具有PDA-UiO-66中间层耐溶剂复合纳滤膜的制备及性能

将多巴胺和Ui O-66纳米颗粒共沉积在经1,6-己二胺交联的聚醚酰亚胺（PEI）基膜上构建了纳米复合中间层（PDA-UiO-66），并在中间层上进行界面聚合反应制备了耐溶剂复合纳滤膜（TFN-U）。通过FTIR、XRD、SEM、AFM、水接触角测量仪对膜结构进行了表征和测试，探究了Ui O-66质量浓度对TFN-U膜耐溶剂性、耐污染性以及运行稳定性的影响。结果表明，PDA-Ui O-66纳米复合中间层的引入能提高TFN-U膜的渗透通量，当Ui O-66纳米颗粒质量浓度为0.2 g/L时，TFN-U2膜水通量为63.83 L/(m2·h)，甲醇通量为28.50L/(m2·h)，对刚果红水溶液和刚果红甲醇溶液的截留率为98.2%和93.2%，经无水乙醇、丙酮、乙酸乙酯、正己烷及N,N-二甲基甲酰胺（DMF）浸泡48h后，其对刚果红的截留率均>94%，通量恢复率达到78.1%，在连续24 h过滤刚果红甲醇溶液后，该膜的甲醇通量为14.13L/(m2·h)，截留率为98.3%，表明TFN-U2膜具有良好的耐溶剂性、耐污染性以及一定的运行稳定性。     

有机溶剂纳滤膜的润湿性对渗透和分离性能的影响

有机溶剂纳滤是一种绿色、高效、节能的新型膜分离技术,在回收和处理有机溶剂中具有广泛的应用前景。本文采用浸渍法分别将聚合物聚二甲基硅氧烷（PDMS）、嵌段聚醚酰胺（PEBAX2533）和聚乙烯醇（PVA）与聚砜（PS）超滤基膜复合,制备了3种不同润湿性的聚合物耐溶剂纳滤膜,研究了PDMS/PS、PEBAX/PS和PVA/PS复合膜对甲醇、乙醇、异丙醇、正己烷、正庚烷的渗透性能,考察了3种聚合物膜对伊文思蓝/甲醇溶液的有机溶剂纳滤性能。结果表明,有机溶剂在不同润湿性复合膜的渗透和传递性能与溶剂本身的溶度参数、分子量、黏度和极性等有很密切的相关性,溶剂的分子量、黏度、分子动力学直径越小,在同一极性复合膜中渗透通量越大;对伊文思蓝/甲醇溶液的有机溶剂纳滤分离表明,PDMS/PS和PEBAX/PS复合膜的截留率均可达90%以上,通量分别为 58.0L/(m²·h·MPa)和72.2L/(m²·h·MPa);PVA/PS复合膜的截留率为85.1%左右,通量为57.5L/(m²·h·MPa)。     

Membrane Concentration and Separation of L-Aspartic Acid and L-Phenylalanine Derivatives in Organic Solvents

Abstract

The concentration and separation of the amino acids N-benzyloxycarbonyl L-aspartic acid and L-phenylalanine methyl ester hydrochloride in organic solvents have been investigated using reverse osmosis membranes of two types of cellulose acetate, a nanofiltration membrane of polyamide-polyphenylene sulfone (PA-PPSO) composite and a gas separation membrane of polyimide composite in a stirred batch cell. The organic solvents used included primary, secondary, and tertiary alcohols, an ester, and a ketone. There were significant variations in permeate flux, solute rejection, and membrane stability. Usually the rejection of both amino acids was similar; however, certain membrane-solvent combinations gave significantly different levels of rejection. The highest rejection of amino acids (～0.94) at the lowest pressure of 0.5 MPa was obtained with the PA-PPSO membrane using methanol as a solvent. The cellulose acetate membranes gave reasonable rejection and fluxes but the membrane stability was very poor. The performance of the polyimide composite membrane was good with ethanol but poor with other solvents. The PA-PPSO membrane with methanol as solvent appeared the most promising combination, and the separation performance according to concentration polarization was discussed.

     

Preparation of thin film nanocomposite membranes with surface modified MOF for high flux organic solvent nanofiltration

Preparation of defect‐free and optimized thin film nanocomposite (TFN) membranes is an effective way to enhance the process of organic solvent nanofiltration. However, it still remains a great challenge due to poor filler particle dispersibility in organic phase and compatible issue between fillers and polymers. Aiming at these difficulties, UiO‐66‐NH₂ nanoparticles were surface modified with long alkyl chains and used in the preparation of TFN membranes. As a result, defect‐free TFN membranes with ultrathin MOF@polyamide layer were successfully prepared benefited from the improved particle dispersibility in n‐hexane. Significant enhancement was found in methanol permeance after nanoparticle incorporation, without comprising the tetracycline rejection evidently. Especially, the novel TFN membrane prepared with organic phase solution containing 0.15% (w/v) modified UiO‐66‐NH₂ nanoparticles showed a superior methanol permeance of 20 L·m^?2·h^?1·bar^?1 and a tetracycline rejection of about 99%, which is appealing to the application in pharmaceutical industry for example. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1303–1312, 2017     

Flow synthesis of a novel zirconium-based UiO-66 nanofiltration membrane and its performance in the removal of p-nitrophenol from water

In this work, a thin zirconium-based UiO-66 membrane was successfully prepared on an alumina hollow fiber tube by flow synthesis, and was used in an attempt to remove p-nitrophenol from water through a nanofiltration process. Two main factors, including flow rate and synthesis time, were investigated to optimize the conditions for membrane growth. Under optimal synthesis conditions, a thin UiO-66 membrane of approximately 2 µm in thickness was fabricated at a flow rate of 4 mL·h⁻¹ for 30 h. The p-nitrophenol rejection rate for the as-prepared UiO-66 membrane applied in the removal of p-nitrophenol from water was only 78.1% due to the existence of membrane defects caused by coordinative defects during membrane formation. Post-synthetic modification of the UiO-66 membrane was carried out using organic linkers with the same flow approach to further improve the nanofiltration performance. The result showed that the p-nitrophenol rejection for the post-modified membrane was greatly improved and reached over 95%. Moreover, the post-modified UiO-66 membrane exhibited remarkable long-term operational stability, which is vital for practical application.     

Using a simple method to prepare UiO-66-NH2/chitosan composite membranes for oil–water separation

Chitosan (CS) was used as a cross-linking agent to modify UiO-66-NH₂, and the modified UiO-66-NH₂ was fixed on the mixed cellulose membrane (MCE) through vacuum filtration technology to prepare a new type of membrane. The membrane exhibited excellent hydrophilicity in the air and excellent super-oleophobic performance underwater, and effectively separated various oil–water emulsions. When separating petroleum ether-water emulsion, the filtration flux of the modified membrane was 2000 L m⁻² h⁻¹ higher than that of MCE, and the separation efficiency can reach more than 95%. After 10 cycles, the flux of the modified membrane was about four times of that MCE, which was 500 L m⁻² h⁻¹. Most importantly, the membrane still maintained underwater superoleophobicity in the environment of strong acid, strong base, and salt solution.     

Performance of Nanofiltration Membranes for Solvent Purification in the Oil Industry

The extraction stage of edible oil in the oil industry is commonly performed by using toxic solvents (e.g. hexane) and processes with high energy consumption (e.g. distillation, evaporation) to recover the solvent, which represents around 70–75 wt% in the oil–solvent mixture. In this paper, a membrane-based extraction method using nanofiltration (NF) membranes is presented. Commercial nanofiltration membranes made of different polymers (Desal-DK-polyamide NF from GE-osmonics^®, NF30 polyethersulfone NF from Nadir^®, STARMEM^TM122 polyimide from MET^® and SOLSEP NF030306 silicone base polymer SOLESP^®) were selected and tested to recover the solvent from soybean oil/solvent (10–20–30% w/w oil) mixtures at various separation pressures and constant temperature in a dead-end filtration set up. The selection of the solvent was made in order to compare solvents obtainable from renewable resources, such as ethanol, iso-propanol and acetone, with solvents traditionally used in the industry (i.e. cyclohexane and n-hexane). The structural stability of the membranes towards the different solvents used in this work was verified visually, by the variation of the membrane area and by means of permeate flux assessments. Desal-DK and NF30 showed poor filtration performance and even visible defects after exposure to acetone but a good performance was obtained for the nanofiltration membranes STARMEM^TM122 and SOLSEP NF030306 with ethanol, iso-propanol and acetone. For example, considering a mixture with 30% edible oil in acetone, STARMEM^TM122 shows a flux and oil rejection of 16.8 L m^?2 h and 70%, respectively. For the same conditions, SOLSEP NF030306 exhibited a flux of 4.8 L m^?2 h with 78% rejection, which shows the potential application of nanofiltration membranes in the oil industry.     

Enhancement of flux and solvent stability of Matrimid® thin‐film composite membranes for organic solvent nanofiltration

The development of high flux and solvent‐stable thin‐film composite (TFC) organic solvent nanofiltration (OSN) membranes was reported. A novel cross‐linked polyimide substrate, consisting of a thin skin layer with minimum solvent transport resistance and a sponge‐like sublayer structure that could withstand membrane compaction under high‐pressure was first fabricated. Then the solvent flux was significantly enhanced without compromising the solute rejection by the coupling effects of (1) the addition of triethylamine/camphorsulfonic acid into the monomer solution, and (2) the combined post‐treatments of glycerol/sodium dodecyl sulphate immersion and dimethyl sulfoxide (DMSO) filtration. Finally, the long‐term stability of the TFC membrane in aprotic solvents such as DMSO was improved by post‐crosslink thermal annealing. The novel TFC OSN membrane developed was found to have superior rejection to tetracycline (MW: 444 g/mol) but was very permeable to alcohols such as methanol (5.12 lm^?2h^?1bar^?1) and aprotic solvents such as dimethylformamide (3.92 lm^?2h^?1bar^?1) and DMSO (3.34 lm^?2h^?1bar^?1). © 2014 American Institute of Chemical Engineers AIChE J, 60: 3623–3633, 2014     

Adsorption Behavior of Rhodamine B on UiO-66

The adsorption characteristics of UiO-66 (a Zr-containing metal–organic framework formed by terephthalate) for Rhodamine B (RhB), such as isotherms, kinetics and thermodynamics, were investigated systematically. The batch adsorption data conform well to the Langmuir and Freundlich isotherms. The adsorption kinetics of UiO-66 for RhB can be well described by the pseudo first-order model, and the adsorption thermodynamic parameters ΔG₀, ΔH₀ and ΔS₀ at 273 K are − 6.282 kJ·mol^− 1, 15.096 kJ·mol^− 1 and 78.052 J·mol^− 1·K^− 1, respectively. The thermodynamic analyses show that the adsorption process of RhB on UiO-66 is more favorable at higher temperatures. UiO-66 can be regenerated by desorbing in DMF solution with ultrasonic for 1 h. UiO-66 can keep good performance for at least six cycles of sorption/desorption.     

Comparison Between Polydimethylsiloxane and Polyimide-Based Solvent-Resistant Nanofiltration Membranes

Nanofiltration using solvent-resistant membranes has become an important separation technology. Polydimethylsiloxane and polyimide are important materials for preparation of solvent-resistant nanofiltration (SRNF) membranes. In this study, the performance of commercial polydimethylsiloxane and polyimide SRNF membranes (as a trademark of MPF and STARMEM) with molecular weight cutoff values of 200–700 Da was compared in terms of organic solvent preconditioning effect, solvent compatibility, solvent flux, and solute rejection. Organic solvents employed were methanol, toluene, ethyl acetate, dichloromethane, and acetone and the organic solutes in a molecular weight range of 160–850 Da were used. Membrane preconditioning with different organic solvents did not affect membrane performance of the polydimethylsiloxane-based MPF membranes but had a significant influence on the polyimide-based STARMEM membranes. Both MPF and STARMEM membranes are not compatible in dichloromethane. MPF membranes were inert to the organic solvents and had relatively low solvent fluxes. STARMEM membranes were highly swollen in methanol and offered much higher solvent fluxes and attractive NF performance in toluene.     

Preparation and properties of polyimide solvent‐resistant nanofiltration membrane obtained by a two‐step method

This study investigated the preparation of polyimide solvent‐resistant nanofiltration membranes by a two‐step method (casting the membrane first and then crosslinking by the thermal imidization method). The influences of polymer concentration, thickness of membranes, temperature of the imidization, phase inversion time and thermal imidization procedure were studied. The membranes with the highest rejection rate of Fast Green FCF (molecular weight 808.86 g mol^?1) were prepared in the following conditions: polymer concentration 13 wt%, phase inversion time 1 h, membrane thickness 150 µm and thermal imidization procedure 200 °C for 2.5 h, 250 °C for 2 h and 300 °C for 2 h in a vacuum environment; the heating rate was 5 °C min^?1. The membrane was stable in most of the solvents tested and the fluxes of some common solvents were equal to or higher than a number of commercial solvent‐resistant nanofiltration membranes. A much higher rejection of dyes in water than in methanol was observed in the filtration experiments and a new way to explain it was developed. Copyright © 2011 Society of Chemical Industry     

Zirconia ultrafiltration membranes on silicon carbide substrate: microstructure and water flux

This study reported the preparation of ZrO₂/SiC ceramic membrane with silicon carbide as the substrate and intermediate layers and zirconia as the selective layer. The substrate and intermediate layers were sintered by evaporation-condensation process at 2200 and 1900 ℃, respectively. After sintering, the intermediate layer presented layer thickness of 50 μm, pore size of 0.87 μm and pure water permeability of 2140 L/(m²·h). The selective lay was deposited on the silicon carbide substrate by dip-coating method and then sintered in the temperature range from 800 to 1000 ℃. For the membrane coated by one dip-coating cycle and sintered at 800 ℃, it presented average pores of 82 nm and water flux of 850 L/(m²·h). Due to the exclusion of low-melting oxides during sintering, the ZrO₂/SiC ceramic membrane can satisfy the separation and purification of chemical corrosion and high temperature wastewater.     

Polyamide composite membranes for enhanced organic solvent nanofiltration performance by metal ions assisted interfacial polymerization method

Herein, thin-film composite membranes consisting of poly(m-phenyleneisophthalamide) substrate and polyamide active layer were constructed by transition metal ion-assisted interfacial polymerization method. As compared to the traditional polyamide membranes, a much thinner polyamide layer (33 vs. 200 nm) can be synthesized with higher permeance (3.2 vs. 0.62 L m⁻² h⁻¹ bar⁻¹) in the organic solvent nanofiltration. Similarly, the prepared membranes maintained a high rejection (>99%) for various dyes. Optimal membranes prepared by using Co²⁺ exhibited strong tolerance to various organic solvents with good long-term stability. Positron annihilation spectroscopy and other characterization methods were used to investigate the relationships between the membrane microstructures and the enhanced separation performance. Based on molecular dynamics simulation, it was found that the diffusion coefficient of polyethyleneimine monomer decreased by about 18 times after adding Co²⁺ to the aqueous solution (forming coordination interaction). This procedure has great potential and sustainability for practical organic solvent nanofiltration applications.     

头孢唑林酸废水的纳滤分离及技术经济分析

抗生素类制药废水污染物浓度高,微生物不易降解,处理难度大。采用纳滤膜分离方法处理头孢唑林酸废水,通过现场实验,确定了工艺参数:料液温度25～30℃,pH值4～5,膜平均通量3L/(m2·h),膜前流速7.14L/(m2·min),膜前压力3.0MPa。并得到头孢唑林酸回收率为90.3%～93.7%。通过经济分析,得出不到2年时间即可回收全部投资,因此认为纳滤膜分离技术在处理头孢唑林酸废水中的应用不仅技术上合理,在经济上也是可行的。     

Solvent-resistant polymeric microfiltration membranes based on oxidized electrospun poly(arylene sulfide sulfone) nanofibers

Polymeric membranes have been widely used in the separation of aqueous system, but there were few studies on the organic solvent-resistant microfiltration (MF) membranes. In this study, organic solvent-resistant oxidized poly(arylene sulfide sulfone)-6 (O-PASS-6) nanofibrous MF membrane with high water flux was prepared through electrospun technology, cold-press, and oxidation treatment. The O-PASS-6 nanofibrous MF membrane was made from the interwoven electrospun uniformly 295 nm nanofibers, and the mean pore size was 0.44 μm. The morphology, chemical structure, and aggregation structure of O-PASS-6 nanofibrous MF membrane were characterized systematically by the scanning electron microscope, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Investigations on the weight loss, swelling ratio, and microstructure change all revealed that the O-PASS-6 membrane had superior stability in strong polar solvents, such as 1,3-dimethyl-2-imidazolidinone (DMI), dimethylformamide (DMF), and tetrahydrofuran (THF). MF performance results showed that the pure water flux of O-PASS-6 nanofibrous membrane was up to 753.34 L·m⁻²·h⁻¹, and the rejection ratio was 99.9% to 0.2 μm particles. More importantly, after treated by aggressive solvents, the membranes still possessed good MF performance: the water flux was 770.08, 775.66, and 766.36 L·m⁻²·h⁻¹ when soaked in DMI, DMF, and THF for 7 days, respectively, and high rejection ratio also maintained (>99%) for both particles investigated. The O-PASS-6 membrane with good solvent resistance proved to be a promising candidate as a prefiltration membrane to eliminate submicron particles in both sewage and aggressive solvents. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48506.     

Review of pervaporation and vapor permeation process factors affecting the removal of water from industrial solvents

A recent review article (Journal of Chemical Technology & Biotechnology 94 : 343–365 (2019)) identified several commercially-available permselective materials for drying organic solvents with pervaporation (PV) and vapor permeation (V·P) separation processes. The membrane materials included polymeric and inorganic substances exhibiting a range in the performance characteristics: water permeance, water/solvent selectivity, and maximum use temperature. This article provides an overview of the factors affecting the design of PV/V·P processes utilizing these membranes to remove water from common organic solvents. Properties of the specific membrane and of the solvent substantially affect the PV/V·P separation. Equally important is the impact of operating parameters on the overall separation. To study these impacts, simplified process performance equations and detailed spreadsheet calculations were developed for single-pass and recirculating batch PV systems and for single-pass V·P systems. Estimates of membrane area, permeate concentration, solvent recovery, permeate condenser temperatures, and heating requirements were calculated. Process variables included: solvent type, water permeance, water/solvent selectivity, initial and final water concentrations, operating temperature (PV) or feed pressure (V·P), temperature drop due to evaporation (PV) or feed-side pressure drop (V·P), and permeate pressure. The target solvents considered were: acetonitrile, 1-butanol, N,N-dimethyl formamide, ethanol, methanol, methyl isobutyl ketone, methyl tert-butyl ether, tetrahydrofuran, acetone, and 2-propanol. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.     

Enhancement in Li+/Mg2+ separation from salt lake brine with PDA–PEI composite nanofiltration membrane

Extraction of lithium from high Mg²⁺/Li⁺ ratio salt lake brine with the nanofiltration (NF) membrane is significantly challenging. Interfacial polymerization was utilized for the facile modification of NF membranes with polydopamine (PDA) and polyethylenimine (PEI) to enhance lithium separation efficiency. Comparing permeability and salts rejection (Li⁺ and Mg²⁺) of three NF membranes before and after PDA/PEI deposition, it was observed that separation efficiency was not only dependent on steric hindrance but also affected by Donnan exclusion mechanism. In the case of NF270 membrane after facile polymerization, due to small pore size distribution and low charge density confirmed by zeta potential measurements, Li⁺ permeability was reached about 95% at a flux of 21.33 L·m⁻²·h⁻¹. Although with the DK membrane, separation factor SF_Li/Mg was also increased up to 60 after modification, the pore narrowing effect significantly decreased lithium permeability and flux. Experimental results showed that facile modification not only enhanced stability and hydrophilicity but also reduced the high Mg²⁺/Li⁺ ratio from 30 to 4.1 in single-stage separation.     

UiO-66/PES混合基质超滤膜的制备及性能

以聚醚砜(PES)为主要膜材料、溶剂热法合成UiO-66并掺入铸膜液中,通过非溶剂相转化法(NIPS)制备了混合基质超滤膜.利用X射线衍射仪(XRD)、傅里叶红外光谱(FTIR)、扫描电镜(SEM)、接触角测量仪及原子力显微镜(AFM)对制备的UiO-66和混合基质膜进行表征.重点考察了UiO-66添加量对膜表面形貌、...     

Metal-organic framework UiO-66 membranes

Metal-organic frameworks (MOFs) have emerged as a class of promising membrane materials. UiO-66 is a prototypical and stable MOF material with a number of analogues. In this article, we review five approaches for fabricating UiO-66 polycrystalline membranes including in situ synthesis, secondary synthesis, biphase synthesis, gas-phase deposition and electrochemical deposition, as well as their applications in gas separation, pervaporation, nanofiltration and ion separation. On this basis, we propose possible methods for scalable synthesis of UiO-66 membranes and their potential separation applications in the future.     

Fibrous ceramic membrane constructed by mullite whiskers for the treatment of oil-in-water emulsions

Ceramic membranes with high porosity and excellent separation efficiency are necessary for the efficient treatment of large-scale wastewaters. However, the conventional ceramic membranes are usually prepared by particles-packing, which inhibits the advances of separation efficiency because of the low porosity and connectivity. Here, a fibrous ceramic membrane with mullite whiskers-interlocked structure was prepared by gas-solid reaction. The effects of aluminum fluoride (AlF₃) on the formation and growth of mullite whiskers, and then the permeability and selectivity of the ceramic membranes were investigated. With the increase of AlF₃ contents, the mullite phase evolved from needle-like, rod-like to flake-like structure, thus the catalyst accelerated the growth of mullite whiskers in the diameter direction. For the ceramic membrane sintered at 1400°C, the porosity increased from 58% to 76% while the average pore sizes increased from 0.65 to 3.93 μm because of the whisker-constructed structures. For the ceramic membrane sintered at 1450°C, the emulsion flux increased stably from 295 L/(m²·h) to 992 L/(m²·h) with the increase of trans-membrane pressure, and the oil rejection exceeded 98%. Thus, this study provides a feasible strategy for the preparation of ceramic membranes with high porosity and excellent separation performances.