What is nanofiltration?

When you think of nanotechnology, you may think of an imperceptible, self-replicating microplague come to wipe out the human race (as in the Michael Crichton novel). Or you may consider the ever-decreasing size of technology. But a form of nanotechnology performs another function: Nanofiltration removes harmful particles from our drinking water every day.

Nanofiltration came to prominence in the 1970s and 1980s as an alternative to reverse osmosis, ultrafiltration, and microfiltration. These forms of water filtration were not totally effective at removing particles of all sizes, however. As filter technology improved, ie, as more technical, advanced membranes were designed, smaller-sized grains were able to be filtered out. By the end of the 1980s, nanofiltration technology had developed such that it filtered out adulterants from water that other filtration technologies could not. This article on nanofiltration says, for instance,

The key difference between nanofiltration and reverse osmosis is that the latter retains monovalent salts (such as sodium chloride), whereas nanofiltration allows them to pass, and then retains divalent salts such as sodium sulphate. Robert Peterson, in his Foreword to Elsevier's Nanofiltration – principles and applications, describes reverse osmosis (especially in the water treatment business) as the main course, the steak perhaps, of a meal, whereas nanofiltration “is like the wine menu … an opportunity for creativity and exploration”.

The key to the development of nanofitraltion technology has been creating better and better filtration technologies. Nanofiltration is a liquid phase membrane separation process; it separates inorganic and organic substances from solution in a liquid. Nanofiltration separates these substances by running them through a membrane under pressure (a smaller amount of pressure than what would normally be used for reverse osmosis, as well). Great advances in nanofiltration generally occurs due to the creation of better membrane technologies. Presently, many nanofiltration systems use an inorganic material; ceramic is an especially popular material.

Ceramics have excellent corrosive-resitance and feature an excellent range of control over their porosity. Ceramic membranes have the advantage of being fully capable of functioning in very high or very low pH environments. Ceramic nanofiltration has industrial applications in the food and dairy sector, chemical processing, pulp and paper industry, and textiles. However, the predominant use of nanofiltration is of course in fresh, process, and waste water filtration.

A growing use of ceramics in nanofiltration is with field of nanofiber media. Nanofibers are made of synthetic materials that are spun into fibers whose diameters range from 10 μm to 100 nm. Advances in spinning techniques have enabled water filtration manufacturers to better utilize ceramic technology. Such ceramic nanofilters feature the high density and durability of ceramics with the capability of removing contaminants to below 0.1 μm. Using ceramics in water filtration technology has increased the robustness and safety of our water supply. And as manufacturers of technical ceramics find ways to decrease cost, we will only see ceramics’ influence in water filtration technology increase.

Mercedes-Benz Stops With Ceramics

Mercedes-Benz has developed new braking technology that utilizes technical, stress-resistant ceramics. Upon request, the automaker will install in a new vehicle an AMG high-performance braking system, which uses composite brake discs.

eMercedesBenz, a Mercedes-Benz blog, describes the AMG high-perfomance braking system as sporting,

ventilated, grooved and perforated brake discs all-round in size 390 x 36 millimetres at the front and 360 x 26 millimetres at the rear ensure excellent deceleration performance. Brake discs in race-tested composite technology are installed at the front axle, with the grey cast iron discs radially and axially floating, and fixed to an aluminium bowl via stainless steel connections. This sophisticated technology ensures highly efficient heat conduction, and therefore outstanding fade-resistance even with a highly dynamic style of driving.

They go on to say that the optional ceramic composite braking system--labeled “AMGCarbon Ceramic” uses discs fashioned from carbon-fiber and reinforced by ceramics in a vacuum at 1700 degrees Celsius. The resulting brake disc is extremely pressure- and stress-resistant, which allows for a markedly decreased braking distance. Not only that, but the composite ceramic disks are 40% lighter than cast iron brake discs and allow for a more direct steering response while driving the car.

This is yet another great use of technical ceramics. It’s almost amazing how designers and engineers are only lately using ceramic materials for such diverse applications calling for extreme heat- and stress-resistance. Historically, the entry cost of working with ceramics has been high, but as manufacturing processes and materials decrease in price, ceramic technologies are being adopted at a high rate, passing on a great value and quality proposition to the consumer.

Georgia Tech Researchers Discovery Mystery Ceramic

Researchers at Georgia Tech have created a new ceramic material that could have revolutionary applications in fuel cell technology. It is still in a nascent, developmental stage, but it could reduce tremendously the cost of creating fuel cells. The high cost of fuel cells has been a barrier to their wider adoption.

The Georgia Tech researchers were supported by the U.S. Department of Energy’s Basic Energy Science Catalysis Science Program. Using the government money, they developed a new material for use in solid oxide fuel cells (SOFC). A SOFC generally uses a ceramic electrolyte, which in this case is a yttria-stabilized zirconia (YSZ) ceramic. Traditionally, YSZ operates poorly in an SOFC because it is inefficient, clogs easily, and must operate at a high temperature due to its poor conductivity at low temperatures. The new ceramic material, though, gets around all these drawbacks.

The material is a Barium-Zirconium-Cerium-Yttrium-Ytterbium Oxide (BZCYYb), which can be used as a coating on a traditional anode or a replacement for YSZ altogether. It has been lab-proven for performance up to 1,000 hours of continuous use, but it requires more testing to determine its stability and lifespan.

Researcher Meilin Liu says,

“Solid oxide fuel cells offer high energy efficiency, the potential for direct utilization of all types of fuels including renewable biofuels, and the possibility of lower costs since they do not use any precious metals... We are working to reduce the cost of solid oxide fuel cells to make them viable in many new applications, and this new material brings us much closer to doing that.”