Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
2002-08-30
2004-07-27
Barry, Chester T (Department: 1724)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S759000, C210S763000, C210S760000
Reexamination Certificate
active
06767472
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an improved process for the oxidative treatment of contaminated aqueous media. Specifically, the present invention relates to a process whereby hydrogen peroxide and ozone are employed to treat contaminated aqueous media with unexpectedly high contaminant removal. The hydrogen peroxide is exposed to a catalytic environment for a controlled period of time, and ozone is added to the aqueous media subsequent to the removal of the aqueous media from the catalytic environment.
Oxidation processes are one important class of treatment technology that destroy contaminants in aqueous media and yield harmless products. For purposes of this disclosure, the terms destruction and degradation of contaminants will refer to the transformation of such contaminants, including any form of transformation such as polymerization, bond-breaking or even complete oxidation to carbon dioxide. One such oxidation process generally involves reactions of organics with reactive species such as hydroxyl radicals, superoxides, hydrated electrons and singlet oxygen. Ozone with ultra-violet light and ozone with hydrogen peroxide have been successfully used for the treatment of synthetic organics and chemicals resistant to biological degradation. These processes, however, suffer from being more expensive than traditional water treatment processes, and are subject to radical traps that can severely reduce their efficiency.
Hydrogen peroxide has been used as an oxidant in engineered systems for treatment of liquid wastes and as a source of oxygen for enhanced bioremediation in aquifers and soil systems. The use of hydrogen peroxide is based on the exploitation of its decomposition chemistry, which can involve the formation of reactive intermediates such as hydroxyl radicals (OH.), perhydroxyl radicals (.HO
2
), and superoxide radical anions (O
2
−
). For example, the reaction of hydrogen peroxide with ferrous iron, commonly referred to as Fenton's reagent, has been shown to produce hydroxyl radicals. Hydroxyl radicals are one of the most powerful oxidizing species known, capable of reacting with a wide range and number of organic compounds.
Heretofore in the art it has generally had been believed that the contaminant degradation efficiency of a hydrogen peroxide system could be increased by increasing the amount and rate of hydrogen peroxide decomposition, which was believed to lead to a proportional increase in usable reactive intermediates, i.e., those intermediates that react with the contaminant or lead to the degradation of the contaminant. It was also believed that increased efficiency could be achieved by increasing the concentration of hydrogen peroxide within the system, as well as by increasing the exposure time between the hydrogen peroxide and catalyst. In other words, it was believed that the mass of hydrogen peroxide decomposed increased as the hydrogen peroxide was in contact with the catalyst, thereby leading to increased concentrations of intermediates that would react and degrade contaminants. It has recently been discovered, however, that the formation of useful intermediates from hydrogen peroxide decomposition is not proportional to the amount of hydrogen peroxide decomposed and/or the exposure time between hydrogen peroxide and the catalyst. That is, as hydrogen peroxide is decomposed by catalysis, the concentration of useful reactive intermediates does not increase with increasing concentrations of hydrogen peroxide added to the system. In fact, useful intermediate concentration is believed to decrease.
It is generally believed that the decrease in useful intermediate concentration is a result of scavenging by the catalytic material. Heretofore in the art, attempts to prevent this scavenging included covering up surface sites or adding amendments to the catalyst to control the reactive pathways. A more detailed explanation of these mechanisms is set forth hereinbelow.
Thus, a need exists to develop a hydrogen peroxide system for treatment of contaminants in aqueous media that reduces the inefficiencies associated with hydrogen peroxide systems known in the art.
SUMMARY OF INVENTION
It is therefore, an object of the present invention to provide a a process for the treatment of contaminated aqueous mediums.
It is another object of the present invention to provide a process whereby contaminant decomposition is accelerated.
It is yet another object of the present invention to provide a process whereby hydrogen peroxide is employed in conjunction with a catalytic material in a fashion where scavenging by the catalytic material is reduced.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to the oxidative treatment of contaminated solutions, which shall become apparent from the specification that follows, are accomplished by the invention as hereinafter described and claimed.
In general the present invention provides a process for the treatment of an aqueous media having contaminants therein, comprising adding hydrogen peroxide to the aqueous media, exposing the aqueous media to a catalytic environment, removing the aqueous media from the catalytic environment prior to the aqueous media having a five minute residence time within the catalytic environment, adding ozone to the aqueous media, and allowing the ozone and aqueous media to interact for at least one minute outside of the presence of the catalytic environment.
The present invention also provides a process for the treatment of an aqueous media having contaminants therein comprising the steps of adding hydrogen peroxide to the aqueous media, exposing the aqueous media to a catalytic environment, removing the aqueous media form the catalytic environment before five percent of the hydrogen peroxide decomposes, adding ozone to the aqueous media, and allowing the ozone and aqueous media to interact for at least one minute outside of the presence of the catalytic environment.
The present invention further provides an improved process for degrading organic contaminants within an aqueous media of the type where hydrogen peroxide is added to the aqueous media, and the aqueous media containing the hydrogen peroxide is introduced to a catalytic environment to initiate decomposition of the hydrogen peroxide, wherein the improvement comprises controlling the exposure of the hydrogen peroxide to the catalytic environment so that the aqueous media is removed from the catalytic environment before five percent of the hydrogen peroxide entering the catalytic environment is decomposed by the catalytic environment, and the improvement further comprises adding ozone to the aqueous media immediately after the aqueous media ceases contact with the catalytic environment.
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Barry Chester T
Firca Donald J.
Moxon II George W.
Roetzel & Andress
The University of Akron
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