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WO1995011749A1 - Destruction photocatalytique de contaminants dans des solides - Google Patents

Destruction photocatalytique de contaminants dans des solides Download PDF

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Publication number
WO1995011749A1
WO1995011749A1 PCT/US1994/012357 US9412357W WO9511749A1 WO 1995011749 A1 WO1995011749 A1 WO 1995011749A1 US 9412357 W US9412357 W US 9412357W WO 9511749 A1 WO9511749 A1 WO 9511749A1
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Prior art keywords
solid material
reactor housing
free radicals
source
catalyst
Prior art date
Application number
PCT/US1994/012357
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English (en)
Inventor
Ronald J. Scrudato
Pengchu Zhang
Original Assignee
Scrudato Ronald J
Pengchu Zhang
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scrudato Ronald J, Pengchu Zhang filed Critical Scrudato Ronald J
Priority to AU80938/94A priority Critical patent/AU8093894A/en
Publication of WO1995011749A1 publication Critical patent/WO1995011749A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C1/00—Reclamation of contaminated soil
    • B09C1/08—Reclamation of contaminated soil chemically
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J19/12—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electromagnetic waves
    • B01J19/122—Incoherent waves
    • B01J19/127—Sunlight; Visible light
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C1/00—Reclamation of contaminated soil
    • B09C1/10—Reclamation of contaminated soil microbiologically, biologically or by using enzymes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C2101/00—In situ

Definitions

  • This invention relates in general to the decontamination of solid materials, and more particularly to the photocatalytic degradation of contaminants in solid material such as soils, sediments and sludges.
  • a potential method for such clean-up is through the use of environmental photochemistry.
  • Environmental photochemistry seeks to utilize photocatalysis in the destruction or degradation of the contaminants from the environment.
  • Photocatalysis refers to the use of light energy to catalyze chemical reactions.
  • PCBs polychlorinated biphenyls
  • TSCA Toxic Substances Control Act
  • RCRA Resource Conservation and Recovery Act
  • Solidification/stabilization have also been utilized to immobilize PCBs in media with cementatious grout compounds and chemical stabilizers to produce a cement-like mass.
  • the created monolith should be impermeable and able to withstand environmental stresses such as freeze/thaw cycles, immersion in groundwater, and cap construction.
  • Physical and biological processes are used to destroy PCBs.
  • Incineration has been commonly used to destroy PCBs, but the high cost and production of hazardous by-products limits its application.
  • Anaerobic and aerobic biodegradation has been used for PCBs-contaminated media treatment, but is slow and perhaps only partially capable of producing less hazardous compounds.
  • Photocatalytic degradation of PCBs in solid materials may offer another alternative for PCB clean-up, and has long been desirable but little progress in this area has been made.
  • PCBs present in or bound on solid materials offers an attractive remediation potential because it is relatively rapid, degradation can be accomplished within minutes or hours (1-4) , the reaction can be conducted with sunlight (3-6) and/or artificial light, catalysts are abundant and low cost (1,3,4,7) , and PCB congeners and other contaminants may be completely mineralized (1,4) .
  • microorganisms such as Escherichia coli which can indicate fecal contamination of some aquatic systems.
  • Ireland and co-workers were the first to report inactivation of this microorganism in waters using titanium dioxide as a photocatalyst (10) .
  • the primary objective of the invention is to provide such a practical, low cost and efficient process to degrade contaminants, such as PCBs, in sediments and other solids, to the extent that the residual concentrations of the contaminants do not pose a threat to human health or the environment.
  • the subject invention provides a method and apparatus for the photocatalytic degradation of contaminants in solid material.
  • the apparatus includes means for containing a solid material; means for agitating the solid material within an aqueous source of free radicals, thereby separating the solid material into a first portion suspended in the aqueous source and a second portion deposited below the aqueous source; and means for simultaneously exposing the first portion to a photoactivatable catalyst and light energy.
  • the method according to the subject invention comprises selecting a solid material containing contaminants therein; placing the solid material in a reactor housing containing an aqueous source of free radicals; agitating the solid material, so as to separate the solid material into a first portion suspended in the aqueous source and a second portion deposited below the aqueous source; introducing a photoactivatable catalyst into the reactor housing; and exposing the photoactivatable catalyst to light energy, thereby causing reaction of the catalyst with the aqueous source of free radicals to generate the free radicals, which contact the first portion of the solid material suspended in the aqueous source and degrade the contaminants therein.
  • An apparatus for photocatalytic degradation of contaminants in solid materials, hich comprises means for containing a solid material, means for agitating the solid material within an aqueous source of free radicals, and means for simultaneously exposing the solid material to a photoactivatable catalyst and light energy.
  • the solid material is selected and treated in-situ or is placed in a reactor housing, then dampened with an aqueous source of free radicals and agitated in the presence of the catalyst and light energy. Agitation can be by continuously plowing the solid material to turn the solid material over and over.
  • the process of the subject invention is preferably operated at ambient pressure and temperature.
  • the catalyst to be used is preferably titanium dioxide which is environmentally inert, although other catalysts can also be used.
  • the photocatalytic process can take place under irradiation of artificial and/or solar light. The technology is thus safe, requires low energy and provides for in-situ and/or on-site remediation of highly contaminated sediments, soils, and/or sludges.
  • Fig. 1 is a schematic for an on-site reactor which is one embodiment of the subject invention
  • Fig. 2 is a schematic for an in-situ reactor which is another embodiment of the subject invention.
  • Fig. 3 illustrates a series of three reactors connected in series and equipped for recirculation
  • Fig. 4 illustrates a baffle design for one of the reactors shown in Fig. 3;
  • Fig. 5 is a plan view of a further reactor design according to the subject invention
  • Fig. 6 is a cross-sectional view of the reactor design shown in Fig. 5;
  • Fig. 7 is a cross-sectional view of another embodiment of a reactor design according to the subject invention.
  • Fig. 8 is a schematic of the connection of a series of photoreactors according to an additional embodiment of the subject invention;
  • Fig. 9 is a schematic showing the process of treatment of contaminated sediment according to one embodiment of the subject invention.
  • Fig. 10 shows the photodecomposition of AroclorTM 1248 in clay suspension in the presence of titanium dioxide
  • Fig. 11 shows the relative concentration changes of PCB congeners in clay suspension after irradiation
  • Fig. 12 shows the photodecomposition of PCBs in the Grasse River sediment suspension
  • Fig. 13 shows the relative concentration changes of PCB congeners in the Grasse River sediment suspension after irradiation
  • Fig. 14 is a GC/MS chromatograph for PCB congeners with 1-3 chlorines in the Grasse River sediment extraction blank
  • Fig. 15 is a GC/MS chromatograph for PCB congeners with 1-3 chlorines in the Grasse River sediment extraction after 2 hours exposure to titanium dioxide
  • Fig. 16 is a GC/MS chromatograph for PCB congeners with 1-3 chlorines in the Grasse River sediment extraction after 6 hours exposure to titanium dioxide
  • Fig. 17 is a GC/MS chromatograph for PCB congeners with 4-6 chlorines in the Grasse River sediment extraction blank
  • Fig. 18 is a GC/MS chromatograph for PCB congeners with 4-6 chlorines in the Grasse River sediment extraction after 2 hours exposure to titanium dioxide;
  • Fig. 19 is a GC/MS chromatograph for PCB congeners with 4-6 chlorines in the Grasse River sediment extraction after 6 hours exposure to titanium dioxide.
  • the apparatus of the subject invention provides for the photocatalytic degradation of contaminants in solid material, such as sediment, soil, or sludge.
  • the main components of the subject invention are a means for containing a solid material, a means for agitating the solid material within an aqueous source of free radicals, and means for simultaneously exposing the agitated solid material to a photoactivatable catalyst and light energy.
  • a solid material is placed in a reactor housing.
  • the housing can comprise any suitable shape or form.
  • a caisson which is a large diameter pipe can serve as the housing in an in-situ application.
  • An additional "housing" might include a natural or constructed pond or lake which can be used to contain the material to be treated or can be the photocatalytic reactor vessel.
  • a large vat can serve as the housing in an on-site or remote application.
  • the agitation is preferably accomplished utilizing moving baffles within the reactor housing or by utilizing a dredge located within a caisson in an in-situ application.
  • the baffles may be mounted to a rotating boom.
  • the agitation separates the solid material into a first portion suspended in the aqueous solution and a second portion deposited below the aqueous source.
  • the baffles can be movably positioned within the suspended portion.
  • the baffles can be, for example, plow-shaped, and be positioned at the lower level of the bottom portion. Agitation of the solids to be treated may also be accomplished by air and/or water induction.
  • the first suspended portion is then exposed simultaneously to a photoactivatable catalyst and light energy. Contaminants within the first portion are thereby degraded by the action of the catalyst, activated by the light energy.
  • Suitable catalysts for such an application include catalysts comprising semiconductor materials, such as titanium dioxide or zinc oxide. Other suitable photoactivatable catalysts will be readily apparent to those skilled in the art.
  • the continuous agitation causes the suspended portion to be in constant motion, thereby maximizing exposure to the catalyst and light. For example, maximum exposure occurs at the surfaces of the aqueous source. This may be at the top surface if the light energy is being applied from above the aqueous source at the top of the reactor housing, or at the side surfaces of the contained solution if light is being applied from the sides of the reactor housing (i.e. with a glass-walled reactor housing).
  • the agitation causes the aqueous solution containing the suspended portion to "roll" past the light surfaces continually.
  • the bottom portion of the solid is also treated to maximize exposure to the catalyst and light energy, so that contaminants therein are degraded.
  • the suspended portion can be removed from the reactor by suitable means (i.e. gravity or pumped) when its treatment is complete. This will reveal the bottom portion.
  • suitable means i.e. gravity or pumped
  • a small amount of the aqueous source of free radicals is left overlying the bottom portion, to serve as the source of free radicals.
  • the bottom portion is in contact with the catalyst and light energy simultaneously. Therefore, degradation at the surfaces of the bottom portion can occur.
  • the bottom portion can be removed from the reactor housing and transferred to a secondary or tertiary reactor housing. Removal can be by any suitable means, such as an auger or wormscrew, conveyor, gravity flow or pumping.
  • the bottom portion can again be mixed with an aqueous source of free radicals to create a new suspended portion and a new bottom portion.
  • the bottom portion can be continually agitated within the second housing.
  • the treated suspended portion can also be transferred to a series of reactor housings for further treatment and exposure to catalyst and light. Numerous contaminants known to those skilled in the art can be removed by such photocatalysis.
  • PCBs polychiorinated biphenyls
  • Echerichia coli a polychiorinated biphenyls
  • inorganic contaminants such as metals, and pesticides, fungicides, and insecticides.
  • the examples include non-aromatic chlorinated hydrocarbons (chloromethane; tetrachloroethylene; dichloromethane; dichloroethane; trichloromethane; 1,1 dibromoethane; carbon tetrachloride; 1,2 dibromoethane; dibromomethan ; ethylene dibromide; tribromo ethane; monochloroacetic acid; trichloroethylene; and dichloroacetic acid) ; aromatic chlorinated hydrocarbons (PCBs; 1,2,4 trichlorobenzene; dioxins; 3,3 dichlorobiphenyl; chlorobenzene; 2,4,5 trichlorophenoxyacetic acid; and 4,4' DDT); aromatic and non-aromatic hydrocarbons (benzene; alkanes; toluene; alkenes; xylene; alkynes; and ethylene
  • the source of free radicals can derive from any suitable source, such as water.
  • the catalyst will cause the release of free radicals from the water molecules upon exposure of the catalyst to light energy in the presence of the water.
  • enhancers can be utilized to increase the availability of free radicals.
  • hydrogen peroxide can also provide such free radicals or be used to enhance the production of free radicals, since exposure of the hydrogen peroxide to the catalyst in the presence of light energy also releases free radicals.
  • the released free radicals will react to degrade the contaminants within the solid material.
  • Other suitable enhancers known to those skilled in the art can also be utilized.
  • Various sources of light energy can be utilized, including natural or artificial. Natural sunlight, UV light, sunlamps, etc., used individually or in concert, can provide the required light energy to activate the catalyst for production of the free radicals.
  • a means for removing the by-products of degradation such as volatiles from PCBs degradation.
  • This can comprise any suitable means, such as a granular activated carbon filter.
  • FIG. 1 there is shown an on-site schematic for the photocatalytic degradation of PC3- contaminated sediments and water.
  • a suction dredge 14 or other delivery system transports contaminated sediments 10 which underly water 12 to a photoreactor 20.
  • the contaminated sediments may, for example, be at the bottom of a pond, lake or river.
  • Titanium dioxide catalyst 16 is added to the contaminated sediments as they are transported to the photoreactor 20.
  • a solar or artificial light source 18 is placed over the photoreactor 20, and within the photoreactor 20, water 22 overlies the removed contaminated sediments 24.
  • the process according to the subject invention involving agitation and simultaneous exposure to catalyst and light energy, then takes place in the photoreactor.
  • FIG. 2 there is shown a cross- sectional schematic of an " in-situ process for photocatalytic degradation of PCB-contaminated sediments.
  • a body of water 26 is selected in which a layer of contaminated sediments 28 overlies clean sediments 30, with a layer of shallow water 32 overlying both.
  • a portion of the body of water 26 is encased by a large diameter caisson 44 which is driven or vibrated through the sediments.
  • Solar light or artificial light 40 is emitted through a transparent layer 34 or from within the caisson and titanium dioxide is introduced to the slurry created by the suction dredge 38 via metering pumps 36.
  • Produced volatiles are trapped and treated at 42, a granular activated carbon trap.
  • the system is operated until sufficient treatment is affected and then the caisson is removed and relocated to treat another area.
  • a large diameter steel cylinder or caisson 44 is driven or vibrated using standard construction techniques through the layer of contaminated sediments 28 into the uncontaminated sediments 30.
  • the sediments are situated below shallow waters 32.
  • a pumping system or dredge 38 is used to agitate the sediments to create a sediment/ ater slurry and to maintain the suspension.
  • the catalyst is introduced as a fine powder with the use of metering pumps 36.
  • the steel cylinder is covered with a transparent layer of plastic or glass 34 to allow sunlight penetration. Artificial sunlight or UV lamp energy sources can also be used to enhance the process. All produced gases and volatilized contaminants are collected and passed through a granular activated carbon filter 42 and then returned to the cylinder to assist with maintaining the suspension. The agitation of the sediments is controlled to maintain the optimal concentration of suspended sediments to maximize light and catalyst contact. Although a negative atmosphere will be maintained during the treatment process, the cylinder will be accessible through a hermetically sealed hatch to enable maintenance and sampling.
  • the suction pump (dredge) will be used to carry the suspended sediments to a photoreactor which is located in proximity to the caisson or enclosure system (see Fig. 1) . After treatment the sediments can be returned to the cylinder, allowed to settle and once settling has occurred, the cylinder can be removed and used to treat other areas requiring decontamination.
  • Fig. 3 shows another embodiment of the invention, in which the reactor consists of a series of parallel photoreactors 46, 48, 50 that are connected in series to provide multiple levels of exposure and treatment.
  • the first photoreactor 46 will receive contaminated sediments from a dredge, backhoe, or other delivering device.
  • the sediment slurry will be discharged directly into photoreactor 46 which will be continuously agitated to allow thorough separation of the suspended and bottom sediment fractions. Titanium dioxide catalyst, will be introduced at the time the slurry is discharged to photoreactor 46.
  • This photoreactor is designed to maximize exposure to artificial UV and/or sunlight sources and as the agitation proceeds, the suspended fraction will be irradiated at the slurry/air surface to promote photocatalysis.
  • the suspended sediment fraction will be slowly discharged 52 to photoreactor 48. This phase of the separation will be timed to optimize the discharge rates with the degree of photodegradation. Slow discharge from 46 to 48 will continue until the suspended sediment fraction is thoroughly transferred to photoreactor 48 which will expose the bottom sediments in photoreactor 46 to the light source(s) . Agitation of the bottom sediments in photoreactor 46 by a tank baffle or other system will be continued to spread the bottom sediments to maximize contact with the catalyst and radiation to promote photocatalytic degradation.
  • the suspended sediment fraction will be gravity discharged 54 or pumped to another photoreactor 50 for continual treatment and for eventual removal and/or discharge 58. Once the bottom sediments in photoreactor 46 have been adequately treated, they will be removed for alternative treatment or disposal 56.
  • a holding tank 64 can be used for sediment settling and make up water can be pumped back to 46 if needed.
  • the entire system of reactors, 46, 48, and 50, are covered by transparent material and artificial light can also be added.
  • gases produced during the treatment process will be drawn through an adsorbing/absorbing filter and the exhaust gases may be utilized to disperse the water/sediment mixture to maintain suspensions.
  • the treatment system is designed to allow continuous recirculation 62 thereby enabling extended times of exposure to the catalyst and to sunlight.
  • Design considerations can also include condensation and water vapor separation.
  • the fine-grained sediment portion will be moved through each treatment chamber by a mechanically operated paddle section.
  • the paddle 66 or "agitation board” can be operated in two modes.
  • photoreactor 46 the suspended sediment is kept in suspension by the back and forth motion of the board. If it is decided to move the bottom sediment to one end of the photoreactor for collection and removal, the board is operated in a lower position to come in contact with the bottom of the vessel and drag the bottom sediments to either end of the photoreactor. While in the lowered position, the door can also be used to agitate the bottom sediments as well as to maximize exposure to the catalyst and light energy.
  • Figs. 5 and 6 depict the design for another embodiment of an onsite photoreactor.
  • the reactor unit 72 is designed to batch treat bottom and suspended sediments, and has an outer spill containment tank 70.
  • the bottom sediments are e ersed under water.
  • the sediments will be continually mixed using a series of baffles 74 which will be designed and operated to thoroughly stir the sediments to continually mix and expose the sediments to the light which will be sunlight and a series of artificial lamp sources.
  • a wormscrew 78 or other mechanism will be used to mix and carry sediment out of the reactor.
  • the sump 76 and wormscrew 78 illustrate a method to remove the treated sediment from the reactor to minimize the removal of water.
  • the sediments will be moved along the bottom of the reactor with the use of the baffles 74.
  • the sump and wormscrew can also be used to remove the partially dewatered sediment and to collect samples for analysis during operations.
  • a double sump/wormscrew system for each reactor will provide redundancy as well as accelerate removal of the treated sediment.
  • Fig. 7 shows an alternative design in which the baffles 80 are rotated on boom 82, agitating the sediment beneath the light source 84. The sediment is removed via wormscrew 86.
  • Fig. 8 shows a series of photoreactors 92, 94, 96 which are interconnected in spill containment housing 90".
  • the contaminated sediment is delivered to photoreactor 92.
  • Photoreactor 92 separates the coarser grained material from the finer, suspended sediment.
  • the coarser material is transported to reactor 98, within spill containment housing 100, for treatment and eventual discharge to a disposal site 102.
  • the suspended (fine-grained) material is discharged to reactor 94 and then to reactor 96 for continued treatment and eventual discharge to the disposal site 104.
  • pretreated sediments can be ground and disaggregated in a grinder 122 to reduce the size of clay clumps, grind twigs, leaves and other vegetative matter.
  • the ground material can then be placed in a dispersal chamber or mixing tank 124 that will further segregate the sediments based on size (specific gravity) .
  • the sediment will be segregated into two size fractions and after separation, transferred to two separate reactors, treatment ponds or tanks 128 and 130 where titanium dioxide 126 will be introduced through a metering system.
  • the coarse fraction will be placed in reactor 130, and the fine fraction will be placed in reactor 128.
  • the two separated fractions will be subjected to varying times of exposure to sunlight and/or artificial sunlight in the presence of finely ground titanium dioxide in the reactors. In order to maximize exposure to sunlight and contact with the catalyst, the suspension will be continually agitated as it is carried through the reactors.
  • gases produced during the treatment process will be drawn through a granular activated carbon filter 132 and the exhaust gases 140 will be utilized to disperse the water/sediment mixture.
  • the treatment system has been designed to allow continuous recirculation through reactor settling tanks 134 and 136, thereby enabling extended times of exposure to the catalyst and to sunlight. Treated and decontaminated effluent 138 can be discharged from the reactor settling tanks 134 and 136.
  • This example details the photodecomposition of PCBs using titanium dioxide as a catalyst and promoted by sunlight in a clay suspension and contaminated sediment.
  • the titanium dioxide catalyzed photolytic process destroyed almost 80% of the total PCBs in the clay suspension after 4 hours of radiation, and greater than 50-60% of total PCBs were destroyed in the sediment suspension within 6 hours.
  • the AroclorTM 1248 standard was obtained from Analabs (North Haven, Conn.), and the stock solution was made by dissolving 32.2 mg of the Aroclor into 100.0 ml of optima-grade hexane (Fisher Sci. ,
  • PCB-Clav Suspension Five grams of kaolinite were mixed with 25.0 ml of Aroclor 1248 hexane stock solution. The slurry was dried at room temperature for 24 hours before suspending into 500 ml of deionized water. A teflon-coated magnetic bar was used to stir the suspension for two days and then 10.0 ml of the suspension was pipetted into an Erlen eyer flask with 490 ml of water to make up a PCB-clay working solution.
  • the final PCB-clay suspension contained 0.2 g/L clay and 0.32 mg/L PCBs.
  • Sediment Suspension Five grams of Grasse River sediment (wet) were suspended into 2 liters of water. After two hours of continually stirring, the large pieces and sands were allowed to settle and after five minutes, the suspension was decanted and the large fraction discarded. The suspended fraction was collected and brought to the final volume of- 2.0 L. The suspension was then divided into 5 equal portions of 400 ml.
  • Irradia ion One ml of titanium dioxide suspension at a concentration of 50 g/L was pipetted into those samples in which the catalyst was used. Samples that did not contain titanium dioxide served as experimental blanks.
  • hexane solution was then transferred to a Kuderna-Danish condenser and concentrated on a steam bath.
  • the concentrated hexane solution was passed through a 4% deactivated Florisil column to remove polar compounds. After Florisil clean-up, the hexane solution was again concentrated and then adjusted to the final volume for chromatographic analysis.
  • Experimental controls and blanks were used under the same conditions for each experimental treatment and they were extracted with the same procedure.
  • PCB concentrations were determined on a gas chromatograph (Perkin-Elmer, Sigma 2000) with an electron capture detector (ECD) .
  • ECD electron capture detector
  • the temperature program was 100°C for 2 minutes, then increased to 160° at a rate of 10"/minute and further increased at 3"/minute to the final 270°,
  • the GC was equipped with a 0.20 mm x 25 m "Ultra 2" HP glass capillary column.
  • PCB standard solution was prepared and provided by the New York State Department of Health.
  • a personal computer equipped with a HP/ChemStation software package through an interface was used to collect and analyze the chromatographic data.
  • Integrated chromatographic peak area sums were utilized to indicate relative changes in PCB concentration. Relative changes in single congener concentrations were done in the same manner.
  • a GC (HP 5890II)/MSD (HP 5971) was used for congener identification.
  • the entire process was controlled by a HP 486 PC with a software package (HP G1034B) for GC/MSD.
  • HP G1034B software package
  • SIM Selective Ion Monitoring
  • PCB-Clay Suspension The results of photocatalytic decomposition of PCBs in the clay suspension are illustrated in Fig. 10 and Table 1.
  • the blank represents no titanium dioxide; Control I represents no titanium dioxide and in the dark; and Control II represented titanium dioxide but in the dark. It was observed that there were only slight differences in total PCB concentrations among the Aroclor-clay suspension, wrapped Aroclor-clay suspension, and the wrapped Aroclor-clay-titanium dioxide suspension. Total PCB concentrations dramatically decreased in the clay suspension in the presence of titanium dioxide. After 2 hours irradiation, only 23% of the PCB remained in the suspension and only 19% of the total PCBs was recovered in the sample exposed to sunlight for 4 hours.
  • the congeners which appear before 23 minutes retention time in the chromatograph usually have 3 or less chlorines and the congeners with retention times longer than 30 minutes usually contain 5 or more.
  • the higher chlorine content congeners appeared to be of much lower reactivity during the photocatalytic process.
  • Figures 14-19 are the chromatograms from the GC/MS which was configured to search for certain ion pairs in the sediment extract.
  • Figs 14-16 illustrate the chromatograms of congeners with 1 to 3 chlorines and
  • Figs 17-19 illustrate the congeners with 4 or more chlorines.
  • the general trend relative to the experimental blank (Fig. 14) is from high to low with increasing retention times. This tendency shifts in the opposite direction for Fig. 15 and 16, which are from the samples subjected to irradiation for 2 and 6 hours, respectively.
  • this phenomena is not observed in the higher chlorinated congeners as illustrated in Figs 17-19.
  • Escherichia coli was used as an index to assess the disinfection of water-borne microorganisms by sunlight irradiation in the presence of a titanium dioxide (TiO,, anatase) photocatalyst. With 23 minutes irradiation, more than 99% of the spiked E. coli was inactivated in water solutions. No significant changes in E. coli were observed in the irradiated control with no titanium dioxide added, or in the water solution that was not irradiated but contained titanium dioxide. The inactivation of E. coli was attributed to the generation of free hydroxyl radicals during irradiation of titanium dioxide in the aqueous solution.
  • Titanium dioxide used in this study was obtained from Degussa with a dominant mineralogical form of anatase. Titanium dioxide was suspended in distilled-deionized water at a concentration of 100 g/L as the stock suspension.
  • Escherichia coli (Wards, #85W0400) was grown on a nutrient agar slant at 37°C for 48 hours. Cells were suspended in 10.0 ml of sterile deionized water to give an optical density reading of 0.06 at 540 nm using a spectronic 20 colorimeter. Duplicate experimental and control systems were prepared by adding 9.0 ml of the cell suspension to 891 ml of sterile deionized water and distributing to each of eight sterile 250 ml Erlenmeyer- screen cap flasks. A batch study was carried out with duplicate 250 ml Erlenmeyer flasks made of Pyrex glass. A sterile teflon coated magnetic stirring bar was used in each S94/12357
  • the samples irradiated with titanium dioxide were diluted to 10, 100, 1000, and 10000 times before one ml of diluted solution was transferred to the petri plates.
  • the experimental controls and blanks were diluted to 100, 1000, and 10000 times original concentrations.
  • the titanium dioxide suspension without spiked E. coli was cultured with the original and 10 times diluted solutions. Triplicate plates were incubated at 37°C for 48 hours.
  • the total averaged active cell density in the 10 and 100 times diluted solutions are 23-27 and 2-3 cell/ml, respectively. These numbers are less than 1% of the total cell density obtained from the averaged numbers from the experimental controls and blanks.
  • sunlight did not affect the cell density in the aqueous solution in this short period of irradiation.
  • E. coli cells were not disinfected in titanium dioxide suspension unless exposed to sunlight.
  • the densities of active cells in the two experimental controls were about the same.
  • Blank no Ti0 2 added; no (I) TNTC 2 164 ( ⁇ 7) 18(4-4) irradiation (ID TNTC 162 ( ⁇ 12) 21( ⁇ 1)
  • Control l TiO, (0.1 g/1) ; no (I) TNTC 169 ( ⁇ 6) 11( ⁇ 2) irradiation (ID TNTC 179 ( ⁇ 9) 20 ( ⁇ 2)
  • Control 2 no TiO, added; irradiation (I) TNTC 157 ( ⁇ 10) 13 (4-3) 23 min. (ID TNTC 146 ( ⁇ 9) 13 ( ⁇ 1)

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  • Treatment Of Water By Oxidation Or Reduction (AREA)

Abstract

La présente invention concerne un appareil et un procédé pour la dégradation/destruction photocatalytique de contaminants dans des solides. L'appareil peut être prévu pour une utilisation sur place ou à distance. Il comprend généralement un réacteur (20) dans lequel le matériau solide est simultanément exposé à un catalyseur pouvant être photoactivé (16) et une énergie lumineuse (18). Le réacteur comprend un moyen pour agiter le matériau solide (38) tel qu'un système de chicanes, pour maximiser l'exposition du matériau solide au catalyseur et à l'énergie lumineuse. Le procédé selon l'invention utilise la photocatalyse pour dégrader les contaminants dans le matériau solide ou sorbés sur ce dernier. Le matériau solide peut être séparé en une partie en suspension dans une source aqueuse de radicaux libres et en une partie déposée au fond. L'exposition d'un catalyseur à l'énergie lumineuse provoque la production de radicaux libres qui, une fois, en contact avec les contaminants dans la partie en suspension ou dans la partie déposée au fond , réagissent avec les contaminants pour les dégrader.
PCT/US1994/012357 1993-10-27 1994-10-27 Destruction photocatalytique de contaminants dans des solides WO1995011749A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU80938/94A AU8093894A (en) 1993-10-27 1994-10-27 Photocatalytic destruction of contaminants in solids

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US14413493A 1993-10-27 1993-10-27
US08/144,134 1993-10-27

Publications (1)

Publication Number Publication Date
WO1995011749A1 true WO1995011749A1 (fr) 1995-05-04

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PCT/US1994/012357 WO1995011749A1 (fr) 1993-10-27 1994-10-27 Destruction photocatalytique de contaminants dans des solides

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AU (1) AU8093894A (fr)
WO (1) WO1995011749A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1583601A4 (fr) * 2003-01-13 2006-04-05 Engineering Performance Soluti Charbon active magnetique et elimination de contaminants de flux de fluide
US7638039B2 (en) 2004-06-15 2009-12-29 Cormetech, Inc. In-situ catalyst replacement
CN103926358A (zh) * 2014-03-17 2014-07-16 湖南工程学院 一种模拟水体环境中活性氧物种对芳香性农药转化机制的方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4793931A (en) * 1987-09-10 1988-12-27 Solarchem Research, A Division Of Brolor Investments Limited Process for treatment of organic contaminants in solid or liquid phase wastes
US4861484A (en) * 1988-03-02 1989-08-29 Synlize, Inc. Catalytic process for degradation of organic materials in aqueous and organic fluids to produce environmentally compatible products
US4978508A (en) * 1988-09-01 1990-12-18 Pacific Resource Recovery Corp. Method and apparatus for soil decontamination

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4793931A (en) * 1987-09-10 1988-12-27 Solarchem Research, A Division Of Brolor Investments Limited Process for treatment of organic contaminants in solid or liquid phase wastes
US4861484A (en) * 1988-03-02 1989-08-29 Synlize, Inc. Catalytic process for degradation of organic materials in aqueous and organic fluids to produce environmentally compatible products
US4978508A (en) * 1988-09-01 1990-12-18 Pacific Resource Recovery Corp. Method and apparatus for soil decontamination

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1583601A4 (fr) * 2003-01-13 2006-04-05 Engineering Performance Soluti Charbon active magnetique et elimination de contaminants de flux de fluide
US7879136B2 (en) 2003-01-13 2011-02-01 Engineering Performance Solutions, Llc Magnetic activated carbon and the removal of contaminants from fluid streams
US7638039B2 (en) 2004-06-15 2009-12-29 Cormetech, Inc. In-situ catalyst replacement
CN103926358A (zh) * 2014-03-17 2014-07-16 湖南工程学院 一种模拟水体环境中活性氧物种对芳香性农药转化机制的方法

Also Published As

Publication number Publication date
AU8093894A (en) 1995-05-22

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