Microchannel coated with hydrogel on the inner wall was used as a simplified but representative structure for this study. The simulation results show that planar hydrogels are front-limited, whereas the structured hydrogels redistribute access in space: at an equivalent characteristic transport length of 300 μm under the same inlet-outlet pressure, to reach 95% diffusion-reaction completion, the 2D microchannel coated with a 200μm-thick-hydrogel and having a1000 μm outer diameter requires approximately 481s, whereas the 1D planar uniform representative requires about 6750 s, corresponding to an approximately 14 times difference. Experimentally, a crosslinked PNIPAm-co-DMAEMA-co-NTBA thermoresponsive hydrogel, with NIPAm:DMAEMA:NTBA = 70:10:20 wt%, MBAA as the crosslinker, and APS with TEMED as the initiator, was prepared as the material platform. Experiments were performed under 400 ppm CO2 with regeneration at 80 °C through a lab-built DGS system, on structures matched to the simulation dimensions plain cylinder and microchannels coated with a 200-μm-thick hydrogel, both with a 1000-μm outer diameter. Compared with plain hydrogels, microchannel hydrogels exhibited a 6-17% improvement in CO2 capture performance, qualitatively consistent with the transport enhancement suggested by the simulations. Overall, the introduction of micrchannels reduces transport paths, improves gas accessibility, and enhances sorbent performance. Through this combined simulation and experimental study, this thesis establishes a connection between structural design and macroscopic adsorption-desorption performance, providing insights for the design of temperature-responsive amine-infused hydrogel for enhanced direct carbon capture.