Explore our new PFAS-Free products designed specifically for PFAS testing!
  • Sign In
  • Create an Account
Toggle Nav
My Cart
My Quote
  • Compare Products
Menu
Account
Forward Osmosis (FO) Membranes
Sterlitech Forward Osmosis Flat Sheet Membranes

Forward osmosis, also known as engineered osmosis, is a membrane separation process which takes advantage of a pressure gradient between two solutions of different concentrations to make the solvent move from one side of the membrane to the other.

The pressure gradient that powers the process is naturally generated by the tendency of the solvent to permeate over to the side of the membrane with the higher concentration of solute. Relying on this natural tendency means that FO requires much lower pressures than other membrane processes to operate (such as reverse osmosis) and, consequently, lower energy requirements.

FTS H2O™ flat sheet membranes are composed of cellulose and are low-fouling. They are able to process precipitating salts and polymerized organics with minimal impact on the process. 

*Aquaporin FO membranes are now ONLY available in Hollow Fiber format. 

 
SKU Product Name Designation Polymer Size Pack Size Est Ship Price
1121818 FTSH2O Flat Sheet Membrane, CTA, FO, 305 x 305mm, 1/Pk CTA Cellulose Triacetate 305 x 305 mm 1 1-2 days
$233.77
View Details
1121819 FTSH2O Flat Sheet Membrane, CTA, FO, 305 x 305mm, 5/Pk CTA Cellulose Triacetate 305 x 305 mm 5 1-2 days
$984.71
View Details
1121820 FTSH2O Flat Sheet Membrane, CTA, FO, Sepa, 5/Pk CTA Cellulose Triacetate Sepa 5 1-2 days
$515.37
View Details
1121821 FTSH2O Flat Sheet Membrane, CTA, FO, CF042, 5/Pk CTA Cellulose Triacetate CF042 5 1-2 days
$179.50
View Details
1121822 FTSH2O Flat Sheet Membrane, CTA, FO, 47mm, 5/Pk CTA Cellulose Triacetate 47 mm 5 1-2 days
$92.98
View Details
1121823 FTSH2O Flat Sheet Membrane, CTA, FO, CF016, 5/Pk CTA Cellulose Triacetate CF016 5 1-2 days
$236.25
View Details
per page
Set Descending Direction

Frequently Asked Questions

Yes—flat sheet membranes can be cut to fit your stirred cell. For best results, use the stirred cell support disk as a template to trace the correct size, then cut the membrane carefully to match.

Yes, we can supply the flat sheet membranes in the correct disk size for your stirred cell. Please contact us at [email protected] for pricing and availability.

Used flat sheet crossflow membranes must be stored wet at all times. If a membrane is allowed to dry out, it can irreversibly lose water permeability and performance.

For storage, place the membrane fully submerged in one of the following solutions:
0.5% formaldehyde solution (helps prevent microbial growth)
1.0% sodium metabisulfite (SMBS) solution -- Replace the SMBS solution monthly to maintain effectiveness

UPDI water (ultrapure deionized water)--Replace the water weekly to reduce contamination and biofouling

Yes, we are able to offer some of the flat sheet membranes as roll stock. Please contact us at [email protected] to inquire about pricing and availability.

Flow characteristics for a spiral element and flat sheet membrane are significantly different and are really only comparable on a qualitative basis. Variability in the membrane manufacturing process, differences in water composition, test procedures, and test equipment, used in a factory, laboratory, or elsewhere, will impact water flux results.

Reference: Understanding Variation of Experimental Flux and Rejection

We do not offer complimentary samples of the flat sheet crossflow membranes. However, most customers find the standard pack quantities to be quite reasonable for initial evaluations. For customers that want to evaluate several different membranes, we do offer custom variety packs. And, in some instances, we may be able to offer custom packs containing smaller sheet quantities. Please contact us to inquire about pricing and availability.

Sterlitech flat sheet crossflow membranes should be stored sealed in the original packaging in a climate-controlled environment, protected from direct light, heat, and temperature extremes. While we recommend using membranes as soon as practical after receipt, most flat sheet membranes can typically be stored for up to one (1) year without affecting performance when stored properly.

Post use, the membrane should be rinsed with water after testing and stored in clean water if the storage duration will be less than 24 hours.  If the membrane is rinsed with water and expected to be stored for longer than 48 hours, it is recommended to use a 1% sodium metabisulfite (SMB, chemical formula Na2S2O5) to prevent bacterial growth from occurring. Periodically inspect the membranes for biological growth. If the preservative solution is cloudy you need to replace it.  Renew the preservative solution every month.
Membranes should be stored in the fridge. Do not allow to freeze. Membranes should be stored away from sunlight. 
Some manufacturers supply their membrane in wet to prevent the membrane from going dry. There is always moisture in these sealed bags and it is not uncommon for some condensation (droplets) to form.
Rinsing the membrane on both sides with a stream of clean water is sufficient to remove the preservative solution. There is no need to pre-condition.
Yes, you need to pre-wet the membranes. The best procedure is to place them in a dry holder and allow them to wet from the inlet side first. It may be best to perform this operation with water or a buffer, then dispose of the first rinse, and introduce the process fluid. This prevents any wetting agents or preservatives from mixing with the process solution.
Prior to use, the FTSH2O™ flat sheet membranes should be rinsed with DI water. Keep membranes moist at all times, the membranes should not be allowed to dry.
Yes, you may attempt to reuse flat sheet membranes. However, you may find it difficult to achieve a leak free seal. The cell body o-rings necessarily compress the membrane during installation and the physical action of separating the membrane from the o-rings during removal may cause damage. This damage can impede that ability to achieve a leak free seal when the membrane is reused.
Unfortunately, allowing a previously wetted crossflow membrane to dry usually results in permanent reduction of water permeability. Nevertheless, you can attempt to re-wet the membrane and use it. First, soak the membrane in a 50% alcohol solution for at least 15min (ethanol, methanol, or IPA would be acceptable). Next, install the membrane in the test cell and operate the cell with purified deionized water as though you were pre-conditioning the membrane. After about 30min, the permeate flux should stabilize to whatever rate the membrane is now capable of.
Determining which solution to use to clean a flat sheet membrane depends on the substance it is fouled with. As a general rule, you can use a caustic or oxidant solution for organic fouling and an acidic solution for inorganic causes. Please remember that different membranes polymers have different pH tolerances.

Slight change in color towards yellow/brown is completely harmless and caused by the chemicals used in the production process of the Aquaporin Inside FO membranes . This change in the color does not affect Aquaporin Inside membrane's characteristics or performance.

Yes, for flat sheet membranes that will be used with water or aqueous solutions, we recommend that you pre-condition the membranes prior to conducting your separation experiments. Pre-conditioning helps ensure that the membranes perform as expected. Also, pre-conditioning removes preservatives and other residuals from the membranes. Purified deionized water is used to pre-condition the membranes. For all flat sheet membranes except the forward osmosis (FO) membranes, install the membrane in the test cell and apply the purified deionized water feed at the normal operating rate and pressure for the membrane. Allow the system to operate with the purified deionized water feed until the permeate flux stabilizes at an expected value. You can now replace the purified deionized water feed with your feed solution and begin your experiments.

The active side of the membrane (as indicated by the packaging) should be facing the feed solution.

Most membrane manufacturers recommend CFVs of 5 to 35cm/s for their spiral wound membrane elements. The flat sheet membranes can be operated in this range to simulate use in such elements. Additionally, the flat sheet membranes may be operated outside of this range by users that want to examine the relationship between CVF and fouling and membrane performance in their applications.
Cross flow velocity (CFV) is the linear velocity of the feed flow tangential to the membrane surface and is typically reported in m/sec or ft/sec. It is calculated by dividing the volumetric flow rate through the feed channel by the cross-sectional area of the feed channel. Please refer to the CFV article at Tech Tips for more information.
The recommended TMP will depend on the type of flat sheet membrane and on the application. Typically, a reasonable TMP will be the same as that noted for the permeate flux specification of the membrane. The specifications for any of the flat sheet membranes can be easily found on our website by clicking the “application/specification” tab on the product web page and scrolling down as necessary. Please contact us at [email protected] if you need additional assistance.
These membrane sizes are intended for use in the bench-scale crossflow test cells offered by Sterlitech. Please see the list of flat sheet membranes we offer and their dimensions: HP4750 Stirred Cell: 47 mm (1.85") discs, CF016 cell: 58 x 75 mm (2.26 x 2.95") coupons, CF042 cell: 56 x 115 mm (2.20 x 4.53") coupons, Sepa CF cell: 140 x 190 mm (5.51 x 7.48") coupons, CF047 circular cell: 47 mm discs, CF090 circular cell: 90 mm discs

You can estimate the rejection of forward osmosis membranes by using the following formula, where Cp is the concentration of solute in the permeate and Cf is the concentration of solute in the feed:
R= 1-(Cp/Cf)

Sterlitech Forward Osmosis Flat Sheet Membranes

Selection Tool

Designation
Size
Related Blog Posts

Part 1: Utilizing Membrane Technologies for Produced Water Treatment

Filtration Resources

Wednesday, November 12, 2025

Produced water, a major byproduct of oil and gas extraction, contains hydrocarbons, salts, metals, and chemicals, with chloride and sodium being most prevalent. The water-to-oil ratio can range from 3 to 10, depending on the well. Managing this complex wastewater is challenging, driving the use of membrane technologies that efficiently meet discharge and reuse standards compared to conventional methods.

Read More

Understanding Variation of Experimental Flux and Rejection

Filtration Resources

Monday, January 13, 2025

Membrane performance can vary due to lot-to-lot variance, making it reasonable to expect performance differences when testing  a smaller area of membrane. Polymeric membranes are widely used across various industries and are typically produced in large batches using processes such as phase inversion and interfacial polymerization. Achieving consistent performance across the entire membrane area, and across different batches is challenging due to the complexity of the production process and the scale of manufacturing. The following sections provide a short summary of the membrane production process, focusing on phase inversion and interfacial polymerization techniques.

Read More

Compare Products
  1. Remove This Item
Compare
Clear All
You have no items to compare.

Frequently Asked Questions

Yes—flat sheet membranes can be cut to fit your stirred cell. For best results, use the stirred cell support disk as a template to trace the correct size, then cut the membrane carefully to match.

Yes, we can supply the flat sheet membranes in the correct disk size for your stirred cell. Please contact us at [email protected] for pricing and availability.

Used flat sheet crossflow membranes must be stored wet at all times. If a membrane is allowed to dry out, it can irreversibly lose water permeability and performance.

For storage, place the membrane fully submerged in one of the following solutions:
0.5% formaldehyde solution (helps prevent microbial growth)
1.0% sodium metabisulfite (SMBS) solution -- Replace the SMBS solution monthly to maintain effectiveness

UPDI water (ultrapure deionized water)--Replace the water weekly to reduce contamination and biofouling

Yes, we are able to offer some of the flat sheet membranes as roll stock. Please contact us at [email protected] to inquire about pricing and availability.

Flow characteristics for a spiral element and flat sheet membrane are significantly different and are really only comparable on a qualitative basis. Variability in the membrane manufacturing process, differences in water composition, test procedures, and test equipment, used in a factory, laboratory, or elsewhere, will impact water flux results.

Reference: Understanding Variation of Experimental Flux and Rejection

We do not offer complimentary samples of the flat sheet crossflow membranes. However, most customers find the standard pack quantities to be quite reasonable for initial evaluations. For customers that want to evaluate several different membranes, we do offer custom variety packs. And, in some instances, we may be able to offer custom packs containing smaller sheet quantities. Please contact us to inquire about pricing and availability.

Sterlitech flat sheet crossflow membranes should be stored sealed in the original packaging in a climate-controlled environment, protected from direct light, heat, and temperature extremes. While we recommend using membranes as soon as practical after receipt, most flat sheet membranes can typically be stored for up to one (1) year without affecting performance when stored properly.

Post use, the membrane should be rinsed with water after testing and stored in clean water if the storage duration will be less than 24 hours.  If the membrane is rinsed with water and expected to be stored for longer than 48 hours, it is recommended to use a 1% sodium metabisulfite (SMB, chemical formula Na2S2O5) to prevent bacterial growth from occurring. Periodically inspect the membranes for biological growth. If the preservative solution is cloudy you need to replace it.  Renew the preservative solution every month.
Membranes should be stored in the fridge. Do not allow to freeze. Membranes should be stored away from sunlight. 
Some manufacturers supply their membrane in wet to prevent the membrane from going dry. There is always moisture in these sealed bags and it is not uncommon for some condensation (droplets) to form.
Rinsing the membrane on both sides with a stream of clean water is sufficient to remove the preservative solution. There is no need to pre-condition.
Yes, you need to pre-wet the membranes. The best procedure is to place them in a dry holder and allow them to wet from the inlet side first. It may be best to perform this operation with water or a buffer, then dispose of the first rinse, and introduce the process fluid. This prevents any wetting agents or preservatives from mixing with the process solution.
Prior to use, the FTSH2O™ flat sheet membranes should be rinsed with DI water. Keep membranes moist at all times, the membranes should not be allowed to dry.
Yes, you may attempt to reuse flat sheet membranes. However, you may find it difficult to achieve a leak free seal. The cell body o-rings necessarily compress the membrane during installation and the physical action of separating the membrane from the o-rings during removal may cause damage. This damage can impede that ability to achieve a leak free seal when the membrane is reused.
Unfortunately, allowing a previously wetted crossflow membrane to dry usually results in permanent reduction of water permeability. Nevertheless, you can attempt to re-wet the membrane and use it. First, soak the membrane in a 50% alcohol solution for at least 15min (ethanol, methanol, or IPA would be acceptable). Next, install the membrane in the test cell and operate the cell with purified deionized water as though you were pre-conditioning the membrane. After about 30min, the permeate flux should stabilize to whatever rate the membrane is now capable of.
Determining which solution to use to clean a flat sheet membrane depends on the substance it is fouled with. As a general rule, you can use a caustic or oxidant solution for organic fouling and an acidic solution for inorganic causes. Please remember that different membranes polymers have different pH tolerances.

Slight change in color towards yellow/brown is completely harmless and caused by the chemicals used in the production process of the Aquaporin Inside FO membranes . This change in the color does not affect Aquaporin Inside membrane's characteristics or performance.

Yes, for flat sheet membranes that will be used with water or aqueous solutions, we recommend that you pre-condition the membranes prior to conducting your separation experiments. Pre-conditioning helps ensure that the membranes perform as expected. Also, pre-conditioning removes preservatives and other residuals from the membranes. Purified deionized water is used to pre-condition the membranes. For all flat sheet membranes except the forward osmosis (FO) membranes, install the membrane in the test cell and apply the purified deionized water feed at the normal operating rate and pressure for the membrane. Allow the system to operate with the purified deionized water feed until the permeate flux stabilizes at an expected value. You can now replace the purified deionized water feed with your feed solution and begin your experiments.

The active side of the membrane (as indicated by the packaging) should be facing the feed solution.

Most membrane manufacturers recommend CFVs of 5 to 35cm/s for their spiral wound membrane elements. The flat sheet membranes can be operated in this range to simulate use in such elements. Additionally, the flat sheet membranes may be operated outside of this range by users that want to examine the relationship between CVF and fouling and membrane performance in their applications.
Cross flow velocity (CFV) is the linear velocity of the feed flow tangential to the membrane surface and is typically reported in m/sec or ft/sec. It is calculated by dividing the volumetric flow rate through the feed channel by the cross-sectional area of the feed channel. Please refer to the CFV article at Tech Tips for more information.
The recommended TMP will depend on the type of flat sheet membrane and on the application. Typically, a reasonable TMP will be the same as that noted for the permeate flux specification of the membrane. The specifications for any of the flat sheet membranes can be easily found on our website by clicking the “application/specification” tab on the product web page and scrolling down as necessary. Please contact us at [email protected] if you need additional assistance.
These membrane sizes are intended for use in the bench-scale crossflow test cells offered by Sterlitech. Please see the list of flat sheet membranes we offer and their dimensions: HP4750 Stirred Cell: 47 mm (1.85") discs, CF016 cell: 58 x 75 mm (2.26 x 2.95") coupons, CF042 cell: 56 x 115 mm (2.20 x 4.53") coupons, Sepa CF cell: 140 x 190 mm (5.51 x 7.48") coupons, CF047 circular cell: 47 mm discs, CF090 circular cell: 90 mm discs

You can estimate the rejection of forward osmosis membranes by using the following formula, where Cp is the concentration of solute in the permeate and Cf is the concentration of solute in the feed:
R= 1-(Cp/Cf)

Ask An Expert

As an industry leader focused in unique micro and sub-micron filtration products, our goal is to support our customers by keeping them at the forefront of their industries. We're here to help with any filtration questions you might have so you can transform your ideas into reality, and tackle those big science challenges. Feel free to reach out using the form below, our experts are ready to serve.
Copyright © 2026 Sterlitech Corporation All Rights Reserved.
Terms and Conditions | Privacy Policy