The NanoCeram^® Advantage

The electroadsorptive ingredient in the NanoCeram^® filter is a nano alumina fiber that has a surface area from 350-500 m²/g, with virtually all of that on the outside surface of the fiber and exposed to the entire spectrum of particulate in an aqueous stream (Figure 9). Such high surface areas are unattainable either in a membrane or in a fibrous filter even where nanofibers are being used. Nanofibers are very difficult to manufacture much below a 100nm diameter versus a 2nm diameter in the case of nano alumina.

And even if a nanoalumina fiber with a 2nm diameter were commercially available, this fiber (and virtually every other nanomaterial) would have a very strong tendency to agglomerate with the other nanofibers. Once this agglomeration occurs, the advantage of that huge surface area is lost. The key to NanoCeram^®’s advantage is that we’ve developed a novel method of grafting these submicron alumina fibers permanently to a scaffold. This serves to keep the fibers separate from one another so that each fiber can do what it is optimized to do . . . attract and capture submicron particles.

Dirt holding capacity (“DHC”) generally refers to the capacity of a filter cartridge to retain a given weight of particles before the cartridge plugs. Logic dictates that for a given pore size, the larger the particle challenging that filter, the greater would be the DHC (based on how long it takes for that filter to plug) as smaller particles would simply pass through the larger pores.

However, there are few applications where capturing those smaller particles don’t have significant value.

As a “broad spectrum” particle adsorber, the NanoCeram^® cartridge removes both coarse particulate as well as fines. For example, in applications currently using a 3 micron cartridge, the NanoCeram^® will remove 3 micron and larger particulate with a similar efficiency to the 3 micron sediment cartridge. Yet, when the two cartridges are weighed and compared after operating under identical conditions and for the same period of time, the NanoCeram^® will have removed several times the quantity of particulate (by weight) than the standard sediment cartridge. The difference is that NanoCeram^® will remove virtually all of the sub-micron particles that pass through a conventional filter.

In many applications, removing sub-micron particles is vital. They are responsible for much of the fouling of reverse osmosis (RO) membranes, and would degrade the efficiency of ultraviolet (UV) and ozone disinfection systems. Unfiltered fines and colloidal matter can also affect chemical processes and impact the quality of the surfaces of precision products.
 

How long a filter will last is a very common question, but a difficult one to answer. Several factors can affect life, but the overriding factor is the load and type of particles being filtered. Particulate contaminants may include colloidal inert matter, inorganic particles such as metal oxides, natural organic matter (NOM), total organic carbon (TOC) to include humic/tannic/fulvic acids, endotoxins, bacteria, cysts, virus, etc. New EPA (in the United States) regulations require that the turbidity (defined as a cloudy condition in water due to suspended silt or organic matter) of municipal water must be reduced to less than 1 NTU (Nephelometric Turbidity Units).

The answer is even more complex when discussing soluble contaminants such as chlorine. In this case, flow velocity (the speed at which water flows through a set surface area of media, often in terms of cm/sec) is a very important metric.

All carbon-based products require “residence time” for contact between the contaminant and the carbon itself. The longer the contact time, the greater the dynamic adsorption rate of the carbon for soluble contaminants. This is why the smaller particles of PAC used in NanoCeram-PAC filters offer such an advantage. The huge surface area of such small carbon particles means that available surface area to adsorb the chlorine is enormous (more capture sites). Therefore, the “bounce-back” capacity of the PAC allows for higher flow rates to attain chlorine adsorption rates which would be comparable to GAC-based filters running at much slower flow rates.