期刊
APPLIED SURFACE SCIENCE
卷 571, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.apsusc.2021.151253
关键词
Biomass; Electron microscopy; NMR spectroscopy; Photoelectron spectroscopy; Surface chemistry
类别
资金
- Queen Mary University of London
- EPSRC [EP/S019138/1]
- EPSRC [EP/S019138/1] Funding Source: UKRI
Surface chemistry and morphology of walnut shells-derived biochars were studied to understand adsorption strengths of solvents to pore surfaces using NMR measurements and X-ray photoelectron spectroscopy. Alkaline pretreatment was found to enhance hydrophilicity and interactions with hydroxyl groups. Results indicated potential modulation of adsorption properties by controlling factors like surface hydrophilicity, particle size, and pore accessibility.
The surface chemistry and morphology of biochars produced by pyrolysis of walnut shells affects their utility for adsorption applications. Yet, little is known about surface interactions in the pores of these materials, mostly due to the challenging nature of accessing information at this length scale in a non-destructive manner. Here, for the first time, the relative adsorption strengths of solvents comprising different functional groups to internal (pore) surfaces of walnut shells and derived biochars were investigated using low-field nuclear magnetic resonance (NMR) relaxation time measurements to non-destructively probe interactions of fluids with pore surfaces. Carbon bonding state compositions of these materials with respect to distance from the particle surface were determined using X-ray photoelectron spectroscopy coupled with ion beam etching. Alkaline pretreatment was found to increase the hydrophilicity of both walnut shells and derived biochars. It was found to increase surface interactions with hydroxyl groups, and to decrease those with methyl groups. Results were contextualised by thermogravimetric analysis, scanning electron microscopy, and previous in-situ X-ray imaging results. Taken together, results showed that alkaline pretreatment may be used to modulate responses to pyrolysis temperature of several factors that affect adsorption properties including surface hydrophilicity, particle size, porosity, pore accessibility, and surface texture.
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