Compounds In Crude Oil Research Articles

Genesis of Organochlorine Compounds in Crude Oil and Petroleum Products (A Review)

Genesis of Organochlorine Compounds in Crude Oil and Petroleum Products (A Review)

Cellular accumulation of crude oil compounds reduces the competitive fitness of the coral symbiont Symbiodinium glynnii

Oil spill events in the marine environment can have a deleterious impact on the affected ecosystems, such as coral reefs, with direct consequences for their socioeconomic value. The mutualistic relationship between tropical corals and their dinoflagellate symbionts (Symbiodiniaceae) provide structural and nutritional basis for a high local biodiversity in oligotrophic waters. Here, we investigated effects of crude oil water-accommodated fraction on the competitive fitness of the model zooxanthellae species Symbiodinium glynnii. Results of laboratory essays demonstrate that crude oil carbon is incorporated into the cellular biomass with a concomitant change of δ13C isotopic value. Carcinogenic/mutagenic polycyclic aromatic hydrocarbons were identified in the culture media and were responsible for a linear reduction in population growth of S. glynnii, presumably related to energy relocation for DNA repair. Additionally, the experiments revealed that physiological effects induced by crude oil compounds are genetically inherited by the following generations under non-contaminated growth conditions, and induce a reduction in the competitive fitness to cope with other environmental parameters, such as low salinity. We suggest that the effects of crude oil contamination represent an imparing factor for S. glynnii coping with anthropogenic drivers (e.g. warming and acidification) and interfere with the delicate symbiont-host relationship of tropical corals. This is especially relevant in the coastal areas of northeastern Brazil where an oil spill event deposited crude oil on shallow water sediments with the potential to be resuspended to the water column by physical and/or biological activity, enhancing the risk of future coral bleaching events.

Different effect of chemical refining process on Baneh (Pistacia atlantica var mutica) kernel oil: Regeneration of tocopherols.

The present study was conducted to investigate the impact of refining process on the chemical properties (fatty acid composition and tocopherols, sterols, and polyphenolic contents), qualitative parameters (peroxide value, acid value, and p‐anisidine value), and antioxidant activity (DPPH radical scavenging assay and FRAP test) of Baneh (Pistacia atlantica var mutica) kernel oil. The results revealed that the refining process had no significant effect on the fatty acid composition. A major finding of this research was the increase in the tocopherol and sterol content up to the bleaching stage followed by their decrease in the deodorizing phase. Some tocopherol and sterol compounds in crude oil were dimerized or attached to other compounds by ester bonding, which are released during some stages of the refining process and this factor is responsible for their increase. In fact, during this process, these compounds are regenerated. The occurrence of this phenomenon in the refining process improved the DPPH radical scavenging power of Baneh kernel oil up to the bleaching stage. Moreover, the content of phenolic compounds decreased after refining of Baneh kernel oil, and only in the deodorizing stage, an increase of these compounds was observed. In general, the results of this study showed that the refining process had a completely different effect on the antioxidant compounds (especially tocopherols) compared to other oils.

Efficient biodesulfurization of diesel oil by Gordonia sp. SC-10 with highly hydrophobic cell surfaces

Biodesulfurization is a promising, environmentally friendly method to desulfurize the organosulfur compounds in crude oils through the highly selective cleavage of carbon-sulfur bonds under mild reaction conditions. In this study, the behavior of a hydrophobic bacterium, Gordonia sp. SC-10, was evaluated in the presence of diesel oils. The biodesulfurization pathways, bacterium hydrophobicity, and cell ultrastructure were investigated, and the capability of strain SC-10 to desulfurize diesel oil was also studied. The results showed that strain SC-10 can desulfurize organosulfur compounds through sulfur-specific desulfurization pathways by producing corresponding hydroxylated products in oil-water polyphasic systems. Mycolic acids consisting of 47 and 58 carbon atoms chains were produced on the cell surface, and inclusion bodies were produced in the cells, both of which may improve the bioavailability of the substrates, thereby enhancing its adaptability to oil-water polyphasic systems. To our knowledge, this is the first report of intracellular inclusion body formation during biodesulfurization. Strain SC-10 also exhibited broad substrate specificity towards organosulfur compounds and effectively desulfurized diesel oils. The sulfur content in real-life diesel oil was reduced from 167.7 mg/L to 19.7 mg/L, with 88.3% of sulfur removed after five days of biodesulfurization. This study showed that Gordonia sp. SC-10 can be effectively used for the biodesulfurization of diesel oils.

MicroRNA (miRNA) Differential Expression and Exposure to Crude-Oil- Related Compounds.

This review summarizes studies on miRNA differential regulation related to exposure to crude oil and 20 different crude oil chemicals, such as hydrocarbons, sulphur, nitrogen, and metal- containing compounds. It may be interesting to explore the possibility of using early post-transcriptional regulators as a potential novel exposure biomarker.Crude oil has been defined as a highly complex mixture of solids, liquids, and gases. Given the toxicological properties of the petroleum components, its extraction and elaboration processes represent high-risk activities for the environment and human health, especially when accidental spills occur. The effects on human health of short-term exposure to petroleum are well known, but chronic exposure effects may variate depending on the exposure type (i.e., work, clean-up activities, or nearby residence).As only two studies are focused on miRNA differential expression after crude-oil exposure, this review will also analyse the bibliography concerning different crude-oil or Petroleum-Related Compounds (PRC) exposure in Animalia L. kingdom and how it is related to differential miRNA transcript levels. Papers include in vitro, animal, and human studies across the world.A list of 10 miRNAs (miR-142-5p, miR-126-3p, miR-24-3p, miR-451a, miR-16-5p, miR-28-5p, let-7b-5p, miR-320b, miR-27a-3p and miR-346) was created based on bibliography analysis and hypothesised as a possible “footprint” for crude-oil exposure. miRNA differential regulation can be considered a Big-Data related challenge, so different statistical programs and bioinformatics tools were used to have a better understanding of the biological significate of the most interesting data.

Effects of crude oil and aromatic compounds on growth and bioluminescence of Vibrio campbellii FS5.

Fifteen native luminescent bacteria were isolated from the Gulf of Thailand, and their sensitivity for the detection of toxicity of crude oil and its aromatic components was investigated. Of these isolates, Vibrio campbellii strain FS5 was one of the two most highly inhibited bacteria at all crude oil concentrations. This bacterium showed a decrease in luminescence intensity of between 10.7 and 80.2% after a 15-min exposure to 0.0001-10mg/L of crude oil. The degree of bioluminescence inhibition increased with increasing concentrations of crude oil. The presence of crude oil at all concentrations had negative effects on the log bioluminescence per log number of viable cells after 15- to 105-min exposure. About 10 to 100 times, lower half maximal effective concentration (EC50) values were observed for polycyclic aromatic hydrocarbons (PAHs) than those for benzene, toluene, ethylbenzene, and xylene (BTEX). In the presence of each individual BTEX and PAH, the bioluminescence inhibition increased with increasing exposure time (1-32h). This indigenous bacterium can be used as a simple and general indicator of oil contamination and its impact on coastal waters as well as for assessing potential toxicity during oil bioremediation.

Synergistic effect of salt ions and water‐soluble amphiphilic compounds of acidic crude oil on surface and interfacial tension

AbstractThis study investigated the effect of solubility of amphiphilic compounds of acidic crude oil in water on the surface and interfacial tension (IFT) with NaCl, MgCl2, CaCl2, and Na2SO4 salts. Accordingly, distilled water, along with the salts mentioned in zero ionic strength up to 2 mol were put in contact with crude oil to become saturated with amphiphilic compounds. The effects of these compounds were investigated on the properties of contact water by pH, total organic carbon (TOC), FTIR (Fourier transform infrared spectroscopy), water‐air surface tension (ST), and water‐n‐decane IFT tests. The results showed that some of the organic components of crude oil, especially acidic and basic compounds, are present or soluble in water, which have a significant effect on reducing the surface and IFT. The IFT reduction of water‐n‐decane was greater than the water‐air ST system. Also, the observations showed that for both NaCl and Na2SO4 salt water, with increasing ionic strength of water, there was an optimum salinity within the range of 0.1‐0.25 mol/L for both salts with the amount of surface and IFT minimized at this point. In the other two salts, this point was delayed upon elevation of ionic strength and was observed at high salinity. In this case, divalent cations reduce tension rate compared to monovalent cations. Due to solubility of acidic and basic groups in water, pH of salt water illustrates an acidic trend. Results of the FTIR test confirmed solubility of these compounds as well.

Genomic characterization of a polyvalent hydrocarbonoclastic bacterium Pseudomonas sp. strain BUN14

Bioremediation offers a viable alternative for the reduction of contaminants from the environment, particularly petroleum and its recalcitrant derivatives. In this study, the ability of a strain of Pseudomonas BUN14 to degrade crude oil, pristane and dioxin compounds, and to produce biosurfactants, was investigated. BUN14 is a halotolerant strain isolated from polluted sediment recovered from the refinery harbor on the Bizerte coast, north Tunisia and capable of producing surfactants. The strain BUN14 was assembled into 22 contigs of 4,898,053 bp with a mean GC content of 62.4%. Whole genome phylogeny and comparative genome analyses showed that strain BUN14 could be affiliated with two validly described Pseudomonas Type Strains, P. kunmingensis DSM 25974T and P. chloritidismutans AW-1T. The current study, however, revealed that the two Type Strains are probably conspecific and, given the priority of the latter, we proposed that P. kunmingensis DSM 25974 is a heteronym of P. chloritidismutans AW-1T. Using GC-FID analysis, we determined that BUN14 was able to use a range of hydrocarbons (crude oil, pristane, dibenzofuran, dibenzothiophene, naphthalene) as a sole carbon source. Genome analysis of BUN14 revealed the presence of a large repertoire of proteins (154) related to xenobiotic biodegradation and metabolism. Thus, 44 proteins were linked to the pathways for complete degradation of benzoate and naphthalene. The annotation of conserved functional domains led to the detection of putative genes encoding enzymes of the rhamnolipid biosynthesis pathway. Overall, the polyvalent hydrocarbon degradation capacity of BUN14 makes it a promising candidate for application in the bioremediation of polluted saline environments.

Histological Effects of Light Crude Oil on Sciaenops ocellatus Under Experimental Conditions.

The health status of Sciaenops ocellatus was studied by qualitative and quantitative histopathological analysis through histological damage prevalence and degree of tissue change (DTC) in response to 96h and 9days of exposure to 0.1, 0.8, and 8g/L of light crude oil in seawater. The histology of the liver, spleen, kidney, and gills of the fish were analyzed and compared between treatments. Our results showed that the exposed fish developed lesions associated with degenerative and necrotic changes. The highest frequency of damage and DTC scores were observed in the liver and kidney from 96h to 9-days post-exposure. Generalized additive models of location, scale, and shape, showed that the DTC was strongly associated with crude oil compounds such as napthalene, Cd, Ni, Pb, and bile polycyclic aromatic hydrocarbon metabolites. Our findings suggest that exposure to crude oil affects fish health, producing irreversible histological damage.

Derivative UV-Vis Spectroscopy of Crude Oil and Asphaltene Solutions for Composition Determination

The determination of the first and second derivatives in the UV spectra of crude oil and asphaltene solutions allows the identification of signals attributed to compounds in the crude oil that cannot be seen in the normal spectrum. This processing of the crude oil UV-Vis spectrum to determine first and second derivatives allowed the identification of five maxima. The maxima observed in the first derivative spectrum can be related to different types of compounds in crude oil: ~230 nm for benzene compounds, 259 nm for naphthalene compounds and their derivatives, 295 nm for pure phenanthrene, 328 nm for aromatic chromophores with three or four aromatic rings, and 401 nm for the Soret electronic absorption band of vanadyl porphyrins. The shape of the spectra was analyzed to predict the presence of colloids or particles in the solutions.

Chemically induced demulsification of water in crude oil emulsion from East Kalimantan oil fields

The application of demulsifiers on dewatering of crude oil emulsions from East Kalimantan oil fields is reported in this work. Two types of experiment were conducted: the bottle test in which emulsion resolution was carried out after demulsification process within the time intervals of 0, 5, 10, 15, 20, 25, 30, 40, 50, 60, 120 and 180 min at temperature of 40 °C followed by the appearance of separated aqueous layer, and identification of variety of fractions or compounds in crude oils that promote and stabilize these emulsions. Demulsification was successfully obtained by adding PT Pertamina (Persero)’s commercial demulsifier series of Pertadem B-02 and Pertadem B-06. Pertadem B-02 is the best candidate for destabilizing water in oil emulsions. The optimal percentage demulsification efficiency (DE) achieved by Pertadem B-02 was 100% with just concentration of 18 ppm for field A and 97% for field B. Moreover, demulsification activities in the water in oil emulsions by Pertadem B-02 were faster compared to Pertadem B-06. Fractions identifications showed emulsifying agents in crude oil of Field A that promote very unstable emulsions compared to crude oil of Field B from East Kalimantan.

Functional compounds of crude oil during low salinity water injection

Due to the intrinsic complexity of crude oil, the advanced chemical compositional analysis would be required to detect the crucial interactions that may take place between water and crude oil during low salinity water injection (LSWI). In this study, a series of analytical techniques were combined to discover the functional compounds of crude oil contributing to low salinity water effect (LSE) during LSWI. The Fourier Transform Infrared (FT-IR) analysis and Fourier Transform Ion Cyclotron Resonance Mass Spectroscopy (FT-ICR MS) were deployed to characterise the oil/water interface of a chosen crude oil with a high potency toward formation of water microdispersion. Using the negative and positive electrospray ionisation modes (−ESI and +ESI, respectively), acidic compounds with aliphatic nature and asphaltene molecules were determined to be the most functional compounds at the interface promoting the spontaneous formation of water-in-oil microdispersion. These species are key to designing any waterflood operation in oil reservoirs.

Characterization of nitrogen-containing compounds in petroleum fractions by online reversed-phase liquid chromatography-electrospray ionization Orbitrap mass spectrometry

Characterization of heteroatom compounds in crude oils is very important in petroleum production and processing. The ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is a powerful MS technique for it but with expensive costs. It is necessary to develop a generally accepted alternative analytical approach to replace FT-ICR MS. In this study, a reversed-phase liquid chromatography (RPLC)-high-resolution (HR) MS method was proposed on an Orbitrap MS with electrospray ionization (ESI). The optimal chromatographic and MS parameters and internal mass calibration method were suggested. The sample complexity was greatly reduced by RPLC separation. Mass resolution (240 K at m/z 200) of Orbitrap MS was enough to obtain an accurate elemental assignment in complex petroleum fractions. False-positive element composition assignment could be easily excluded by the RPLC retention behavior of isomers. The performance of RPLC-Orbitrap MS was evaluated in comparison with direct injection (DI)-FT-ICR MS and DI-Orbitrap MS in positive ion mode for heavy oil analysis. The results showed that heteroatom class species, DBE vs carbon number distributions were very similar between RPLC-Orbitrap MS and DI-FT-ICR MS. The developed methods were further used to analyze petroleum oil fractions with boiling ranges at 180–350 °C, 350–530 °C and >530 °C. Detailed heteroatom class species and corresponding DBE vs carbon number distributions were obtained. This study demonstrated that the RPLC-Orbitrap MS technique could successfully be applied for heteroatom compound characterization in petroleum fractions.

Experimental study on the causes and critical conditions of toxic gases in hydraulically fractured oil wells

ABSTRACT Hydraulic fracturing is the most preferred oil well stimulation technology worldwide. In fractured oil wells, toxic gases (hydrogen sulfide and carbon monoxide) present a problem when the produced water is reclaimed as base fluid for fracturing. These gases can cause equipment corrosion, environment pollution, and adversely affect the operational personnel’s health. Extant research focuses on toxic gases produced at high temperatures (>200 °C). Therefore, this paper examines the causes and critical conditions for toxic gas formation in fractured wells in conventional reservoirs at low temperatures (<160 °C) through a series of laboratory experiments that include bacterial culture and heating experiments. The results show that for temperature in the range 40–60 °C, the presence of sulfate-reducing bacteria in the produced water is the main cause of hydrogen sulfide production in fractured wells. However, when the temperature is higher than 102 °C, the sulfur compounds (potassium persulfate and sodium sulfite) in the fracturing fluid and crude oil can produce hydrogen sulfide by thermochemical sulfate reduction. In addition, when the temperature is higher than 75 °C, oxygenated compounds (aldehydes) in crude oil can produce carbon monoxide by decarbonylation. Both processes can occur simultaneously when the temperature is higher than 102 °C. This paper is of great significance in controlling the formation of toxic gases in fractured wells.

A potential material for removal of nitrogen compounds in petroleum and petrochemical derivates

Activated carbon from coconut shell (Elaeis guineensis), in both crude and chemically modified forms, was evaluated as an adsorbent for removing nitrogen compounds of samples from synthetic and real fuel. The preliminary adsorption tests showed that 97.95 of indoline was removed by sulfuric acid-treated activated carbon (SAAC). The optimum conditions toward adsorption of nitrogen-containing compounds in crude oil (54 °C, 150 rpm and 1.104 g of adsorbent) was evaluated according to the design of experiments (DOE) technique associated with Differential Evolution optimization algorithm and an effective removal of 30.37% of basic nitrogenous compounds present in crude oil was achieved. For comparative effect, the tests were carried out using the previously optimized condition with the vacuum residue, diesel S-500, and diesel S-10, obtaining the removal of 21.56%, 44.44%, and 62.09%, respectively. Complementing the quantitative analysis, the analysis of mass spectrometry confirmed that coconut shell is a potential material for selective adsorption of nitrogenous compounds.

Quantitative analysis of PAH compounds in DWH crude oil and their effects on Caenorhabditis elegans germ cell apoptosis, associated with CYP450s upregulation

The Deepwater Horizon (DWH) oil spill marked the largest environmental oil spill in human history, where it was estimated a large amount of the polycyclic aromatic hydrocarbons (PAHs) were released with crude oil into the environment. In this study, common PAH compounds were quantitatively determined in crude oil from the DWH spill by gas chromatography-mass spectroscopy (GC–MS). Twelve PAH compounds were identified and quantified from a 100× dilution of DWH crude oil: naphthalene (7800 ng/mL), acenaphthylene (590 ng/mL), acenaphtehen (540 ng/mL), fluorene (2550 ng/mL), phenanthrene (2910 ng/mL), anthracene (840 ng/mL), fluoranthene (490 ng/mL), pyrene (290 ng/mL), benzo(k) fluoranthene (1050 ng/mL), benzo(b)fluoranthene (1360 ng/mL), dibenz(a,h)anthracene (2560 ng/mL), and benzo(g, h, i) perylene (630 ng/mL). Toxicity assays using the nematode, Caenorhabditis elegans (C. elegans), indicated a single PAH compound naphthalene, exposure increased C. elegans germ cell apoptosis which may adversely affect progeny reproduction. The number of apoptotic germ cells significantly increased from 1.4 to 2.5 when worms were treated with 10 μg/mL of naphthalene and from 1.3 to 2.5 and 3.5 cells in presence of 1 μg/mL and 5 μg/mL of benzo(a)pyrene, respectively. Five CYP450 genes (CYP14A3, CYP35A1, CYP35A2, CYP35A5, and CYP35C1) were significantly upregulated following 500× dilution of dispersed crude oil exposure (p < 0.05). These results suggest that CYP450s may play a role in bioactivation of PAHs in crude oil, resulting in DNA damage related germ cell apoptosis.

Investigating biological nitrogen cycling in lacustrine systems by FT-ICR-MS analysis of nitrogen-containing compounds in petroleum

Biological nitrogen cycling plays an important role in bio, environmental and petroleum geochemistry. Until now most research has focused on marine environments using nitrogen isotopes, and in contrast, nitrogen cycling in lacustrine environments remains poorly understood. To fill this knowledge gap, we present a case study of crude oils from Permian brackish and saline alkaline lacustrine rocks in the Junggar Basin, northwestern China. To complement the large variation in nitrogen isotope values in lacustrine sediments, we analyzed the pyrrolic N-containing compounds of crude oil using negative ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS). Our results show that pyrrolic compounds derived from biological sources are more abundant in oils from brackish lacustrine settings (i.e., the Jimusar Sag oils of the Junggar Basin) than in oils from alkaline lacustrine settings (i.e., the Mahu Sag oils of the Junggar Basin), which is mainly due to greater higher plant contributions to the latter. Higher plants provide abundant alkaloids and chlorophyll that are the biological precursors of pyrrolic N-containing compounds. In addition, anoxic, sulfate-type, brackish lacustrine settings provide abundant ferrous iron and sulfide that promote N fixation. This study provides the first insights into biological N cycling in brackish and alkaline lacustrine systems, which has significance for fossil fuel resources and their environmental impacts. Our data suggest that the N cycling in lacustrine systems might have an important role in entire Earth system N budget.

Determination of water content of crude oil by azeotropic distillation Karl Fischer coulometric titration

The determination of water content in crude oil is important for oil transportation, refining, and trade. However, the sensitivity and accuracy of the conventional azeotropic distillation (AD) method are inadequate. Karl Fischer titration methods may give false high results because of the reducing sulfur compounds in crude oil. The present study developed an azeotropic distillation Karl Fischer coulometric titration (AD-KFCT) method which required a modified instrument and a new calibration procedure. The method was modified to decrease the interference caused by reducing sulfur compounds. A certified reference material for water content in liquid was used to determine the recovery of water mass achieved using the AD-KFCT method. The effect of the sample polarity on the method accuracy was assessed. The relative error and relative standard deviations of the water content in three crude oils containing known amounts of water were -7.5% to 2.9% and 0.4% to 6.0%, respectively. The interference by reducing sulfur compounds was studied. The crude oil containing 1-propanethiol was measured using a sulfur dioxide-free anolyte, and the amount of iodine consumed by the distilled 1-propanethiol was determined. The contribution of 1-propanethiol was then subtracted from the water content measured using the normal Karl Fischer reagent. Finally, the relative error of the modified water content in the crude oil samples containing 1-propanethiol was -4.4% to 0.7%. Therefore, the modified AD-KFCT method is accurate and convenient for crude oil.

Kinetic modeling of asphaltene nano-aggregates formation using dynamic light scattering technique

Asphaltene is known as a class of polar poly-nuclear aromatic compounds of crude oil which is extracted by its solubility difference in normal heptane and toluene. Precipitation of this hydrocarbon compound by changing in fluid thermodynamic conditions decelerates flow when passing through up-stream and down-stream processes. In order to understand the thermodynamics of the deposition phenomenon, one needs to pay attention to the kinetics of the aggregation of these nano-particles. In this study, the kinetics phenomenon of aggregation of asphaltene clots in toluene is investigated using dynamic light scattering (DLS) technique. The dynamic light scattering results for super dilute solutions showed that at high and low sonication time, the asphaltene is monomeric and polymeric forms, respectively. Moreover, the experiments revealed that the relationship between the amount of sonication energy given to the solutions and the particle size is logarithmic. The DLS spectra obtained from the lower-sonication solutions were decomposed to the four normal distributions using the deconvolution technique, indicating four different clusters in the solution. The ratio of the area of each normal distribution to the area of the spectrum indicates the fraction of the presence of each cluster in the solution. For the lower and the higher concentrations of the asphaltene solution, the percentage of nano-aggregates is between 8%-41% and 4%–51%, respectively. By assuming the asphaltene molecule to be on a coin-shaped plate and forming a π bond with a minimal coinage overlap, the coin model of asphaltene aggregation kinetics has been developed. The concentration of each nano-aggregates in equilibrium solution is calculated according to the fraction of its presence in the medium and the coin model. Then, these equilibrium concentrations are used to calculate the equilibrium reaction constants. The correlation coefficient between the reaction constants and the diffusion coefficients of the clots in the solutions for all reactions was found to be equal to 0.42. This same value indicates that this coefficient is independent of the concentration of asphaltene in the solution and is dependent on the nature of the solution.

How do ions contribute to brine-hydrophobic hydrocarbon Interfaces? An in silico study

HypothesisThe saltwater-oil interface is of broad implication in geochemistry and petroleum disciplines. To date, the main focus has been on the surface contribution of polar, heavy compounds of crude oil, widely neglecting the role of non-polar hydrocarbons. However, non-polar compounds are expected to contribute to characteristics of oil-brine interfaces. MethodologyUtilizing molecular dynamics simulation, we aim to characterize ion behavior adjacent to hydrophobic organic phases. Concerning natural environments, NaCl, CaCl2 and Na2SO4 electrolytes at low (5 wt%) and high (15 wt%) concentrations were brought in contact with heptane and/or toluene which account for aliphatic and aromatic constituents of typical crude oils, respectively. The reproduced experimental data for interfacial tension, brines density and ions’ diffusivities adequately verify our molecular calculations. FindingsIons accumulate nearby the intrinsically charge-neutral oil surfaces. A disparate surface-favoring propensity of ions causes the interfacial region to resemble an electrical layer and impose an effective surface charge onto the oil surface. Despite absence of any polar site, the effective surface charge density is hydrocarbon-dependent, with the highest and lowest values observed for toluene and heptane interfaces, respectively. Due to accumulation of toluene molecules nearby the brines, the interfacial characteristics of heptol (toluene-heptane mixture) is comparable to that of the toluene phase.