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Title: Investigating the adsorption of select polar functionalities with the aqueous electrolyte/amorphous silica interface to understand the 'low salinity' effect
Author: Desmond, Jasmine L.
ISNI:       0000 0004 5924 1933
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2015
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Low-salinity enhanced oil recovery (EOR) uses low-salinity seawater in the water flooding of sandstone reservoirs to maximise oil yields. Because oil is strongly adsorbed onto mineral surfaces, understanding the interactions involved at the oil/mineral interface, and how to weaken them, is crucial to design more efficient, low-cost EOR. This thesis focuses on the influence of electrolyte concentration on the interaction of alkylammonium (R-NH+3) and alkylcarboxylic acid/carboxylate (R-COOH/COO- functionalities, present in crude-oil, with the amorphous silica (mimic for quartz grains in sandstone)/aqueous electrolyte interface. Both computational (molecular dynamics, MD) and experimental (chemical force mapping atomic force microscopy, CFM-AFM) techniques were used. Firstly (Chapter 3), we tested the inter-operability of the new SPC/Fw water force-field with CHARMM. No significant differences were found between the data generated from SPC/Fw-CHARMM and TIPS3P-CHARMM, therefore the latter, computationally more efficient, was used in Chapters 4-6. The behaviour of the four electrolyte solutions at two concentrations was tested in Chapters 4-5 (NaCl, KCl, CaCl2 and MgCl2 at 0.1 and 0.3 M); interfacial ion and water structuring has been investigated in Chapter 4, while the effect of the electrolytes on the adsorption of R-NH+3) and alkylcarboxylic acid/carboxylate (R-COOH/COO-) was explored in Chapter 5. Interfacial ion concentration was greatest in the CaCl2 case, with various long-lived surface-site types involving different combinations of ions identified. CFM-AFM showed a substantial concentration-dependent difference in adhesion for R-NH+3 in CaCl2 and R-COOH/COO- in the divalent ion solutions. The free energy of adsorption for NH+3 CH3 was investigated using metadynamics. Force curves were calculated from the generated free energy profiles. The greatest force is, indeed, observed for one particular surface-site type in CaCl2 solution, prevalent in more concentrated solutions. Finally, a more sophisticated computational model for the experimental AFM tip, a small array of S(CH211NH3+) is presented in Chapter 6, laying the basis for future work.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry