Oil Contact Angle Research Articles

Bio‐Inspired Fabrication of Porous Aromatic Framework‐Coated Fabric for Achieving Durable Superhydrophobic Applications

AbstractPorous aromatic frameworks (PAFs) composed of high‐density phenyl units are renowned for stable micro/meso‐porous architecture and highly hydrophobic surface, which make them ideal candidates for durable superhydrophobic applications, especially under harsh conditions. Herein, a carbazole‐based PAF solid is synthesized using carbazole and triphenylamine as the building units through the CC linking pattern. For the first time, the PAF powder is uniformly deposited on the fabric surface via a facile dip‐coating method, which thus shows superhydrophobicity with high water contact angle of 153.8° and oil contact angle of approximately 0°. Consequently, the PAF‐coated fabric displays an outstanding simple oil/water mixture and separation efficiency of over 96% and enables simple and time‐saving cyclic utilization at least 10 times. Due to the ultrahigh stability of PAF skeleton, the PAF‐based composite maintains high superhydrophobicity under extreme conditions including high temperature, high humidity, and strong acidic/alkaline solutions. These results delineate important research advances toward the implementation of PAF powder in superhydrophobic applications.

Synthesis and electrospinning of multiscale‐ordered PLA/LDH@AgGB composite nanofibrous membrane for antibacterial and oil–water separation

AbstractIn recent years, the problem of oily sewage has seriously affected the ecological environment and human health. Thus, we prepared a novel biodegradable poly (lactic acid) (PLA) membrane with antibacterial property and oil–water separation function via electrospinning method. First, the matter of silver ion glass microbeads (AgGB) loaded with layered double hydroxides (LDHs) and the LDH@AgGB modified with 3‐triethoxysilyl‐1‐Propanamine (APTES) were synthesized. Then, the LDH@AgGB were blended with PLA to prepare PLA/LDH@AgGB composite. And the PLA nanofibrous membranes were electrospun. The results showed that APTES could significantly improve the dispersion and compatibility of LDH@AgGB in PLA matrix. The addition of A‐LDH@AgGB could greatly improve the crystallinity, and control the porosity and pore‐size of PLA membranes. The maximum water contact angle of the PLA membranes could reach to 109.31°, while the oil contact angle of the PLA membranes decreased to 0° resulting in a high oil absorption capacity, and fast oil absorption rate performance. Meanwhile, the PLA membrane had efficient antibacterial property against Escherichia coli. The reported novel LDH@AgGB and its PLA composite membrane provided a method for designing and preparing environmental‐friendly, high‐performance materials with both excellent antibacterial property and oil–water separation.

New insights into the synergism between silica nanoparticles and surfactants on interfacial properties: Implications for spontaneous imbibition in tight oil reservoirs

Nanofluids, a new cost-effective chemical additive for enhanced oil recovery (EOR) applications, have attracted increasing attention in the development of tight oil reservoirs. However, the underlying role of nanofluids in the EOR processes has yet to be identified. In this work, the synergistic effects between various surfactant molecules and silica NPs at oil/water, solid/liquid, or oil/water/solid three-phase system were systematically studied, and their effects on EOR in the tight sandstone reservoir were explored. Several silica-based nanofluids were prepared by dispersing silica nanoparticles (NPs) and surface-modifying chemical agents (i.e., anionic, nonionic, anion-nonionic, and amphoteric surfactants) in deionized (DI) water, and the properties of these nanofluids were further evaluated via dispersion stability, interfacial tension (IFT), wettability, spontaneous imbibition and nuclear magnetic resonance (NMR) tests at 60 °C. The experimental results showed that the imbibition efficiency potentials of stable nanofluids modified by different surfactants was: anionic-nonionic > anionic > nonionic > amphoteric. Micropores and mesopores contributed to majority of the imbibition recovery. The appropriate IFTs and oil contact angles for EOR potential were more than 1 mN/m and 140°, respectively. Anionic-nonionic and anionic surfactant nanofluids were suggested as better fracturing additives or EOR agents for sandstone reservoirs. In addition, it was proven that the IFT reduction and wettability alteration were mainly attributed to the synergistic effects of silica NPs and surfactant micelles. This research provides new insights into the underlying mechanism between surfactant nanofluids to interfacial interactions and EOR applications.

Modified phosphogypsum used as reinforcing material in composites

High-density polyethylene (HDPE)/phosphogypsum (PG) or polypropylene (PP)/PG composites were produced using mass-produced PG powders and a twin screw extruder. The modification effect of calcium stearate was studied by oil absorption value, contact angle, and FTIR. XRD analysis indicated that the PG phase was affected by different calcination temperatures. The mechanical properties of the composite materials were evaluated by tensile and impact tests. The dispersion of PG in the matrix was showed by scanning electron microscope (SEM). Within the weight fraction range studied (5, 10, 15, 20, 25, and 30 wt%), the Young’s modulus and tensile strength of the PG/HDPE composites increased significantly, but the impact strength and elongation at break decreased remarkably. Young’s modulus and impact strength of PG/PP composites increase prominently, but tensile strength and elongation at break are significantly reduced. Thermodynamic analysis showed that PG can improve the thermal stability of composite materials. The apparent density indicated that the composite material filled with PG has the property of being lighter in weight. In these experiments, the mechanical properties of compounding PG powder with HDPE or PP were significantly improved, but the toughness of composites decreased.

Superamphiphobic properties of fluorine doped graphene prepared by RF-PECVD: EIS and first principle study

A fluorine doped graphene (FDG) film was deposited on the surface of roving fabric by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). The micromorphology, functional group types, chemical composition, molecular structure and nanostructure image of the deposited films under different discharge power were characterized by field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and transmission electron microscope (TEM). The static and rolling−water/−oil contact angle were measured by contact angle meter. The electrochemistry properties were tested using electrochemical workstation. The superamphiphobic mechanism was studied by electrochemical impedance spectroscopy (EIS) and density functional theory (DFT), and the corresponding software were Gemry Echem Analyst and Materials Studio 7.0, respectively. The results show that the obtained FDG film has the best hydrophobic and oil repellent performance under the discharge power of 80 W. F atom in the FDG film is arranged on both side and the capacitance structure (C-model) is presented in the equivalent element by EIS fitting and DFT calculation under the discharge power of 80 W. The phenomenon proves that the electron transfer of free electrons from the position of K point in the Brillouin region of graphene surface was forbidden by the F atom, which is the mechanism of superhydrophobic and oil drainage on the FDG film surface.

Fabrication of superhydrophobic and lyophobic paper for self‑cleaning, moisture-proof and antibacterial activity

Paper-based materials have been used in every aspect of social life. However, the current paper-based materials face unprecedented challenges, such as limited lifespan and poor mechanical strength, owing to the deformation after absorbing a large amount of water and bacterial erosion. Herein, superhydrophobic and lyophobic paper was fabricated using internal sizing technology. Hydrophobically modified starch and Ag@SiO2 particles were added as two functional additives to paper pulp to promote a hierarchical structure formation with low surface energy. Consequently, the water and linseed oil contact angles of the obtained paper reached 154.8° and 138.4°, respectively. The resistance to moisture and water vapor also improved under high-humidity condition, the relative moisture content decreased from 511% to 278% and water vapor transmission rate also decreased from 97.44 to 21.23 g/m2·h. Furthermore, its mechanical properties could also be well maintained with a high fracture stress of 4.91 MPa. Besides, some liquid food, such as honey, easily rolled off the surface without leaving behind any residue, which demonstrated its self-cleaning ability. Furthermore, the modified paper exhibited notable bacterial repellency and antibacterial activity. This study provides an innovative method for endowing conventional paper with superhydrophobic and antibacterial properties, which can effectively expand their application scope.

Protonated cross-linkable nanocomposite coatings with outstanding underwater superoleophobic and anti-viscous oil-fouling properties for crude oil/water separation

Superhydrophilic/underwater superoleophobic coatings that effectively prevent viscous oil contamination have been of considerable interest for the great potential in oil spill remediation and oilfield wastewater treatment. In the present work, a protonated cross-linkable nanocomposite coating with robust underwater superoleophobicity and intensified hydration capability is proposed through the synthesis of active polymeric nanocomplex (PNC), cross-linking reaction between PNC and hydrophilic chitosan (CS), and final protonation to further improve water affinity. Benefiting from the hierarchical structure and strong hydration capability induced by electrostatic interactions and hydrogen bondings, the nanocomposite coating coated textile exhibits excellent superhydrophilicity (within 0.28 s with water contact angle reaching 0°), underwater superoleophobicity (underwater crude oil contact angle at 160°), and ultralow oil adhesion even to highly viscous silicone oil. Moreover, the nanocomposite coating presents a robust chemical resistance, mechanical tolerance, and storage stability. Simultaneously, the nanocomposite coating adapts well to various porous substrates (e.g., stainless steel mesh and Ni sponge) with great anti-oil-fouling and self-cleaning performances. Importantly, the coating coated textile is successfully applied in crude oil/water separation with excellent efficiency and repeatability. The findings conceivably stand out as a new methodology to fabricate superhydrophilic/underwater superoleophobic materials with outstanding anti-viscous oil-fouling property for practically treating oily wastewater.

Underwater superoleophobic mesh with robust Anthurium andraeanum-like attapulgite coating layer for effective oil spill recovery

It is highly desired to develop an efficient and stable approach to recover water from oil-water mixtures. In this work, we reported the facile fabrication of superhydrophilic and underwater superoleophobic membranes by coating a layer of Anthurium andraeanum-like attapulgite (ARATP) on commercially available wire meshes via sintering. The ARATP was obtained through anchoring nano-Fe3O4 on attapulgite (ATP), and its micro nano-structures can be adjusted by varying Fe3O4 content. Molecular dynamic simulations revealed the benefits of Fe3O4 in constructing superwetting coating layer with oil droplet repulsion larger than 227 KJ·mol−1. The membrane exhibited underwater superoleophobicity (with underwater oil contact angle at 157°) and was proven to treat various oil-water mixtures effectively (with a water permeation flux above 3249 L·m−2·h−1 and oil content in filtrate less than 2 mg·L−1). Furthermore, the chemical, mechanical stability and easy-cleaning property of the as-prepared membrane was demonstrated by different tests.

Mussel-Inspired Durable TiO2/PDA-Based Superhydrophobic Paper with Excellent Self-Cleaning, High Chemical Stability, and Efficient Oil/Water Separation Properties.

Oceanic oil spill and the discharge of industrial oily wastewaters can cause significant threats to the ecological environment and human health. Herein, we design a durable TiO2/PDA-based superhydrophobic paper for efficient oil/water separation. Bioinspired from mussel adhesive proteins, the mechanical durability of the as-prepared superhydrophobic paper is enhanced by the deposition of polydopamine (PDA) onto cellulosic fibers via self-polymerization of dopamine. The TiO2/PDA-based superhydrophobic paper shows a high water contact angle of 168.2° and an oil contact angle of ∼0°, exhibiting excellent superhydrophobicity and superoleophilicity. Furthermore, the as-prepared superhydrophobic paper possesses excellent chemical stability, thermal stability, and mechanical durability in terms of being immersed in corrosive solutions and solvents and boiling water and being subjected to the sandpaper abrasion test, respectively. More importantly, the separation efficiency of the TiO2/PDA-based superhydrophobic paper for an oil/water mixture is 97.2%, and it maintains a separation efficiency above 94.3% even after 15 cyclic separation processes. Furthermore, the separation efficiency for water-in-oil emulsions is higher than 93.7% after 15 cyclic separation tests, showing its excellent recyclable stability for water-in-oil emulsions. Therefore, the rationally designed TiO2/PDA-based superhydrophobic paper shows great potential in the practical applications of self-cleaning, antifouling, and oil/water separation.

Surface modification of phosphogypsum and application in polyolefin composites.

Phosphogypsum (PG) is one of solid wastes with large amount of yield and serious pollution, which has attracted wide attention. The aim of this study is to investigate filling performance of PG on polypropylene (PP) or high-density polyethylene (HDPE) matrix. In this work, PG was calcined initially to improve whiteness and fix impurities. X-ray diffraction (XRD) results showed that after calcined at 500°C, the PG phase changed from CaSO4·2H2O to CaSO4. The modification effects of the three modifiers were evaluated by Fourier transform infrared spectra (FTIR), oil absorption value, water floatability, and contact angle analysis. The effects of weight fraction of PG in PP and HDPE matrix on mechanics and morphology were observed by tensile test, impact test, and scanning electron microscope. Scanning electron microscope (SEM) showed that modified PG can be dispersed uniformly in the matrix at low filling content. With the increase of PG filling content, the analysis of mechanical properties showed that the tensile strength of HDPE matrix increased, while the tensile strength of PP matrix decreased gradually. The impact strength of HDPE matrix would decrease, but the impact strength of PP matrix increased first and then decreased. Compared with calcium carbonate (CC), the mechanical properties of HDPE filled with PG performed better. The apparent density showed that polymer composites filled with PG have the characteristics of light weight.

Superwetting sea urchin-like BiOBr@Co3O4 nanowire clusters-coated copper mesh with efficient emulsion separation and photo-Fenton-like degradation of soluble dye

The development of superwetting materials for the separation of oily wastewater and emulsified oil/water mixtures has been accelerated to handle the ever-increasing oil spills from industrial and sanitary wastewaters that contain organic contaminates (e.g., dyes). Herein, sea urchin-like BiOBr@Co3O4 nanowire clusters were fabricated on the copper mesh substrates via combination of hydrothermal synthesis and calcination of Co3O4 nanowire clusters, and hydrothermal deposition of a BiOBr photocatalyst. Such a hierarchical nanostructure composite membrane acquired superhydrophilicity and underwater superoleophobic properties, and consequently presented excellent self-cleaning and anti-fouling with an underwater oil contact angle of 160.6 ± 2°. The membrane had high emulsion separation efficiency and permeation flux for both surfactant-free (≥99.98%, up to 4656.33 L·m−2·h−1) and surfactant-stabilized oil-in-water emulsions (≥98.66%, up to 887.67 L·m−2·h−1). Moreover, the deposition of BiOBr enhanced the photo-Fenton-like catalytic activity so that the membrane could degrade ≥96.0% methylene blue (50 mL, 10 ppm) within 60 min under visible light irradiation. Furthermore, the as-fabricated superwetting mesh membrane demonstrated great reusability as well as good mechanical and corrosion resistance when exposed to harsh environmental conditions. Thus, this study presents a novel high-performance superwetting material with great potential in efficient removal of insoluble and soluble organic contaminants from oily wastewater.

Superhydrophobic polypropylene/ethylene-propylene-diene terpolymer thermoplastic vulcanizates for continuous oil-water separation

Although the construction of superwettability materials for oil-water separation has become a research hotspot, it is still a thorny issue due to its easy pollution to the environment during the preparation process. In this paper, we reported the functional PP/EPDM TPV film (with a contact angle of oil and water is 0° and 157.9±2.9°) as superhydrophobic and superoleophilic materials with reproducible processing characteristics at high temperature; moreover, during the molding process the etched aluminum foil was used as a template for the preparation of functional TPV film which was used in the efficient separation treatment of oily wastewater. It should be noted that a novel method was proposed for the continuous oil-water separation via a pressure response through valve, which was different from the traditional gravity-driven method and the permeable oil-water separation. The flexible PP/EPDM TPV film was rolled up and loaded into the through valve and the gap between films was used as the pressure response channel of oil-water separation. The novel functional TPV film used in the continuous oil-water separation was recyclable, environmentally friendly, and easy to industrialize, indicating the great potential in practical applications.

A durable biomimetic superhydrophilic/underwater superoleophobic fabric bed for highly efficient emulsion separation

A superhydrophilic/underwater superoleophobic fabric was fabricated via an immersion process in buffer solution of gallic acid (GA) and polyethyleneimine (PEI) and a short-term complexation process with cupric ions (Cu2+). The fabric shows superhydrophilicity with a water contact angle (WCA) of 0° and underwater superoleophobicity with an underwater oil contact angle (UWOCA) of 162.2 ± 2.4°. Its superwettability can be kept after harsh acid/base/salty treatment, 1000 g sand impact and 50 cycles of tape-peeling, demonstrating outstanding chemical and physical durability. A fabric bed constructed by as-prepared fabrics was used for separating surfactant-stabilized toluene/isooctane/petroleum ether/1,2-dichloroethane-in-water emulsions, with separation efficiencies all over 99.1%. The separation efficiency could be retained above 99.1% after repeated separation, indicating excellent reusability of the fabric bed.

Super-hydrophobic/super-oleophilic carbon nanofiber-embedded resorcinol-formaldehyde composite membrane for effective separation of water-in-oil emulsion

A super-hydrophobic/super-oleophilic carbon nanofibers (CNFs)-embedded resorcinol-formaldehyde (RF)-activated carbon fiber (ACF) composite membrane is synthesized for the efficient removal of water from a water-oil emulsion. Chemical vapor deposition (CVD) with copper oxide (CuO) as the catalyst is used to form CNFs for the first time over an ACF-supported RF polymeric layer. The prepared CuO–CNF/RF-ACF membrane was physicochemically characterized as super-hydrophobic/super-oleophilic (water contact angle 157° and oil contact angle 0°), attributed to the high surface roughness (Ra ∼55.56 nm) and graphitic content of the CNFs. The membrane had an asymmetric internal structure with a hydrophobic CNF-decorated microporous surface, which facilitated oil to pass and rejection of water droplets from the emulsion. The dead-end separation test data indicated a flux of 426 ± 20 L/m2-h with the water removal efficiency of 99.7% and the permeate having water droplets with the size range of 37–78 nm when tested against a water-oil emulsion of 10% (v/v) comprising 700–1700 nm sized water droplets. The physicochemical characterization, including the tests under harsh conditions showed the material mechanically, thermally, and chemically stable. The method described in this study to synthesize CuO–CNF/RF-ACF membrane is facile and has a potential for scale-up.

High-efficiency oil-water separation and passive radiant cooling performance of nano-ZnO- embedded dust-free paper

Developing a flexible nano-composite material which is not only impermeable to low-polar oil, but also has the ability of daytime radiation cooling, remains a huge challenge for both academia and industry. By modifying the fiber network of the dust-free paper using nano-ZnO particles (ZnO-DF), we strategically designed and demonstrated dual capabilities of superhydrophilicity/superoleophobicity and daytime radiant cooling for the flexible cellulose nano-composite simultaneously. A superior surface with superhydrophilic/superoleophobic (oil contact angle up to 159° and water contact angle down to 0°) was attained by regulation of surface energy components and roughness. Furthermore, the materials revealed outstanding corrosion and mechanical damage resistance, 152,788 L m−2 h−1 high permeation flux and >99.2% continuous and efficient oil-water separation performance. In addition, a cooling effect of about 5.6 °C of ZnO-DF paper could be achieved by cooperative function of both radiative cooling and sweat evaporation. It is expected that the ZnO-DF paper is promising for the thermal management of wearable products integrated with passive radiant cooling, phase change cooling (e.g., sweat evaporation) and large-scale industrial oil-water separation.

Wetting stability of flexible superamphiphobic surfaces under stretching loading

Wetting stability is important for superamphiphobic surfaces used in oil–water environments. Maintaining the wetting stability of flexible superamphiphobic surfaces under stretching is challenging. Here, flexible surfaces with stable superamphiphobicity under stretching were fabricated by covering flexible polydimethylsiloxane substrates with superamphiphobic powders. Superamphiphobic powders composed of micro- and nanoparticles were prepared by a chemical substitution reaction and modification treatment. The fabricated flexible surfaces possessed contact angles for water, kerosene and peanut oil of 155, 152 and 153°, respectively, exhibiting superhydrophobicity and superoleophobicity. The self-cleaning properties of the fabricated flexible surface were studied by removing contaminants from the surfaces using water and oil droplets. Also, the wettability and morphology of the fabricated flexible surface under stretching were investigated. It was found that the fabricated flexible surface maintained stable superhydrophobicity and superoleophobicity when the stretching strain reached 60% due to the fact that it still kept micro–nano double-scale structures after being stretched. The fabricated flexible surface coated with superamphiphobic powders with wetting stability is expected to be used in the field of liquid repellency.

Waste-derived carbon fiber membrane with hierarchical structures for enhanced oil-in-water emulsion separation: Performance and mechanisms

A superhydrophilic and underwater superoleophobic membrane based on waste-derived carbon fibers was prepared with the assistance of tannic acid and (3-Aminopropyl)triethoxysilane. The surface morphology, chemistry, roughness and wettability of the membranes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy, water contact angle (WCA) and underwater oil contact angle (UWOCA) measurements, respectively. Carbon fibers enabled the construction of micro-nano hierarchical structures on the membrane surface, which significantly increased the membrane surface roughness (2.1 times higher than the control) and effective surface area (1.6 times higher than the control). The carbon fiber membrane exhibited superhydrophilicity (WCA = 0°) with ultrafast water spreading in air and underwater superoleophobicity (UWOCA = 157.2°) with little oil adhesion. The carbon fiber membrane showed effective surfactant stabilized oil-in-water emulsion separation using various oils (permeation flux up to 713 Lm-2h-1 and separation efficiency up to 99.8%). We also proposed an integrated model to elucidate how the superhydrophilic and underwater superoleophobic property and surface roughness interact with the size exclusion mechanism by considering dynamic flows near the membrane surface, which further reveals the anti-fouling and self-cleaning properties of our carbon fiber membrane. Our model provides new insights into developing specially-wettable membranes with high fouling resistance for wide wastewater treatment applications based on surface wettability and roughness.

Preparing a wettability-controllable stainless-steel mesh and its oil–water separation performance

The ability to regulate and apply surface wettability has attracted much attention in the surface engineering field. In this study, a simple chemical etching method was used to construct a rough micro/nano structure on 304 stainless steel mesh; this rough surface was subsequently decorated with fatty acids of varying chain length to regulate wettability. The wettability, composition, and morphology of the surface were characterized and analyzed by measuring contact angles, and by atomic force microscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy . The superhydrophobic and superoleophilic properties of the mesh modified with long-chain fatty acids were examined for oil-water separation performance and reusability. The surface had a micro/nano hierarchical morphology with ordered carbon chains, and the hydrophilic-to-superhydrophobic transformation was achieved by adjusting the chain length of the fatty acid to deliver contact angles in the range of 30°~154°. The oil contact angle was always 0°, irrespective of the chain length fatty acid, and oil drops quickly penetrated the mesh surface. A fatty acid with a longer chain afforded a more hydrophobic and oleophilic mesh surface and better oil–water separation efficiency (up to 96%), which still exceeded 85% after 50 cycles of oil–water separation testing. Consequently, the prepared surface with controllable wettability has excellent prospects for use in intelligent response interfaces and oil–water separation applications.

Zwitterionic polyvinylidene fluoride membranes with strong underwater superoleophobicity and oil-fouling resistance for oily water purification

Polyvinylidene fluoride (PVDF) membrane offers excellent potential for efficient separation and purification of O/W emulsions. However, oil-fouling presents a major obstacle to its further application. Herein, a strong underwater superoleophobic surface was engineered to efficiently inhibit oil-fouling. PVDF-graft-poly(2-(dimethylamino) ethyl methacrylate) (PVDF-g-PDMAEMA) membranes were first fabricated via vapor-induced phase separation (VIPS), in which the nascent liquid film was left in a vapor bath for a predesigned time (te). The surface roughness increases by an order of magnitude when te increases from 0 to 240 s, and the underwater oil contact angle (UWOCA) correspondingly increases to more than 150°. However, it declines with time gone until the oil droplets on the underwater membranes were swallowed up. After surface zwitterionicalization by the reaction between PDMAEMA and 1, 3-propane sulfonate, a strong underwater superoleophobic surface was obtained, even after being soaked in water for 24 h. It endows the zwitterionic membrane with superior crude oil/water emulsion separation (with a flux of 749.7 ± 44.8 L m−2 h−1 and separation efficiency of 99.4 ± 0.1%) and excellent oil-fouling resistance (with a flux recovery rate of more than 90%), improving the potential value of porous membranes in oily water treatment.

Superhydrophilic photocatalytic g-C3N4/SiO2 composite membranes for effective separation of oil-in-water emulsion and bacteria removal

Conventional membrane processes, e.g., microfiltration and ultrafiltration, suffer from severe permeation flux decline and fouling during the oily wastewater treatment. The superhydrophilic surface decoration provides an important and effective strategy to address this challenge. Herein, a surperhydrophilic/underwater superoleophobic nanocomposite surface with the photocatalytic properties was constructed via one-step facile vacuum-assisted filtration of a g-C3N4 nanosheet/SiO2 nanoparticle dispersion onto a microfiltration membrane substrate. Specifically, with the intercalation of 20 mg∙L−1 SiO2 nanoparticles into the g-C3N4 nanosheets, the g-C3N4/SiO2 composite membrane showed the superhydrophilic/underwater superoleophobic properties with an underwater oil contact angle of 170.0 ± 0.3°. Such a g-C3N4/SiO2 composite membrane yielded a permeation flux of >1290 LMH·bar−1 with an oil rejection of >99.91% during the vacuum filtration of oil-in-water emulsions. The g-C3N4/SiO2 composite membrane significantly outperformed the pristine microfiltration substrate that had severe fouling caused by oil blockage. Additionally, the g-C3N4/SiO2 composite membrane not only effectively retained the E. coli bacteria through size exclusion effect, but also promoted the inactivation of bacteria via visible-light photocatalysis. Therefore, our membrane has a great promise in practical oily wastewater treatment due to its excellent separation performance and biofouling resistance.