USOO5232484A United States Patent (19) 11 Patent Number: 5,232,484 Pignatello 45 Date of Patent: Aug. 3, 1993

(54). DEGRADATION OF BY Waste Disposal Proceedings EPA/600/9-85/030, pp. FERRC REAGENTS AND PEROXDEN 72 to 85. THE PRESENCE OF LIGHT Johnson, L. J., and Talbot, H. W., 39 Experimentia 1236-1246 (1983). 75 Inventor: Joseph J. Pignatello, Hamden, Conn. Mill, T., and Haag, W. R., Preprints of Extended Ab 73 Assignee: The Connecticut Agricultural stracts, 198th Nat. Meeting Amer. Chem. Soc. Div. Experiment Station, New Haven, Env, Chem., A.C.S., Washington, 1969, paper 155, pp. Conn. 342-345. 21 Appl. No.: 744,365 Munnecke, D. M., 70 Residue Rev. 1-26 (1979). Murphy, A. P., et al., 23 Environ. Sci. Technol. 166-169 22 Filed: Aug. 13, 1991 (1989). 51 int. Ci...... A01N 37/38; A01N 43/70; Nye, J. C., 1985 National Workshop on Waste CO2F 1/72 Disposal Proceedings EPA/600/9-85/030 pp. 43 to 52 U.S.C...... 588/206; 210/759; 480. 588/207; 588/210 Plimmer, J. R., et al., 19 J.Agr. Food Chem. 572-573 58 Field of Search ...... 71/117, 116,93; (1971). 210/749, 758, 759 Schmidt, C., 1986 National Workshop on Pesticide Waste Disposal Proceedings EPA/600/9-87/001, pp. 56) References Cited 45 to 52. U.S. PATENT DOCUMENTS Sedlak, D. L. and Andren, A. W., 25 Environ. Sci. 3,819,516 6/1974 Murchison et al...... 422A24 Technol. 777-782 (1991). 4,569,769 2/1986 Walton et al. . Watts, R. J., et al., Extended Abstracts if 156, 198th 4,585,753 4/1986 Scott et al. . ACS Meeting, Env. Chem. Div., 1989, pp. 346-349. Wei, T. Y., et al., J. Photochem. Photobiol. A: Chem., OTHER PUBLICATIONS 55: 115-126 (1990). Skurlatov, Y. I. J. Agric. Food Chem. 31: 1065-1071, 1983. Primary Examiner-Allen J. Robinson Larson, R. A. "Sensitized Photodecomposition of Or Assistant Examiner-S. Mark Clardy ganic Compounds Found in Illinois Wastewaters', Attorney, Agent, or Firm-St. Onge Steward Johnston & HWRIC-RR-045, May 1990. Reens Bailin, L. J., et al., 12 Environ. Sci. Technol. 673-679 57 ABSTRACT (1978). Barbeni, M., et al., 16 Chemosphere 2225-2237 (1987) at A method for mineralizing pesticides, notably aromatic 2229 and Figure 4 on 2232. pesticides, using ferric ion in an acid aqueous solution at Ehart, O. R. 1985 National Workshop on Pesticide room temperature is disclosed. In a preferred embodi Waste Disposal Proceedings EPA/600/9-85/030, pp. 2 ment, the ferric ion is employed in the presence of hy to 11. drogen peroxide; degradation occurs in the light or in Eul, W., et al., “Hydrogen Peroxide-Based Treatment the dark, although light accelerates the degradation. Technology for Hazardous Waste," Emerging Tech The method also is functional in the absence of hydro nologies In Hazardous Waste Management, ACS Sym gen peroxide, but light and oxygen is required in this posium No. 422, 1990, 1-35 at 29. method. Preferred degradation methods are conducted Ferguson, T. L., and Wilkinson, R. R. in Krueger, R. in the presence of hydrogen peroxide and light, and in F., and Seiber, J. N. eds, Treatment and Disposal of the absence of large concentrations of organic solvents, Pesticide Wastes, ACS, 1984, Chapter 11, pp. 181 to chloride, and sulfate. 191. Honeycutt, R. C., 1985 National Workshop on Pesticide 13 Clains, 11 Drawing Sheets OO

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ECG REC 6 5,232,484 1 2 Iron hydroxide finely dispersed on inorganic supports DEGRADATION OF PESTCDES BY FERRC that are unreactive to HO, including silica and mont REAG ENTS AND PEROXDE IN THE PRESENCE morillonite clay, have been disclosed to improve the OF LIGHT efficiency of waste water treatments using H2O2 (Mill, T., and Haag, W. R., Preprints of Extended Abstracts, BACKGROUND OF THE INVENTION 198th Nat. Meeting Amer. Chem. Soc., Div. Env. This invention relates to the degradation of organic Chen., A.C.S., Washington, 1969, paper 155, pp. pesticides, notably aromatic compounds such as chlori 342-345). Phenol has been photocatalytically oxidized nated aromatics, by ferric reagents to form inorganic in the presence of hydrogen peroxide and titanium diox Wastes. 10 ide powders in the presence and absence of ferric ions Chlorinated hydrocarbon, organophosphorus, or (Wei, T.Y., et al., J. Photochen. Photobiol. A. Chem, 55: ganonitrogen, organometallic, and the like pesticide 115-126 (1990). Dilute aqueous formaldehyde waste compounds number among the hazardous wastes that solutions have been neutralized by ferric chloride and require special methods for disposal because of their hydrogen peroxide in a process developed for treating toxic, refractory, or persistent properties. Many of these 15 Bureau of Reclamation reverse osmosis desalting mem compounds that do not degrade pose a threat to biota brane storage solutions (Murphy, A. P., et al., 23 Envi and/or human populations. Concern about the potential ron. Sci Technol. 166-169 (1989). However, Barbeni, hazards associated with the compounds has resulted in M., et al., found the addition of ferric ions instead of numerous recent laws and policies that require the ferrous inconsequential in the chemical degradation of cleanup of contaminated soil, sediments, surface water, 20 chlorophenols by Fenton's reagent (16 Chemosphere and wastewater. 2225-2237 (1987) at 2229 and FIG. 4 on 2232). A number of disposal techniques have been suggested SUMMARY OF THE INVENTION for various types of these toxic chemicals (see reviews It is an object of the present invention to provide a by Munnecke, D. M., 70 Residue Rev. 1-26 (1979) and 25 new method for degrading pesticides. It is another ob Ehart, O.R., 1985 National Workshop on Pesticide Waste ject of the present invention to provide a method for Disposal Proceedings EPA/600/9-85/030, pages 2 to 11 decontaminating equipment. It is a further object of the . Physical methods include entrapment, burial, adsorp present invention to provide a degradation method that tion, flocculation, and the like (reviewed by Nye, J. C., employs environmentally benign and inexpensive rea 1985 National Workshop on Pesticide Waste Disposal 30 gents and equipment, and yields virtually complete Proceedings, cited above, pages 43 to 480); an example is mineralization of the pesticides. the activated charcoal detoxification of pesticides dis These and other objects are achieved by the present closed by Scott in U.S. Pat. No. 4,585,753. Chemical invention, which describes methods of degrading pesti methods include oxidation, reduction, hydrolysis, con cides of the type having a formula containing more than jugation, irradiation, and the like (reviewed by Honey 35 one carbon atom, notably aromatics, under mild condi cutt, R. C., 1985 National Workshop on Pesticide Waste tions using ferric reagents. Preferred embodiments Disposal Proceedings, cited above, pages 72 to 85); exam achieve substantial mineralization of the pesticides by ples include incineration (discussed by Ferguson, T. L., contacting them in an oxygenated acidic aqueous solu and Wilkinson, R. R., in Krueger, R. F., and Seiber, J. tion with ferric ion in an amount and for a time effective N., eds., Treatment and Disposal of Pesticide Wastes, to achieve substantial mineralization. Degradations con ACS, 1984, chapter 11, pages 181 to 191), thiosulfate ducted in the dark require an oxidizing agent such as a oxidation using hydrogen peroxide and copper dis peroxide; hydrogen peroxide is preferred. In light, per closed by Walton and Rutz in U.S. Pat. No. 4,569,769, oxide (or other oxidizing agent) is not required, but it and the microwave plasma detoxification process de greatly accelerates degradation. In one embodiment, scribed in Bailin, L. J., et al., 12 Environ. Sci Technol. 45 pesticides are degraded in aqueous solutions having a 673-679 (1978). Biological methods include degradation pH of about 1.5 to about 3.5, preferably about 2.5 to by enzymes and microorganisms (Schmidt, C., 1986 about 3.0, by ferric ion in light for a time effective to National Workshop on Pesticide Waste Disposal Proceed achieve substantial mineralization. In another embodi ings, EPA/600/9-87/001, pages 45 to 52, and Johnson, ment, pesticides are degraded in aqueous solutions hav L. M., and Talbot, H. W., 39 Experientia 1236-1246 50 ing a pH of about 1.5 to about 3.5, preferably about 2.5 (1983)). to about 3.0, by contacting the pesticide with a compo Waste treatment systems employing Fenton's rea sition comprising ferric ion and peroxide in the presence gent, i.e., hydrogen peroxide containing ferrous ions, or in the absence of light. Preferred methods are con have been suggested for the degradation of chloroben ducted in absence of large concentrations of organic zene, phenols, formaldehyde, s-triazine and 55 solvents, chloride, and sulfate. octachloro-p-dibenzo-dioxin (Plimmer, J. R., et al., 19.J. Agr. Food Chem, 572-573 (1971), Watts, R. J., et al., BRIEF DESCRIPTION OF THE FIGURES Extended Abstracts #198th ACS Meeting, Env. Chem. FIGS. 1 and 2 show the ferric reagent-catalyzed Div., 1989, pages 346-349, and Sedlak, D. L., and An oxidation of 2,4-dichlorophenoxyacetic acid using the dren, A. W., 25 Environ. Sci Technol. 777-782 (1991)). method described in Example 1. The concen Treatment of hazardous wastes with Fenton's reagent tration is 0.1 mM and the iron concentration is 1.0 mM. "has its limitations. Non-polar organic molecules like FIG. 1 is the perchlorate solution 0.2M in sodium per polycyclic aromatics, benzene, mesitylene or hydrocar chlorate and 2.5 mM in peroxide. FIG. 2 is the sulfate bons with long carbon chains are especially difficult to solution, is 10 mM in peroxide. destroy" (Eul, W., et al., "Hydrogen Peroxide-Based 65 FIG. 3 shows the ferric reagent mineralization of Treatment Technology for Hazardous Waste," Emerg ring-uniformly labelled(UL)-C-2,4-dichlorophenox ing Technologies in Hazardous Waste Management, ACS yacetic acid at a pH of 2.8 as described in Example 1. Symposium No. 422, 1990, 1-35 at 29). The reaction mixture contains 0.2 mM (1 x 10 disinte 5,232,484 3 4. grations per minute (DPM)/ml) herbicide, 1.0 mM fer FIG. 16 shows the degradation of ring-UL-1C-atra ric ion, 10 mM peroxide and 0.2M sodium perchlorate. zine in the dark with 1 mM ferric perchlorate, 10 mM DCP is 2,4-dichlorophenol. hydrogen peroxide at pH 2.75, and 0.2M sodium per FIG. 4 shows the comparative yields of 14CO2 from chlorate. carboxy-C-2,4-dichlorophenoxyacetic acid in chlo- 5 ride and in perchlorate reaction media at pH 2.75 as set DETALED DESCRIPTION OF THE out in Example 1. The mixtures are 0.1 mM (1 x 10 INVENTION DPM/ml) in herbicide, 1.0 mM in iron, and 10 mM in In the practice of this invention, aqueous, acidic ferric peroxide. reagents are employed to degrade, preferably to sub FIG. 4 plots the ferric-catalyzed decomposition of 10 stantially mineralize, organic pesticides of the type hav the hydrogen peroxide control described in Example 1. ing a formula containing more than one carbon atom, The initial reaction mixture contains 0.99 mM Fe+3, notably aromatics, under mild conditions. Degradation 100 mM H2O2, and 0.2M NaClO4. The kits incorporates reactions carried out in the dark require oxygen and ferric ion and hydrogen ion concentration terms added oxidizing agent such as peroxide. Reactions car FIGS. 7 and 8 show the photo-assisted ferric reagent 15 ried out in light do not require peroxide or other oxidiz degradation of ring-labelled 2,4-dichlorophenoxyacetic ing agent except oxygen, but adding such an agent greatly accelerates the degradation. Preferred ferric acid at pH 2.7 using the method of Example 1. The reagents contain ferric ion and hydrogen peroxide. The reaction is 0.1 mM (1 x 104 DPM/ml) in labelled herbi reaction is preferably carried out at pHs ranging be cide, 1.0 mM in ferric perchlorate, 10 mM in peroxide, tween about 1.5 and about 3.5, more preferably between and 0.2M in sodium perchlorate. Iron and hydrogen about 2.5 and about 3.0. peroxide are present in the reactions plotted in FIG. 7, With an inorganic or organic chelating agent, the with 'a' being bright light and "b', the dark reaction. In reaction can be carried out at higher pH's, such as, for FIG. 8, alpha is bright light and iron alone, beta is bright example, about pH 3.5 to about 6.0. Example chelating light and peroxide alone, and theta is dark with iron 25 agents include gallic acid (3,4,5-trihydroxybenzoic alone. acid), picolinic acid (-2-carboxylic acid), and FIG. 9 shows the photo-assisted ferric reagent miner rhodizonic acid. alization of ring-labelled 2,4-dichlorophenoxyacetic Any acid can be employed to adjust the pH. Pre acid as a function of peroxide concentration in bright ferred acids are perchloric and nitric. light as described in Example 1. Peroxide concentra The ferric reagents employed in the degradation tions vary as follows: A-A 0.1 mM, V-V 0.2 mM, methods of this invention are prepared from ferric salts. V-V 0.4 mM, A-A 0.5 mM, O-O 2 mM, O-O 5 Any water soluble ferric salt can be employed, but mM, and O-D 10 mM. Other conditions are as set out ferric chloride and ferric sulfate are not preferred. Ex for FIGS. 7 and 8 above. ample ferric salts include, but are not limited to, ferric FIG. 10 shows the ferric reagent mineralization of perchlorate, ferric nitrate, ferric citrate, ferric malate, ring-labelled 2,4,5-trichlorophenoxyacetic acid at pH ferric lactate, ferric oxalate, and the like. 2.75. Initial concentrations are 0.175 mM (1 x 10 Where ferric ions are employed to degrade pesticides DPM/ml) in labelled herbicide, 1.0 mM in ferric ion, in the absence of peroxide or other oxidizing agent 10.2 mM in peroxide, and 0.2M in sodium perchlorate. other than oxygen, the ferric salts can be either dis FIGS. 11 and 12 show the photo-assisted ferric rea- 40 solved as solids in aqueous pesticide solutions or added gent degradation of ring-labelled 2,4,5-trichlorophenox to the pesticide as a stock ferric solutions; adding ferric yacetic acid at pH 2.7 using the method of Example 2. solutions is preferred. Where peroxide or other oxidiz The reaction is 0.1 mM in labelled herbicide, 1.0 mM in ing agent is used in concert with ferric ion to degrade ferric perchlorate, 10 mM in peroxide, and 0.2M in pesticides, the agent can be added with the ferric ion or sodium perchlorate. Reactions 'a', 'b', and 'c' all have 45 before or after adding ferric ion. The amounts of added iron and peroxide present; 'a' is carried in the presence ferric salts are not critical in the dark reaction, but in the of bright light, "b", in the dark, and "c", in dim light. light preferred ferric concentrations in the initial degra Alpha denotes a reaction carried out in bright light with dation reaction mixtures range between about 0.2 mM iron alone, beta, bright light and peroxide alone, and to about 2.5 mM. theta is dark with iron alone. SO Certain anions, including chloride and sulfate, inhibit FIG. 13 shows the reaction of 2,4-dichlorophenoxya the degradation reaction at high concentrations. Large cetic acid with hydrogen peroxide and ferrous ion at pH concentrations of organic solvents such as 1.8 as described in Example 3. The reaction is 0.1 mM in also inhibit the reaction. Therefore, the ferric reagents herbicide, 0.99 mM in ferrous sulfate, and 0.96 mM in of this invention are preferably employed in the absence peroxide. 55 of large concentrations of chloride, sulfate, and organic FIG. 14 shows the Fenton oxidation of 2,4-dichloro solvents. phenoxyacetic acid at different pHs (adjusted with sul Degradation of pesticides occurs on incubation of the furic acid) as described in Example 3. The reactions are pesticide with ferric ion in light. In this embodiment, 0.1M in herbicide, 0.246M in ferrous ion, and 0.126 mM pesticides are degraded in aqueous solutions having a in peroxide. DCP is 2,4-dichlorophenol. 60 pH of about 1.5 to about 3.5, preferably about 2.5 to FIG. 15 shows a comparison the ferric reagent of this about 3.0, by contacting the pesticides with ferric ion in invention (Fe+3/H2O2) with Fe+2/H2O2 under optimal light for a time effective to achieve substantial, i.e., at conditions employed for ferric reagent in the mineral least about 25% to about 30%, mineralization. By "min ization of ring-labelled 2,4-dichlorophenoxyacetic acid eralization' is meant conversion of the organic pesticide at a pH of 2.7 as described in Example 3. The reactions 65 to inorganic compounds. are 0.1 mM 1 x 10 DPM/ml in labelled herbicide, 1.0 Bright light is preferred. By "bright” light is meant mM in iron (perchlorate salts), 10 mM in peroxide and light having an intensity of at least about 1.2 mW/cm2 in 0.2M in sodium perchlorate. the visible region (400 to 700 nm) and at least about 5,232,484 5 6 0.035 mW/cm2 in the near ultraviolet (UV, 290 to 385 xylyliminomethyl) amine); amlure (propyl 1,4-benzodi nm). As is illustrated in the Examples to follow, the oxan-2-carboxylate), amoban (diammonium ethylene reaction proceeds in dim light (about 20 times less in bisdithiocarbamate); tetrasul (Animert V-101 TM, 4 tense). Moreover, the reaction proceeds in light of near chlorphenyl 2,4,5-trichlorophenyl sulfide); anthraqui UV wavelength (~300 to ~400 nm). However, even in none (9,10-anthraquinone); diethatyl ethyl (Antor TM, bright light, the degradation reaction can be relatively N-(chloroacetyl)-N-(2,6-diethylphenyl)glycine ethyl slow for some pesticides (e.g., only about 20 to 35% ester); IPSP (Aphidan TM, O,O-diisopropyl-S-ethylsul mineralization in about 10 hours). finyl methyl dithiophosphate); niagramite (Aramite TM, The light reaction may be accelerated by adding an 2(p-tert butylphenoxy)-isopropyl 2-chloroethylsulfite); oxidizing agent other than oxygen such as a peroxide, 10 (Aresin TM, N-(4-chlorophenyl)-N' me preferably hydrogen peroxide. Oxidizing agents include thoxy-N'-methylurea); (Asana TM, (S)- but are not limited to perborate, organoperoxides and cyano(3-phenoxyphenyl)methyl-(S)-4-chloro-alpha (1- hydrogen peroxide. Therefore, peroxide, especially methylethyl) benzene acetate); Aaulam (methyl sul hydrogen peroxide, is a component of preferred ferric fanillylcarbamate); terbucarb (AzakTM, 2,6-di-tert reagents of this invention. 15 butyl-p-tolyl methylcarbmnate); Azithiram TM (bis Peroxide may be added to degradation reaction mix dimethylaminocarbamoyl disulfide); BanairTM (2- tures before, after, or with the ferric ion. Adding perox methoxy-3,6-dichlorobenzene); bensultap (BancolTM, ide after the iron is preferred. Peroxide is preferably S,S'-2-dimethylaminotrimethylene di(benzene-thiosul employed in amounts ranging from about 1 mM to phonate); dimethylamine salt of (Banvel TM, about 500 mM in the mixture. Increasing the peroxide 20 dimethylamine salt of 2-methoxy-3,6-dichlorobenzoic concentration generally increases the rate of mineraliza acid or dimethylamine salt of 3,6-dichloro-o-anisic tion of the pesticides. acid); (Basagran TM, 3-isopropyl-1H-2,1,3- In a preferred embodiment of the invention, pesti benzothiadiazin-4(3H)-one 2,2-dioxide); niclosamide cides are contacted, in an aqueous solution having a pH (Bayluscid TM, 5-chloro-N-(2-chloro-4-nitrophenyl)-2- of about 1.5 to about 3.5, preferably about 2.5 to about 25 hydroxybenzamide compound respectively with 2 3.0, with a composition comprising ferric ion and hy aminoethanol (1:1)); (Baythion TM, 2-(((die drogen peroxide, each in amounts and for a time effec thoxyphosphinothioyl)oxy)imino) benzene-acetoni tive to achieve substantial mineralization of the pesti trile); chlorphoxim (Baythion CTM, 7(2-chlorophenyl)- cide. At least about 25% to 30% mineralization, more 4-ethoxy-3,5-dioxa-6-aza-4-phosphos-phaoct-6-ene-8- preferably about 50% or greater, even more preferably 30 nitrile-4-sulfide); benazolin (4-chloro-2-oxobenzothiazo about 75% or greater, is preferred. Some embodiments lin-3-ylacetic acid); TM (2,2-dimethyl-1,3- achieve about 95% or greater mineralization. The deg benzodixol-4-yl methylcarbamate); benodanil (2-iodo-N radation can proceed in the absence or the presence of phenylbenzamide); exporsan ( TM, S-O,O- light. Light is preferred. diisopropyl phosphorodithioate) ester of N-(2-mercap By the term "pesticide' is meant compounds of the 35 toethyl) benzenesulfonamide); BTC (benzalkonium type having a formula containing more than one carbon chloride, alkyl dimethyl benzylammonium chloride); atom, used to destroy pests, including herbicides, fungi benzomate (JMAF) (benzoximate, ethyl O-benzoyl 3 cides , rodenticides, and the like. Unsatu chloro-2,6 dimeth-oxybenzohydroximate); chlorfen rated pesticides, notably aromatic pesticides, are espe prop-methyl (Bidsin TM, 2-chloro-3(4-chlorophenyl)- cially susceptible to degradation by the ferric reagents methylpropionate); (methyl 5-(2,4-dichloro of this invention. Using the terminology of the Farm phenoxy)-2-nitroben-zoate); (Bladafum TM, Chemicals Handbook 1990, Example pesticides include, tetraethyl thiodiphosphate); sulprofos (Bolstar TM, O but are not limited to flucythrinate/ (Aas ethyl-O-(4-(methylthio) phenyl)-S-propyl phosphorodi tar TM, O,O-diethyl-S-((ethylthio)methyl)phosphoro thioate); bomyl (dimethyl 3-hydroxy glutaconate di dithioate) and cyano(3-phenoxyphenyl)methyl-4-(di 45 methyl phosphate); fenobcarb (BPMC, 2-(1-methylpro fluromethoxy)alpha(1-methyl-ethyl)benzene acetate); pyl) phenyl methylcarbamate); Brodifacoum TM (3-(3- temephos (Abate TM, O,O'-(thiodi-4,1-phenylene)bis (4-bromo(1,1'-biphenyl)-4-yl)-1,2,3,4-tetrahydro-1-nap (O,O-dimethyl phosphorothioate); bromopropylate thalenyl)-4-hydroxy-2H-1-benzopyran-2-one); (Acarol TM, isopropyl 4,4'-dibromobenzilate); aceto Bromadiolone TM (3-(3-(4-bromo(1,1'-biphenyl)-4-yl)- chlor (AcenitTM, 2-chloro-N-ethoxymethyl-6'-ethyla SO 3-hydroxy-1-phenylpropyl)-4-hydroxy-2H-1-benzopy cet-o-toluidide), (2-chloro-6-nitro-3-phenoxy ran-2-one); BromophosTM (O(4-bromo-2,5-dichloro ) (Advantage TM, 2,3-dihydro-2,2- phenyl)-0, 0-dimethylphosphorothioate); bromo dimethyl-7-benzofuranyl (dibutylamino)thio)methyl phosethyl (O-(4-bromo-2,5-dichlorophenyl) O,O-die ); (AgritoxTM), Akton TM thylphosphorothioate); TM (3,5-dibromo (O,O-diethyl O-(2-chloro-1-(2,5-dichlorophenyl) vinyl) 55 4-hydroxybenzonitrile); Bronopol TM (2-bromo-2- phosphorothioate); (2-chloro-2'-6'-diethyl-N- nitropropan-1,3-diol); Buban 37TM (3',5'-dinitro-4-(di (methoxymethyl)-acetanilide), aldoxycarb (2-methyl-2- n-propylamino) aceto-phenone); Butacarb TM (3,5-di-t- methylsulfonyl) propanyl O-((methylamino)carbonyl butylphenyl N-methylcarbamate); ButachlorTM (2- )oxime) clofop-isobutyl (Alopex TM, 2-(4-(4-chloro chloro-2',6'-diethyl-N-(butoxy methyl) acetanilide); phenoxy)-phenoxy)-isobutyl-propionate); alpha-cyper Butonate TM (O,O-dimethyl-2,2,2-trichloro-1-n-buty methrin (cyclopropanecarboxylic acid, 3-(2,2-dichloro ryl-oxethyl phosphonate); Butylate TM (S-ethyl ethenyl)-2,2-dimethyl-cyano (3-phenoxyphenyl)methyl disobutylthiocarbamate--inert safener); bufencarb ester); alpha-napthenylacetic acid, triflumuron (Alsys (BuxTM, amorphous SiO2); (Car tin TM, 2-chloro-N-(((4-(trifluoromethoxyphenyl bamultTM, 3-methyl-5-isopropylphenyl-N-methyl-car )aminocarbonyl) benzamide); (Amiben TM, 65 bamate); TM (1-naphthyl N-methylcarba 3-amino-2,5-dichlorobenzoic acid), DAEP (Ami mate); Carbetamide TM (N-ethyl-2-(((phenylamino)car phosTM, O,O-dimethyl-S-2 (acetylamino)ethyldithio bonyl)oxy) propanamide(D)-isomer) TM phosphate); (N-methylbis(2,4- (2,3 dihydro-2,2-dimethyl-7-benzofuranyl methylcarba 5,232,484 7 8 mate); Carboxin TM (5,6-dihydro-2-methyl-N-phenyl chloride); TM (O,O-dimethyl-S-(N-methyl 1,4-oxathiin-3-carboxamide); barban (Carbyne TM, 4 carbamoylmethyl) phosphorodithioate); Dimethyl chloro-2-butynyl m-chlorocarbanilate); Phthalate TM; Diphenamid TM (N N-dimethyl-2,2- hydrochloride (CarzolTM, (3-dimethylamino-(me diphenylacetamide); dipan (Diphenatrile TM); Di thyleneimino phenyl))N-methylcarbamate hydrochlo phenylamine TM; TM (O,O-diethyl S-(2- ride); pyrocatechol (CatecholTM, O-Dihydroxyben (ethylthio)ethyl)phosphoro-dithioate); oxydisulfoton zene); Cellocidin TM (acetylene dicarboxamide); bequi (Disyston STM, O,O-diethyl S-(2-(ethylsulfinyl) ethyl) nox (Ceredon TM, 1,4-benzoquinone N'-benzoylhydra phosphorodithioate); DitalinfosTM (O,O-diethyl zone oxime); Chlomethoxynil TM (2,4-dichlorphenyl phthalimido-phosphonothioate); Dithianon TM (5,10 3-methoxy-4-nitrophenyl-ether); Chloranil TM (2,3,5,6- O dihydor-5,10-dioxonaphtho(2,3b)-p-dithin-2,3-dicar tetrachloro-1,4-benzoquinone); Chlorbenside TM (p- bonitrile); Diuron TM (3-(3,4-dichlorophenyl)-1,1- chlorobenzyl p-chlorophenyl sulfide); Chlor dimethylurea--N'-(3,4-dichlorophenyl)-N,N-dime dimeform TM (N'-(4-chloro-o-tolyl)-N,N-dimethyl-for thylurea); 2-phenylphenol (Dowicide 1 TM, 99% ortho ma-midine); Chlorfenson TM (4-chlorophenyl-4-chloro phenylphenol); Dowicide ATM (97% Sodium o benzene sulphonate); Chlorfensulphide TM (4- 15 phenylphenate); thiocarbazil (Drepamon TM, S-benzyl chlorophenyl 2,4,5-trichlorophenylazo sulphide); chlor N,N-di-sec-butylthiolcarbamate); (Dyfona flurecol-methyl ester (Chlorfurenol TM, methyl 2 te TM, 0-ethyl-S-phenylethylphosphonodithioate); Edi chloro-9-hydroxyfluorene-9-carboxylate, methyl-9- fenphosTM (0,ethyl S.S.-diphenyl phosphorodithioate); hydroxyfluorene-9-carboxylate); ChlormephosTM (S- isoxaben (E1-107 TM, N-(3-(1-ethyl-1-methylpropyl)-5- chlornethyl-O,O-diethyl phosphoro-dithioate); Chlo 20 isoxazolyl)-2,6-dimethoxybenzamide); dioxacarb (Elo rophacinone TM (2-((p-chlorophenyl)phenylacetyl)-1,3 cron TM, 2-(1,3-dioxalan-2-yl)phenyl-N-methylcarba indandione); Chlorophenoxy Propionic Acid TM (2-(3- mate); TM; alpha-chlorohydrin (Epi chlorophenoxy)-propionic acid); Chlorotoluron TM bloc TM, 3-chloro-1,2-propanediol); EPNTM (O-ethyl (N'-(3-chloro-4-methylphenyl)-N-'-dimethyl ); 0(4-nitrophenylphenylphosphonothioate); buturon (Ep Chloroxynil TM (3,5-dichloro-4-hydroxybenzonitrile); 25 tapur TM); eptam (EPTCTM, S-ethyl dipropylthiocar Chlorphoxim TM (isopropyl m-chlorocarbanilate); bamate); Ethiolate TM (S-ethyl diethylthiocarbamate); Chlorpropham TM (mixture of 3 isomers: (1) O-2,5- TM (0,0,0,0-tetraethyl SS-methylene bis (phos dichloro-4-(methylthio)phenyl phosphorothoic acid phorodithioate); Ethoprop TM (0-Eehy S.S.-dipropyl O,O-diethyl ester (2) 0,2,4-dichloro-5-(methylthio)phe phosphorodithioate); chlorfenac (Fenatrol TM, (2,3,6- nyl phosphorothoic acid O,O-diethyl ester (3) 0,4,5- 30 trichlorophenyl) acetic acid); Fenfuram TM (2-methyl dichloro-2-(methylthio) phenyl phosphorothoic acid furan-3-carboxanilide); Fenoxaprop-Ethyl TM O,O-diethyl ester); chlornitrofen (CNPTM, 2,4,6-tri ((-)-ethyl 2-(4-((6-chloro-2-benzoxazolyl) oxy)- chlorophenyl-4-nitrophenyl ether); CGA-92194 (Con phenoxy)propanoate); TM (ethyl (2-(4- cep IITM, N-(1,3-dioxolan-2-yl-methoxy)-iminoben phenoxyphenoxy)ethyl)carbamate); Fen zene-acetonitrile); Conen TM (O-butyl-S-benzyl-S- 35 propimorph TM (-)-cis-4-(3-tert-butylphenyl)-2- ethyl phosphorodithioate); Coumochior TM; 4 methylpropyl)-2,6-dimethylmorpholine); TM CPATM (parachlorophenoxyacetic acid); (O,O-dimethyl 0-(3-methyl-4-(methylthio) phenyl)- (Croneton TM, 2-(ethylthiomethyl) phenyl methylcar phosphorothioate); Fenuron TM (3-phenyl-1,1-dime bamate); CrotoxyphosTM (dimethyl phosphate of al thylurea); Fenvaler ate TM (CRS)-alpha-cyano-3- pha-methylbenzyl 3-hydroxy-cis-crotonate); profenfos 40 phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbuty (Curcacron TM, O-(4-bromo-2-chlorophenyl)-O-ethyl rate); Ferbam TM (ferric dimethyldithiocarbamate); S-propyl phosphorthioate); CyanofenphosTM (4- ethychlozate (Figaron TM, ethyl 5-chloro-3-(1H)- cyanophenylethylphenyl phosphonothioate); Cyan indazolyl-acetate); ethoate-methyl (Fitios B/77 TM, phosTM (O-4-cyanophenyl O,O-dimethyl phosphoro N-ethylamide of O,O-dimethyl dithiophosphorylacetic thioate); mephosfolan (Cytrolane TM, 2-(diethoxyphos 45 acid); flurecol-n-butylester (Flurecol TM, n-butyl-9- phinylimino)-4-methyl-1,3-dithiolane); 2,4-DTM (2,4- hydroxyfluorene-9-carboxylate); tribufos (Folex dichlorophenoxy) acetic acid); DCPA (Dactha TM, 6ECTM, S,S,S-tributyl phosphotrithioate); onethoate dimethyltetrachloroterephthalate); PTMD (Dani (FolimatTM, O,O-dimethyl S-(2-(methylamino)-2- fosTM, S-((p-Chlorophenl) thio)methyl)O,O-diethyl oxothyl) phosphorothioate); furalaxyl (Fongarid TM, phosphorothioate); fensulfothion (DasanitTM, O,O- SO methyl N-2,6-dimethylphenyul-N-furoyl(2)-alaninate); diethyl O-(4-methylsulfinyl)phenyl) phosphorothioate); phosethyl Al (Fosetyl-Al TM, aluminum tris(O-ethyl 2,4-DBTM (4-(2,4-dichlorophenoxy) butyric acid); phosphonate); 3-CPA (Fruitone CPATM, 2-(3-chloro DCNATM (2,6-dichloro-4-nitroaniline); 2,4-DEBTM phenoxy) propionic acid); fuberidazole (Fuberida (2,4-dichlorophenoxyethyl benzoate); butifos zolTM, 202'-furyl)-1H-benzimidazole); Fujithion TM (DEFTM, S,S,S,-tributylphosphorotrithioate); 2,4-D 55 (S-(p-chlorophenyl) O,O-dimethyl phosphoro-thioate); acetate (Defy TM); Demephion-STM (O,O-dimethyl benalaxyl (Galben TM, methyl-N-phenylacethyl-N-2,6- S-(2(methylthio)ethyl) phosphorothioate); Desmedi xylylaninate); Gallic Acid TM ; benazolin (GaltakTM, phan TM (C16H16N2O4); napropamide (Devrinol TM, 4-chloro-2-oxobenzothiazolin-3-ylacetic acid); benz 2-(a-naphthoxy)-N,N-diethylpropionamide); bronsa thiazuron (Gatnon TM, N-2-benzothiazoly)-N'- lans (Diaphene TM, a halogenated salicylanilide); dibu 60 methylurea); phorazetim (Gophacide TM, O,O-bis(p- tyl phthalate; Dicamba TM (2-methoxy-3,6- chlorophenyl) acetimodyl-phosphoramidothioate); dichlorobenzoic acid); Dichlofenthion TM (O-2,4- Griseofulvin TM (7-chloro-4,6-dimethoxycoumaran dichlorophenyl O,O-diethylphosphoro-thioate); Di 3-one-2-spiro-1-(2-methoxy-6' methylcyclohex-2-en chlone TM; TM (2-(2,4-dichlorophenoxy)- 4'-one); EXD (Herbisan #5TM, diethyl dithiobis propionic acid); dichlorprop-PTM ((R)-2-(2,4-dichloro 65 (thinoformate): Hexachlorophene TM (2,2'methylene phenoxy) propionic acid); chloranocryl (Dicryl TM); bis(3,4,6-trichlorophenol); diclofop-methyl (Hoelon Diethofencarb TM (isopropyl 3,4-diethoxyphenylcarba 3ECTM, 2-(4-(2',4'-dichlorophenoxy)-phenoxy) methyl mate); Dimanin TM (alkyldimethylbenzylammonium propanoate); isothioate (Hosdon TM); allyxycarb (Hy

5,232,484 19 20 dimethyl-4,4'-bipyridinium ion); PCNBTM (pentachlo column (Alltech) using ultraviolet detection at 230 nm. ronitrobenzene); ethylan (Perthane TM, 1,1-dichloro Samples (2 ml) are quenched in methanol containing 2,2-bis(4-ethylphenyl) ethane); mepiquat-chloride 0.13% trifluoroacetic acid (3 ml) prior to chromatogra (PixTM, 1,1-dimethylpiperidiniumchloride); Propi phy. The mobile phase is methanol-water-trifluoroa neb TM ((((1-methyl-1,2-ethanediyl)bis(carbanodithi cetic acid in a ratio of 60:40:0.08 (v/v/v). At a flow rate oato))(2-))zinc homopolymer); sodium fluoroacetate of 1.5 ml/min, the elution time is about 7.8 minutes. (sodium monofluoracetate); ethalfluralin (Sonalan TM, Standards of the 2,4-dichlorophenoxy acid (Aldrich, N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4(tri 298% pure) are prepared in 60:40 (v/v) methanol fluomethyl) benzanamine); TCATM (trichloroacetic water. acid); TDETM (1,1-dichloro-2,2-bis(p-chlorophenyl) O Hydrogen peroxide is determined iodimetrically. To ethane); Teflubenzuron TM (1-(3,5-dichloro-2,4- prevent interference from Fe+3, titrations are carried difluorophenyl)-3-(2,6-difluorobenzyl)-urea); isobenzan out in the presence of NaF (100:1 Fe/F molar ratio). (Telodrin TM, isobornyl thiocyanoacetate); profluralin Chloride is measured with a chloride-selective elec (Tolban TM); TM (alpha, alpha, alpha-tri trode (Orion model 96-17B). Calibration curves are fluoro-2,6-dinitro N,N-dipropyl-p-toluidine); trihydrox 15 generated from NaCl standard solutions containing all ytriazine (2,4,6-Trihydroxy-1,3,5-triazine); and monu components of the reaction mixture except the herbi ron TCA (UroxTM). cide and peroxide. Prior to analysis, 5 ml aliquots of Preferred degradation reaction mixtures contain be sample or standard solutions are treated with 0.5 ml 1M tween a trace to about 1 mM pesticide, though the NaHCO3 (as buffer), 0.1 ml Orion ISA reagent, and 0.05 amount of pesticide present is not critical. An advantage 20 ml methanol to quench the herbicide degradation reac of the present invention is that a wide range of pesticide tion. Measurements are made within one hour after concentrations can be degraded by the ferric reagents of quenching. this invention. Carbon-14 is measured by liquid scintillation count The degradation reaction is generally carried out in ing in 15 ml Opti-Fluor (Packard Instrument Co.) using an acidic aqueous solution at room temperature (i.e., 25 about 18 to about 22 C.) in the presence of air and the external standard method. Quench curves are con preferably in the presence of light. Bright light is pre structed with CCL4. One-ml of reaction mixtures con ferred over dim light. The pH of the reaction mixture taining C-labelled compound is added to 1 ml water preferably varies between about 1.5 to about 3.5, more plus 0.5 ml methanol in a scintillation vial and purged preferably about 2.5 to about 3.0. Under these condi 30 with a stream of argon for 2 minutes to drive off 14CO2 tions, complete pesticide mineralization, i.e., complete before addition of the scintillation cocktail. conversion of organic material to inorganic, can take For CO2 gas evolution measurements, glass wool place in less than two hours with peroxide to pesticide impregnated with 0.3 ml of 1M aqueous ethanolamine is ratios as low as 5. employed as a CO2 trap in a well in the stopper of the An advantage of the present invention is that degra 35 reaction flask (1M NaOH works equally well, but the dation, and, eventually, mineralization, of toxic pesti resulting Na2CO3 is insoluble in Opti-Fluor). The cides can be achieved under mild conditions using rela stopper well and its contents (including the glass wool) tively inexpensive reagents and no special equipment. are added to a separate scintillation vial after first sepa Using dilute reagents, for example, herbicides such as rating the glass wool from the well with a forceps. In 2,4-dichlorophenoxyacetic acid and 2,4,5-trichloro 40 these cases, controls show the mass transfer of CO2 phenoxyacetic acid can be completely dechlorinated in from solution to well is complete within an hour. a fraction of an hour and completely mineralized in Reagents under two hours. (Specific conditions are set out in the next section.) It is an advantage of the invention that the Stock solutions of ferric salts are made fresh (within 1 method can be used both to destroy waste pesticides 45 h) before use in 0.1 or 0.01 M of the appropriate mineral and to decontaminate equipment. The invention is espe acid. Fe(ClO4)3 (GFS Chemicals, Columbus, Ohio) in cially suited to small to medium scale pesticide waste HClO4 is generally employed. Stock solutions of 2,4-D generation such as container and machinery rinsates and herbicide (about 0.03 to 0.14M) are prepared by con verting the acid form to the sodium salt With NaOH to removal of unused formulations. a final pH of 6 to 7. Ring-UL-C-2,4-dichlorophenox EXAMPLES yacetic acid (10 mCi/mmol) and carboxy-1C-2,4- The following examples are presented to further illus dichlorophenoxyacetic acid (9.0 mCi/mmol) are used as trate and explain the present invention and should not received (>98% pure) from Sigma Chem. Co. Hydro be taken as limiting in any regard. Unless otherwise gen peroxide (30%, Fisher) is assayed periodically and, indicated, all parts and percentages are by weight, and 55 if necessary, a diluted stock is made just prior to use. are based on the weight at the particular stage of the Nonphotolytic Degradation processing being described Experiments are conducted in a thermostated room at Example 1 21"-1" C. or in a water bath at 21'-02 C. A typical This example illustrates the degradation of the herbi experiment involves preparing a solution (usually 100 cide 2,4-dichlorophenoxyacetic acid (herein abbrevi ml in a 250-ml Erlenmeyer flask equipped with a mag ated 2,4-D) with an aqueous acidic ferric reagent con netic stir bar) containing herbicide, background electro taining hydrogen peroxide of this invention. lytes, and the iron stock solution, which lowers the pH to about 3. If the target pH is below 3, the pH is adjusted Analyses 65 with concentrated acid (usually HClO4). If the target pH 2,4-Dichlorophenoxyacetic acid is analyzed by high is higher than 3, NaOH is added, and the solution is performance liquid chromatography (HPLC) on a 5 allowed to stand for 15 minutes. A magnetic stirrer is micron Spherisorb ODS-2 C-18 reverse-phase 25 cm then turned up to sufficient speed to create a profusion 5,232,484 21 22 of bubbles to maintain oxygen saturation, and the reac FIG. 1 shows the sensitivity of the reaction to pH. tion is initiated by adding hydrogen peroxide. The rate is maximum around pH 2.7 to 2.8 and falls off Reactions where CO2 evolution is monitored are steeply on either side of the maximum. At optimum pH, carried out on a 10-ml scale in 50 ml Erlenmeyer flasks. herbicide disappears in under 30 minutes at hydrogen The flasks are fitted with a stopper holding a polypro 5 peroxide concentrations of 2.5 to 10 mM (FIGS. 1 to 3). pylene center well (Kontes) which contains a plug of Increasing the hydrogen peroxide concentration glass wool impregnated with ethanolamine as described from 10 to 500 mM results in significant improvements above. The flasks are placed on a revolving shaker at in 2,4-D mineralization (Table I). Increasing ferric ion, 100 revolutions per minute. on the other hand, has essentially no effect. At two The results are plotted in FIGS. 1 to 6. Dichloro O higher ferric concentrations (5 and 20 mM), the reaction phenol (herein abbreviated DCP) is a transient interme solution immediately turns a persistent deep red color diate in the reaction (FIGS. 1 to 3). The production and characteristic of soluble polynuclear ferric oxyhydrox disappearance of DCP parallel the reactivity of the ides, even in the absence of 2,4-D and hydrogen perox parent compound (FIGS. 1 and 2); thus, DCP peaks ide early under conditions where 2,4-D degradation is fast 15 Determination of the influence of herbicide concen (e.g., at pH 2.7), but correspondingly later under condi tration on mineralization is hampered by its limited tions where 2,4-D degradation is slow. solubility in acid form. However, no significant differ At optimum pH, chloride is released rapidly and ence in mineralization is seen between 0.1 and 0.5 nM quantitatively (FIG. 3). Dechlorination is practically 2,4-D at constant ferric and hydrogen peroxide concen concomitant with loss of parent material Chlorine pres 20 trations (Table I). Consistent with this, the reaction may ent in the species 2,4-D, DCP, and Cl accounts for be approximated as zero-order in 2,4-D concentration between 90 and 100% of total chlorine throughout the (i.e., linear with time) near the optimum pH (FIGS. 1 to reaction. Extraction of the reaction mixture with or 3), although more complex kinetics are found at other ganic solvents at various times during treatment of ring pHs. labelled 2,4-D with Fe3/H2O2 indicates that 2,4-D is 25 The transformation of 2,4-D by Fe+3/H2O2 is sensi rapidly converted to highly hydrophilic intermediates; tive to the anion originating from the ferric salt or acid for instance, the percent of ethyl-acetate extractable counterions and background electrolytes. Fe3/H2O2 radioactivity declined from 100% at time zero to <1% exhibits lower reactivity in chloride or sulfate solutions after dechlorination was achieved (i.e., after about 40 compared to perchlorate or nitrate solutions (Table II). minutes). 30 The pseudo zero-order rate constants at constant ionic Fe+3/H2O2 treatment of the herbicide at optimum strength (Nasalts) follow the order: pH also results in substantial mineralization of herbicide carbon. Evolution of CO2 from labelled compounds in reactions carried out in the dark cease after 3 to 4 hours. By this time most of the hydrogen peroxide has decom 35 Also, the peak yield of DCP in the presence of chloride posed. Table I summarizes the extent of mineralization is considerably higher compared to other anions (Table as a function of herbicide and reagent concentrations at II). pH 2.7 to 2.8 in perchlorate solution: In chloride solution, the ratio of moles of CO2 pro duced per mole of carboxy-1C-2,4-D reacted is much TABLE I greater than it is in perchlorate solution (FIG. 4). In Mineralization of Herbicides by Fe+/H2O2 perchlorate solution, mineralization of the carboxyl (Dark, pH 2.7–2.8, 02 MSodium Perchlorate) carbon of 2,4-D is slightly less extensive than ring car % initial Ca bons. Taken together with the higher yield of DCP in confirm E. mM Fe3+ rig 14CO chloride compared to ther anions (Table II) indicates 45 that the mechanism of herbicide decomposition varies ring-2,4-D 8: 8 : g 4. with anion. As little as 1000 mg/L (31 mM) methanol y oi 100 39 56 stops the reaction. FP 0. 500 27 69 Controls show that hydrogen peroxide is decom 1. 3. 8 2 NA posed by ferric ion in the absence of herbicide. The As oi io 5 52 SA 50 pseudo first-order rate constant, kobs, at a ferric concen F O. 10 20 57 NA tration of 0.99 mM shows a pH profile (FIGS. 5 and 6) 0.1 100 1 40 NA which is virtually identical that of the 2,4-D transfor carboxy-2,4-Dfy OS0.1 10010 4066 NA37 t (FIG. 1). The Fe+ -catalyzed decompositiona - Of ring 2,4,5-T 0.1 10 59 4. ydrogen peroxide is also sensitive to the anion (Table After 3-4 h reaction time. 55 II); the pseudo first-order rate constants measured in the Not analyzed. absence of 2,4-D follow the order: Example 2 CIO-NO3>CiteSO42.

TABLE I Influence of Anion on Ferric Iron Reactivity (10 mM Fet, pH 2.7–2.8) H2O2 decomposition 2,4-D transformation pseudo 1 or pseudo zero-order k, DCP max. kos. ht M electrolyte 10-4 M/h (2SE) yield, 7% (-2SE) NaClO4 3.3(0.3); 9.7 0.67(0.04) 5,232,484 23 TABLE II-continued influence of Anion on Ferric Iron Reactivity (10 mM Fet, pH 2.7-2.8) H2O2 decomposition 2,4-D transformation pseudo 1 or pseudo zero-order k, DCP max. kob, h M electrolyte 10-M/h (2SE)a yield, 9% (t2SE) 4.3(0.4) 1 NaNO3 3.6(0.6) 8.9 0.56(0.02); 0.49(0.04) 1 NaCl 0.39(0.09); 243; 0.31(0.01) 0.36(0.05) 25C Na2SO 0.36(0.04) 13 0.0330.001) 0.1. NaClO4 3.5(0.8) 1. o 0. NC 0.650.13) 28 0. Na2SO4 0.57(0.09) 4. re H2O) = 10 nM; ranger for C t, 0.963-0.996, n = 5-7; SE is standard error of slope. 'Ranger for in C/C vs , 0991-0.998, n = 9-11. Duplicate run.

20 H2O2 is ineffectual, and 0.2 and 0.4 nM are internedi Photolytic Degradation ate. Reactions are carried out in 250-ml Pyrex Erlen Example 2 meyer flasks equipped with a magnetic stir bar and This example illustrates the degradation of another covered with a 38 mm diameter watchglass. The flasks 25 herbicide, 2,4,5-trichlorochlorophenoxyacetic acid are stirred magnetically. Samples under "bright' condi (herein abbreviated 2,4,5-T), with an aqueous acidic tions are irradiated about 30 cm from a rack of four ferric reagent containing hydrogen peroxide of this 244-cm long 200 W "cool white' fluorescent lights. invention. Samples under "dim" light conditions are placed more The procedures and reagents described in Example 1, remote from the source and received a combination of 30 above, are employed, except that the methanol-water direct light and light reflected off the white walls of the trifluoroacetic acid proportions in the HPLC mobile OO phase is 70:30:0.064 (v/v/v); at a flow rate of 1.5 The radiant intensity in the visible region (400 to 700 ml/min, the elution time is about 7.2 minutes. Ring-UL nm) is measured with a Li-Cor Quantum Radiometer 14C-2,4,5-T was obtained from Sigma and used as re (Model LI-185B) while that in the near UV region (290 35 ceived (>98% pure). to 385 nm) is measured with an Eppley UV radiometer The results, plotted in FIGS. 10 and 11, are similar to (No. 23520) covered with a Pyrex beaker. Dark con 2,4-D (Example 1 above). The 2,4,5-T transformation at trols are carried out concurrently in aluminum foil-cov pH 2.8 is somewhat slower than 2,4-D, both in the dark ered flasks. and in the light. Chlorine is released rapidly and quanti FIGS. 7 and 8 shows that the transformation and 40 tatively (FIG. 10); chlorine in the species 2,4,5-T, tri mineralization of the herbicide in the presence of chlorophenol (TCP), and C together accounted for Fe+3/H2O2 is strongly accelerated by irradiation from between 93 and 1.15% of total chlorine throughout the a conventional fluorescent light. Samples under reaction period. "bright" light received 0.034 to 0.036 mW/cm2 in the Using initial rates, transformation of 2,4,5-T under near UV (290 to 385 nm) and 1.2 to 1.3 mW/cm2 in the 45 bright light is 1.6 times faster than in the dark. Samples, visible region (400 to 700 nm). Under these conditions, of 2,4,5-T were irradiated also under "dim" light (FIG. transformation of the herbicide in the presence of 1.0 11), which was 17 to 18 times lower in intensity than the mM Fe+3 and 10 mM H2O2 is complete in less than 0.15 bright light (and comparable to a poorly lit room). Dim hours and mineralization of ring-labelled 2,4-D is com light has almost no effect on 2,4,5-T transformation plete in less than two hours. Using initial rates, transfor 50 compared to the dark reaction. Din light also has no mation of 2,4-D under bright light is 2.7 times faster effect on ring mineralization of 2,4,5-T during the first than in the dark. hour. However, whereas mineralization in the dark Bright light iron-only and peroxide-only controls reaction is over in about two hours, mineralization show degradation, but on a much longer time scale under dim light continues for at least 10 hours at a slow (inset, to FIG. 7). Iron-only controls show slow loss of 55 rate. Dim light reactions at high iron concentrations parent herbicide and 25 to 30% mineralization over a (>5 mM), in which red polymeric iron products were 10-hour period. Peroxide-only controls show little or no present, reach a plateau in mineralization after about 2 parent herbicide transformation or mineralization. Dark hours similar to the dark reactions. iron-only controls also give no reaction. Hydrogen peroxide decomposition is accelerated under bright 60 Example 3 light, showing a pseudo first-order rate constant 1.35 This example describes the degradation of the herbi times greater than that of the dark reaction at 1 mM iron cide 2,4-dichlorophenoxyacetic acid (2,4-D) using fer and 100 mM peroxide rous ion and hydrogen peroxide using the method out The effect of hydrogen peroxide concentration on lined in Example 1 above, except that FeSO4 was used bright photo-assisted mineralization of ring-labelled 65 instead of Fe(ClO4)3. 2,4-D at constant iron concentrations of 1 mM is shown The reaction of 0.1 mM herbicide with Fe+2 and an in FIG. 9. Reactions carried out at 0.5, 2.0, 5.0, and 10 excess of hydrogen peroxide in an air-saturated acidic mM H2O2 are almost indistinguishable, whereas 0.1 mM solution at 21 C. is plotted in FIG. 13 (-0-). At 5,232,484 25 26 higher concentrations of ferrous ion and hydrogen per ferric ion and a peroxide in amounts effective to achieve oxide, i.e., greater than about 1 mM, 0.1 mM herbicide substantial mineralization of said pesticide. disappears in about a minute. No loss of herbicide is 2. A method according to claim 1 wherein said solu observed in controls carried out with hydrogen perox tion has a pH of about 1.5 to about 3.5. ide alone or with ferrous ion alone. 3. A method according to claim 1 wherein said perox The Fenton's transformation of 2,4-D under condi ide is hydrogen peroxide. tions in which the Fe+2 and H2O2 were initially present 4. A method according to claim 3 wherein said or in a stoichiometric ratio of 2:1 is plotted as a function of ganic pesticide is selected from the group consisting of pH in FIG. 14. The reaction rate decreases as the pH 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenox drops from 4.0 to 1.8. Dichlorophenol (DCP) is pro 10 yacetic acid, atrazine and 2-chloro-N-(2-ethyl-6- duced in low yield. methylphenyl)-N-(2-methoxy-1-methylethyl)aceta Mineralization of ring-14C-2,4-D by Fenton's reagent mide. (Fe+2/H2O2) and Fe+3/H2O2 ferric reagent is directly 5. A method according to claim 1 wherein said light compared in the plot of FIG. 15. Substituting Fe+2 in has an intensity of at least about 1.2 mW/cm2 in the place of Fe3 had no substantial effect on the extent of 15 visible region. mineralization of ring--C-2,4-D, except during the 6. A method for degrading an organic pesticide con first few minutes. These results indicate that the Fe+3/- taining oxidizable aliphatic or aromatic functional H2O2 reaction is the primary cause of mineralization groups comprising contacting said pesticide, in an aque under the pH and other conditions that optimize the ous solution having a pH of about 2.5 to about 3.0 in the activity of the ferric reagent of this invention. 20 presence of light, with ferric ion and peroxide in amounts effective to achieve substantial mineralization Example 4 of said pesticide for a time effective to achieve substan This example illustrates the degradation of atrazine tial mineralization of said pesticide. using the ferric reagent of this invention. 7. A method according to claim 6 wherein said pesti Atrazine was purchased from Ciba-Geigy (99% 25 cide is an aromatic compound. pure). Ring-UL-14C-atrazine (4.5 mCi/mmol, >98% 8. A method according to claim 6 wherein said pesti cide is selected from the group consisting of 2,4- pure) was purchased from Sigma Chemical Company. dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxya The procedures and reagents used for atrazine degrada cetic acid and atrazine. tion are those described under Example 1 above, except 30 9. A method according to claim 6 comprising an that the mobile phase for HPLC analysis of atrazine is initial ferric ion concentration of about 0.2 mM to about 65/35 (v/v) methanol-water at 1 ml per minute. 2.5 mM and an initial peroxide concentration of about FIG. 16 shows the degradation of 0.1 mM ring-UL 1.0 nM to about 500 mM. 14C-atrazine in the presence of 1 mM ferric ion and 10 10. A method according to claim 6 wherein said per mM hydrogen peroxide at pH 2.75 in the dark. Atrazine 35 oxide is hydrogen peroxide. disappears from solution in about 4 hours. However, no 11. A method for substantially mineralizing an or CO2 is released, and C in solution remains at initial ganic aromatic pesticide comprising contacting up to levels. This suggests that the s-triazine ring remained about 1.0 mM of said pesticide, in an aqueous solution intact. having a pH of about 1.5 to about 3.5, with about 0.2 The above description is for the purpose of teaching mM to about 2.5 mM ferric ion and about 1 mM to the person of ordinary skill in the art how to practice about 500 mM hydrogen peroxide in the presence of the present invention, and it is not intended to detail all light and in the absence of large concentrations of or those obvious modifications and variations of it which ganic solvents, chloride, and sulfate. will become apparent to the skilled worker upon read 12. A method according to claim 11 wherein said ing the description. It is intended, however, that all such 45 ferric ion is derived from ferric perchlorate or ferric obvious modifications and variations be included within nitrate. the scope of the present invention, which is defined by 13. A method according to claim 11 wherein said the following claims. organic aromatic pesticide is selected from the group What is claimed is: consisting of 2,4-dichlorophenoxyacetic acid, 2,4,5-tri 1. A method for degrading an organic pesticide con 50 chlorophenoxyacetic acid, 2-chloro-N-(2-ethyl-6- taining oxidizable aliphatic or aromatic functional methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide groups comprising contacting said pesticide, in an and atrazine. acidic aqueous solution in the presence of light, with k B k k

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