Patent Application
20130075316
The present invention is related to a method of treating water pollutant with the functions of adsorption, oxidation and activation, and more particularly to a method of treating water pollutant using persulfate to stably combine with adsorbent (with low oxidation number) and iron-containing activator.
Groundwater contaminated by gasoline and other petroleum hydrocarbons has become a more common and serious problem. The source of contamination mainly comes from underground storage tank leakage, pipeline rupture and ground oil leakage, etc. Since the pipelines of gas stations and large oil storage tanks are located underground and with aging facilities, earthquakes, poor construction or other human factors, the possibility of oil leakage has increased. In the United States, there are more than two million oil storage tanks and it is estimated that 35% of the oil storage tanks may be leaking (Bedient et al., 1999). In Taiwan, oil pollution cases are also gradually increasing, while the soil and groundwater pollution, is an important topic for countries all over the world.
Conventional treatment of contaminated groundwater technologies, such as extraction processing method (pump and treat, R & T) are widely used in various contamination processing sites, but traditional methods are often lengthy, and long-term remediation may be required that increases the costs. Current remediation of contaminated sites, considering costs and other factors, use (in-site) remediation methods (US EPA, 2004).
In situ chemical oxidation (ISCO) is a method that injects oxidant into the contaminated area to destroy the target pollutants. Ideally, pollutants will be completely oxidized to carbon dioxide, water and other harmless substances (ITRC, 2005). Common oxidants include hydrogen peroxide (H2O2) [Fenton's reagent], permanganate, persulfate and ozone. Using sulfate as an oxidant is a relatively newly developed chemical processes (ITRC, 2005). Persulfate is a strong oxidant, and if activated by heat or metal (such as ferrous iron), it can produce sulfate radicals (SO4−.) to rapidly degrade pollutants (Shiying et al., 2008; Chen et al., 2009). Conventional methods of in-site chemical oxidation, such as
However, the method mentioned above still has following problems: (a) only the curing agent (320) (cement) and persulfate (310) to form the oxidant releasing composition (300) to remove contaminants from water, but when the persulfate (310) is not activated, it is not efficient to remove water pollutants; (b) additional costs may be necessary to accelerate the removal of pollutants, like using heat or adding additional transition metal catalysts such as iron (II) persulfate (310), which will not only increased costs, but also reduce permeability of a water-containing layer because after ferrous iron (oxidation number 2) becomes ferrous ion (oxidation number 3) through oxidation, the precipitation will increase to clog the water-containing layer.
Therefore, there is a need for an improved and new integrated processing system serving the functions of adsorption, activation and oxidation to speed up degradation of the pollutants and delay the movement of the pollutants and further reduce the threat to the downstream.
The present invention provides a method of handling water pollutant using adsorption, oxidation and activation, wherein an integrated processing system has a stable persulfate combining with an adsorbent with low oxidation number (natural zeolite) and an iron-containing activator (e.g. industrial wastes, such as BF slags and BOF slags). When the adsorbent and activator co-exist, they can not only adsorb pollutants, but also activate the persulfate in a heterogeneous phase. Utilizing a principle of building a functional wall, the adsorbent can mix with the activator and persulfate to form a compound that can release the persulfate slowly in a long period of time, so that the functional wall formed by the released substance can not only delay the flow rate of the pollutants, but also efficiently remove the pollutants by the effect of heterogeneously catalyzing. Therefore, the system has the property of oxidizing, adsorbing and activating the persulfate to handle water or underground water polluted by organic substances.
Comparing with conventional techniques, the present invention has the following advantages:
(a) the integrated processing system has the persulfate, adsorbent with low oxidation number and iron-containing activator, wherein the persulfate has an oxidizing capability, the adsorbent (with low oxidation number) has an adsorbing capability, and the activator has transition metal, such as iron, to activate the persulfate. The system can not only increase the speed of eliminating pollutant, but also reduce the speed of pollutant movement to further reduce the threat of the pollution spreading to downstream;
(b) BF slag and BOF slag are industrial wastes, and the integrated processing system provides a channel for reusing the industrial wastes to easily process the industrial wastes;
(c) the activator can catalyze persulfate by itself to produce sulfate free radicals to enhance oxidation capability;
(d) the adsorbent has a function of self-cleaning, so the integrated processing system does not need a huge amount of adsorbent to reduce the costs of the pollution treatment site;
(e) the pollution treatment site can adjust the combination ratio of the persulfate, adsorbent and activator to receive the best efficiency of pollutants elimination; and
(f) the integrated processing system simultaneously possesses the functions of oxidation, activation and adsorption to efficiently eliminate pollutants and delay the pollutant flowing to downstream.
The detailed description set forth below is intended as a description of the presently exemplary device provided in accordance with aspects of the present invention and is not intended to represent the only forms in which the present invention may be prepared or utilized. It is to be understood, rather, that the same or equivalent functions and components may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices and materials similar or equivalent to those described can be used in the practice or testing of the invention, the exemplary methods, devices and materials are now described.
All publications mentioned are incorporated by reference for the purpose of describing and disclosing, for example, the designs and methodologies that are described in the publications that might be used in connection with the presently described invention. The publications listed or discussed above, below and throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention.
In order to further understand the goal, characteristics and effect of the present invention, a number of embodiments along with the drawings are illustrated as following:
Referring to
Persulfate (11) is a long-term oxidant in nature and tends not to react with the organic compounds in the soil, so that the required amount during reaction of persulfate (11) is lower than other oxidants. Thus, in addition to eliminate pollutants, using persulfate (11) can reduce the costs of the pollution treatment site.
Zeolite is an adsorbent (12) with low oxidation number, chosen from mordenite (Japan, reagent grade). As to the activator, blast furnace slag (BF slag) and basic oxygen furnace slag (BOF slag) are industrial wastes with different particle diameters, so before using them, a 10˜18 mesh (1˜2 mm) mesh sieve has to be used followed with 5% HCl to wash out the impurities, and deionized water has to be used to wash for several times. The slags are then dried for 24 hours at 105° C. and kept in a drying box (Cao et al., 2003). Since mordenite is a commercial chemical product, no pre-treatment is needed before using. According to the chemical component analysis in table 1, the percentage of iron in those two activators (13) is between 2.5 to 37.7% that indicates the potential for the activators (13) to oxidize persulfate (11).
1 Not available
In order to understand the pollutant removing efficiency of the integrated processing system (10) in the present invention, methyl tert-butyl ether (MTBE) is used as a target pollutant to compare the difference from using the integrated processing system (10) in the present invention and oxidation, activation and adsorption. According to the experimental results, the adsorbent (12) is used for adsorbing pollutant, activator (13) is helpful in the process of catalyzing persulfate (11) to degrade MTBE, and the degrading efficiency is enhanced when the amount of the activator (13) increases because the activator (13) contains metal components such as iron.
In one embodiment, when using the integrated processing system (10) (having functions of adsorption, oxidation and activation), the persulfate (11), adsorbent (12) and iron-containing activator (13) are directly added to the polluted water and underground water to destroy the pollutants by using oxidation, activation and adsorption mechanisms (see
In another embodiment, the persulfate (11), adsorbent (12) and iron-containing activator (13) can be enclosed in cement (20) and then disposed in the polluted water and underground water (see
According to the structure shown in the embodiments, the present invention has the following advantages: (a) the integrated processing system (10) has the persulfate (11), adsorbent (12) with low oxidation number and iron-containing activator (13), wherein the persulfate (11) has an oxidizing capability, the adsorbent (12) (with low oxidation number) has an adsorbing capability, and the activator (13) has transition metal, such as iron, to activate the persulfate (11). The system (10) can not only increase the speed of eliminating pollutant, but also reduce the speed of pollutant movement to further reduce the threat of the pollution spreading to downstream; and (b) BF slag and BOF slag are industrial wastes, and the integrated processing system (10) provides a channel for reusing the industrial wastes to easily process the industrial wastes; (c) the activator (13) can catalyze the persulfate (11) by itself to produce sulfate free radicals to enhance oxidation capability; (d) the adsorbent has a function of self-cleaning, so the integrated processing system (10) does not need a huge amount of adsorbent (12) to reduce the costs of the pollution treatment site; (e) the pollution treatment site can adjust the combination ratio of the persulfate (11), adsorbent (12) and activator (13) to receive the best efficiency of pollution elimination; and (f) the integrated processing system (10) simultaneously possesses the functions of oxidation, activation and adsorption to efficiently eliminate pollutants and delay the pollutant flowing to downstream.
Having described the invention by the description and illustrations above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Accordingly, the invention is not to be considered as limited by the foregoing description, but includes any equivalent
