Membrane Technology - Science topic

you can deploy Copilot https://sl.bing.net/hNww0ukRfeS

You will have to try several for your particular powder and fluid to see which works best. Sigma-Aldrich sells several types of Zonyl(TM) fluorosurfactants. Best wishes for success.

Dear Dhiraj Bhalachandra Thakur

In addition to nitrates and nitrites as referred by Peter Donkor we also convert sulfates, sulfites and sulfides biologically to elemental sulfur S° which precipitates as white solids.

Hi Noor Ul Ain

You can fix the adsorbent dose and the concentrations of Cr(VI) and Pb(II). You can measure the remaining concentrations of Cr(VI) and Pb(II) after certain time intervals, e.g. 10, 30, 60, 90, 120 min, and so on, until you achieve adsorption equilibrium.

For Cr(VI) you may seek help from the following article.

Dear Foroogh Khodadadi:

You can benefit from these valuable Links about your topic:

@https://www.researchgate.net/topic/Membrane-Distillation

@https://youtu.be/GWX7grT-DhI

I hope it will be helpful ...

Best wishes ...

DCMD membrane cell can be used in VMD cell on condition that sealing one end of the cold side.

I'm confused by your question. Measuring the zeta potential of a membrane would imply using streaming potential. The Zetameter is a microelectrophoresis instrument. It measures the velocity of particles dispersed in a liquid.

Are you wanting to measure a membrane or particles made from the same material?

By definition, the isoelectric point is the pH at which the velocity of particles in an externally applied electric field is zero. So, you need some kind of instrument to apply an electric field and measure velocity (or flow liquid through a membrane and measure potential).

Nafion™ perfluorosulfonic acid (PFSA) membranes are based on a PFSA/polytetrafluoroethylene (PTFE) copolymer. Nafion™ polymer is used as the proton exchange membranes in polymer electrode fuel cells. Nafion™ polymer is used as a super-acid catalyst in the production of fine chemicals. n practically all applications Nafion membranes are used as dense, non-porous flat sheet membranes with smooth surfaces in electrochemical cells, they function as cation-conducting solid electrolytes. membranes are composed mainly of a polytetrafluoroethylene (PTFE) backbone with side chains containing ether groups and a sulfonic acid unit at its end. Modifications with conducting polymers, such as polyaniline, are studied to reduce the methanol crossover in direct methanol fuel cell applications.The proton exchange membrane is vigorously being developed. While the Nafion (Du pont) has 100 microns thickness and $500/m2 today, the experts says it will be $50/m2 on the production scale 150 thousands of fuel cell cars annuallya specific acid treatment was performed in order to activate the membrane and increase the amount of water molecules per sulfonic group [5] Currently, sulfuric acid (H2SO4) with concentration below 1 M is used in standard method for the activation of Nafion.

I think there is no problem unless the equation defines a different meaning from the original one

Nguyen Anh Pham

Many years ago at Courtaulds we made carbon fiber and the precursor was PAN in NaSCN solution. This was a very viscous polymeric solution and bubbles would break the ‘tow’ (a 10000 filament bundle). We degassed the dope (same name!) by passing a warmed solution into a vacuum funnel via a thin stretched capillary tube. We could even estimate the gas content by the number of fractures of the streaming filament per unit time.

Hello,

Question:

what if a cell treatment give rise to detergent-resistant membranes? Under which category will it be placed? DRM or lipid raft? Thank you.

Exploration of new material combination for improving the performance maybe.

Desalination

Journal of Membrane Science

Desalination and Water Treatment

Hydration Innovation Technology (HTI)

The molecular weights of citrate and acetate are not high. They might permeate out from the bulk liquid. However, selection of membranes depends also on the properties and molecular weight of stuff in the bulk phase. In addition, these two substances are organic acid, so the possibility of corrosion to the surface materials of the membrane must be considered.

Dear Seyed Mohsen Samaei

Regards

The endpoint occurs when operating conditions (temperature, all pressures, circulation rate) and the flux are all stable. When conditions have stabilized, measure the flux, then measure it again a few minutes later. If the values agree, that flux characterizes the particular set of conditions.

It depends on the membrane you make. There is no specific time for the flux to be stabilized. Some of the ultrafiltration membrane reaches a steady state after 30 minutes, the others take more than 2 hours to be stabilized.

Tannins can be precipitated by some polyacrylamide flocculants. It is a trial and error process to identify the most appropriate product. Dose rate is typically tannin x 2.5 .

Gelatin will also usually offer a similar effect.

The addition of Ferrous or Ferric iron and pH adjustment to pH 7 - 8.0 should also produce good results.

Ok. Thank you for your recommendation. I'll look it up. Good luck to your research anyway !

Munish,

This is a very good question. One of the main challenges when dealing with membrane processes is dealing with the retentate (reject) stream. Note that the reject stream is mainly produced in cross-flow configuration and dead-end membrane filtration does not produce a reject. There are many membrane separation processes out there and depending on the process and the target feed stream, reject management could differ. Here are a couple of examples:

Reverse Osmosis (RO) is widely used for seawater desalination (e.g. in California). In this process, seawater is used as the feed stream. Fresh (low mineral content) water is produced in the permeate stream and the reject stream contains the rejected species (ions, suspended solids, etc.). In most cases, rejected stream is discharged into the ocean. However, in cases where RO is used for water desalination in land (far from the coast, such as brackish water treatment), rejected stream has to be managed. Some management techniques are using desalination ponds, thermal evaporation, crystallization, membrane distillation, etc. Regarding in land operations, reject management can lead to significant capital and O&M costs.

Ultrafiltration and microfiltration (combined with oxidation processes) can be used for drinking water treatment. In this case, surface water (such as Lake water) is used as feed for UF or MF system. In this case, the reject stream is usually sent to a municipal wastewater treatment plant for biological treatment and safe discharge into environment.

I need to mention that in some membrane applications, the reject stream is the target product not the permeate! As an example, membrane separation can be used for CO2/CH4 separation. In this case, CO2 is collected in the permeate stream, while CH4 (the target product) is concentrated in the reject. Hence, the permeate needs to managed for safe discharge, not the reject stream.

Thanks for your answer. For the reuse of municipal wastewater, submerged dynamic membrane combined with activated sludge may provide a alternative, which performs well in pollutant removal and is advantageous in membrane cost. The back washing of DM layer was also reported to be easy. I think this technology will be feasible under some occasions.

How to extract this index of damage in the structure by the results of the analysis of nonlinear time history of IDA

Membrane Distillation (MD) is most certainly a viable technology, and compete with more traditional technologies such as Seawater RO and Multi-Effect Distillation (MED) plants. Membrane Distillation is a newer technology, has more companies entering the market but still lacks large number of commercial installation. Companies such as Memsys from Germany has Membrane Distillation product, has sold large systems in China, and has done pilot plant work in the USA.

Based on my evaluation, MD technology should be considered for desalination of non-traditional sources of wastewater including reject streams from Cooling towers, Air scrubbers blowdown streams and coal pile runoff from power plants, RO reject streams, etc. If waste heat is available (Example, condensate loop or air stack for power plants) then the technology could be more affordable, will require less power.

Most Membrane Distillation technologies are made with the materials that can be exposed to wide pH range, wide range of chemicals, oxidizing environment, etc.

Best regards,

Ken Pandya

Office 001 972 733 4404

Evonik Membrane Extraction Technologies (MET) Ltd.

Address: Wharfeside/Rosemont Rd, Wembley HA0 4PE, United Kingdom

Phone: +44 20 8902 0040

pH range for membrane operation is usually between 2 to 11. If pH is more than 11 the membrane will be damaged. You can ask the membrane manufacturer and let us know.

Hi Nguyen,

Yes I think so. With my experience, room temperature is the ideal. But maximum should be around 6-8 hrs in room temperature. But if we want to keep longer, it is better to keep at 4 degrees. When temperature is decreased, incubation time should be increased.

No the average is always greater then 40.

also the seawater can reach up to be 33% but more than this I don't know what kind of seawater you have unless you have closed seas.

perfluorinated sulfonic acid/PTFE copolymers

Ammonia can be liberated by biological action leaving a hydroxyl in its place.

The anode reaction is a catalyzed oxidation of urea and any ammonia that forms. A deficiency of electrons on the anode destabilizes the fuel such that the catalyst is able to activate the oxidation mechanism at moderate temperature.

Over all efficiency increases with temperature, leading to research on porous heat resistant materials.

Hello Jeng

If you are asking in respect to Alan's answer, then definitely phenomenon will be equally applicable, but there will be no control over flow rate and TMP. If valve is in closed position then even it will behave like a dead end system.

According to the characteristics of the membrane, such as pore size and material, and testing conditions, such as wet or dry, as well as its applications, there are many different ways to measure the mean pore size of the membrane. I have lots of experience in characterize the pore size of a polymeric membrane for water separation. You can find the details from my publications.  

I also suggest you to take a look here:

For our work, we took it as a good example for the construction of module. More particularly, we faced two flat sheet modules with a distance of about 2 cm and with a controlled but continue air scouring from the bottom of these. The structure well supported our purposes (http://www.sciencedirect.com/science/article/pii/S0960852416314602).

Hi Norbert,

Thanks for your answer. I did go to lab bench and discovered that the signal units were wrong. The set-up manual says not to worry about this, because the units will be telegraphed from the Multiclamp 700B amplifier automatically, but I have been worrying about this. I think I've found the answer to my problem. There is a section in Multiclamp 700B just above where you change the Bessel filter setting. This can either say "Membrane potential" or "Membrane current" or a number of other things. I didn't realise that you could change this, but if you click on those words and drag the mouse up or down, you can change what the amplifier is measuring when in I=0 mode. I didn't think it made a lot of sense to be able to measure "membrane current" in I=0 mode, but for some reason that was the default setting in Multiclamp 700B. I changed it to "membrane potential" and now it works. I've been trying to sort this problem out for weeks! I hope this helps somebody else in the future.

Best wishes,

Theresa

HI,

If you use polyimide or polyamide then yes definitely it will cross-link.

Please go through the articles published by Katrien van Herck and Ivo vankelecom from KU Leuven, Belgium.

Regards,

Parimal

Burn the sludge before dissolution with the acid.

Dear Ramesh,

ASTM International. F838-05 Standard Test Method for Determining Bacterial Retention of Membrane Filters Utilized for Liquid Filtration (2005); http://webstore.ansi.org/ansidocstore/product.asp?sku=ASTM+F838-05

Bowman, F.W., Calhoun, M.P., and White, M. “Microbiological Methods for Quality Control of Membrane Filters”, J. Pharm. Sci. 1967, 56: 222-225.

Regards

Krishna

Dear Tamilarasan,

The attached file contains a study which demonstrate that constant transmembrane pressure is comparable to constant permeate flux (see Figure 8):

Daniel J. Miller, Sirirat Kasemset, Donald R. Paul, Benny D. Freeman

Journal of Membrane Science 454 (2014) 505–515

Membrane fouling is often characterized in the laboratory by flux decline experiments, where an increase in transport resistance due to accumulation of foulants on and/or in a membrane is manifested as a decrease in permeate flux with filtration time at fixed transmembrane pressure. However, many industrial microfiltration and ultrafiltration applications operate at constant permeate flux, and there are few reports comparing these modes of operation. In this study, emulsified oil fouling of polysulfone ultrafiltration membranes was studied using both constant permeate flux and constant transmembrane pressure experiments. Mass transfer resistance changes during fouling were compared between constant flux experiments and constant transmembrane pressure experiments performed at an initial flux equal to the flux imposed during the constant flux experiment. At low fluxes, the transport resistance and its change with permeate volume per unit area agreed within experimental error regardless of operational mode. In contrast, at high fluxes, the change in membrane resistance with permeate volume per unit area was much higher in constant flux than in constant transmembrane pressure experiments. The threshold flux, defined recently as the flux at which the rate of fouling begins to increase rapidly, separates the regimes of good and poor agreement between the two types of experiments. The weak form of the critical flux, below which spontaneous adsorption is the only significant resistance imposed by foulant, was also observed.

Hoping this will be helpful,

Rafik

Whether or not the film can be detached from the substrate depends on the type of the polymer (interaction between the two). Try to immerse the coated glass in a water bath right after coating; you can slightly peel a tiny edge for initiation. I am not really working on integrally asymmetric membrane, but I guess you usually need this process for phase inversion if the water is your non-solvent. If it doesn't work, try to use an acrylic glass slide instead. It worked for me to make a cellulose freestanding film.

Dear Caesar,

Please read the following text:

Dicopper chloride trihydroxide Cu₂(OH)₃Cl is a green crystalline solid. It decomposes above 220 °C with elimination of hydrochloric acid to oxides of copper. It is largely stable in neutral media, but decomposes by warming in alkaline media, yielding oxides. It is virtually insoluble in water and organic solvents, soluble in mineral acids yielding the corresponding copper salts, soluble in ammonia, amine and EDTA solutions under complex formation. It can easily be converted to copper hydroxide by reacting with sodium hydroxide. Its pH in water is 6.9 measured by EPA method SW846-9045.

Copper(I) chloride is a Lewis acid, which is classified as soft according to the Hard-Soft Acid-Base concept. Thus, it tends to form stable complexes with soft Lewis bases such as triphenylphosphine:

CuCl + P(C₆H₅)₃ → [CuCl(P(C₆H₅)₃)]₄

Although CuCl is insoluble in water, it dissolves in aqueous solutions containing suitable donor molecules. It forms complexes with halide ions, for example forming H₃O+ CuCl₂− with concentrated hydrochloric acid. It is attacked by CN−, S2O32−, and NH3 to give the corresponding complexes.

Solutions of CuCl in HCl or NH₃ absorb carbon monoxide to form colourless complexes such as the chloride-bridged dimer [CuCl(CO)]₂.

Hoping this will be helpful,

Rafik

Just to complement what Konstantinos said, the pressure is not an input parameter, it is the resulting output of the interaction between your membrane and your mixed liquor. That is, the lower your sludge filterability, the higher the filtration resistance therefore the higher the pressure you need to apply in order to produce your permeate. Just make sure that you apply a flux which allows you to keep the desired HRT without exceeding the membrane manufacturer's recommended maximum pressure.  check out this paper and the references in it. cheers, CMB

Chloroform and 1,1,2-trichloroethylene (TCE) are definitely good solvents for PPO. 

You must know the feed seawater condition and the feed after chemical pretreatment from SDI, pH, TDS, and the temperature. Then you can choose the appropriate type of membranes. The least pressure, is the pressure just greater than the net driving pressure (which  depends on the feed TDS).   

I assume you are using ion exclusion chromatography. If so you have two options: 1. Increase the temperature analysis, 2) Lower the H2SO4 concentration such that lactic acid starts to acquire a negative charge while acetic acid remains protonated (uncharged). In the second case the retention time for lactic acid should decrease while the one for acetic acid increase. 

Mobile phase choice is dependent on the sample, detection requirements and separation desired. A true column void time should not vary with mobile phase so ideally use your actual sample method mobile phase to find and calculate it.

Dear Natalia, 

Thank you so much for the help.

Dear Mohamed,

You can check the followings:

The Winflows reverse osmosis (RO) system design and simulation software program brings advanced RO simulation to a whole new level. Some of the program features include:

3-Pass systems

Permeate split and recycle

Anti-scalant dosing

Energy Recovery Devices

Ability to combine stages

Much more

The program is an intuitive and user-friendly simulation, which makes it easy to quickly design a simple system or the most complex system without difficultly. The first program to incorporate other simulation packages, Winflows can recommend pretreatment chemicals and their dosage rates if needed.

ROSA (Reverse Osmosis System Analysis) design software continues to evolve and grow to meet your demanding system design needs. The latest version, ROSA 9.1, is now available to aid in system design using DOW FILMTEC™ elements, the highest quality RO and NF elements available globally. Download ROSA 9.1 now to begin recognizing the benefits today.

Hoping this will be helpful,

Rafik

For fast crystallization, you can create some inter-phase by seeding with small crystal of copper sulfate or put a glass rod inside the solution. As mentioned by Rafik Karaman, the crystals obtained will be hydrated copper sulfate, so you have to heat it to obtain anhydrous copper sulfate.

Dear Ahmad,

You may check the following links:

Soluble chloromethylated polymers of styrene and alpha-methyl styrene, their quaternary ammonium salts and method of making the same

US 2694702 A

Hoping this will be helpful,

Rafik

Dear Heba, you can but you don't have to strip a blot. Stripping will always loose in sensitivity. But you can check in a slightly different way. Make a SDS-PAGE with a larger well 1 to 2 cm or even larger, e.g. one well per gel). Add your sample (calculate/increase the sample size according to the width of your well), run the gel and transfer it as usual. After transfer cut the blot in small stripes as small as 1 to 2 mm is no problem or as small as you like. Store the stripes at -20. Proceed with the respective slice whenever you like by blocking, incubation with your abs. If you go as small as 1 mm, beware that the blot can turn around without your notice! So the band may occur at the opposite side. Good luck

Dear Shailendra,

The following link contains a publication which describes a design of Spiral-Wound Modules.

Hoping this will be helpful,

Rafik

Abdorazzah,

Performing at this concentration You will have the indicated problem. From my experience, the maximum concentration of psf that I worked in nmp was 12%. You are using a ternar mix (two polymers in the same solvent, nmp) at a very high concentration. 

My advice is to use the same proportion (3/1) psf/pvp at a lower concentration in order to get a nice, straight, porous membrane (maximum 9 wt% psf and 3wt % pvp per 100 ml nmp). You will see that this way works.

For higher concentration of polymer (psf and pvp) in nmp solution, You will experience a very high viscosity and You will have no option to obtain a thick layer.

Good luck!

Try a different membrane material, as mentioned above. You also may want to try a smaller cutoff . . . roughly 1/3 kDa was what I was always taught, but proteins are shaped differently. If it's long and skinny (tube-shaped, etc.), it could be slipping through the membrane that way and, therefore, you'd want to use an even smaller cutoff. Have you tested the flow through on the Amicon to see if your protein is getting through?

Prem Sir, 

Very sorry. I found the links. Thank you very much Sir

I think gradually we are coming closer in our thinking.

Regarding your question on carbon supply to fungus:

Membrane should allow transfer of nutrients (N, P) as well as carbon from water-side surface to air-side surface for limited growth of fungus. The source of N. P. and C is the water flowing on the membrane sheet. The generated O2 by fungal activity is diffused to water-side surface to keep the aerobic condition (limited aerobic condition okay) on the inner side of the water flowing on the membrane sheet.

I think nano porous ceramic (or similar kind material) membrane would serve my purpose. Its making may require some blending (of other material) to keep the porous nature of the membrane as well as to prepare the required surface characteristics (of air-side and water side surface of the membrane). 

Nanofiltration (NF) is a pressure-driven membrane process with performance characteristics between reverse osmosis (RO) and ultrafiltration. The theoretical pore size of the membrane is 1 nm, although there are no pores in thin-film composite spiral-wound NF membranes (when made of polyamide the surface is slightly negative).NF will have a high removal (high rejection) of sulfate because it is a divalent ion, but will have lower rejection of monovalent ions such as sodium. 

Mass transfer of solutes across the active membrane thin-film can be predicted using the homogeneous solution-diffusion model as first illustrated by Kedem and Katchalsky in 1958 (Biochimica et Biophyica Acta, 27:123) as well as with the use of sieving models. I would agree with others that a molecular weight cutoff of between 300 and 400 would suffice for sulfate removal using a NF membrane process, as sulfate removal is primarily a function of the Donnan effect. I would also agree that you would not see much sulfate removal in a membrane having a MW cutoff of 1000 or more.

Separation of ionic species by NF strongly depends on the membrane charge and molecular weight cutoff. A membrane with a smaller MW cutoff is better able to retain ionic species. Likewise, a highly charged membrane is better able to exclude co-ions (ions of same charge as the membrane) from the membrane surface. RO for sulfate removal is generally only considered when monovalent contaminants must also be removed.  Otherwise, NF is more cost-effective for sulfate removal than is RO.

See:

Peeters et al. (1998). Retention measurements of nanofiltration membranes with electrolyte solutions. J. Membr. Sci. 145, 199.

Tsuru et al. (1991). Reverse osmosis of single and mixed electrolytes with charged membranes: Experiments and analysis. J.Chem. Eng. Jpn. 24, 518.

Duranceau and Taylor. "Solute Charge and Molecule Weight Modeling for Prediction of Solute Mass Transfer Coefficients." American Water Works Association Seminar Proceedings: 1993 Membrane Technology Conference. Baltimore, MD: AWWA, 243-249 (1993).

Dear Nurul

If you have access to a confocal microscope (CLSM) you may simply fix and permeabilise  the cells, stain them with alexa-488 coupled phalloidin and propidium iodide, cut the inserts in small pieces and mount on coverslips with the cells facing the coverslip. This will allow you to see the cells, without interference from the polycarbonate support (due to the CLSM's ability to make optical slices)

BR Birger

None that I know of.  In our behavioral studies, we painted kissing bugs and ticks with fluorescent paint and tracked their movements with a video camera and fluorescent lamps, working in a dark room.  See paper by Milne, Sonenshine and others.

Dr. Sonenshine

Hi

I dont know which polymers you are using. If the polymers are insoluble in ethanol then you can put some ethanol on the surface of thin membrane. It will slightly coagulate the formed membrane and might help in detaching the membrane.

I hope this trick might help you.

Regards,

Parimal

 Thank you all for your answers,

I think that the problem arises from residual NMP in the membrane. I used to heat the membrane in a vacuum oven to 120 C after detachment. Know I'm testing to detach it after heating in vacuum :) and no deformation.

The permeances of gases through polymers generally follows the sequence: :H2O > CO2> O2> N2.  O2/N2 selectivity varies from a low ~ 2 for PDMS to highs of  7-10 for glassy polymers.  You can easily make a pressurized residue stream with ~ 1-2% O2 from air using membranes (for example google MEDAL Air Liquide membrane & look at N2 applications).  You will be able to do this from the diesel exhaust gas with some pre-treatment.  There are definitely commercial membranes that would work with some residual HC in the exhaust gas but there  is an economic trade-off.  Permanent gases are not usually a problem but you want to consider NOx and SOx.

Dear friend,

As mentioned as above,it depends on material composition,feed solution and preparation condition.But ideally it should be stable during separation experiments ,so we can reuse membrane.Mostly Pervaporation membrane is cross-linked membrane with controlled swelling,which affect the selectivity and flux directly.If your membrane have good cross-linking density which is stable during pervaporation separation than you can reuse it easily.During reusing you have to just take the reading after minimum 1 hour,because membrane established equilibrium with feed and permeate during this time,  according to swelling property.

Dear Jyoti,

There are four different methods to determine the permeability of metal ions such as  Ca ⁺⁺ or Mg⁺⁺ through membranes:

A number of chelators of divalent cations have different fluorescence spectra in the bound and unbound states. Chelators for Ca²⁺ are well established, have high affinity for the cation, and low interference from other ions. Mg²⁺ chelators lag behind and the major fluorescence dye for Mg²⁺ (mag-fura 2) actually has a higher affinity for Ca²⁺.This limits the application of this dye to cell types where the resting level of Ca²⁺ is < 1 μM and does not vary with the experimental conditions under which Mg²⁺ is to be measured. Recently, Otten et al. (2001) have described work into a new class of compounds that may prove more useful, having significantly better binding affinities for Mg²⁺.The use of the fluorescent dyes is limited to measuring the free Mg²⁺. If the ion concentration is buffered by the cell by chelation or removal to subcellular compartments, the measured rate of uptake will give only minimum values of k_m and V_max.

First, ion-specific microelectrodes can be used to measure the internal free ion concentration of cells and organelles. The major advantages are that readings can be made from cells over relatively long periods of time, and that unlike dyes very little extra ion buffering capacity is added to the cells.

Second, the technique of two-electrode voltage-clamp allows the direct measurement of the ion flux across the membrane of a cell. The membrane is held at an electric potential and the responding current is measured. All ions passing across the membrane contribute to the measured current.

Third, the technique of patch-clamp uses isolated sections of natural or artificial membrane in much the same manner as voltage-clamp but without the secondary effects of a cellular system. Under ideal conditions the conductance of individual channels can be quantified. This methodology gives the most direct measurement of the action of ion channels.

Maguire, M.E.; Cowan, J. A. (2002). "Magnesium chemistry and biochemistry". BioMetals 15 (3): 203–210. 

Tevelev, A.; Cowan, J. A. (1995). J.A. Cowan, ed. Metal substitution as a probe of the biological chemistry of magnesium ion. The Biological Chemistry of Magnesium (New York: VCH).

Drakenberg, T. (1995). J. A. Cowan, ed. Physical methods for studying the biological chemistry of magnesium. The Biological Chenistry of Magnesium (New York: VCH).

Raju, B.; Murphy, E.; Levy, L. A.; Hall, R. D.; London, R. E. (1989). "A fluorescent indicator for measuring cytosolic free magnesium". Am J Physiol Cell Physiol 256: C540–548.

Grubbs, R. D. (2002). "Intracellular magnesium and magnesium buffering". BioMetals 15 (3): 251–259.

Otten, P.A.; London, R.E.; Levy, L. A. (2001). "4-Oxo-4H-quinolizine-3-carboxylic acids as Mg2+ selective, fluorescent indicators". Bioconjugate Chemistry 12 (2): 203–212. 

Gunzel, D.; Schlue, W.-R. (2002). "Determination of [Mg2+]i - an update on the use of Mg2+-selective electrodes". BioMetals 15 (3): 237–249. 

Hille, B. (1992). "2". Ionic channels of excitable membranes. Sunderland: Sinauer Associates Inc. ISBN 0-87893-322-0.

Dean, J.R. (1997). Atomic Absorption and Plasma Spectroscopy. Chichester: John Wiley & Sons. ISBN 0-471-97255-X. for descriptions of the methodology as applied to analytical chemistry.

Hoping this will be helpful,

Rafik

You can use the UV-induced photografting to hydrophilize the PP membranes.Dopamine-assisted deposition is also a good choice as a very simple process. You can just immerse your membrane into the dopamine or dopamine/polymer solution for severals hours. You can find more details in these literatures (J. Mater. Chem. A, 2014, 2, 10225-10230; J. Membr. Sci., 2015, 483,  42-59 ).

Try adding surfactant (4-5% of SLS) into the gelation/precipitation bath before you submerge the cast film and keep the water temperature at RT or little higher. Is your problem with polysulfone based polymer only or others too? some people use casting on a support, particularly for polysulfone polymers. hope this helps.

to get a copy of 

ASTM D1141 - 98(2013) - Standard Practice for the Preparation of Substitute Ocean Water, the link:

Dear Shradha Mawatwal,

I refer you to the following link which contains good answers to a similar question to yours:

Hoping this will be helpful,

Rafik

sir, i have to separate mostly alcoholic/water azeotropic mixtures and many more....are these membranes fit for such separations.

Here are two links comparing PVDF and nitrocellulose.  Nitrocellulose may be preferred for low weight molecules or certain applications like nucleic acid analysis, but in your case, you're probably looking at a protein heavier than 20 kDa, and the better durability of PVDF is better for reprobing, so you can analyze both total or un-phosphorylated versus phosphorylated protein.  In addition PVDF has greater sensitivity if you need it.

Hi Wei-Xiong,

I presume you are trying to remove the glycan attached at the surface of plasma membrane proteins. You can treat your cells with PNGase which will remove surface glycans (you may need to co-treat you cells with neuraminidase too to improve PNGase efficiency). Also, if you want to prevent glycosylation of newly synthesized proteins you may want to treat your cells with Tunicamycin - but it will likely alter the trafficking of proteins to the cell surface. We have been using these strategies in this study http://www.ncbi.nlm.nih.gov/pubmed/23503728

Hope this helps. Norbert

Acid/base cycle treatment is always recommanded to regenerate membrane after use, but you have to check reproductibilty of exchange properties.

A lot of washing cycle may deterior membrane squeleton.

Dear Sahar kh,

The following publication entitled " Constant-Pressure Measurement of SteamWater

Relative Permeability"  describes a method for permeability determination using constant pressure:

Abstract

A series of steady-state experiments have established relative permeability curves for two-phase flow of water in a porous medium. These experiments have minimized uncertainty in pressure, heat loss, and saturation. By attempting to maintain a constant pressure gradient, the experiments have provided a baseline from which to determine the effect of temperature on relative permeability.

The use of a flexible heater with an automatic control system made it possible to assume negligible phase change for the mobile fluid. X-ray computer tomography (CT) aided by measuring in-situ steam saturation more directly. Mobile steam mass fraction was established by separate steam and water inlets or by correlating with previous results. The measured steam-water relative permeability curves assume a shape similar to those obtained by Corey (1954) for the simultaneous flow of nitrogen and water. Close agreement between the curves by Satik (1998), Mahiya (1999), and this study establishes the reliability of the experimental method and instrumentation adopted in these experiments, though some differences may bear further investigation. In particular, the steam phase relative permeability appears to vary much more linearly with saturation than does the water phase relative permeability.

For more details, please use the following link:

Hoping this will be helpful,

Rafik

I am assuming your are looking for production quantities. Other wise Whatman, Cole Parmer or dozens of other distributors of filter discs have or can package this off of sheets.

Thank you Mr. Manish Jain for your clarifications and hope to ask you if i can consider the variation of solute concentration along the thickness of the membrane in addition to measure the impact of spacer'c geometry as well. Hope you have a link for such studies you can guide me to add it to what i have found.

please accept my regards

Mudhar

Thanks all!

Dear Zhang,

GuassView is an illustration program. There is no possibility to conduct any calculations with this program. GuassView a program that can view results from G09 and etc.

Regarding your question, you can use Materials Studio program.

Please use the following links to get familiar with this program:

For free download, please use the following link:

Hoping this will be helpful,

Rafik

If the 2 compounds bind to each other so strongly that they can't be separated by chromatography, then they probably wouldn't be separated by size-differential dialysis either, even if such selective tubing existed, which I doubt. You need to find a solvent in which the compounds are not tightly bound, and separate them by chromatography. Of course, if they are really covalently bound, then this will be impossible.

In our work we use RH1692.  The per cent change in fluorescence corresponding to membrane voltage change is low (typically <1%) so we need to use a high dynamic range CCD camera (DALSA 1M60).

There is a good explanation in the voltage sensitive dye section of materials and methods available here:

Dear Rosa,

The efficiency of TiO2 as a photocatalyst is dependent on the initial concentration of the pollutant, the amount of light penetration to the surface of TiO2, and the duration of light irradiation. The surface area of the catalyst is a key factor in catalytic reactions.

TiO2 based photocatalysts with large surface area show high photocatalytic efficiency, and thus nano-sized TiO2 has been used in most studies. The results have shown that nano-sized TiO2 suspended in solution outperforms its bulk counterpart regardless

of the morphology.

For more information regarding this topic see the following link which contains a review article entitled " TiO2 based photocatalytic membranes: A review" by Leong et al. published in Journal of Membrane Science (2014).

file:///C:/Users/Rafik%20Karaman/Downloads/2014-JMS_TiO2%20based%20photocatalytic%20membranes%20A%20review.pdf

Hoping this will be helpful,

Rafik