Matthew J. Realff

Hollow fiber sorbents containing amine-infused mesoporous silicas are promising materials for CO2 capture from ambient air due to their ease of heat integration and low pressure drops. This advanced sorbent design permits a wide range of heat source integration options, though limited experimental insights are found in the literature. In this study, hot water is utilized as the heat source for regenerating poly(sulfone)-silica-poly(ethyleneimine) fibers prepared with a hybrid poly(vinylidene chloride)/styrene-butadiene lumen barrier. Fiber sorbents with this novel polymer and lumen formulation are characterized and tested using breakthrough and desorption measurements to evaluate the optimal adsorption and desorption times. Rapid temperature swing adsorption cycles are completed to evaluate the stability, productivity, and swing capacities of the fiber sorbents. In the final cycle, a swing capacity of 0.72 mmol gfiber-1 under 400 ppm CO2 flow at 22 °C and 45% relative humidity was reached, with a CO2 recovery of 68%.

This perspective explores emerging methodological challenges in applying life cycle assessment to low-carbon technologies in a policy-driven decarbonization landscape.

Direct air capture (DAC) of CO₂ is a critical technology to combat climate change, offering a scalable approach to mitigate atmospheric CO₂ accumulation. Despite advancements in adsorbent materials, the performance of DAC systems remains highly sensitive to environmental conditions, such as temperature and humidity. Poly­(ethylenimine) (PEI)-functionalized silica has emerged as a promising sorbent due to its high CO₂ capacity and tunable properties. However, optimizing its performance across diverse climatic conditions requires a deeper understanding of how the PEI loading impacts the adsorption capacity and kinetics under varying temperatures and humidities. This study reports the CO₂ and H₂O adsorption kinetics and capacities, desorption behavior, and speciation of adsorbed CO₂ using silica/PEI adsorbents supported within expanded poly­(tetrafluoroethylene) (ePTFE) sheets across a wide range of temperatures and humidities, representing the diversity of climates found across the United States. With the obtained data, guidelines for selecting and optimizing PEI-loaded silica-based sorbents for DAC applications are developed. These findings provide a framework for tailoring sorbents to specific climatic scenarios, ensuring a reliable and efficient DAC performance.

Hollow fiber sorbents containing amine-infused mesoporous silicas are promising materials for CO2 capture from ambient air due to the ease of heat integration and low pressure drops. In this study, hot water is utilized as the heat source for regenerating polysulfone-silica-poly(ethyleneimine) fibers prepared with a hybrid polyvinylidene chloride/styrene-butadiene lumen barrier. The fiber sorbents are characterized using breakthrough and desorption measurements to evaluate the optimal adsorption and desorption times. Rapid temperature swing adsorption cycles are completed to evaluate the stability, productivity, and swing capacities of the fiber sorbents. In the final cycle, a swing capacity of 0.72 mmol gfiber-1 under 400 ppm CO2 flow at 22 °C and 45% relative humidity was reached, with a CO2 recovery of 68%.

Plastics offer significant benefits but pose growing environmental and health concerns due to low recycling rates and continued reliance on fossil-derived feedstocks. While plastics circularity has emerged as a key strategy to reduce plastic waste and impacts, current mechanical recycling pathways face major limitations in maintaining material quality over repeated cycles. Advanced methods like chemical recycling and dissolution show promise but raise questions about environmental impacts, scalability, and cost. In this perspective, we introduce the concept of spirality as a more realistic model than perfect circularity, acknowledging the inevitable degradation of plastic quality over consecutive recycling cycles and the need for tiered recycling strategies. We emphasize the importance of early stage integration of mechanical property benchmarking, life cycle assessment (LCA), and techno-economic analysis (TEA) to evaluate emerging chemistry-enabled solutions for plastics recycling. In parallel, we underscore the critical role of high-quality data, and the need for multidisciplinary collaboration to align chemistry, materials science, engineering, systems analyses, and policy for sustainable transitions. Spirality, combined with robust assessment frameworks, can guide innovation toward more pragmatic and sustainable solutions in polymer design and end-of-life management.

Pervaporation, combined with other separation processes, can effectively remove water from fermentation product streams, making it highly suitable for purifying alcohols like 2,3-butanediol (BDO). In this study, a dense poly-(vinylidene fluoride) (PVDF) hollow fiber membrane module prototype was fabricated for BDO dehydration, achieving >0.2 LMH total flux and >95% BDO rejection. With a Markov chain Monte Carlo (MCMC) approach, Bayesian inference was used to quantify the uncertainty of the permeance parameters. A membrane cascade model was developed to scale up a process that purifies a preconcentrated BDO feed (70 wt %) to high purity (90 wt %). Through propagation of the uncertainty of the parameters and sensitivity analyses of the process variables, a cascade design was recommended. Despite data and model limitations, the framework enabled a reliable system analysis and economic evaluation, validated through tight confidence intervals in key process metrics, establishing the foundation for future applications of Bayesian methods in membrane-based processes.

Molecular simulations, experiments, and techno-economic analysis propose cost-efficient direct air capture at near-cryogenic temperatures via LNG regasification integration.