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Oil sands process water (OSPW) contains organics, inorganics, and particles. To understand and improve the ozonation performance, it is crucial to clarify the effect of inorganics and particles on the ozonation of OSPW organic compounds. In this study, OSPW containing only inorganic fraction (OSPW-IF) was obtained after the organics were adsorbed onto granular activated carbon. A model naphthenic acid (NA) compound, cyclohexanecarboxylic acid (CHA), was dissolved in OSPW-IF (CHA-OSPW-IF) and NaHCO3 buffer (CHA-Buffer). Ozonation of CHA-Buffer achieved higher CHA removal and lower utilized ozone dosages compared to CHA-OSPW-IF. Some inorganic ions present in OSPW (i.e., NH4+, HCO3−, and Cl−) caused a slight reduction of CHA degradation. Inorganics in OSPW inhibited the degradation of natural-occurring NAs while a negligible influence of particles on the ozonation of NAs was found. This research suggests that ozonation could be better utilized as an intermediate or post-treatment step in a treatment train for OSPW reclamation. [ABSTRACT FROM AUTHOR]

Abstract Naphthenic acids (NAs) are one of the constituents of concerns in oil sands process water (OSPW) because of their persistence and recalcitrance. Herein, we investigated the degradation of five model NA compounds by UV-activated persulfate (UV/persulfate) process under medium-pressure UV lamp irradiation at pH 8.0. UV/persulfate process showed higher degradation efficiency towards cyclohexanoic acid (CHA) compared to UV/H 2 O 2 process under the same experimental conditions. CHA (0.39 mM) was completely removed within 30 min when 2 mM persulfate was used as oxidant, while more than 60 min were needed for the UV/H 2 O 2 process. The removal of CHA decreased from 100% to 10% when 300 mM tert-butyl alcohol (TBA) was used as the scavenger, indicating that hydroxyl radical (OH) was responsible for the CHA degradation in the UV/persulfate process. Sulfate (SO 4 −) radicals reacted slowly with CHA in the UV/persulfate process with a second-order rate constant of k = 5.3 × 107 M−1s−1. Relative kinetics studies using binary mixtures of model NA compounds showed similar structure-reactivity to that under UV/H 2 O 2 process. NAs with long carbon chain, cyclic ring, and aromatic ring were more reactive in the UV/persulfate process. The presence of high concentration of chloride ions dramatically inhibited the reaction. The OH radicals in the UV/persulfate process were generated by capturing OH− in solutions, as evidenced by the decrease of the pH value from 8.0 to 2.8 before and after treatment, respectively, in a pure water matrix. Primary intermediate products (oxy-CHA, hydroxyl-CHA, and dihydroxyl-CHA) of UV/persulfate process were confirmed by UPLC-MS. Highlights • UV activated persulfate oxidation process was used for the degradation of model NAs. • SO 4 − radical reacted slowly with CHA in UV/persulfate process compared to BA. • OH generated from SO 4 − and OH− were the main radicals responsible for the CHA removal. • Relative kinetics of model NA compounds in UV/persulfate process were studied. • The presence of chlorine ions was adverse to CHA removal and related chlorinated by-products were formed. [ABSTRACT FROM AUTHOR]

This study investigated the application of materials peat-mineral mix (PT) and Pleistocene fluvial sands from different location (PF-1 and PF-2) obtained from surface mining of oil sands as sorbents of naphthenic acids (NAs) from oil sands process water (OSPW). To understand the sorption properties and mechanisms of NAs in the materials, sorption and desorption studies were performed using decanoic acid (DA) and 5-phenylvaleric acid (PVA). Additionally, the removal efficiency was evaluated using real OSPW to understand the effect of NA structure on sorption. Equilibrium of DA and PVA was reached at 2 days for PT, and 3 and 6 days for PF materials, respectively. Langmuir isotherm best fitted the equilibrium data. Maximum sorption capacities for DA and PVA were, respectively, 16.8 × 103 and 104 mg/kg for PT, 142.9 and 81.3 mg/kg for PF-1, and 600 and 476.2 mg/kg for PF-2. Hydrophobic interactions, hydrogen bonding, and π−π interaction were the main sorption mechanisms. Desorption of model compounds from post-sorption materials was not observed for 14 days. The removal of NAs from real OSPW ranged from 20 to 54%. PT is the most promising sorbent of NAs from OSPW because it partially removed NAs with a wide range of molecular weights and structures at very low dosage. Sorption of NAs was affected by the total organic carbon of the materials, emphasizing the hydrophobic interaction as an important sorption mechanism. The results suggest that some mobility of NAs is expected to take place if the reclamation materials come in contact with OSPW, which might occur in an oil sands reclamation landscape. [Display omitted] • Three materials were studied as sorbents of model NA compounds and NAs from OSPW. • Sorption mechanisms included hydrogen bonding, hydrophobic and π−π interactions. • No desorption of model NAs from materials was observed up to 14 days of contact time. • Removal of NAs with different molecular weights and structures ranged from 9.9 to 68.3%. • TOC was the main characteristic of materials that affected the sorption of NAs from OSPW. [ABSTRACT FROM AUTHOR]

Due to their recalcitrance, naphthenic acids (NAs) are one of the constituents of interest in oil sands process water (OSPW). In this study, peroxymonosulfate (PMS) activated by ozone was employed to degrade NA model compounds in buffer solutions. At an ozone/PMS ratio of 2:1, a removal of 85 % was observed for a model diamondoid NA compound (1-adamantanecarboxylic acid; ACA) after 45 s of reaction. Compared with ozone alone, the degradation of ACA was accelerated in the presence of ozone/PMS, with an overall pseudo-first order rate constant (k obs) increasing from 8.02 × 10−4 s−1 during ozone treatment to 6.74 × 10−2 s−1 in the ozone/PMS system. Although ozone/hydrogen peroxide (H 2 O 2) showed high degradation for ACA, the ozone/PMS system showed a higher k obs of 5.44 × 10−2 s−1at a PMS dose of 0.042 mM, while at the same dose of H 2 O 2 , k obs was equal to 3.62 × 10−2 s−1 for ozone/H 2 O 2. This result showed the synergetic effect of ozone and PMS on the degradation of ACA. Relative kinetics studies using mixtures of model NA compounds showed better performance for ozone/PMS to degrade aromatic NAs compared to ozone/H 2 O 2. Hydroxyl radicals and sulfate radicals were found to be responsible for the removal of ACA, with limited effect of molecular ozone. The proposed degradation pathways for ACA included hydroxylation, carboxylation, and polymerization under ozone/PMS, while hydroxylation and carboxylation were the main degradation pathways under ozone/H 2 O 2. The results of this study emphasize the potential of ozone/PMS process to treat OSPW by accelerating the degradation of recalcitrant organic compounds. [Display omitted] • PMS was successfully activated by ozone to degrade naphthenic acids model compounds. • The degradation of ACA was accelerated in the presence of ozone/PMS. • Hydroxyl radicals and sulfate radicals were responsible for the removal of ACA. • Limited effect of molecular ozone was observed for the oxidation of model NAs. • Ozone/PMS produced intermediates via hydroxylation, carboxylation and polymerization. [ABSTRACT FROM AUTHOR]

The toxicological effects from all components in oil sands process-affected water (OSPW) are not known. Alternatively, monitoring the variations and abundance of different classes and compounds after treatments might be a useful approach in OSPW remediation. In this study, the variations in the compositions of classical and heteroatomic naphthenic acids (NAs) after treatment using advanced oxidation processes (AOPs), mainly ozone and peroxone, and two different mass spectrometry methods; ultra-performance liquid chromatography time-of-flight (UPLC-TOFMS) and Fourier transform ion cyclotron resonance (FTICR-MS), were examined. Two markers (O 2 S:O 3 S:O 4 S and O 2 :O 4 ratios) were used to reveal changes and similarities of the treated water characteristics with those in natural waters. Both ratios decreased after all treatments, from 2.7:4.8:2.1 and 3.59 in raw OSPW to 0:1.4:0.5 and 0.7, respectively, in peroxone (1:2), becoming close to the reported ratios in natural waters. Toxicity toward Vibrio fischeri showed residual toxic effects after AOPs, suggesting that part of OSPW toxicity may be caused by specific compounds of NAs (i.e., similar reduction (50%) was achieved in both toxicity and abundance in O 2 species with carbon 15–26) and/or generated by-products (e.g., O 3 S classes at double bond equivalent (DBE) = 4 and C 9 H 12 O 2 at DBE = 4). Although by-products were generated, the best biodegradability enhancement and chemical oxygen demand reduction were achieved in peroxone (1:2) compared to ozone, suggesting the possibility of using combined OSPW remediation approaches (i.e., peroxone coupled with biological process). The recommended indicators can assist in evaluating the treatments' performance and in examining the best removal levels to accomplish significant toxicity reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnCl 2 -activated biochar from sludge successfully adsorbed total NAs in raw OSPW. • Pore filling, hydrogen bonding, and π − π interactions were the adsorption mechanisms. • Biochar had selectivity for NAs with hydrophobic and higher cyclicity characteristics. • Microtox® assay indicated 66% reduction in acute toxicity after biochar treatment. • 91% reduction of bioavailability of organics was observed in OSPW treated with sludge biochar. Large volumes of oil sands process water (OSPW) containing naphthenic acids (NAs) and other contaminants are generated by oil sands operations. For the first time, pristine and zinc chloride-activated biochars from sludge from a municipal wastewater treatment plant are studied in the adsorption of NAs in real OSPW. By using activated biochar instead of pristine biochar, the adsorption capacity (q t) for total NAs (classical and oxidized NAs) increased from 2.3 to 26.6 mg/g. The increase in q t for activated biochar was related to the improvement of surface area from 7.9 to 513 m2/g, the abundance of mesopores (89% of pore volume), and the oxygen-containing surface groups. Equilibrium was reached at 2 h of contact time. Considering the thousands of structures of NAs in the OSPW, the activated biochar presented higher affinity for NAs with higher carbon and double bond equivalency numbers, therefore, NAs with more hydrophobic and higher cyclicity characteristics. Pore-filling, hydrogen bonding, and π-π interactions are the adsorption mechanisms. Thermal regeneration of spent activated biochar was studied, and in the fifth cycle of regeneration, the regenerated biochar had q t of 7.1 mg/g, which was 5 times higher than the adsorption capacity of fresh pristine biochar. Adsorption treatment of OSPW using activated biochar decreased the following parameters: metals Mg (7%), Ca (21%), Sr (27%), and Ba (60%), organic matter by means of DOC (63%) and COD (66%), acute toxicity towards V. fischeri (66%) and bioavailability of organics (91%). These findings promote circular economy as it presents an efficient adsorbent for NAs in OSPW developed from sludge, reducing the environmental impact associated with sludge disposal and allowing the efficient reclamation and reuse of OSPW. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are a highly complex mixture of organic compounds naturally present in bitumen and identified as the primary toxic constituent of oil sands process-affected water (OSPW). This work investigated the degradation of cyclohexanoic acid (CHA), a model NA compound, and natural occurring NAs during the UV photolysis of Fe(III)-nitrilotriacetic acid (UV-Fe(III)NTA) and UV-NTA-Fenton processes. The results indicated that in the UV-Fe(III)NTA process at pH 8, the CHA removal increased with increasing NTA dose (0.18, 0.36 and 0.72 mM), while it was independent of the Fe(III) dose (0.09, 0.18 and 0.36 mM). Moreover, the three Fe concentrations had no influence on the photolysis of the Fe(III)NTA complex. The main responsible species for the CHA degradation was hydroxyl radical ( OH), and the role of dissolved O 2 in the OH generation was found to be negligible. Real OSPW was treated with the UV-Fe(III)NTA and UV-NTA-Fenton advanced oxidation processes (AOPs). The removals of classical NAs (O 2 -NAs), oxidized NAs with one additional oxygen atom (O 3 -NAs) and with two additional oxygen atoms (O 4 -NAs) were 44.5%, 21.3%, and 25.2% in the UV-Fe(III)NTA process, respectively, and 98.4%, 86.0%, and 81.0% in the UV-NTA-Fenton process, respectively. There was no influence of O 2 on the NA removal in these two processes. The results also confirmed the high reactivity of the O 2 -NA species with more carbons and increasing number of rings or double bond equivalents. This work opens a new window for the possible treatment of OSPW at natural pH using these AOPs. [ABSTRACT FROM AUTHOR]

Basal aquifer water is saline groundwater that often needs to be dewatered prior to mining. The oil sands industry is seeking cost-effective methods to treat basal aquifer water in order to allow its recycle to the bitumen extraction process. A hybrid desalination system consisting of advanced electrodialysis reversal (EDR)–reverse osmosis (RO) combined with a low-temperature evaporator/crystallizer was assessed as an opportunity to treat basal aquifer water for a near-zero liquid discharge (ZLD) approach. The pilot-scale plant had a capacity of 50 m 3 /day influent. Pretreatment through sedimentation and ultrafiltration proved to be effective in removing both suspended solids and turbidity. The hybrid EDR–RO desalination system achieved about 77% recoveries, with brine concentrations up to 125,000 mg/L. The results showed that the evaporator-crystallizer was able to concentrate the EDR–RO brine to a conductivity of just over 250 mS/cm, while producing additional freshwater. This proof-of-concept study demonstrated that the hybrid EDR–RO system combined with a low-temperature evaporator/crystallizer was an effective near-zero ZLD approach to produce freshwater and minimize brine discharge when treating basal aquifer water. [ABSTRACT FROM AUTHOR]

The oil sands industry has recently focused on both reducing their freshwater usage and maximizing the reuse of process water. This study is one of the few pilot-scale investigations reporting the ability of reverse osmosis (RO) to treat recycle water (RCW) from an oil sands facility. Two distinct treatment trains were assessed to evaluate the impacts of pretreatments on the RO performance. Treatment train 1 consisted of coagulant addition, ceramic ultrafiltration (CUF), antiscalant, and a single-pass RO system operated at natural pH, while the treatment train 2 included softening, coagulant addition, CUF system, weak acid cation ion exchange, antiscalant addition, and an RO system operated at alkaline pH. RO permeate fluxes normalized to 25 °C of approximately 31–39 L/m 2 ·h at 72% recovery and 38–52 L/m 2 ·h at 85% recovery were recorded for treatment trains 1 and 2, respectively. At these conditions, the two treatment trains resulted in total dissolved solids lower than 18 mg/L, while the dissolved sodium concentrations were below 7 mg/L. During the pilot tests, clean-in-place procedures were not required for both treatment configurations, highlighting the effectiveness of the pretreatment steps to reduce the RO membrane foulants. [ABSTRACT FROM AUTHOR]

Membrane filtration is an effective treatment method for oil sands tailings pond recycle water (RCW); however, membrane fouling and rapid decrease in permeate flux caused by colloids, organic matter, and bitumen residues present in the RCW hinder its successful application. This pilot-scale study investigated the impact of different pretreatment steps on the performance of a ceramic ultrafiltration (CUF) membrane used for the treatment of RCW. Two treatment trains were examined: treatment train 1 consisted of coagulant followed by a CUF system, while treatment train 2 included softening (Multiflo™ system) and coagulant addition, followed by a CUF system. The results indicated that minimum pretreatment (train 1) was required for almost complete solids removal. The addition of a softening step (train 2) provided an additional barrier to membrane fouling by reducing hardness-causing ions to negligible levels. More than 99% removal of turbidity and less than 20% removal of total organic carbon were achieved regardless of the treatment train used. Permeate fluxes normalized at 20 °C of 127–130 L/m 2 h and 111–118 L/m 2 h, with permeate recoveries of 90–93% and 90–94% were observed for the treatment trains 1 and 2, respectively. It was also found that materials deposited onto the membrane surface had an impact on trans-membrane pressure and influenced the required frequencies of chemically enhanced backwashes (CEBs) and clean-in-place (CIP) procedures. The CIP performed was successful in removing fouling and scaling materials such that the CUF performance was restored to baseline levels. The results also demonstrated that due to their low turbidity and silt density index values, permeates produced in this pilot study were suitable for further treatment by high pressure membrane processes. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are persistent compounds that contribute to the toxicity of oil sands process-affected water (OSPW). In this study, the effects of ozone and ozone/hydrogen peroxide on the NAs degradation in buffered water and OSPW were examined. Cyclohexanoic acid (CHA) was used as a model NAs compound in buffered water experiments at two different pHs, using radical scavengers. At pH 9, the addition of carbonate did not have any effect on CHA degradation. Additions of tert-butyl alcohol and tetranitromethane decreased the CHA degradation levels. For the OSPW experiments, degradation of acid-extractable fraction (AEF) and NAs was examined. Approximately 90% of AEF was oxidized in a semi-batch system. In a batch system, 99% of OSPW NAs were degraded. This study demonstrated that ozone and ozone/hydrogen peroxide could be suitable treatment processes for OSPW remediation. [ABSTRACT FROM AUTHOR]

Oil sands process-affected water (OSPW) is a toxic and poorly biodegradable mixture of sand, silt, heavy metals, and organics. In this study, qualitative and quantitative comparisons of naphthenic acids (NAs) were done using ultraperformance liquid chromatography time-of-flight mass spectrometry (UPLC TOF- MS), Fourier transform ion cyclotron resonance (FT-ICR) MS, and ion mobility spectrometry (IMS). The unique combination of these analyses allowed for the determination and correlation of NAs, oxidized NAs, and heteroatom (sulfur or nitrogen) NAs. Despite its lower resolution, UPLC-TOF MS was shown to offer a comparable level of reliability and precision as the high resolution FT-ICR MS. Additionally, the impacts of ozonation (35 mg/L utilized ozone dose) and subsequent NAs degradation on OSPW toxicity were assessed via a collection of organisms and toxicity end points using Vibrio fischeri (nonspecific), specific fish macrophage antimicrobial responses, and fish olfactory responses. Fish macrophages exposed to ozonated OSPW for 1 week showed higher production of reactive oxygen and nitrogen intermediates; however, after 12 weeks the responses were reduced significantly Fish olfactory tests suggested that OSPW interfered with their perception of odorants. Current results indicate that the quantification of NAs species,using novel analytical methods, can be combined with various toxicity methods to assess the efficiency of OSPW treatment processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • BC/ZnO composites were successfully synthesized from wood wastes. • The BC/30 %ZnO composite showed enhanced photocatalytic performance than pure ZnO. • The composite presented good reusability and stability after 4 cycles of use. • First study applied BC/ZnO composite for NAs mixture photocatalytic degradation. • Over 95 % of NAs in mixture were degraded by BC/30 %ZnO after 6 h solar irradiation. Naphthenic acids (NAs) present in oil sands process water (OSPW) have brought increasing environmental concerns due to their potential risk to aquatic and mammalian species. In this study, sustainable biochar zinc oxide (BC/ZnO) composites were synthesized using wood waste with different ZnO content and applied under simulated solar light for the photocatalytic degradation of different NAs for the first time. The best experimental conditions were determined as 0.5 g/L BC/30%ZnO and 4 h of simulated solar irradiation time, achieving 93.7 % degradation of cyclohexanecarboxylic acid (CHA) following the pseudo-first order kinetics. BC, with a porous structure and roughened surface, acted as an excellent platform for ZnO particles and an electron reservoir to inhibit the recombination of photogenerated electron-hole pairs. Hydroxyl radicals (•OH) were identified to play the dominant role in CHA degradation, and the enhanced photocatalytic performance of the BC/30%ZnO composite was proved by more •OH species detected compared to synthesized ZnO. The composite showed good reusability and stability after 4 successive cycles of use, still achieving 92.9 % degradation of CHA. Moreover, this is the first study applying BC/30%ZnO composite for the simultaneous degradation of a complex mixture of eight NAs with significantly different chemical structures. The competition kinetics were observed among different NAs in the mixture, resulted in over 95 % degradation of total NAs after 6 h treatment. By applying wood waste-based BC/ZnO composite with excellent photocatalytic performance in combination with solar light as green energy source, this research highlights a promising sustainable approach for real OSPW remediation. [ABSTRACT FROM AUTHOR]

A novel photocatalyst, Bi 2 WO 6 /NiO/Ag, with hierarchical flower-like Z-scheme heterojunction, which exhibited excellent stability and photocatalytic activity over a wide light spectrum, was firstly synthesized and used in the remediation of real oil sands process water (OSPW) and achieved complete removal of aromatics, classical naphthenic acids (NAs), and heteroatomic NAs after 6 h of photocatalytic treatment. The acute toxicity of OSPW was completely eliminated after only 2 h of treatment. h+ and ∙OH were found to be the major oxidative species in the photocatalytic system. The enhanced photocatalytic efficiency is the result of the unique Z-scheme electron transfer among electron mediators Ag, NiO, and Bi 2 WO 6 , which was supported by the in-situ irradiated XPS. The study benefits the design of engineered passive treatment approach for OSPW remediation through solar light-driven catalyst. [Display omitted] • 3D flower-like Z scheme photocatalyst Bi 2 WO 6 /NiO/Ag was synthesized. • Bi 2 WO 6 /NiO/Ag effectively treated OSPW with 90% degradation of O 2 -NAs within 3 hrs. • Aromatics with three fused rings were more prone to degradation than single and two-ring aromatics. • NAs with different carbon number and DBE showed different degradation behaviors. • Z-scheme structure enhanced the photocatalytic activity and was verified by in-situ irradiated XPS. [ABSTRACT FROM AUTHOR]

The application of UV-Fenton processes with two chelating agents, nitrilotriacetic acid (NTA) and [S,S]-ethylenediamine-N,N'-disuccinic acid ([S,S]-EDDS), for the treatment of oil sands process-affected water (OSPW) at natural pH was investigated. The half-wave potentials of Fe(III/II)NTA and Fe(III/II)EDDS and the UV photolysis of the complexes in Milli-Q water and OSPW were compared. Under optimum conditions, UV-NTA-Fenton exhibited higher efficiency than UV-EDDS-Fenton 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 UV-NTA-Fenton 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 UV-H2O2 (88.9%, 48.7%, and 54.6%, correspondingly) and NTA-Fenton (69.6%, 35.3%, and 44.2%, correspondingly) processes. Both UV-NTA-Fenton and UV-EDDS-Fenton processes presented promoting effect on the acute toxicity of OSPW toward Vibrio fischeri. No significant change of the NTA toxicity occurred during the photolysis of Fe(III)NTA; however, the acute toxicity of EDDS increased as the photolysis of Fe(III)EDDS proceeded. NTA is a much better agent than EDDS for the application of UV-Fenton process in the treatment of OSPW. [ABSTRACT FROM AUTHOR]

Through sustainable water management, oil sands companies are working to reduce their reliance on fresh water by minimizing the amount of water required for their operations and by recycling water from tailings ponds. This study was the first pilot-scale testing of a hybrid technology consisting of froth flotation combined with filtration through precoated submerged stainless steel membranes used to treat recycle water from an oil sands facility. The results indicated that the most important factor affecting the performance of the hybrid system was the influent water quality. Any rise in the levels of suspended solids or total organic carbon of the feed water resulted in changes of chemical consumption rates, flux rates, and operating cycle durations. The selections of chemical type and dosing rates were critical in achieving optimal performance. In particular, the froth application rate heavily affected the overall recovery of the hybrid system as well as the performance of the flotation process. Optimum surfactant usage to generate froth (per liter of treated water) was 0.25 mL/L at approximately 2000 NTU of influent turbidity and 0.015 mL/L at approximately 200 NTU of influent turbidity. At the tested conditions, the optimal coagulant dose was 80 mg/L (as Al) at approximately 2000 NTU of influent turbidity and <40 mg/L (as Al) at approximately 200 NTU of influent turbidity. Precoat loading per unit membrane surface area tested during the pilot study was approximately 30 g/m 2 . The results of this study indicated that this hybrid technology can potentially be considered as a pre-treatment step for reverse osmosis treatment of recycle water. [ABSTRACT FROM AUTHOR]

The fractionation of oil sands process-affected water (OSPW) via pH-dependent extractions was performed to quantitatively investigate naphthenic acids (NAs, C n H 2 n + Z O 2 ) and oxidized NAs (O x -NAs) species (C n H 2 n + Z O 3 and C n H 2 n + Z O 4 ) using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS). A mathematical model was also developed to estimate the dissociation constant p K a for NAs species, considering the liquid–liquid extraction process and the aqueous layer acid-base equilibrium. This model provides estimated dissociation constants for compounds in water samples based on fractionation extraction and relative quantification. Overall, the sum of O 2 -, O 3 -, and O 4 -NAs species accounted for 33.6% of total extracted organic matter. Accumulative extracted masses at different pHs revealed that every oxygen atom added to NAs increases the p K a (i.e., O 2 -NAs < O 3 -NAs < O 4 -NAs), indicating that the additional O atoms exist as –OH in O 3 - and O 4 -NAs. Molecule electron-withdrawing groups such as double bonds and aromatic groups, as indicated by higher carbon and − Z number, may be responsible for the lower p K a of O 2 -, O 3 -, and O 4 -NAs. The model obtained estimated p K a values of 3.5 for O 2 -NAs, 4.8 for O 3 -NAs, and 6.8 for O 4 -NAs via nonlinear regression curve fittings. These p K a values are valuable physicochemical parameters for environmental engineering applications targeting OSPW NAs treatment. [ABSTRACT FROM AUTHOR]

Oil sands process-affected water (OSPW) is a complex mixture of organic and inorganic contaminants, and suspended solids, generated by the oil sands industry during the bitumen extraction process. OSPW contains a large number of structurally diverse organic compounds, and due to variability of the water quality of different OSPW matrices, there is a need to select a group of easily measured surrogate parameters for monitoring and treatment process control. In this study, kinetic and surrogate correlation models were developed to predict the degradation of naphthenic acids (NAs) species during the ozonation of OSPW. Additionally, the speciation and distribution of classical and oxidized NA species in raw and ozonated OSPW were also examined. The structure-reactivity of NA species indicated that the reactivity of individual NA species increased as the carbon and hydrogen deficiency numbers increased. The kinetic parameters obtained in this study allowed calculating the evolution of the concentrations of the acid-extractable fraction (AEF), chemical oxygen demand (COD), and NA distributions for a given ozonation process. High correlations between the AEF and COD and NA species were found, suggesting that AEF and COD can be used as surrogate parameters to predict the degradation of NAs during the ozonation of OSPW. [ABSTRACT FROM AUTHOR]

[Display omitted] • PDS and PMS were successfully activated by UVA LED light to treat real OSPW. • Over 90 % of classical NAs were removed by UVA LED/PDS (1 mM) or /PMS (2 mM) • The UVA LED/PDS (1 mM) was the most cost-effective system to treat OSPW. • Pre-existing immunotoxic and cytotoxic effects were markedly reduced in treated OSPW. • Treated OSPW could potentially be considered for reuse applications. This study investigated for the first time the synergistic effect of coupling persulfate (PDS) and peroxymonosulfate (PMS) with UVA LED light for the treatment of real oil sands process water (OSPW). The performance of the UVA LED/PDS and UVA LED/PMS processes was studied at different oxidant concentrations to remove fluorophore organic compounds and naphthenic acids (NAs), commonly considered significant contributors to the toxicity of raw OSPW. Both systems were highly efficient in eliminating fluorophore organic contaminants and classical NAs (O 2 -NAs) from the matrix; however, concentrations of 1 and 2 mM of PDS and PMS, respectively, were the most suitable conditions to achieve one order of magnitude removal of O 2 -NAs (i.e., 90 %). In addition, oxidized NAs (O 3 - and O 4 -NAs) were moderately degraded under these conditions. Considering economic factors, the UVA LED/PDS (1 mM) system proved to be more cost-effective than the UVA LED/PMS (2 mM) process and a viable alternative to other advanced treatments for OSPW remediation. Moreover, the pre-existing toxic effect of raw OSPW was markedly mitigated after treatment with UVA LED/PDS (1 mM), reducing by 80 % the ability of the matrix to induce pro-inflammatory cytokines in human leukemic monocytic and without significantly affecting the viability of the Staphylococcus epidermidis bacteria. Specifically for the microbial viability assay, the exposure period of the microorganism was exceptionally more extended than those considered in standard bioassays, reinforcing the scientific relevance of the obtained results. Finally, these results suggest a high environmental compatibility of the treated OSPW, making its reuse in further applications safe. [ABSTRACT FROM AUTHOR]

This work reports the monitoring and assessment of naphthenic acids (NAs) in oil sands process-affected water (OSPW), Pleistocene channel aquifer groundwater (PLCA), and oil sands basal aquifer groundwater (OSBA) from an active oil sands development in Alberta, Canada, using ultra performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) analysis with internal standard (ISTD) and external standard (ESTD) calibration methods and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) for compositional analysis. PLCA was collected at 45–51 m depth and OSBA was collected at 67–144 m depth. Results of O x −NA concentrations follow an order as OSPW > OSBA > PLCA, indicating that occurrences of NAs in OSBA were likely related to natural bitumen deposits instead of OSPW. Liquid-liquid extraction (LLE) was applied to avoid the matrix effect for the ESTD method. Reduced LLE efficiency accounted for the divergence of the ISTD and ESTD calibrated results for oxidized NAs. Principle component analysis results of O 2 and O 4 species could be employed for differentiation of water types, while classical NAs with C13−15 and Z (-4)−(-6) and aromatic O 2 −NAs with C16−18 and Z (-14)−(-16) could be measured as marker compounds to characterize water sources and potential temporal variations of samples, respectively. FTICR-MS results revealed that compositions of NA species varied greatly among OSPW, PLCA, and OSBA, because of NA transfer and transformation processes. This work contributed to the understanding of the concentration and composition of NAs in various types of water, and provided a useful combination of analytical and statistical tools for monitoring studies, in support of future safe discharge of treated OSPW. [ABSTRACT FROM AUTHOR]

There are several established methods for the determination of naphthenic acids (NAs) in waters associated with oil sands mining operations. Due to their highly complex nature, measured concentration and composition of NAs vary depending on the method used. This study compared different common sample preparation techniques, analytical instrument methods, and analytical standards to measure NAs in groundwater and process water samples collected from an active oil sands operation. In general, the high- and ultrahigh-resolution methods, namely high performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) and Orbitrap mass spectrometry (Orbitrap-MS), were within an order of magnitude of the Fourier transform infrared spectroscopy (FTIR) methods. The gas chromatography mass spectrometry (GC-MS) methods consistently had the highest NA concentrations and greatest standard error. Total NAs concentration was not statistically different between sample preparation of solid phase extraction and liquid-liquid extraction. Calibration standards influenced quantitation results. This work provided a comprehensive understanding of the inherent differences in the various techniques available to measure NAs and hence the potential differences in measured amounts of NAs in samples. Results from this study will contribute to the analytical method standardization for NA analysis in oil sands related water samples. [ABSTRACT FROM AUTHOR]

This work investigated the oxidative transformation of the organic species in oil sands process-affected water (OSPW) using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) in both negative and positive electrospray ionization (ESI) modes. This is the first time to apply FTICR-MS to investigate species transformation in OSPW treatments by ferrate (VI), UV/H 2 O 2 , and molecular ozone, and also this is the first preliminary study to use positive ESI to investigate organic species in addition to naphthenic acids (NAs) in these treatment processes. The oxidation processes with potassium ferrate (VI), UV/H 2 O 2 , and ozone transformed the distribution profiles of O x , O x S y , and O x N y organic fractions (i.e., species containing oxygen, sulfur, and nitrogen, with x, y specifying the oxygen number and sulfur/nitrogen number, respectively), with O x S y distribution profiles showing the most sensitive responses to the oxidation extent and can be used as a signature fraction to evaluate the oxidation effectiveness. Negative mode UPLC-TOF-MS confirmed the transformation pattern of O x species observed with FTICR-MS, but positive mode UPLC-TOF-MS results showed severe discrepancies with FTICR-MS results and should be subjected for future further investigation, regarding the relatively low mass resolution of UPLC-TOF-MS. The investigation of the transformation patterns of different organic species using two ionization modes was a preliminary study to enhance the understanding of the efficiency, selectivity, and mechanism of different oxidation processes in OSPW remediation for both NAs and non-NA species. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are reported to be the main species responsible for the oil sands process-affected water (OSPW) toxicity. In this study, the degradation of cyclohexanoic acid (CHA) as a model compound for NAs by an ethylenediamine- N , N ’-disuccinic acid (EDDS)-modified Fenton process was investigated at pH 8. Optimum dose for Fe-EDDS (EDDS:Fe = 2:1) was 0.45 mM, and 2.94 mM for hydrogen peroxide (H 2 O 2 ). The time profiles of the main species in the process were studied, including CHA, H 2 O 2 , Fe(II), total Fe, and Fe-EDDS (in the main form of Fe III EDDS). The second-order rate constant between EDDS and hydroxyl radical ( OH) at pH 8 was obtained as 2.48 ± 0.43 × 10 9 M −1 s −1 . OH was proved to be the main species responsible for the CHA degradation, while superoxide radical (O 2 − ) played a minor role. The consecutive addition of H 2 O 2 and Fe-EDDS led to a higher removal of CHA compared to that achieved by adding the reagents at a time. The half-wave potential of Fe III/II EDDS was measured at pH 7–9. The EDDS-modified Fenton process is a promising alternative to degrade NAs. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) from oil sand process-affected water (OSPW) were liquid–liquid extracted using six organic solvents (n-pentane, n-hexane, cyclohexane, dichloromethane, ethyl ether, and ethyl acetate) at three pHs (2.0, 8.5, and 12.0). The NAs exist in ionic (ions) and non-ionic (molecules) forms in the water phase depending on their dissociation constants and the solution pH. Results showed the extractability of NA molecules depends on the solvent polarity and the extractability of NA ions on the water solubility in solvent. The organic solvent type and solution pH were found to not only impact the extracted amounts of each NA species, but also the NAs distribution in terms of molecule carbon number and hydrogen deficiency. Overall, it is concluded that ethyl ether can be used as an alternative to dichloromethane (DCM) given their similar extraction efficiencies and extracted NA profiles. This is important since DCM is known to have metabolic toxicity and transitioning to the safer ethyl ether would eliminate laboratory DCM exposures and risk to human health. Despite the higher extraction efficiency of NAs at pH 2.0, extraction at pH 12.0 could be useful for targeted extraction of low-concentration nonpolar organic compounds in OSPW. This knowledge may assist in the determination of the specific NAs species that are known to have chronic, sub-chronic and acute toxicity to various organisms, and the potential targeting of treatment to these NAs species. [ABSTRACT FROM AUTHOR]

• The photochemical reactions of ferric citrate were used to treat OSPW. • NAs could be effectively degraded by ferric citrate under visible light irradiation. • Photocatalytic activity of ferric citrate was greatly affected by the initial pH of OSPW. • Hydroxyl radical was the dominant reactive species in the process. • The photochemical reactions of ferric citrate could produce both Fe2+ and H 2 O 2 in situ. An environmental-friendly treatment method based on photochemical reactions of ferricarboxylate complexes was developed for the treatment of oil sands process water (OSPW). Without using H 2 O 2 , the classical naphthenic acids (NAs), one of the organic compounds present in OSPW, can be effectively degraded by ferric citrate under visible light irradiation. Photochemical reaction activity of ferric citrate was greatly affected by the initial pH of OSPW. In acidic conditions, ferric citrate exhibited an extremely high degradation ratio of classical NAs, 98.3% (initial pH 3) and 96.8% (initial pH 5). Once initial pH exceeded 5, the degradation ratio of classical NAs in OSPW decreased quickly, and the degradation ratio of classical NAs could reach 65.7% (initial pH 7) and 42.4% (without adjusting pH, initial pH 8.9), respectively. It was found that the structure of NAs had little impact on the removal efficiency of NAs. It was also confirmed through scavenger experiments and reaction mechanism study that hydroxyl radical was the dominant reactive species in the process. The study demonstrated that ferric citrate possesses excellent visible light absorption ability and the photochemical reactions of ferric citrate can produce both Fe2+ and H 2 O 2 in situ , Fenton reagent, which non-selectively degrade NAs of OSPW. [ABSTRACT FROM AUTHOR]