Ultrafiltration and nanofiltration membranes applied to the removal of the pharmaceuticals amoxicillin,naproxen, metoprolol and phenacetin from water

BACKGROUND: In the removal of pharmaceuticals present in aquatic systems by membrane processes, some important issues must be explored in order to obtain a better knowledge of the global process. Among these issues, a better understanding of the influences of the operating parameters on the membrane flux, an analysis of membrane resistances and fouling, and determination of the removal of specific substances, must be studied. RESULTS: Four selected pharmaceuticals (amoxicillin, naproxen, metoprolol and phenacetin) were subjected to ultrafiltration (UF) and nanofiltration (NF) processes for their removal from several water matrices. The determined permeate fluxes at the steady state were affected by the main operating conditions: molecular weight cut‐off (MWCO) of the membrane, transmembrane pressure TMP, cross‐flow velocity and temperature. The retention coefficients with the UF membranes followed the sequence naproxen > metoprolol > amoxicillin > phenacetin, and with the NF membranes, followed the trend: amoxicillin > naproxen > metoprolol > phenacetin, due to the role of other mechanisms such as size exclusion and electrostatic repulsion. In the case of the selected water matrices, the retention coefficient was referred to some quality parameters (total organic carbon, chemical oxygen demand and absorbance at 254 nm), leading to moderate (UF) or high (NF) removals of the organic matter content. CONCLUSIONS: The NF CK membrane achieved the highest retention of these pharmaceuticals (excepting phenacetin), and provided retentions for quality parameters around 80% in the four water systems tested. Copyright © 2011 Society of Chemical Industry     

微孔膜对O/W型乳液破乳的研究

采用以正丁醇 水为实验体系和十二烷基磺酸钠为表面活性剂制得的乳液为研究对象 ,研究了膜通量随时间的变化规律 ,考察了透过压、乳液中油含量以及膜孔径等因素对破乳效果的影响。结果表明 ,膜破乳技术是一种很有效的破乳技术。乳液通量的稳定在本实验条件下需要 4h以上。增加透过压有利于乳液通量的增加 ,但透过油中油含量会随之增加。在同样操作条件下 ,增加乳液油含量不利于通量增加和透过液中油含量的减少。微孔膜的孔径对膜通量有很大的影响 ,随着孔径增大 ,膜通量迅速增加 ,而透过液的油含量仍可保持较低量     

Effect of Conditioning Ultrafiltration Membranes on their Performances in Electrodialysis with Ultrafiltration Membrane

Abstract

A recent alternative method based on ultrafiltration membrane stacked in an electrodialysis cell was recently used for the separation of bio‐active high added value charged molecules, such as peptides and polyphenols. However, the ultrafiltration membranes which are uncharged membranes present lower electrical conductivity, in comparison with conventional ion‐exchange membranes. The purpose of this study was to evaluate the effect of conditioning ultrafiltration membranes of different molecular weight cut‐off (MWCO) (10, 20, 50, and 100 kDa) in solution with different ionic strength (distilled water and 0.1 M NaCl_(aq)) on their electrodialytic properties. It appeared that the conditioning solution could have a major impact on the electrical conductivity value of an ultrafiltration membrane and that the final conductivity value after soaking increased with an increase in molecular weight cut‐off. However, the soaking period and solution had no effect on membrane thickness. Furthermore, the electrical conductivity of the membrane was increased after an electrodialysis with ultrafiltration membranes process of a salt solution.     

Effect of polyvinylpyrrolidone molecular weights on morphology,oil/water separation,mechanical and thermal properties of polyetherimide/polyvinylpyrrolidone hollow fiber membranes

We prepared polyetherimide (PEI) hollow fiber membranes using polyvinylpyrrolidones (PVP) with different molecular weights (PVP 10,000, PVP 40,000, and PVP 1,300,000) as additives for oil/water separation. Asymmetric hollow fiber membranes were fabricated by wet phase inversion technique from 25 wt % or 30 wt % solids of 20 : 5 : 75 or 20 : 10 : 70 (weight ratio) PEI/PVP/N‐metyl‐2‐pyrrolidone (NMP) solutions and a 95 : 5 NMP/water solution was used as bore fluid to eliminate resistance on the internal surface. Effects of PVP molecular weights on morphology, oil‐surfactant‐water separation characteristics, mechanical, and thermal properties of PEI/PVP hollow fiber membranes were investigated. It was found that an increase in PVP molecular weight and percentage in PEI/PVP dope solution resulted in the membrane morphology change from the finger‐like structure to the spongy structure. Without sodium hypochlorite posttreatment, hollow fiber membranes with higher PVP molecular weights had a higher rejection but with a lower water flux. For oil‐surfactant‐water emulsion systems (1600 ppm surfactant of sodium dodecylbenzenesulfonate and 2500 ppm oil of n‐decane), experimental results illustrated that the rejection rates for surfactant, total organic carbon, and oil were 76.1 ≈ 79.8%, 91.0 ≈ 93.0%, and more than 99%, respectively. Based on the glass transition temperature values, PVP existed in hollow fiber membranes and resulted in the hydrophilicity of membranes. In addition, using NaOCl as a posttreatment agent for membranes showed a significant improvement in membrane permeability for PVP with a molecular weight of 1300 K, whereas the elongation at break of the treated hollow fiber membranes decreased significantly. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2220–2233, 1999     

Effiziente Wasserabtrennung aus Dieselkraftstoff mittels Membrantechnik und Online‐Monitoring

The separation of water from diesel fuel is very important for safety, ecological, and economic reasons, as otherwise it can lead to lower combustion efficiency and engine problems. In addition, the free water from ultra‐low‐sulfur diesel (ULSD) can only be insufficiently separated with the classic separation systems. To solve this problem, a membrane process with different organic/inorganic membranes for the selective separation of water droplets from ULSD and an innovative water‐in‐oil online sensor were developed.     

Vegetable oil degumming with polyimide and polyvinylidenefluoride ultrafiltration membranes

The removal of phospholipids (‘degumming’) is the first step in the process of refining crude vegetable oil. Membrane separation has been often proposed as an alternative to the conventional procedure (water degumming). Until now, the instability of polymeric membranes in organic solvents has been the major obstacle in applying this technique. In this work, a local synthesized polyvinylidenefluoride (PVDF) and a commercial polyimide (PI) membrane were evaluated for their flux and rejection properties during degumming of soybean oil in a laboratory‐scale cross‐flow ultrafiltration cell. Degumming experiments were done at different temperatures and feed flows, keeping constant both the feed concentration and the transmembrane pressure. PVDF and PI membranes gave selectivity values and permeate color that did not differ significantly from each other. Retention coefficients larger than 98% were obtained in all cases. In every experiment, a decline in permeate flux with time occurred at the beginning of the degumming process. By increasing the feed rate, a higher permeate flux was obtained. The results show that the PVDF membrane had a higher productivity than the PI one. Copyright © 2003 Society of Chemical Industry     

Mathematical Modeling of Flux in Ultrafiltration Membrane for Water Treatment

Abstract

Calculation of water flux in a spiral ultrafiltration element was conducted by the novel proposed method, in which all necessary parameters were determined solely from membrane sheet test. By comparing water flux of the commercial element with the data from membrane sheet measurement, this study found that the tendency of water flux variation with time in the membrane element was similar to that which occurred in the membrane sheet, including the consideration of scale‐up effect due to hydrodynamics influence. Therefore, it is possible to express the variation of water flux in the membrane element based on the results from membrane sheet measurement using a practical water source. Surface water and sea water were separately employed to carry out a pilot test with an 8‐inch spiral membrane element, made of polyvinylidene fluoride(PVDF) with a molecular weight cut‐off of 150 kDa, and water fluxes under various transmembrane pressures. Calculations were approximate agreement with that of the pilot test, which enables us believe that the proposal method is reliable for designing a practical ultrafiltration system.     

Factors influencing critical flux in membrane filtration of activated sludge

Membrane filtration of biomass is usually accompanied by significant flux decline due to cake‐layer formation and fouling. Crossflow filtration with flux controlled by pumping the permeate can produce stable fluxes if a ‘critical flux’ is not exceeded. Below critical flux the transmembrane pressure is typically very low and increases linearly with imposed flux. Above the critical flux the transmembrane pressure rises rapidly signifying cake‐layer formation which is usually accompanied by a continued rise in transmembrane pressure and/or a drop in delivered flux. A range of microfiltration and ultrafiltration membranes with pore sizes from 0.22 to 0.65 µm and molecular weight cut‐off of 100 kDa was used. The feed was an activated sludge mixed liquor with concentration in the range of 3–10 g dm⁻³. The results show that the critical flux depends on feed concentration and crossflow velocity, being higher for higher crossflow velocity or lower feed concentration. Critical flux was also dependent on membrane type, being lower for hydrophobic membranes. Although the transmembrane pressure was higher for the larger pore size membrane, no significant difference in critical flux was observed among different pore size membranes. © 1999 Society of Chemical Industry     

Oil–Water Separation Using Superhydrophobic PET Membranes Fabricated Via Simple Dip‐Coating Of PDMS–SiO2 Nanoparticles

The surfaces of commercially available polyester (PET) and polypropylene (PP) are superhydrophobically modified via the deposition of polydimethylsiloxane (PDMS)‐coated SiO₂ nanoparticles (P‐SiO₂) and PDMS binder. The adhesion of P‐SiO₂ is stronger on PET than on PP due to a stronger chemical interaction between PET and PDMS, which is attributed to the higher surface energy of PET than PP. The waterproof ability and oil separation rate of the P‐SiO₂‐coated PET (dip‐PET) membranes are studied as a function of membrane thickness, and the influence of oil viscosity on the oil separation efficiency is investigated. Optimal membrane thickness should be selected in a given environment for the facile oil–water separation and the dip‐PET membrane is chemically stable and can be used repetitively for oil–water separation. Finally, an automated prototype instrument is introduced for the dip‐coating process. It is suggested that our dip‐PET is a promising solution for oil–water separation in real‐world oil‐spill applications.     

Effect of Tween 80 on morphology and performance of poly(L‐lactic acid) ultrafiltration membranes

Poly(L‐lactic acid) (PLLA) ultrafiltration (UF) membrane was fabricated by immersion precipitation method using Tween 80 as an additive. Membrane structure was characterized by scanning electron microscopy (SEM), porosity and pore size measurement, and atomic force microscopy (AFM). Membrane performance was evaluated by pure water flux, molecular weight cut‐off, and tensile test. It was found that the addition of Tween 80 into the casting solution significantly increased the permeability and molecular weight cut‐off of membrane. Tensile test confirmed that the as‐prepared PLLA membranes exhibited acceptable mechanical properties for ultrafiltration. Further, the role of Tween 80 in the process of membrane formation was analyzed and proposed. The addition of Tween 80 favored the formation of larger pores by interrupting the polymer chain entanglement and improving the miscibility between solvent and coagulant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44428.     

Enhancing antifouling performance of poly(l‐lactide) membranes by TiO2 nanoparticles

Poly(l ‐lactide) (PLLA)/TiO₂ composite membranes were fabricated by immersion precipitation method. The resulting membranes were characterized using various methods including XRD, ATR‐FTIR, TGA, DSC, SEM, goniometer, and molecular weight cut‐off. The antifouling performance of the membrane was investigated through the filtration experiments of the oil/water emulsion. XRD, SEM, and ATR‐FTIR results indicated that TiO₂ was successfully introduced into the membrane, while DSC and TGA indicated the enhancement of thermal stability of membrane. The improvement of membrane hydrophilicity was confirmed by goniometer. In addition, the pore size and porosity on the membrane surface varied obviously with increasing the TiO₂ loading. It was concluded that PLLA/TiO₂ composite membranes had better antifouling and recycling performance compared with the pure PLLA membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43542.     

Membrane‐Based Conditioning of an Innovative Oil‐Based Preservative for Food Technology

Demulsification of emulsions is of great interest for industrial applications. For developing a new, alternative preservation process, investigations are conducted for separating a mixture of water and an oil‐based preservative by membrane technology. Using a water‐in‐oil emulsion, the conventional membrane separation with hydrophobic membranes does not show a reasonable result. It was found that the oil‐based preservative leads to a hydrophilization of the membrane by its amphipathic character. Subsequently, a possible separation with a hydrophilic membrane system as a coalescing system was investigated. Different parametric studies were performed. The efficiency of the coalescence depends on the membrane material, the pore size, the transmembrane pressure, and the temperature during membrane passage as well. Best results so far have been achieved by using a polyethersulfone membrane with a pore size of 0.6 μm.     

Biological Treatment of Agro‐Industrial Wastewater for the Production of Glucoamylase and Rhizopus Biomass

Abstract

The present work concerns the biological treatment of a starch wastewater, coupled with the production of microbial biomass and glucoamylase. Every unit operation of the process was tested in a laboratory scale, in order to perform a feasibility analysis. Fermentation tests confirmed that a stirring rate of 300 rpm was the optimum (in the investigated range) as concerns biomass growth and enzyme activity. Ultrafiltration tests showed that the best operating conditions in the investigated range for enzyme recovery were: temperature 25°C, transmembrane pressure 100 kPa, membrane cut off 30 kDa. Diafiltration tests evidenced that an effective enzyme washing (about 85% reduction of chemical oxygen demand) was achieved with 3 volumes of water per volume of feed and no significant enzyme deactivation was observed.     

Influence of adsorption and concentration polarisation on membrane performance during ultrafiltration of a non-ionic surfactant

Surfactants are present in almost all aqueous solutions — either as additives for different purposes, or because they occur naturally. Because of the common occurrence of surfactants in process water it is important to know how they behave in membrane processes. Ultrafiltration membranes allow almost complete passage of surfactant monomers, but reject micelles almost completely. Concentration polarisation during ultrafiltration of surfactant solutions is therefore mainly influenced by the presence of micelles. Operating parameters, e.g. the transmembrane pressure and the concentration of surfactant, as well as the pure water flux of the membrane, have a marked influence on the performance of hydrophilic membranes, as shown in this investigation. A distinct difference between the interaction of a non-ionic surfactant with hydrophilic and hydrophobic membranes was observed. The hydrophobic membrane showed a flux reduction already at concentrations below the critical micelle concentration (CMC), whereas no flux reduction was observed for a hydrophilic membrane with the same nominal molecular weight cut-off, below the CMC.     

疏水性油水分离膜及其过程研究进展

油水分离是治理含油废水和含水油液的重要工业过程。本文概括了疏水性油水分离膜的类型与制备方法,包括常规分离膜和高度疏水/超亲油分离膜。前者为常规微滤、超滤及纳滤过程用膜;后者由构筑高度疏水（水滴接触角≥120°）表面方法得到,形式有金属网膜、纤维膜、滤纸、复合膜及不对称膜,其为制备耐污染的疏水性油水分离膜提供了新思路。指出了疏水性膜用于油水分离的过程原理及应用现状：含油废水除油中,疏水性膜可实现O/W乳液的破乳、粗粒化油滴、滤除油滴及吸附油分子几方面的功能;含水油液除水中,膜被用来截留水滴,可直接得到净化的油品。最后,指出了其过程规模化应用前尚需解决的重要问题,特别是高度疏水/超亲油分离膜的制备、相关过程研究的深入及其规模化试验等方面需着力加强。     

Purification of Produced Water by Ceramic Membranes: Material Screening,Process Design and Economics

Abstract

Produced water, generated from underlying formations during the recovery of hydrocarbons, constitutes the largest waste stream associated with oil and gas production. Currently, over 90% of produced water is reinjected into the formation, either in support of enhanced oil recovery or for disposal. In arid areas, reclamation of produced water for beneficial uses such as irrigation or tower cooling may be an attractive alternative if the produced water can be purified to an adequate quality, specifically through the removal of dissolved components including inorganic compounds (salts, heavy metals, and radiochemicals) and organic compounds (fatty acid, aliphatic, and aromatics).

Membranes technologies show advantages in both energy efficiency and high water quality. Due to the presence of dissolved organics, reverse osmosis with organic membranes is highly limited. Research efforts focus on developing new materials that are less prone to fouling and are easy to regenerate. Novel ceramic membranes are relatively new classes of material that show promising application in produced water purification due to their extreme stability in harsh environments and optional choices for regeneration. This paper details the results of investigations of produced water purification by microporous ceramic membranes, including metal oxide membranes, clay membranes, and zeolite membranes. Techniques for membrane fabrication, process design, and economic aspects are also discussed.     

Al_2O_3的添加对聚砜膜性能的影响

报导了用相转化法 (sol- gel)制备聚砜 - Al2 O3共混膜。该膜是将 Al2 O3微粒填充到聚砜中制成的。对该膜的机械性能 ,对含油污水的超滤性能 ,扫描电镜 (SEM) ,亲水性和孔隙率进行了测试。对分散剂和制膜工艺对共混膜性能的影响作了分析。实验发现该共混膜对含油污水具有很好的处理效果     

膜分离技术在油田含油污水处理中的应用研究进展

介绍了膜分离技术及其优点,有机膜、无机膜和复合膜在油田含油污水处理中的应用研究进展;分析了膜处理含油污水过程中的破乳机理、影响含油污水处理效果的各种因素、产生膜污染的原因及其控制措施;探讨了膜分离技术的研究方向和发展前景.最后指出,深入研究分离膜的分离过程和机理,探索合适的清洗周期,研究合适的清洗剂和清洗工艺,明确分离膜的预处理指标要求,合理安排工艺流程,开发新型膜及膜组件是膜分离技术在油田含油污水处理中应重点解决的问题.     

Elimination of organic matter present in wastewaters from the cork industry by membrane filtration

BACKGROUND: The first stage of the cork industrial process generates great volumes of wastewater with moderate to high organic pollutant content that must be purified using different procedures, such as filtration by membranes. RESULTS: The tangential filtration of these wastewaters was studied using two different laboratory equipments. In the first one, three ultrafiltration (UF) membranes were tested, with molecular weight cut‐off (MWCO) 100 kDa and 30 kDa, and two operating modes were used: total recycling of permeate and retentate streams, and in continuous mode, without recycling both streams. In the total recycling UF experiments, the influence of the operating variables on the permeate flux was first established. The effectiveness of the different membranes was determined by evaluating the rejection coefficients for several parameters that measure the global pollutant content of the effluent. The values found for these rejection coefficients were in the following order: ellagic acid and color > absorbance at 254 nm > tannic content > COD (chemical oxygen demand). In the continuous mode experiments, the fouling mechanism for each membrane was established by fitting the experimental data to various filtration fouling models given in the literature. The operating mode in the second equipment was batch concentration, and additional experiments were carried out with an UF membrane (2 kDa), and with a NF membrane (with MWCO in the range 150–300 Da). CONCLUSIONS: The three operating modes tested provided different rejection levels of organic matter; among them, the most effective procedure tested was batch concentration mode using a NF membrane. Copyright © 2007 Society of Chemical Industry     

Amphiphilic poly(ether sulfone) membranes for oil/water separation: Effect of sequence structure of the modifier

Oil‐contaminated wastewater threatens our environment and health thus novel membrane materials with low or nonfouling properties are an immediate need for oily wastewater treatment in a cost‐effective and environmentally friendly manner. In this study, three types of amphiphilic random, gradient, and block copolymers with similar molecular weights and chemical compositions, based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate (TFOA), were synthesized by the reversible addition‐fragmentation chain transfer (RAFT) method. The amphiphilic Poly(ether sulfone) membranes were then fabricated by blending with these copolymers via a facile coupled process of nonsolvent induced phase separation and surface segregation. Accompanying the phase inversion process of polymer matrix, the hydrophilic and hydrophobic segments in the amphiphilic modifiers would migrate and immobilize onto the membrane surfaces. This surface segregation process leaded to a chemical heterogeneous membrane surface comprising both hydrophilic PEGMA and low surface energy PTFOA brushes, which was confirmed by X‐ray photoelectron spectroscopy (XPS) and surface wettability analyses. Oil‐in‐water emulsion filtration test of the membranes displayed a lower permeate flux decline and a higher flux recovery (as high as 99.8%), establishing their considerably elevated antifouling properties. Additionally, cyclic oil/water separation and long‐term underwater immersion tests demonstrated that the as‐prepared membranes modified by these amphiphilic additives possessed excellent antifouling stabilities. © 2016 American Institute of Chemical Engineers AIChE J, 63: 739–750, 2017