Oil Sands Process-Affected Water Characterization and Application of Adsorption Process for the Removal of Naphthenic Acids

  • Author / Creator
    Ibrahim, Mohamed
  • Many techniques have been used to identify and quantify the naphthenic acids (NAs) in the oil sands process-affected water (OSPW) such as gas chromatography mass spectrometry (GC-MS), high performance liquid chromatography mass spectrometry (HPLC-MS), ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS), and Fourier transformation infrared (FTIR) spectroscopy. Extraction methods widely used in NAs quantification are liquid-liquid extraction (LLE), and solid phase extraction (SPE) methods. In his research, as a step forward to the establishment of standard method for quantifying NAs, the effects of extraction methods on quantifying NAs using FTIR and UPLC-TOFMS methods by implementing two standards (Fluka NAs and OSPW extract) were studied. Our results showed higher recovery of both the Ox-NAs (i.e., total NAs or sum of classical (O2) and oxidized species) and naphthenic acid fractions compounds (NAFCs) in SPE compared to LLE, regardless the water source. However, for O2 species, LLE and SPE acquired significant similar concentrations with higher abundance values in LLE (e.g., OSPW samples: (63.1 %) than SPE (58.5%). The high hydrophobicity of O2 species governed the extraction efficiency and increased their transport (i.e., from water to solvent) thus increasing their recovery in LLE. To improve our understanding of FTIR method, which is suggested as a standard method for routine monitoring of OSPW, a statistical analysis was implemented to assess the effect of sample type, preparation methods and standard type on quantifying the acid extractable fraction (AEF) using FTIR method. For samples preparation, LLE and SPE methods were used in this study while Fluka and OSPW extract were used as standard chemicals for calibration and quantification. It was found that SPE AEF was 1.37 times the AEF yielded using the LLE method. The AEF quantified using the OSPW extract standard method was 2.5 times higher than that quantified using the Fluka NA standard. SPE method, which is based on the adsorption process, was found to be effective in separating the NAs from the OSPW samples. Therefore, among different OSPW treatment techniques, adsorption process was selected to study the removal the NAs from the OSPW samples. Carbon xerogel (CX) is a material that can be synthesized to provide textural characteristics that adhere to specific contaminants present in all forms. Therefore, mesoporous carbon CX was synthesized in the laboratory and used as an adsorbent to study its performance in removing model NAs. The adsorption capacity and kinetics were compared to those obtained using granular activated carbon (GAC). The effects of solution pH, temperature, and ion strength on the adsorption of a Trans-4-Pentylcyclohexanecarboxylic acid (TPCA), A NA model compound, on the CX and GAC surface were investigated herein. Moreover, the kinetics and thermodynamics of the process were included in this study. Results confirmed that the adsorption was a physical process (activation energy Ea = 9.75 and 1.2 KJ.mol-1 for CX and GAC, respectively) and best described by Langmuir isotherm (R2 = 0.97 and 0.96 for CX and GAC, respectively). The maximum adsorption capacity of the CXand GAC based on Langmuir isotherm was calculated as 69.9 and 102 mg g-1, respectively. The adsorption kinetics followed the pseudo first order and intra-particle diffusion kinetics models were both appropriate in defining the adsorption of TPCA to CX and GAC (R2≥0.90). Pore diffusion was the rate limiting step, but film diffusion still maintained a significant role in the rate of diffusion of NAs. The effect of initial solution pH on the adsorption process was significant, while temperature and ion strength effect were minimal. The findings of this work are important for standardizing the NA identification and quantification method for monitoring industrial process water including the OSPW. Moreover, the deep understanding of the effect of the sample pre-treatment, chemical standards and the sample type on the FTIR method results, opens a new venue for comparing the results from different studies that were generated using different techniques. The generated comparative database will be usefull for the monitoring and remediation of OSPW. The removal of NA model compounds from alkaline water using new adsorbent will help in developing a treatment approach designed to remove the contaminant from OSPW as first step towards safely releasing it into the environment.

  • Subjects / Keywords
  • Graduation date
    Spring 2018
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
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