15 research outputs found
Silver-Ion Solid Phase Extraction Separation of Classical, Aromatic, Oxidized, and Heteroatomic Naphthenic Acids from Oil Sands Process-Affected Water
The separation of
classical, aromatic, oxidized, and heteroatomic
(sulfur-containing) naphthenic acid (NA) species from unprocessed
and ozone-treated oil sands process-affected water (OSPW) was performed
using silver-ion (Ag-ion) solid phase extraction (SPE) without the
requirement of pre-methylation for NAs. OSPW samples before SPE and
SPE fractions were characterized using ultra performance liquid chromatography
ion mobility time-of-flight mass spectrometry (UPLC-IM-TOFMS) to corroborate
the separation of distinct NA species. The mass spectrum identification
applied a mass tolerance of Ā±1.5 mDa due to the mass errors of
NAs were measured within this range, allowing the identification of
O<sub>2</sub>SāNAs from O<sub>2</sub>āNAs. Moreover,
separated NA species facilitated the tandem mass spectrometry (MS/MS)
characterization of NA compounds due to the removal of matrix and
a simplified composition. MS/MS results showed that classical, aromatic,
oxidized, and sulfur-containing NA compounds were eluted into individual
SPE fractions. Overall results indicated that the separation of NA
species using Ag-ion SPE is a valuable method for extracting individual
NA species that are of great interest for environmental toxicology
and wastewater treatment research, to conduct species-specific studies.
Furthermore, the separated NA species on the milligram level could
be widely used as the standard materials for environmental monitoring
of NAs from various contamination sites
Evaluation of Membrane Fouling for In-Line Filtration of Oil Sands Process-Affected Water: The Effects of Pretreatment Conditions
Membrane filtration is an effective reclamation option
for oil
sands process-affected water (OSPW). However, fresh OSPWs contain
suspended solids and inorganic constituents in suspended and dissolved
forms that can severely foul membranes. Pretreatment of OSPW with
coagulationāflocculation (CF) was investigated to determine
the effects of different coagulant aids (anionic, cationic, and nonionic
polymers) on membrane surface properties and fouling. Our results
showed that CF pretreatment effectively enhanced nanofiltration (NF)
and reverse osmosis (RO) membrane permeate flux and salt rejection
ratio through reducing membrane fouling. It was shown that coagulants
and coagulant aids applied to OSPW feedwater can affect membrane physicochemical
properties (surface hydrophilicity, zeta potential, and morphology),
membrane performance, and the fouling indexes. Membrane rejection
of ionic species increased significantly with the inclusion of an
anionic coagulant aid and slightly with a cationic coagulant aid.
Among three coagulant aids tested, anionic coagulant aids led to the
most enhanced membrane performance through increasing membrane surface
negativity and decreasing the formation of a fouling layer. Conversely,
although cationic coagulant aids were the most effective in reducing
OSPW turbidity, the application of cationic coagulant aids promoted
the adsorption of foulants on membrane surfaces
Ultra Performance Liquid Chromatography Ion Mobility Time-of-Flight Mass Spectrometry Characterization of Naphthenic Acids Species from Oil Sands Process-Affected Water
Ultraperformance
liquid chromatography ion mobility time-of-flight
mass spectrometry (UPLC-IM-TOFMS), integrating traveling wave ion
mobility spectrometry (TWIMS) with negative electrospray ionization
(ESI) mode, was used to achieve two-dimensional (2D) separation (drift
vs retention times) of naphthenic acids (NAs). Unprocessed and ozonated
commercial NAs were used for method development. Only O<sub>2</sub>āNAs were found in unprocessed NAs with ozonation creating
O<sub>3</sub>āNAs and O<sub>4</sub>āNAs. Unprocessed
and ozonated oil sands process-affected waters (OSPW) were examined
to validate the method for complex matrix NAs. Ozonation increased
the <i>x</i> number for O<sub><i>x</i></sub>āNAs
(2 ā¤ <i>x</i> ā¤ 5) and also impacted the ā<i>Z</i> number distribution. OSPW extracted using dichloromethane
removed the potential for sample matrix impacts and was used for MS/MS
NAs characterization. The O<sub><i>x</i></sub>āNAs
(2 ā¤ <i>x</i> ā¤ 6) were identified with O<sub>2</sub>āNAs separated into three clusters indicating isobaric
and isomeric species. MS/MS was used to verify compounds, while also
indicating the presence of CH<sub>3</sub>CH<sub>2</sub>Sā NAs
groups. This result may be useful for future studies of sulfur-NAs
fate, toxicity, and treatment. Overall, the value-added information
provided by UPLC-IM-TOFMS makes it a promising analytical technique
for analysis of NAs in complex OSPW samples. Moreover, this methodology
can be used for other matrices to investigate relative molecular sizes
and to separate complex species (e.g., fatty acids, lipids), making
it beneficial for environmental and bioanalytical applications
Impact of an extracellular polymeric substance (EPS) precoating on the initial adhesion of <i>Burkholderia cepacia</i> and <i>Pseudomonas aeruginosa</i>
<div><p>Extracellular polymeric substances (EPS) significantly influence bacterial adhesion to solid surfaces, but it is difficult to elucidate the role of EPS on bacterial adhesion due to their complexity and variability. In the present study, the effect of EPS on the initial adhesion of <i>B. cepaciaepacia</i> PC184 and <i>P. aeruginosa</i> PAO1 on glass slides with and without an EPS precoating was investigated under three ionic strength conditions. The surface roughness of EPS coated slides was evaluated by atomic force microscopy (AFM), and its effect on initial bacterial adhesion was found to be trivial. X-ray photoelectron spectroscopy (XPS) studies were performed to determine the elemental surface compositions of bacterial cells and substrata. The results showed that an EPS precoating hindered bacterial adhesion on solid surfaces, which was largely attributed to the presence of proteins in the EPS. This observation can be attributed to the increased steric repulsion at high ionic strength conditions. A steric model for polymer brushes that considers the combined influence of steric effects and DLVO interaction forces is shown to adequately describe bacterial adhesion behaviors.</p>
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Comparison of Nitrilotriacetic Acid and [<i>S</i>,<i>S</i>]āEthylenediamineā<i>N</i>,<i>N</i>ā²ādisuccinic Acid in UVāFenton for the Treatment of Oil Sands Process-Affected Water at Natural pH
The application of
UVāFenton processes with two chelating
agents, nitrilotriacetic acid (NTA) and [<i>S</i>,<i>S</i>]-ethylenediamine-<i>N</i>,<i>N</i>ā²-disuccinic acid ([<i>S</i>,<i>S</i>]-EDDS),
for the treatment of oil sands process-affected water (OSPW) at natural
pH was investigated. The half-wave potentials of FeĀ(III/II)ĀNTA and
FeĀ(III/II)ĀEDDS and the UV photolysis of the complexes in Milli-Q water
and OSPW were compared. Under optimum conditions, UVāNTAāFenton
exhibited higher efficiency than UVāEDDSāFenton in the
removal of acid extractable organic fraction (66.8% for the former
and 50.0% for the latter) and aromatics (93.5% for the former and
74.2% for the latter). Naphthenic acids (NAs) removals in the UVāNTAāFenton
process (98.4%, 86.0%, and 81.0% for classical NAs, NAs + O (oxidized
NAs with one additional oxygen atom), and NAs + 2O (oxidized NAs with
two additional oxygen atoms), respectively) under the experimental
conditions were much higher than those in the UVāH<sub>2</sub>O<sub>2</sub> (88.9%, 48.7%, and 54.6%, correspondingly) and NTAāFenton
(69.6%, 35.3%, and 44.2%, correspondingly) processes. Both UVāNTAāFenton
and UVāEDDSāFenton processes presented promoting effect
on the acute toxicity of OSPW toward <i>Vibrio fischeri</i>. No significant change of the NTA toxicity occurred during the photolysis
of FeĀ(III)ĀNTA; however, the acute toxicity of EDDS increased as the
photolysis of FeĀ(III)ĀEDDS proceeded. NTA is a much better agent than
EDDS for the application of UVāFenton process in the treatment
of OSPW
Investigation of Mono/Competitive Adsorption of Environmentally Relevant Ionized Weak Acids on Graphite: Impact of Molecular Properties and Thermodynamics
The
thermodynamics of adsorption and competitive interactions of
five weak acids on a graphite surface was assessed in alkaline solutions.
Adsorption of the acids in mono- and multicompound solutions followed
their Freundlich isotherms which suggest a diversity of graphite adsorption
sites as confirmed by the presence of carboxylic and phenolic groups
observed on graphite surfaces. Thermodynamic calculations assigned
the formation of the negatively charged assisted hydrogen bond (āCAHB)
between ionized solutes and adsorbent surface groups as the possible
adsorption mechanism. However, the similar p<i>K</i><sub>a</sub> values of current acids resulted in comparable free energies
for āCAHB formation (Ī<i>G</i><sup>āCAHB</sup>) being less than solvation free energies (Ī<i>G</i><sub>Solv</sub>). Thus, additional Ī<i>G</i> is supplemented
by increased hydrophobicity due to proton exchange of ionized acids
with water (ĪĪ<i>G</i><sub>Hydrophobicity</sub>). Adsorption capacities and competition coefficients indicated that
ĪĪ<i>G</i><sub>Hydrophobicity</sub> values depend
on the neutral and ionized acid <i>K</i><sub>ow</sub>. Competitive
adsorption implies that multilayer adsorption may occur via hydrophobic
bonding with the CH<sub>3</sub> ends of the self-assembled layer which
affects the acid adsorption capacities in mixtures as compared to
monocompound solutions. The determination of adsorption mechanisms
will assist in understanding of the fate and bioavailability of emerging
and classical weak acids released into natural waters
Oxidation of Oil Sands Process-Affected Water by Potassium Ferrate(VI)
This paper investigates
the oxidation of oil sands process-affected
water (OSPW) by potassium ferrateĀ(VI). Due to the selectivity of ferrateĀ(VI)
oxidation, two-ring and three-ring fluorescing aromatics were preferentially
removed at doses <100 mg/L FeĀ(VI), and one-ring aromatics were
removed only at doses ā„100 mg/L FeĀ(VI). FerrateĀ(VI) oxidation
achieved 64.0% and 78.4% removal of naphthenic acids (NAs) at the
dose of 200 mg/L and 400 mg/L FeĀ(VI) respectively, and NAs with high
carbon number and ring number were removed preferentially. <sup>1</sup>H nuclear magnetic resonance (<sup>1</sup>H NMR) spectra indicated
that the oxidation of fluorescing aromatics resulted in the opening
of some aromatic rings. Electron paramagnetic resonance (EPR) analysis
detected signals of organic radical intermediates, indicating that
one-electron transfer is one of the probable mechanisms in the oxidation
of NAs. The inhibition effect of OSPW on <i>Vibrio fischeri</i> and the toxicity effect on goldfish primary kidney macrophages (PKMs)
were both reduced after ferrateĀ(VI) oxidation. The fluorescing aromatics
in OSPW were proposed to be an important contributor to this acute
toxicity. Degradation of model compounds with ferrateĀ(VI) was also
investigated and the results confirmed our findings in OSPW study
Application of a Solar UV/Chlorine Advanced Oxidation Process to Oil Sands Process-Affected Water Remediation
The
solar UV/chlorine process has emerged as a novel advanced oxidation
process for industrial and municipal wastewaters. Currently, its practical
application to oil sands process-affected water (OSPW) remediation
has been studied to treat fresh OSPW retained in large tailings ponds,
which can cause significant adverse environmental impacts on ground
and surface waters in Northern Alberta, Canada. Degradation of naphthenic
acids (NAs) and fluorophore organic compounds in OSPW was investigated.
In a laboratory-scale UV/chlorine treatment, the NAs degradation was
clearly structure-dependent and hydroxyl radical-based. In terms of
the NAs degradation rate, the raw OSPW (pH ā¼ 8.3) rates were
higher than those at an alkaline condition (pH = 10). Under actual
sunlight, direct solar photolysis partially degraded fluorophore organic
compounds, as indicated by the qualitative synchronous fluorescence
spectra (SFS) of the OSPW, but did not impact NAs degradation. The
solar/chlorine process effectively removed NAs (75ā84% removal)
and fluorophore organic compounds in OSPW in the presence of 200 or
300 mg L<sup>ā1</sup> OCl<sup>ā</sup>. The acute toxicity
of OSPW toward Vibrio fischeri was
reduced after the solar/chlorine treatment. However, the OSPW toxicity
toward goldfish primary kidney macrophages after solar/chlorine treatment
showed no obvious toxicity reduction versus that of untreated OSPW,
which warrants further study for process optimization
Impact of Peroxydisulfate in the Presence of Zero Valent Iron on the Oxidation of Cyclohexanoic Acid and Naphthenic Acids from Oil Sands Process-Affected Water
Large volumes of oil sands process-affected water (OSPW)
are produced
during the extraction of bitumen from oil sands in Alberta, Canada.
The degradation of a model naphthenic acid, cyclohexanoic acid (CHA),
and real naphthenic acids (NAs) from OSPW were investigated in the
presence of peroxydisulfate (S<sub>2</sub>O<sub>8</sub><sup>2ā</sup>) and zerovalent iron (ZVI). For the model compound CHA (50 mg/L),
in the presence of ZVI and 500 mg/L S<sub>2</sub>O<sub>8</sub><sup>2ā</sup>, the concentration decreased by 45% after 6 days
of treatment at 20 Ā°C, whereas at 40, 60, and 80 Ā°C the
concentration decreased by 20, 45 and 90%, respectively, after 2 h
of treatment. The formation of chloro-CHA was observed during ZVI/S<sub>2</sub>O<sub>8</sub><sup>2ā</sup> treatment of CHA in the
presence of chloride. For OSPW NAs, in the presence of ZVI alone,
a 50% removal of NAs was observed after 6 days of exposure at 20 Ā°C.
The addition of 100 mg/L S<sub>2</sub>O<sub>8</sub><sup>2ā</sup> to the solution increased the removal of OSPW NAs from 50 to 90%.
In absence of ZVI, a complete NAs removal from OSPW was observed in
presence of 2000 mg/L S<sub>2</sub>O<sub>8</sub><sup>2ā</sup> at 80 Ā°C. The addition of ZVI increased the efficiency of NAs
oxidation by S<sub>2</sub>O<sub>8</sub><sup>2ā</sup> near room
temperature. Thus, ZVI/S<sub>2</sub>O<sub>8</sub><sup>2ā</sup> process was found to be a viable option for accelerating the degradation
of NAs present in OSPW
Probing the Adsorption of Weak Acids on Graphite Using Amplitude ModulationāFrequency Modulation Atomic Force Microscopy
Recent
thermodynamics calculations and adsorption isotherms showed that the
adsorption of a self-assembled layer (SAL) of ionized weak acids to
carbon was attributed to the negatively charged hydrogen bonding (āCAHB),
yet the direct visualization and characterization of this adsorption
behavior have not been reported. Here, an amplitude modulationāfrequency
modulation atomic force microscopy (AMāFM AFM) technique was
applied to discriminate the adsorption of decanoic acids (DA) on highly
ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed
that the adsorption of SAL was driven by the formation of āCAHB
with negatively charged functional groups of HOPG. Multilayer adsorption
could occur over the adsorbed ionized SAL, leading to the development
of aggregates. AMāFM AFM imaging showed that the adsorption
of the DA molecules forming aggregates occurred only for the HOPG-functionalized
steps, while DA molecules were found to adsorb over the entire functionalized
HOPG surface after water-plasma treatment, as evident from the frequency
shifts identified in AFM images