Filtration

In order to keep costs down many companies perform in-house testing on the lubricating oil and hydraulic fluid in their machinery to monitor it for particulate contamination. While most facilities can’t match the detailed analysis that an oil analysis laboratory can provide, there are some commercially available kits out there that allow users to get a good idea about the quality of their industrial fluids instantly. This process is commonly known as a “patch test” and it includes the use of MCE filters to collect and isolate debris for evaluation (“patches” is a colloquial term for filters in the oil analysis industry).

The ISO recognizes the important link between contaminated oils and component life and has published a cleanliness code as well as various standard methods, such as ISO 4406:1999, that testers can reference to determine how much particulate is acceptable. For the filtration aspect, our customers often use the sterile MCE membrane filters, which are individually wrapped and are actually less expensive than their non-sterile counterparts. Pore sizes and diameters vary by user; for a pore size larger than 1.2 micron a non-sterile MCE filter should be used (non-sterile MCE filters are available up to 8.0 microns).

Clients performing this analysis can purchase the necessary components separately, but they often purchase a pre-assembled patch test kit which may include the filters, sample bottles, forceps, filter holder, a vacuum pump, and a visual correlation chart to compare the results to the approximate ISO cleanliness code. The actual components of the patch test kit, as well as the filter specifications, are likely to vary by provider so be sure to check out what is included in yours before ordering.

Consult this article from Machinery Lubrication for more information on patch testing.
Read ISO 4406:1999
Read “Decoding the ISO Cleanliness Code”

The Toxicity Characteristic Leaching Procedure as described in EPA Method 1311 is designed to determine the mobility of organic and inorganic analytes present in different forms of waste. This procedure involves extracting and filtering waste samples using specific types of glass fiber filters and extraction vessels. When following this procedure, there are two kinds of vessel that can be used to extract samples for analysis, the bottle extraction vessel and the zero-headspace extraction vessel. Which type of vessel you use depends on the volatility of the analyte being sampled. Nonvolatile analytes can be tested using a bottle extraction vessel, while the zero-headspace extraction vessel must be used when testing for the mobility of volatile analytes. Examples of volatile analytes include: acetone, benzene, methanol, toluene, and vinyl chloride.

The EPA Method specifies that the filter for both liquid and solid waste (the latter is filtered after solid phase extraction) be a 0.6 to 0.8 micron glass fiber filter. The TCLP grade filters, which are designed precisely to meet the requirements of EPA Method 1311, feature a 0.7 micron pore size and have been acid treated and rinsed with deionized water at multiple stages to handle volatile analytes. When using these filters in conjunction with a zero-headspace extraction vessel, the EPA Method dictates that the TCLP filter should have a diameter between 90 mm and 110 mm (TCLP-2 and TCLP-3 meet this specification).

For more information on the Toxicity Characteristic Leaching Procedure, consult the complete text of EPA Method 1311 here.

A new report from Lux Research indicates that the worldwide market for membranes is expected to nearly double by 2020, from $1.5 billion to $2.8 billion (USD). One of the main reasons for this growth is advancements in membrane technology which will increase their utility. Improvements in fouling resistance and chemical tolerance open the door for membranes to be used in applications that they couldn’t perform before, such as industrial water treatment.

Another reason for optimism in the membrane industry is the continued market strength in the industries that purchase membranes. The food & beverage, pharmaceutical, desalination, environmental, and biotechnology sectors all commonly use membranes in their processes and are all expected to continue growing in the United States and around the world.

What do you think? Do you see yourself using membranes more often 10 years from now?

Also visit Filtration + Separation for more information on this report.

This month’s Laboratory Equipment magazine features a reader survey on liquid handling devices that shows just how common these items are in the lab. In fact, 91% of the respondents indicated that they are using a liquid handling system, and about 75% are using their equipment at least several times per week.

The most commonly used devices are pipets (75%) and pipet tips (70%), followed closely by syringes (68%) and then filters (67%). Less popular items include flow controllers (16%) and liquid level meters (10%). Overall, 80% of respondents said that they are completely or mostly satisfied with their equipment. Hopefully that group includes our customers…

The uses for liquid handling devices are spread out across a range of applications without any dominant focus. The most frequent applications are basic research (36%) and sample preparation (34%). Less common answers include wastewater (16%), pharmaceutical  (16%), and water analysis (20%).

Click on either of the charts below to enlarge.

Biogas, a form of renewable energy this is produced through, among other things, animal and human waste (hey, it’s not like you were using it) is one of several developing energy sources whose proponents are exploring membrane separation techniques to improve their purification process. A recent study published in the “Applied Chemistry – A Journal of the Society of German Chemists” experimented with a new method of membrane separation called the “condensing-liquid membrane” (or CLM) in an effort to enrich raw biogas, which typically contains between 50-80% methane, to natural gas quality (at least 95% methane content), with favorable results.

Common membrane materials like Cellulose Acetate and Polyimide have been tried for this application with some success, but the problem is that they can be ruined by the aggressive gases that are present in raw biogas, such as carbon dioxide and hydrogen sulfide. The CLM is a liquid (water in this case) layer that condenses on a porous hydrophilic membrane which then gets regenerated to allow for continuous operation. This support, made from Teflon, gathers water vapor from the biogas on the feed side of the membrane and is partially removed from the permeate side by nitrogen gas, thus allowing for separation to occur in one step as the water is constantly refreshed. One of the more brilliant aspects of the CLM method is that the presence of water in biogas, usually regarded as a disadvantage, suddenly becomes a key component in the process.

Since the membranes are being preserved and not destroyed, the potential exists for this process to be a cost-efficient method of purifying biogas in the future. Researchers will continue to investigate the CLM method in order to find the optimal conditions that will make it even more efficient.

Visit here to read the full report “Effective Purification of Biogas by a Condensing-Liquid Membrane.”

To learn more about biogas, try this site from Alternative Fuels and Advanced Vehicles Data Center and the U.S. Dept. of Energy.

How does a biogas plant work? Watch this animated video to get an idea.

Quartz Fiber Filters for High Temp. Needs

This week we added another new item to our catalog - Quartz Fiber Filters. These filters are especially useful for high temperature filtration applications since they can withstand temperatures over 500°C.

Other nice things about these filters include their indefinite storage life and their high chemical resistance. Right now we have grades QR100 and QR200 available in diameters ranging from 21mm to 150mm.

Two weeks ago I had the opportunity to mix business with pleasure during an ACS sponsored event at a local chocolate maker. Based out of Seattle, WA, Theo Chocolates, appropriately named after the chocolate bean bearing tree Theobroma cacao, is the only bean-to-bar, organic, fair trade chocolate factory in the USA. After a delicious round of tastings and an insightful tour of the production line, COO Andy McShea gave an interesting lecture on all things chocolate. Did you know that the antioxidant poly-phenols found in dark chocolate are known to lower blood pressure, reduce oral bacteria, and improve cognition? Still need convincing it’s ok to take one more piece?

At this point, you're probably wondering, but what does chocolate have to do with filtration? And you're right, not nearly as much as you’d find in the beverage industry. But Theo, in an effort to maintain its organic product status, uses only essential oils as opposed to extracts to create the sensational, true to flavor tastes its customers have come to enjoy. That’s where filtration comes in to play. Diatomite filtration has been used for decades in the food and beverage industry to produce essential oils for foods. In recent months, we’ve received several inquiries about the use of cross flow filtration for essential oil extraction as well. Science never smelled so sweet (or tasted this good)!

Visit Sterlitech at the ACS Spring 2011 Exposition in Anaheim, March 27th-31: Booth #313

Theo Chocolates are available at Whole Foods nationwide. For more information, visit www.theochocolate.com

Have you ever wondered where you would be without Thomas Graham? If you are a chemist or membrane scientist, you probably should. Scientists of many disciplines are indebted to Thomas Graham for his groundbreaking studies on gas flow through microporous membranes. His work, which included creating Graham’s Laws of Diffusion to describe the relative permeation rate of two gases, was instrumental in the creation of colloidal chemistry and the advancement of membrane science.

In terms of real world applications, Graham’s efforts are a precursor to inventions ranging from the artificial kidney to the atomic bomb. His feats are even more impressive when you consider that in order to perform his experiments he had to first generate the necessary gases himself, and also that his selection of membrane materials was limited to whatever objects he could find, such as rubber balloons, animal bladders, and thin metal sheets.

Thomas Graham was born in Edinburgh, Scotland in 1805 and enrolled in the University of Glasgow at the tender age of 14! He went on to become Professor of Chemistry at Anderson’s College (now part of Strathclyde University) and then at University College London. In 1854, Graham was named Master of the Mint, a position once held by Sir Isaac Newton. Even though this was considered to be more of an honorary title at the time, Graham invested himself so heavily in its duties that he actually suspended his research for several years. The position was permanently retired following his death in 1869.

Thomas Graham’s influence has grown considerably since his passing. In addition to Graham’s Laws for diffusion and effusion of gases, he introduced the terms gel, sol, colloids, crystalloids, and dialyzer into the scientific lexicon. Other important contributions include his determining the formulas of the PxOy polyatomic ions, and in the 1850’s he hypothesized that a membrane machine could be created that would separate the blood toxins that built up in kidney failure, paving the way for modern kidney dialysis. His tenacity was rewarded with several honors in his lifetime, including the Copley Medal of the Royal Society, the Royal Medal of the Royal Society (twice), and the Prix Jecker of the Paris Academy of Sciences.

Sources:
“Thomas Graham,” D. Lane and J. Solon, Woodrow Wilson Leadership Program in Chemistry, The Woodrow Wilson National Fellowship Foundation, CN 5281, Princeton, NJ 08543; http://www.woodrow.org/teachers/ci/1992/Graham.html.

“Membrane Pioneers: Thomas Graham,” S. Alexander Stern and Richard W. Baker. Membrane Quarterly. Volume 25, Number 1, January 2010, pgs. 17-19.

We've previously discussed how the combination of silver and carbon nanotubes can be used to create more efficient water purification filters, now you can see a little bit about how this filter is made thanks to Technology Review and Stanford University. You can read more about the process here.

Over the years we have seen an increased use of filtration equipment in juice processing, particularly regarding ultrafiltration (UF) or microfiltration (MF) for the clarification of apple juice.  Since it has been demonstrated that membrane filtration can produce yields of 95%-99% - compared to only 80-94% through conventional processes – it is no wonder that filtration methods are growing in prevalence.  The greater yield combined with the reduced time and labor costs have translated to hundreds of thousands of dollars saved for juice processing plants!

If you are considering juice filtration, here a couple of tips to keep in mind:

• The juice must be clear.  Of the four common types of apple juice produced – natural, crushed, clarified, and clear – only clear juice is suitable for membrane processing.
• Consider ceramic membranes.  More and more fruit juice installations are installing ceramic membranes.  While these do have  a higher cost than other materials, they do offer a higher flux, much longer life, and better resistance to aggressive processing and cleaning conditions.
• Know your operation.  Since fruit juices have a very low level of retained solids, the optimum mode of operation is the modified batch operation with a partial recycle of retentate.
• Not just for apples.  Other fruit and vegetables that have benefited from membrane filtration include: apricot, carrot, cherry, cranberry, grape, lemon, lime, orange, peach, passion fruit, and tomato.

References:
Ultrafiltration and Microfiltration Handbook.  Cheryan, Munir.  Technomic Publishing Company, 1998.
Microfiltration and Ultrafiltration: Principles and Applications.  Zemon, Leos & Zydney, Andrew.  Marcel Dekker, 1996.