Fabrication of SPES/Nano-TiO_2 Composite Ultrafiltration Membrane and Its Anti-fouling Mechanism

Membrane fouling is one of the major obstacles for reaching a high flux over a prolonged period of ultrafiltration（UF）process.In this study,a sulfonated-polyethersulfone（SPES）/nano-TiO2 composite UF membrane with good anti-fouling performance was fabricated by phase inversion and self-assembly methods.The TiO2 nanoparticle self-assembly on the SPES membrane surface was confirmed by X-ray photoelectron spectroscopy （XPS）and FT-IR spectrometer.The morphology and hydrophilicity were characterized by scanning electron microscopy（SEM）,atomic force microscopy（AFM）and contact angle goniometer,respectively.The anti-fouling mechanism of composite UF membrane was discussed through the analysis of the micro-structure and component of UF membrane surface.The results showed that the TiO2 content and the micro-structure of the composite UF membrane surface had great influence on the separation and anti-fouling performance.

Fabrication of magnetically responsive anti-fouling and easy-cleaning nanofiber membrane and its application for efficient oil-water emulsion separation

The magnetically responsive anti-fouling nanofiber membrane(MRANM)was fabricated for efficient oilwater emulsion separation,which could be cleaned using oscillating magnetic field.MRANM was prepared by grafting superparamagnetic Fe_(3)O_(4) nanoparticles onto the surface of electrospun polyacrylonitrile nanofiber membrane(PANM).Compared with PANM,the water contact angle of MRANM decreased from 104°to 0°,indicating that the hydrophilicity of the membrane was significantly improved.For the emulsions of hexadecane,octane and rapeseed oil,the separation efficiency was 98.04%,96.59%and 92.67%,respectively.After the treatments in oscillating magnetic field,the separation efficiency kept above 95%after 8 times recycling,which indicated that the MRANM had good regenerability and reusability.The as-fabricated membrane with magnetic responsiveness facilitated an effective method for solving the membrane fouling problem during practical applications of separation high viscosity oil-water emulsion.

Porous polybenzimidazole membranes with positive charges enable an excellent anti-fouling ability for vanadium-methylene blue flow battery

A cost-effective, high-performance and highly stable membrane has always been in intensively needed in aqueous organic-based flow batteries. Here we present a porous polybenzimidazole(PBI) membrane with positive charges that endow the membrane with a high rejection and an excellent anti-fouling ability for target organic molecule and asymmetric structure that affords a high conductivity for vanadiummethylene blue flow battery(V-MB FB). The morphologies and thickness of separating layer in particular of the porous PBI can be well adjusted by simply altering the polymer concentration in the cast solution and further afford the membrane with a controllable property in terms of both ion selectivity and ion conductivity. As a result, a V-MB FB assembled with a porous PBI membrane delivers a coulombic efficiency(CE) of 99.45% and an energy efficiency(EE) of 86.10% at a current density of 40 mA cm^(-2), which is 12% higher than that afforded by a Nafion 212 membrane. Most importantly, the V-MB FB demonstrates a methylene blue(MB) utilization of 97.55% at a theoretical capacity of 32.16 Ah L^(-1)(based on the concentration of MB in the electrolyte) because of the high ion conductivity of the membrane, which favors reducing the cost of a battery. The results suggest that the designed porous PBI membranes exhibit a very promising prospect for methylene blue-vanadium flow battery.

Electromagnetic anti-fouling technology for prevention of scale

An electromagnetic anti-fouling technology(EAFT) was developed further. The operating principle of the EAFT was presented using fundamental physics laws. To validate the effect of EAFT and identify the mechanism, a circulating flow setup was built. A series of fouling tests were carried out with and without EAFT, measuring fouling thermal resistance as function of time, making scanning electron microscope images and analyzing the particles size distribution in solution by dynamics light scattering technology. The main results were as follows: 1) All the precipitated crystals in solution were calcite and there were little differences between with EAFT and without EAFT in the experimental range. 2) The number of precipitate nucleation in solution was small and the particle growth was slow without EAFT. In opposition to the case untreated, a rapid particle growth was observed and the number of nucleation was expected to be large, due to the fact that the EAFT effectively increases the ions and crystals collision frequency and effectiveness by utilizing the induced electric field. It is indicated that the particle growth is promoted mainly by coagulation process but not nucleation growth. 3) The EAFT could prolong the delay time of fouling greatly, and after the delay time, the thermal resistance quickly increased. Therefore, in order to mitigate scale significantly, the floccules in solution should be deposited beforehand in a low-lying area of the exchangers and let off in time.

The Impact of Implementing the International Convention on the Control of Harmful Anti-fouling Systems in Ships （AFS Convention） on the Marine Environment

Marine fouling is the settlement and growth of a variety of marine organisms, such as bacteria, diatoms, protozoa and algae spores on structures immersed in seawater, such as ship＇s hulls, navigation buoys, and sonar equipment. Anti-fouling refers to material or systems used to prevent the accumulation of biological material on submerged surfaces. Bio-fouling results in higher fuel consumption and can also facilitate the transport of harmful NIS （Non-Indigenous Species）. Antifouling technologies incorporating biocides （e.g., Tributyltin） have been developed to prevent fouling. Their widespread use, however, raised concerns about their toxic effects on marine communities. The AFS Convention （International Convention on the Control of Harmful Anti-fouling Systems in Ships） is a 2001 IMO （International Maritime Organization） treaty, whereby states agree to ban the use of harmful anti-fouling paints and other anti-fouling systems that contain harmful substances. Particularly, the use of the organotinTributyltin is prohibited, since leaching of that chemical from the hulls of ships has been shown to cause deleterious effects on some sea creatures. Although the AFS Convention has entered into force, its full implementation has not yet been appropriately achieved. Most of the ratifying States have delegated the Classification Society to inspect their ships to ensure the implementation of the provisions of the Convention. Since painting ships takes place in dry docks, the full control falls in the hands of Classification Societies.

Long-Lasting Filtration of Oily Water by Anti-Fouling Underwater Oleophobic Sand Particles

The produced water from the oilfield was purified with filter material and then injected back into the ground.The serpentine filter material was easy to harden with the increase in filtration amount,which affected the water quality.A superhydrophilic/underwater oleophobic serpentine filter material was successfully prepared by a simple method of coating modification,which exhibited long-lasting filtration of oily water,good filtration and anti-fouling properties,and resistance to harden.The film-forming material of the superhydrophilic/underwater oleophobic coating was composed of SiO_(2) particles with small size,which could completely and evenly cover the filter particle.The weight loss was only 7.6%after mechanical stirring for 90 min.Compared with the original filter material,the superhydrophilic/underwater oleophobic serpentine filter material showed a better anti-fouling ability and resistance to harden.The filtration of crude oil emulsion and oil slick sewage showed a better backwashing performance.After 35 cycles of continuous filtration of suspended solids in wastewater,the backwashing rate reached 78.4%.The results provided an effective method for the filtration of oily wastewater in the oilfield.

Amine-functionalized metal organic framework@graphene oxide as filler in PAEK-containing carboxyl group membrane for ultrafiltration with ultra-high permeability and strong fouling resistance

Achieving high fouling resistance and permeability using membrane separation technology in water treatment processes remains a challenge.In this work,a novel mixed-matrix membrane(MMM)(poly(arylene ether ketone)[PAEK]-containing carboxyl groups[PAEK-COOH]/UiO-66-NH_(2)@graphene oxide[GO])with superb fouling resistance and high permeability was prepared by the nonsolvent-induced phase separation method,by in-situ growth of UiO-66-NH_(2) on the GO layer,and by preparing hydrophilic PAEK-COOH.On the basis of the structure and performance analysis of the MMM,the maximum water flux reached 591.25 L·m^(-2)·h^(-1) for PAEK-COOH/UiO-66-NH_(2)@GO,whereas the retention rate for bovine serum albumin increased from 85.40%to 94.87%.As the loading gradually increased,the hydrophilicity of the MMMs increased,significantly enhancing their fouling resistance.The strongest anti-fouling ability observed was 94.74%,which was 2.02 times greater than that of the pure membrane.At the same time,the MMMs contained internal amide and hydrogen bonds during the preparation process,forming a cross-linked structure,which further enhanced the mechanical strength and chemical stability.In summary,the MMMs with high retention rate,strong permeability,and anti-fouling ability were successfully prepared.

Flexible,durable,and anti-fouling nanocellulose-based membrane functionalized by block copolymer with ultra-high flux and efficiency for oil-in-water emulsions separation

The clearwater obtained from stabilized oily wastewater has become a worldwide challenge.Nowdays,the area of oil/water emulsion separation materials have accomplished great progress,but still faces the enormous problems of low flux,poor stability,and pollution resistance.Nanocelluloses(cellulose nanocrystals(CNC))with the advantages of hydrophilicity,ecofriendliness,and regeneration are ideal materials for the construction of separation membranes.In this paper,a flexible,antifouling,and durable nanocellulose-based membrane functionalized by block copolymer(poly(N-isopropylacrylamide)-b-poly(N,Ndimethylaminoethyl methacrylate))is prepared via chemical modification and self-assembly,showing high separation efficiency(above 99.6%)for stabilized oil-in-water emulsions,excellent anti-fouling and cycling stability,high-temperature resistance,and acid and alkali resistance.More importantly,the composite membrane has ultra-high flux in separating oil-in-water emulsions(29,003 L·m^(−2)·h^(−1)·bar^(−1))and oil/water mixture(51,444 L·m^(−2)·h^(−1)·bar^(−1)),which ensures high separation efficiency.With its durability,easy scale-up,and green regeneration,we envision this biomass-derived membrane will be an alternative to the existing commercial filter membrane in environmental remediation.

A hyperbranched polymer-based water-resistant adhesive:Durable underwater adhesion and primer for anchoring anti-fouling hydrogel coating

Direct deployment of gluing and achieving durable robust adhesion in water is challenging due to difficulty in repelling interface water.This work reports a novel hyperbranched polymer-based water-resistant adhesive(HBPBA)based on Michael addition reaction of multi-vinyl monomers with dopamine and 3-aminophenylboronic acid.Upon encountering water,the HBPBA forms coacervates whose hydrophobic chains aggregate to displace interface water,and meanwhile the catechols exposing outwards contribute to underwater adhesion.The HBPBA can strongly glue diverse substrates including PTFE,PE,PET,ceramic,Ti and stainless steel.The HBPBA can maintain stable adhesion in different environments,such as tap water,simulated sea water,PBS,and a wide range of pH solutions(pH 2 to 10)for 3 months,supposedly due to the complexation of catechol with boronic acid.Intriguingly,HBPBA film can be bonded to the titanium surface as a primer,which firmly anchors the antifouling PNAGAPCBAA hydrogel coating through copolymerization of remaining double bonds in HBPBA and NAGA plus CBAA.The PNAGA-PCBAA hydrogel-modified titanium is biocompatible and shows outstanding antifouling ability both in vitro and in vivo.This work proposes a new strategy for creating underwater deployable and water-resistant adhesives that may find promising applications in engineering and biomedical fields.

Source of propagules of the fouling green macroalgae in the Subei Shoal,China

Since 2007,large-scale green tides dominated by Ulva prolifera consecutively bloomed in the Yellow Sea and caused great economic losses.The fouling U.prolifera on the Pyropia yezoensis aquaculture rafts in the Subei Shoal was regarded as the major source of the floating biomass.However,it was still unclear about the seed source of fouling green macroalgae attached on the rafts.In this study,the field surveys and the indoor experiments were conducted to reveal the source of propagules of the fouling green macroalgae on the rafts and to study the anti-fouling material for P.yezoensis aquaculture rafts which could possibly be a feasible strategy to control the green tides in the Yellow Sea.The results showed that（1） micro-propagules of several green macroalgal species,including U.prolifera,U.linza,U.compressa,U.flexuosa,and Blidingia sp.coexisted in the waters and sediments in the Subei Shoal and their proportion remarkably changed over time;（2） the bamboo poles with peeling treatment could significantly reduce the amount of U.prolifera micro-propagules attached.This study confirmed that the micro-propagules distributed in the Subei Shoal area were the precursors of the green tides,and provided a feasible method to control the Yellow Sea large-scale green tides at the beginning.

Slippery Surface with Petal-like Structure for Protecting Al Alloy: Anti-corrosion, Anti-fouling and Anti-icing

The harsh working environment affects the performance and usage life of Al and its alloys,thus limiting their application.In recent years,Slippery Liquid-infused Porous Surface(SLIPS)has attracted much attention due to excellent anti-corrosion,anti-fouling and anti-icing properties.This may be an effective way to improve the properties of Al and its alloys.Here,the SLIPS with petal-like structure was constructed on the Al alloy via simple hydrothermal reaction,Stearic Acid(STA)modification and lubricant injection.A variety of droplets(including oil-in-water emulsions)can slide on the SLIPS at a low angle,even the Sliding Angle(SA)of the water droplet is only 3°.Furthermore,the SLIPS exhibits outstanding mechanical and chemical properties.It can maintain fine oil-locking ability under high shearing force and keep slippery stability after immersion in acid/alkaline solutions.In addition,the SLIPS possesses excellent anti-corrosion,anti-fouling and anti-icing properties,which provides a new way to promote the application of Al and its alloys.Therefore,the SLIPS is expected to be an effective way to improve the properties of Al and its alloys,as well as play a role in anti-fouling and self-cleaning in construction,shipbuilding and automotive manufacturing industries,thereby expanding the practical application of Al and its alloys.

Tyramine-enhanced zwitterion hyaluronan hydrogel coating for anti-fouling and anti-thrombosis

Zwitterions have aroused much interest to endow implantable medical devices with anti-fouling and anti-thrombosis performance,due to their ability to form a hydrated layer that can provide a good barrier against protein and cell adhesion. Herein,tyramine modified sulfobetaine-derived sodium hyaluronan(HST) hydrogel coating was fabricated, in which hyaluronan(HA)was used as polysaccharide skeleton to graft zwitterionic sulfobetaine, and tyramine was introduced as crosslinker to construct both the network of hydrogel and a strong covalent bond between coating and substrate. Hydrogel coating was prepared by spin coating or painting HST prepolymer solution under ultraviolet light irradiation. The obtained HST hydrogel coating shows good stability. Moreover, in addition to its outstanding anti-fouling performance and good biocompatibility, it can effectively prevent thrombosis in blood circulation ex vivo. This work offers a universal strategy to prepare a high-performance anti-fouling and antithrombosis coating, which is expected to promote the development of functional coatings for biomedical materials.

Zwitterionic-phosphonate block polymer as anti-fouling coating for biomedical metals

Antifouling ability and blood compatibility are critically important in the development of medical metallic implants for clinical applications.Here,we report the zwitterionic-phosphonate block polymer as a new type of high-efficiency antifouling coating for metallic substrates.Six block polymers(pSBMA-b-pDEMMP)with different segment lengths(nSBMA:nDEMMP=10:25,40:25,100:25,75:5,75:40,75:100)were prepared and anchored on titanium alloy(TC4)substrates.1H nuclear magnetic resonance(NMR)results clearly showed the precise preparation of the block polymers.XPS analysis and water contact angle measurement indicated the successful construction of the block polymer on TC4 substrates.The relationship between the antifouling performance of the polymer coating and the length of pDEMMP and pSBMA segments in the block polymer was established.Results showed that the polymer containing the pSBMA segment above 40 repeat units could significantly inhibit protein adsorption,platelet adhesion,bacterial adhesion and cell adhesion,while the pDEMMP segment above 5 repeat units is able to generate stable zwitterionic polymer coating on TC4 substrates.This ease of production and high-efficiency antifouling modification strategy elucidated here may find broad application for biomedical implants and devices in clinical applications.

SYNTHESIS OF AMPHIPHILIC COMB-SHAPED COPOLYMERS USED FOR SURFACE MODIFICATION OF PVDF MEMBRANES

The synthesis of a novel amphiphilic comb-shaped copolymer consisting of a main chain of styrene-(N-(4- hydroxyphenyl) maleimide)(SHMI) copolymer and poly(ethylene glycol) methyl ether methacrylate(PEGMA) side groups was achieved by atom transfer radical polymerization(ATRP).The amphiphilic copolymers were characterized by ~1H-NMR, Fourier transform infrared(FTIR) spectroscopy and gel permeation chromatography(GPC).From thermogravimetric analysis (TGA),the decomposition temperature of SHMI-g-PEGMA is lower ...

Zwitterionic monolayer grafted ceramic membrane with an antifouling performance for the efficient oil-water separation

Enormous demands on the separation of oil/water(O/W)emulsions in various industries,such as petrochemical,food and pharmaceutical industries,are looking for high performance and energy-efficient separation methods.Ceramic membranes have been used to deal with O/W emulsions,for its outstanding characteristics of easy-operation,high-flux,and long-term stability.However,membrane fouling is still a challenge in the industrial application of ceramic membranes.Herein,antifouling ceramic membranes were fabricated by grafting zwitterions on the membrane surface via an environment-friendly two-step grafting method,which improves the antifouling property and permeability.Successful grafting of such zwitterion on the ceramic surface was assessed by the combination of FTIR and XPS characterization.More importantly,the hydration can be formed by electrostatic interactions layer on the modified membrane,which was confirmed by TGA characterization.The antifouling performance of prepared zwitterionic ceramic membranes in the separation of O/W emulsions was systematically tested.The results suggested that zwitterion can significantly improve the flux of ceramic ultrafiltration membrane,and can also improve antifouling property dramatically by reducing the irreversible fouling in the separation of O/W emulsions.Therefore,zwitterionic ceramic membranes hold promising potentials as an antifouling,highly efficient and green method in the practical purification of the O/W emulsions.

Self-cleaning Anti-fouling TiO2/Poly(aryl ether sulfone) Composite Ultrafiltration Membranes

A series of novel TiO2/poly(aryl ether sulfone) ultrafiltration membranes with anti-fouling and self-cleaning properties was designed and prepared. First, anti-photocatalytic degraded fluorine contained polv(aryl ether sulfone) matrix(PAES-F) was synthesized. Then the composite membranes were prepared via TiO2 nanopartides and PAES-F polymer matrix by solution blending and non-solvent induced phase inversion methods. Further, separation efficiency, fouling behavior and self-cleaning property of the composite ultrafiltration(UF) membranes were investigated by dead-end filtration experiments using a polyacn lamide solution. The composite UF membranes exhibited outstanding self-cleaning efficiency and anti-photocatalytic degraded property after exposure to simulated sunliglit irradiation.The water flux recovery ratios(FRR)of the optimal composite UF membranes could reach 74.24%, which was attributable to photocatalytic degradation of the organic contaminant by TiO2. And the retention rates of the composite UF membranes could maintain over 97%, which indicated the excellent photocatalytic degradation resistance of the fluorine contained PAES-F matrix. The novel high perfomiance composite UF membranes have a broad application prospect in water treatment.

Simple fabrication of Cu^(2+)doped calcium alginate hydrogel filtration membrane with excellent anti-fouling and antibacterial properties

Herein,copper ion doped calcium alginate(Cu^(2+)/CaAlg)composite hydrogel filtration membranes were prepared by using natural polymer sodium alginate(NaAlg)as raw material.The thermal stability and structure of the composite membranes were characterized by thermogravimetric analysis and infrared spectroscopy.The mechanical strength,anti-fouling performance,hydrophilicity and filtration performance of the membrane were studied.The results show that Cu^(2+)/CaAlg hydrogel membrane has excelle nt mechanical properties and thermal stability.The anti-swelling ability of the membrane was greatly enhanced by doping Cu^(2+).After three alternate filtration cycles,the flux recovery rate of Cu^(2+)/CaAlg hydrogel membrane can still reach 85%,indicating that the membrane has good antipollution performance.When the operation pressure was 0.1 MPa,the rejection of coomassie brilliant blue G250 reached 99.8%with a flux of 46.3 L m^(-2)h^(-1),while the Na_(2)SO_(4) rejection was less than 10.0%.The Cu^(2+)/CaAlg membrane was recycled after 24 h in the filtration process,and its flux and rejection rate did not decrease significantly,indicating that the hydrogel membrane has long-term application potential.The Cu^(2+)/CaAlg membrane has a wide range of applications prospect in dye desalination,fine separation and biopharmaceutical technology fields.

Atomic layer deposition of Al_2O_3 on porous polypropylene hollow fibers for enhanced membrane performances

Porous polypropylene hollow fiber(PPHF) membranes are widely used in liquid purification. However, the hydrophobicity of polypropylene(PP) has limited its applications in water treatment. Herein, we demonstrate that, for the first time, atomic layer deposition(ALD) is an effective strategy to conveniently upgrade the filtration performances of PPHF membranes. The chemical and morphological changes of the deposited PPHF membranes are characterized by spectral, compositional, microscopic characterizations and protein adsorption measurements. Al_2O_3 is distributed along the cross section of the PP hollow fibers, with decreasing concentration from the outer surface to the inner surface. The pore size of the outer surface can be easily turned by altering the ALD cycles. Interestingly, the hollow fibers become much more ductile after deposition as their elongation at break is increased more than six times after deposition with 100 cycles. The deposited membranes show simultaneously enhanced water permeance and retention after deposition with moderate ALD cycle numbers.For instance, after 50 ALD cycles a 17% increase in water permeance and one-fold increase in BSA rejection are observed. Moreover, the PP membranes exhibit improved fouling-resistance after ALD deposition.

Air-blast anti-fouling cleaning for aquatic optical sensors

In order to solve the problem of fouling of submerged optical instruments,an air-blast cleaning mechanism was integrated into an optical sensor used for measuring suspended sediment concentration(SSC)in natural waters.Laboratory experiments in a manually created fouling environment were conducted to observe the fouling process on sensor cases made of different materials,and to verify the effectiveness of air-blast cleaning in reducing fouling.Results indicated that sensors with an aluminum case experienced more serious bio-fouling than that with polyethylene case,and the air-blast cleaning mechanism was capable of reducing fouling effect on sensor signals.So the submerged optical instruments should avoid using metal materials.The duration and frequency of air-blast cleaning can be determined and adjusted depending on actual field conditions.

Environmentally friendly expanded graphite-doped ZnO superhydrophobic coating with good corrosion resistance in marine environment

Designing and fabricating the marine anti-corrosion materials without fluorine by superhydrophobic method is a huge challenge. In this study, an environmentally friendly composite coating was prepared by combing modified expanded graphite(EAG) with nano zinc oxide(ZnO). This coating showed superhydrophobic surface and good corrosion resistance. Fourier transform infrared spectroscopy(FITR), X-ray diffraction(XRD),and scanning electron microscopy(SEM) were used to characterize the materials in fabricating process of the coating. The properties of three composite coatings(ZnO,EAG, and EAG@ZnO) were analyzed, including surface roughness, water contact angle, corrosion resistance, selfcleaning and anti-fouling. The combination of ZnO and EAG caused a big water contact angle, leading superhydrophobic surface of the composite coatings. The electrochemical results showed that the superhydrophobic EAG@ZnO coating had a larger capacitive arc diameter and charge transfer resistance, indicating the enhanced anti-corrosion resistance. Meanwhile, the EAG@ZnO coating also showed good self-cleaning and anti-fouling performance according to solid and liquid pollutants tests.In addition, the mechanical properties and stability of the superhydrophobic EAG@ZnO coatings were evaluated by knife peeling and finger scratch tests. In summary, these superhydrophobic and anti-fouling EAG@ZnO composite coatings provide a potential application in marine corrosion and protection field.