bench scale

Unfortunately, Koch has discontinued the ultrafiltration membrane HFM-100. The HFM-180 is a viable alternative to the 100 and 116, it is PVDF with a separation range of 100,000. The good news is we will be adding 4 new membranes in the next couple of weeks.

Compare the specifications for all of our UF membrane designations here.

Here's a short demonstration with Kristina explaining how to cut a Sepa CF Membrane Filter using a steel ruled die:

Is there a product or process video demonstration that you'd like to see? Let us know in the comments!

One of the most promising new frontiers in filtration technology involves infusing different membrane types with nanomaterials in order to improve performance or to pass along certain material attributes. Here we will look into one prominent example from recent years, the incorporation of carbon nanotubes (CNTs) into ultrafiltration membranes used in water treatment. We’ll also look at how our stirred cells have aided in this specialized membrane manufacturing process.

First off, what is there to gain by using CNT’s to manufacture water treatment membranes? While scientists have identified several potential advantages for CNT implementation, since the process is still in the R&D phase they have not necessarily been proven in all cases. One key possible benefit is that membranes made with these materials would be much stronger than traditional membranes, thus reducing instances of membrane breakage and fouling, two problems that contribute significantly to high maintenance costs in water treatment. Another unique advantage is that CNTs have antibacterial properties that may reduce biofilm formation and therefore prevent or limit biofouling. Lastly, the process of manufacturing ultrafiltration membranes with CNTs allows the producer to chemically modify the membrane surface which can further reduce fouling by tailoring the membrane for specific organic solutes.

As with standard membrane manufacturing processes, the stirred cell is an ideal piece of equipment for establishing the permeability of the test membranes. For this particular study on the effectiveness of polysulfone ultrafiltration membranes manufactured with CNTs, the cell (an HP4750 in this case) was set to perform dead-end filtration with ultrapure water at 38 bars of pressure (about 551 psi).

The HP4750 Stirred Cell

In order to determine permeability, the HP4750 was directly connected to the pressure regulator of the compressed air tank. Each membrane was compacted at 38 bars until the flow rate was stable (minimum of 30 minutes). Then the flow rate was measured by weighing the permeate as a function of the pressure applied (between 5 and 35 bars). To confirm the results, this test was performed in triplicate.

Permeability is an important test characteristic for determining the membrane’s susceptibility to fouling and its overall efficiency. In the study cited here, researchers found no statistically significant difference in permeability between CNT and non-CNT amended membranes. These findings supported their conclusion that their process for grafting CNTs onto membranes was ineffective. In the conclusion the authors note that because the CNTs only partially dispersed in the host material that they were prevented from taking on the mechanical properties of the CNTs.

While this particular study did not yield the desired results, new methods of integrating nanomaterials onto membranes are constantly being explored and hopefully it’s only a matter of time until these superior membranes become available.

Visit here to read the full study:
http://cohesion.rice.edu/engineering/pedroalvarez/emplibrary/85.pdf

Starting this week you can power your process filtration units and membrane test cells with the full line of flat sheet membranes from TriSep Corporation! These membrane elements are designed to provide premium efficiency in water treatment applications.

What is especially great about this news is that now you can get these membranes in precut sizes to fit the CF042, Sepa CF, and HP4750 membrane test cell (individual sheets are available too)! Performing desalination and wastewater purification just got a lot easier…

See the full announcement here.

The Department of Energy and Savannah River National Laboratory recently published a study regarding their efforts to improve performance on cross-flow filtration for high level waste treatment. Even though the waste being treated in this case is actually radioactive material from nuclear power plants, the process they describe, along with the issues they raise and recommendations for improvement, can be applied to the more common uses for cross-flow filtration.

The stated goal of this DOE research was to improve filter fluxes in their existing cross-flow equipment, a common request of many customers. The study examines the problem of increasing cross-flow filtration efficiency from a number of different approaches: Backpulsing, cake development, scouring, and cleaning were all taken into consideration.

At the end of the study SRNL was able to draw some conclusions to take into consideration when evaluating your own setup.

• Higher solids concentration presents a greater challenge to filtration.
• The presence of a filter cake can improve the solids separation by an order of magnitude as determined by turbidity.
• Scouring a filter without cleaning will lead to improved filter performance.
• Filtrate flux decline is reversible when the concentration of the filtering slurry drops and the filter is scoured.

You can read the full report here to see a detailed description of their setup and complete results.

This week the New York Times gave a very nice shout out to one of our customers, Ion Torrent, and their CEO, Dr. Jonathan Rothberg. Ion Torrent is increasing the prevalence of genetic sequencing by developing smaller and more affordable machines. The article compares what they are doing with genetic equipment to what Steve Jobs did with the personal computer – so clearly Ion Torrent has some big, ambitious plans.

They’ve been using our bench scale products for a little while now, and it’s nice to know they are going to good use. My favorite part, “If somebody is to get the Nobel Prize for next-generation sequencing, it should be Jonathan.”

Just make sure to wave to us from Stockholm!

Read the complete article here.

One of the biggest issues for crossflow filtration is figuring out how to control the loss of permeate flux in the process. Whether using reverse osmosis (RO), ultrafiltration (UF), or microfiltration (MF), the loss due to polarization and membrane fouling prevents many potential users in the biological or chemical processing fields from adopting this method.

If you are using crossflow filtration, or considering using it, and fear the effects of permeate loss, then you may want to consider this technique courtesy of North Carolina A&T University and the U.S. National Energy Technology Laboratory. Their study (see here) produced drastically improved results by implementing flow reversal to enhance the membrane flux.

They found that by periodically reversing the flow direction of the feed stream at the membrane surface results in prevention and mitigation of membrane fouling. This particular study conducted experiments with bovine serum albumin, Detran T-70, and apple juice. We’d love to hear from any of you in the field that may have tried this technique to see how it worked out!