Oil Fouling Research Articles

Coupled effect of organic fouling and scaling in the treatment of hyper-saline produced water using forward osmosis

Hyper-saline water streams, such as the produced water from the oil industry, cannot be treated via the conventional desalination method, such as reverse osmosis (RO), due to the extreme required pressure to overcome the osmotic pressure. This research investigates the effect of oil fouling and cleaning behaviors when the forward osmosis (FO) process is applied to treat hyper-saline-produced water. Synthetic produced water with total dissolved solids (TDS) concentration of 240 g/l (contained Na, Ca, Mg, Fe, Cl, SO4, and CO3 ions) and oil content of 100 ppm was used as a feed solution. Also, two draw solutions, namely: ammonium bicarbonate (NH4HCO3) and magnesium chloride (MgCl2) of concentrations 6 M and 4.8 M, respectively, were utilized for the FO operation. Results showed that the MgCl2 draw solution provided significantly higher water flux than NH4HCO3 due to MgCl2’s high osmotic pressure and low scaling influence. Furthermore, the individual impact of oil was found to be low on the FO’s water flux. However, a synergistic effect between the oil and inorganic scaling was noticed. SEM technique was used to comprehend the observation and analyze the fouling content. Although the feed was a highly polluted stream, it was found that osmotic backwashing can recover more than 90% of the initial flux.

Gradient Adhesive Hydrogel Decorated Superhydrophilic Membranes for Ultra‐Stable Oil/Water Separation

AbstractHydrogels are excellent for protecting membranes from oil fouling for oil/water separation. However, conventional hydrogels including adhesive hydrogels have a contradictory between high adhesion on membranes and anti‐oil‐fouling ability. Herein, the design of an adhesive hydrogel on membranes is proposed by ingeniously integrating high adhesion on membranes, outstanding anti‐oil‐fouling ability, ultrathin thickness suitable for membrane decoration and satisfactory durability, where an inside‐out gradient distribution of adhesive protocatechuic acid (PCA) and hydrated calcium alginate (CaAlg) on membranes is constructed. The innermost PCA enables the adhesive hydrogel to tightly adhere to the membranes. The outermost CaAlg defends membranes from oil fouling. The gradient distribution and uniform integration of PCA/CaAlg guarantee an excellent stability. Membranes decorated with the adhesive hydrogel demonstrate superhydrophilicity, anti‐fouling to various oils, and anti‐abrasion to external damaging. The membranes achieve ultra‐stable and efficient separation of surfactant‐stabilized oil‐in‐water emulsions and crude oil/water mixture with the most advanced cycling ability of ≈100% flux recovery and nearly zero irreversible oil fouling. This study provides a new strategy for designing anti‐oil‐fouling membranes toward practical oil/water separation applications.

Four-Dimensional Visualization of Microscale Dynamics of Membrane Oil Fouling via Synchrotron Radiation Microcomputed Tomography.

Although oil-water separation technology via wettability-controlled membranes has emerged as a promising technology to treat oily wastewater, membrane fouling by faulents such as sludge flocs and colloids, and the consequent clogging of pores, severely degrades the efficiency of filtration systems. One of the main promotors of fouling by faulents is oil fouling, which is also a form of fouling itself. Despite considerable practical and academic interest in the analysis of oil-fouled membranes, direct visualization of the entire process of oil infiltration into hydrophilic membranes is still preliminary owing to (i) the similar optical contrast and physical density between oil and water, (ii) the low penetration depth of imaging methods, and (iii) the lack of 3D segmentation capability. In this study, microcomputed X-ray tomography using tunable synchrotron radiation provided direct high-speed 3D visualization of the microscale dynamics of the oil infiltration of a prewetted hydrophilic filter membrane over time. Direct visualization of the interfacial dynamics of oil infiltration opens a window into the complex liquid (water/oil)-gas-solid interface and thus helps furnish an in-depth understanding of oil fouling in the prewetted membrane.

Comparison of omniphobic membranes and Janus membranes with a dense hydrophilic surface layer for robust membrane distillation

Membrane wetting, fouling, and scaling are three prominent challenges that limit membrane distillation (MD) applications. To overcome these challenges, novel MD membranes including omniphobic membranes and Janus membranes with a dense hydrophilic surface layer have been developed. In this study, we fabricated an omniphobic membrane and a Janus membrane composed of a dense polyvinyl alcohol (PVA) surface layer and a polyvinylidene fluoride (PVDF) substrate. The two membranes have been compared in MD experiments with different feeds. Furthermore, the working mechanisms of the two membranes have been elucidated. As a result, neither the omniphobic MD membrane nor the Janus MD membrane can resolve all three challenges at the same time. Specifically, both the omniphobic MD membrane and Janus MD membrane can resist wetting but via different working mechanisms. From breakthrough pressure (BP) determinations with an ethanol-water mixture (i.e., a low-surface-tension liquid), the omniphobic MD membrane resists wetting as its LEP (82.0 ± 9.2 kPa) is larger than the transmembrane pressure in the MD operation, while the Janus MD membrane resists wetting because the huge capillary pressure (550 ± 50 kPa) in the dense hydrophilic surface layer retains the wetting solution. The omniphobic MD membrane is prone to oil fouling because of the strong underwater hydrophobic attraction between the membrane surface and the mineral oil droplets, while the Janus MD membrane can substantially mitigate fouling due to the lack of attraction between the mineral oil droplets and the hydrophilic membrane surface. The omniphobic MD membrane exhibits outstanding scaling resistance because minerals can hardly precipitate and/or crystalize on the membrane surface, while the Janus MD membrane was susceptible to scaling due to the precipitation and/or crystallization of minerals inside the hydrophilic surface layer. Therefore, the selection of MD membranes should depend on the feed constituents. Overall, our study provides important guidelines for the future development of robust MD membranes.

Green and rapid fabrication of superhydrophilic and underwater superoleophobic coatings for super anti-crude oil fouling and crude oil-water separation

The development of surfaces with super anti-crude oil-fouling behavior and crude oil-water separation properties is still a global challenge owing to the high viscosity of crude oil. Herein, superhydrophilic and underwater superoleophobic surfaces were successfully prepared by a simple, green and environmentally friendly one-step dip coating method. In the whole process, microcrystalline cellulose with hydrophilic hydroxyl functional groups was introduced into the coating with the help of inorganic adhesives, water was the only solvent, and no other organic solvents or surface modifiers was added. Besides being highly resistant to low viscosity oils and achieving effective oil-water separation (more than 98.3% separation efficiency after 30 cycles), the surface effectively resisted crude oil adhesion and achieved high viscosity crude oil-water separation. In addition, the underwater oil contact angle can still reach 147.5° and 152.5° after 20 cycles of sandpaper friction tests and 50 cycles of finger pressure tests, respectively, which indicates excellent durability. Furthermore, the method can achieve excellent superhydrophilicity and underwater superoleophobicity on varieties of substrates (such as copper foil, aluminum sheet and glass), showing very extensive applicability. It is expected that such fabrication strategy can provide a low cost, green and environmentally friendly approach to construct a series of superhydrophilic and underwater superoleophobic surfaces to achieve super anti-crude oil-fouling and (crude) oil-water separation.

Eco-friendly Dopamine-Modified Silica Nanoparticles for Oil-Repellent Coatings: Implications for Underwater Self-Cleaning and Antifogging Applications

Solid materials ubiquitously suffer from oil fouling in engineering applications. In this work, a facile and economical method was proposed to prepare a substrate-independent self-cleaning coating with remarkable oil repellency, which were realized by dints of the surface of nanocomposite structures with polar groups introduced by silica nanoparticles and polydopamine. The dip coating preparation process can be carried out in an ambient atmosphere without the use of hazardous reagents or complex equipment. The coating displays self-cleaning performance to detach the adhered oil after being immersed into water. The underwater contact angles were measured over 150° to various oils, further retaining stability in corrosive aqueous environments. Moreover, the coated glass shows resistance to water condensation, which can remain transparent after steaming or frosting, due to its hydrophilicity. The special wettability also endows the coated fabric with permselectivity to water and oil. Modified filter cotton was utilized to separate five kinds of oil/water mixtures. This study proposed a tried-and-true approach to realize oil repellency. It is anticipated that it could set a precedent for the design of self-cleaning or antifouling coatings.

Cicada wing-inspired solar transmittance enhancement and hydrophobicity design for graphene-based solar steam generation: A novel gas phase deposition approach

The severe light reflection phenomenon has become a critical challenge for the sufficient utilization of solar energy. For preventing the predation risk, cicada’s wings are gradually evolved into transparent morphology to preferably blend into the natural environment. The high solar transmittance in cicada wings is due to the presence of surface micro/nanostructures which avoids the large change of refractive index between air and wings. Herein, inspired by the high solar transmittance of cicada’s wings, an extremely-simple gaseous phase deposition with low heating temperature is developed to cover graphene film with methyl-modified silicon dioxide (CH3-SiO2) nanospheres that decelerate the refractive index reduction. The destructive interference effect of CH3-SiO2 nanospheres effectively increases the solar transmittance to promote the absorption and conversion of solar energy into heat by graphene nanosheets. As a result, compared to pure graphene film, CH3-SiO2 nanospheres covered graphene (SiO2-graphene) film presents a temperature increase of ∼6.3 °C with solar illumination of 1.0 kW/m2. After being combined with zwitterion-modified cotton fabric, a novel solar steam generation system mainly composed of SiO2-graphene film is prepared. Due to the hydrophobicity of CH3-SiO2 nanosphere and the hydration effect of zwitterionic polymer, the salt precipitation and oil fouling problems regarded as major challenges in solar desalination are simultaneously solved, thus achieving water evaporation rate near 1.40 kg/m2h at oily seawater environment. Most importantly, the solar transmittance enhancement and anti-reflection design inspired by cicada wings provide a valuable reference to promote the solar absorption capacity of other photo-thermal conversion materials.

Universal Rapid Demulsification by Vacuum Suction Using Superamphiphilic and Underliquid Superamphiphobic Polyurethane/Diatomite Composites.

A process for universal rapid demulsification by vacuum suction using an as-prepared superamphiphilic and underliquid superamphiphobic polyurethane (PU)/diatomite composite has been developed and is used to demulsify kerosene-in-water and water-in-kerosene emulsions with and without a surfactant. The results show that the demulsification rate of all the emulsions exceeds 98.5% in long-term operation, with a stable demulsification speed exceeding 0.303 L/m2 min. When a superhydrophobic channel for separation is added, the oil/water separation efficiency exceeds 99.0%, and the final products are qualified oil and water. This attractive universal demulsification capability of PU/diatomite originates from its underliquid superamphiphobicity, which attracts a continuous phase to form a stable liquid film and thus repels dispersed phase droplets, which have a similar interaction with the surface but are much less abundant. The vacuum forces emulsion droplets into the microstructure of the PU/diatomite cake, where they are compressed, coalesce, and finally demulsified. This observed mechanism suggests a promising strategy to avoid the negative effects of oil fouling in demulsification and achieve large-scale universal continuous rapid demulsification.

Green, robust self-cleaning superhydrophilic coating and on-demand oil–water separation

Recently, biomimetic modified membranes for oil–water separation have attracted extensive attention. However, complex processing and severe oil fouling have always been the main obstacles to its application. To explore facile and green preparation methods is urgently desired. In this study, a green and facile modification strategy was proposed, when the feature that sodium periodate could promote procyanidin deposition was utilized to prepare superhydrophilic fabrics and superhydrophilic polyvinylidene fluoride membranes to separate oil–water mixtures on demand. This method could simultaneously build a rough structure and introduce polar functional groups on the substrate surface. The prepared materials possessed excellent oil–water separation ability and cycle stability. The flux and efficiency of separating immiscible oil–water mixtures through superhydrophilic fabrics could reach up to 38,100 L·m-2h−1 and 99.8%, while those of separating oil in water emulsion through superhydrophilic polyvinylidene fluoride membranes could be as high as 681 L·m-2h−1 and 99.5%, respectively, showing that the superhydrophilic materials wetted with water had excellent antifouling ability. The superhydrophilic coating was also featured with excellent chemical stability and mechanical durability. The preparation strategy of the superhydrophilic materials provided in this study can promote the development of oil–water separation technology.

Theory of oil fouling for microfiltration and ultrafiltration membranes in produced water treatment

Due to the complexity of oil-in-water emulsions, the existing literature is still missing a mathematical tool that can describe membrane fouling in a fully quantitative manner on the basis of relevant fouling mechanisms. HypothesisIn this work, a quantitative model that successfully describes cake layer formation and pore blocking is presented. We propose that the degree of pore blocking is determined by the membrane contact angle and the resulting surface coverage, while the cake layer is described by a mass balance and a cake erosion flux. ValidationThe model is validated by comparison to experimental data from previous works (Dickhout et al. 2019; Virga et al., 2020) where membrane type, surfactant type and salinity were varied. Most input parameters could be directly taken from the experimental conditions, while four fitting parameters were required. FindingsThe experimental data can be well described by the model which was developed to provide insight into the dominant fouling mechanisms. Moreover, where existing models usually assume that pore blocking precedes cake layer formation, here we find that cake layer formation can start and occur while the degree of pore blocking is still increasing, in line with the more dynamic nature of oil droplets filtration. These new conceptual advances in the field of colloid and interface science open up new pathways for membrane fouling understanding, prevention and control.

Cationic guar gum-kaolin coated combined superhydrophilic and oleophobic nylon textile for efficient oil separation from wastewater

The treatment of wastewater polluted by oils and organic solvents has becoming a global environmental issue. Superhydrophobic separation materials have been widely developed to solve the problems, these materials are easily fouled by high viscosity oil fouling, causing the decrease of separation efficiency. Developing the materials with high hydrophilicity and oleophobicity in air via a facile and inexpensive approach is vital to address the oily water problems. Herein, a guar hydroxypropyltrimonium chloride-perfluorononanoate/kaolin (GHTC-PFN/KL) coated nylon textile (NT) was fabricated via a facile dip-coating approach. The obtained textiles reveal good superhydrophilicity, high oleophobicity in air, and low oil adhesion. By virtue of their special wettability, the functionalized textiles without any pre-wetting allow water to pass but preventing the passage of oils, which enables the textiles to be utilized for the selective separation to water/oil mixtures. The separation efficiencies for different oils are more than 96.7%. The modified textiles are capable of separating the oils employed with acidic, alkaline, salty solutions and hot water. Especially, a large quantity of water underoil is able to be continuously separated in situ via the multilayered textile tube at vacuum system. Simple preparation steps, scalable process and low cost make the as-prepared textile an ideal candidate for dealing with oily wastewater and purifying water-containing oil.

Systematic Design of a Flow-Through Titanium Electrode-Based Device with Strong Oil Droplet Rejection Property for Superior Oil-in-Water Emulsion Separation Performance.

Oily wastewater treatment has been restricted by the existence of stable oil-in-water (O/W) emulsions containing micrometer-sized oil droplets. However, the strong adhesion and stacking of emulsified oil droplets on the surface of current separation media cause serious fouling of the treatment unit and the rapid decline of treatment efficiency. Herein, a novel flow-through titanium (Ti) electrode-based filtration device with remarkable oil droplet rejection property was well designed for the continuously separating O/W emulsion. In contrast to the pristine Ti foam, the permeance of the TiO2 nanoarray-coated Ti foam (NATF) increased from 2538 to 4364 L m-2 h-1 bar-1 through gravity-driven flow. Further, more than ∼70% permeability can be maintained after 6 h of O/W emulsion filtration using the current device, the value of which was markedly higher than that of conventional oil/water separation filters (less than 5%). According to the results of wettability test, the super-oil-repellent surface endowed by this nanoarray structure primarily avoided the formation of a compact oil fouling layer. When the voltage was applied, accompanied by the electrophoresis effect, redistribution of surfactant molecules on the surface of oil droplets induced by an electric field made them readily captured by the microbubbles continuously generated from the electrode, thereby rapidly migrating these bubble-adhered oil droplets far from the filtration medium.

Electro-Enhanced Separation of Microsized Oil-in-Water Emulsions via Metallic Membranes: Performance and Mechanistic Insights.

Conventional separation membranes suffer from evitable fouling and flux decrease for water treatment applications. Herein, a novel protocol of electro-enhanced membrane separation is proposed for the efficient treatment of microsized emulsions (∼1 μm) by rationally designing robust electroresponsive copper metallic membranes, which could mitigate oil fouling and coenhance permeance (from ∼1026 to ∼2516 L·m-2·h-1·bar-1) and rejection (from ∼87 to ∼98%). High-flux Cu membranes exhibit superior ductility and electrical conductivity, enabling promising electroactivity. Separation performance and the fouling mechanism were studied under different electrical potentials and ionic strengths. Application of negative polarization into a large-pore (∼2.1 μm) Cu membrane is favorable to not only almost completely reject smaller-sized oil droplets (∼1 μm) but also achieve antifouling and anticorrosion functions. Moreover, surfactants around oil droplets might be redistributed due to electrostatic repulsion, which effectively enhances the steric hindrance effect between neighboring oil droplets, mitigating oil coalescence and consequently membrane fouling. Furthermore, due to the screening effect of surfactants, the presence of low-concentration salts increases the adsorption of surfactants at the oil-water interface, thus preventing oil coalescence via decreasing oil-water interfacial tension. However, under high ionic strengths, the fouling mechanism converts from cake filtration to a complete blocking model due to the reduced electrostatic repulsion between the Cu membrane and oil droplets. This work would provide mechanistic insights into electro-enhanced antifouling for not only oil emulsion separation but also more water treatment applications using rationally designed novel electroresponsive membranes.

Bio-inspired robust superhydrophilic/underwater superoleophobic coating with lubrication, anti-crude oil fouling and anti-corrosion performances

The crude oil spill accidents cause numerous crude oil contaminations and oily wastewater. Underwater superoleophobic coating has excellent ability to resist crude oil contamination and separate oily wastewater. But it’s hard to keep stable performance against the physical or chemical attack. Herein, a robust underwater superoleophobic coating was fabricated by spraying the mixture of polyethyleneimine (PEI) and TiO2 on epoxy resin (E44) surface. Besides the good physical and chemical stability, the coating exhibited better drag reduction, anti-fouling performance and anti-corrosive performance in water compared with the commercially hydrophilic coating. The stainless steel mesh (SSM), coated by the E44/PEI/TiO2 coating, could separate different oil-water emulsions with a high oil rejection greater than 99.7%.

Lipase immobilization on alumina membranes using a traditional and a nature-inspired method for active degradation of oil fouling

This study compared the traditional method of silanization using 3-aminopropyltriethoxysilane (APTES) with the innovative technique of polydopamine coating (PDA) for lipase immobilization on α-alumina membranes. Three lipases were tested, and Eversa Transform 2.0 (ET2) was chosen to be immobilized in the membrane due to its high hydrolytic activity towards soybean oil. Polydopamine deposition with and without glutaraldehyde activation presented the highest membrane hydrolytic activities (1553 ± 209 and 1845 ± 283 U·m−2, respectively). The membrane without activation maintained 41.1 ± 1.7 % of the free enzyme activity while the one with glutaraldehyde preserved only 23.9 ± 1.0 %. When tested in oil–water separation using a soybean oil emulsion, the membranes with ET2 immobilized by PDA showed water permeance 2-fold higher than the nonactive membranes (300 ± 12 and 156 ± 4 L·h−1·m−2·bar, respectively), showing good fouling-degrading capacity. They also presented self-cleaning properties when activated through the use of proper pH and temperature. The water permeance recovery for the control membrane was 34% while the membranes with immobilized ET2 by PDA and APTES showed recoveries of 69% and 49%, respectively. Permeance recovery for ET2 immobilized by silanization was similar to the PDA-coated membrane with no enzyme (45%).

Investigation on Crude Oil Fouling Behavior

Investigation on Crude Oil Fouling Behavior

Fouling monitoring in oil-water flow using density profile

In water lubricated transportation of heavy crude oil, fouling monitoring on the walls of the pipe is fundamental, since it reflects in the cost of transportation. Although such phenomenon has been discussed by many researchers, more of experimental and theoretical evaluations have been carried out than numerical ones. For this reason, this work was aimed at using laminar Level-set (numerical method) to identify oil fouling (through oil density magnitude identification) on the upper and lower walls of a round horizontal pipe during water lubricated transportation. In order to achieve such objective, fluid constants (found in literature) and operational conditions established experimentally were applied to simulate and observe the density flow profiles along the upper and lower walls of a 2D pipe. Prior to the simulation process, a grid convergence test was carried out in order to establish a mesh which was capable of representing the flow characteristics, and at the same time reducing computational cost. Additionally, laminar Level-set was validated through comparing Reynolds numbers obtained from its application to analytical values calculated at the same conditions. Two main volumetric flow profiles (plug and core-annular flow- CAF) with their respective density profiles were obtained. In both cases, oil fouling was identified at specific regions of the pipe's upper and lower walls, presenting densities closer to 918.8 kg/m3.

Data-Driven Model of Crude Oil Fouling in Heat Exchanger Networks and its Application to Cleaning Schedule Optimization

Data-Driven Model of Crude Oil Fouling in Heat Exchanger Networks and its Application to Cleaning Schedule Optimization

Bench-scale oil fouling/antifouling tests under high temperature and high pressure conditions and the underlying interfacial interaction mechanisms

Oil fouling is commonly encountered in many environmental and engineering fields and remains a challenging issue. The fouling issue in steam-assisted gravity drainage (SAGD) process for extracting bitumen from oil sands deposits has received much attention from oil industry. In view of low capital investment and exceptional antifouling performance, adding antifoulants has emerged as a promising strategy for addressing fouling issues. Developing an efficient method to evaluate their antifouling performance under production conditions is urgently needed. In this work, we report a novel bench-scale test method for quantitatively evaluating the antifouling performance of antifoulants under high temperature and high pressure (HTHP), close to SAGD operation conditions. The effects of antifoulant dosage and stirring rate on the antifouling performance are systematically investigated. The underlying fouling and antifouling mechanisms are characterized through direct molecular and surface force measurements. It is found that the commercial antifoulant exhibits exceptional antifouling performance at the dosage range of 20–35 ppm, and increasing stirring rate enhances the antifouling behavior. The force measurement results indicate that the antifoulant can adsorb to organics and target substrate surfaces, performing the antifouling function by lowering the hydrophobic interaction between organics and target substrates. This work provides a novel and feasible method for characterizing fouling phenomena and evaluating antifoulants under HTHP conditions and improves the understanding of fundamental interaction mechanisms underlying the fouling and antifouling phenomena.

Simulation of the hydrodynamics in the onset of fouling for oil-water core-annular flow in a horizontal pipe

Core-annular flow is an efficient way of transporting viscous oil through a pipeline. A sharp increase in the pressure drop will occur when the oil waves at the water-oil interface touch the pipe wall. Depending on the oil and pipe material physical properties, the oil may adhere to the wall leading to fouling. Therefore, a necessary requirement for the onset of oil fouling of the pipe wall is that the flow hydrodynamics allow the oil to reach and touch the wall. With respect to the problem statement, this study deals with finding the hydrodynamic conditions under which core-annular flow becomes unstable and the oil waves touch the pipe wall. The method that is followed is to resolve the first-principle set of equations that describe the hydrodynamics: the Reynolds-Averaged Navier-Stokes (RANS) equations are solved using Computational Fluid Dynamics (CFD) in the opensource package OpenFOAM. Simulations were carried out for the horizontal pipe with two diameters (10.5 and 21 mm), at a range of imposed pressure drops and water holdup fractions (giving the mixture velocity and watercut as output). Most simulations were carried out for an oil to water viscosity ratio of 1040 (but also a variation of this was considered). For each value of the pressure drop (or mixture velocity) there is a critical value of the watercut below which the oil reaches the pipe wall. This critical value of the watercut is lower for the larger pipe diameter of 21 mm, namely about 9.6%, than for the smaller pipe diameter of 10.5 mm, namely about 14% (for a viscosity ratio m = 1040). Wall touching occurs when the mixture velocity is too low, but this lower limit is significantly higher for the larger pipe diameter of 21 mm, namely about 1.1 m/s, than for the smaller pipe diameter, namely about 0.3 m/s (for a viscosity ratio m = 1040). The main conclusion is that a state-of-art CFD approach is capable of simulating the growth of waves at the oil-water interface until they touch the pipe wall, which is a necessary condition for the onset of fouling.