Oily Wastewater Treatment Research Articles

Recent progress of cotton fabric based on bio‐inspired modification for oil/water separation

AbstractWith the continuous development of the industry, oil spill accidents occur frequently. Oil/water separation materials are considered to be a major choice for the treatment of oily wastewater due to their flexible operation and low cost. Cotton fabrics are low‐cost and environmentally friendly, which are used as substrates to prepare oil/water separation materials with quite competitive in the market. A large number of oil/water separation cotton fabrics with excellent properties have been frequently reported in recent decades. On the other hand, since the service life of these oil/water separation cotton fabrics is closely related to the thin layer covered on the surface, so in order to improve the practical applicability, substances such as dopamine and plant polyphenols that improve the adhesion of the thin layer to the surface of the material are introduced into the preparation process of these materials. On this basis, the research progress of super‐hydrophobic cotton fabrics, super‐hydrophilic/underwater super‐oleophobic cotton fabrics, super durable oil/water separation cotton fabrics and intelligent response to oil/water separation fabric in recent years are reviewed, as well as their applications in the field of oil/water separation.

Combining Dissolved Air Flotation (DAF) and Modified Moving Bed Biofilm Reactors (MMBBR) for Synthetic Oily Wastewater Treatment

<p>Numerous industrial processes, including petroleum refining, food production, car washes, leather manufacturing, and slaughter houses, generate significant volumes of wastewater due to their substantial water consumption during processing. The presence of oily wastewater has detrimental effects on surface and ground water resources, Human health and aquatic ecosystems. This study aims to integrate dissolved air flotation (DAF) and moving bed biofilm reactors (MBBR) for the treatment of oily wastewater. For this reason, a synthetic oily wastewater was prepared by utilizing commercially available powdered starch as an organic source, along with diesel oil and a finely ground soil. In addition, the experiments were designed and analyzed using Response Surface Methodology (RSM). DAF reactor factors were flotation time and air flow rate. While the MBBR reactor variables were mixing time and hydraulic retention time (HRT). The responses were chemical oxygen demand (COD), oil and grease(O&G), ammonia (NH3-N) and total suspended solids (TSS). Optimum results obtained by RSM for the DAF were 10 min for the flotation time and air flow rate of 72 L/min. in addition, HRT for both MBBRs was 23.5 hr and mixing time of 13 min and 23 min for MBBR1 and MBBR2 respectively.</p>

Exceptional self-cleaning MXene-based membrane for highly efficient oil/water separation

Two-dimensional (2D) MXene-based separation membranes exhibit significant promise for oily wastewater treatment. The intercalation of TiO2 nanoparticles between MXene nanosheets can not only enlarge their interlayer distance for faster transportation of water molecules, but also promote their photocatalytic oxidation for removal of membrane fouling by oil droplets. However, the uniform loading of ultra-small TiO2 nanomaterials between MXene layers without aggregation is challenging. Herein, taking advantages of inherent Ti elements of MXene, we grew ultra-small TiO2 by in-situ one-step oxidation of MXene nanosheets to prepare 2D MXene@TiO2 heterojunctions. They were then loaded on polyethersulfone (PES) support by vacuum filtration for the PES-MXene@TiO2 composite membrane (MXTM) with exceptional water permeance and anti-fouling and self-cleaning properties. It achieves a remarkably high flux of 3045 L m−2 h−1·bar−1 and oil/water emulsion separation efficiency over 99.8%. Moreover, the MXTM membrane exhibits remarkable hydrophilicity, evidenced by an abrupt reduction in water contact angle from 43.8 to less than 5° within 10 s, which could retard the progress of oil adhesion on the membrane surfaces. The extended Derjaguin-Landau-Verwey-Overbeek theory confirmed high interaction energy between the membrane and pollutants. Furthermore, the MXTM membrane excels in self-cleaning and anti-fouling properties, retaining a flux recovery rate of >98% in 10 cycles by visible light driven photodegradation of foulants irradiation. This innovative 2D self-cleaning membrane offers excellent anti-fouling properties for efficient oil/water separation.

Study on the treatment of oily wastewater with non equilibrium plasma synergistic catalysts

Petroleum is currently a highly demanded power fuel, but oil fields produce oily wastewater during production. If not treated in a timely manner, it can cause serious ecological problems. To solve this issue, this article utilizes the non-equilibrium plasma generated by Dielectric Barrier Discharge (DBD) technology to treat diesel simulated oily wastewater under the synergistic effect of AC/Mn + TiO2 catalyst. The results indicate that: After 180 min of DBD treatment, the degradation rates of diesel and Tween-80 were 60.9% and 53.2%, respectively; after 180 min of synergistic DBD treatment with AC/Mn + TiO2 catalyst, the degradation rates of diesel and Tween-80 were 76.0% and 71.7%, respectively, with a significant increase in degradation rates. The SEM characterization of the catalyst before and after the reaction was compared, and it was found that the surface of the crystal after the reaction was smooth. XPS characterization showed that Mn electron migration leads to the generation of positively charged holes on the valence band of TiO2. These all demonstrate that the synergistic effect of DBD and catalyst promotes the degradation of oily wastewater.

Excellent coagulation performance of polysilicate aluminum ferric for treating oily wastewater from Daqing gasfield: Responses to polymer properties and coagulation mechanism

The polysilicate aluminum ferric (PSAF) was synthesized via copolymerization of polysilicic acid (PSi), AlCl3 and FeCl3 for treating oily wastewater from Daqing gas field. This study investigated the effects of key preparation factors such as the degree of PSi's preactivation and the ratio of (Fe + Al)/Si and Al/Fe on both polymerization and coagulation performance exhibited by PSAF. To determine the optimal timing for introducing Al3+ and Fe3+, zeta potential, viscosity and particle size were investigated. Additionally, infrared spectroscopy, X-ray powder diffraction, polarizing microscopy and scanning electron microscope analysis were employed to investigate the structure and morphology of PSAF. The results indicate that under conditions characterized by a SiO2 mass fraction of 2.5% and pH = 4.5, an optimal timing for introducing Al3+ and Fe3+ is at 100 min when PSi exhibits moderate polymerization along with sufficient stability. When considering molar ratios such as (Al + Fe)/Si being 6:4 and Al/Fe being 5:5, respectively, PSAF falls within a “stable zone” enabling storage period up to 32 days. Moreover, Jar test results demonstrate that at a dosage of 200 mg/L PSAF for oily wastewater treatment in gas fields could reach the maximum turbidity removal efficiency up to 99.5% while oil removal efficiency reach 88.6% without pH adjustment. The copolymerization facilitates the formation of larger PSAF aggregates with positive potential, thereby augmenting the coagulants' adsorption bridging and charge neutralization capabilities. As a result, PSAF has great potential as a practical coagulant for treating oil-containing wastewater in industrial settings.

Preparation of acrylate-cationic monomer block copolymers by RAFT and their flotation oil removal properties

With the development of oilfields, the liquid volume of oily wastewater gets larger. Thus, more efficient flotation agents must be developed. In this regard, cationic polyacrylates with amphiphilic structures are potentially efficient flotation agents. Many studies have explored the effect of monomer type on flotation performance. However, there is a lack of investigations on the effect of block sequences on flotation performance. In this paper, acrylates (including methyl acrylate (MA) and ethyl acrylate (EA)) and cationic monomers (including acryloxyethyl trimethyl ammonium chloride (DAC), methylacryloxyethyl trimethyl ammonium chloride (DMC) and acryloxyethyl benzyl dimethyl ammonium chloride (DBC)) were used as raw materials, random, diblock and triblock copolymers were prepared through free radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization. The effect of the copolymer sequence on flotation performance was studied, and triblock copolymer P(DBC-b-MA-b-DBC) had better flotation performance than those of other copolymers. The synthesis conditions of P(DBC-b-MA-b-DBC) were successively optimized using the single-factor and response surface methods, and the optimal synthesis conditions were obtained as follows: monomer concentration of 51 wt%, the first section m(DBC): the second section m(MA): the third section m(DBC) = 1.5:1:1.5, initiator concentration of 0.28 wt%, reaction time of each section of 2 h, and reaction temperature of 73 °C. Under flotation temperature of 25 °C, P(DBC-b-MA-b-DBC) concentration of 70 mg/L, aeration flow rate of 2.0 L/min and flotation time of 10 min, the oil removal of oily wastewater with initial oil content of 822 mg/L reached 96.5 %. The results of the study can provide reference for the research and development of oily wastewater treatment agents.

Effective parameters on fabrication and performance of superhydrophobic/superoleophilic polyurethane sponge: Design of experiment approach

Referring to importance of the oil/water separation as one of the main challenges in the environmental conditions, numerous researches in the superhydrophobic/superoleophilic materials especially in the industrial oily wastewater treatment have been focused. In this study, the commercial polyurethane (PU) sponge was dip-coated by zinc stearate (Zn(St)2) particles and a novel adhesive of hexamethylenetetramine (HMTA) cured phenol-formaldehyde resin (PFR). For this purpose, a design of experiment (DOE) was applied to statistically specify the effect of important process variables on the final product properties. The second-order central composite design (CCD) approach based on the response surface methodology (RSM) analysis was conducted by changing namely the Zn(St)2 suspension concentration (2–4 wt%), PFR concentration (10–30 wt%), HMTA/PFR weight ratio (10–20 wt%), and sponge density (12, 15 and 17 kg∙m−3) on the key response output variables including oil and water absorption capacity of the Zn(St)2/HMTA cured PFR-coated PU. The optimal predicted results were experimentally verified and matched well to achieve the modified superhydrophobic PU sponge for the oil/water separation. The characterizations of the modified PU sponge by SEM, EDX mapping, FTIR, XRD, UV-Vis, BET, and TGA results confirmed that the Zn(St)2 uniformly covered the entire PU sponge. In addition, it showed a high demulsification capacity, the absorption capacity of various oil and solvents, and a water contact angle as high as 165° which was further approved to be oil wet in less than <10 millisecond. More importantly, the prepared modified superhydrophobic PU sponge presented an excellent reusability performance and chemical, thermal and mechanical stability in harsh conditions. This stable superhydrophobic PU sponge with the aforementioned outstanding properties is expected to be widely used for the practical oil/water separation.

Effect of composite membrane flux behavior on oily wastewater treatment: Predicting and optimizing based response surface methodology and AI

The use of inorganic-organic composite membranes or mixed matrix membranes in membrane technology has gained worldwide recognition as a reliable method for producing drinkable water and effectively treating and purifying wastewater. This study aimed to create a model using response surface methodology (RSM) and artificial neural network (ANN) that can accurately predict and optimize the flux behavior of a membrane made of a polymeric-ceramic composite material for oil-water separation. In addition, as mentioned earlier, the optimization of the factor has been achieved through the use of RSM to establish the most optimal mode for the oil-water separation process. The findings of the RSM analysis show that the projected R2 value of 0.9764 closely matches the Adjusted R2 value of 0.9789, indicating a strong agreement between the two. Furthermore, the ANN modeling exhibited significant agreement with the actual data. The ANN model achieved a high level of performance, with an R-squared value of 0.9998 and a mean squared error (MSE) of 2.57E-03. The results were obtained by employing a model structure comprising two concealed layers, with the initial concealed layer comprising 3 neurons and the subsequent concealed layer comprising 10 neurons. The RSM was tweaked to find that the best flow mode happened when the oil emulsion level was 107.117 mg/L, the transmembrane pressure (TP) was 134.219 kPa, and the time period was 12.836 s.

One-Step Prepared Multifunctional Polyacrylonitrile/MIL-100(Fe) Membrane with High-Density Porous Fibers for Efficient Dye/Oil Wastewater Remediation.

With environmental pollution becoming more serious, developing efficient treatment technologies for all kinds of organic wastewater has become the focus of current research. In this work, the coaxial electrospinning technology was used to one-step fabricate a porous and underwater superoleophobic polyacrylonitrile nanofibrous membrane with an Fe-based metal-organic framework (MIL-100(Fe)). Benefiting from the synergistic effect of two jets, the nanofibers are smaller and denser, which prompt the exposure of more nanomaterial additives (MIL-100(Fe)). The BET surface area increased to 202.888 m2/g, and the membranes demonstrated outstanding underwater superoleophobicity. Moreover, compared with traditional blended matrix membranes by the single-axis method, separation of the modifier and membrane matrix material by coaxial methods also maintained excellent mechanical properties, which enhanced Young's modulus 3.4 times (∼1.34 MPa). As a result, facing soluble dyes, the porous C-PAN/MIL-100(Fe) membrane can demonstrate outstanding and fast adsorptive property (the Qm of MB and CR reached 44.71 and 88.74 mg g-1, respectively). For oily emulsion, the hydrophilic and oleophobic nanofibrous reticular surface provided excellent separation performance (flux: 1124.0-1549.3 L m-2 h-1, R > 98%). Moreover, the porous and underwater superoleophobic C-PAN/MIL-100(Fe)-0.5 membrane can synchronously purify the dye/oil mixture emulsions by one-step filtration. Based on the above performance, we believe that the modified nanofibrous membrane prepared by one-step coaxial electrospinning technology can promote more studies of the development of membrane preparation technology in the field of oily wastewater treatment.

Janus Membranes with Asymmetric Superwettability for High-Performance and Long-Term On-Demand Oil/Water Emulsion Separation.

Current single-function superwettable materials are typically designed for either oil removal or water removal and are constrained by oil density, limiting their widespread applications. Janus membranes with opposite wettability on their two surfaces have recently emerged and present attractive opportunities for on-demand oil/water emulsion separation. Here, a combination strategy is introduced to prepare a Janus membrane with asymmetric superwettability for switchable oil/water emulsion separation. A mussel-inspired asymmetric interface introduction cooperating with the sequence-confined surface modification not only brings about an asymmetric superwettability Janus interface but also guarantees an outstanding stable interface and remarkable chemical stability surfaces. Specifically, the superhydrophilic surface with underwater superoleophobicity can separate surfactant-stabilized oil-in-water emulsions. Conversely, other surface displays opposite superhydrophobicity and superoleophilicity to treat surfactant-stabilized water-in-oil emulsions. Significantly, this superwettable Janus membrane presents superior long-term on-demand oil/water emulsion separation without obvious flux decline and high recovery ability because of its superwettability and superior stability. Furthermore, the asymmetric superwettability enhances the interfacial floatability at air-water interfaces, enabling the design of advanced interfacial materials. The as-prepared superwettable Janus membrane has established a cooperated separation system, overcoming the monotony of conventional superwettable membranes and expanding the application of these specialized membranes to oily wastewater treatment.

Binary fiber membranes with dual transport channels and interfacial demulsification for continuous emulsion separation

Membrane fouling occurred during subsequent filtration weakens the application advantages of membrane separation technology in treating oil–water emulsions. Herein, a functionalized binary fiber membrane with dual transport channels and enhanced interfacial demulsification was fabricated to facilitate continuous emulsion separation. The interpenetrated cellulose acetate (CA) and polytetrafluoroethylene (PVDF) fibers offer independent channels for transferring water and oil in the binary fiber membrane, which enables the timely removal of continuous oil contamination to mitigate membrane fouling. Moreover, a Span 80 functional layer assembled on the binary fiber membrane by a solvent-induced grafting approach promotes dynamic interfacial demulsification and antifouling of membrane materials. Owing to the advantages of the dual oil–water transport channel and Span 80 functional demulsification layer, the binary fiber membrane can separate continuously emulsifier-stabilized oil-in-water emulsions. Consequently, the binary fiber membrane can handle emulsions with high oil content (>5 vol%), and a single-stage separation time can last up to 5 h with a separation efficiency of over 98% because of its dynamic antifouling properties. Significantly, the membrane exhibits desirable cycling performance, and the Span 80 functional layer can be easily assembled to reset the separation performance, which encourages continuous emulsion separation and an extended membrane service life. Overall, this work opens a new avenue to fabricate binary fiber membranes with dual transport channels for sustainable antifouling and continuous emulsion separation, with high potential in practical applications relating to oily wastewater treatment and fuel purification.

Conversion of chitosan and biomass fiber into recyclable superhydrophobic aerogel for efficient oil/water separation through a facile and green approach

Developing high performance and recyclable sorbent through a facile, low-cost, and eco-friendly way is quite important for oily wastewater treatment. Among the various fabrication approaches developed so far, the one using biomass waste as starting materials is particularly attractive in view of the cost and environmental benignity. Herein, a magnetic chitosan/typha orientalis fibers aerogel (MCS/TOFs) with excellent elasticity and superhydrophobicity was facilely prepared through freeze-drying and subsequent low-temperature annealing of biomass fibers (typha orientalis fibers, TOFs), chitosan (CS), and Fe3O4 nanoparticles. Benefiting from the 3D interconnected porous structure, superhydrophobic-lipophilic surface, and capillary effect of TOFs, the MCS/TOFs aerogel exhibited excellent sorption performance including fast sorption speed (few second to achieve saturation), high sorption capacity (up to 88.4 g/g), large flux (2.2 × 104 L m−2 h−1), and high separation efficiency (98.4%). Additionally, the MCS/TOFs aerogel can be facilely separated from the solution phase by a magnet at the end of the sorption process. After removal of the adsorbate by extrusion, the recovered MCS/TOFs can be used for next separation cycle, delivering high sorption capacity retention (> 91% of the initial capacity) after ten sorption-extrusion cycles. This work provides a facile biomass-based approach to high-performance and recyclable sorbent for oily wastewater treatment, exhibiting great potential in practical applications.

LDHs/TA-modified hybridized PAN/PVDF-HPF electrospinning membrane for emulsion separation

Membrane materials are widely used in the treatment of oily wastewater. In this work, hybrid nanofibrous membranes of polyacrylonitrile (PAN) and polytetrafluoroethylene-hexafluoropropylene (PVDF-HPF) were prepared by electrospinning and cured at high temperature. Subsequent hydrothermal treatment to grow Mg/Al-LDHs and polymerization of tannic acid (TA) on the surface yielded WPPLT membranes. SEM and EDS tests showed that the WPPLT membranes had a uniform compositional distribution. AFM tests showed that the hydrothermal and tannic acid treatments increased the roughness of the membranes and imparted a superhydrophilicity to the membranes. Separation tests of the emulsion showed that the separation efficiency was above 99 % with stable flux due to the fine pore size of the nanofiber membrane and the positive charge effect of the LDHs. Mechanical tensile tests showed that the tensile strength of the WPPLT membrane was 4.1 MPa, which was 89 % higher relative to the electrospinning membrane. Finally, the synergistic effect of LDHs and tannic acid under UV irradiation achieved more than 90 % degradation efficiency of methylene blue (MB). The present work provides new insights to improve the mechanical properties of nanofiber membranes, which helps the membranes to be used in more complex environments and enhances the prospect of their application in oil and water pollution.

Comparative study between bulk and surface modification on hy-drophobic membrane for dyeing and oily wastewater treatment

Surface modification could remarkably improve the oil–water separation ability of membrane, but suffers from limited survival positive effect layer after long-term operation. Herein, we report a systematic comparative study between bulk and surface modification (i.e., synchronous or sequential electrospun/elecrospraying) on hydrophobic polyvinylidene difluoride (PVDF) membrane. A hydrophilic UiO-66-NH2@polyacrylic acid micro/nanospheres (UiO@PAA) was selected as functional layer to improve the separation and adsorption capability of PVDF. The surface modification (SMM) and bulk modification membranes (BMM) exhibited the similar water wetting behavior in air as the same surface layer. The spider filament-like nanofibers of BMM could enhance the mechanical stability and dispersion uniformity of active sites among the PVDF fibers. In terms of oil-in-water emulsions separation ability, the BMM was superior to the SMM with the maximumly increase of separation efficiency and filtration flux to 1.3 % and 192.6 L m-2h−1, respectively. As for dye absorption, the BMM showed better adsorption capacity with a removal efficiency over 96 %. For the low concentration of methylene blue, the removal efficiency of SMM was only 94 %, while the removal efficiency of the BMM reached 98 % at room temperature. In addition, the BMM exhibited higher removal efficiency over 94 % compared with that less than 84 % of SMM after eight cycling tests, confirming its advantages in repeatability. This study demonstrates that the bulk modification can endow the initial membrane with better performance and durability, showing more promising prospects in actual wastewater treatment.

PPS/TA-PEI/β-FeOOH membranes with powerful photo-Fenton self-cleaning capability for efficient oil–water emulsion separation

Polyphenylene sulfide (PPS) microporous membranes have garnered extensive research enthusiasm concerning their outstanding permeation performance and separation accuracy in treating oily wastewater. Nevertheless, the inherent hydrophobic chemical structure, along with the noticeable concentration polarization effect, predisposes them to severe membrane contamination during the separation process. Accordingly, it is desirable to design a PPS self-cleaning membrane with superior anti-fouling capability, fast transport, and remarkable flux recovery. This study marks the first combination of PPS membrane materials with the photo-Fenton process. In detail, the polyphenol (tannic acid, TA)-polycation (polyethyleneimine, PEI)-metal ion (Fe3+) double cross-linking coatings were first assembled on the PPS substrate surface. Subsequently, β-FeOOH photocatalysts were synthesized through in-situ mineralization to further strengthen the hydrophilicity of the membranes. The obtained PPS/TA-PEI/β-FeOOH composite membrane achieved exceptional separation of diverse oil-in-water (O/W) emulsions. The PPS/TA-PEI/β-FeOOH membranes exhibited in-air superhydrophilic and under-water superoleophobicity, exhibiting under-water oil contact angles greater than 151° for diverse oil agents. The fabricated composite membranes displayed high permeability (a flux of the petroleum ether-in-water (P/W) emulsion reached 3400.5 L m−2h−1 bar−1 driven by a pressure of 0.05 MPa) along with ideal oil rejection (98.6 %). Significantly, the PPS/TA-PEI/β-FeOOH membrane possessed powerful photo-Fenton self-cleaning capability, and its flux recoveries of the contaminated membrane exceeded 90.3 % for varied O/W emulsions after being cleaned by visible light for 10 min. We believe that our research presents a novel approach for the exploitation of PPS-based photo-Fenton self-cleaning membranes, which also exhibit great applicative potential in oily wastewater treatment.

Enhanced treatment of oily wastewater through modified magnetic seeds for magnetic flocculation

Enhanced treatment of oily wastewater through modified magnetic seeds for magnetic flocculation

Synthesis and Characterization of Anti‐fouling Ultrafiltration Nanocomposite Membranes Integrated with S‐β Zeolite Nanoparticles for Oily Wastewater Treatment

AbstractMembrane separation has been proven to be highly effective in oily wastewater treatment, although fouling remains a persistent challenge. This study explored the incorporation of S‐β zeolite nanoparticles into an ultrafiltration membrane, forming a nanocomposite to tackle fouling and enhance water flux recovery. Porous nanoparticles were synthesized using sol‐gel and hydrothermal methods, featuring a remarkable surface area of 450 m2/g and pore sizes ranging from 50 to 175 nm according to BET results. These nanoparticles were integrated into the membranes at various concentrations using the phase inversion technique. The presence of S‐zeolite in the membrane was confirmed through FTIR, EDX, and SEM analyses. The S‐β1 nanocomposite membrane demonstrated exceptional antifouling properties, particularly at higher concentrations of oily wastewater. Its outstanding performance is attributed to its enhanced hydrophilicity and average pore size of 13±3 nm, which prevents fouling formation. Compared to other membranes, S‐β1 exhibited remarkable water flux recovery, reaching 100 % at an oil concentration of 50 ppm and 72 % at 1000 ppm. These results highlight the significant advantages of this nanocomposite in reducing fouling and improving the water flux recovery in oily wastewater treatment.

Study on efficient oil-containing wastewater purification with super-hydrophilic PVDF coating

The sustainable, low-energy, and cost-effective treatment of oily wastewater has become an important issue for aquatic ecosystems, environmental protection, and economic development. Improper treatment could have a significant impact on aquatic ecosystems, resulting in eutrophication and fish deaths. The method for preparing PVDF-CC by impregnation involves using polyvinylidene fluoride (PVDF), chitosan, and sodium citrate. Moreover, these performance improvements can be achieved at a lower cost compared to using many other chemical agents in membrane processing.

A rapid two-step process to prepare a high-throughput, efficient, reusable superhydrophobic–superoleophilic stainless steel mesh for oil/water separation

Currently, due to the industrial development, the direct discharge of large amounts of oil-containing wastewater has led to serious water pollution. It is necessary to develop an efficient, durable, and high-throughput material for oil–water separation. To achieve this, we prepared a nickel (Ni) coating with a loose leaf-like micro/nanostructure on the surface of stainless steel mesh (SSM), imparting it with superhydrophobic and superoleophilic properties. The deposition of ions onto the substrate was carefully controlled by adjusting the deposition parameters. Subsequently, the as-prepared Ni coating was further modified using a solution of perfluorooctyltriethoxysilane (PFOTS) in ethanol to obtain a PFOTS/Ni mesh (PNM) with excellent superhydrophobic–superoleophilic properties. Wettability tests revealed that the water contact angle (WCA) and oil contact angle (OCA) of the PNM, prepared under the optimized deposition conditions, were 161 ± 1° and 0°, respectively, with a water sliding angle (WSA) of less than 10°. Importantly, the PNM demonstrated remarkable mechanical stability in blade scratch and tape peel tests, as well as excellent chemical stability in acid-alkali resistance and electrochemical corrosion tests. And, the PNM exhibited remarkable self-cleaning capability. Additionally, PNMit filters displayed outstanding efficiency in separating oil and water (reaching 91.5%) and remarkable durability. The results indicate that the well-designed superhydrophobic–superoleophilic SSM exhibits advantages such as simple fabrication, low cost, high reusability, and strong robustness. It holds great potential for practical applications in the treatment of oily wastewater and oil spill remediation.

Switchable superlyophobic CoAl-layered double hydroxide (LDH)-based mesh membranes for separation of various oil/water systems and removal of soluble organic pollutants

Switchable surface wettability has attracted tremendous attention owing to its potential applications, but it is still thorny to construct under-liquid dual superlyophobic surfaces for reversible separation of emulsified oil/water mixtures and treatment of complex oily wastewater. In this work, a CoAl-LDH-based mesh membrane was prepared for switchable separation of emulsified oily wastewater. The interpenetrating CoAl-LDH nanosheets were grown on the stainless steel mesh (SSM) forming a micro-/nano hierarchical structure via a hydrothermal method, which endows the membrane with under-liquid dual superlyophobicity. The obtained CoAl-LDH membrane exhibited switchable separation capability for both oil/water mixtures and oil/water emulsions with high fluxes and efficiencies (99.7%). In addition, the CoAl-LDH membrane could not only separate but also photodegrade the oil-in-water (O/W) emulsions containing soluble organic pollutants. Interestingly, after introducing a ZnO nanorod layer, the LDH/ZnO membrane exhibited progressive removal efficiency (99%) and photodegradation efficiency (＞99%) for methylene blue (MB). The cycled and harsh condition tests also confirmed the stability and robustness of the prepared membranes. The excellent separation performance and photocatalytic property endow the membranes appealing to practical oil/water separation and oily wastewater treatment.