Thesis
Design of experiments optimisation of Scottish wood biochars for water remediation targeting selected persistent organic pollutants
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T16841
- Person Identifier (Local)
- 202061506
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This work focuses on the development of a class of porous materials-biochars for the purpose of water remediation targeting selected persistent organic pollutants. The ease of renewability of the raw material involved and the overall carbon footprint ofthe production process are key factors to be considered. Despite extensive research into biochar production, the synergistic effects between the operating process parameters and their influence on the final biochar characteristics have not always been mapped. As a result, this work focusses on the development of biochars usingnative Scottish wood samples and aims to understand the interplay of process variables on final biochar performance.For investigation, softwood and hardwood samples were procured from a local estate for the purpose of biochar production. Initially, screening experiments identified pure softwood as the preferable feedstock for a reasonable yield and large surface areas.Influence of operational parameters, i.e., activating gas flow rate (CO2), heating ramp rate and contact time on final biochar characteristics, was investigated using design of experiments. Surface area and biochar yield were selected as response variables.Minitab was used to define experimental run conditions and suggested optimal output, through maximum responses, was achieved at 60 min contact time and 15 °C/min ramp rate. The highest surface area (764 m2/g) was achieved at 850 °C fromsoftwood, albeit with a low yield of 15 %. Under optimised conditions, the observed surface area was 613 m2/g with 18 % yield. Pareto charts suggested no influence of gas flow rate on the chosen responses, which correlated well with experimental data.Pore structure was a combination of micro- and mesopores, with average pore widths of 3-5 nm and an average point of zero charge of 7.40 ± 0.02. Proximate analysis showed an increase in fixed carbon content from 20 %, in the feedstock, to 80 %, in the optimised biochar, while morphological analysis showed a layered carbon structure in the biochars. The results show the significance of the selected feedstock as a potential source of biochar material, and the relevance of interplay of operational variables in biochar development and their final characteristics. The characteristicsalso suggest application of the produced biochar in water remediation.The optimised biochar sample suggested by Minitab and correlated by experimental data, gave a high surface area and a mix of microporous and mesoporous nature with an average pore width of 4 nm. Morphological analysis revealed a layered carbonstructure as expected and spectroscopic analysis showed the presence of oxygen and nitrogen-based functionalities. The biochar had an average point of zero charge slightly above neutral. The sample was subsequently used for further analysis andapplication against three persistent organic pollutant species.Challenge of the biochar sample against 3,4-dichloroaniline, acetaminophen and carbamazepine from water, allowed assessment of the removal efficiency and performance as an adsorbent material. 3-4, DCA kinetic rates were rapid (<5 min),restricting kinetic analysis, while a pseudo second order kinetic model was best suited to represent the kinetic data for acetaminophen and carbamazepine, suggestingchemical control. The adsorption equilibria were most appropriately described by the Sips isotherm model, supplementing the chemical control theory for a multilayer system. Maximum adsorption capacity was relatively high for all three chemicals, andthe biochar demonstrated good removal efficiency against all target species compared to similar systems, showing potential as an adsorbent. The investigations in this work highlight the importance of the combined effects of initial operating parameters on produced biochars, demonstrating the importance of understandingthe interplay of process variables, as well as the potential of the chosen feedstock to act as an adsorbent for vital environmental applications.
- Advisor / supervisor
- Fletcher, Ashleigh
- Resource Type
- DOI
Relações
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PDF of Thesis T16841 | 2024-05-22 | Público | Baixar |