Please send us an email or complete this form if you would like a hard copy of our new catalog!

Here is a link to the web based catalog - 2016 Catalog!

Nanostone flat sheet membranes are being discontinued by the manufacturer. Limited quantities of Nanostone flat sheet membranes is available at the moment, for more information or if you need assistance finding a suitable replacement product, please contact Sterlitech at sales@sterlitech.com.

Nanostone™ Discontinued Nanofiltration Membranes

Nanostone™ Discontinued Ultrafiltration Membranes

Nanostone™ Discontinued Microfiltration Membranes

 
To browse our complete selection of flat sheet membranes or to place an order with us, click here.

North American Membrane Society (NAMS) annual meeting was held in Bellevue, WA, during the last week of May. Due to the great collective interest shown by the membrane research community, only 40% of the abstracts submitted to the meeting could be accepted for podium presentation, which made up to about 140 talks! In addition, about 140 posters were presented in 5 parallel poster sessions. As a comparison, there were about 144 talks and 160 posters in NAMS 2015 meeting at Boston. Conference attendees were primarily researchers from industry and academia.

Research was focused on the following topics:

• Membrane Distillation (MD)
• Biomimetic membranes
• Desalination and potable water production
• Gas separation
• Design and processing of polymeric and inorganic membranes
• Designs and processing of composite and hybrid membranes
• Novel membrane materials

Other topics of interest included:

• Pervaporation
• Membrane transport: theory and characterization tools
• Water treatment, reclamation, and reuse
• Energy applications (fuel cells, batteries, buildings)

Sterlitech was present at NAMS 2016. Our Product Manager, Sepideh Jankhah, also presented the results of her most recent research; title of her talk was “How Do Hydrodynamic Conditions in Spiral Wound Membrane Elements Translate into Shear Forces Effective for Fouling Control at Membrane Surface?” Her research was conducted in a CF042 cross flow filtration cell using feed spacers commonly used in commercial spiral wound elements.

For more information about the meeting please visit: membranes.org

They’re back! Last year, Sterlitech discontinued offering the economical Rocker vacuum pump series due to supply issues. We’re happy to report the issues are worked out and they’re now back to our product lineup! These pumps complement a family of durable and economical lab products designed to help your filtration needs.

The Rocker pumps include the models 300, 400, and 600 in both 110V/60Hz and 220V/50Hz units. These pumps are outstanding economical resources for wide ranging lab applications based on simple aqueous solutions. In addition to the Rocker pumps, we also offer the Rocker repair kits, when needed, to rebuild the pumps after they go past the extra mile.

The Rocker pumps are now online at Sterlitech.com and Amazon.com, but you can always contact us directly for a quote or tech support if needed prior to ordering. If your requirements are for more chemically harsh or demanding environments, consider our heavier duty TLD or Gast vacuum pumps; available here.

PCTE Membrane Filter

Sterlitech’s polycarbonate and polyester track-etch membrane filters are a unique product that find use in numerous applications. They possess clean cylindrical pores that transverse the membrane surface from one side to the other. As a result of this unique feature, the pore density must be much lower compared to almost all other standard thin-film membranes such as Nylon, PTFE, PVDF, and more. Particulates either pass through the pores in track-etch filters, or remain on the surface. Almost never do they become embedded within the pore’s interior. But what happens when these filters are needed for your project and the particles being filtered occlude the opening of the pores? This effect is called pore blinding; and you may ask “But what can be done?”

Fear not brave scientist! In most applications, the track-etch filters will work fine on their own. But if a difficult particulate is clogging up your filter too soon, consider use of our Polyester Drain Discs. These discs act as a pre-filter to prevent the dreaded pore blinding from stopping your filtration run and allow you to stand head and shoulders above your competitors. The drain discs keep larger material off the pores and out of the way, so the filters can do their job. In addition, the drain discs also act as a membrane support when using two track-etch filters in series (one on top of the other) for a step-wise separation method. These handy discs are available in several different pore sizes to pair with the track-etch filters.

Need a little help in getting the blinders off the track-etch filters? Please contact Sterlitech’s sales team for help at sales@sterlitech.com.

Sterlitech teamed up with Senior Engineering Students at California State Polytechnic University, Pomona (Cal Poly Pomona) to evaluate the design of a tangential flow Air Gap Membrane Distillation (AGMD) test cell. Membrane Distillation (MD) is a thermally driven membrane separation technique used for desalination. In this process, the driving force is the difference in the vapor pressure on both sides of the membrane, where permeate travels through a hydrophobic membrane in a vapor phase. Advantages of MD process over conventional distillation or pressure driven separation processes are:

• Low Operating Pressures
• Low Operating Temperatures
• Less Susceptibility to Fouling

These all translate to lower energy requirements that make MD an energy efficient separation process.

Scope of the Project

A bench-scale tangential flow test cell is configured in this project where feed solution is circulated tangentially to the membrane in the feed channel on one side and the coolant solution is circulated tangentially to a cold plate in the cooling channel on the other side. There is an air gap between the membrane and the cold plate. The thickness of the air gap can be varied. In this configuration, permeate travels through the membrane and is collected at the bottom of the air gap. Objectives of this project included the design of the air gap configuration, as well as evaluating the effect of air gap thickness and operating temperatures on the permeate flux and permeate quality.

Results and Final Presentation

Spacer plates were designed to create an air gap of 3/16 in (4.76 mm) and a membrane active area of 7.068 in² (179.5 mm²) in the cell. Permeate flux measured with this configuration was within the range expected for the membranes and operating conditions tested in this project. Permeate was collected at the bottom of the air gap. Feed temperature and flow rate both proved to effect the permeate flux and quality. The results obtained in the course of this project were presented at the Spring Green Expo of 2016 held by The Metropolitan Water District of Southern California. Spring Green Expo highlights sustainability and water related projects created by Southern California college students.

If you have additional questions or would like to learn about the AGMD cell or membranes recommended for the MD process, please contact Sterlitech.

Congratulations to the group members at Cal Poly Pomona for delivering the project and presenting at the Spring Green Expo!

Pictured Right: Senior Design Project Group members at Spring Green Expo 2016. N. Espinoza, B. Elgawly, and M.Price.

Water, oils, and solvents sometimes need to be filtered. But when you see filters labeled as hydrophilic, hydrophobic, and now oleophobic; what does all this mean?  Sterlitech currently offers membrane disc and sheet filters in 10 different polymer types and 4 inorganic filters. 2 of the polymer types are subdivided into 4 subgroups based on surface chemistry alone.

Filters listed as hydrophilic, which has its origins in the Greek language and means water (hydro) loving (philos), love to get wet! Hydrophilic filters will easily pass water or water-based solutions such as dairy, river water, seawater, cell culture solutions, buffers, beverages, and many more. The filters best suited to handle these solutions are silver, ceramic, glass fiber, cellulose acetate, mixed cellulose ester (nitrocellulose), nylon, polyester, polycarbonate (PVP-treated), polyacrylonitrile (PAN), and PVDF. They can be used for almost any application that needs particle removal, clarification, cell harvesting, sterile filtration, or prefiltration.

In contrast, hydrophobic filters, water (hydro) fear/hatred (phobia), take a different approach. These filters will not allow water to easily pass due to their surface chemistry, water-based fluids will bead up on their surface. Sterlitech’s current line of hydrophobic filters are the PVP-free polycarbonate, polypropylene, and PTFE. These filters will naturally repel water and most water-based solutions, but oils and most solvents will easily pass right through. This group of filters often find use in venting applications where air can pass through but water should remain behind, such as cell culture flasks, environmental sensors, acoustic devices, and fluid degassers.

So what is an oleophobic filter? These filters are quite unique and limited (at present) to our line of Aspire laminated PTFE filters. The surface chemistry of these filters repels water-based and solvent/oil-based liquids. They might be more aptly named omniphobic filters because they will repel just about anything! Fuels, alcohols, solvents, water, and nearly everything else will just bead up on their surface. These membranes find use in specialty venting applications that might see splashing from oils, solvents, or detergent-based aqueous solutions, such as electrical transformers, machined parts washing stations, and solvent/water mixtures.

While all of the “phobic” membranes will repel something, this repulsive force can usually be overcome with the application of sufficient pressure. So if the surface chemistry of a membrane might have an effect on your process or experiment, contact one of our knowledgeable sales reps at Sterlitech for guidance on choosing the best material or to answer questions on our membrane filters.

Q: What is Cross Flow Velocity?

A: Cross flow velocity (CFV) is the linear velocity of the flow tangential to the membrane surface and is reported in [m/sec] or [ft/sec]. CFV affects fouling rate and formation of concentration polarization at membrane surface and is calculated by dividing the volumetric flow rate [lpm or gpm] in the flow channel by the cross sectional area [m² or ft²] of the flow channel.

Q: How is CFV calculated in Sterlitech’s bench-scale test cells?

A: Example: Calculate CFV in the CF042 cell

Flow channel cross sectional area: 0.23 x 3.92 cm

Flow rate: 1 l/min = 1/60000 m³/s

CVF = (1/60000 m³/s) = 0.18 m/s
         ------------------------
       (0.0023 x 0.0392 m)

Q: How is CFV calculated when shims or feed spacers are inserted in the flow channel?

A: Adding shims to the flow channel reduces the depth of the channel. E.g. if the channel depth is 0.23 cm, inserting a shim with a thickness of 0.05 cm reduces the flow channel depth to 0.23 - (0.05) = 0.18 cm. CFV is then calculated by dividing the volumetric flow rate in the flow channel by the reduced cross sectional area of the channel.

Adding feed spacers to the flow channel further reduces the channel cross sectional area. Effective cross sectional area depends on the spacer thickness and spacer’s percentage of open area.

You can find commercially available Polypropylene and PTFE feed spacers with a wide range of thickness and percentage of open area on our website for Sepa CF, CF042, and CF016 test cells.

Please contact Sterlitech at sales@sterlitech.com for more information about calculating CFV or if you are interested in learning more about the shims and feed spacers Sterlitech offers at the moment.