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.     

乳状液膜分离技术的发展与应用

乳状液膜分离技术综合了固体膜分离法和溶剂萃取法的特点,是一种新兴的节能型分离手段。介绍了乳状液膜的组成和分类,并对其传质机理和分离过程中的影响因素进行了分析。对乳状液膜在废水处理和冶金工业方面的应用进行了具体介绍。     

SiO2改性聚丙烯纤维棉对油水乳状液的高效分离

近年来,基于特殊润湿性理论制备表面具有微纳米粗糙结构的多孔材料成为油水分离领域研究的重点。为了满足不同环境下对不同形式油-水乳状液高效高通量分离的需求,该研究利用纳米SiO2颗粒对聚丙烯（PP）纤维棉有针对性地亲（疏）水改性,构建了系列不同润湿性和粗糙度的PP纤维棉,探究了不同孔隙度和表面能的PP纤维棉对W/O及O/W型乳状液的分离性能,结果表明,经过亲（疏）水改性后的PP纤维棉对水/正己烷和水/甲苯乳状液的分离效率都高于99.5%,通量高于700 L/(m2·h),并针对不同形式油-水乳状液阐释其相应的分离机制,为后续油-水乳状液分离材料的科学设计和可控制备提供了理论依据。     

Recycling of waste attapulgite to prepare ceramic membranes for efficient oil-in-water emulsion separation

Large-scale application of ceramic membranes is restricted by high cost resulting from raw materials and sintering process. In this study, low-cost ceramic membranes were prepared with waste attapulgite (WAT) and α-Al₂O₃ as starting materials and used for oily wastewater treatment. The optimal membrane sintered at 1100 °C possessed excellent properties, with open porosity of 41.6%, flexural strength of 37.2 MPa and average pore size of 0.40 μm. The membrane also displayed outstanding permeability and chemical stability. The hydrophilicity and underwater oleophobicity were enhanced after surface modification. When used for oil-in-water emulsion filtration, the permeate flux reached 236.8 L m^?2 h^?2 bar^-1 under a low transmembrane pressure of 0.2 bar and the oil rejection exceeded 99%. Membrane cleaning with a simple ultrasonic treatment could easily achieve flux recovery. This study proposed a feasible strategy for both solid waste utilization and oily wastewater treatment.     

Multifunctional fly ash-based GO/geopolymer composite membrane for efficient oil-water separation and dye degradation

Membrane fouling and separation materials with low cost and high efficiency are challenges for membrane separation technology in wastewater treatment. Superhydrophilic and underwater superoleophobic membranes show broad application prospects in oily wastewater treatment because of their high permeability, selectivity, and antifouling performance; however, they are generally ineffective for organic pollutant molecules. In this study, a novel graphene oxide (GO)/geopolymer composite membrane with superhydrophilic and underwater superoleophobic characteristics was prepared by dipping a mixed slurry of GO and fly ash-based geopolymer onto a stainless steel mesh via a facile self-assembly process. The results show that GO could adjust the hydrophilicity and water flux of composite membranes. The composite membrane containing 0.4 wt% GO (4GO/GCM) had the best hydrophilic, water flux of 1363 kg/(m²·h), and high separation efficiencies (≥98.2%) for oil-water mixtures and oil-in-water emulsions under gravity-driven. In addition, the 4GO/GCM sample exhibited excellent stability under harsh conditions, including hot water and strong acid, alkali, and salt solutions. Importantly, the sample derived from fly ash exhibited unique photocatalytic degradation performance for organic dye molecules under simulated solar-light irradiation. Thus, it is believed to this strategy has substantial potential for high-value utilization of fly ash and the sustainable treatment of oily and dye wastewater.     

Preparation and anti-fouling property of carboxybetaine-based zwitterionic PVDF membrane

This work describes the synthesis and anti-fouling properties of poly(vinylidene fluoride) membrane, grafted with carboxybetaine-based zwitterions. An amphiphilic copolymer, poly(vinylidene fluoride)-graft- poly(N,N-dimethylamino-2-ethylmethacrylate) (PVDF-g-PDMAEMA), was synthesized by radical graft copolymerization, followed by casting the copolymer into a flat membrane, by an immersed phase inversion method. PVDF-g-PDMAEMA membrane was reacted with sodium chloroacetate (SCA) to yield a carboxybetaine-based zwitterionic surface. The membrane showed significantly enhanced hydrophilicity, due to the hydration ability of carboxybetaine-based zwitterions, which inhibited protein adsorption. Compared to pristine PVDF-g-PDMAEMA membrane, carboxybetaine-based zwitterionic membrane exhibited a higher flux recovery in the cyclic filtration.     

Synthesis and characterization of mullite-ZrO2 porous fibrous ceramic for highly efficient oil-water separation

This work aimed to proposing a new strategy for preparing the mullite-ZrO₂ porous fibrous ceramic used as alternative matrix material for oil-water separation by the aqueous gel-casting method. The properties of the fabricated porous fibrous ceramics in terms of microstructure, phase composition, apparent porosity, bulk density and compressive strength were investigated and the separation behavior was predicted by analyzing the structural changes. It is demonstrated that the phase composition of green bodies consisted of bayerite, boehmite, ZrSiO₄ and YSZ, and the sintered sample contained mullite, ZrO₂ and YSZ. As the YSZ fibers increased, the porosity of the fabricated porous ceramic increased with the maximum value of 70.65% due to the formation of more pores caused by YSZ fibers. Moreover, a significant increase in compressive strength (up to 9.52–21.86 MPa) was observed with the increase of YSZ fibers. Therefore, the fabricated porous ceramics could be appropriative for advanced applications of separation membranes for oil-water separation.     

乳状液膜分离技术及其在废水处理中的应用

介绍了乳状液膜的发展、基本概念、分类及其制备方法,对乳状液膜的传质机理和溶胀稳定性进行了分析。对乳状液膜分离技术在废水处理中的应用进行了具体介绍,并对乳状液膜分离技术的发展进行了分析和展望。     

聚乙烯醇微球抗污染动态膜的制备及性能

采用静电自组装和过滤预涂技术将表面富含羟基、具有强亲水性和电负性的聚乙烯醇微球(polyvinyl alcohol micro-sphere, PVA-MS)与工业滤布基膜相结合,分别制备无滤饼标准型和完全堵塞型PVA-MS动态膜。对膜的表征和性能的对比研究表明, PVA-MS组成的动态膜结构能明显改善基膜的亲水性、负电性。自组装PVA-MS动态膜的有效过滤孔径为2.1 μm, 清水阻力为1.02×10¹⁰ m^-1, 对基膜的截留性能基本没有提高, 预涂PVA-MS动态膜的有效过滤孔径为0.4 μm, 清水阻力为1.07×10¹¹ m^-1, 对浊度为21.34 NTU和TOC为18.3 mg•L^-1的上清液过滤出水为0.23 NTU和9.4 mg•L^-1, 分别提高基膜截留效果20%和30%。动态膜不可逆污染的去除性能研究表明, 自组装PVA-MS动态膜在化学清洗后能保持大部分PVA-MS的存在,预涂PVA-MS动态膜利用物理反冲洗可完全去除不可逆膜污染,再预涂后即再生。     

表面活性剂对乳状液膜分离效率的影响

综述了基于表面活性剂的乳状液膜分离技术的原理,包括不含流动载体的I型传递机理和含流动载体的Ⅱ型传递机理;介绍了表面活性剂的种类、浓度对乳状液膜的稳定性、分离效率的影响;提出了使用乳状液膜分离技术时选用表面活性剂的原则,并展望了乳状液膜分离技术的发展前景。     

Synthesis and characterization of superoleophobic fumed alumina nanocomposite coated via the sol-gel process onto ceramic-based hollow fibre membrane for oil-water separation

Oily wastewater treatment is a global challenge due to the substantial amount of effluent resulted from many industrial and domestic activities. To overcome the challenge of using existing treatment approach and fouling, superoleophobic coatings were fabricated. In this study, a superoleophobic membrane surface was obtained using the sol-gel technique with perfluorooctanoate (PFO), poly (diallyl dimethylammonium chloride) (PDADMAC), and nanoparticles as complex-polymer nanocomposites. The effects of coating cycles on the surface structure, chemical properties, surface chemistry, and oleophobicity of the surface were examined using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and oil contact angle measurement. The results showed that the coated layer successfully adhered to the substrate surface. However, the chemical stability with respect to oil contact angle (OCA) revealed a decline at pH 7 and pH 9 and maintained stability at pH 3. Besides, oil flux at 63.0 L/m². h was achieved for PDADMAC-Al₂O₃/44 wt% PFO and the highest separation efficiency of 98% was obtained. Furthermore, the oil rejection decreases as the oil concentration increases from 1 to 3 g/L. OCA of 155° was obtained after 5 coating cycles. Apart from mitigating substrate fouling, the superoleophobic and superhydrophilic coating can be applied to a ceramic-based hollow fibre membrane and efficiently used for the separation of oil from oily wastewater.     

磺化聚醚砜/纳米TiO2复合超滤膜制备及其抗污染机理

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.     

浓乳液聚合制备优先脱醇渗透蒸发分离膜

提出了一种以浓乳液聚合直接浇注制备新型有机硅类渗透蒸发分离膜的新方法。考察了乙醇浓度、分离时间与渗透蒸发分离性能之间的关系,表征了有机硅浓乳液聚合过程中的乳胶粒子形态与成膜后粒子堆砌的微观结构。结果表明,利用膜中乳胶粒子间微通道的极性效应可以有效地分离醇/水混合物中的醇,且优先脱醇效果明显,分离性能良好。在乙醇/水混合物的渗透蒸发膜分离实验中,其渗透通量为4.7～165g·m-2·h-1,分离因子为1.0～11.3,分离选择性最好时的料液中乙醇的质量分数为33.41%。     

Electrospinning organic solvent resistant preoxidized poly(acrylonitrile) nanofiber membrane and its properties

A high performance preoxidized poly(acrylonitrile) (O-PAN) nanofiber membrane with excellent solvent resistance, thermal stability and flexibility was fabricated by the preoxidation of electrospun PAN nanofiber membrane. The performance of resultant O-PAN nanofiber membrane was optimized by altering the PAN concentration and preoxidation temperature. The results showed that the O-PAN nanofiber membrane which made from PAN concentration of 14% (mass) and preoxidation temperature of 250.0 ℃ have a more optimal comprehensive performance. In the long-term separation test of SiO₂ particle (1 μm) in DMAc suspension, the permeate flux of O-PAN nanofiber membrane stabilized at 227.91 L·m^-2·h^-1 (25 ℃, 0.05 MPa) while the SiO₂ rejection above 99.6%, which showed excellent solvent resistance and separation performance. In order to further explore the application of the O-PAN nanofiber membrane, the O-PAN nanofiber membrane was treated with fluoride and used in oil/water separation process. The O-PAN nanofiber membrane after hydrophobic treatment showed excellent hydrophobicity and good oil/water separation performance with the permeate flux about 969.59 L·m^-2·h^-1 while the separation efficiency above 96.1%. The O-PAN nanofiber membrane exhibited a potential application prospect in harsh environment separation.     

Design of a super-hydrophilic/super-oleophobic g-C3N4/Ti(OH)4/PFOA nanocomposite coated mesh as a smart nanofilter with robust anti-fouling properties for separation of oil and water emulsions

The design and development of efficient approaches for water–oil separation have had widespread interest. This study aimed to synthesize nanocomposites based on Ti(OH)₄ and g-C₃N₄ nanosheets (CN-NS) to show experimentally that the inclusion of Ti(OH)₄ nanoparticles of 9.2 nm size into CN-NS leads to an improved oil-water separation efficiency and anti-fouling performance. So, a novel, reusable, and recyclable super-hydrophilic/underwater super-oleophobic CN-NS/Ti(OH)₄ nanocomposite-coated stainless steel mesh was developed to separate oil-in-water emulsions. Super-wettability was obtained in the CN-NS/Ti(OH)₄ nanocomposite with WCA = 0° and UOCA = 154°, respectively, showing significant super-hydrophilicity and underwater super-oleophobicity. Surface hydrophilicity increased after anchoring Ti(OH)₄ on the CN-NS surface, resulting from oxygen-containing functional groups and consequently making defects on the mesh surface. Enhanced underwater oleophobicity of nanocomposite coated mesh is attributed to its higher surface roughness, which is a result of its micro-nano meter and mesoporous hierarchical structure. Moreover, the self-cleaning property of the as-prepared mesh was demonstrated by visible light irradiation on the contaminated mesh. In addition, perfluorooctanoic acid (PFOA) reduced energy in CN-NS/Ti(OH)₄/PFOA mesh, resulting in a super-hydrophilic/super-oleophobic mesh. The CN-NS/Ti(OH)₄/PFOA nanocomposite-coated filter was observed to separate water from a 1 wt% water-in-oil emulsion at 0.2 bar pressure with a filtration flux of 317.2 L m⁻² h⁻¹ and 95% separation efficiency.     

超亲水SiO2修饰膜的构建及其油水乳液分离性能

采用硅溶胶和多巴胺作为修饰剂,通过一步反应在微孔聚丙烯膜(MPPM)表面构建了SiO₂修饰层。利用FTIR、ESEM和EDX对膜进行了表征,发现膜表面SiO₂颗粒分布非常均匀。水/油接触角及纯水通量实验结果表明,修饰膜具有超亲水性及水下超疏油性,透水能力强,水通量大[在0.1 MPa时,水通量高达(5100±500)L·m^-2·h^-1]。油水乳液分离结果表明,修饰膜能有效分离油水乳液,在0.05 MPa时,油水乳液水通量达2830 L·m^-2·h^-1,油截留率达99.8%以上,即使过膜压力增大到0.15 MPa,油截留率也能保持在99%以上,且膜表面的油污可用水清洗除去,展现出很好的应用前景。     

聚偏氟乙烯膜亲水改性及其乳液分离与重金属吸附应用

聚偏氟乙烯（PVDF）膜因其优异的化学和力学稳定性而被广泛应用于水处理领域,但PVDF膜本身的疏水性,容易使其在处理含油废水的过程中被油滴污染,造成膜孔堵塞。以PVDF微滤膜为基底,通过单宁酸（TA）和聚乙烯亚胺（PEI）共沉积形成了TA/PEI黏附层,经戊二醛共价交联和接枝半胱氨酸（Cys）,制备了一种PVDF改性膜（PVDF@TA/PEI-Cys）。改性后的PVDF膜具有良好的亲水性和水下超疏油性,水接触角和水下油接触角分别为22.2°和150.2°。在0.09 MPa下,PVDF@TA/PEI-Cys膜的纯水通量达6328 L/（m²·h）,水包油型乳液分离效率高达99.9%。此外,该改性膜还可同时吸附水中的汞离子,最大吸附量为24.7 mg/g。     

鳞片状BiVO4不锈钢网涂层的制备及其在油水分离中的应用

随着石油泄漏事故的频繁发生和工业含油废水的大量排放,现代化工油水分离问题日益突出。具有特殊润湿性的材料可以选择性透过水或油,分离效率高且操作简单而广泛应用于油水分离。本文以不锈钢网为基底,通过液相法可控制备得到具有不同尺寸、排列的BiVO₄纳米片涂层。通过扫描电子显微镜、原子力显微镜、接触角测量仪对其表面形貌与润湿性能进行表征,研究BiVO₄纳米片尺寸和排列对水下疏油性能的影响。结果表明当不锈钢网表面均匀生长着鳞片状BiVO₄,且这些纳米片随机放射排列时,涂层水下油接触角达到了165.1°,倾斜角仅为2.0°,具有水下超疏油性质。将该涂层用于油水混合物的分离,分离效率均在95.0%以上且分离通量最大可达1.4×10⁴L/(m²·h),在油水分离领域展现出巨大的应用潜力。     

A polypropylene melt-blown strategy for the facile and efficient membrane separation of oil-water mixtures

Porous materials with selective wettability and permeability have significant importance in oil-water separation, but complex fabrication processes are typically required to obtain the desired structures with suitable surface chemistry. In this work, an industrial melt-blown strategy that utilized commercially available polypropylene (PP) was used for the large-scale fabrication of superhydrophobic/superoleophilic membranes with staggered fabric structures. These membranes could readily separate different oils including pump oil and crude oil from various aqueous solutions such as strongly acidic, alkaline, and saline media. In addition, the separation efficiencies of these membranes exceeded 99%, and they could remain functional even after exposure to corrosive media. We anticipate that this work will further the design of membranes and enhance their applicability in oil-water separation, and provide researchers and engineers with a more effective tool for performing challenging separations and mitigating pollution.     

Fabrication of BSCF-based mixed ionic-electronic conducting membrane by electrophoretic deposition for oxygen separation application

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF), which exhibits a high mixed oxide ionic-electronic conduction, was used for the fabrication of an oxygen separation membrane. An asymmetric structure, which was a thin and dense BSCF membrane layer supported on a porous BSCF substrate, was fabricated by the electrophoretic deposition method (EPD). Porous BSCF supports were prepared by the uniaxial pressing method using a powder mixture with BSCF and starch as the pore-forming agent (0–50 wt.%). The sintering behaviors of the porous support and the thin layer were separately characterized by dilatometry to determine the co-fired temperature at which cracking did not occur. A crack-free and thin dense membrane layer, which had about a 15 μm thickness and >95% relative density, was obtained after optimizing the processes of EPD and sintering. The dense/porous interface was well-bonded and the oxygen permeation flux was 2.5 ml (STP) min⁻¹ cm^-2 at 850 °C.