Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1993-10-22
1996-07-09
Cintins, Ivars C.
Liquid purification or separation
Processes
Ion exchange or selective sorption
210679, 210694, 210747, 210170, 210503, C02F 128
Patent
active
055341543
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the cleaning of contaminated water.
The invention is mainly concerned with the cleaning of groundwater in its native aquifer, or of effluent water discharged from a manufactory.
The invention is not limited in scope only to specific contaminants, but the contaminants with which the invention is mainly concerned are those which are carcinogenic or otherwise hazardous in trace quantities, and which are difficult to break down chemically. A typical example of the type of contaminant is the halogenated hydrocarbon (organic) type, which includes eg chloroform; solvents such as carbon tetrachloride; and pesticides such as DDT.
THE PRIOR ART
One of the well-known conventional systems for removing contaminants from water is to pass the contaminated water through a body of activated carbon. Activated carbon is highly adsorptive material, whereby the dissolved contaminants are removed from the water and retained on the activated carbon.
Over a period of time, the contaminant builds up on the activated carbon. One way of dealing with the activated carbon that has become saturated with the contaminant is to periodically remove the activated carbon, and dispose of it as a hazardous waste.
Alternatively, periodically the activated carbon may be flushed or otherwise treated (eg by heating) to remove or drive off the contaminated material that has accumulated. When the activated carbon has been flushed it can be re-used. The contaminants however still exist, and must be disposed of.
Thus, one of the disadvantages of the conventional decontamination systems based on the use of activated carbon is that the contaminant remains intact. In the conventional system, the activated carbon functions simply to strip the contaminant out of the water; the contaminant material that is removed from the activated carbon upon flushing is still hazardous. In fact, it is even more hazardous because it is concentrated. The contaminant may finally be broken down in a further treatment facility, or it may be disposed of as a hazardous waste.
It is an aim of the invention to provide a decontamination system in which contaminants, such as those of the halogenated organic type, are broken down into harmless, or at least less hazardous, chemical substances.
It is also known in the art to pass an halogenated-organic contaminant through a permeable body comprising a pair of metals. It has been found that the halogenated-organic materials break down, when in prolonged contact with the pair of metals, inferredly by a form of hydrolysis reaction, into chlorides etc; these substances generally are virtually harmless in trace quantires, and often will precipitate out of the water as insoluble solids.
One of the disadvantages with the above "metals" system is that substantial periods of time, and/or substantial quantities of the metals are required. The system can be expensive, not only as regards providing the metals, but also as regards arranging for a sufficient residence time of the water within the body of metals, and as regards creating the best conditions of pH level, temperature, oxidizing/reducing conditions, etc, throughout that residence time.
The great advantage of the "metals" system is that the hazardous material disappears.
It is an aim of the invention to provide a decontamination system in which, as in the known "metals" system described above, the hazardous materials are broken down and converted into relatively harmless chemical compounds; it is also an aim to achieve this breakdown of the contaminants using substantially smaller quantities of metal.
GENERAL FEATURES OF THE INVENTION
In the invention, the contaminated water is passed through a permeable body comprising a mixture of an adsorptive material, such as activated carbon, and a metal, such as iron.
It is recognized that the function which the adsorptive material performs when mixed with the metal is substantially different from its conventional function as a mere adsorber of the contaminant. Rather, it may be regarded that the adsorptive material
REFERENCES:
patent: 3784014 (1974-01-01), Turner
patent: 3803033 (1974-04-01), Sutherland
patent: 4234420 (1980-11-01), Turbeville
patent: 5057227 (1991-10-01), Cohen
patent: 5064534 (1991-11-01), Busch et al.
patent: 5149437 (1992-09-01), Wilkinson et al.
patent: 5266213 (1993-11-01), Gillham
Cintins Ivars C.
University of Waterloo
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