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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

Sterlitech is introducing flat sheet membranes from Fluid Technology Solutions to expand our line of Forward Osmosis membrane products. The FTSH2O™ flat sheet membranes are constructed from low-fouling cellulose triacetate (CTA) material. They also present the benefit of being able to backwash to restore membrane performance.

FTSH2O™ FO membranes are ideal for applications where the feed stream contains high levels of suspended solids or high salinity. Use of FO membranes enables the treatment of these feed streams using osmotic pressure, therefore eliminating the need for the extensive pre-treatment and high hydraulic pressures involved in pressure-driven treatment processes. This results in both lower capital and operating expenditure for the filtration system.

These new membrane additions are available in large sheet format, as well as in precut coupons for use in the Sepa, CF042 and CF016 Forward Osmosis filtration cells.

Our full selection of Forward Osmosis membranes can be found

Water molecules are ubiquitous, vital, and may have the world’s most well-known chemical formula (H₂O). The properties of water are quite unique; its solid state is less dense than its liquid state, raising pressure lowers its melting point, and it exists as a liquid at room temperature despite low molecular mass. Even more unique is the water molecule’s ability to exist as two distinct nuclear configurations called spin isomers.

The two spin isomers of water molecules differ based on the direction of the nuclear spin of the two hydrogen nuclei. If the two hydrogen nuclei have parallel spins, the molecule is known as ortho-water. If the two hydrogen nuclei have opposite spins, the molecule is known as para-water. Water at room temperature always contains a mix of these two spin isomers and, until recently, it has been nearly impossible to study them separately.

Now a study co-authored by Stefan Willitsch at the University of Basel has successfully isolated the two forms of water and found

The National Association of Scientific Materials Managers (NAOSMM) will be holding its 45^th Annual Conference and Trade Show , July 22-27^th in Spokane, Washington - just over the mountains from Sterlitech. We are excited to participate in this trade show for the 5^th consecutive year and hope to meet with attendees at our booth, #22! We’re also looking forward to co-sponsoring the Tuesday Evening Out event at the show, as part of the Independent Laboratory Distributors Association (ILDA).

This conference provides an opportunity for its over 500 members in the scientific industry to discuss current trends and issues, participate in seminars and workshops, and preview new products from vendors. NAOSMM’s members range from teaching, academic, research and industrial fields. We’re looking forward to seeing you there!

Our new Convertible Skid system is specifically designed as a high-pressure system for pressure driven membrane filtration (such as Reverse Osmosis) that can be conveniently converted to perform as either an osmotically driven (such as Forward Osmosis) or a temperature driven process (such as Membrane Distillation) without the need for any additional parts or equipment. This unique capability creates versatility for both industry and academia where research priorities evolve over time.

Features and benefits of the Convertible skid:

• Designed to operate at high and low pressures
• Convertible to an osmotically driven or temperature driven process
• Customizable for compatibility with harsh or corrosive chemicals
• Available in both digital and analog options

The skid is modular and can be custom designed for use with a combination of membrane test cell types and flow configurations. Applications include: processing of water and wastewater, chemicals, pharmaceuticals, removing organic and heavy

A recent study from the World Health Organization (WHO) found that 9 of 10 people live in environments that expose them daily to elevated levels of air pollution.¹ This contributes to staggering 7 million deaths a year from related diseases.1The danger is largely posed by fine particles less than 10 (PM₁₀) and 2.5 (PM_2.5) micrometers which may pass through the nose and extend beyond the heart and lungs to the brain and cause health problems; these can also affect the environment.¹ US Environmental Protection Agency (EPA) Method 201A is commonly used to monitor PM₁₀, and PM_2.5 for air quality control. Air is withdrawn through two sizing cyclones, and then collected on an EPA approved PTFE membrane filter. After a sample is obtained, gravimetric analysis is used to determine the particulate mass for each size fraction. The PM_2.5 mass is determined by adding the mass of particulates captured on the PTFE filter and the ≤ 2.5 μm wash.^2,3

Sterlitech is now offering PTFE PM_2.5 membranes