Effective Oil-water Separation Research Articles

Development of superhydrophobic PVA/CNC nanofibrous membranes for enhanced oil-water separation

Effective oil–water separation is crucial for environmental purification and the remediation of oil pollution, yet current methods face limitations in efficiency, durability, and environmental impact. In this study, we aimed a green nanofibrous membrane with excellent oil–water separation efficiency, addressing the significant environmental challenge of separating oil from water in various states. For this purpose, polyvinyl alcohol (PVA)-based nanofibers were prepared by aqueous electrospinning. The mechanical strength of the nanofibers was reinforced by adding cellulose nanocrystals (CNCs). The surface of the nanofibers was modified with hexadecyltrimethoxysilane (HDTMS) to induce hydrophobicity, evidenced by the increase in contact angle from 44.41° to 133.19°, facilitating effective oil separation from various states, including dispersed, suspended, and emulsified states. The prepared PVA/CNC-HDTMS nanofiber showed 194 %, 539 %, and 407 % higher tensile strength, yield strength, and Young’s modulus than PVA nanofibers, respectively. The oil sorption capacity of the nanofibers varied widely from 17.01-113.76 g/g, which is strongly influenced by the viscosity and volatility of the oil species. The durability and reusability of the nanofibers were well maintained, even after being reused more than 10 times without morphological deterioration. In separating oil–water mixtures, the nanofibers maintained a high flux of 40,039 L/m2h and a separation efficiency of 99.2 % under pressurized conditions. Additionally, the nanofibers achieved a separation efficiency of 98.5 % in oil–water emulsion states.

Polystyrene Nanofibrous Membrane Infused with TiO2 Nanoparticles by a One-Step Electrospinning Process for Effective Oil–Water Separation

Polystyrene Nanofibrous Membrane Infused with TiO₂ Nanoparticles by a One-Step Electrospinning Process for Effective Oil–Water Separation

Superhydrophobic Stainless Steel Mesh through Chemical Vapour Deposition of TMCS for Effective Oil-Water Separation

Aim: To Fabricate the superhydrophobic Stainless Steel (SS) mesh using Trimethylchlorosilane (TMCS) through a Chemical Vapor Deposition (CVD) method for the oil-water mixture separation Background: The frequent oil spills have a devastating impact on marine ecosystems and the environment. The porous materials with superhydrophobic properties have been created to separate oil and water effectively. Due to their ability to effectively separate oil and water, superhydrophobic coatings have gained significant attention. Methods: The cleaned stainless-steel mesh was put on a stand and covered with a glass container. Within the container, 50 mL of hexane, which contained 1 mL of TMCS, was added. The mesh was then left for 3 h to undergo the CVD process Results: The silane content with low surface energy creates a highly rough structure on the mesh surface. The optimal mesh coating is superhydrophobic, having a strong affinity to oil and a water contact angle of 162 ± 2°. The coated mesh has shown a separation efficiency of over 97.8% for different oil-water mixtures. The coatings sustain their superhydrophobicity up to 30 tape peels and 40 times sandpaper abrasion, indicating good mechanical durability. Conclusion: The study concludes that the S-3 sample is mechanically stable and can withstand various tests such as adhesive tape peeling, sandpaper abrasion, bending, folding, and twisting. It efficiently separates oil and water mixtures on a large scale with high efficacy

Graphene-based aerogel for efficient oil sorption and water pollution remediation

In the past few years, there has been a notable rise in the release of industrial waste oil, frequent oil spills at sea, and a significant escalation in the severity of water pollution. This issue has garnered global attention and is now recognised as a widespread concern. Hence, there is a pressing demand for an oil-absorbing material exhibiting high oil-absorption capabilities and robust mechanical properties. This study introduces a new aerogel characterised by a three-dimensional hierarchical pore size structure derived from natural corn stalk powder and graphene oxide (GO). The developed aerogel demonstrated notable sorption capacity ranging from 70.6 to 131.0 g/g, along with excellent compressibility and high elasticity. These properties enable effective oil-water separation and selective sorption. This study introduces a novel approach to treating agricultural waste and presents a straightforward, environmentally friendly, cost-effective method for synthesising high-performance graphene-based oil-absorbing agents.

Sustainable waste valorization: hydrophobic sponge from coconut fibers and expanded polystyrene for effective oil–water separation

Sustainable waste valorization: hydrophobic sponge from coconut fibers and expanded polystyrene for effective oil–water separation

Magnetic Hyperporous Elastic Material with Excellent Fatigue Resistance and Oil Retention for Oil-Water Separation.

Oily wastewater has caused serious threats to the environment; thus, high-performance absorbing materials for effective oil-water separation technology have attracted increasing attention. Herein, we develop a magnetic, hydrophobic, and lipophilic hyperporous elastic material (HEM) templated by high internal phase emulsions (HIPE), in which free-radical polymerization of butyl acrylate (BA) and divinylbenzene (DVB) is employed in the presence of poly(dimethylsiloxane) (PDMS), lecithin surfactant, and modified Fe3O4 nanoparticles. The adoption of the emulsion template with nanoparticles as both stabilizers and cross-linkers endows the HEM with biomimetic hierarchical open-cell micropores and elastic cross-linked networks, generating an oil absorbent with outstanding mechanical stability. Compressive fatigue resistance of the HEM is demonstrated to endure 2000 mechanical cycles without plastic deformation or strength degradation. By exploiting the synergistic effect of hierarchical structures and low-surface-energy components, the resulting HEM also possesses excellent and robust hydrophobicity (water contact angle of 164°) and good oil absorption capacity, in which Fe3O4 nanoparticles lead to convenient magnetically controlled oil recyclability as well. Notably, the unique biomimetic microporous structure demonstrates superior oil retention capacity (>95% at 1000 rpm and >60% at 10,000 rpm) over the state-of-the-art porous materials for a diverse variety of oils to reduce the risk of secondary oil leakage, along with good recoverability by squeezing owing to the excellent compression resilience. These excellent performances of our HEM provide broad prospects for practical applications in oil-water separation, energy conversion, and smart soft robotics.

Fluorine-free preparation of superhydrophobic polyester fabric with directional moisture transport for efficient oil-water separation

Since the negative impact of fluorinated substances on human health and the environment, fluorine-free superhydrophobic surfaces are the alternative approach that has received growing attention and progress. Herein, a fluorine-free superhydrophobic polyester fabric (D4H-PF) with directional moisture transport was facilely fabricated through plasma-induced polymerization of octamethylcyclotetrasiloxane (D4) for efficient oil-water separation. To obtain asymmetric wettability, a hydrophilic finishing agent (HFA) was sprayed on the other side of the polyester fabric. After plasma treatment, the water contact angle (WCA) of the polyester fabric has been significantly enhanced from 79° to 153.31°, thereby achieving superhydrophobicity. The directional moisture transport endowed D4H-PF with an efficient oil-water separation efficiency for both light oil/water mixture (98.88%) and heavy oil/water mixture (92.24%). Meanwhile, the D4H-PF has high permeation fluxes of 4968.15 L/(m2·h) and 4872.61 L/(m2·h), respectively. Meanwhile, D4H-PF showed suitable mechanical stability, acid-base tolerance, and washability for practical application. Therefore, D4H-PF with directional moisture transport service is a promising potential candidate for sustainable and effective oil-water separation. This study not only extends the application scope of plasma but also offers useful insights into the designing of eco-friendly superhydrophobic surfaces.

Facile preparation of UiO-66-NH2-coated mesh membrane with underwater superoleophobicity for high efficiency oil-water separation

The metal organic framework (MOF) polycrystalline membranes on stainless steel mesh (SSM) are urgently required for effective oil-water separation, but the affordable preparation still remains a challenge. Herein, we report a series of UiO-66-NH2/SSM films, which are developed by a rational ‘seeding-assisted secondary growth’ method. Results depict that the proposed method greatly shortens the synthesis time, and helps to achieve a continuous and uniform modification of UiO-66-NH2 on SSM, and hence contributes to a superior hydrophilicity and superoleophobicity for UiO-66-NH2/SSM with minimum water contact angle of 32° and maximum underwater oil contact angle of 150°, respectively. Specifically, the UiO-66-NH2/SSM-600–2 has total permeation fluxes and separation efficiencies of ca. 8.4×104 L·m−2·h−1 and 100% for the n-hexane-, petroleum ether- and chloroform-water emulsions (1% volume ratio), which exceed numerous polycrystalline membranes reported so far. It also exhibits a great durability with only 0.1% loss of separation efficiency after 8 cycles. Furthermore, outstanding acid-resistivity and salt-tolerance are also presented. Our work supplies a new strategy to construct UiO-66-NH2/SSM, and the decent properties confirm a huge potential for practical use in oil-water separation.

An eco-friendly and facile method for oil-water separation using the bio-Zn oxide-based superhydrophobic membrane.

This manuscript presents a novel approach for developing an environmentally friendly and effective oil-water separation membrane. Achieving a superhydrophobic (SH) coating on textile fabric (TF) involved a two-step process. Initially, the surface roughness was enhanced by applying bio-zinc oxide (ZnO) nanoparticles obtained from Thymbra spicata L. Subsequently, the roughened surface was modified with stearic acid, a material known for its low surface energy. The bio-ZnO nanoparticles exhibit a circular morphology with an average size of 21 nm. The coating demonstrated remarkable mechanical stability, maintaining SH properties even after an abrasion length of 300 mm. Chemical stability studies revealed that the prepared membrane retained SH properties within a pH range of 5-11, which ensures robust performance. Absorption capacity measurements showcased different capacities for n-hexane (Hex), corn oil (C.O), and silicone oil (S.O), with consistent performance over 10 absorption-desorption cycles. High oil-water separation efficiencies were achieved for hexane, C.O, and S.O, emphasizing the coating's versatility. Flux rate measurements demonstrated that oil passed through the membrane efficiently, with the highest flux observed for Hex. The prepared SH membrane has superior mechanical and chemical stability and high separation efficiencies, which positions it as a promising candidate for diverse industrial applications.

Mussel-inspired fabrication of fouling-resistant PPSU-based nanocomposite membrane using polydopamine and tannic acid-functionalized CeO2 nanoparticles towards effective oil-water emulsions separation

Surface modification of membranes using hydrophilic nanoparticles has proved promising to improve the surface wettability and antifouling properties of the membranes that are otherwise prone to the attachment of oil droplets. Nonetheless, the strong adhesion of nanoparticles onto the membrane surface and their long-term performance pose problems for their widespread application. To address these issues, a novel organic-inorganic hybrid coating was constructed onto surfaces of polyphenylsulfone (PPSU) ultrafiltration membrane via simultaneous deposition of mussel-inspired polydopamine (PDA) followed by immobilization of tannic-acid functionalized cerium oxide (CeO2) nanoparticles. These prepared membranes were characterized by FTIR, XPS, FESEM, EDX, pore size, water contact angle (WCA), underwater oil contact angle (UOCA), and separation performance. The effects of functionalization and nanoparticle concentration on membrane properties were investigated. SEM and EDX results showed that functionalized nanoparticles (up to optimum concentration: 0.05 wt%) were uniformly distributed onto the membrane surface, which exhibited increase in permeate flux (∼375 %), UOCA (∼36 %), Fouling resistance ratio (FRR ∼ 300 %) with a decrease in irreversible fouling (∼94 %) and WCA (∼80 %) and high oil rejection of > 99 % compared to pristine PPSU membrane. Long-term operation (for six cycles) indicates that the optimum membrane possessed high efficiency and durability for oil-in-water emulsion separation due to superb antifouling properties and strong binding of the functionalized nanoparticles onto the membrane surface.

Application of MOF-based membrane in oil-water separation

In addition to being a serious threat to human health and the natural environment, the rising volume of oily wastewater and oil spills also causes resource depletion. Thus, there is a lot of interest in effective oil-water (O/W) separation. Scientists have looked at and suggested a variety of creative separation techniques in an attempt to address this issue. Unfortunately, the majority of these techniques have technical issues with low separation efficiency and significant energy usage. It is crucial to develop an effective oil-water separation membrane in order to address this issue. Because of their large surface area, low density, high porosity, controllable wettability, and variable pore size, have a lot of potential in this sector. This paper first categorizes several different MOF-based membranes and describe in detail their different synthesis methods, including solvent thermal method, ultrasonic method, microwave method, etc. Then, the physicochemical properties of MOF-based films are summarized in detail. The mechanism by which MOF-based films can separate oil-water mixtures is also explained. Finally, the modification of stainless steel mesh, sponge, aerogel and filtration membranes by MOF-based films, respectively, is emphasized and their applications in O/W separation are discussed.

Trabecular bone-inspired tung oil-derived spongy cellular networks with intelligent pH-responsive wettability and superelasticity for efficient multitasking separation

Development of new biomass sponges with controllable wettability and excellent resilience is urgent while challenging for multitasking and effective oil–water separation because incorporating these performances into conventional biomass sponges is complicated and even contradictory. Herein, a hypersalinity-confined thermopolymerization strategy is presented for fabricating the tung oil-derived spongy cellular network (TSN), during which its interconnected porous skeleton with ionizable carboxyl groups is formed due to the self-initiated thermal polymerization and crosslinking of tung oil precursors enclosed in the stacking space of sodium chloride (NaCl) particles. By mimicking trabecular bone architecture with good energy transfer/dissipation, high porosity and strong capillary absorption, the resultant TSN with carboxylic acid groups exhibits reversible pH-responsive wettability (transition from hydrophobicity/lipophilicity to hydrophilicity/oleophobicity), superelasticity (nearly 100 % stress and height retention after 1000 cycles), good thermal/chemical stability and efficient oil–water separation performance (>99.4 % separation efficiency) in multitasking situations. This study provides an encouraging insight for the tailored fabrication of smart sponge materials derived from renewable vegetable oils for oil–water separation in multitasking and complex situations.

Facet engineering of minerals for effective oil-water separation

Minerals have been growing as an emerging ‘hot’ topic in separating water-in-oil emulsions. Whether the intrinsic structure of minerals could precisely regulate water–mineral interactions for enhancing emulsions separation efficiency is still ambiguous. Here, taking half-hydrated gypsum as a case, this study reveals the crystal facet-dependent potential mechanism of minerals in water-in-oil emulsions separation. We show that the (204) facet of half-hydrated gypsum is more susceptible to water-induced degradation and hydration reaction. With combined experimental and theoretical studies, the facet-dependent mechanism for oil–water separation are revealed; the (204) facet that exhibited weak internal hydrogen bond and strong binding energy with water accelerated the dissolution and recrystallization of half-hydrated gypsum, thus enhancing oil–water separation efficiency. Through engineering, half-hydrated gypsum with a higher surface fraction of the (204) facet achieved much higher separation efficiency (99.9%), surpassing those of minerals in disclosed literature. This investigation not only contributes significantly to the comprehension of interactions at the minerals-water interface but also illuminates novel perspectives and avenues for the utilization of facet engineering in advancing research on mineral surface properties.

Highly efficient sorbent utilizing regenerated cellulose as an eco-friendly template for humic acid removal and oil–water separation processes

In this study, a novel and environmentally friendly sorbent was developed utilizing regenerated cellulose (RC) as a renewable resource. The preparation process of the regenerated cellulose hydrogel, following a bottom-up strategy, occurs in an aqueous system and offers the added benefits of temperature-induced gelation and solvent recyclability. The RC/PEI aerogel was prepared through a polyethyleneimine (PEI) modification and di-epoxide crosslinking process, which improves the gel's elastic recovery for the squeezing process and concurrently provides excellent ability to remove humic acid (HA) contaminants. As a result of the HA removal experiment using the RC/PEI aerogel in an aqueous environment, the gel showed an experimental HA adsorption capacity of 124.9 mg/g and qm value of 196.7 mg/g. Furthermore, the prepared RC hydrogel template was successfully transformed into a highly effective oil–water separation sorbent through a hydrophobic alkylated graphene oxide (AGO) coating process. Oil-water separation was carried out using AGO-RC/PEI gel, and it was possible to successfully adsorb the oil and then recover it through the squeezing process. In addition, long-term usability has been validated by demonstrating an oil adsorption capacity of over 84 %, even after ten consecutive reuses.

Simple preparation of UV-absorbing and magnetic superhydrophobic membranes by one-step electrospinning for effective oil–water separation

Developing multifunctional separation membranes, especially composite separation membranes that are corrosion-resistant, fouling-resistant, and easy to collect, has become a new challenge to treating oily wastewater in complex environments. Therefore, superhydrophobic magnetic membranes composed of polystyrene/poly(acrylonitrile)-poly(vinylidene fluoride)/poly(dimethylsiloxane)-iron oxide/titanium dioxide nanoparticles (PS/PAN-PVDF/PDMS@Fe3O4/TiO2), which possess exceptional corrosion resistance and UV absorption properties, were fabricated through the process of electrospinning. Controlling the doping ratio of Fe3O4/TiO2, composite membranes with excellent superhydrophobicity (156.9°), mechanical properties (3.67 MPa and 75.93 %), and thermal stability (330 °C) were obtained. The membrane demonstrates outstanding corrosion resistance (WCA > 150°) even after being immersed in various corrosive solutions for 120 h. Under visible-ultraviolet irradiation, the membrane has excellent UV absorption and exhibits a significant red-shift phenomenon, providing a certain degree of resistance to fouling. In the presence of a magnetic field, the membrane has a maximum saturation magnetization of 9.98 emu/g, which the magnetic field drive can attract. The oil adsorption capacity of the membrane was 29–112 g/g, which also maintained 88 % of the initial value after ten cycles. In addition, a comprehensive evaluation was conducted to assess the fabricated composite membrane's separation flux, efficiency, and cycle life when exposed to acidic and alkaline corrosive solutions. The results indicated that even after 40 cycles, the membrane's oil–water separation flux and separation efficiency remained at 6971 L.h−1.m−2 and 97 %, respectively, representing a 24.2 % increase compared to the unmodified membrane. Therefore, the membrane exhibits promising potential for treating oily wastewater in harsh environments.

Facile Coaxial Electrospinning Synthesis of Polyacrylonitrile/Cellulose Acetate Nanofiber Membrane for Oil-Water Separations.

Oil-contaminated water and industrial oily wastewater discharges have adversely affected aquatic ecosystems and human safety. Membrane separation technology offers a promising solution for effective oil-water separation. Thus, a membrane with high surface area, hydrophilic-oleophobic properties, and stability is a promising candidate. Electrospinning, a straightforward and efficient process, produces highly porous polymer-based membranes with a vast surface area and stability. The main objective of this study is to produce hydrophilic-oleophobic polyacrylonitrile (PAN) and cellulose acetate (CA) nanofibers using core-shell electrospinning. Incorporating CA into the shell of the nanofibers enhances the wettability. The core PAN polymer improves the electrospinning process and contributes to the hydrophilicity-oleophobicity of the produced nanofibers. The PAN/CA nanofibers were characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction, and surface-wetting behavior. The resulting PAN/cellulose nanofibers exhibited significantly improved surface-wetting properties, demonstrating super-hydrophilicity and underwater superoleophobicity, making them a promising choice for oil-water separation. Various oils, including gasoline, diesel, toluene, xylene, and benzene, were employed in the preparation of oil-water mixture solutions. The utilization of PAN/CA nanofibers as a substrate proved to be highly efficient, confirming exceptional separation efficiency, remarkable stability, and prolonged durability. The current work introduces an innovative single-step fabrication method of composite nanofibers, specially designed for efficient oil-water separation. This technology exhibits significant promise for deployment in challenging situations, offering excellent reusability and a remarkable separation efficiency of nearly 99.9%.

A facile approach for oil-water separation using superhydrophobic polystyrene-silica coated stainless steel mesh bucket

Inspired by traditional shaduf technology in the irrigation field, we fabricated a superhydrophobic stainless steel mesh bucket by layering polystyrene and SiO2 nanoparticles through a facile dip coating technique for effective oil-water separation. The superhydrophobic steel mesh bucket could effectively lift oil as well as microplastic pollutants from the water surface. The water contact angle of a two-layered polystyrene-silica coating was 158.5° ± 2°, while the oil contact angle was nearly 0°. The oil-water separation performance of superhydrophobic mesh was tested using several kinds of oil. The separation efficiency achieved for low viscous oil was 99.33 %, while 86.66 % efficiency was recorded for high viscous oil. The superhydrophobic mesh showed high durability against mechanical tests including bending, folding, twisting, adhesive tape tearing (25 cycles), and sandpaper abrasion (20 cycles). The mesh presented admirable thermal and chemical durability. The present superhydrophobic steel mesh bucket is a suitable candidate for large-scale application.

Fabrication of plasma-treated superhydrophobic polydimethylsiloxane (PDMS) – Coatėd melamine sponge for enhanced adhesion capability and sustainable oil/water separation

A persistent global issue is the need for developing novel absorbent materials with high absorption efficacy and rapid absorption rates for effective oil–water separation. This work presents a novel, resilient, and recyclable material with exceptional sorption capabilities, achieved through a simple surface modification of melamine sponge (MS) using Argon plasma treatment followed by Polydimethylsiloxane (PDMS) polymer coating (Ar-PT/PDMS@MS). This study also delineates the choiceful impact of atmospheric and vacuum plasma over the surface modification of MS. The material's super hydrophobicity, demonstrated by a high-water contact angle of ∼165°, is enhanced using novel plasma treatment to homogenously coat PDMS polymer. This treatment also imparts sturdiness to withstand harsh environmental conditions. The modified 3D networked structure of melamine sponge with a porous core was able to selectively absorb the oil of various densities with the capacity range of 42–139.5 mg/g. The batch and continuous O/W separation studies revealed the efficiency of the modified MS to be able to selectively separate light nonaqueous phase liquids (LNAPL) and dense nonaqueous phase liquids (DNAPL) oil with more than 99% efficiency. The continuous studies showed that using diesel oil the separation efficiency was >99% for 35 L of oil for more than 5 h. It was also discovered that it outperformed and exceeded commercial absorbent materials in terms of absorption capacity. The recyclability studies highlighted the ability of the modified MS to be used for more than 10 cycles without compromising its separation efficiency. These findings may foreshadow Ar-PT/PDMS@MS's ability to be a promising antagonist for oil–water (O/W) separation in real-world oil-spill scenarios.

High-efficiency oil/water separation by simple fabrication of superhydrophobic nanocomposite (Zno-SiO2) coating mesh

Environmental sustainability and human health are globally imperilled by oil-contaminated water resulting from oil spill disasters or industrial disposal. Superhydrophobic materials have gained increasing attention in oil–water separation to fulfil the ever-growing need for highly effective oil–water separation. Due to the regeneration ability of silicon dioxide nanoparticles (SiO2), superhydrophobic/superolephilic nanocomposite (ZnO-SiO2) was created using a new, simple flame treatment procedure. ZnO(NRs) was coated on stainless steel mesh via water bath deposition method and modified with silicon rubber ( RTV-SR) solution. The mesh coated exhibited an excellent superhydrophobic surface with water at a contact angle 168±1°, a sliding angle 3.5° and superolephilic with oil contact angle OCA (0°). The x-ray diffraction, contact angle measurement, field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS) were used to describe the coated mesh surface. Kerosene-water, diesel oil–water mixtures and sunflower oil–water are successfully separated by the simple filtering method using the coated mesh with a separation efficiency of 96%.

Nanostructured CFO@SiN-DICP-DHDA as a novel reversible magnetic gelator for the fast and effective oil–water separation: Toluene optimization by CCD approach

In the present work, a novel approach has been described for the synthesis of a durable and recyclable functionalized nanomagnetic gelator namely CoFe2O4@SiO2-NH2-1-5 di isocyanatopentane- di Hexadecylamine (CFO@SiN-DICP-DHDA). The nanocomposite was then used for efficient oil/diesel separation from water, a combination of organic solvents and oil that has rarely applied. CFO@SN-DICP-DHDA was characterized using various techniques, including Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), Vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and inverted microscopic and differential scanning calorimetry (DSC). The successful gelation of the oil leads to facile isolation of the gelator by an external magnetic field. Due to the remarkable oil separation capability, as well as the great mechanical and chemical stability of CFO@SiN-DICP-DHDA, it can tightly bind the organic and inorganic layers on the CoFe2O4 nanoparticles. The gelator demonstrates reproducible application for up to seven consecutive cycles without a significant reduction in performance. These outstanding results will pave the way for the removal of oil stains from water and the development of functional super magnetic gel materials. The initial maximum toluene uptake of ∼58 % was boosted to approximately ∼97.65 % through optimization using the central composite design (CCD) approach.