Download the full-sized PDF of Investigation of the Adsorption of Model and Oil Sands Process-Affected Water Naphthenic Acids on GraphiteDownload the full-sized PDF



Permanent link (DOI):


Export to: EndNote  |  Zotero  |  Mendeley


This file is in the following communities:

Graduate Studies and Research, Faculty of


This file is in the following collections:

Theses and Dissertations

Investigation of the Adsorption of Model and Oil Sands Process-Affected Water Naphthenic Acids on Graphite Open Access


Other title
Weak acids
Atomic force microscopy
Amplitude modulation
Naphthenci acids
Frequency modulation
Oil sands process affected water
Type of item
Degree grantor
University of Alberta
Author or creator
Moustafa, Ahmed M. A.
Supervisor and department
Mohamed Gamal El-Din (Civil and Environmental Engineering)
Examining committee member and department
Rajesh Seth (Department of Civil & Environmental Engineering, University of Windsor)
Ian D Buchanan (Civil and Environmental Engineering)
Hongbo Zeng (Chemical and Materials Engineering)
Yang Liu (Civil and Environmental Engineering)
Department of Civil and Environmental Engineering
Environmental Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Naphthenic acids (NAs) are constituents of bitumen in the oil sands deposits in northern Alberta, Canada. The extraction process of bitumen creates an enormous amount of wastewater called oil sands process affected waters (OSPW). This OSPW contains elevated concentrations of NAs, and other contaminants, that need removal in order to continue its reuse in the extraction process or eventually safe disposal into natural water streams. The research herein focuses on the understanding of NAs adsorption on the expanded graphite (EG) and highly-ordered pyrolytic graphite (HOPG). The adsorption of model NAs on EG was evaluated using Langmuir/Freundlich adsorption models and free energy thermodynamics calculations. Following the model compounds, the mechanisms for NAs adsorption of a commercial Merichem mixture and OSPW were explored. The visualization of adsorption on the surface of EG was not possible due to its irregular surface morphology. Thus, the Amplitude Modulation - Frequency Modulation Atomic Force Microscopy (AM-FM-AFM) was used to characterize the adsorption of NAs on HOPG. The adsorption of 5 model NA compounds in mono/multi-compound solutions was investigated to determine adsorption mechanisms. Overall, the NAs in both mono- and multi-compound solutions fit the Freundlich adsorption isotherms (R2 > 0.89). Thermodynamic calculations were used to assign the formation of the negatively charged assisted hydrogen bond (–CAHB) between ionized solutes and the negatively charged functional groups (FGs) on the EG as the possible adsorption mechanism. The similar pKa values of the model NAs resulted in comparable free energies for –CAHB formation (ΔG-CAHB) being less than solvation free energies (ΔGSolv). Thus, additional ΔG is supplemented by increased hydrophobicity due to proton exchange of ionized acids with water (ΔΔGHydrophobicity). Adsorption capacities and competition coefficients indicated that ΔΔGHydrophobicity values depend directly on hydrophobicity as indicated by Log Kow values. Competitive adsorption implies the occurrence of multilayer adsorption via hydrophobic bonding with CH3 ends of the self-assembled layer of NAs to the EG surface. Further study visually characterized the adsorption of decanoic acid (DA) on the surface of HOPG using AM-FM-AFM. The AM-FM-AFM images showed that DA molecules formed aggregates at the functionalized steps of HOPG and over the entire functionalized HOPG (F-HOPG). This DA adsorption to FGs in HOPG and F-HOPG confirmed the previous thermodynamics findings. The last step of this research was to understand the mechanism of NAs adsorption from complex mixtures including the Merichem NAs solution and raw OSPW. Adsorption results showed that higher Log Kow NAs have higher removal efficiency for all solutions. The calculated free energy required for the formation of –CAHB was lower than the free energy of solvation for NAs; however the –CAHB formation was still triggered by the need for additional free energy ΔΔGHydrophobicity as observed for model compounds. The presence of a large number of NAs species in both mixtures did not impact the reported mechanism.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
(1) Ahmed M.A. Moustafa, EunSik Kim, Alla Alpatova, Nian Sun, Scott Smith, Seoktae Kang, Mohamed Gamal El-Din, Impact of polymeric membrane filtration of oil sands process water on organic compounds quantification. Water Science and Technology. 2014. 70 (5), 771-779(2) Ahmed M.A. Moustafa, Kerry N. McPhedran, Jesús Moreira and Mohamed Gamal El-Din, Investigation of mono/competitive adsorption of environmentally relevant ionized weak acids on graphite: Impact of molecular properties and thermodynamics. Environmental Science & Technology. 2014. 48 (24), 14472-14480(3) Ahmed M.A. Moustafa, Jun Huang, Kerry N. McPhedran, Hongbo Zeng, and Mohamed Gamal El-Din, Probing Adsorption of Weak Acids on Graphite Using Amplitude Modulation-Frequency Modulation Atomic Force Microscopy. Langmuir, 2015. 31 (10), 3069–3075(4) Ahmed M.A. Moustafa, Kerry N. McPhedran and Mohamed Gamal El-Din, Investigation of the adsorption of ionized carboxylic acids on graphite: Using simple model compounds to understand complex mixtures. Journal of Hazardous Materials (Submitted; 30 March 2015)

File Details

Date Uploaded
Date Modified
Audit Status
Audits have not yet been run on this file.
File format: pdf (PDF/A)
Mime type: application/pdf
File size: 4936352
Last modified: 2015:10:21 22:27:26-06:00
Filename: Moustafa_Ahmed_MA_201504_PhD.pdf
Original checksum: d272e689a7fb8581ceb90621dbba2343
Activity of users you follow
User Activity Date