Page 34 - Blog

When selecting the right membrane for a microfiltration application, one of the most important factors to consider is membrane wettability. While hydrophobic membrane filters are ideal for air and gas filtration, they are not suitable for filtering aqueous solutions. Hydrophilic membrane filters, on the other hand, are commonly used for clarification and sterilization of water-based fluids but are not typically used for venting applications.

To conceptualize the forces contributing to membrane wettability, you can start by thinking of a water drop on a material’s surface.

(Yuan & Lee, 2013)

When the electrostatic attraction between the water molecules and the material is greater than the attraction between the water molecules themselves, the water drop will spread out. Here, the instantaneous angle between the edge of the drop and the surface, the water contact angle, will be <90°. Such materials are called hydrophilic, literally meaning “water loving”. The more hydrophilic

Sterlitech has recently discontinued sale of the MS7-Pro Analog Magnetic Stirrer from Scilogex. For fans of the MS7 model, we recommend the MS7-H550-Pro Hotplate Stirrer. 

If you're looking for a comparable stirrer (and don't need the heating function), we still have a selection to choose from in the Magnetic Stirrers & Hotplates section of our website. We are happy to assist with finding the right stir plate for your lab - please contact us with any questions!

In a joint effort to address our customers’ growing need for a Forward Osmosis (FO) membrane module that has a larger membrane active area compared to our flat sheet FO modules, but has a smaller membrane active area than the Aquaporin Inside HFFO2 module, Sterlitech is now pleased to announce the launch of Aquaporin Inside HFFO06 hollow fiber FO membrane module.

Aquaporin Inside HFFO06 hollow fiber FO membrane module has a 0.6 m² membrane active area and can be operated with lower volumes of feed and draw solutions compared to the Aquaporin Inside HFFO2 hollow fiber FO membrane module with a 2.3 m² membrane active area, making this a perfect fit for lab scale testing and small-scale production.

Membrane active layer in these HF membranes is composed of a thin film composite with integrated aquaporin proteins. Use of HF membranes allows higher packing density (i.e. higher membrane active area) in the module.

Applications of Aquaporin Inside HFFO06 hollow fiber FO membrane module:

• Forward

Sterlitech Kato-Katz Test Kits are designed for diagnostic use in the field. Our kit was developed in response to difficulty among research groups, control programs, and health organizations to readily source the materials needed for this testing. Field scientists utilize Kato-Katz tests to identify the presence of parasitic Soil-Transmitted Helminths (STH) eggs in fecal samples from infected patients. It can be used to diagnose individual infection and monitor disease prevalence across communities for epidemiological studies. Compared to other diagnostic methods, the Kato-Katz technique offers the benefit of sample preservation, enabling field samples to be stored for later study.¹ It complements the Sterlitech Schistosome Test Kit, which detects parasitic Schistosome worm eggs in urine.

STH worm infections affect a substantial portion of the world’s population living in warm and moist climates with limited access to clean water and sanitation services. When eggs are ingested, or hookworm

Groundwater is a vital natural resource; it provides drinking, household, and irrigation water across the country and the world. Over half of the United States population relies on groundwater as their drinking water source.¹ Unfortunately, in some geographical regions, groundwater supplies are at risk of depletion and contamination. Pollutants can originate from septic systems, landfills, underground oil and gas tanks, and various atmospheric contaminants. Emerging issues to assess in groundwater testing are the impacts of hydraulic fracturing, sea water intrusion, and microplastics accumulation.  

In the US, organizations like the US Geological Survey (USGS) sample and analyze groundwater to monitor water availability and water quality. Scientists run tests on the physical, chemical, and microbiological characteristics of groundwater sources, and use this data to monitor and forecast how these factors might be impacted by increasing human consumption and climate change.

Mixed cellulose

Sterlitech is pleased to partner with the Pasteur Paris research team, who is using our gold-coated polycarbonate and aluminum oxide membrane filters in their exciting research for this year’s International Genetically Engineered Machine (iGEM) competition. Team Pasteur’s project, called NeuronArch, seeks to improve outcomes of surgical prothesis implants.

After surgery, microbes like S. aureus can colonize implants and form surface biofilms – these rare but severe infections are hard to treat with antibiotics, and often require removal of the implant to cure completely (1). One avenue of preventing this problem is to combat biofilm accumulation. However, the NeuronArch project aims to subvert the biofilm instead of fighting it. Their goal is to coat the implant with a genetically modified lab-grown E. coli, to serve as an interface between the synthetic prosthesis and organic tissues. This controlled biofilm would work to promote neural connections while preventing colonization by

Sterlitech Glass Filter Holders are available in a variety of sizes to accommodate most filtration applications, ranging from milliliters to liters of solution. Glass filter holders are reusable, easy to clean and sterilize, and enable precise filtration. They are recommended for use with polymeric Membrane Disc Filters to perform particulate collection and fluid filtration. Applying vacuum reduces process time compared to gravity flow.

Compared to other vacuum filter holders suited for coarse filtration (i.e. Buchner funnels), Glass Filter Holders form a tight seal with the membrane to ensure all fluid passes through its pores.

A typical holder apparatus consists of:

• glass base
• membrane support (glass frit, stainless steel, or PTFE)
• glass funnel
• rubber adaptor
• aluminum clamp

Glass frit supports are ideal for filtering acidic solutions, while stainless steel support screens offer the faster flow rate with viscous solutions. PTFE-coated supports provide the best of both worlds. Many

Have you noticed how your membrane performance is affected by the operating conditions? Depending on the type of membrane separation process, operating conditions may include hydraulic pressure, osmotic pressure, temperature and feed cross flow velocity. Operating conditions can affect both permeate flux and solute rejection. Among these parameters, permeate flux is very sensitive to the feed temperature. Permeate flux increases as the feed temperature increases. This is mainly due to the decrease of feed viscosity with an increase in the feed temperature.  More specifically permeate flux typically increases as temperature increases in a linear relationship with viscosity as described below (1):

In this equation, J is the permeate flux through the membrane,  m is the feed viscosity, J₀ is the permeate flux at a reference temperature, and μ₀ is the viscosity at the same reference temperature. J₀ and µ₀ are constants and are ordinarily defined by the membrane

Sterlitech offers bench-scale membrane test cells that can be used for a variety of filtration applications. The Developer series are the largest cells used with Sepa size flat sheet membrane coupons, i.e. membrane active area of 140 cm²/24 in². The Explorer series is used with CF042 size flat sheet membranes, i.e. membrane active area of 42 cm²/6.5 in². The Innovator series are the smallest cells used with CF016 size flat sheet membranes, i.e. membrane active area of 20.6 cm²/3.2 in². All three series of cells are available in a  variety of material of construction, including: Stainless steel, Hastelloy, Delrin, PTFE, Acrylic.

These are available in models suited for Cross/tangential Flow, Forward Osmosis, or both processes. For Cross Flow applications, the feed solution is circulated tangentially to the membrane filter. Molecules or materials which are smaller than the membrane's molecular weight cut-off (MWCO) or porosity pass through the membrane as permeate and the remainder

Because they have similar outward appearance, it is easy to presume that the various microporous membrane filters and flat sheet membrane filters offered by Sterlitech have similar pore structures.  Some consider symmetry to be the epitome of beauty, but with respect to filtration, it’s all relative.  In reality, there is a rich variety of pore structure morphologies resulting from the techniques and materials used to manufacture the membranes.

For the microporous membrane filters, the pore structures range from the essentially two-dimensional screen-like structures of the polycarbonate and polyester track-etch membranes, to the node and tendril structures of the expanded PTFE membranes, to the entangled nanofiber structure of the polyacrylonitrile (PAN) membrane, and to the convoluted lacey foam-like structures of the solvent cast membranes such as cellulose acetate (CA).

Some solvent cast microporous membranes, such as Nylon, have essentially symmetric pore structures where the