NANOCERAM-PAC™ SERIES
Pleated filter cartridges combining high efficiency particulate filtration with a high efficiency (powdered) activated carbon (PAC) into a single depth media - NanoCeram-PAC™ is a further advancement in Argonide’s series of filters and is a major breakthrough in using activated carbon for purifying water.
Background -Typically GAC is used in a packed bed or is combined into a media using adhesives or via a foamed polymer. What is new with NanoCeram-PAC™ is that fine activated carbon powder (-325 mesh) is held within the structure by electro-adhesive forces, without using adhesives that would blind or deactivate the carbon. As compared to media containing granular activated carbon (GAC), PAC offers a much greater external surface area that results in much more rapid adsorption of soluble contaminants. Contaminants removed include chlorine, iodine or soluble organics that may be highly toxic or may cause unpalatable taste and odor. The result is much greater adsorption efficiency at moderate to high flow rates and/or with thin beds of media, such as a single layer pleated cartridge. At the same time, the media is capable of retaining bacteria, virus and colloidal particles with efficiency that is unsurpassed as compared to a depth media, a microporous membrane or even an ultraporous membrane.
How it works – Nano alumina is combined into a microglass fiber matrix to form an electropositive (~+50 mV) filter media and is then converted into pleated cartridges. The active ingredient is a nano alumina fiber that is only 2 nanometers in diameter and about 250 nm long and is grafted to a microglass fiber backbone. Coarser cellulose or synthetic polymer fibers are added to enlarge the pore size and provide flexibility and strength. The media is produced by a conventional wet laying process and is then pleated and end-capped to form a cartridge. Since virtually all small particles are electronegative in water, they are readily adsorbed. This filter has a high efficiency for capturing very fine particles. What we discovered is that we could add very fine or even nano size particles in fabrication of the paper-like sheet, and that they are held so tightly that they can’t be removed without destruction of the media or by other heroic means. The first commercial implementation contains 32 weight percent of a high surface area commercial PAC (Iodine Number=1100 mg/g, ave.particle size ~27 μm). The new media is laminated with polyester spun-bond. Its pore size is 2 μm and its flowrate is equivalent to NanoCeram® cartridges.
Features and Benefits
· Retains soluble organics (VOC’s, toxic organics) and residual chlorine with high efficiency – See Figure 1, that compares the retention of 24 ppm chlorine at a high flowrate (3 gallons/ft2/min) with four other commercially available carbon-containing media. Similar results were reported [1] comparing dynamic iodine adsorption with single and multiple layers. A single layer will remove >95% of chloroform at a high flow (1 g/ft2/min).
· Turbidity reduction maintained below 0.01 NTU (Nephelometric turbidity units) until terminal pressure drop (35 psi)
· Silt Density Index (SDI) is less than 1.0 – SDI is a more sensitive measure of particulate contamination of water than turbidity. It measures how long it takes for a water mixture to clog a 0.45 micron membrane. Manufacturers of reverse osmosis (RO) membranes suggest an SDI lower than 3.0. That is not attainable by fibrous depth filters. Manufacturers of ultraporous membranes typically claim SDI’s of 1.75 to 2.25. The PAC in NanoCeram-PAC™ is held so tightly that the resulting SDI is ~1.
· NanoCeram-PAC™ will trap ultrafine carbon downstream of packed GAC beds.
· Bacteria- A 2.5-10” diameter cartridge retained >6 LRV of E coli at a flow rate of 4 gpm
· Virus- A 2.5-10” diameter cartridge retained >3 LRV of MS2 (25 nm) at a flowrate of 4 gpm
· Retains cysts – A filter disc was tested at a third party laboratory and found to retain >99.99% of 4 micron monodisperse spheres (simulant for Cryptosporidium cysts).
· High dirt holding capacity – Even though the media is loaded with 32% of particulate carbon, its dirt holding capacity (as measured using A2 fine or even ultrafine test dust) is ~118 mg/in2, and is equal to or slightly greater than that of NanoCeram® .
· Effective between pH 5 and 9 and in the presence of 30 g/L of NaCl, simulating seawater
· Removes both soluble and insoluble total organic carbon (TOC’s)
Suggested applications
· Filtration of VOC’s, disinfection by-products (DBP’s), trace toxic organics such as organic pesticides and endocrine disruptors from waste water
· Removal of residual chlorine, toxic organic pollutants and particulate from drinking water for point of use (POU) and point of entry (POE) filter systems
· As a polishing filter downstream of large granular carbon beds used for solvent recovery
· As a polishing filter downstream of coagulation and filtration water purification systems
· Removal of particulate sorbents downstream of filter beds (e.g.-arsenic or IX resins)
· As a prefilter for protecting RO membranes for both fresh water and sea water – Filters chlorine that can damage membranes as well as sub-micron particles that tend to foul RO.
· As a filter downstream of RO used in drinking water. NanoCeram-PAC™ will filter bacteria and virus as well as any small molecule organic pollutants that might have escaped the RO
· Purification of aqueous analytical solutions
· Chemical-biological filters for protection against terrorist contamination of water supplies
Availability - NanoCeram-PAC™ is currently available in 2.5” diameter (5” and 10” long) double open end and in 4.5” (Big Blue) configurations. The 4.5”X 20” can be integrated into HyFlo (up to 830 gpm) housings.
Figure 1 – Adsorption of chlorine by NanoCeram-PAC™ and other media
1. Tepper, F and Kaledin, L- Amer. Filtration Soc. annual meeting, Orlando, March, 2007
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