High-flux whisker layer ceramic membrane prepared by gel spin-coating method for low-pressure oil/water emulsion filtration

Insufficient permeability and membrane fouling significantly influence the efficiency of ceramic microfiltration (MF) membranes in oil/water emulsion treatment. In this study, a high-flux whisker layer ceramic MF membrane with super-hydrophilicity was successfully fabricated through gel-spin coating method and a low-temperature oxidation method, which was used to separate oil/water emulsion. The effects of the whisker layer and surface wettability were systematically investigated, and the mechanism of in-situ gelling and pore size distribution was proposed. The super-hydrophilic ceramic MF membrane with an average pore size of 250 nm exhibited a high gas flux of 934 m³/(m²·h·bar) and excellent pure water flux of 9754 L/(m² h bar). Even after a long-term circulating filtration process, the super-hydrophilic ceramic MF membrane still maintained a high water flux of over 50 L/(m²·h) at a transmembrane pressure of 5 KPa during the treatment of oil-in-water emulsion with a concentration of 1000 mg/L. Overall, the developed ceramic MF membrane demonstrated high permeability and excellent anti-fouling performance, making it a promising candidate for oil/water emulsion wastewater treatment.     

A TiO2 modified whisker mullite hollow fiber ceramic membrane for high-efficiency oil/water emulsions separation

Design and preparation of membranes with ultrahigh separation performance and antifouling property for oil-in-water (O/W) emulsions remains challenging. In this study, a high flux mullite/TiO₂ ceramic composite membrane was prepared via multi-precipitation of TiO₂ on a whisker mullite hollow fiber support synthesized by combining phase inversion and high-temperature sintering techniques. The results showed that the generated whisker mullite structure improved the permeation flux, and the micro-nano structured TiO₂ functional layer endowed the membrane surface with superhydrophility and stability. The retention of the optimal composite membrane (M20T13) that was soaked in the titanium solution 20 times for 13 min each time for the O/W emulsions like n-hexane, toluene and engine oil maintained over 98 %, and the flux after 6 h filtration was 668.34 L·m⁻²·h⁻¹, 487.25 L·m⁻²·h⁻¹ and 258.66 L·m⁻²·h⁻¹, respectively, much higher than that of the optimal substrate (F3A1, mass ratio of fly ash: Al₂O₃ = 3:1). Moreover, the flux recovery rate of M20T13 was much higher than that of F3A1 after chemical backwashing. This work manifests great potential in O/W treatment fields.     

Treatment of oily wastewater using low cost ceramic membrane: Comparative assessment of pore blocking and artificial neural network models

This work addresses the performance and modeling of the separation of oil-in-water (o/w) emulsions using low cost ceramic membrane that was prepared from inorganic precursors such as kaolin, quartz, feldspar, sodium carbonate, boric acid and sodium metasilicate. Synthetic o/w emulsions constituting 125 and 250 mg/L oil concentrations were subjected to microfiltration (MF) using this membrane in batch mode of operation with varying trans-membrane pressure differentials (ΔP) ranging from 68.95 to 275.8 kPa. The membrane exhibited 98.8% oil rejection efficiency and 5.36 × 10⁻⁶ m³/m² s permeate flux after 60 min of experimental run at 68.95 kPa trans-membrane pressure and 250 mg/L initial oil concentration. These experimental investigations confirmed the applicability of the prepared membrane in the treatment of o/w emulsions to yield permeate streams that can meet stricter environmental legislations (<10 mg/L). Subsequently, the experimental flux data has been subjected to modeling study using both conventional pore blocking models as well as back propagation-based multi-layer feed forward artificial neural network (ANN) model. Amongst several pore blocking models, the cake filtration model has been evaluated to be the best to represent the fouling phenomena. ANN has been found to perform better than the cake filtration model for the permeate flux prediction with marginally lower error values.     

Highly porous fibrous mullite ceramic membrane with interconnected pores for high performance dust removal

Porous fibrous mullite ceramic membranes with different content of fibers were successfully fabricated by molding method for dust removal. The properties of the samples, such as microstructure, porosity, bulk density and mechanical behavior were analyzed. Owing to the highly porous three-dimensional structure of ceramic membranes, all the samples exhibited low density (lower than 0.64?g/cm³), high porosity (higher than 73%), low linear shrinkage (lower than 1.0%) and low thermal conductivity (lower than 0.165?W/mK). Significantly, the as-prepared porous ceramic membrane possessed of enhanced dust removal efficiency with almost 100% for 3–10?µm, 97% for 1.0?µm, 87% for 0.5?µm and 82% for 0.3?µm dust particles in diameter from dust-laden air passed through the test module. Moreover, the pressure drop was lower than 80?Pa when the airflow linear velocity reached 1.25?m?min^?1. The results indicated that the ceramic membranes prepared in this work were promising high efficiency dedusting materials for the application in gas filtration field.     

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.     

烧结温度对TiO2/不锈钢中空纤维复合膜结构和性能的影响

不锈钢中空纤维膜基膜孔径大,直接涂覆分离层容易产生表面缺陷。在二氧化钛悬浮液中加入聚乙烯醇作为黏结剂,通过真空辅助抽滤法在不锈钢中空纤维基膜表面形成一层均匀的分离层。通过高温烧结得到了TiO₂/不锈钢中空纤维复合膜,考察了烧结温度对于TiO₂/不锈钢中空纤维复合膜表面分离层形貌和结构的影响。不同烧结温度时,TiO₂/不锈钢中空纤维复合膜的表面形貌有所差异;随着烧结温度的升高,不锈钢复合膜的孔径和纯水通量均先升高再下降。当烧结温度为500℃时,表面涂层均匀,孔径分布集中,水通量较高。最后,以SPT-500膜测试了水包油乳液分离效果,分离效率达到99%以上,且具有良好的抗污染性能。     

基于膜射流乳化技术的TiO2大孔陶瓷制备方法研究

A novel method to prepare macroporous TiO2 ceramic, based on membrane emulsification was reported.To solve the paradox between the instability of nonaqueous emulsion and long emulsification time required by themembrane emulsification, a two-stage ceramic membrane jet-flow emulsification .was. proposed. Discussion wasconducted on the evolution of droplet size with time, which followed the Ostwalcl npemng theory. And a monodispersed nonaqueous emulsion with an average droplet size of 1.6μm could beprepared. Using the emulsion, as atemplate, TiO2 ceramics with an average pore size ot 1.1 μm were obtaineed. Tne material could be prospectivelyused for preparation of catalysts, adsorbents, and membranes.     

热致相分离法制备聚乙烯/纳米二氧化钛共混膜

采用相对分子质量为130 000的聚乙烯(PE)为膜材、DIDP为稀释剂、平均直径为180 nm的TiO2粉末作添加剂,用热致相分离(TIPS)法制备了PE膜和PE/TiO2共混膜。研究了共混组成和冷却速率对膜结构的影响。所有制备的膜均是海绵状孔,冷却速率越大,膜孔越小。对PE质量分数为15%,当PE与TiO2的质量比大于1时,TiO2在膜内的分布不均匀,当PE与TiO2的质量比为0.5时,TiO2能比较均匀的分布于膜内。共混膜浸于水中经过紫外照射后,其亲水性显著增加。     

Characteristics of in-situ synthesized Hydroxyapatite on TiO2 ceramic via plasma electrolytic oxidation

The biocompatibility properties of Ti scaffolds can be improved significantly by hydroxyapatite (HA) composite coating. We successfully coated the surface of the Ti substrates by in-situ formation of HA nanocrystals on TiO₂ sublayer under calcium acetate and trisodium phosphate electrolytes through the plasma electrolytic oxidation (PEO) process. The effects of the process parameters and passivation on the characteristics of the coated substrates were studied using X–ray diffraction, Fourier-transform infrared spectroscopy, Field emission scanning electron microscopy, and Energy–dispersive X–ray spectroscopy. The systematically controlled experimental studies indicated that using the higher calcium/phosphorous ratio in the electrolyte enhances the micro arcs power and consequently, thickens the synthesized HA layer. The HA nanocrystals were tailored on the walls and edges of the discharge channels due to the locally concentrated heating zones, which consequently resulted in noticeable amounts of Ca and P dopants in porous TiO₂.     

Construction of membrane formation system with low critical solution temperature for preparing hydrophilic polysulfone membrane via modified reverse thermally induced phase separation process

This paper presents a novel method to construct a membrane formation system featuring a low critical solution temperature (LCST) by incorporating hydroxy terminated hyperbranched polyester (HBPE) into polysulfone (PSF) casting solution. PSF membranes were developed by modified reverse thermally induced phase separation (m-RTIPS) process while the introduction of HBPE improved the hydrophilicity of the membrane. The critical properties of the flat-sheet PSF membranes were discussed in detail. The cloud point decreased as the HBPE concentration was increased. When membranes were prepared via m-RTIPS, the region of bicontinuous finger-like pores in the sublayer gradually broadened. The membranes showed better permeation properties, larger pore size, and better mechanical properties than those of the membranes prepared via non-solvent-induced phase separation (NIPS) process. Furthermore, no matter the enhanced hydrophilicity of membrane or m-RTIPS membrane-forming mechanism was beneficial to the anti-fouling properties. In general, the membrane MPSF-8-b had relatively high flux, good hydrophilicity and excellent mechanical properties at 0.8 wt.% HBPE content, and the pure water flux recovery of the membrane was increased to 55.2%.     

Preparation and membrane performance of poly(ethylene-co-vinyl alcohol) hollow fiber membrane via thermally induced phase separation

Poly(ethylene-co-vinyl alcohol) (EVOH) hollow fiber membranes with ultrafiltration performance were prepared from EVOH/glycerol systems via thermally induced phase separation (TIPS). The diluent glycerol was used as bore liquid to make a lumen of the hollow fiber for the purpose of prevention of the diluent evaporation and the larger pores formation at the inner surface of the hollow fiber. The obtained hollow fiber membranes showed asymmetric structures with skin layer near the outer surface, the larger pores just below the skin layer and the smaller pores near the inner surface. The formation of the larger pores near the outer surface was due to the enhanced pore growth by the water penetration. Some primary factors affecting the structure and performance of the membranes such as ethylene content (EC) in EVOH, cooling water bath temperature and take-up speed were studied extensively. The water permeability can be improved by increasing the water bath temperature and the take-up speed and by decreasing the EC. Both the pore size at the outer surface and the connectivity between the pores have to be considered together to understand the experimental result of the water permeability and the solute rejection.     

致密超细球形氧化铝制备性能良好的陶瓷超滤膜

热等离子体制备的超细球形氧化铝具有表面致密光滑、分散性好等特点,本工作以超细球形氧化铝为原料,通过浸渍提拉烧结法,制备了孔径分布窄、渗透通量高的陶瓷超滤膜,研究了烧结温度对陶瓷膜微孔结构的演化、孔径分布和渗透通量的影响。随后对1250℃下烧结的陶瓷膜进行了纳米硅水分散液过滤处理,采用不同堵塞模型分析了陶瓷膜过滤纳米硅水分散液的膜污染过程。结果表明,通过调节烧结温度调控陶瓷膜的微孔结构,当烧结温度为1250℃时,陶瓷膜的孔径分布较窄,孔径大小为25?65 nm,渗透通量为986.4 L/(m2?h)。超细球形氧化铝粒径分布较窄及表面致密光滑有助于1250℃下烧结形成均匀的烧结颈,提供了陶瓷膜较窄的孔径分布。对1250℃下烧结的陶瓷膜进行了纳米硅水分散液过滤处理后其浊度下降为0.231 NTU,浊度去除率达99.96%。采用不同堵塞模型分析了陶瓷膜过滤纳米硅水分散液的膜污染过程,结果表明,纳米硅水分散液的堵塞模型是滤饼过滤,属于可逆污染。     

疏水SiO2/PTFPMS杂化复合膜的制备及其气体分离性能

为了提高气体分离膜的耐溶胀特性,以多孔聚醚酰亚胺（PEI）为支撑层,采用溶液共混法制备了疏水SiO₂/PTFPMS杂化复合膜,研究了疏水SiO₂质量共混比对膜形态、耐溶胀性以及不同操作压差下的纯气渗透分离性能的影响。光学显微照片显示,当共混比不超过0.018时,杂化膜的透明度较高,表明疏水SiO₂与PTFPMS具有较好的相容性;当SiO₂与PTFPMS的共混比超过0.018时,SiO₂团聚明显。SEM表征结果显示,杂化膜表面光洁,断面杂化涂层紧密贴合支撑层。疏水SiO₂/PTFPMS杂化膜在异辛烷中的溶胀度为0,在乙酸乙酯中的溶胀度比PTFPMS均质膜的下降了11.9%,显示了其优异的耐溶胀性能。在操作压力为1.0 MPa,操作温度为25℃下,SiO₂共混比为0.012时,疏水SiO₂/PTFPMS杂化复合膜的CO₂渗透通量达到最高156.1GPU,CO₂/N₂选择性为15.86。     

Asymmetric TiO2 hybrid photocatalytic ceramic membrane with porosity gradient: Effect of structure directing agent on the resulting membranes architecture and performances

Asymmetric TiO₂ hybrid photocatalytic ceramic membranes with porosity gradient have been fabricated via acid-catalyzed sol–gel method. Different structure directing agents (SDAs) i.e. Pluronic P-123, Triton X-100, Tween 20 and Tween 80 were incorporated in the preparation of TiO₂ sol to obtain a porous multilayered TiO₂ coated on the alumina ceramic support. Six different SDA-modified membrane specimens were fabricated. Four of which were coated with the TiO₂ sols prepared using only one type of SDA. The remaining two specimens were fabricated via multilayer coating of different TiO₂ sols prepared using different types of SDAs. Physico-chemical and morphological properties of different TiO₂ layers were thoroughly investigated. The membrane M1 which had the most porous TiO₂ sub-layers showed a high pure water permeability of 155 L m⁻² h⁻¹ bar⁻¹. The membrane showed a relatively high Rhodamine B (RhB) removal of 2997 mg m⁻² over 8 h treatment duration in the batch photoreactor, second only to the Pluronic-based TiO₂ membrane (specific RhB removal of 3050 mg m⁻²). All membrane specimens exhibited good performances while operated in the flow-through photocatalytic membrane reactor. Over 91% of RhB removal capability was retained after 4 treatment cycles. All membranes also showed self-cleaning property by retaining >90% of initial flux after 4 treatment cycles. The flexibility of optimizing membrane performances by fine-tuning the porosity gradient configuration of the photocatalytic layer has also been demonstrated.     

Effect of hypochlorite treatment on performance of hollow fiber membrane prepared from polyethersulfone/N‐methyl‐2‐pyrrolidone/tetronic 1307 solution

Polyethersulfone (PES) hollow fiber membrane was prepared by blending with nonionic surfactant Tetronic 1307 to improve its hydrophilicity. The membranes were posttreated by hypochlorite solution of 10, 100, 500, and 2000 ppm. The effect of hypochlorite treatment on the performance of PES membrane was investigated. Experimental results showed that the water permeability of treated membrane was two to three times higher than that of untreated membrane in case of blend membrane prepared from PES/N‐methyl‐2‐pyrrolidone (NMP)/Tetronic 1307 solution. On the other hand, hypochlorite treatment has no effect on water permeability of the membrane prepared from PES/NMP solution. Elemental analysis and ATR–FTIR measurement results indicated that hypochlorite treatment led to decomposition and leaching out of Tetronic 1307 component from the membrane. The change of membrane surface structure by the hypochlorite treatment was confirmed by atomic force microscopy measurement. The hypochlorite treatment brought about no significant impact on the mechanical property of the membranes. This indicated that the hypochlorite treatment of PES membrane prepared with surfactant was a useful way to improve the water permeability without the decrease of membrane strength. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

用于喷墨印花染料纯化的自组装GO/TiO2复合纳滤膜的制备

数码喷墨打印技术对墨水高纯度和低含盐量要求,不断促使染料纯化技术的开发与研究。基于氧化石墨烯(GO)/纳米二氧化钛(TiO₂)自组装的纳滤膜材料的开发,探究了纳米TiO₂颗粒尺寸和与GO共混比例,所获最优GO/TiO₂复合纳滤膜中TiO₂颗粒尺寸为60 nm,与GO共混比例为1∶1。其纯水通量为10.69 L/(m²·h·bar),对NaCl和Na₂SO₄的截留分别为12.6%和15.7%,对铬黑T、刚果红和考马斯亮蓝R的截留均高于99%。采用自制的连续恒容渗滤装置对粗品墨水进行染料脱盐浓缩的实验,所获染料的浓度由最初的2.0 g/L浓缩至9.74 g/L,NaCl和Na₂SO₄浓度则由起始10 g/L分别下降至5.3 mg/L和11 mg/L,满足数码印花对墨水高纯度以及低盐度的要求。     

CO2/CH4高分子气体分离膜材料研究进展

气体膜分离法正在成为分离CO2/CH4体系的一项重要技术。概括介绍了该领域国内外的主要高分子膜材料的研究进展,重点介绍了聚酰亚胺膜和促进传递膜材料,并提出了膜材料的改进方向,以期为制得更好的膜提供帮助。     

Synthesis of dual-functionalized mixed matrix membrane with amino-GO-Bent/PVDF for efficient separation of CO2/CH4 and CO2/N2

Mixed matrix membranes (MMMs), which combine the characteristics of inorganic nanofillers and organic matrices, have received wide attention because of their good permeability and selective performance for separating CO₂ from industrial waste gases. In this work, the amino-GO-loaded bentonite (amino GO-Bent) was prepared by loading  NH₂ on the GO surface with a large number of functional sites. Firstly, by introducing  NH₂ on the surface of GO and then interacting with bentonite (Bent) organically modified by silane coupling agents through amide bonding. Mixed matrix membranes (MMMs) with an area of 623.7 cm² and homogeneous texture were prepared using amino-GO-Bent as inorganic filler to improve the membrane selectivity for CO₂/N₂ and CO₂/CH₄ separation. The results show that the introduction of amino GO-Bent in MMMs can greatly improve the CO₂ permeability and obtain high CO₂ permeation performance: 2.67945 × 10⁻⁷ cm³ (STP)·cm/s/cm²/cmHg, and the selectivity of CO₂/N₂ and CO₂/CH₄ can reach 307.28 and 325.97, respectively. The two selective values were 14 and 18 times higher than those of pure PVDF membranes, and the performance of MMMs far exceeded the Robeson upper limit in 2008, respectively.     

Vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor with Cu/SiO2/ ceramic composite membrane

The Cu/SiO₂/ceramic composite membrane was prepared on the SiO₂/ceramic mesoporous membrane by an ion exchange method, and vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor was investigated. It showed much better performance in the catalytic membrane reactor than that in the fixed-bed reactor under the same reaction conditions. At 240 °C, 57.3% conversion of methanol and 50.0% yield of methyl formate were achieved in the catalytic membrane reactor and only 43.1% conversion of methanol and 36.9% yield of methyl formate were achieved in the fixed-bed reactor.