Physical and Chemical Treatment of Oil Sands Process-Affected Water with Polyaluminum Chloride and Potassium Ferrate(VI)

• Author / Creator

  Wang, Chengjin

• This study investigated the application of polyaluminum chloride (PACl) and potassium ferrate(VI) for the treatment of oil sands process-affected water (OSPW). In addition, the performance of potassium ferrate(VI) was compared with other oxidation processes, including UV/hydrogen peroxide (H2O2), and ozonation with and without hydroxyl radical (∙OH) scavenger. The comparison of the performance not only involved the removal of naphthenic acids (NAs) and aromatics, but also the oxidation of sulfur and nitrogen containing species. PACls are commonly used in water treatment with the most effective species reported to be Al13. In this research, PACl with 83.6% Al13 was synthesized using the slow base titration method and compared with a commercially available PACl in terms of aluminum species distribution, coagulation/flocculation (CF) performance, floc morphology, and contaminant removal. Both coagulants were effective in removing suspended solids, achieving over 96% turbidity removal at all applied coagulant doses (0.5-3.0 mM Al). The removal efficiencies of metals varied among different metals depending on their pKa values. Metal cations with pKa values (Fe, Al, Ga, and Ti) below OSPW pH of 6.9-8.1 (dose dependent) were removed by more than 90%, while metal cations with higher pKa values (K, Na, Ca, Mg and Ni) had removals of less than 40%. NAs were not removed due to their low molecular weights, negative charges, and hydrophilic characteristics at the OSPW pH. At the highest applied coagulant dose of 3.0 mM Al, the synthetic PACl reduced Vibrio fischeri inhibition effect to 43.3±3.0% from 49.5±0.4% in raw OSPW. In contrast, no reduction of toxicity was found for OSPW treated with the commercial PACl. Based on water quality and floc analyses, the dominant CF mechanism for particle removal during OSPW treatment was considered to be enmeshment in the precipitates (i.e., sweep flocculation). Potassium ferrate(VI) showed high selectivity in oxidizing the organic fraction of OSPW. It preferentially removed two-ring and three-ring fluorescing aromatics at doses <100 mg/L Fe(VI), and one-ring aromatics were removed only at doses ≥100 mg/L Fe(VI). Ferrate(VI) oxidation achieved 64.0% and 78.4% removal of classical NAs (NAs with two oxygen atoms) at the dose of 200 mg/L and 400 mg/L Fe(VI), respectively, and NAs with high carbon number and ring number were removed preferentially. 1H nuclear magnetic resonance (1H NMR) spectra indicated that the oxidation of fluorescing aromatics resulted in the opening of some aromatic rings. Electron paramagnetic resonance (EPR) analysis detected the signals of organic radical intermediates, indicating that one-electron transfer is one of the probable mechanisms in the oxidation of NAs. The efficiency of three different oxidation processes, including UV/H2O2 oxidation, ferrate(VI) oxidation, and ozonation with and without ∙OH scavenger tert-butyl alcohol (TBA) on the removal of organic compounds in OSPW was investigated and compared. UV/H2O2 oxidation occurred through radical reaction and photolysis, transforming one-ring, two-ring, and three-ring fluorescing aromatics simultaneously and achieving 42.4% of classical NA removal at 2.0 mM H2O2 and 950 mJ/cm2 UV dose. Ferrate(VI) oxidation exhibited high selectivity as mentioned above. At 2.0 mM Fe(VI), 46.7% of classical NAs was removed. Ozonation achieved almost complete removal of fluorescing aromatics, sulfur-containing NAs (NAs+S), and classical NAs (97.1% removal) at the utilized O3 dose of 2.0 mM. Both molecular ozone reaction and ∙OH reaction were important pathways in transforming the organics in OSPW as supported by the ozonation performance with and without TBA. All the three oxidation processes reduced the acute toxicity towards Vibrio fischeri and on goldfish primary kidney macrophages (PKMs), with ozonation being the most efficient process. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) analyses revealed that Ox species (species containing no other heteroatoms except oxygen) were the dominant species among the organic species (i.e., Ox; OxSy: sulfur-containing species; OxNy: nitrogen-containing species; and OxSy1Ny2: sulfur and nitrogen containing species) in OSPW, accounting for 82.3% and 51.3% of the total species detected in negative and positive electrospray ionization (ESI) mode, respectively. The oxidation processes transformed the distribution profiles of Ox, OxSy, and OxNy fractions, with the most significant changes occurring to OxSy. It was also noted that the selectivity of the oxidants impacted the transformation patterns, especially embodied by different performance by different oxidants detected in negative ESI mode on transforming O2 to O3 and/or O4 and on transforming O2S to O3S and/or O4S.

• Subjects / Keywords

  • Potassium Ferrate
  • Oil Sands Process-Affected Water
  • Polyaluminum Chloride

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3JH3D97H

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.