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288 results on '"Stevens, Lee A."'

12. Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years

Author

Weber, Michael E., Bailey, Ian, Hemming, Sidney R., Martos, Yasmina M., Reilly, Brendan T., Ronge, Thomas A., Brachfeld, Stefanie, Williams, Trevor, Raymo, Maureen, Belt, Simon T., Smik, Lukas, Vogel, Hendrik, Peck, Victoria L., Armbrecht, Linda, Cage, Alix, Cardillo, Fabricio G., Du, Zhiheng, Fauth, Gerson, Fogwill, Christopher J., Garcia, Marga, Garnsworthy, Marlo, Glüder, Anna, Guitard, Michelle, Gutjahr, Marcus, Hernández-Almeida, Iván, Hoem, Frida S., Hwang, Ji-Hwan, Iizuka, Mutsumi, Kato, Yuji, Kenlee, Bridget, OConnell, Suzanne, Pérez, Lara F., Seki, Osamu, Stevens, Lee, Tauxe, Lisa, Tripathi, Shubham, Warnock, Jonathan, and Zheng, Xufeng

Published
2022
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26. Designing topographically textured microparticles for induction and modulation of osteogenesis in mesenchymal stem cell engineering

Author

Amer, Mahetab H., Alvarez-Paino, Marta, McLaren, Jane, Pappalardo, Francesco, Trujillo, Sara, Wong, Jing Qian, Shrestha, Sumana, Abdelrazig, Salah, Stevens, Lee A., Lee, Jong Bong, Kim, Dong-Hyun, González-García, Cristina, Needham, David, Salmerón-Sánchez, Manuel, Shakesheff, Kevin M., Alexander, Morgan R., Alexander, Cameron, and Rose, Felicity RAJ

Published
2021
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37. Exploring the Utilisation of Natural Biosorbents for Effective Methylene Blue Removal.

Author

Güleç, Fatih, Williams, Orla, Samson, Abby, Kostas, Emily T., Stevens, Lee A., and Lester, Edward

Subjects
METHYLENE blue, ADSORPTION capacity, ADSORPTION isotherms, ADSORPTION kinetics, FREUNDLICH isotherm equation, LANGMUIR isotherms
Abstract

This paper presents a comprehensive analysis of the adsorbent capacity of five distinctly different biosorbents derived from untreated biomasses. The optimal adsorption capacity of seaweed (Laminaria digitata), horse chestnut husk, hazelnut husk, rapeseed residue, and whitewood to remove methylene blue (MB) dye was assessed by analysing the effects of particle size, pH, temperature, and initial dye concentrations. Furthermore, the adsorption kinetics, isotherms, and adsorption thermodynamics were investigated. The results showed that relatively high MB adsorption capacity was achieved by Laminaria digitata (~180 mg/g), in addition to a reasonable MB adsorption capacity of horse chestnut husk (~130 mg/g), hazelnut husk (~110 mg/g), and rapeseed residue (~80 mg/g). However, whitewood provides a relatively low adsorption capacity of below 20 mg/g. The best fit with experimental results regardless of biosorbent type was a pseudo-second-order kinetic model with the lowest mean absolute percentage error (ε, MAPE < 2.5%) and the highest correlation coefficients (R2 > 0.99). Although the pseudo-second-order kinetic model is often associated with chemisorption, the low enthalpy values (<29.30 kJ/mol) typically suggest that the adsorption process is more characteristic of physisorption, which involves weaker van der Waals forces rather than the stronger covalent bonds of chemisorption. This proposed a multi-step adsorption process involving both physisorption and chemisorption. The adsorption isotherm of Langmuir showed superior fitting results for Laminaria digitata and hazelnut husk. In contrast, rapeseed residue and horse chestnut husk fit better with the Freundlich adsorption isotherm. The Langmuir adsorption isotherms showed a maximum adsorption capacity of ~500 mg/g for Laminaria digitata, followed by horse chestnut husk (~137 mg/g), hazelnut husk (~120 mg/g), and rapeseed residue (~85 mg/g). The Gibbs free energy was negative for Laminaria digitata < horse chestnut husk < hazelnut husk < 0, which suggests that the removal of MB is thermodynamically favourable, as the adsorption process occurs spontaneously. The results of the study indicate that MB dye removal using untreated biomasses has the potential to be a low-cost valorisation option in the holistic whole life cycle valorisation pathway for Laminaria digitata, horse chestnut husk, and hazelnut husk. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Valorization Strategies in CO 2 Capture: A New Life for Exhausted Silica-Polyethylenimine.

Author

Coralli, Irene, Giuri, Demetra, Spada, Lorenzo, Ortolani, Jacopo, Mazzocchetti, Laura, Tomasini, Claudia, Stevens, Lee A., Snape, Colin E., and Fabbri, Daniele

Subjects
CARBON sequestration, POLYETHYLENEIMINE, SOLVENT extraction
Abstract

The search for alternative ways to give a second life to materials paved the way for detailed investigation into three silica-polyethylenimine (Si-PEI) materials for the purpose of CO2 adsorption in carbon capture and storage. A solvent extraction procedure was investigated to recover degraded PEIs and silica, and concomitantly, pyrolysis was evaluated to obtain valuable chemicals such as alkylated pyrazines. An array of thermal (TGA, Py-GC-MS), mechanical (rheology), and spectroscopical (ATR-FTIR, 1H-13C-NMR) methods were applied to PEIs extracted with methanol to determine the relevant physico-chemical features of these polymers when subjected to degradation after use in CO2 capture. Proxies of degradation associated with the plausible formation of urea/carbamate moieties were revealed by Py-GC-MS, NMR, and ATR-FTIR. The yield of alkylpyrazines estimated by Py-GC-MS highlighted the potential of exhausted PEIs as possibly valuable materials in other applications. [ABSTRACT FROM AUTHOR]

Published
2023
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44. A comprehensive comparative study on methylene blue removal from aqueous solution using biochars produced from rapeseed, whitewood, and seaweed via different thermal conversion technologies

Author

Williams, Orla, Kostas, Emily T., Samson, Abby, Stevens, Lee A., and Lester, Edward

Subjects
Fuel Technology, General Chemical Engineering, Organic Chemistry, Energy Engineering and Power Technology
Abstract

This paper presents, for the first time, a comprehensive comparative analysis of the potential of using biochars from three distinctly different UK-sourced biomass feedstocks, produced via three different thermal processing techniques, to adsorb methylene blue dye. Biochars were made from rapeseed, whitewood, and seaweed (Laminaria Digitata), produced via hydrothermal conversion, pyrolysis, and torrefaction. Adsorption kinetic models were developed for each biochar at different temperatures, pH and initial dye concentrations. Relatively high levels of methylene blue adsorption capacity were achieved by seaweed-based biochars (∼150 mg/g), with reasonable levels for rapeseed-based biochars (∼60 mg/g), whilst adsorption levels were found to be relatively low for whitewood-based biochars (

Published
2022

47. A Guaranteed Basic Income for Canadians: Off the Table or Within Reach?

Author

Stevens, Lee, Simpson, Wayne, Stevens, Harvey, and Emery, Herb

Abstract

Pilot projects in the past that have experimented with a Guaranteed Basic Income (GBI) in Manitoba and Ontario, and a recent study of the feasibility of a GBI in British Columbia, indicate that provinces are not in an ideal position to successfully implement an affordable and effective GBI. However, a GBI implemented by the federal government, financed by eliminating the GST credit and lowering personal tax exemptions, could be both effective and affordable. It could also do so without requiring the elimination of those provincial social assistance programs that are more deeply targeted toward people’s needs. By using its revenue powers, the federal government could create more fiscal capacity for the provinces to provide other cash and in-kind social supports, allowing for greater provincial benefit targeting. The federal government’s centrality in designing and implementing tax structures and collecting tax revenue make it singularly suitable for administering and delivering a GBI. Financing the GBI by eliminating the modest GST credit and lowering the current basic personal income tax exemption could provide a significant reduction in the rate, depth and intensity of poverty in Canada, without imposing an excessive tax burden on Canadians. If provinces use the GBI as a replacement for certain less-targeted provincial social assistance income transfers, the freed-up payments and reduced caseloads could also allow provinces to target more effectively those needs not addressed by the GBI. The recent COVID-19 pandemic exposed longstanding gaps in Canada’s income- support frameworks, with lower-income workers facing exceptional economic vulnerability. At the same time, the Canadian Emergency Response Benefit proved edifying in terms of how to best design a basic-income program. In addition, the federal government’s experiences with the poverty-reducing impacts of the Canada Child Benefit, the Old Age Supplement and the Guaranteed Income Supplement have moved Canada closer than ever to a workable GBI. While it comes with additional costs, those costs will be less burdensome than many GBI skeptics might believe. They must also be put into perspective, by comparing them against the costs of current and, in many cases ineffective income transfers and, just as importantly, against the human cost of leaving more Canadians living in poverty., The School of Public Policy Publications, Vol. 15 No. 1 (2022)

Published
2022
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48. Simultaneous conventional and microwave heating for the synthesis of adsorbents for CO2 capture: Comparative study to pristine technologies

Author

Rodriguez, Jose, Kostas, Emily T., Stevens, Lee A., Binner, Eleanor, Dodds, Chris, and DURAN JIMENEZ, GABRIELA

Subjects
General Chemical Engineering, Environmental Chemistry, General Chemistry, Industrial and Manufacturing Engineering
Abstract

Microwave has become an attractive technology in the valorisation of renewable biomass and in the mitigation of challenges of climate change. In this work, the synergic effects of coupling microwave and mild conventional heating conditions has been investigated in preparing engineered ultra-micropore carbons from lignocellulosic biomass. The processing conditions were systematically investigated and correlated to the physicochemical properties of activated carbons produced and their performance in post-combustion CO2 capture. The highest CO2 uptake (225 mg g−1) was achieved for the hybrid carbon produced at low temperature (600 °C) and modest microwave intensity. The synergic effect of hybrid heating was confirmed by the significant CO2 uptake increase up to 80 and 60 % for the activated carbons prepared by microwave and conventional heating, respectively. The enhanced adsorption was confirmed by cyclic regeneration up to 99 % after 16 adsorption–desorption cycles, showing a linear correlation between the surface area, micropore volume and CO2 uptake. The Pseudo-first order model accurately describes the adsorption phenomena, indicating that physisorption is the primary mechanism governing the process. The results acquired from this study highlight the process intensification in the synthesis of porous materials with comparable properties that are typically attained in conventional heating using energy intensive conditions. Additionally, this approach reveals the benefits of conventional treatment for increasing the material's microwave susceptibility and as consequence to reduce the processing time by microwave heating. The synergic effects confirms the potential of hybrid heating for applications where fast and selective heating is paramount.

Published
2022

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