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Stirred Cells

Sterlitech offers a variety of stirred cells that utilize a cross/tangential flow design for the filtration of small volumes of feed solution. The compact design and capacity is also ideal for membrane studies and characterization.

Stirred Cell Features and Benefits:

  • Tangential flow stirred cell design increases membrane life and sample throughout
  • Test small areas of membrane or small volumes of feed solution
  • Filter small volumes ranging from 10 mL to 2L
  • Options operable up to 2500 psi
  • Solvent resistant options available
 

Interested in learning how to operate our membrane process equipment?  Check out our MPD channel to watch videos now!

MaterialFeaturesApplicationsPore Size (μm)
Sterlitech HP4750 Stirred Cell For Membrane Process Development

Chemically resistant and features a low hold-up volume (1 ml)

Solutions with high levels of dissolved solids and high osmotic pressure, volatile solutions

N/A
Sterlitech HP4750X Stirred Cell For Membrane Process Development

Maximum pressure rating of 172 bar (2500 psig) at ambient temperatures, autoclavable, chemical resistant stirred cell components

Aqueous and non-aqueous solutions, volatile solutions

N/A
Polymeric Stirred Cells with Tangential Flow Design

Clear plastic reservoir allows for visual monitoring of fluid level and sample condition, tangential flow design

Desalting and concentrating proteins, enzymes, virus, and other biological samples

N/A

Frequently Asked Questions

Yes, you can use almost all microfiltration membrane disk filters  in the stirred cells. The only exception are the ceramic membrane disk filters; these are too thick to fit in the stirred cells.

You can find a diagram for a typical stirred cell system at https://www.sterlitech.com/media/wysiwyg/Manual/HP4750_Flow_Diagram.png. In addition to the stirred cell itself, the user will require a pressure source consisting of a regulated supply of compressed inert gas or air, a bleed valve for releasing the air pressure, an appropriately sized magnetic stirring plate, and a permeate collection vessel (e.g. flask or beaker) to collect the filtrate. 

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.

To pre-condition the membrane disk, install it in the stirred cell and then fill the stirred cell with purified deionized water. Initiate operation of the stirred cell at the pressure and temperature expected for the separation experiments. Allow the cell to operate until the permeate flux has stabilized at an expected value. Then release the pressure, discard any water remaining in the stirred cell, and discard the water from the permeate collection vessel. You may now proceed with your experiments by refilling the cell with the desired feed sample. At no time should the wetted membrane disk be allowed to dry.  

Yes, we offer operating manuals for the HP4750HP4750X, UHP polymeric stirred cells. You can find links to the operating manuals for the stirred cells by clicking on the “Documention/Media” tab on the stirred cell product pages.

It is important to note that membrane manufacturer’s specifications for rejection and permeate flux are usually based on testing of large area spiral wound membrane elements operating in crossflow mode using standardized feed streams and pressures. It is normal, and to be expected, that rejection and permeate flux will be different for feed streams and pressures that are not similar to the standardized test conditions. It is also normal, and to be expected, that rejection and permeate flux will have greater variability from published specifications for devices with membrane active areas that are very much smaller than spiral wound elements, such as stirred cells. Some amount of concentration buildup in the feed for stirred cells is inevitable and this may affect rejection and permeate flux.

There are some tactics that can be used to optimize rejection and permeate flow while using stirred cells. First, the membrane should be pre-conditioned using purified deionized water. Please refer to the operating manual for the pre-conditioning procedure. Second, make sure that the stir bar is turning properly and at an appropriate rate. Third, the operating pressure should correspond to the membrane manufacturer’s recommended pressure. Finally, you may want to stop your experiments while there is still some feed liquid remaining in the stirred cell to mitigate effects associated with increasing concentrations.

Yes, you may connect the permeate line directly to an instrument. However, it is important to understand that if the membrane fails or is allowed to dry, then the full feed pressure may be applied to the permeate line. If the instrument cannot withstand the feed pressure, then directly connecting the permeate line is not recommended. Alternatively, if the membrane becomes prematurely fouled (due to a high TDS or particulate loading), permeate levels may drop below detection in the HPLC inlet port.

The stirred cells are designed to accept flat sheet membranes with thickness of 350 microns or less.

The porous support disk has a nominal pore size of 20µm.  

All of the wetted surfaces are non-metallic. The UHP stirred cells have polycarbonate or acrylic barrels, polyacetal endcaps and stir rod, PTFE stir bar, polypropylene support screen, and silicone o-rings. The UHP-K stirred cells have polysulfone wetted components and silicone o-rings.  

The maximum operating pressure for the UHP stirred cells is 73psi (5.0bar). However, the nominal safety relief pressure for the vent valve is 63psi (4.3bar).

The maximum operating pressure for the UHP-K polysulfone stirred cells is 71psi (4.9bar). However, the nominal safety relief pressure for the vent valve is 57psi (3.9bar).

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.