Photocatalytic degradation kinetics of naphthenic acids in oil sands process-affected water: Multifactorial determination of significant factors.
Oil sands process-affected water (OSPW) is generated as a byproduct of bitumen extraction in Canada's oil sands. Due to the water's toxicity, associated with dissolved acid extractable organics (AEO), especially naphthenic acids (NAs), along with base-neutral organics, OSPW may require treatment to enable safe discharge to the environment. Heterogeneous photocatalysis is a promising advanced oxidation process (AOP) for OSPW remediation, however, predicting treatment efficacy can be challenging due to the unique water chemistry of OSPW from different tailings ponds. The objective of this work was to study various factors affecting the kinetics of photocatalytic AEO degradation in OSPW. The rate of photocatalytic treatment varied significantly in two different OSPW sources, which could not be accounted for by differences in AEO composition, as studied by high resolution mass spectrometry (HRMS). The effects of inorganic water constituents were investigated using factorial and response surface experiments, which revealed that hydroxyl (HO) radical scavenging by iron (Fe3+) and bicarbonate (HCO3-) inhibited the NA degradation rate. The effects of NA concentration and temperature on the treatment kinetics were also evaluated in terms of Langmuir-Hinshelwood and Arrhenius models; pH and temperature were identified as weak factors, while dissolved oxygen (DO) was critical to the photo-oxidation reaction. Accounting for all of these variables, a general empirical kinetic expression is proposed, enabling prediction of photocatalytic treatment performance in diverse sources of OSPW.
Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada; Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
Tim
T
Leshuk
Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
Diogo
D
de Oliveira Livera
Water Science and Technology Directorate, Environment Canada, 11 Innovation Blvd, Saskatoon, Saskatchewan, S7N 3H5, Canada.
Kerry M
KM
Peru
Water Science and Technology Directorate, Environment Canada, 11 Innovation Blvd, Saskatoon, Saskatchewan, S7N 3H5, Canada.
John V
JV
Headley
Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
Sucharita
S
Vijayaraghavan
Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
Timothy
T
Wong
Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada; Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada. Electronic address: frank.gu@uwaterloo.ca.
Frank
F
Gu
D002170:Canada; D002264:Carboxylic Acids / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007700:Kinetics; D061329:Oil and Gas Fields / Q000737:chemistry*; D010782:Photolysis; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity
D002264:Carboxylic Acids; D014874:Water Pollutants, Chemical; C046170:naphthenic acid
Nanoparticles; Naphthenic acids; Oil sands; Photocatalysis; Titanium dioxide