Mesh Pore Size Research Articles

A gradient porous transport layer enabling a high-performance proton-exchange membrane electrolysis cell

Large-scale green hydrogen production through proton-exchange membrane electrolysis cells (PEMECs) is constrained by high costs. Operating PEMECs at high current densities while minimizing overpotentials, particularly the mass transport overpotential due to intense water-oxygen two-phase flow, is crucial. The porous transport layer (PTL) plays a key role in facilitating water-oxygen two-phase flow and affecting ohmic resistance and catalyst utilization. In this study, a gradient PTL has been developed by introducing titanium mesh with tunable pores between the titanium felt and the flow field. The woven mesh structure with large pores facilitates water transport under the ribs, while the titanium felt reduces ohmic resistance and improves catalyst utilization. Experimental results demonstrate that the gradient PTL with a single layer of titanium mesh (pore size: 0.6 mm) can reduce the mass transport overpotential from 0.478 V to 0.206 V at 5 A/cm2 and maintain low ohmic and activation overpotentials compared with the conventional PTLs. Additionally, the gradient PTL with two titanium mesh layers (pore sizes: 0.6 mm and 0.28 mm) can further facilitate water transport, reducing mass transport overpotential to 0.149 V at 5 A/cm2. Numerical simulations reveal that the developed gradient PTL increases the volume fraction of liquid water and ensures uniform water distribution in the catalyst layer. The combined results indicate that the gradient PTL design is promising for enhancing mass transport performance while maintaining low ohmic resistance and high catalyst utilization, making PEMECs more viable for large-scale hydrogen production.

Is mesh pore size in polypropylene meshes associated with the outcome in Lichtenstein inguinal hernia repair: a registry-based analysis of 22,141 patients

IntroductionExperimental data show that large-pored meshes reduce foreign body reaction, inflammation and scar bridging and thus improve mesh integration. However, clinical data on the effect of mesh porosity on the outcome of hernioplasty are limited. This study investigated the relation of pore size in polypropylene meshes to the outcome of Lichtenstein inguinal hernioplasty using data from the Herniamed registry.MethodsThis analysis of data from the Herniamed registry evaluated perioperative and 1-year follow-up outcomes in patients undergoing elective, primary, unilateral Lichtenstein inguinal hernia repair using polypropylene meshes. Patients operated with a non-polypropylene mesh or a polypropylene mesh with absorbable components were excluded. Polypropylene meshes with a pore size of 1.0 × 1.0 mm or less were defined as small-pored meshes, while a pore size of more than 1.0 × 1.0 mm was considered large-pored.Unadjusted analyses and multivariable analyses were performed to investigate the relation of pore size of polypropylene meshes, patient and surgical characteristics to the outcome parameters.ResultsData from 22,141 patients were analyzed, of which 6853 (31%) were operated on with a small-pore polypropylene mesh and 15,288 (69%) with a large-pore polypropylene mesh. No association of mesh pore size with intraoperative, general or postoperative complications, recurrence rate or pain requiring treatment was found at 1-year follow-up. A lower risk of complication-related reoperation tended to be associated with small-pore size (p = 0.086). Furthermore, small-pore mesh repair was associated with a lower risk of pain at rest and pain on exertion at 1-year follow-up.ConclusionThe present study could not demonstrate an advantage of large-pore polypropylene meshes for the outcome of Lichtenstein inguinal hernioplasty.

Optimal Mesh Pore Size Combined with Periodic Air Mass Load (AML) for Effective Operation of a Self-Forming Dynamic Membrane BioReactor (SFD MBR) for Sustainable Treatment of Municipal Wastewater

A self-forming dynamic membrane bioreactor (SFD MBR) is a cost-effective alternative to conventional MBR, in which the synthetic membrane is replaced by a “cake layer,” an accumulation of the biological suspension over a surface of inert, low-cost support originated by filtration itself. Under optimized conditions, the cake layer is easy to remove and quick to form again, resulting a “dynamic membrane.” The permeate of the SFD MBR has chemo-physical characteristics comparable to those of conventional ultrafiltration-based MBR. In this paper, two nylon meshes with pore sizes of 20 and 50 µm, respectively, were tested in a bench-scale SFD MBR in which an air mass load (AML) was periodically supplied tangentially to the filtration surface to maintain filtration effectiveness. The SFD MBR equipped with 20 µm nylon mesh coupled with 5 min of AML every 4 h showed the best performance, ensuring both a permeate with turbidity values always below 3 NTU and revealing no increases in transmembrane pressure (TMP) with manual maintenance needs. A benchmark test with the only difference of a suction break (relaxation) instead of AML was conducted under identical operating conditions for validation with an already known maintenance strategy. This latter test produced a permeate of very good quality, but it needed frequent TMP increases and consequent manual cleanings, showing that a periodic AML coupled with the use of a 20 µm mesh can be an optimal strategy for long-term operation of SFD MBR.

Controllable penetration of underwater bubble via an integrated Janus mesh

Underwater bubble dynamics and manipulation have emerged as an important research hotspot for boiling heat transfer, as well as bubble transport and collection. However, achieving switchable and controllable penetration of bubbles remains a challenge. In this work, by using laser etching and post-modification, Janus meshes with four pore sizes ranging from micron to millimeter sizes were prepared for unidirectional penetration of bubbles. Although typical unidirectional penetration was observed in these Janus meshes of four pore sizes, they all exhibit easy passage of bubbles without the desired controllable and switchable properties for penetration behaviors. The Janus mesh (with a pore size of ∼930 μm) is respectively superimposed with hydrophilic meshes of different pore sizes as integrated meshes. Interestingly, the integrated meshes take a penetration behavior transition of the bubbles from prohibited to a critical state, and easy permeation by changing the pore size and thickness of the hydrophilic mesh. The controllable permeability of the integrated mesh is attributed to different levels of resistance (i.e., the gas pressure at the upper interface, Pup) before acquiring a Laplace pressure. The integrated mesh can function as a bubble switch, offering a flexible and effective strategy for controllable penetration of underwater bubbles.

Conduction-Dominated Cryomesh for Organism Vitrification.

Vitrification-based cryopreservation is a promising approach to achieving long-term storage of biological systems for maintaining biodiversity, healthcare, and sustainable food production. Using the "cryomesh" system achieves rapid cooling and rewarming of biomaterials, but further improvement in cooling rates is needed to increase biosystem viability and the ability to cryopreserve new biosystems. Improved cooling rates and viability are possible by enabling conductive cooling through cryomesh. Conduction-dominated cryomesh improves cooling rates from twofold to tenfold (i.e., 0.24 to 1.2× 105 °C min-1 ) in a variety of biosystems. Higher thermal conductivity, smaller mesh wire diameter and pore size, and minimizing the nitrogen vapor barrier (e.g., vertical plunging in liquid nitrogen) are key parameters to achieving improved vitrification. Conduction-dominated cryomesh successfully vitrifies coral larvae, Drosophila embryos, and zebrafish embryos with improved outcomes. Not only a theoretical foundation for improved vitrification in µm to mm biosystems but also the capability to scale up for biorepositories and/or agricultural, aquaculture, or scientific use are demonstrated.

A novel solid-state submerged fermenter (3SF) for acidogenic fermentation of food waste at high volumetric loading: Effect of inoculum to substrate ratio, design optimization, and inoculum enrichment

This study reports the development and operation of a solid-state submerged fermenter (3SF) to produce short-chain fatty acids (SCFAs) from food waste at high volumetric loading of 55 gVS/Lreactor. To maximize food waste degradation and SCFA production in the 3SF, three factors were optimized: inoculum to substrate ratio (16%, 9%, 6%, and 4%), mesh pore size of the food waste holding chamber (4.5 mm, 2 mm, and 1 mm), and enrichment of the inoculum. The 3SF operation at higher inoculum-to-substrate ratio (ISR) of 16% resulted in 13–20% higher hydrolysis (600 ± 6.6 gCOD/kgVSadded) and SCFA yields (480 ± 8.7 gCODSCFA/kgVSadded) than those obtained at lower ISRs of 4–6%. Optimization of the mesh pore size (2 mm) further improved hydrolysis and SCFA yield to 628 ± 6.1 gCOD/kgVSadded and 517 ± 7.3 gCODSCFA/kgVSadded, respectively. Enrichment of the inoculum increased the hydrolysis and acidification rates resulting in significantly higher (P ≤ 0.05) hydrolysis and SCFA yields than the non-enriched reactor in just 8 days, implying a 43% reduction in the fermentation time. SCFA composition comprised of acetate, propionate, and butyrate for all reactors. However, an increase in ISR and the use of enriched inoculum resulted in a gradual increase in butyrate composition within the SCFA mix with a maximum butyrate composition of 46% on day 8. Microbial composition showed a high relative abundance of Enterococcus, Clostridium Sensu Stricto 1, and Bacteroides.

Bioinspired antifouling mesh with liquid-adaptive wettability for on-demand separation of oil-in-water and water-in-oil emulsions

Separation materials integrating robust fouling resistance and switchable wettability have been considered as promising candidates for oily sewage treatment, but there is still great challenge. Inspired by goose feathers, a unique antifouling mesh with liquid-adaptive wettability was prepared by in situ electrochemical growth of feather-like copper arrays on stainless steel mesh. The hierarchical feather-like copper arrays not only reduced the mesh pore sizes to improve its separation efficiency (98.9%), but also captured oil or water by simple pre-infusion to form a robust liquid cushion to tune the mesh wettability. The formed robust liquid cushion also endowed the mesh with outstanding antifouling abilities. Thus, the mesh exhibited excellent on-demand separation performance for various oil-in-water and water-in-oil emulsions. Besides, the mesh exhibited durable liquid-adaptive wettability in harsh environment, promising application in separating dual emulsions.

Definition of Mesh Weight and Pore Size in Groin Hernia Repair: A Systematic Scoping Review of Randomised Controlled Trials.

Introduction: Groin hernia literature often uses the terms light- and heavyweight and small or large pores to describe meshes. There is no universal definition of these terms, and the aim of this scoping review was to assess how mesh weight and pore sizes are defined in the groin hernia literature. Methods: In this systematic scoping review, we searched PubMed, Embase, and Cochrane CENTRAL. We included randomised controlled trials with adults undergoing groin hernia repair with the Lichtenstein or laparoscopic techniques using a flat permanent polypropylene or polyester mesh. Studies had to use the terms lightweight, mediumweight, or heavyweight to be included, and the outcome was to report how researchers defined these terms as well as pore sizes. Results: We included 48 studies with unique populations. The weight of lightweight meshes ranged from 28 to 60g/m2 with a median of 39g/m2, and the pore size ranged from 1.0 to 4.0mm with a median of 1.6mm. The weight of heavyweight meshes ranged from 72 to 116g/m2 with a median of 88g/m2, and the pore size ranged from 0.08 to 1.8mm with a median of 1.0mm. Only one mediumweight mesh was used weighing 55g/m2 with a pore size of 0.75mm. Conclusion: There seems to be a consensus that meshes weighing less than 60g/m2 are defined as lightweight and meshes weighing more than 70g/m2 are defined as heavyweight. The weight terms were used independently of pore sizes, which slightly overlapped between lightweight and heavyweight meshes.

PHOTOCATALYTIC DEGRADATION OF METHYLENE BLUE FROM AQUEOUS SOLUTION USING BASE MODIFIED TERMITE SOIL UNDER UV LIGHT IRRADIATION

Photocatalysis is an effective treatment method for removal of toxic pollutants from industrial wastewaters. Sodium hydroxide was used to modified termite mound soil obtained from Ahmadu Bello University Zaria, Kaduna State, Nigeria. The soil was washed with deionized water and placed in an oven set at 60oC for 6 hrs before crushing with an aggregate impact crusher, sieved with 0.075 m mesh pore size. The sieved soil sample was tagged as unmodified-TMS (termite mound soil). The soil sample was modified using sodium hydroxide (NaOH) at different concentrations (5 %, 10 %, 15 %, and 20 % W/V). The modified and unmodified-TMS catalysts were characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray fluorescence (XRF), Electron diffractive X-ray (EDX), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and Selected area electron diffraction (SAED), The photocatalytic activity of the unmodified-TMS, 5 % NaOH, 10 % TMS-NaOH, 15 % TMS-NaOH, and 20 % TMS-NaOH, were assessed by testing the degradation rate of Methylene Blue under ultraviolet light irradiation. The results indicated that the samples exhibited the best photocatalytic activity at optimum parameters of catalyst dosage 2.5 g /L. pH 9 and 125 mg/L concentration of MB this is evidenced by the highest methylene degradation rate of (74 %). The photocatalytic degradation of the Methylene blue dye was found to obey first-order kinetics.

MODIFICATION OF TERMITE MOUND SOIL USING PHOSPHORIC ACID FOR PHOTODEGRADATION OF METHYLENE BLUE DYE UNDER UV LIGHT IRRADIATION

Termite mound was mined from the termite nest spotted at Ahmadu Bello University, Zaria Kaduna State, Nigeria. It was washed with deionized water and placed in an oven set at 60oC for 6 hrs before crushing with an aggregate impact crusher and sieved into 0.075 m mesh pore size. The sieved soil sample was tagged as unmodified-TMS (termite mound soil). The soil sample was modified using orthophosphoric acid (H3PO4) at different (5 %, 10 %, 15 %, and 20 %) concentrations. The modified and unmodified-TMS were characterized by the methods of scanning electronic microscope (SEM), transmission electron microscope (TEM), Electron diffractive X-ray (EDX), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), and Selected area electron diffraction (SAED), The photocatalytic activity of the unmodified-TMS, 5 % TMS-H3PO4, 10 % TMS-H3PO4 , 15 % TMS-H3PO4 , and 20 % TMS-H3PO4, were assessed by testing the degradation rate of Methylene Blue under ultraviolet light irradiation using optimum parameters (1.5 g/L, pH 11 & 75 mg/L). The results indicated that the samples exhibited the best photocatalytic activity at optimum parameters of catalyst dosage 1.5 g /L. pH 11 and 75 mg/L concentration of MB as evidenced by the highest methylene degradation rate of (88 %). The photocatalytic degradation of Methylene blue dye was found to obey first-order kinetics.

Mesh-tissue integration of synthetic and biologic meshes in wall surgery: brief state of art.

Many studies show that surgical hernia repair with the use of prosthetic meshes can result in pain, hernia recurrence, contraction and mesh rupture. Numerous experimental studies have been conducted to understand the effect of mesh stiffness, pore size and mesh patterns on mesh biocompatibility. The purpose of this mini review is to present an overview of the contracture, adhesion, tissue regrowth and histological response characteristics of permanent and absorbable mesh. Indeed, the mechanics of mesh-human tissue interaction is poorly understood in the literature. It has been shown that early integration of biological meshes is critical for sustained hernia repair. One of the emerging experimental approaches is to combine cell-based regenerative medicine with mesh materials. Studies in preclinical models show that the use of synthetic and biological meshes with autologous cell implantation improves the biocompatibility of biomaterials, promoting key tissue regeneration processes such as adhesion and vascularisation.

Novel Method of Oil/Water Separation Using Composite of Polymethylacrylamide Hydrogel-Coated Metal Mesh

Different compositions of hydrogels composed of mathacrylamide homopolymer (60 and 90% of PMAM) were prepared using the free radical polymerization technique, with and without methylene bisacrylamide as crosslinker (0 and 3%). Several parameters and properties were studied to evaluate their performance as oil/water separators. Many parameters are used, such as residual oil in water, water recovery, separation time, hydrogels coated percentages, swelling parameters, mechanical properties, microscopic and photographic images, and scanning electron microscopy. The results showed that water recovery (87-97), Separation efficiency (96.2-99.6 %), separation time (6-9.5 min.), hydrogels coated percentages (18-23 %), water content (70-97 %), and tensile test (63-90 MPa). The effect of polymer crosslinking density, mesh pore size, and polymer composition on the parameters and properties mentioned above were also studied. The results showed that the separation efficiency of 1000 micron mesh composite is better than 500-micron mesh composites.

Investigating the bone regeneration activity of PVA nanofibers scaffolds loaded with simvastatin/chitosan nanoparticles in an induced bone defect rabbit model

This study aims at preparing electrospun PVA NFs incorporating simvastatin/chitosan nanoparticles (SIM CS NPs) as a controlled drug eluting scaffold for bone regeneration. Optimization was performed by Design Expert® software through establishing two factor, three level factorial design, where the independent variables were the applied voltage, flow rate and PVA solution/SIM CS NPs ratio. Formulation variables values for the optimized formula were 18KV, 0.5 mL/h, and 3:1 respectively. NFs diameter and mesh pore size were chosen as the dependent variables. The optimized NFs were evaluated morphologically, chemically, and physically. Additionally, in-vitro SIM release from the scaffolds was investigated along 24 days. Optimum NFs possessed 136 nm diameter size and 6.5 nm porosity. Also, they showed sustained SIM release for 24 days to achieve the desired goal in bone regeneration. The optimized NFs were implanted within induced bone defects in rabbits. In-vivo assessments were performed through cone beam computed tomography 3D images, bone density measurements, histological analysis and bone morphogenetic protein 2 (BMP 2) level. The obtained results proved the high potential of the optimized NFs in promoting bone regeneration compared to untreated group, non-medicated NFs group, free SIM group and NFs loaded with SIM group after 6 weeks of implantation.

Effect of Pore Size and Hydrophobic Coating on Oil-Water Separation System for Grease Trap

Public concern towards solidification of fat, oil, and grease (FOG) through disposed wastes into the drainage system is an unresolved issue to this day. The use of skimmer to separate oil and water form their mixture is a less comprehensive solution. This paper aimed to design the concept and fabricate oil-water separation medium, as well as to analyse the effect of different pore sizes of wire mesh and coating respectively. Water separation system is designed based on Pugh Method, while stainless steel wire mesh is used in analysing the water repellent and oil absorption characteristics. Titanium dioxide is used as coating. Surface characterization and contact angle of droplet were observed using scanning electron microscope and contact angle measurement tools. Hydrophobicity of uncoated stainless steel of wire mesh will increase if the pore size of wire mesh is decreasing in size. The more layers of coating increase the hydrophobicity of the wire mesh in increments with contact angle more than 100⁰. For the cooking oil droplet to expeditiously spread over the mesh surface and rapidly permeate through the mesh less than 1 second, showed the oleophilic nature of the mesh.

Degradation of dissolved RDX, NQ, and DNAN by cathodic processes in an electrochemical flow-through reactor

Both legacy munitions compounds (e.g., RDX) and new insensitive high explosives (e.g. DNAN, NQ) are being manufactured and utilized concurrently, and there exists a need for wastewater treatment systems that are able to degrade both classes of explosives. Electrochemical systems offer treatment possibilities using inexpensive materials and no chemical additions. Electrochemically induced removal of RDX, NQ, and DNAN were separately studied within an electrochemical plug flow reactor hosting a stainless steel (SS) cathode and downstream Ti/MMO anode. Varying wire mesh cathodes and operating conditions were evaluated in an effort to identify the optimal cathode material, to determine the relative contributions of cathodically-induced removal processes, to shorten time to steady-state removal conditions, and to find practical ranges of operating conditions. Applied current allowed the cathode to support munitions removal mainly by direct reduction at the cathode surface, and the secondary reactions of cathodically-induced alkaline hydrolysis and catalytic hydrogenation by adsorbed H on Ni-containing cathode surfaces might contribute to some munitions degradation. The optimal cathode material was identified as SS grade 316, possibly due to its superior Ni content and lack of corrosion protection coating. Higher current, longer cathode length, and smaller mesh pore sizes resulted in slightly greater removal extents and shorter acclimation times to steady state removal conditions, but there are practical upper limits to these properties. Higher Ni content within SS improved RDX and NQ removal but does not affect DNAN removal. Prolonged use of SS grade 316 showed no debilitating changes in electrical performance or chemical content.

Particle Engineering by Nano Spray Drying: Optimization of Process Parameters with Hydroethanolic versus Aqueous Solutions.

Nano spray drying has emerged as an outstanding platform for engineering micro- and nanoparticles, with growing applications in various areas of drug delivery. As a new technology involving distinct technical design, parameters of the nano spray drying process are not fully elucidated. In a quality-by-design approach, the aim of the current study was to gain thorough understanding of critical determinants of product characteristics in the Büchi Nano Spray Dryer B-90. Following a factorial experimental design, a series of spray drying experiments were conducted to gain new insights into the influences of the inlet temperature, the spray solvent, and the solute concentration in the spray solution on the yield, the moisture content, and the particle size of the nano spray-dried powder material. Special consideration was given to the potential of using hydroethanolic in comparison with aqueous solvent systems and to particle engineering for pulmonary drug delivery. Lactose and mannitol, widely used as excipients in dry powder inhalation formulations, were used as model materials. Lactose and mannitol are known to spray dry in amorphous and crystalline forms, respectively. The yields of spray drying of lactose and mannitol amounted generally to 71.1 ± 6.6% w/w and 66.1 ± 3.5% w/w, respectively. The spray-dried materials exhibited generally a number-weighted median particle diameter of 1.6 ± 0.2 μm and a volume-weighted median particle diameter of 5.1 ± 1.0 μm. A detailed analysis of the results improved understanding of the interplay between process parameters in the Nano Spray Dryer. The results demonstrate that optimization of spray generation is the key to yield optimization. On the other hand, particle size is determined by the spray mesh pore size and the spray solution degree of saturation. Selection of an appropriate spray solvent and using spray solution additives could optimize spray flow. In parallel, the spray solvent and the solute concentration in the spray solution determine the degree of saturation. Guidance on optimization of particle engineering by nano spray drying is provided.

Dynamic membranes with sparse nanofibers as the skeletons yield better and more stable effluent quality without sacrificing the flux in bioreactors

Previous studies found that the inhabitation of filamentous bacteria on the support materials with large apertures in dynamic membrane bioreactor (DMBR) could stabilize the DM structure and resulted in stable effluent quality. However, it is hard to cultivate the filamentous bacteria on support materials in DMBR intentionally. In present study, a polyvinyl alcohol (PVA) nanofiber layer was coated on 180-μm nylon mesh to simulate the inhabitation of filamentous bacteria. The nanofiber coated mesh with 1 h spinning time (referred as PVA-1h) had a similar porosity (14.9%) to that of 25-μm nylon mesh and dominant pore size of 1.0–2.5 μm. Short-term test indicated that the PVA-1h had a low initial effluent turbidity of 5.3 NTU and could form DM within 5 min. Long-term test in DMBR demonstrated that better and more stable effluent quality (0.71 ± 0.31 NTU) was achieved by PVA-1h compared to typical used support materials of 25-μm mesh (1.04 ± 0.60 NTU). However, the PVA-1h had an operation flux of 30–50 L/(m2·h) with a water head loss ≤2 cm, which was comparable with the 25-μm mesh but much greater than that of 2.6-μm mesh (<5 L/(m2·h)). In addition, the filtration resistance change between the PVA-1h and 25-μm mesh were very similar. Therefore, this study demonstrated that with proper density of nanofiber as the skeletons, DMs would be formed more quickly and stably, resulting in better and more stable effluent quality in DMBR without sacrificing operation flux.

Development and performance of a dynamic membrane for anaerobic wastewater treatment - an analysis with different mesh pore sizes and configurations.

Recent studies have focused on proposing materials with larger pores and lower cost to replace conventional membranes. This study aims to investigate the performance of an anaerobic dynamic membrane bioreactor (AnDMBR) at pilot scale, acting as a post-treatment for an Upflow Anaerobic Sludge Blanket (UASB) reactor treating sewage, for the removal of complementary organic matter, focusing on the module design, dynamic layer formation and process performance. The configurations tested on this study were: UASB followed by stone filter and three AnDMBRs in series with polyester pore sizes of 100 μm, 50 μm, and 5 μm; UASB followed by disc filter and the three AnDMBRs in series; UASB followed by the three AnDMBRs in series; and UASB reactor with only one AnDMBR module. Regarding the studied configurations, high removals of total suspended solids, chemical oxygen demand, and turbidity were achieved in all experimental setups. The use of stone and disc filters did not bring clear benefits to the system concerning the direct application of filtration with dynamic membranes, therefore, their removal in the system was favorable. The dynamic membrane formation was faster in the 50 μm mesh, and only a few hours were necessary to obtain a permeate quality with a total suspended solids concentration and a turbidity lower than 15 mg·L-1 and 30 NTU, respectively. Thus, the dynamic membrane technology proved to be a potential solution in the post-treatment of UASB reactor effluents.

A novel and facile preparation of Superhydrophilic/Superoleophobic nanofilter using carbon nitride nanosheet for W/O emulsion separation

In this research, a novel superhydrophilic/ superoleophobic thermoplastic polyurethane@graphitic-carbon nitride@perflourooctanoic acid (TPU@g-C3N4 @PFOA) coated stainless steel mesh was prepared to separate water/oil emulsion. g-C3N4 nanosheets were synthesized with a facile thermal condensation process followed by exfoliation using acid. TPU as a binder is commercially available and provides strong bonding of the nanocomposite coating to the substrate. Wettability characteristics of nanocomposite coated mesh showed the water contact angle of 18.9° and oil contact angle of 151°, which confirmed the special wettability of superhydrophilicity and superoleophobicity. The prepared nanocomposite-coated filter with the surface energy of 92.87 mN/m (dispersive and polar surface energy of 0.199 and 92.68 mN/m) was able to separate water from a 10 wt % water/oil emulsion. Ultimately excellent water–oil separation efficiency of 99% and the filtration flux of 50.5 L.m−2.h−1 were attained under gravity. The particular behavior of the surface is justified with small pore size of mesh, higher roughness and superoleophobic wettability due to the presence of g-C3N4 nanosheets, as well as with the reduction of the surface energy of the synthesized TPU@g-C3N4 by PFOA, as a surfactant with the fluorine tail groups. As-prepared mesh can also separate free crude oil–water mixtures with the separation efficiency and flux of 99.9% and 2157.4 L.M−2.h−1, respectively.The anti-fouling and mechanical stabilities of the as-prepared coated mesh were investigated. This result implied that the as-prepared water-removing filter has great potential for separation of the water-in-oil emulsion, which has long been a problem in industry and is often separated using oil-removing filters in the literature.

Water sprays formed by impinging millimeter-sized droplets on superhydrophobic meshes

Impinging a millimeter-sized liquid droplet on a leaky substrate—such as a porous mesh—can cause the formation of many small droplets from the ligament fragmentation. Although this phenomenon has been widely considered as a desirable strategy to produce liquid sprays of monodisperse droplets, the underlying mechanism has not yet been completely elucidated, and the spray needs detailed characterization. Herein, we experimentally investigate the atomization phenomena occurring in the recoiling and spreading stages of impinging water droplets on superhydrophobic meshes. We show that the spray formed during droplet recoiling is stimulated by the longitudinally symmetric air cavity collapse on the superhydrophobic mesh, and thus the size of the spray formation area on the mesh is almost identical to the size of the simultaneously generated upward jet. By contrast, the water spray produced during droplet spreading is expelled under the action of the inertia-induced hydrodynamic pressure, and the size of spray formation area on the mesh exhibits a power-law dependence on the Weber number; yet, the pore geometry restricts it to take a constant value when the Weber number is sufficiently high. By performing statistical analyses on the spray droplet sizes, we further demonstrate that the mean sizes of spray droplets are mainly set by the mesh pore sizes, but the complex atomization dynamics leads to a broad size distribution, which is beyond the expectation.