Alamro, Mohammed
(2025)
Development and performance evaluation of alkali-intercalated nano-porous carbons materials from waste plastics for CO2 capture applications.
PhD thesis, University of Nottingham.
Abstract
The global imperative to mitigate greenhouse gas emissions and address climate change necessitates the development of advanced carbon capture technologies. This PhD research explores the valorisation of polymeric waste materials—including polyurethane (PU), polyisocyanurate (PIR), phenolic resin (PR), and mixed foams—into high-performance activated carbons (ACs) for post-combustion CO2 capture. Using sustainable carbonization-activation methods with KOH and K2CO3 as activating agents, the study demonstrates the potential of these waste-derived materials as cost-effective, efficient, and scalable adsorbents under industrially relevant flue gas conditions.
Comprehensive investigations revealed that the activation conditions, including temperature and activating agent ratios, are critical determinants of the textural properties, surface chemistry, and microporosity of the synthesized carbons. PU-derived carbons exhibited ultra-microporous structures (<1 nm) and potassium-enriched surface chemistry, achieving exceptional CO2 adsorption capacities of up to 2.22 mmol/g at 25°C and 15 kPa. PIR-derived carbons, enhanced with nitrogen and potassium species, demonstrated comparable performance, with adsorption capacities reaching 2.10 mmol/g. These materials benefited from their unique combination of high microporosity and enriched basic sites, which facilitated strong interactions with CO2 molecules. PR-derived carbons,
though slightly less efficient, exhibited high stability over multiple adsorption-desorption cycles, underscoring the role of controlled pore size distribution and surface functionalization. Mixed foam-derived carbons, while exhibiting reduced adsorption capacities (1.66 mmol/g at 25°C and 15 kPa), highlighted the potential for optimization by refining activation conditions to overcome their inherent compositional heterogeneity.
Advanced characterization techniques, including Brunauer–Emmett–Teller (BET) analysis, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), provided detailed insights into the physical, chemical, and structural properties of the adsorbents. The results established a strong correlation between ultra-microporosity and CO2 adsorption capacity at low partial pressures, particularly for pore sizes ranging from 0.36 to 0.43 nm. Furthermore, the presence of extra-framework cations, such as potassium, was found to play a pivotal role in enhancing CO2 adsorption through electrostatic and chemical interactions, contributing to more than 50% of the total uptake in some samples. These findings emphasize the interplay between pore structure and surface chemistry in determining the overall performance of the adsorbents.
The research not only highlights the potential of foam-derived carbons for industrial CO2 capture but also identifies key challenges. The scalability of the synthesis process, particularly for mixed foams, and the environmental and economic implications of activating agents like KOH and K2CO3 remain critical areas for future exploration. Additionally, optimizing the activation conditions to maximize ultra-microporosity while maintaining structural stability and surface functionality will be essential for advancing these materials to commercial applications.
By transforming polymeric waste into high-value adsorbents, this study contributes significantly to the dual objectives of mitigating climate change and addressing global plastic pollution. The findings provide a foundation for future research in sustainable carbon capture technologies, offering practical solutions that align with global efforts to achieve net-zero emissions. This research demonstrates that waste-derived carbons can serve as a bridge between environmental sustainability and technological innovation, paving the way for their adoption in industrial-scale CO2 capture and beyond.
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