A number of scientists have long attempted to combine carbon and silver in an effort to exploit the excellent filtration properties of activated carbon for water treatment while avoiding bacterial contamination issues by using silver, which provides bacteriostatic effects. These bacteriostatic properties of silver (and other heavy metals) have been recognised since ancient times as we know the Romans liked to keep their water in silver jars.
With the benefit of scientific progress, it was possible to envisage combining the properties of these two materials.
The various methods that preceded the NANOPURE™ process were based on chemical impregnation techniques that made them unusable for producing drinking water, as excessively high amounts of silver were released due to the product’s instability (the weak bond between the carbon and the silver salts in a Van der Waals interaction): this resulted in the reappearance of the various components of the ‘chemical bath’ used to generate the product.
This is important because the benefit of a porous material such as a filter, when it is used to purify water, lies in the fact that the pores will trap the various pollutants in the water, which then makes it an ideal site for bacterial growth.
With the NANOPURE™ process, both internal and external surfaces can be metallised without the use of ‘chemical baths’, in a modular manner, while also depositing a metal coating in the pores of the material, thus preventing bacterial growth.
The NANOPURE™ products have undergone considerable release testing, none of which has identified any quantifiable trace of released silver.
NANOPURE™ is able to confirm strong covalent bonds between the silver and the support. The typical bonds occurring in the chemical method are more akin to Van der Waals interactions and are therefore weaker.
Advanced physico-chemical analyses of our metallisation process have revealed that the silver is deposited in its purest metallic form, AgO (unlike other processes, the depositing process does not cause the metal to oxidise), ensuring excellent reactivity in the water.
The various oxidation states of the carbon (e.g., C-O, C=O, etc.) are also beneficial to the treatment of the water.
XPS-type analyses have confirmed that silver carbides are created during the plasma process generated by our treatment, and they confirm the exceptional stability of the resulting product, which exceeds the scope of a bond between two elements!
Residual properties :
Residual properties refer to the water’s ability to resist becoming polluted after treatment. The following experimental process is carried out to test for residual properties: The water treated by our process is collected in a container and left in the open air for a few days. After this period, we take a sample of this water and submit it to a battery of bacteriological analyses: no pathogenic bacteria are detected (analyses certified by laboratories). This represents the properties acquired by water treated by the NANOPURE™ process, after contact with our product, in a very precisely defined form (kinetic energy, etc.) In fact, the measured passage of water through the NANOPURE™ material catalyses physico-chemical reactions which, according to the microbiological report, serve to oxidise the bacteria, particularly through a reactive provision of oxygen (as seen above). This bactericidal property exceeds the bacteriostatic property alone.
Furthermore, the production and obtention of carbides and silvering by our process demonstrate that in terms of the product, we achieve something different to the metallically impregnated powders or materials, and this plays a vital role in the water purification and conservation we aim for.
|International Publication||Patent No: 98/47819 WO international application No: PCT/IB98/00619|
The technological process was developed with the CNRS (the French national centre for scientific research).
The powder is produced with plasma reactors.
The production of the powder, together with expert knowledge, are key factors in the whole process.