Liquid purification or separation – Processes – Including geographic feature
Reexamination Certificate
1998-04-16
2001-09-11
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Including geographic feature
C210S757000, C210S198100, C210S903000, C210S909000
Reexamination Certificate
active
06287472
ABSTRACT:
BACKGROUND TO THE INVENTION
In that technology, dissolved contaminants of the halogenated-organic type are broken down by passing the contaminated water over or through a body of iron granules, such as iron filings. Prolonged proximity to the iron, under strictly anoxic conditions, causes the breakdown reaction.
GENERAL POINTS OF THE INVENTION
It has now been found that coating the particles of iron with a small amount of nickel results in a great improvement in performance with respect to degradation rates of the contaminant. Also, it has been found, in cases where the degradation of the initial contaminant is to a substance that is also an halogenated organic contaminant, that such induced contaminants are less in concentration, and degrade comparatively much more quickly than they degrade when the particles are plain iron.
This new development, i.e coating the iron particles with nickel, gives degradation rates that can be almost an order of magnitude faster than when un-coated iron particles have been used.
It has also been found that, when the iron particles are coated with nickel, the need to exclude oxygen from the body of iron particles is not so dire. Therefore, surface water, industrial waste streams, etc, can be treated, in addition to oxygen-free groundwater.
Enhanced results have been encountered also when the iron particles are coated with an alloy of nickel-boron, or an alloy of nickel-phosphorus.
The manner in which the coating is applied is important. The coating should not be complete, i.e the coating should be patchy, whereby some of the surface of the iron is not coated. Thus, the water, and the contaminants in the water, are exposed to direct contact with the iron.
As regards the type of contaminant that can be treated, not only does the new development apply to the treatment of the halogenated hydrocarbons, as with the original technology, but it is also applicable for the treatment of contaminants of the kind that have nitrogen groups in place of the halogens, for example.
As to the treatment material, other combinations of metals, i.e other than iron coated with nickel, are contemplated. One of the key characteristics of the first metal, i.e., the metal that constitutes the main weight of the treatment material, is that the first metal should be cheap. Iron is good from this standpoint, of course, because of the ready availability of cheap iron and steel scrap from industry. The second metal, i.e., the metal which is applied as a patchy coating to the first metal particles, should be of a lower electrochemical activity than the first metal. Thus, nickel may be used as the second metal for coating iron particles. On the other hand, zinc could not be used as the coating for iron particles.
One of the reasons the coating of the iron particles can be of the desired patchiness, derives from the fact that the iron particles, being scrap from industrial processing, often are rusty, i.e they have a coating of iron oxide. This oxide coating is itself uneven, both as to thickness and as to chemical composition, and this unevenness is of assistance in ensuring that the coating applied to the particles will be patchy.
The plating process tends to remove the oxide, and thus to leave bare the areas of the surface of the particle that are un-coated. The bare metal thus exposed then tends not to re-oxidise, because of the immediate proximity of the patches of the second metal, which sets up an electro-chemical balance. A point to be noted is that if too much second metal (nickel) is used in the coating, some of the nickel leaches out, which is itself a contaminant. The desired small amount of nickel is instrumental in maintaining the electro-chemical balance.
Preferably, in the invention, the coating process is electro-less, in that the coating is of the kind that can be applied to the first metal without the input of electrical energy. An electricity-applied plating process would be much more expensive.
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Gillham Robert W
O'Hannesin Stephanie F
Odziemkowski Marek S
Anthony Asquith & Co.
Barry Chester T.
University of Waterloo
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