scholarly journals Oil Deposition on Polymer Brush-Coated NF Membranes

Membranes ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 168 ◽  
Author(s):  
Anh Vu ◽  
Naama Segev Mark ◽  
Guy Z. Ramon ◽  
Xianghong Qian ◽  
Arijit Sengupta ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Polymer Brush ◽  
Operating Mode ◽  
Feed Solution ◽  
Polymer Chains ◽  
Membrane Properties ◽  
Solution Temperature ◽  
Oil Droplets ◽  
Grafted Polymer

Membrane-based processes are attractive for treating oily wastewaters. However, membrane fouling due to the deposition of oil droplets on the membrane surface compromises performance. Here, real-time observation of the deposition of oil droplets by direct confocal microscopy was conducted. Experiments were conducted in dead-end and crossflow modes. Base NF 270 nanofiltration membranes as well as membranes modified by grafting poly(N-isopropylacrylamide) chains from the membrane surface using atom transfer radical polymerization were investigated. By using feed streams containing low and high NaCl concentrations, the grafted polymer chains could be induced to switch conformation from a hydrated to a dehydrated state, as the lower critical solution temperature for the grafted polymer chains moved above and below the room temperature, respectively. For the modified membrane, it was shown that switching conformation of the grafted polymer chains led to the partial release of adsorbed oil. The results also indicate that, unlike particles such as polystyrene beads, adsorption of oil droplets can lead to coalescence of the adsorbed oil droplets on the membrane surface. The results provide further evidence of the importance of membrane properties, feed solution characteristics, and operating mode and conditions on membrane fouling.

scholarly journals Effect of heat treatment on fouling resistance and the rejection of small and neutral solutes by reverse osmosis membranes

2014 ◽  
Vol 15 (3) ◽  
pp. 510-516 ◽  
Author(s):  
Takahiro Fujioka ◽  
Nagayasu Oshima ◽  
Ryoichi Suzuki ◽  
Michael Higgins ◽  
William E. Price ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Reverse Osmosis ◽  
Free Volume ◽  
Membrane Fouling ◽  
Volume Fraction ◽  
Membrane Surface ◽  
Feed Solution ◽  
Membrane Properties ◽  
Permeate Flux ◽  
Fouling Resistance

The effects of heat treatment on membrane fouling resistance and the rejection of small and neutral solutes by reverse osmosis (RO) membranes were elucidated. RO membrane modification by heat treatment reduced fouling and improved boron rejection. However, heat treatment also caused a decrease in the water permeability of RO membranes. Significant improvement on fouling resistance by heat treatment was observed when RO concentrate was used to simulate a feed solution with high fouling propensity. The improved fouling resistance is likely to be due to changes in the hydrophobic interaction between the membrane surface and foulants. Boron rejection by the ESPA2 membrane was enhanced by heat treatment from 26 to 68% (when evaluated at the permeate flux of 20 L/m2 h). Positron annihilation lifetime spectroscopy revealed that heat treatment did not significantly influence the free-volume hole-radius of the membrane active skin layer. The results reported in this study suggested that changes in the other membrane properties such as free-volume fraction and thickness may be the main cause improving boron rejection.

Essential Factors to Make Excellent Biocompatibility of Phospholipid Polymer Materials

2010 ◽  
Vol 76 ◽  
pp. 1-9 ◽  
Author(s):  
Kazuhiko Ishihara ◽  
Yuuki Inoue
Keyword(s):  
Radical Polymerization ◽  
Blood Compatibility ◽  
Membrane Surface ◽  
Polymer Brush ◽  
Living Radical Polymerization ◽  
Polymer Chains ◽  
Polymer Materials ◽  
Biomaterial Surface ◽  
Phospholipid Polymer ◽  
Living Organisms

Recently, much attention has been attracted to bio/blood compatible materials to suppress undesirable biological reactions that determine the fate of living organisms and materials. A phospholipid polymer composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) unit, which is designed by inspiration of cell membrane surface structure, is the most promising polymer biomaterial with excellent bio/blood compatibility. Progress in living radical polymerization method initiated from the surface enables preparation of a dense polymer chains on the surface, which is called as a polymer brush. The polymer brush structure has narrow molecular weight distribution and controlled chain length. So, it is ideal surface to clarify the interactions between the biomolecules and biomaterial surface that has never done. In these regards, the poly(MPC) brush surfaces are expected to be a novel class of biomaterials, and have been extensively studied its unusual properties. In this review, surface-initiated living radical polymerization of MPC and the characteristics of the poly(MPC) brush surfaces are summarized from a viewpoint of biomaterials science.

scholarly journals Effect of Initial Water Flux on the Performance of Anaerobic Membrane Bioreactor: Constant Flux Mode versus Varying Flux Mode

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 203
Author(s):  
Xiawen Yi ◽  
Meng Zhang ◽  
Weilong Song ◽  
Xinhua Wang
Keyword(s):  
Membrane Fouling ◽  
Membrane Surface ◽  
Water Flux ◽  
Operating Time ◽  
Operating Mode ◽  
Initial Water ◽  
Constant Flux ◽  
Membrane Performance ◽  
Fouling Mitigation ◽  
Flux Mode

Anaerobic membrane bioreactors (AnMBRs) have aroused growing interest in wastewater treatment and energy recovery. However, serious membrane fouling remains a critical hindrance to AnMBRs. Here, a novel membrane fouling mitigation via optimizing initial water flux is proposed, and its feasibility was evaluated by comparing the membrane performance in AnMBRs between constant flux and varying flux modes. Results indicated that, compared with the constant flux mode, varying flux mode significantly prolonged the membrane operating time by mitigating membrane fouling. Through the analyses of fouled membranes under two operating modes, the mechanism of membrane fouling mitigation was revealed as follows: A low water flux was applied in stage 1 which slowed down the interaction between foulants and membrane surface, especially reduced the deposition of proteins on the membrane surface and formed a thin and loose fouling layer. Correspondingly, the interaction between foulants was weakened in the following stage 2 with a high water flux and, subsequently, the foulants absorbed on the membrane surface was further reduced. In addition, flux operating mode had no impact on the contaminant removal in an AnMBR. This study provides a new way of improving membrane performance in AnMBRs via a varying flux operating mode.

Approaches to membrane fouling control in anaerobic membrane bioreactors

2000 ◽  
Vol 41 (10-11) ◽  
pp. 363-371 ◽  
Author(s):  
K-H. Choo ◽  
I-J. Kang ◽  
S-H. Yoon ◽  
H. Park ◽  
J-H. Kim ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Ceramic Membrane ◽  
Substantial Improvement ◽  
Membrane Bioreactors ◽  
Polymer Chains ◽  
Polymeric Membrane ◽  
Hydrophilic Modification ◽  
Grafted Polymer ◽  
Fouling Control ◽  
Anaerobic Membrane Bioreactors

Various fouling control methods were investigated for polymeric and ceramic microfiltration membranes in the anaerobic membrane bioreactors where inorganic precipitates and/or fine colloids have been recently known as the most significant foulants: (i) Substantial improvement of flux was achieved by backfeeding of acidic wastewater through the membrane module. The backfeeding mode formed an acidic environment around the membrane pores and thus suppressed struvite formation. (ii) Struvite precipitation was also mitigated when an additional combined dialysis/zeolite unit was attached to the bioreactor. With this combined unit the flux improvement for the ceramic membrane, where struvite had a severer fouling effect, was achieved more significantly than that for the polymeric membrane. (iii) To control the deposition of organics and fine colloids onto the polymeric membrane, powdered activated carbon (PAC) was added into the bioreactor, which gave rise to the reduction of specific cake resistances of biosolids through the sorption and/or coagulation of dissolved and colloidal matter. (iv) The hydrophilic modification of polypropylene (PP) membranes by graft polymerization reduced membrane fouling. Its effectiveness was most substantial at 70% of the degree of grafting, indicating that there was an optimal degree of grafting. This is possibly due to the steric hindrance of grafted polymer chains and the increase in the hydrophilicity of the grafted PP membrane.

scholarly journals Membrane Fouling – The Enemy of Forward Osmosis

2021 ◽  
Vol 25 (2) ◽  
pp. 73-88
Author(s):  
Z. H. Chang ◽  
Y. H. Teow ◽  
S. P. Yeap ◽  
J. Y. Sum
Keyword(s):  
Membrane Fouling ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Forward Osmosis ◽  
Feed Solution ◽  
Separation Process ◽  
Nutrient Recovery ◽  
Water Reclamation ◽  
Water Permeation ◽  
Fouling Mechanism

Forward osmosis (FO) is an osmotically driven membrane separation process. It is potentially applied in various industries for nutrient recovery and water reclamation. Although FO showed a lesser fouling tendency than other pressure-driven membrane processes, the solutes in the feed solution would still deposit on the membrane surface, forming a fouling layer that resists water permeation. For that reason, fouling mitigation is a trending issue in the FO process. A better understanding of the fouling mechanism is required before opting for the appropriate strategy to mitigate it. This article describes the fouling mechanism based on different foulant presented in the feed, followed by a method in relieving fouling in the FO process.

scholarly journals Intermittent Ultrasound-Assisted Ceramic Membrane Fouling Control in Ultrafiltration

2021 ◽  
Author(s):  
Kyu Min Lee ◽  
Farhad Ein-Mozaffari
Keyword(s):  
Flow Rate ◽  
Membrane Fouling ◽  
Ceramic Membrane ◽  
Membrane Surface ◽  
Operating Cost ◽  
Feed Solution ◽  
Time Interval ◽  
Short Time Interval ◽  
Feed Concentration ◽  
Power Intensity

Ultrafiltration is one of the most promising membrane technologies for liquid purification due to its high economic efficiency in the industries. However, it has been faced with a critical problem, called fouling. The contaminants in feed solution tend to accumulate on the membrane surface, hindering permeate solution to pass through the porous spaces. Among the various solutions, application of ultrasound has been considered as the most popular method since it does not suffer a disadvantage of downtime and the filtration process does not need to be stopped for the removal of foulants. In this study, control of ceramic membrane fouling by an on-line intermittent ultrasound system was being investigated. The experiment focused on obtaining optimal operating ultrasonic condition. Frequency (20, 28, and 40 kHz), power intensity (1.44, 2.88, and 5.76W/cm2 ), and time interval of intermittent ultrasound (1, 1.5, and 2 minutes) were the parameters of interest. The effect of feed concentration was also analyzed at optimal ultrasonic condition. The quality and flow rate of the permeate streams were monitored for the evaluation of the process performance. The optimal condition of intermittent ultrasound was found at the frequency of 28 kHz and the power intensity of 2.88 W/cm2 ; and then, the application of intermittent ultrasound with short time interval successfully reduced the operating cost of ultrafiltration process while maintaining acceptable quality and flow rate of permeate solution. There was increase in efficiency of intermittent ultrasound at lower feed concentration.

scholarly journals Densely Packed Tethered Polymer Nanoislands: A Simulation Study

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2570
Author(s):  
Nicolas Chen ◽  
Oleg Davydovich ◽  
Caitlyn McConnell ◽  
Alexander Sidorenko ◽  
Preston B. Moore
Keyword(s):  
Rational Design ◽  
Polymer Brush ◽  
Structural Features ◽  
Polymer Chains ◽  
Semiflexible Polymers ◽  
Grafted Polymer ◽  
Neighbor Effect ◽  
Critical Components ◽  
Different Characteristics ◽  
External Stimuli

COordinated Responsive Arrays of Surface-Linked polymer islands (CORALS) allow for the creation of molecular surfaces with novel and switchable properties. Critical components of CORALs are the uniformly distributed islands of densely grafted polymer chains (nanoislands) separated by regions of bare surface. The grafting footprint and separation distances of nanoislands are comparable to that of the constituent polymer chains themselves. Herein, we characterize the structural features of the nanoislands and semiflexible polymers within to better understand this critical constituent of CORALs. We observe different characteristics of grafted semiflexible polymers depending on the polymer island’s size and distance from the center of the island. Specifically, the characteristics of the chains at the island periphery are similar to isolated tethered polymer chains (full flexible chains), while chains in the center of the island experience the neighbor effect such as chains in the classic polymer brush. Chains close to the edge of the islands exhibit unique structural features between these two regimes. These results can be used in the rational design of CORALs with specific interfacial characteristics and predictable responses to external stimuli. It is hoped that this the discussion of the different morphologies of the polymers as a function of distance from the edge of the polymer will find applications in a wide variety of systems.

scholarly journals Intermittent Ultrasound-Assisted Ceramic Membrane Fouling Control in Ultrafiltration

2021 ◽  
Author(s):  
Kyu Min Lee ◽  
Farhad Ein-Mozaffari
Keyword(s):  
Flow Rate ◽  
Membrane Fouling ◽  
Ceramic Membrane ◽  
Membrane Surface ◽  
Operating Cost ◽  
Feed Solution ◽  
Time Interval ◽  
Short Time Interval ◽  
Feed Concentration ◽  
Power Intensity

Ultrafiltration is one of the most promising membrane technologies for liquid purification due to its high economic efficiency in the industries. However, it has been faced with a critical problem, called fouling. The contaminants in feed solution tend to accumulate on the membrane surface, hindering permeate solution to pass through the porous spaces. Among the various solutions, application of ultrasound has been considered as the most popular method since it does not suffer a disadvantage of downtime and the filtration process does not need to be stopped for the removal of foulants. In this study, control of ceramic membrane fouling by an on-line intermittent ultrasound system was being investigated. The experiment focused on obtaining optimal operating ultrasonic condition. Frequency (20, 28, and 40 kHz), power intensity (1.44, 2.88, and 5.76W/cm2 ), and time interval of intermittent ultrasound (1, 1.5, and 2 minutes) were the parameters of interest. The effect of feed concentration was also analyzed at optimal ultrasonic condition. The quality and flow rate of the permeate streams were monitored for the evaluation of the process performance. The optimal condition of intermittent ultrasound was found at the frequency of 28 kHz and the power intensity of 2.88 W/cm2 ; and then, the application of intermittent ultrasound with short time interval successfully reduced the operating cost of ultrafiltration process while maintaining acceptable quality and flow rate of permeate solution. There was increase in efficiency of intermittent ultrasound at lower feed concentration.

Fouling analysis of ultrafiltration and nanofiltration membranes

2006 ◽  
Vol 1 (4) ◽  
Author(s):  
D. B. Mosqueda-Jimenez ◽  
P. M. Huck
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Membrane Surface ◽  
Feed Solution ◽  
Nanofiltration Membranes ◽  
Biological Matter ◽  
Membrane Pretreatment ◽  
Microbiological Analyses

Chemical and microbiological analyses were performed in an attempt to obtain a better understanding of the reduction of membrane fouling via the use of feed pretreatment. Biofiltration was chosen as pretreatment due to its potential to be a sustainable process coupled with membrane filtration. Biofiltration effectively reduced the concentration of organic and biological matter in the feed solution, decreasing the material deposited on the membrane surface approximately by half. More importantly, it reduced the loss of permeability during the operation of UF and NF membranes. However, it is believed that the performance of biofiltration as membrane pretreatment can be further improved with a greater understanding of the material that causes membrane fouling. This way the biofilter design and operation can be optimized to specifically minimize the concentration of this fouling material.

Coagulation/flocculation/ultrafiltration for natural organic matter removal in drinking water production

2004 ◽  
Vol 4 (5-6) ◽  
pp. 215-222 ◽  
Author(s):  
A.R. Costa ◽  
M.N. de Pinho
Keyword(s):  
Drinking Water ◽  
Organic Matter ◽  
Natural Organic Matter ◽  
Membrane Fouling ◽  
Membrane Filtration ◽  
Membrane Surface ◽  
Water Production ◽  
Cellulose Acetate Membranes ◽  
Wide Range ◽  
Drinking Water Production

Membrane fouling by natural organic matter (NOM), namely by humic substances (HS), is a major problem in water treatment for drinking water production using membrane processes. Membrane fouling is dependent on membrane morphology like pore size and on water characteristics namely NOM nature. This work addresses the evaluation of the efficiency of ultrafiltration (UF) and Coagulation/Flocculation/UF performance in terms of permeation fluxes and HS removal, of the water from Tagus River (Valada). The operation of coagulation with chitosan was evaluated as a pretreatment for minimization of membrane fouling. UF experiments were carried out in flat cells of 13.2×10−4 m2 of membrane surface area and at transmembrane pressures from 1 to 4 bar. Five cellulose acetate membranes were laboratory made to cover a wide range of molecular weight cut-off (MWCO): 2,300, 11,000, 28,000, 60,000 and 75,000 Da. Severe fouling is observed for the membranes with the highest cut-off. In the permeation experiments of raw water, coagulation prior to membrane filtration led to a significant improvement of the permeation performance of the membranes with the highest MWCO due to the particles and colloidal matter removal.

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