On Clay Minerals: Adsorption and Modification

Clay minerals are prevalent in nature and are a key component of sandstone-based oil reservoirs. Understanding the behaviour of organic components at clay mineral surfaces is therefore important for elucidating the mechanisms of oil recovery. These clay - organic interactions are of interest both in the context of oil components adsorbed to clay minerals, and for the action and attrition of surfactant packages employed in enhanced recovery. The surprising adsorption of anionic molecules onto the anionic mica surface from aqueous solution, mediated by specific cations, has been investigated. A key variation in cation behaviour down group 1A was demonstrated, where the caesium salt of the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) showed adsorption to mica, in contrast to the lack of adsorption of the sodium salt. This `cation bridging' by monovalent ions is a novel finding of the work. Further investigations with added cations revealed potassium to also mediate adsorption, and probed the importance of the ratio of cations in solution. The sodium salts of carboxylic acids were found to adsorb to mica, representing a significant difference between the behaviour of these acids and the sulfonate head-grouped AOT. The behaviour of an adsorbed layer of the cationic surfactant didodecyldimethylammonium bromide (DDAB) adsorbed on mica was studied on exposure to different species in solution, including anionic and non-ionic surfactants. Very different behaviour was seen depending on the nature of the solution species. The effect of the anionic surfactant sodium dodecyl sulfate was found to be particularly complex; below the CMC there was partial layer replacement but a thickening of the total organic layer, but significantly at the CMC complete desorption of all adsorbed material occurred. This may represent an approach to remove such strongly bound cationics. As many surface techniques require large and very flat clay surfaces, methods to produce flat surfaces on a macroscopic scale with different surface charge densities were investigated. Two candidate approaches were shown to result in modified charges. Cation exchange then heat treatment of mica was shown to partially neutralise the surface charge, in line with the literature, and sodium aluminate treated silica was shown to display an imparted negative charge. Finally, the technique of fluorescence microscopy was developed as an alternative experimental method for investigation of adsorption to mica. Through different imaging regimes, species in solution and on the surface were selectively imaged. Adsorption of cationic dyes was explored, and the surface mobility was investigated using bleach recovery measurements.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2020

Author dc:creator

• Allen, Finian

Advisor dc:contributor.advisor

• Clarke, stuart

• surface chemistry
• physical chemistry
• adsorption
• surfactant
• oil recovery
• neutron reflectivity

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6312148d-5db7-4634-bd13-efdc273f4ad8/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

Author Identifier

0000-0002-9823-562X

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/317780