Thesis
Peeling a better future : development of microporous activated carbons derived from citrus waste for carbon dioxide capture
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T18126
- Person Identifier (Local)
- 202255898
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- As worldwide reliance on fossil fuels refuses to subside, the importance of developing Carbon Capture and Storage (CCS) technologies grows. Within this field, there is a growing interest in reusable solid adsorbent materials that can be derived from sustainable sources. This study investigates the production of microporous nitrogen-doped biochars and hydrochars from surplus citrus peels, contributing to a circular economy through valorisation of waste streams, for use in carbon dioxide (CO₂) capture systems. A robust Design of Experiments process was carried out for both biochar and hydrochar synthesis routes to identify influential process parameters, and statistical optimisation models were produced, after being informed by material characterisation results. These models aimed to optimise the porosity and elemental characteristics of the materials to enhance their applicability to carbon capture technologies. The samples with the highest response metrics, from both synthesis routes, were then tested for their CO₂ adsorption performance and regenerative ability, under conditions analogous to industrial flue gas. Nitrogen doping, through inclusion of urea in the synthesis process, was found to successfully increase nitrogen content within carbonaceous chars, and activation of the chars using CO₂ was found to develop highly microporous materials. The highest performing sample in terms of CO₂ adsorption, BC Control Mandarin, exhibited CO₂ capacities of 0.61 mmol/g (0.1 bar) and 0.78 mmol/g (0.2 bar), at 60 °C. Meanwhile, the most effective nitrogen-doped char was found to be an optimised material, OPB Micropore Orange, with CO₂ capacities of 0.48 mmol/g (0.1 bar) and 0.70 mmol/g (0.2 bar), at 60 °C. Microporosity, particularly ultramicroporosity, of the materials was found to be key to adsorption at low pressure (< 1 bar), while overall pore volume determined adsorption capacity at higher pressure (5 – 19.5 bar). Meanwhile, increasing the nitrogen content of the samples was not seen to increase CO₂ adsorption in any meaningful way, contrasting with literature findings. All samples tested for their cyclic adsorption characteristics showed minimal loss in capacity, indicating high levels of regenerative ability. This study has provided a detailed and extensive comparison between two synthesis routes for carbonaceous char sorbents, using two similar but distinct biological waste peel feedstocks of orange and mandarin, which both descend from the Rutaceae family. Through elemental and textural characterisation, it aims to provide an overview and assessment of the advantages and disadvantages of both char synthesis methods, and reaffirms the ability of CO₂ to be used as an activating agent to promote micropore formation. By considering the properties and adsorption performance of the carbonaceous char materials, it has been established that Rutaceae peel-derived chars are sustainable and viable solid adsorbents for post-combustion carbon capture applications. The Design of Experiment work in this study also provides a base level to progress from for further process optimisation of chars produced from such feedstocks.
- Advisor / supervisor
- Fletcher, Ashleigh
- Craig, Gavin
- Resource Type
- DOI
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PDF of thesis T18126 | 2026-09-08 | Public | Download |