Filtration Resources

As part of our goal to enable researchers, Sterlitech carries a comprehensive assortment of membranes for use in bench-scale filtration systems (such as our HP4750, CF016, CF042, and Sepa CF cells). We offer membrane filter sheets designed for use in reverse osmosis, nanofiltration, ultrafiltration, microfiltration, and forward osmosis applications.  Additionally, we offer membranes for membrane distillation and where this is a need for chemically resistant membranes.

We are continually adding new products to our offerings; please visit the Flat

Legalization and the increasing demand for cannabis products have transformed technology used for extracts from simple to sophisticated in recent years. 

Extract processing typically begins with a solvent wash, followed by winterization and/or filtration to concentrate the active compounds and to remove large impurities such as waxes. A final purification step aims to remove chlorophyll, thus producing the desirable amber concentrate, ready to be further modified into valuable end products. This time and labor consuming process can further be simplified and improved. Removing color while preserving THC and CBD’s still remains a challenge.

Our solution for addressing both needs:

According to Evonik Corporation’s recent presentation, Organic Solvent Nanofiltration (OSN) Duramem^TM Membranes may not only simplify the

Sterlitech offers a broad variety of polyamide active layer thin film composite (TFC) reverse osmosis (RO) and nanofiltration (NF) flat sheet membranes.  It is quite common for these membranes to have visually apparent surface imperfections, most notably small dark spots, resulting from the manufacturing process.  Some inexperienced users may be concerned that these spots are mold or some other contamination, however, these are almost always the result of trace residual amounts of polyamide monomer that have reacted to ambient light.  While not visually appealing, you can rest assured that these spots are not a source of contamination and do not affect membrane performance.  Users should resist the urge to clean these spots as rubbing the membrane surface will cause damage.

Other types of common surface imperfections are light areas or spots that become visually apparent when observing membranes

If the goal of your vacuum filtration is purification using a membrane with an absolute pore size, Sterlitech recommends utilizing glass filter holder assemblies. Compared to Buchner funnels, these systems create a tight seal to prevent liquid bypass around the membrane. Without this seal, the benefit of a highly retentive membrane disappears.

It is typical to experience some leaking in many vacuum filtration applications, but minimizing this will significantly improve yield. There are a few ways to ensure optimal sealing, including proper set-up of the apparatus and running under the manufacturer’s recommended conditions.

To illustrate this, we ran trial liquid filtration on our 150 mm assembly with improper gasket placement (below support)

What is membrane preconditioning and why is it recommended to precondition new flat sheet or spiral wound membranes prior to use?

Membrane preconditioning is a filtration step using deionized water as feed solution and is typically performed at a pressure equal to or higher than the anticipated testing pressure. During this process membrane pores are wetted and the membrane structure may go through compaction or swelling, affecting both the permeate flux and the rejection values. Preconditioning will help ensure that the membrane performs according to the specs provided by the manufacturer.

Are FO membranes preconditioned the same way?

Aquaporin Inside™  flat sheet FO membranes should be soaked in DI water for

When introducing a new control fluid to hydraulic systems, it is important to ensure that the new liquid or mixture is of equal or superior quality to the previous fluid. If the new mixture is incompatible, precipitate may form and result in an overall inferior fluid. This can speed up clogging or damage the system.

When a manufacturer of construction machinery releases a new line of bulldozers or backhoes, they may consider using a lower cost alternative fluid mixture. If the machines take a different fluid than previous versions, it may be beneficial to switch over to a single fluid for the entire fleet. The compatibility of the new fluid with the old can be assessed for quality to decide if the change is warranted.

Similarly, an automotive die-casting company may want to convert from a water glycol hydraulic fluid to a polyol-ester fluid for higher performance and lower environmental impact on their cutting machinery. Examining the new fluid’s compatibility can

Researchers frequently ask, “what is the purpose of the shims and spacers for use with the membrane test cells, and do I need them?” Curious to know more? In response to this common question Sterlitech’s own Sepideh Jankhah explores this topic in her recently published Paper, which investigates the hydrodynamic conditions in a bench-scale membrane flow-cell (CF042 Cell). It looks at the ways in which parameters such as the feed crossflow velocity, geometry of the cell, and feed spacers, affect system hydrodynamics.

Last month we examined filter selection strategies for maximizing service life in continuous use applications.  In this 3^rd installment, we will examine the use of prefilters to extend service life.

Clarifying liquids with high levels of suspended solids is challenging, especially for applications requiring submicron filtration.  In these applications, filter users who experience frustratingly short service life should consider using prefilters.  A suitable prefilter will reduce the particle fouling of the final filter and, consequently, the combination will have better total throughput than the final filter alone.

In general, the amount of particulate a filter can accommodate before becoming clogged is related to its pore size rating.  As filter pore sizes decrease, the smaller pores have reduced void volumes and reduced capacity for holding particulate.  Conversely, as filter pore sizes increase, the larger pores have increased void

Last month, we described the considerations associated with predicting filter service life and how total throughput can be estimated through experimentation.  In this second installment, we will examine four filter selection strategies for maximizing service life in continuous-use applications. These aspects consider chemical compatibility, temperature, binding characteristics, and pore size.

At the most basic level, selecting filters that are compatible with the application’s chemistry is the key to success.  Filters with poor compatibility to the liquid being filtered typically fail well before normal clogging due to limitations associated with filter deterioration.  The filter chosen must exhibit both good chemical compatibility with the fluid and good physical compatibility with the operating conditions.  PTFE and polyether ether ketone (PEEK

For consumers using disk, syringe, and capsule filters it is a common FAQ: How long will my filter last? Or, to put it another way: How much fluid can I expect to pass through my filter before it clogs? This seems to be a simple and reasonable question for a filter consumer: Would any of us purchase a product without an understanding of its service life? However, this apparently simple question is deceivingly complex as a multitude of factors influence filter service life. Service life can be defined as the total volume of fluid that is passed through a normal flow filter until it becomes clogged; this is commonly referred to as total throughput. It is nearly impossible to predict total throughput, even with a good understanding of the application. So, as a filter manufacturer, how would we suggest approaching this challenge?

Most laboratory filtration applications involve limited