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Naphthenic Acids (NAs) are widely believed to universally act in a stabilizing capacity during the formation of water-in-crude oil emulsions. This work provides evidence to the contrary wherein differences between commercially acquired NAs and those extracted from crude exhibit opposing effects on emulsion stability. Addition of the commercial NAs to a crude oil prior to water-in-oil emulsion formation resulted in an increase in emulsion destabilization rate. This was demonstrated via quantification of water droplet coalescence using pulsed field gradient nuclear magnetic resonance (NMR) and, over long timescales in the visual observation of the disengagement of a free water phase. The efficacy of the commercial NAs to act in such a demulsification capacity was shown to be effective at concentrations as low as 0.5v/v% and in the presence of saline water of up to 3.5 wt% NaCl. Differences in NA demulsifying ability was observed between three crude oils of various origins with some demonstrating clear visual phase separation whilst others remained in an emulsified state. Conversely, addition of NAs extracted from a crude oil at similar concentrations had negligible effect on the rate of emulsion destabilization. Comparative characterization of the commercial and indigenous NAs was performed using 1H NMR, Diffusion Ordered Spectroscopy (DOSY), Rheometry, Pendant Drop Tensiometry, and Gas Chromatography–Mass Spectrometry. The results of this characterization indicated that differences in emulsion stability were governed not by differences in the reduction of emulsion droplet interfacial tension (IFT) but by the kinetics of molecular diffusion of the NAs during both the emulsification and destabilization phases. [ABSTRACT FROM AUTHOR]

Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon steel, specifically A333 Grade 6, in a naphthenic acid solution. Various weight percentages of niobium were incorporated, and the resulting properties were observed. It was noted that the addition of 2% niobium in low-carbon steel exhibited the least mass loss and a lower corrosion rate after a 12 h immersion in naphthenic acid. Microstructural analysis using scanning electron microscopy (SEM) revealed small white particles, indicating the presence of oil sediment residue, along with corrosion pits. Following the addition of 2% niobium, the occurrence of corrosion pits markedly decreased, and only minor voids were observed. Additionally, the chemical composition analysis using energy-dispersive X-Ray analysis (EDX) showed that the black spot exhibited the highest percentage of carbon, resembling high corrosion attack. Meanwhile, the whitish regions with low carbon content indicated the lowest corrosion attack. The results demonstrated that the addition of 2% niobium yielded optimal properties for justifying corrosion effects. Therefore, low-carbon steel with a 2% niobium addition can be regarded as a superior corrosion-resistant material for offshore platform pipeline applications. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Naphthenic acids (NA) are organic compounds commonly found in crude oil and produced water, known for their recalcitrance and toxicity. This study introduces a new adsorbent, a polymer derived from spent coffee grounds (SCGs), through a straightforward cross-linking method for removing cyclohexane carboxylic acid as representative NA. The adsorption kinetics followed a pseudo-second-order model for the data (0.007 g min−1 mg−1), while the equilibrium data fitted the Sips model ( q m = 140.55 mg g−1). The process's thermodynamics indicated that the target NA's adsorption was spontaneous and exothermic. The localized sterical and energetic aspects were investigated through statistical physical modeling, which corroborated that the adsorption occurred indeed in monolayer, as suggested by the Sips model, but revealed the contribution of two energies per site ( n 1 ; n 2 ). The number of molecules adsorbed per site (n ) was highly influenced by the temperature as n 1 decreased with increasing temperature and n 2 increased. These results were experimentally demonstrated within the pH range between 4 and 6, where both C6H11COO−(aq.) and C6H11COOH(aq.) species coexisted and were adsorbed by different energy sites. The polymer produced was naturally porous and amorphous, with a low surface area of 20 to 30 m2 g−1 that presented more energetically accessible sites than other adsorbents with much higher surface areas. Thus, this study shows that the relation between surface area and high adsorption efficiency depends on the compatibility between the energetic states of the receptor sites, the speciation of the adsorbate molecules, and the temperature range studied. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) have been found to exert serious threats on offshore sediment ecosystems and human health in recent years, which entails us the urgent need for NAs remediation. Bioremediation is considered an ideal method for sediment remediation due to ecological sustainability and economic feasibility. However, current bioremediation efficiency of offshore sediments suffers from relatively slow and there has never any attempts to bioremediate offshore sediment NAs contamination hitherto. In this study, the green synthetic iron oxides (gFeOx) based on Laminaria extracts was employed to enhance the biodegradation of NAs (Cyclohexylacetic acid, CHAA) in offshore sediments by Pseudoalteromonas sp. JSTW (an indigenous microorganism). The results showed that CHAA (20 mg·kg−1) in offshore sediments was removed almost 100% within 7 days at 30 mg·kg−1 gFeOx and 0.6 mg·kg−1 Strain JSTW. High-throughput sequencing results revealed that the structure and function of sediment microbial community were essentially restored to uncontaminated levels after bioremediation, highlighting the joint remediation approach is an efficient and eco-friendly method. Overall, this work has firstly provided insights into the application for NAs in situ bioremediation in offshore sediments. [ABSTRACT FROM AUTHOR]

We evaluated whether naphthenic acid fraction compounds (NAFCs) extracted from oil sand tailings adversely affect fish survival and behaviour. Following a before–after-control-impact design, we housed wild-caught juvenile yellow perch (Perca flavescens) in outdoor mesocosms to assess survival and behaviour under baseline conditions, then exposed fish to one of three treatments: negative control, 2 mg/L NAFC, or 15 mg/L NAFC. We performed behavioural assays (no-stimulus activity, food stimulus, and predator stimulus using a model bird) and assessed a comprehensive suite of endpoints (equilibrium losses, activity, shoaling, burst swimming, freezing, and space use). We found that exposure to 15 mg/L NAFCs substantially reduced fish survival and impaired fish equilibrium in all three behavioural tests. Furthermore, exposure to NAFCs impaired anti-predator behaviour: while the activity of control fish increased by two-fold in response to a predator stimulus, fish exposed to 2 or 15 mg/L NAFC did not change their activity levels after stimulation. No significant changes were observed in other behavioural endpoints. Overall, our findings suggest that a week-long exposure to NAFCs at concentrations commonly found in tailings ponds, constructed wetlands, and other mining-impacted waters may affect multiple facets of fish behaviour that could ultimately lead to reduced fitness in fish populations.

In offshore platforms, elevated costs due to effluent quantity, logistics, space limitation, and availability of solvents hinder produced water treatment, leading petrochemical industries to develop feasible backup strategies to create a sustainable treatment of this byproduct. This context motivates the present study's proposal to use diesel oil in offshore facilities as onboard fuel to remove naphthenic acids (model compound of the dissolved organic fraction) through liquid-liquid extraction. Results achieved out in a separation funnel using synthetic produced water ([cyclohexanecarboxylic naphthenic acid] 0 = 500 mg/L) and diesel as an extracting solvent (10%) present high removal efficiencies of about 60% of the cyclohexanecarboxylic naphthenic acid present in synthetic water produced at pH 2% and 42% at pH 4. The characterization analysis of the diesel oil after the liquid-liquid extraction process indicates that it is suitable for reuse as fuel within the offshore platform dispensing further treatments. [Display omitted] [ABSTRACT FROM AUTHOR]

Oil sands process-affected water (OSPW) contains a diverse mixture of inorganic and organic compounds. Naphthenic acids (NAs) are a subset of the organic naphthenic acid fraction compounds (NAFCs) and are a major contributor of toxicity to aquatic species. Thousands of unique chemical formulae are measured in OSPW by accurate mass spectrometry and high-resolution mass spectrometry (MS) analysis of NAFCs. As no commercial reference standard is available to cover the range of compounds present in NAFCs, quantitation may best be referred to as "semi-quantitative" and is based on the responses of one or more model compounds. Negative mode electrospray ionization (ESI-) is often used for NAFC measurement but is prone to ion suppression in complex matrices. This review discusses aspects of off-line sample preparation techniques and liquid chromatography (LC) separations to help reduce ion suppression effects and improve the comparability of both inter-laboratory and intra-laboratory results. Alternative approaches to the analytical parameters discussed include extraction solvents, salt content of samples, extraction pH, off-line sample cleanup, on-line LC chromatography, calibration standards, MS ionization modes, NAFC compound classes, MS mass resolution, and the use of internal standards. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are a complex mixture of organic compounds released during bitumen extraction from mined oil sands that are important contaminants of oil sands process-affected water (OSPW). NAs can be toxic to aquatic organisms and, therefore, are a main target compound for OSPW. The ability of microorganisms to degrade NAs can be exploited for bioremediation of OSPW using constructed wetland treatment systems (CWTS), which represent a possible low energy and low-cost option for scalable in situ NA removal. Recent advances in genomics and analytical chemistry have provided insights into a better understanding of the metabolic pathways and genes involved in NA degradation. Here, we discuss the ecology of microbial NA degradation with a focus on CWTS and summarize the current knowledge related to the metabolic pathways and genes used by microorganisms to degrade NAs. Evidence to date suggests that NAs are mostly degraded aerobically through ring cleavage via the beta-oxidation pathway, which can be combined with other steps such as aromatization, alpha-oxidation, omega-oxidation, or activation as coenzyme A (CoA) thioesters. Anaerobic NA degradation has also been reported via the production of benzoyl-CoA as an intermediate and/or through the involvement of methanogens or nitrate, sulfate, and iron reducers. Furthermore, we discuss how genomic, statistical, and modeling tools can assist in the development of improved bioremediation practices. [ABSTRACT FROM AUTHOR]

The authors studied the problem of naphthenate deposits in the oil and gas industry. Currently, there are few ways available to inhibit or dissolve naphthenate deposits in oil facilities. Naphthenate deposits can block pipelines and aggregate in other parts of the installation, i.e., in the separators. In Europe, the issue of deposition on oil rigs is commonly encountered in Norway and the United Kingdom, as well as in some African countries, i.e., Angola and Nigeria. Many tons of chemicals are used to combat naphthenate deposition, usually through inhibition, but also via the dissolution of the scale that precipitates over time. The presented work examines the characteristics of naphthenate fouling, historical ways to inhibit it, and current approaches to the problem, as well as the results of the laboratory testing of naphthenate inhibitors and solvents. The process of the naphthenate creation is as follows. When oil exhibits a high TAN (total acid number) and high content of salty water, naphthenate deposits can emerge via the reaction of naphthenic acids and metal salts (mostly calcium ones). Naphthenates are partially insoluble in water, and they usually float below the oil/water interface. The standard methods of naphthenate inhibition involve lowering the pH of the production water, which can result in serious problems, especially related to corrosion. This study addresses experiments conducted in the laboratory in Poland and on oil rigs in Angola and is based on contemporary knowledge and standards. The objective of this paper was to investigate the most suitable naphthenate inhibitors and solvents, as well as to undertake bottle tests of naphthenate inhibitors with a focus on the main indicators (water clarity, quality of separation surface, and clarity of oil). The use of citric and formic acids in this paper is a novelty, and it is compared with the results obtained with the more commonly used acetic acid, hydrochloric acid, and ABS acid. It was proven that formic acid can effectively inhibit and dissolve naphthenic deposits (99% efficiency of inhibition and 100% efficiency of dissolution). It was found that some acids used in naphthenate inhibition create more deposits than were originally present. Formic acid and ABS acid yielded significantly better results than other types. It is also here hypothesized that there are substances other than acids that can effectively remove naphthenate deposits, and the other novelty of this study is in the use of mutual solvents in the removal of naphthenate salts. Another important outcome is the finding that not only acids but also mutual solvents (EGMBE and isopropyl alcohol) can effectively remove naphthenate deposits. The test results show that formic acid dissolved all of the naphthenates, while citric acid had 97% efficacy, isopropyl alcohol had 95% efficacy, and EGMBE showed 94% efficacy. The impacts of commercial naphthenate inhibitors on the bottle test results and interfacial tension measurements were also investigated. It was shown that commercial naphthenate inhibitors can decrease the interfacial tension between oil and water by more than 30% when used at dosages of 400 ppm. [ABSTRACT FROM AUTHOR]

A capillary electrophoresis‐mass spectrometry method was used to analyze naphthenic acids in produced water samples. It was possible to detect cyclopentanecarboxylic, benzoic, cyclohexanebutyric, 1‐naphthoic, decanoic, 3,5‐dimethyladamantane‐1‐carboxylic, 9‐anthracenecarboxylic, and pentadecanoic acids within ca. 13 min using a buffer composed of 40 mmol/L ammonium hydroxide, 32 mmol/L acetic acid and 20% v/v isopropyl alcohol, pH 8.6. The proposed method showed good repeatability, with relative standard deviation (RSD) values of 6.6% for the sum of the peak areas and less than 2% for the analysis time. In the interday analysis, the RSD values for the sum of the peak areas and migration time were 10.3% and 10%, respectively. The developed method demonstrated linear behavior in the concentration range between 5 and 50 mg/L for benzoic, decanoic, 3,5‐dimethyladamantane‐1‐carboxylic and 9‐anthracenecarboxylic acids, and between 10 and 50 mg/L for cyclopentanecarboxylic, cyclohexanebutyric, 1‐ naphthoic, and pentadecanoic acids. The detection limits values ranged from 0.31 to 1.64 mg/L. Six produced water samples were analyzed and it was possible to identify and quantify cyclopentanecarboxylic, benzoic, cyclohexanebutyric, and decanoic acids. The concentrations varied between 4.8 and 98.9 mg/L, proving effective in the application of complex samples. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Multiple studies have focused on the effect of long-term weathering processes on oils after spill events, without considering the chemical compositional changes occurring shortly after the release of oil into the environment. Therefore, the present study provides a broad chemical characterization for understanding of the changes occurring in the chemical compositions of intermediate (°API = 27.0) and heavy (°API = 20.9) oils from the Sergipe-Alagoas basin submitted to two simulated situations, one under marine conditions and the other in a riverine environment. Samples of the oils were collected during the first 72 h of contact with the simulated environments, followed by evaluation of their chemical compositions. SARA fractionation was used to isolate the resins, which were characterized at the molecular level by UHRMS. The evaporation process was highlighted, with the GC-FID chromatographic profiles showing the disappearance of compounds from n-C10 until n-C16, as well as changes in the weathering indexes and pristane + n-C17/phytane + n-C18 ratios for the crude oils submitted to the riverine conditions. Analysis of the resins fraction showed that basic polar compounds underwent little or no alterations during the early stages of weathering. The marine environment was shown to be much less oxidative than the riverine environment. For both environments, a feature highlighted was an increase of acidic oxygenated compounds with the increase of weathering, especially for the crude oil with °API = 27.0. [ABSTRACT FROM AUTHOR]

The ethylenediamine-N,N′-disuccinic acid (EDDS) was utilized to form Fe-EDDS complex to activate peroxymonosulfate (PMS) in the electrochemical (EC) co-catalytic system for effective oxidation of naphthenic acids (NAs) under neutral pH conditions. 1-adamantanecarboxylic acid (ACA) was used as a model compound to represent NAs, which are persistent pollutants that are abundantly present in oil and gas field wastewater. The ACA degradation rate was significantly enhanced in the EC/PMS/Fe(III)-EDDS system (96.6%) compared to that of the EC/PMS/Fe(III) system (65.4%). The addition of EDDS led to the formation of a stable complex of Fe-EDDS under neutral pH conditions, which effectively promoted the redox cycle of Fe(III)-EDDS/Fe(II)-EDDS to activate PMS to generate oxidative species for ACA degradation. The results of quenching and chemical probe experiments, as well as electron paramagnetic resonance (EPR) analysis, identified significant contributions of •OH, 1O2, and SO4•− in the removal of ACA. The ACA degradation pathways were revealed based on the results of high resolution mass spectrometry analysis and calculation of the Fukui index. The presence of anions, such as NO3−, Cl−, and HCO3−, as well as humic acids, induced nonsignificant influence on the ACA degradation, indicating the robustness of the current system for applications in authentic scenarios. Overall results indicated the EC/PMS/Fe(III)-EDDS system is a promising strategy for the practical treatment of NAs in oil and gas field wastewater. [ABSTRACT FROM AUTHOR]

Copyright of Corrosion & Protection in Petrochemical Industry is the property of Corrosion & Protection in Petrochemical Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Petroleum coke‐derived activated cokes were prepared and used for the adsorptive removal of a single‐ring naphthenic acid (NA) from synthetic oil sands process affected water (OSPW). CO2 activation produced carbon with a larger mesopore volume fraction (0.67) than steam activation (0.25). Interestingly, prolonging the activation time of CO2 from 6 to 9 h led to a simultaneous increase in specific surface area (276–405 m2/g) and mesopore volume (0.51–0.67). Furthermore, a positive relationship was found between the pseudo‐second‐order kinetic rate constant and the mesoporous volume of the activated coke. This suggests both the importance of pore size on kinetics and the fact that physical activation with a reagent such as CO2 may be better suited than chemical activation due to its ability to create mesopores. Although enlarging the pores and accelerating the adsorption rate, post‐oxidation had detrimental effects on adsorption capacity, resulting in a decrease in equilibrium adsorbed amount from 115 to 34 mg/g, a 70% decrease, when post‐oxidized with O2, due to the negative charge of oxygen‐containing functional groups. On the other hand, the measured adsorption capacity increased by over 60% when activated coke was treated with ammonia, a result of the positively charged nitrogen‐containing surface groups. Finally, in real OSPW, the activated coke had a much lower capacity for total acid‐extractable organics than for the model NA. Therefore, activated petroleum coke may not be the best choice for treating raw tailings pond water and may be better suited for polishing. [ABSTRACT FROM AUTHOR]

Naphthenic acids, NAs, are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters, OSPW. Using activated carbon adsorbents are an attractive option given their low cost of fabrication and implementation. A deeper evaluation of the effect NA structural differences have on uptake affinity is warranted. Here we provide an in-depth exploration of NA adsorption including many more model NA species than have been assessed previously with evaluation of adsorption kinetics and isotherms at the relevant alkaline pH of OSPW using several different carbon adsorbents with pH buffering to simulate the behaviour of real OSPW. Uptake for the NA varied considerably regardless of the activated carbon used, ranging from 350 mg/g to near zero highlighting recalcitrant NAs. The equilibrium data was explored to identify structural features of these species and key physiochemical properties that influence adsorption. We found that certain NA will be resistant to adsorption when hydrophobic adsorbents are used. Adsorption isotherm modelling helped explore interactions occurring at the interface between NA and adsorbent surfaces. We identified the importance of NA hydrophobicity for activated carbon uptake. Evidence is also presented that indicates favorable hydrogen bonding between certain NA and surface site hydroxyl groups, demonstrating the importance of adsorbent surface functionality for NA uptake. This research highlights the challenges associated with removing NAs from OSPW through adsorption and also identifies how adsorbent surface chemistry modification can be used to increase the removal efficiency of recalcitrant NA species. [ABSTRACT FROM AUTHOR]

The focus of this work is to investigate the interfacial rheology of a fatty acid, stearic acid (SA), and a commercial mixture of naphthenic acid (CMNA), capable of mimicking the real naphthenic acids (NAs) found in crude oils. We aim to propose an acidic molecular interaction at the water-oil interface under different aqueous phase compositions, by changing its electrolyte content, adding monovalent salts (NaCl and KCl), divalent salts (CaCl2 and BaCl2), and, increasing the pH of the water subphase. The viscoelastic properties are measured using the pendant drop dilation and contraction technique known as drop shape analysis (DSA). Furthermore, we prepare water-in-oil emulsions to correlate interfacial properties with their stability. The experimental results reveal that SAs can form rigid and viscoelastic films upon low sinusoidal deformations and higher cation content. We find that the emulsions containing SAs are more stable in high pH environments, where we observe the presence of birefringence features in SA laden droplets. This outcome evidences the interplay between emulsion stability and mechanical resistance at hydrocarbon-high pH interfaces loaded with SAs. [ABSTRACT FROM AUTHOR]

In order to reduce dependence on imported crude oil and to progress towards self-reliance in energy, it is desirable to develop processes for producing fuels from renewable resources like bio-based feedstocks. However, it is observed that use of biocrude in a Petroleum Refinery is limited by extensive corrosion of Refinery equipment due to the presence of Naphthenic acids at high levels to the tune of > 90 mg KOH/gm. As part of the study, detailed study on biocrude is carried out and found that 46 vol% fraction of biocrude is having boiling range of 643.15°K–753.15°K and has a high tendency of coke formation. To investigate the behaviour of thermal cracking and extract kinetic parameters, different model-free techniques such as the Friedman, Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose method are employed from the Thermogravimetric and Differential Scanning Calorimetry analysis. The experimental results showed that activation energy obtained from isoconversional methods showed good agreement, but Friedman method was considered to be the best among the model-free methods to evaluate kinetic parameters of highly stable materials like biocrude and VR with activation energy ranging from 53 to 92 kJ mol−1 and 159 to 234 kJ mol−1, respectively, for extent of conversion from 10 to 50 mass%. A thermal cracking study in laboratory scale Micro-coker unit was also carried out by co-processing the biocrude with vacuum residue, to study the feasibility of co-processing in Delayed Coker Unit. Thermal decomposition of biocrude also showed considerable reduction in the Total Acid Number from 90 to 18 mg KOH/gm. [ABSTRACT FROM AUTHOR]

Large volumes of oil sands process-affected waters (OSPW) result from heavy oil extraction in Alberta, Canada. Currently, a toxic legacy of ca. 500 Mm3 is stored in tailings ponds under a zero-discharge policy. OSPW is a complex mixture of suspended and dissolved materials including a wide range of inorganic and organic contaminants. Classically defined naphthenic acids (NAs; CnH2n+ZO2) are one of the primary toxic fractions in OSPW and have therefore been the subject of considerable research interest. Most studies employ considerable sample cleanup followed by liquid chromatography and/or high-resolution mass spectrometry (HRMS) for the characterization of these complex mixtures. However, these strategies can be time- and cost-intensive, limiting the scope of research and adoption for regulatory purposes. Condensed phase membrane introduction mass spectrometry (CP-MIMS) is emerging as a "fit-for-purpose" approach for the analysis of NAs. This technique directly interfaces the mass spectrometer with an aqueous sample using a hydrophobic semi-permeable membrane, requiring only pH adjustment to convert NAs to a membrane-permeable form. Here, we examine the perm-selectivity of classical NAs (O2) relative to their more oxidized counterparts (O3–O7) and heteroatomic (N, S) species collectively termed naphthenic acid fraction compounds (NAFCs). The investigation of 14 model compounds revealed that classically defined NAs are greater than 50-fold more membrane permeable than their oxidized/heteroatomic analogs. HRMS analysis of real OSPW extracts with and without membrane clean-up further supported selectivity towards the toxic O2 class of NAs, with >85% of the overall signal intensity attributable to O2 NAs in the membrane permeate despite as little as 34.7 ± 0.6% O2 NAs observed in the directly infused mixture. The information collected with HRMS is leveraged to refine our method for analysis of NAs at unit mass resolution. This new method is applied to 28 archived real-world samples containing NAs/NAFCs from constructed wetlands, OSPW, and environmental monitoring campaigns. Concentrations ranged from 0–25 mg/L O2 NAs and the results measured by CP-MIMS (unit mass) and SPE-HRMS (Orbitrap) showed good agreement (slope = 0.80; R2 = 0.76). [ABSTRACT FROM AUTHOR]

Resins have enormous potential in the removal of naphthenic acids (NAs) from transformer oil due to their rich porosity and high mechanical and diversified functionality, whereas their poor adsorption capacity limits application. In this work, the polystyrene–diethylamine resin (PS−DEA−x) was prepared by grafting diethylamine (DEA) onto chloromethylated polystyrene (PS−Cl) resin to efficiently adsorb cyclopentane carboxylic acid from transformer oil for the first time. The characterization analysis results indicated that amine contents were significantly enhanced with the increase in DEA. Particularly, resin with a molar ratio of 1:5 depending on chloromethyl to DEA (PS−DEA−5) exhibited the highest amine contents and efficient adsorption of cyclopentane carboxylic acid (static adsorption capacity up to 110.0 mg/g), which was about 5 times higher than that of the pristine PS−Cl. The thermodynamic and kinetic studies showed that the adsorption behaviors could be well fitted to the Langmuir isotherm equation and pseudo−second−order rate equation. Moreover, it was found that 1 g of the PS−DEA−5 can decontaminate about 760 mL transformer oil to meet reuse standards by a continuous stream, indicating its potential application in industry. [ABSTRACT FROM AUTHOR]

Naphthenic acid (NA) is a toxic pollutant with potential threat to human health. However, NA transformations in marine environments are still unclear. In this study, the characteristics and pathways of cyclohexanecarboxylic acid (CHCA) biodegradation were explored in the presence of nitrate. The results showed that CHCA was completely degraded with pseudo-first-order kinetic reaction under aerobic and anaerobic conditions, accompanied by nitrate removal rates exceeding 70%, which was positively correlated with CHCA degradation (P < 0.05). In the proposed CHCA degradation pathways, cyclohexane is dehydrogenated to form cyclohexene, followed by ring-opening by dioxygenase to generate fatty acid under aerobic conditions or cleavage of cyclohexene through β-oxidation under anaerobic conditions. Whole genome analysis indicated that nitrate was removed via assimilation and dissimilation pathways under aerobic conditions and via denitrification pathway under anaerobic conditions. These results provide a basis for alleviating combined pollution of NA and nitrate in marine environments with frequent anthropogenic activities. [ABSTRACT FROM AUTHOR]

Saddle Diesel is a diesel engine plant in a local city in northeast China, which is already the special designation. In this paper, a new polyhydroxy polyacid macromolecule called citric acid-1,4-butanediol-citric acid-cycloalkanic acid-tetradecyl alcohol (CTC-NT) with 1,4-butanediol as the core was designed and synthesized via an "ester-ester" copolymerization process using 1,4-butanediol and citric acid as the raw materials and then grafted sequentially with naphthenic acid and tetradecanol containing functionalized groups. The structures of the synthesized compounds were characterized by nuclear magnetic resonance and infrared spectroscopy, and the results showed that the synthetic products were consistent with the designed molecular structure. The use of the prepared CTC-NT in saddle oil light diesel was studied. The results showed that the filtration improvements of the synthesized multibranched macromolecule CTC-NT were better than those of other additives for the same oil, and the cold filter point was reduced by up to 13°C when the dosage was 900 μg/g. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The occurrence of naphthenic acids (NAs) in crude oil and its fractional distillation cuts have been widely recognized to be a natural phenomenon. Despite this, they continue to generate wide interest due to the ecological and industrial concerns emanating from their toxicity and corrosion effects. In this study, refined petroleum products were assayed for their physical and chemical properties as well as associated NAs. The NAs were removed using the solvent extraction method and characterized using the gas chromatography–mass spectrometry technique. The total acid number and densities of the gasoline, kerosene, diesel, and lubricating oil samples were 9.37, 5.44, 12.45, and 5.72 mg KOH/g, and 0.63, 0.66, 0.72, and 0.75 g/cm3, respectively. In consonance with other estimated properties, it was observed that lubricating oil was the heaviest of the studied oil samples while gasoline was the lightest. This was attributed to the presence of more aromatic compounds in the lubricating oil sample. Although there were slight variations in the profiles of NAs from sample to sample, they generally contained degree of unsaturation (z), z = 0 to z = − 16 compounds with a high predominance of aliphatic naphthenic acid types. The carbon numbers of the NAs detected in the oil samples ranged from 8 to 15. The estimated carbon preference index (CPI) indicated that the lubricating oil sample may have emanated from biogenic contribution (CPI > > 1) while the other samples likely emanated from petrogenic sources (CPI < 1). The even–odd carbon ratio (E/O) indicated that there is no carbon preference among the studied oil samples. [ABSTRACT FROM AUTHOR]

This paper represents a detailed techno-economic analysis of a typical commercial-scale catalytic decarboxylation process of naphthenic acids over HZSM-5 zeolite. Simulation of the process has been performed in ASPEN Plus®. The performance of the modeled unit was compared to experimental results data from a similar plant. Two models were developed for the proposed industrial plant based on continuous flow reactors; the first is based on a fluidized bed reactor, and it was modeled as a continuous stirred tank reactor (CSTR) unit, and the second is a semi-regenerative process that consists of three fixed-bed reactors with intermediate preheaters and are modeled as three plug flow reactors (PFR). The outcome of the economic analysis of the two proposed commercial scale reactors of a decarboxylation process of a capacity of 11,000 bbl/day showed that the CAPEX, including the total equipment cost for the fluidized bed reactor plant and semi-regenerative process plant, was $44,319,362 and $4,447,919, respectively. The annual operating cost for the fluidized bed plant and semi-regenerative process plant is 45,269,180 $/year and 1,771,839 $/year, respectively. Our results demonstrated that catalytic decarboxylation over HZSM-5 zeolite is economically feasible using a semi-regenerative process, and is a promising method for removing naphthenic acid. The insight obtained from this work can be used as a basis for more comprehensive future financial and risk modeling of the process. The cost estimated in this work was compared to the Khartoum refinery cost for the naphthenic acid corrosion mitigation system, with a saving of $29,459,528. [ABSTRACT FROM AUTHOR]

This research proposes a new method that fuses data from the field and lab-based optical measures coupled with machine learning algorithms to quantify the concentrations of toxic contaminants found in fuels and oil sands process-affected water. Selected pairs of excitation/emission intensities at key wavelengths are inputs to an augmentation neural network (NN), trained using lab-based measurements, that generates synthetic high-resolution spectra. Then, an image processing NN is used to estimate the contaminant concentrations from the spectra generated from a few key wavelengths. The presented approach is tested using naphthenic acids, phenol, fluoranthene and pyrene spiked into natural waters. The spills or loss of containment of these contaminants represent a significant risk to the environment and public health, requiring accurate and rapid detection methods to protect the surrounding aquatic environment. Results were compared with models based on only the corresponding peak intensities of each contaminant and with an image processing NN using the original spectra. Naphthenic acids, fluoranthene and pyrene were easy to detect by all methods; however, performance for more challenging signals to identify, such as phenol, was optimized by the proposed method (peak picking with mean absolute error (MAE) of 30.48 µg/L, generated excitation-emission matrix with MAE of 8.30 µg/L). Results suggested that data fusion and machine learning techniques can improve the detection of contaminants in the aquatic environment at environmentally relevant concentrations. [ABSTRACT FROM AUTHOR]

Naphthenic acids are a group of polar organic carboxylic acids that are present in crude oil naturally. They are cycloaliphatic carboxylic acids which have 10 to 16 carbons, which gained importance since the early twentieth century because of corrosion in oil refineries. Moreover, they are the most important environmental pollutants caused by oil extraction from oil sand reserves. Heavy crude oils which have high concentration of naphthenic acids are usually considered as poor-quality oil and sold at a lower price. Often, the high concentration of naphthenic acids in crude oil reduces the life of the equipment which are used in the exploration and refining process because of corrosion. Hence, researchers are increasingly interested in the chemical properties of naphthenic acids and the acidic components of the crude oils. The most popular methods for the identification and analysis of naphthenic acids are liquid and gas chromatography (GC), liquid-liquid extraction, Fourier transform infrared spectroscopy (FTIR), and solid-phase extraction (SPE). Naphthenic acids are the most important environmental pollutants caused by oil extraction from oil sand reserves. Previous studies have revealed that naphthenic acids can be absorbed by fish, but their distribution in different tissues of fish has not been specified. Experimental samples showed the highest toxicity to fish, while there was less toxicity to invertebrates and algae. Moreover, naphthenates have various industrial utilizations; they are used in synthetic detergents, corrosion inhibitors, lubricants, fuel and oil additives, wood preservatives, insecticides, fungicides, pesticides, wetting agents, napalm thickening agents, and oil desiccants that are utilized in painting and treating wood surfaces. [ABSTRACT FROM AUTHOR]

Oil sands process-affected water (OSPW) contains a diverse mixture of inorganic and organic compounds. Naphthenic acids (NAs) are a subset of the organic naphthenic acid fraction compounds (NAFCs) and are a major contributor of toxicity to aquatic species. Thousands of unique chemical formulae are measured in OSPW by accurate mass spectrometry and high-resolution mass spectrometry (MS) analysis of NAFCs. As no commercial reference standard is available to cover the range of compounds present in NAFCs, quantitation may best be referred to as “semi-quantitative” and is based on the responses of one or more model compounds. Negative mode electrospray ionization (ESI-) is often used for NAFC measurement but is prone to ion suppression in complex matrices. This review discusses aspects of off-line sample preparation techniques and liquid chromatography (LC) separations to help reduce ion suppression effects and improve the comparability of both inter-laboratory and intra-laboratory results. Alternative approaches to the analytical parameters discussed include extraction solvents, salt content of samples, extraction pH, off-line sample cleanup, on-line LC chromatography, calibration standards, MS ionization modes, NAFC compound classes, MS mass resolution, and the use of internal standards.

Naphthenic acids (NAs) are typical contaminants in heavily crude oil. Benzo[a]pyrene (B[a]P) is also a component of crude oil, but their combined effects have not been systematically explored. In this study, zebrafish (Danio rerio) were used as the test organisms, and behavioral indicators and enzyme activities were used as toxicity indicators. Combined with the effects of environmental concentrations, the toxic effects of low concentrations of commercially available NAs (0.5 mg/LNA) and benzo[a]pyrene (0.8 μg/LBaP) at single and compound exposures (0.5 mg/LNA and 0.8 μg/LBaP) were assayed in zebrafish, and transcriptome sequencing technology was used to explore the molecular mechanism of the two compounds affecting zebrafish from the molecular biology level. Sensitive molecular markers that could indicate the presence of contaminants were screened. The results showed that (1) zebrafish in the NA and BaP exposure groups exhibited increased locomotor behavior, and the mixed exposure group exhibited inhibition of locomotor behavior. Oxidative stress biomarkers showed increased activity under single exposure and decreased activity under the mixed exposure. (2) NA stress led to changes in the activity of transporters and the intensity of energy metabolism; BaP directly stimulates the pathway of actin production. When the two compounds are combined, the excitability of neurons in the central nervous system is decreased, and the actin-related genes are down-regulated. (3) After BaP and Mix treatments, genes were enriched in the cytokine-receptor interaction and actin signal pathway, while NA increased the toxic effect on the mixed treatment group. In general, the interaction between NA and BaP has a synergistic effect on the transcription of zebrafish nerve and motor behavior-related genes, resulting in increased toxicity under combined exposure. The changes in expression of various zebrafish genes are manifested in the changes in the normal movement behavior of zebrafish and the intensification of oxidative stress in the apparent behavior and physiological indicators. Capsule abstract: We investigated the toxicity and genetic alterations caused by NA, B[a]P, and their mixtures in zebrafish in an aquatic environment using transcriptome sequencing technology and comprehensive behavioral analysis. These changes involved energy metabolism, the generation of muscle cells, and the nervous system.

This study reports the adsorption of the naphthenic acids (NA) presents in an aviation kerosene (AVK) model mix using adsorbents prepared from peanut shell (PS). Both carbonization and the CO 2 activation of the PS favored the adsorptive process. In the factorial design, the activated carbon prepared presented the highest adsorptive capacity for the lowest levels of the variables studied (<0.09 mm and without agitation). The adsorption equilibrium after 360 min, and the process is not only controlled by the intraparticle diffusion step. The adsorption isotherm was best fitted to Langmuir model with a maximum adsorbed amount of 884 mg g−1, whose heat of adsorption indicated that the process was of the physisorption. In the continuous adsorption study, it was verified that the increase of the flow and the concentration of NA decreased the rupture time. The breakthrough time and adsorptive capacity were reduced at each adsorption/desorption cycle. Given the shortage of works on this topic in literature, this study contributes with new findings that describe naphthenic acid adsorption in AVK. [Display omitted] • Characterization of adsorbents prepared for naphthenic acid adsorption. • Adsorption of naphthenic acid in an aviation kerosene model mixture. • Parameters evaluation using factorial design for the adsorptive process. • Model application to predict the naphthenic acid adsorption process. • Study of continuous adsorption of naphthenic acid in a fixed-bed column. [ABSTRACT FROM AUTHOR]

Calcium in crude oil can cause equipment fouling and catalyst deactivation, hence the speciation of calcium in crude oil is of interest to the petroleum industry. This review summarizes various forms of calcium found in crude oils, includes inorganic calcium-containing compounds and organic calcium-containing compounds. The progress in characterization method and molecular composition of organic insoluble calcium-containing compounds are highlighted. The organic calcium compounds are mainly calcium naphthenate, therefore the challenge for the characterization of calcium compounds is the molecular characterization of the hydrolyzed naphthenic acids. With the advances in high-resolution mass spectrometry, the complex mixture of naphthenic acids can be characterized at the molecular level. Large molecular tetra carboxylic acids, which are derived from bacterial/eukaryotic lipids and/or archaeal membranes, are found the major component to form hard deposit with calcium ions. Naphthenic acids are considered as a key controlling factor for the calcium content in petroleum, however, the mechanism of interaction between calcium and naphthenic acid molecules is still not well understood. [ABSTRACT FROM AUTHOR]

The extraction of bitumen from surface mining in the Athabasca Oil Sands Region (AOSR) produces large quantities of oil sands process‐affected water (OSPW) that needs to be stored in settling basins near extraction sites. Chemical constituents of OSPW are known to impair bone health in some organisms, which can lead to increased fracture risk and lower reproductive fitness. Naphthenic acid fraction components (NAFCs) are thought to be among the most toxic class of compounds in OSPW; however, the effect of NAFCs on osteoblast development is largely unknown. In this study, we demonstrate that NAFCs from OSPW inhibit osteoblast differentiation and deposition of extracellular matrix, which is required for bone formation. Extracellular matrix deposition was inhibited in osteoblasts exposed to 12.5–125 mg/L of NAFC for 21 days. We also show that components within NAFCs inhibit the expression of gene markers of osteoblast differentiation and function, namely, alkaline phosphatase (Alp), osteocalcin, and collagen type 1 alpha 1 (Col1a1). These effects were partially mediated by the induction of glucocorticoid receptor (GR) activity; NAFC induces the expression of the GR activity marker genes Sgk1 (12.5 mg/L) and p85a (125 mg/L) and inhibits GR protein (125 mg/L) and Opg RNA (12.5 mg/L) expression. This study provides evidence that NAFC concentrations of 12.5 mg/L and above can directly act on osteoblasts to inhibit bone formation and suggests that NAFCs contain components that can act as GR agonists, which may have further endocrine disrupting effects on exposed wildlife. Surface mining in the Athabasca Oil Sands Region (AOSR) produces large quantities of oil sands process‐affected water (OSPW), constituents of which are known to impair bone health in some organisms. Naphthenic acid fraction components (NAFCs) are thought to be responsible for most of the toxic effect of OSPW, but their effects on bone are unknown. In this study, we demonstrate that NAFCs extracted from the AOSR inhibit osteoblast differentiation and may act via the glucocorticoid receptor. [ABSTRACT FROM AUTHOR]

The biocidal activity of the aminomethyl derivatives of 2-mercaptobenzoxazole synthesized by us and being of interest as potential antimicrobial additives to petroleum products and cutting fluids, was studied. The aminomethylation reaction proceeded with the participation of methylene-bis-amines. As a result, the appropriate N-substituted benzoxazolin-2-thiones were obtained. Their structure was proved by NMR 1H. Due to the poor solubility of the synthesized compounds in petroleum products, their salts with petroleum naphthenic acid were obtained for microbiological testing. The results of tests in lubricating oil M-8 show that the naphthenic salts of the synthesized compounds exhibit biocidal activity and their fungicidal properties are higher than bactericidal ones. The petroleum naphthenic acid used in the test in its pure form in the composition of the M-8 lubricating oil is not biostable and is affected by microorganisms. N-piperidinomethylbenzoxazolin-2-thione in the composition of the coolant proved to be a biocide, and its bactericidal properties are higher than fungicidal ones. The results of a microbiological study of an aqueous solution of this compound showed high bactericidal properties in the absence of effectiveness against mold fungi. [ABSTRACT FROM AUTHOR]

Interfacial tension (IFT) is important in developing oilfield exploration and production strategies, enhanced oil recovery, and oil-water separation. Tests using reservoir simulators such as Eclipse show that the selected IFT has significant impact on prediction of water coning and production. In petroleum engineering, IFT is often assessed through correlations based on bulk properties excluding the impact of surface-active components. Crude oil contains many different types of surface-active components among which naphthenic acids and asphaltene-like molecules play an important role in IFT between oil and water. It is desirable to be able to link the IFT to the concentration of the natural surfactants to predict variations across a petroleum reservoir. To develop this relation, the equilibrium IFT was investigated in various systems of varying acid content. As expected, naphthenic acids reduce IFT of oil and water significantly. The IFT reduction is however dependent on the structure and composition of naphthenic acids as well as the nature of the solvent. To include the natural surfactancy in the model a Gibbs-Langmuir approach is used to describe the impact of naphthenic acids content in crude oil on IFT. This is compared to two models currently used to estimate IFT in the petroleum industry. The current models are not equipped to capture the role of natural surfactants and hence results may lead to erroneous predictions on crude oil production. We therefore propose an approach where bulk properties that estimate the bulk IFT is used in combination of a term based on the Gibbs-Langmuir model to capture the perturbation by the naphthenic acids to yield more accurate estimates of IFT. This require fitting to at least two experimental points to yield accurate results. [ABSTRACT FROM AUTHOR]

Naphthenic Acids (NA) are important oil extraction subproducts. These chemical species are one of the leading causes of marine pollution and duct corrosion. For this reason, understanding the behavior of NAs in different saline conditions is one of the challenges in the oil industry. In this work, we simulated several naphthenic acid species and their mixtures, employing density functional theory calculations with the MST-IEFPCM continuum solvation model, to obtain the octanol–water partition coefficients, together with microsecond classical molecular dynamics. The latter consisted of pure water, low-salinity, and high-salinity environment simulations, to assess the stability of NAs aggregates and their sizes. The quantum calculations have shown that the longer chain acids are more hydrophobic, and the classical simulations corroborated: that the longer the chain, the higher the order of the aggregate. In addition, we observed that larger aggregates are stable at higher salinities for all the studied NAs. This can be one factor in the observed low-salinity-enhanced oil recovery, which is a complex phenomenon. The simulations also show that stabilizing the aggregates induced by the salinity involves a direct interplay of Na+ cations with the carboxylic groups of the NAs inside the aggregates. In some cases, the ion/NA organization forms a membrane-like circular structural arrangement, especially for longer chain NAs. [ABSTRACT FROM AUTHOR]

In this experiment, the effects of the application of naphthenic acids (NAs) on apricots in the early fruit development phases on fruit morphological properties, composition and postharvest properties were investigated. Two concentrations of NAs (1 mg/L and 3 mg/L) were applied at two development stages in the apricot cultivar NS-4. The application of NAs at the beginning of the petal fall development phase resulted in the reduction of fruit dimensions at harvest while the application 7 days later increased fruit dimensions. Although there were no significant differences in the most investigated characteristics between fruits treated with NAs and untreated control at harvest or in the postharvest period during 20 days of cold storage (1 ± 1 °C, RD 80%) and particularly after 3 days of shelf life at room temperature. However, compared to the untreated control, apricots treated with NAs were characterized by higher total soluble solids content accompanied by higher fructose content, and lower titratable acidity accompanied by higher succinic acid content. Apricots treated with NAs showed trends towards improved sensory properties: sweeter and less sour taste, with more expressed apricot aroma accompanied with decreased gumminess and crispiness and more intensive tissue breakdown, but without expressed notes of inappropriate taste.

• The effects of carbamide on smart water flooding were investigated. • The presence of carbamide decreased the micro-dispersion formation at the oil/brine interface. • More amounts of naphthenic acids partitioned and dissociated in the brine at low carbamide concentrations. • Tuning SO 4 2− concentration in carbamide/SW solution resulted in more oil extraction. • The carbonate surface became more water-wet, and interfacial tension experienced more reduction in the presence of carbamide. This study explores the impact of carbamide at different concentrations on smart water flooding into carbonate reservoirs. The aim is to find out how the presence of carbamide can influence the mechanisms of smart water flooding at rock/brine and oil/brine interfaces. The results revealed that interfacial tension (IFT) reduces as the carbamide concentration increases in the brine. Indeed, the carbamide decomposes at elevated temperatures, and in-situ surface active agents are formed at the oil/brine interface, reducing IFT values. Further, while the dilution of seawater (SW) is unable to change the oil-wet wettability, the carbamide can make the carbonate surface more water-wet by elevating its concentration. Additionally, the corresponding mechanisms of this wettability alteration would be the formation of in-situ surface active agents, electrostatic interactions, and hydrogen bond formation at the rock/brine interface. Among K+, Mg2+, and SO 4 2−, adjusting the concentration of sulfate ions in SW leads to greater IFT reduction in the presence of carbamide. In addition, the contact angle is further reduced as K+ concentration is doubled in the solution; however, this reduction is not significant as compared to Mg2+ and SO 4 2−. Also, ten-times diluted seawater (10dsw) produced more micro-dispersions in the oil phase. Nevertheless, the presence of carbamide in 10dws had a negative impact on the micro-dispersion formation, which is one of the driving mechanisms of smart water flooding. At a lower carbamide concentration (1000 ppm), more carboxylic acids and ketones were observed in the brines due to the partitioning and dissociation of naphthenic acids. On the contrary, as carbamide concentration increased to 10000 ppm, amounts of carboxylic acids declined due to the production of in-situ surface active agents at the oil/brine interface. Bottle test experiments indicated that water-in-oil emulsions were generated in the presence of carbamide. The mean water droplet size grew as carbamide concentration rose to 25000 ppm; nonetheless, further increase in the carbamide concentration resulted in mean droplet size reduction. Calcite-coated micromodel flooding illustrated that oil recovery of 21.6, 24, and 27.2 % was found at carbamide concentrations of 1000, 10000, and 100000 ppm. Furthermore, a three-time increase in SO 4 2− concentration at 10000 ppm of carbamide offered a better performance in boosting oil recovery than tuning K+ and Mg2+ concentrations in carbamide/SW solutions. The findings of this study underscore the promising prospects of leveraging carbamide to enhance the efficacy of smart water solutions in carbonate reservoirs, particularly regarding IFT modification, wettability alteration, and oil recovery enhancement. [ABSTRACT FROM AUTHOR]

• The EC/PMS/Fe(III)-EDTA system was tested under a pH range of 3–9. • Fe(II)-EDTA complex maintains high reaction rates to degrade ACA at neutral pH. • •OH, 1O 2 , SO 4 •− and Fe(IV) are the dominant reactive species in the system. • The addition of EDTA established a new pathway for producing 1O 2 in the system. • ACA degradation pathways and byproducts were revealed based on mass spectra. In this work, ethylene diamine tetraacetic acid (EDTA) was applied as a chelating agent to stabilize Fe(III)/Fe(II) cycle to effectively activate peroxymonosulfate (PMS) in an electrochemical (EC) co-catalytic system for elimination of naphthenic acids (NAs) under neutral pH condition. 1-Adamantanecarboxylic acid (ACA) was applied as the model compound for NAs that are persistent contaminants in petroleum industrial wastewater. In the PMS/EC/Fe(III)-EDTA system, complete removal of ACA has been achieved in 20-min reaction under neutral pH condition. Degradation mechanisms were investigated via electron paramagnetic resonance (EPR) analysis, probe experiments and quenching experiments to reveal the reactive species •OH, SO 4 •− and 1O 2 for ACA removal, the production of which have been significantly facilitated by the introduction of EDTA complex. A new pathway has been found for the production of 1O 2 via several intermediates including hydrogen peroxide and superoxide radicals. Density functional theory (DFT) calculations and mass spectrometry analysis were applied to predict ACA degradation pathways and byproducts. Decarboxylation, hydroxyl substitution and carbonyl substitution byproducts of ACA were detected. The PMS/EC/Fe(III)-EDTA system suffered nonimportant influence at the presence of humic acid, H 2 PO 4 -, HCO 3 –, NO 3 – and Cl- for ACA removal. Overall results demonstrate the effectiveness and reliability of the PMS/EC/Fe(III)-EDTA system for efficient removal of NAs in petroleum wastewater in natural environment under neutral pH condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • DOC desorption was driven by pore diffusion, with minimal effect from film diffusion. • High stability of DOC and NAs in PASS-treated FFT. • Desorption was minimally influenced by temperature and water conductivity. • Cations (K+, Ca2+) significantly inhibited desorption; anions had little effect. • Geochemical stability of PASS-treated FFT endorsed its use in FFT management. Rate and mechanism of organic compounds desorption from fluid fine tailings (FFT) deposits into the capped water are crucial to understand the geochemical stability of end pit lakes. Specifically, the intricate interplay between electrolyte concentrations and seasonal fluctuations along with their impact on the persistence of organic constituents remains insufficiently elucidated. This study utilized PASS-treated FFT (i.e., permanent aquatic structure storage) from Lake Miwasin to address these questions. Experiments were conducted to investigate the desorption of organics from FFT into lake water under different conditions, including FFT dosage, contact time, temperature, and ionic strength. Results revealed that higher FFT dosage and lake water organic matter led to increased desorption of dissolved organic carbon (DOC), while temperature and conductivity of the lake water had minimal effects. The presence of electrolytes regulated the equilibrium desorption capacity of DOC, with cations (K+ and Ca2+) significantly affecting the desorption process from negatively charged treated FFT particles. Temkin isotherms displayed that desorption dynamics followed physically favorable patterns whereas the Intraparticle diffusion kinetic model suggested the equilibrium desorption capacity of DOC as 0.65 mg/g of PASS-treated FFT. A small percentage (5.82 %) of the DOC and less than half of naphthenic acids (NAs) (39.1 %) in PASS-treated FFT were potentially released. The distribution coefficient value of DOC and NAs was comparably high, indicating that DOC and NAs were mostly stable within the PASS-treated FFT deposition. The study reflects considerable stability of PASS-treated FFT about the physical and chemical conditions of the lake water, making them a promising alternative in FFT management. [ABSTRACT FROM AUTHOR]

• NAs cause intestinal inflammation and oxidative stress in marine medaka gut. • 10 mg/L NAs significantly reduced the diversity of intestinal flora. • •Relative abundance of DBS1, Pseudomonas and Haloferula increased and Vibrio decreased. Naphthenic acids (NAs) are important pollutants in marine crude oils and have obvious toxic effects on marine organisms. However, the effects of NAs on the intestine are largely unknown. Thus, we evaluated the effects of NAs exposure in the intestines of marine medaka. Fish were experimentally exposed to NAs (0.5 mg/L, 5 mg/L, and 10 mg/L) for 96 h and monitored for changes in intestinal histology, markers of oxidative stress, and intestinal microbiome responses. Significant mucosal damage, inflammation, and oxidative stress were observed in the intestines of marine medaka after exposure to NAs. In addition, significant changes in the gut microbiota were observed. Specifically, the relative abundance of Proteobacteria decreased, while that of Verrucomicrobiota increased in the high-concentration exposure group. In addition, nutrient synthesis and metabolism in the gut were affected. The results of this study contribute to a better understanding of the ecological risk of different concentrations of NAs to marine organisms. Changes in the gut microbial community of marine medaka (Oryzias melastigma) caused by naphthenic acids in the marine environment were investigated through the assessment of gut inflammatory factors and comprehensive analysis using 16S rDNA high-throughput sequencing. The results indicated the induction of intestinal inflammation and changes in the structural composition of the intestinal flora. [ABSTRACT FROM AUTHOR]

In this study, the Fe(III)/WS 2 /peroxymonosulfate (PMS) system was found to remove up to 97% of cyclohexanecarboxylic acid (CHA) within 10 min. CHA is a model compound for naphthenic acids (NAs), which are prevalent in petroleum industrial wastewater. The addition of WS 2 effectively activated the Fe(III)/PMS system, significantly enhancing its ability to produce reactive oxidative species (ROS) for the oxidation of CHA. Further experimental results and characterization analyses demonstrated that the metallic element W(IV) in WS 2 could provide electrons for the direct reduction of Fe(III) to Fe(II), thus rapidly activating PMS and initiating a chain redox process to produce ROS (SO 4 •−, •OH, and 1O 2). Repeated tests and practical exploratory experiments indicated that WS 2 exhibited excellent catalytic performance, reusability and anti-interference capacity, achieving efficient degradation of commercial NAs mixtures. Therefore, applying WS 2 to catalyze the Fe(III)/PMS system can overcome speed limitations and facilitate simple, economical engineering applications. [Display omitted] • Fe(III)/WS 2 /PMS system can achieve 97% removel rate of CHA within 10 min. • •OH, SO 4 •−, and 1O 2 are main ROS in the Fe(III)/WS 2 /PMS system. • W(IV) contained in WS 2 can promoting Fe(III)/Fe(II) cycle by providing electrons. • Fe(III)/WS 2 /PMS system can achieve efficient degradation of commercial NAs. • Fe(III)/WS 2 /PMS system exhibits excellent reusability and anti-interference. [ABSTRACT FROM AUTHOR]

Bitumen extraction in Alberta's oil sands region uses large volumes of water, leading to an abundance of oil sands process-affected water (OSPW). OSPW contains naphthenic acid fraction compounds (NAFCs) which have been found to contribute to OSPW toxicity. This study utilized a multistep treatment, coupling biological degradation with UV photocatalytic oxidation, and nutrient addition to boost the native microbial community's degradation capacity. OSPW initially contained 40–42 mg/L NAFCs with a toxicity of 3.8–3.9 TU. Initial biodegradation (Step 1) was used to remove the easily biodegradable NAFCs (11–25% removal), followed by a light or heavy dose of oxidation (Step 2) to breakdown the recalcitrant NAFCs (66–82% removal). Lastly, post-oxidation biodegradation with nutrients (Step 3) removed the residual bioavailable NAFCs (16–31% removal). By the end of the multistep treatment, the final NAFC concentrations and toxicity ranged from 5.3 to 6.8 mg/L and 1.1–1.2 TU. Analysis showed that OPSW was limited in phosphorus (below detection limit), and the addition of nutrients improved the degradation of NAFCs. Two treatments throughout the multistep treatment never received nutrients and showed minimal NAFC degradation post-oxidation. The native microbial community survived the stress from UV photocatalytic oxidation as seen by the post-oxidation NAFC biodegradation. Microbial community diversity was reduced considerably following oxidation, but increased with nutrient addition. The microbial community consisted predominately of Proteobacteria (Gammaproteobacteria and Alphaproteobacteria), and the composition shifted depending on the level of oxidation received. Possible NAFC-degrading microbes identified after a light oxidation dose included Pseudomonas , Acinetobacter and Xanthomonadales, while Xanthobacteracea and Rhodococcus were the dominant microbes after heavy oxidation. This experiment confirms that the microbial community is capable of degrading NAFCs and withstanding oxidative stress, and that degradation is further enhanced with the addition of nutrients. [Display omitted] • A multistep treatment was used: initial biodegradation, UV photocatalytic oxidation, and final biodegradation. • Significant NAFC removal and detoxification was observed. • Biodegradation was most effective with nutrient amendment. • Native microbes survived oxidation but diversity was significantly reduced. • Dominant microbial species shifted depending on the level of oxidation received. [ABSTRACT FROM AUTHOR]

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 (O 2 –NAs, 58% and 49%) in undiluted and half-diluted OSPW, respectively. The increased ratios of oxidized NAs (O 3 –O 6 NAs) to classical NAs suggested a transformation trend. The results also indicated that O 2 –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 O 2 –O 6 NA species and BE-SPME concentrations unveiled the changes in the relative abundances of O 2 –O 6 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. [Display omitted] • Naphthenic acids (NAs) in OSPW demonstrated removal over time in constructed mesocosms. • BE-SPME results of mesocosm samples displayed a temporal decrease in bioavailable organics. • Microtox® assay showed considerable toxicity reduction over time in mesocosm samples. • Removal of NAs and BE-SPME correlated well with the reduction in acute toxicity. [ABSTRACT FROM AUTHOR]