Oil Sands Process Research Articles

Solar photocatalytic degradation of model naphthenic acids mixtures by Bi2WO6 and Bi2WO6/NiO/Ag: Exploring the influence of inorganic fraction of oil sands process water

This study investigates the comparative photocatalytic degradation of six model naphthenic acids, key organic constituents responsible for the toxicity of oil sands process water, using the semiconductor photocatalysts Bi2WO6 and Bi2WO6/NiO/Ag in both buffered solution and the inorganic fraction of OSPW. The heterojunction catalyst (Bi2WO6/NiO/Ag) exhibited the highest removal efficiencies for these organic pollutants with k values 0.048, 0.036, 0.019, 0.283, 0.026, and 0.075 min−1 for 1-adamantanecarboxylic acid, cyclohexanecarboxylic acid, tetrahydropyran-4-carboxylic acid, tetrahydro-2H-thiopyran-4-carboxylic acid, isonipecotic acid, and 4,5-dihydronaphtho[1,2-b]thiophene-2-carboxylic acid, respectively. Experimental analysis suggested that chloride and bicarbonate inhibited the photocatalytic degradation of the target naphthenic acids, while nitrate could accelerate the production of aminyl radicals, enhancing the degradation of isonipecotic acid. Notably, four additional nitrated and hydroxylated by-products were identified during 1-adamantanecarboxylic acid degradation in the presence of nitrate. The addition of the catalyst not only accelerated the degradation rate of 1-adamantanecarboxylic acid but also helped mitigate the formation of potentially toxic by-products. Additionally, the transformation products of 4,5-dihydronaphtho[1,2-b] thiophene-2-carboxylic acid were identified. Degradation pathways were further elucidated with the assistance of density functional theory calculations, identifying the β-carbon as the initial reactive site, with the sulfur atom also playing a significant role in reactivity. These findings contribute to the understanding of the water matrix-induced transformation process of model naphthenic acids during photocatalytic treatment, enhancing the environmental applicability of photocatalytic treatments.

Solar-activated tin oxide photocatalysis for efficient naphthenic acids removal and toxicity reduction in oil sands process water

This research studied, for the first time, the effect of activating tin oxide (SnO2) under simulated solar light for treating real oil sands process water (OSPW). The solar/SnO2 system effectively eliminated fluorophore organic contaminants, classical naphthenic acids (O2-NAs), and oxidized NAs (Oxy-NAs) from OSPW. The best experimental conditions to remove over 90 % of O2-NAs were found to be 0.5 g/L SnO2 under 8 h of irradiation. HO• and O2•– species identified by electron paramagnetic resonance (EPR) analysis played an important role in the degradation of NAs and other contaminants in real OSPW. The initial toxic effects of untreated OSPW were noticeably reduced after treatment, with a reduction of approximately 50 % in acute toxicity using Microtox® bioassay and over 80 % in the level of bioavailable hydrocarbons. In addition, the process also demonstrated a significant reduction in immunotoxicity as measured using an immune cell bioassay and reduced the toxic effects on Staphylococcus warneri using an adapted bacterial minimal inhibitory concentration (MIC) viability assay. These results suggest that treated OSPW by SnO2 under solar light has high environmental compatibility, indicating it is safe for reuse in further applications.

Detecting naphthenic acids in oil sands process water with microbial electrochemical sensor: Impact of inoculum sources and quorum sensing autoinducer

This study presents the inaugural demonstration of a microbial electrochemical cell (MXC)-based biosensor for naphthenic acids (NAs) detection in oil sands process water (OSPW) from a mining site. During the calibration process, different operating parameters were evaluated, including standing times (3 – 12 hours) and charging durations (5 – 20 minutes) within the charging-discharging cycles. The observations ascertained that a combination of a 12-hour standing period followed by a 15-minute charging period yielded the optimal current output when measuring NA concentrations ranging from 4.98 to 24.9 mg/L in real OSPW samples (diluted to concentrations of 20–100 %). Subsequently, incorporating diverse inoculum sources from MXCs led to significant signal output improvements, with one sustained on a mixture of cyclohexane carboxylic acids, commercial naphthenic acids, and real OSPW, and another exposed to acetate medium for over four years. Moreover, integrating quorum sensing (QS) autoinducers (10 μM) increased the current generation, highlighting the potential for more sensitive detection capabilities. Ultimately, our MXC biosensor could enable a cost-effective and rapid detection of OSPW NAs, offering a potential alternative for environmental surveillance.

Analysis of Naphthenic Acid–Salt Interactions in Simulated Oil Sands Process Water

Analysis of Naphthenic Acid–Salt Interactions in Simulated Oil Sands Process Water

Attenuation of phenylnaphthenic acids related to oil sands process water using solar activated calcium peroxide: Influence of experimental factors, mechanistic modeling, and toxicity evaluation

Refractory naphthenic acids (NAs) are among the primary toxic compounds in oil sands process water (OSPW), a matrix with a complex chemical composition that poses challenges to its remediation. This study evaluated the effectiveness of calcium peroxide (CaO2) combined with solar radiation (solar/CaO2) as an advanced water treatment process for degrading model NAs (1,2,3,4-tetrahydronaphthalene-2-carboxylic acid, pentanoic acid, and diphenylacetic acid) in synthetic water (STW) and provide preliminary insights in treating real OSPW. Solar light and CaO2 acted synergistically to degrade target NAs in STW (>67 of synergistic factor) following a pseudo-first-order kinetic (R2 ≥ 0.95), with an optimal CaO2 dosage of 0.1 g L–1. Inorganic ions and dissolved organic matter were found to hinder the degradation of NAs by solar/CaO2 treatment; however, the complete degradation of NAs was reached in 6.7 h of treatment. The main degradation mechanism involved the generation of hydroxyl radicals (•OH), which contributed ∼90% to the apparent degradation rate constant (K), followed by H2O2 (4–5%) and 1O2 (0–5%). The tentative transformation pathways of three NAs were proposed, confirming an open-ring reaction and resulting in short-chain fatty acid ions as final products. Furthermore, a reduction in acute microbial toxicity and genotoxic effect was observed in the treated samples, suggesting that solar/CaO2 treatment exhibits high environmental compatibility. Furthermore, the solar/CaO2 system was successfully applied as a preliminary step for real-world applications to remove natural NAs, fluorophore organic compounds, and inorganic components from OSPW, demonstrating the potential use of this technology in the advanced treatment of oil-tailing-derived NAs.

Phytoremediation of metals in oil sands process affected water by native wetland species

Process affected water and other industrial wastewaters are a major environmental concern. During oil sands mining, large amounts of oil sands process affected water (OSPW) are generated and stored in ponds until reclaimed and ready for surface water discharge. While much research has focused on organics in process waters, trace metals at high concentrations may also pose environmental risks. Phytoremediation is a cost effective and sustainable approach that employs plants to extract and reduce contaminants in water. The research was undertaken in mesocosm scale constructed wetlands with plants exposed to OSPW for 60 days. The objective was to screen seven native emergent wetland species for their ability to tolerate high metal concentrations (arsenic, cadmium, copper, chromium, copper, nickel, selenium, zinc), and then to evaluate the best performing species for OSPW phytoremediation. All native plant species, except Glyceria grandis, tolerated and grew in OSPW. Carex aquatilis (water sedge), Juncus balticus (baltic rush), and Typha latifolia (cattail) had highest survival and growth, and had high metal removal efficiencies for arsenic (81–87 %), chromium (78–86 %), and cadmium (74–84 %), relative to other metals; and greater than 91 % of the dissolved portions were removed. The native plant species were efficient accumulators of all metals, as demonstrated by high root and shoot bioaccumulation factors; root accumulation was greater than shoot accumulation. Translocation factor values were greater than one for Juncus balticus (chromium, zinc) and Carex aquatilis (cadmium, chromium, cobalt, nickel). The results demonstrate the potential suitability of these species for phytoremediation of a number of metals of concern and could provide an effective and environmentally sound remediation approach for wastewaters.

β-cyclodextrin modified GO ultrafiltration membranes with enhanced antifouling property for water purification

The study investigated the influence of additives on the fabrication of mixed matrix membranes comprising polyethersulfone (PES), with a specific focus on hydrophilicity, flux, morphology, and antifouling properties. Carboxymethyl modified β-cyclodextrin (CMβ-CD) was used to enhance the dispersion and hydrophilicity of graphene oxide (GO), leading to the formation of a hydrophilic and stable composite nanoparticle (CMCD@GO). The hydrophilicity (WCA <51.5°) and water flux (32.6 L m−2.h−1) of the modified PES membranes (MCDGO-x) were improved by the incorporation of CMCD@GO nanoparticles, while that of PES membrane was 79.7° and 10.6 L m−2.h−1. The rate of backscattered light intensity (ΔBS) of MCDGO-x suspensions remains stable, suggesting stable dispersion of CMCD@GO in organic solvents. Compared to the bare PES membrane, the MCDGO-x membrane exhibits a thinner active layer and a finger-like structure. The MCDGO-x membrane exhibited excellent naphthenic acids (NAs) rejection (>93.2%) due to reduced roughness and higher hydrophilicity, while the GO-modified PES membrane (MGO-5) exhibited lower NAs rejection (87.2%). Furthermore, the MCDGO-5 membrane showed higher flux recovery ratio (FRR) of 79.3% compared to MGO-5 membrane (68.5%) after three cycles, indicating the antifouling performance of MCDGO-x for NAs was significantly improved. The combination of CMβ-CD and GO enhance the flux and antifouling properties of PES ultrafiltration membranes, suggesting significant potential for applications in the purification of oil sands process water and the treatment of oily wastewater.

Potential of biochar and humic substances for phytoremediation of trace metals in oil sands process affected water

Oil sands process affected water (OSPW) is produced during bitumen extraction and typically contains high concentrations of trace metals. Constructed wetlands have emerged as a cost effective and green technology for the treatment of metals in wastewaters. Whether the addition of amendments to constructed wetlands can improve metal removal efficiency is unknown. We investigated the synergistic effects of carbon based amendments and wetland plant species in removal of arsenic, cadmium, cobalt, chromium, copper, nickel, and selenium from OSPW. Three native wetland species (Carex aquatilis, Juncus balticus, Scirpus validus) and two amendments (canola straw biochar, nano humus) were investigated in constructed wetland mesocosms over 60 days. Amendment effect on metal removal efficiency was not significant, while plant species effect was. Phytoremediation resulted in removal efficiencies of 78.61–96.31 % for arsenic, cadmium, and cobalt. Carex aquatilis had the highest removal efficiencies for all metals. Amendments alone performed well in removing some metals and were comparable to phytoremediation for cadmium, cobalt, copper, and nickel. Metals were primarily distributed in roots with negligible translocation to shoots. Our work provides insights into the role of plants and amendments during metal remediation and their complex interactions in constructed treatment wetlands.

Comprehensive characterization of organics in oil sands process water in constructed mesocosms utilizing multiple analytical methods

This study aims to provide a thorough characterization of dissolved organics in oil sands process water (OSPW) in field-based aquatic mesocosms at both molecular and bulk measurement levels using multiple analytical methods. In a 3-year outdoor mesocosm experiment, the analysis of naphthenic acid (NA) species was conducted using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS). The results revealed the removal of both total NAs (38% and 35%) and classical NAs (O2–NAs, 58% and 49%) in undiluted and half-diluted OSPW, respectively. The increased ratios of oxidized NAs (O3–O6 NAs) to classical NAs suggested a transformation trend. The results also indicated that O2–NAs with higher carbon number and lower double bond equivalent (DBE) were more easily degraded in the mesocosm systems. Biomimetic extraction using solid-phase microextraction (BE-SPME) measurement displayed 26% (undiluted OSPW) and 30% (half-diluted OSPW) decrease in total bioavailable organics over 3 years. Naphthenic acids fraction compounds (NAFCs) obtained by liquid-liquid extraction (LLE) were also determined using Fourier transform infrared spectroscopy (FTIR). Reduction in acute toxicity for undiluted (43%) and half-diluted (26%) OSPW was observed over 3 years, which are well correlated with the decreases of NAs and BE-SPME concentrations. Moreover, BE-SPME values were found to be linearly correlated with total NAs concentrations (r = 0.96) and NAFCs (r = 0.96). Additionally, the linear relationships of individual O2–O6 NA species and BE-SPME concentrations unveiled the changes in the relative abundances of O2–O6 NA species in total bioavailable organics over time in the mesocosms. The present study has provided comprehensive insights by integrating various analytical methods, contributing valuable information for assessing the effectiveness of aquatic mesocosm systems in studying the temporal changes of organics in OSPW.

Electrochemical reclamation of oil sands process water: Two and three-dimensional electrode configuration systems structured with different anode materials

Several studies have indicated the potential of the electrochemical advanced oxidation process in oil sands process water (OSPW) reclamation; however, the variations in different electrode configuration systems and anode materials remain elusive. This study assembled a two-dimensional electrode system (2-DES) and a packed bed electrode reactor (PBER) for OSPW reclamation, of which boron-doped diamond (BDD) (non-active anode), dimensionally stable anodes (DSA-RuO2 and DSA-IrO2) and graphite (active anodes) were selected as the anode materials, while in PBER, spherical activated carbon (SAC) was added as the third electrode. Within the 2-DES, BDD achieved over 60% removal of chemical oxygen demand (COD) due to its excellent •OH generation ability, while DSAs generated the most active chlorine and were quickly consumed by organic matter during the first 30 minutes. However, mass transfer limitation restricted the 2-DES treatment efficiency regardless of the anode materials employed, particularly resulting in limited removal of naphthenic acids (NAs). Compared to 2-DES, PBER significantly improved the OSPW treatment under identical electrolysis conditions, achieving over 91% COD and 99% NAs removal using DSA-IrO2 + SAC. Because of the contribution of the third electrode in PBER, the performance differences between various anode materials were less substantial than in the case of 2-DES. Packed SAC enhanced the mass transfer performance and generation of radical oxidants during OSPW electrolysis, improving the OSPW electrochemical treatment process. Additionally, SAC adsorbed most free chlorine from the liquid phase, avoiding the formation of halogenated organic compounds in reclaimed OSPW.

Digital twin and control of an industrial-scale bitumen extraction process

This article presents a digital twin solution for bitumen extraction process required to study process dynamics, control, and optimization of this critical oil sands process. It captures the actual process interconnectivity and scale, enabling the bidirectional data connection between the virtual and physical entities. The proposed model was validated using data from an oil sands extraction facility. Results demonstrate the model well mimics real process behavior in both steady-state and dynamic conditions, with tunable parameters tailored for any further adaption. The model was used to study extraction performance under various production scenarios. It enables analyzing process behavior and testing strategies to optimize bitumen recovery.

UVA LED-assisted breakdown of persulfate oxidants for the treatment of real oil sands process water: Removal of naphthenic acids and evaluation of residual toxicity

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 (O2-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 O2-NAs (i.e., 90 %). In addition, oxidized NAs (O3- and O4-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.

Electrocatalytic activation of peroxomonosulfate (PMS) under aerobic condition for the remediation of oil sands process water: Insight into one-pot synergistic coupling of PMS electro-activation and heterogeneous electro-Fenton processes

Alkaline industrial effluents possess a different challenge during treatment by advanced oxidation processes due to the reduction in redox potential of hydroxyl radical (•OH) in basic media. Herein, electrocatalytic peroxomonosulfate activation (EC-PMS), which synergistically couples an early-stage PMS electro-activation (E-PMS) with subsequent heterogeneous electro-Fenton oxidation (HEF) catalyzed by Fe-modified biochar (BC-Fe) was investigated for enhanced degradation and mineralization of organics in oil sands process water (OSPW). The EC-PMS was first studied for the degradation of surrogate naphthenic acids (NAs) (5-phenylvalveric acid, (PVA)) as a synthetic process water and complete degradation of 50 mg L−1 PVA solution was achieved within very short treatment time (0.5 h) with excellent mineralization (>70 % TOC removal) in 6 h. The efficiency of EC-PMS for PVA degradation was affected by the applied current density, PMS, and catalyst dosage. The organic degradation, electroparamagnetic resonance spectrometry, quenching and chemical probe experiments showed that sulfate radical (SO4•−) generated by E-PMS was the dominant radical oxidant for the degradation of PVA, contributing over 93 %, whereas •OH produced from BC-Fe decomposition of electrogenerated H2O2 in HEF was responsible for the mineralization of the organic solution at the later stage of the coupled process. The EC-PMS showed excellent reusability and was effective for the treatment of real OSPW, achieving complete degradation of real NAs in OSPW and relatively good mineralization of the water. Analysis of the EC-PMS treated OSPW did not simulate any response during the bioactivity assay test using a macrophage cell line, indicating the complete detoxification of the water.

Examining the immunotoxicity of oil sands process affected waters using a human macrophage cell line

Oil sands process affected water (OSPW) is produced during the surface mining of the oil sands bitumen deposits in Northern Alberta. OSPW contains variable quantities of organic and inorganic components causing toxic effects on living organisms. Advanced Oxidation Processes (AOPs) are widely used to degrade toxic organic components from OSPW including naphthenic acids (NAs). However, there is no established biological procedure to assess the effectiveness of the remediation processes. Our previous study showed that human macrophage cells (THP-1) can be used as a bioindicator system to evaluate the effectiveness of OSPW treatments through examining the proinflammatory gene transcription levels. In the present study, we investigated the immunotoxicological changes in THP-1 cells following exposure to untreated and AOP-treated OSPW. Specifically, using proinflammatory cytokine protein secretion assays we showed that AOP treatment significantly abrogates the ability of OSPW to induce the secretion of IL-1β, IL-6, IL-8, TNF-α, IL-1Ra and MCP-1. By measuring transcriptional activity as well as surface protein expression levels, we also showed that two select immune cell surface markers, CD40 and CD54, were significantly elevated following OSPW exposure. However, AOP treatments abolished the immunostimulatory properties of OSPW to enhance the surface expression of these immune proteins. Finally, a transcriptome-based approach was used to examine the proinflammatory effects of OSPW as well as the abrogation of immunotoxicity following AOP treatments. Overall, this research shows how a human macrophage cell-based biomonitoring system serves as an effective in vitro tool to study the immunotoxicity of OSPW samples before and after targeted remediation strategies.

Ozone in the boreal forest in the Alberta Oil Sands Region

Abstract. Measurements of ozone were made using an instrumented tower and a tethersonde located in a forested region surrounded by oil sands production facilities in the Athabasca Oil Sands Region (AOSR). Our observations and modeling show that the concentration of ozone was modified by vertical mixing, photochemical reactions, and surface dry deposition. Measurements on the tower demonstrated that when winds are from the direction of anthropogenic emissions from oil sand extraction and processing facilities, there is no significant increase in ozone mixing ratio compared to when winds are from the direction of undisturbed forest. This suggests that ozone is destroyed by reaction with NOx from oil sands extraction operations (as well as NO resulting from photolysis of NO2). Vertical gradients of ozone mixing ratio with height were observed using instruments on a tethered balloon (up to a height of 300 m) as well as a pulley system and two-point gradients within the canopy. Strong gradients (ozone increasing with height near 0.35 ppb m−1) were measured in the canopy in the evening and overnight, while morning and daytime gradients were weaker and highly variable. A 1D canopy model was used to simulate the diurnal variation of the in-canopy gradient. Model results suggest an ozone dry deposition velocity between 0.2 and 0.4 cm s−1 for this location. Sensitivity simulations using the model suggest that the local NO concentration profile and coefficients of vertical diffusivity have a significant influence on the O3 concentrations and profiles in the region.

Evaluating the attenuation of naphthenic acids in constructed wetland mesocosms planted with Carex aquatilis

Surface oil sands mining and extraction in northern Alberta’s Athabasca oil sands region produce large volumes of oil sands process–affected water (OSPW). OSPW is a complex mixture containing major contaminant classes including trace metals, polycyclic aromatic hydrocarbons, and naphthenic acid fraction compounds (NAFCs). Naphthenic acids (NAs) are the primary organic toxicants in OSPW, and reducing their concentrations is a priority for oil sands companies. Previous evidence has shown that constructed wetland treatment systems (CWTSs) are capable of reducing the concentration of NAs and the toxicity of OSPW through bioremediation. In this study, we constructed greenhouse mesocosms with OSPW or lab process water (LPW) (i.e., water designed to mimic OSPW minus the NAFC content) with three treatments: (1) OSPW planted with Carex aquatilis; (2) OSPW, no plants; and (3) LPW, no plants. The OSPW–C. aquatilis treatment saw a significant reduction in NAFC concentrations in comparison to OSPW, no plant treatments, but both changed the distribution of the NAFCs in similar ways. Upon completion of the study, treatments with OSPW saw fewer high-molecular-weight NAs and an increase in the abundance of O3- and O4-containing formulae. Results from this study provide invaluable information on how constructed wetlands can be used in future remediation of OSPW in a way that previous studies were unable to achieve due to uncontrollable environmental factors in field experiments and the active, high-energy processes used in CWTSs pilot studies.

Electrochemical degradation of dissolved organic matters in oil sands process water using continuous-flow packed bed electrode reactor

In this study, a continuous-flow packed bed electrode reactor (PBER) was presented for the first time to reclaim oil sands process water (OSPW) generated during the bitumen extraction of oil sands surface mining. The PBER was constructed based on a traditional two-dimensional electrode system (2-DES) by packing pretreated spherical activated carbon (SAC) between the anode and cathode, forming the third electrode, charged and polarized under the electric field. The electrochemical treatment effect of three essential control factors, including cell voltage, electrode space, and flow rate, were investigated on the degradation of dissolved organic matters (DOMs) in OSPW. Electrolysis for 180 min under obtained optimal conditions: cell voltage 10 V, electrode space 6 cm and flow rate 5 mL/min, achieved 74.49% COD and 65.85% DOC removal percentage in PBER compared with only 11.72% and 12.97% achieved in 2-DES at similar conditions. The energy consumption and current efficiency were also significantly improved from 12.29 to 2.21 kW·h/g COD and 9.81% to 54.59%, respectively, thanks to the application of the third electrode. Further analysis revealed that the naphthenic acids (NAs), the primary source of acute toxicity in OSPW, were effectively degraded during PBER electrolysis, which was also validated by the Microtox® test that showed no acute toxicity in the PBER-treated OSPW, indicating that PBER could significantly improve the OSPW's biodegradability. This study first demonstrated that PBER was a prospective technology for process water recycling in oil sands production and tailings ponds reclamation, particularly compared to the traditional 2-DES electrolysis.

Enhanced bitumen extraction from oil sands using CO2-responsive surfactant combined with low-salinity brine: Toward cleaner production via CO2 utilization

With a recent concern on more sustainable production, oil sands as an affordable energy resource requires more efficient and cleaner technology to extract bitumen from its deposits. Recent study conceptualized the combination of greener bitumen recovery and CO2 utilization, which shows promising potential. Using CO2-responsive surfactants that could ‘switch’ the bitumen-water interfacial behavior, oil-water separation process can be greatly improved, although its workability in bitumen aeration stage and co-presence with brines are not yet fully examined. In the current study, influence of a combination of CO2-responsive surfactant and NaCl brine fluids to bitumen liberation and aeration stages were investigated. Two interfacial phenomena (i.e., bitumen-water interfacial tension and bitumen-water-substrate contact angle) were studied as dominant parameters to oil sands processing. Although an ultra-low interfacial tension at high mixture concentration (6 mM surfactant + 500 mM NaCl) promises an advantage for bitumen extraction via a spontaneous bitumen pinch-off, some bitumen residual was left unproduced on substrate. While the low-salinity brine at the same surfactant concentration (6 mM surfactant + 10 mM NaCl) resulted in a much-reduced bitumen-substate contact area, which could practically enhance bitumen liberation. Furthermore, CO2-responsive surfactant suggests a good switchability in such a high-salinity environment for bitumen-water demulsification, owing to the CO2-induced acidification. In aeration stage, CO2 bubble was found a greater ‘attachability’ to bitumen surface compared to typical air bubble. This observation suggests a promising CO2 utilization as an alternative flotation gas carrier for bitumen aeration. The findings in the current study provide fundamental guidance on bitumen extraction process enhanced by both surfactant and brine fluids. The study also confirms a holistic improvement for the whole extraction process with CO2 utilization toward a cleaner production that couples both climate action and affordable energy sustainable goals.

Z-scheme plasmonic Ag decorated Bi2WO6/NiO hybrids for enhanced photocatalytic treatment of naphthenic acids in real oil sands process water under simulated solar irradiation

A novel photocatalyst, Bi2WO6/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 Bi2WO6, 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.

Near-infrared carbon quantum dots from PEG-based deep eutectic solvents for high-accuracy quantitative analysis of naphthenic acids in wastewater

Naphthenic acids (NAs) are toxic components in refinery wastewater and in oil sands process water. The presence of NAs in aqueous environments would cause serious environmental problems. Development of a rapid method for screening and determination of trace NAs is urgent. In this work, a near-infrared fluorescence carbon quantum dots (CQDs) was successfully synthesized with p-phenylenediamine (PPD) and polyethylene glycol 400 (PEG 400) by the hydrothermal method. It showed a good fluorescence response to NAs with good detectability. The limit of detection was calculated to be 0.16 mmol‧L−1, with a linear range from 0.5 to 15 mmol‧L−1. The detection mechanism of NAs and CQDs was also proposed with in situ infrared spectrometer. This work provides new insights into the fluorescence detection of CQDs in the petrochemical industry, broadening the application of CQDs in the detection of environmental organic pollutants.