Sustainable conversion of strategic industrial wastes and biomass into activated carbons for CO₂ capture: mechanisms, material design, and adsorption performance
Doctoral thesis, 2026
The increasing concentration of atmospheric CO₂ necessitates sustainable sorbent materials for efficient carbon capture . This thesis explores the valorization of carbon-intensive waste streams into porous carbons for CO₂ capture within a circular materials framework. Three structurally distinct precursors were investigated: woody biomass, recovered carbon black from end-of-life tires, and graphite from spent lithium-ion batteries. Potassium-assisted chemical activation served as a unifying synthesis approach to establish structure–property–performance relationships and assess the chosen materials suitability as solid adsorbents.
The effects of precursor structure, activation conditions, and potassium speciation on pore development, carbon framework evolution, and surface chemistry were systematically analyzed. Particular attention was given to adsorption-relevant microporosity and its role in governing CO₂ uptake and CO₂/N₂ selectivity.
The obtained results suggested that activation responsiveness was strongly precursor-dependent. Biomass showed the highest reactivity toward KOH, yielding dense microporous networks with BET surface areas up to 2655 m² g⁻¹ and high CO₂ capacities, although excessive activation caused pore widening and performance loss. Recovered carbon black exhibited limited activation due to its compact morphology, leading to mesopore-dominated structures and lower uptake. Recovered graphite was the most resistant, with porosity developing mainly through defect-driven edge etching while preserving graphitic order.
CO₂ adsorption across all systems was governed by the presence of narrow micropores rather than total surface area, highlighting that the key performance factor was pore size matching to the kinetic diameter of CO₂ as. KOH provided the highest activation efficiency, while alternative potassium salts enabled milder pore development with improved yield. Oxygen-containing surface groups formed as a result of the activation contributed to adsorption energetics but remained secondary to textural effects under physisorption-controlled conditions.
Biomass- and recovered carbon black–derived carbons showed stable cyclic operation and favorable CO₂/N₂ selectivity under dilute and flue-gas-relevant conditions.
Beyond adsorption performance, this work demonstrates scalable routes for converting renewable, industrial, and technological carbon residues into high-value porous materials. The results provide design guidelines for precursor selection, activation strategy, and pore engineering in waste-derived carbons for gas separation and related environmental applications.
The effects of precursor structure, activation conditions, and potassium speciation on pore development, carbon framework evolution, and surface chemistry were systematically analyzed. Particular attention was given to adsorption-relevant microporosity and its role in governing CO₂ uptake and CO₂/N₂ selectivity.
The obtained results suggested that activation responsiveness was strongly precursor-dependent. Biomass showed the highest reactivity toward KOH, yielding dense microporous networks with BET surface areas up to 2655 m² g⁻¹ and high CO₂ capacities, although excessive activation caused pore widening and performance loss. Recovered carbon black exhibited limited activation due to its compact morphology, leading to mesopore-dominated structures and lower uptake. Recovered graphite was the most resistant, with porosity developing mainly through defect-driven edge etching while preserving graphitic order.
CO₂ adsorption across all systems was governed by the presence of narrow micropores rather than total surface area, highlighting that the key performance factor was pore size matching to the kinetic diameter of CO₂ as. KOH provided the highest activation efficiency, while alternative potassium salts enabled milder pore development with improved yield. Oxygen-containing surface groups formed as a result of the activation contributed to adsorption energetics but remained secondary to textural effects under physisorption-controlled conditions.
Biomass- and recovered carbon black–derived carbons showed stable cyclic operation and favorable CO₂/N₂ selectivity under dilute and flue-gas-relevant conditions.
Beyond adsorption performance, this work demonstrates scalable routes for converting renewable, industrial, and technological carbon residues into high-value porous materials. The results provide design guidelines for precursor selection, activation strategy, and pore engineering in waste-derived carbons for gas separation and related environmental applications.
Recovered graphite
Biomass
CO₂ capture
CCU, CCUS.
Recovered carbon black
Potassium activation
Waste valorization
Activated carbon
Author
Bartosz Dziejarski
Chalmers, Space, Earth and Environment, Energy Technology
Tailoring highly surface and microporous activated carbons (ACs) from biomass via KOH, K₂C₂O₄ and KOH/K2C2O4 activation for efficient CO₂ capture and CO2/N2 selectivity: characterization, experimental and molecular simulation insights
Chemical Engineering Journal,;Vol. 524(2025)
Journal article
Upgrading recovered carbon black (rCB) from industrial-scale end-of-life tires (ELTs) pyrolysis to activated carbons: Material characterization and CO<inf>2</inf> capture abilities
Environmental Research,;Vol. 247(2024)
Journal article
Insights into Activation Pathways of Recovered Carbon Black (rCB) from End-of-Life Tires (ELTs) by Potassium-Containing Agents
ACS Omega,;Vol. 9(2024)p. 31814-31831
Journal article
Valorization of hazardous graphite from black mass (NMC 111) of lithium-ion battery recycling via KOH activation for functional carbon design
Materials and Design,;Vol. 254(2025)
Journal article
Carbon dioxide (CO₂) is one of the main greenhouse gases responsible for climate change. Reducing its concentration in the atmosphere is a major global challenge, and one promising solution is carbon capture, where specialized materials trap CO₂ before it is released into the environment. At the same time, large amounts of carbon-rich waste are generated every year from industries, transportation, and consumer products. This thesis combines these two challenges by exploring how waste materials can be transformed into valuable CO₂-capturing materials.
Three different waste sources were investigated: wood-based biomass, recovered carbon black obtained from end-of-life tires, and graphite recovered from spent lithium-ion batteries. Using a chemical treatment based on potassium compounds, these materials were converted into highly porous carbons. The process creates millions of tiny pores within the carbon structure, greatly increasing the surface area available for gas adsorption.
The study showed that the original structure of the waste material strongly influences the final performance. Biomass was the most suitable precursor, producing carbons with exceptionally high surface areas and a large number of very small pores that efficiently captured CO₂. Carbon black from waste tires could also be converted into porous materials, although its dense structure limited pore formation and reduced adsorption capacity. Recovered graphite from batteries was the most resistant to modification and developed only limited porosity while retaining much of its original graphitic structure.
The results revealed that the ability to capture CO₂ depends less on the total surface area and more on the presence of extremely small pores that closely match the size of CO₂ molecules. These pores act like molecular traps, selectively capturing CO₂ while allowing other gases, such as nitrogen, to pass more easily. The materials also maintained their performance over repeated adsorption and regeneration cycles, demonstrating their potential for practical applications.
Beyond carbon capture, this research highlights a sustainable pathway for converting renewable, industrial, and technological waste into high-value functional materials. By turning discarded resources into products that help reduce greenhouse gas emissions, the work supports the principles of the circular economy and contributes to the development of cleaner and more resource-efficient technologies.
Three different waste sources were investigated: wood-based biomass, recovered carbon black obtained from end-of-life tires, and graphite recovered from spent lithium-ion batteries. Using a chemical treatment based on potassium compounds, these materials were converted into highly porous carbons. The process creates millions of tiny pores within the carbon structure, greatly increasing the surface area available for gas adsorption.
The study showed that the original structure of the waste material strongly influences the final performance. Biomass was the most suitable precursor, producing carbons with exceptionally high surface areas and a large number of very small pores that efficiently captured CO₂. Carbon black from waste tires could also be converted into porous materials, although its dense structure limited pore formation and reduced adsorption capacity. Recovered graphite from batteries was the most resistant to modification and developed only limited porosity while retaining much of its original graphitic structure.
The results revealed that the ability to capture CO₂ depends less on the total surface area and more on the presence of extremely small pores that closely match the size of CO₂ molecules. These pores act like molecular traps, selectively capturing CO₂ while allowing other gases, such as nitrogen, to pass more easily. The materials also maintained their performance over repeated adsorption and regeneration cycles, demonstrating their potential for practical applications.
Beyond carbon capture, this research highlights a sustainable pathway for converting renewable, industrial, and technological waste into high-value functional materials. By turning discarded resources into products that help reduce greenhouse gas emissions, the work supports the principles of the circular economy and contributes to the development of cleaner and more resource-efficient technologies.
Subject Categories (SSIF 2025)
Materials Chemistry
Driving Forces
Sustainable development
Areas of Advance
Energy
Materials Science
Roots
Basic sciences
DOI
10.63959/chalmers.dt/5904
ISBN
978-91-8103-447-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5904
Publisher
Chalmers