CA1338313C - Use of metal chelate complexes in dehalogenation - Google Patents

Abstract

A method for dehalogenation of organohalogen compounds, eg environmental pollutants in industrial waste. The organohalogen is reacted with a reducing agent in the presence of a selected metal-centred corrin, porphyrin or phthalocyanine complex. Pref-erred complexes are hydrolysis products of cyanocobalamin, of formula:

in which R1 is NH2 or OH, R is H, CH2CH2COOH or CH2CH2CONH2, R3 is H, CH2CH2COOH or CH2CH2CONH2, and R4 is NHCH2CH(OH)CH3, OH or NH2.
The complex is preferably immobilised on a substrate. Some novel metal-centred porphyrin complexes are also described. A dehalogen-ation apparatus using the method of the invention is also described.

Description

, I . 13383l3pos87 US~ OF MLTAL ~RTATR COMPLRXRS IN ~R~AT~h '~lON
This invention relates to a method of use of metal chelate complexes, in particular metal complexes o certain porphyrins, corrins and phthalocyanines in the dehalogenation of organo-halogen compounds, especially organohalogen pollutants. The invention also relates to novel metal-porphyrin and metal-corrin complexe6, including some such complexes which are suitable for use in this method.
Organohalogen compounds present an environmental pollution problem. They may enter soil and aquatic environments by several routes and may threaten the drinking water supply. They are generated in large quantities as wastes by the chemical industry.
Disposal of these wastes may be by incineration, which is expensive, or more commonly precipitation followed by landfill dumping which is cheaper but leads to high local concentrations of these pollutants.
An important class of organohalogen compounds are insecticides, which are introduced deliberately and directly into the environment, or else may enter the environment indirectly, for example as a result of processing sheep fleeces obtained from sheep which have been dipped in solutions of insecticides.
Some examples of organochlorine insecticides are briefly mentioned below.
DDT: 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane, (1):

Cl ~ -CH ~ -Cl (1) Commercially available DDT often consists of a mixture of (1) with several other organochlorine compounds including: 1,1,1 - trichloro -2- (0 - chlorophenyl) - -2- (p - chlorophenyl) ethane, 1, 1 -dichloro - 2, 2 - bis (p - chlorophenyl) ethane ( DDD or TDE ), 1 -(p - chlorophenyl) - 2,2,2 - trichloroethanol, 1,1,1 - trichloro - 2,2-bis (o - chlorophenyl) ethane and bis (p - chlorophenyl) sulphone. Degradation of commercial DDT may lead to other organochlorine compounds being present.

Lindane: 1,2,3,4,5,6 - hexachlorocyclohexane (2):
Cl Cl ~ Cl Cl ~ Cl (2) Cl Commercially available Lindane may contain a number of stereoisomers of (2).
Dieldrin: 1,2,3,4,10, lO - hexachloro - 6,7 - epoxy - -1,4,4a, 5,6,7,8,8a - octahydro - 1,4 - endo, endo -5,8- - dimethanonaphthalene (3): Cl 0 ~ ~ (3) Cl Organohalides are often extremely persistent, ie they are not easily degraded into environmentally acceptable or biodegradable products. Consequently they may be transmitted along the food chain to the detriment of higher forms of life including man. It is therefore desirable to find cheap and effective methods of degrading organohalides, particularly those which are persistent pollutants.
It is known that certain porphyrins and corrin6 are effective at causing and/or accelerating the degradation of organohalides by dehalogenation. Porphyrins, corrins and phthalocyanines are large, cyclic, metal-chelating, amines of related structure.
Porphyrins contain the ring system (4):

~ N ~ (4) which may carry peripheral substituents.

~_ 1 3383 1 3 A numb~r of porphyrin ring systems exist in nature, for example the protoporphyrin (4A), haematoporphyrin (4B), uroporphyrin (4C) and coproporphyrin (4D) systems:

Me Me HooccH2cH2 N~. ~ CH=CH2 ~/ ~ (4A) 10 HCCH2CH2 ~ ~ Me Me CH-CH2 Me Me 15NOOCCH2C~z ~ ~ CH-Me HOOCCH2CH2~,~Me Me CH-Me OH
--HOOCCH

HOOCCH2CH2~N ~CH2CH2COOH
~ (4C) 25HOOCCH2CH2 ~ CH2COOH

Me Me 30HOOCCH2CH2 ~ CH2cH2cooH

< ~ ~ (4D) HOOCCH2CH2 ~ N ~ -Me Me CH2cH2cooH

` 4 Corrins appear to exist in a number of isomeric forms in which the position of double and single bonds in their l9-membered peripheral ring system may vary, as will be seen in the discussion of structures 5A-5H below. The general abbreviation (5):

~ ~ (5) l~ N N ~
~'~

is used herein to represent all forms of the corrin ring including isomeric forms and those carrying peripheral substituents.
Phthalocyanines contain the ring system (6).

~ N

~ N~ N
N ~ (6) ~ N N

In porphyrin, corrin and phthalocyanine ring systems one or more of the central nitrogen atoms may be bonded to one or more hydrogen atoms, or all 4 may be co-ordinated to a central metal atom, which may itself be additionally complexed with one or more ~ other l~g~n~, for example to form the metal-co-ordinated centre:
Ll N "i~ . N
~5 L2 where M is a metal atom or ion, and where L1 and L2 if present represent the same or different ligands.

Porphyrins and corrins cont~ln~ne metal centres are known in nature. For example haematin,haem and haemin have protoporphyrin ring systems with an Fe(III)OH, a Fe(II~ and a Fe~III)C1 centre respectively. Chlorophyll is a magnesium centred porphyrin ring.
5 Such porphyrins are frequently found as parts of larger biological lecules, for example haemoglobin contains an iron-centred porphyrin complexed with proteins. ~Y~ s of known metal-centred corrins include the cobalt centred corrins found in the vitamin B12 series of compounds, eg vitamin B12 itself, ie cyanocobalamin, also known 10 simply as coh~l~ m; n, (5A):

C~ 3 c~ a C> C~2.c~
h,y Co c ~ ~ C U 7~C~I ~ ~O N N D

UZ~ C~ ~ ~
CH3 , , C ~ H c~3 ~0 CHLC~L I C~LC~L~ ~ h 1 (5A) CH ~
CH-C~3 O \OUo~cc~

hO CN~ ~

Closely related to cyanocob3lamin (5A) is dicyanocobalamin, which has a structure analogous to cyanocoh~l~m;n but in which two CN ligands are coordinated to the central cobalt ion an~ the riba-~ole resid~e does not chelate with the cobalt.
Other known cobalt centred corrins include hydroxycobalamin, a~enosylcobpl~;n and cobaloximes.

Other known cobalt-centred corrins are those described by Bonnett et al (1971) ie Neovitamin B12, a stereoisomer of (5A) in which the H and CH2CH2CONH2 substituents at ring position 13 are transposed, and the compounds (5Bi-vi) of structure:

CORl . Me Me CH2COR

C~ CHzCH2coRl 15 COBl ~ ,Me (5B) COR

i : Cobin~m~de R1 = NH2, R2 = H, R3 = CH2 CH2 CONH2, R4 = NHCH2CH(OH)Me.
ii : Neocobinamide Rl = NH2, R2 = CH2 CH2 CONH2, R3 = H, R~ = NH CH2 CH(OH)Me.
iii : Cobyric Acid Rl = NH2, R2 = H, R3 = CH2 CH2 CONH2, R4 = OH.
iv : Neocobyric Acid R1 = NH2, R2 = CH2 CH2 CONH2, R3 = H, R4 = OH.
v : Heptamethyl Cobyrinate Rl = R4 = OMe, R2 = H, R3 =
3 CH2 CH2 C02 Me.
vi : Heptamethyl Neocobyrinate R1 = R4 = OMe, R2 = CH2 CH2 C2 Me, R3 = H.

Cobalt centred corrins of formula (5C and D) are described by Gossauer et al (1977):
cOOMe O
Me M~e~
MeOOC ~ COCH3 Me N~ I ~N ~ R (5C) 0MeOOC~\~S( Me Me r COOMe COOCH3 COOCH
3 Me COOCH~
Me ~

~e'~\\-~/~ COOC1~3 20 I'le' ~ (5D) Z5 ~e t~ Me sC R L 5 D R
i H CN i H
ii H SCN or NCS ii Br 3 iii Br CN iii iv I CN iiv NO2 v NO2 CN v NH2 vi NH2 CN vi NH~ CF3COO
vii NHCOCH3 CN vii NHCOCH3 Bormann et al (1967) describes cobalt and nickel centred corrins of formulae 5E, 5F and 5G.

Me Me V

5 <~ 2 Co \ (5E) 10~/( Me 5E Rl R2 - _ i H H
ii CN H

Me Me 20 ~ R
N~ N ~ R2 N

5F Rl R2 i H H
3 ii CN H
Me Me ~,X~

35N~ ~ N--~
~ Ni /~ (5G) Me< ~ N ><Me CN

Bieganowski and Friedrich (19~0) also describe ~`e (III) centred analogues o-~ cyanocobalamin (5A) and cobyric acid (5Biii).
Holze and Gossauer (19~6) describe various ~legradation products of cyanocobalamin (5A) including (5H) in which the rib-S azole residue has been removed:
MeOOCCH2CH2 Me CH2COOMe MeOOCCH ~
~ 1¦ CN ~ CH2CH2COOMe Me - N I N ~ (5H) N l N ~

e , HO `Me MeOOCCH2CH2 Me CH2CH2CMe Some investigations of dehalogenation of organohalides by porphyrins and corrins have been carried out, as briefly reviewed below.
Wade and Castro (1973), Miskus et al (1965) and Zoro et al ~1974) describe the dehalogenation of a wide range of organohalides by iron-centred porphyrins such as iron tII) deuteroporphyrin IX, haematin, haemoglobin and haemin. Porphyrins are known to dehalogenate some organohalide lnsecticides, including DDT, 25 Lindane and Dieldrin. Castro (1964) discusses the possible reaction between iron ~II) deUteroporphyrin and DDT, and Wade & Castro (op cit) include DDT and DDD among the organohalides they studied. Stotter (1976) describes reactions between DDT and iron-centred porphyrins such as cytochromes, haemoglobin and haematin (these latter two being ~0 Fe (II) and Fe (III) complexes of proto-porphyrin respectively). The ability of other metals such as chromium and zinc to degrade DDT in vitro or in enzymic reactions is also discussed (in Stotter (1976) but without reference to porphyrins containing these metals. Ohisa et al (1980) refers to the dehalogenation of Lindane by iron-centred cytochrome 3~ P450. The interation between naturally occurring porphyrins and organohalide insecticides has been proposed as a mechanism for the - lo 1 3383 1 3 degradation via dehalogenation of these insecticides by biological residues such as those in lake water (Miskus et at, (op cit), and by certain cell extracts (Ohisa et al (op cit)).
However although an effective porphyrin may degrade a wide range of oraganohalides little is known about optimum metal/porphyrin combinations. For example the magnesium-centred chlorophylls have little or no ability to degrade organohalides, and haematin is known to be ca twice as effective as haemin in the degradation of lindane in identical conditions, although both have similar iron-centred structures, whilst cytochrome C, also iron-centred, does not degrade lindane to any substantial extent.
Bieniek et al (1970) describes the dehalogenation of lindane by cyanocobalamin. Both Bieniek (op cit) and Stotter (1977) refer to the dehalogenation of dieldrin (3) by cyanocobalamin. Neither of these references gives any kinetic data for the reactions of cyanocobalamin with these organohalides. Stotter (1976) and Jagnow et al (1977) refer to in vivo reactions between cyanocobalamin and a number of organohalides including chloromethanes, chloral hydrate and lindane. The degradation of DDT in cyanocobalamin-rich sewage sludge has been observed (Stotter op cit). Little work has been carried out however to identify the corrins which are most effective in the dehalogenation of organohalides, or optimum conditions under which dehalogenation may take place.
By virtue of their being naturally occurring and hence potentially cheap, porphyrins and corrins are attractive compounds for use in the degradation of organohalide pollutants.
It is an object of the invention to prepare and investigate novel metal-corrin complexes. It is a further object of the invention to provide a novel method using novel or known metal-corrin complexes to dehalogenate organohalogen compounds.
An aspect of the present invention provides a method for dehalogenation of a halogenated organic compound, which comprises causing the compound to react with a reducing agent in the presence of a complex of a corrin containing a metal centred ring system of the formula:

CH2C~zOOR
OORI M` e CH COR I

~ - -CH2CH2COR

~ 2 CoR4 wherein M is a metal atom or iron; A and B are coordinating ligands which may be the same or different; a and b are each O or l; R1 is NH2 or OH, R2 is H, CH2CH2COOH or CH2CH2CONH2, R3 is H, CH2CH2COOH or CH2CH2CONH2, and R is NHCH2CH(OH)CH3, OH or NH2.
Preferred corrin complexes for use in the method of the invention are those of magnesium, cobalt, nickel, molybdenum, iron and vanadium. Other suitable but less preferred ions are calcium, barium, strontium, chromium, copper, manganese and zinc.
The ligands A and B with which the metal may be additionally complexed are preferably inorganic ligands, especially CN , ~104 , SCN , S203 , S03 , Cl , H20, N02 and N03 .
The complexes of corrins have a basic formula 5I:
<~

N~N~ (SI) < ~

In the above formula, M is the metal atom or ion, A
and B are the same or different coordinating ligands, and a and b each are O or 1.
A preferred isomeric form for the corrin ring in 5I
is that found in structures 5A and 5~. The corrin ring in 5I
preferably has substituents on the ring which enhance the E solubility of the complex in water or enhance its ability to be bound to a solid substrate. Preferably there are up to 8 substituents independently selected from carboxylic acid-, hydroxyl-, or amide- terminated substituents or -OCH3 or -OC2H5, in one or more of the 2, 3, 7, 8, 12, 13, 17 or 18 ring positions. Preferably carboxylic acid- and amide-terminated substituents have a formula (CH2)nCOX where n is 0-3 and X is respectively OH; NR1R2 where R1 and R2 are independently H, C1 10 alkyl or C1 10 hydroxy-substituted alkyl eg ~CH2)mCHOH(CpH2p+1) where m and p are independently 1-5. Hydroxyl terminated substituents preferably have a formula (CH2)rOH where r is 1-5.
Other substitution positions on the 5I ring if occupied by other than hydrogen are preferably occupied by substituents which do not interfere by sterically hindering the approach of the organohalogen molecule to the metal M or do by causing a deleterious electron shift in the complex.
Suitable substituents on these other positions include small (eg C1 8) alkyl groups especially methyl, amino, cyano or ester groups, or monocyclic substituents such as in 5C. The method may also work but less satisfactorily when these other positions are occupied by larger organic residues such as the ribazole group present in dicyanocobalamin, but these may cause some interference.
The corrin ring system in complexes 5I may conveniently be, or be derived from, known corrin ring systems such as those in 5A - 5H above. For example ester, amide and cyano substituents in 5A - 5H may be hydrolysed to form carboxylic acid groups, which may then be converted to E

amide groups if desired by known methods. Additionally or alternately substitutents such as the ribazole side chain of cyanocobalamin may be removed eg by hydrolysis of the phosphate ester link to yield cobinamide.
Preferred metals M in these corrin complexes are those of Group 2, 5, 6, 7, 8, 9, 10, 11 or 12 of the periodic table, but especially cobalt, nickel, molybdenum, iron and magnesium, particularly cobalt. In many cases corrin complexes of formula 5I in which M is other than cobalt may be prepared from known cobalt-corrin complex precursors such as those described above by reaction of a solution of the cobalt corrin complex with a chelating ligand which has a stronger affinity for cobalt than the corrin residue, such as EDTA, preferably to form an insoluble cobalt-chelating ligand complex which may easily be separated. This leaves a vacant co-ordination site in the centre of the corrin ring into which a metal ion M may be inserted by incubating the corrin with a solution of the metal ion in a manner similar to that used for the porphyrin complexes above, Suitable conditions are reaction of the precursor with an equimolar amount of the chelating ligand in aqueous solution.
Preferred ligands A and B are inorganic ligands such as Cl04 , SCN , S03 , S2032 , H20 and in particular CN , Cl or OH . As many corrin complexes are known with a Co(CN)2 centre it is convenient to prepare cobalt corrin complexes in which A and B are other than CN starting from a Co(CN)2 centred complex precursor by incubation of the precursor with an equimolar amount of the ligand in aqueous E

- 15 ~ l 3383 1 3 solution.
In formula 5I, ta ~ b) is preferably 2 if M is cobalt II or III, and O if M is Ni II.
Preferred corrin complexes of formula 5I are the products of hydrolysis of cyanocobalamin (SA) or Neovitamin B12, eg on hydrolysis with an aqueous acid (eg HCl~ or alkali (eg NaOH) on heating.
Particularly preferred corrin-cobalt complexes of formula 5I are those of formula 5J:

CH2(~H2COR
COR~ CH2CORl COR

(51) ~oR4 in which R1 is selected from NH2 and OH, R2 is selected from H, CH2CH2COOH and CH2CH2CONH2, R3 is selected from H, CH2CH2COOH and CH2CH2CONH2, and R is selected from NHCH2CH(OH~CH3, OH and NH2.
Particularly preferred cobalt-corrin complexes of formula 5J are:
cyanocobalamin- SCN or S2O32 complexes, i.e.

-analogues of dicyanocobalamin having A = CN and B = SCN or cobinamide (5Bi), neocobinamide (5Bii), cobyric acid (5Biii), neocobyric acid (5Biv), cobyrinic acid (i.e.
5Bv having R1 = R4 = OH, R2 = H R3 = CH2CH2COOH) and neocobyrinic acid (i.e. 5Bvi having R1 = R4 = OH, R
CH2CH2COOH, R = H), i.e. having A = B = CN and a and b being l;
and analogues of cobinamide, neocobinamide, cobyric acid, neocobyric acid, cobyrinic acid and neocobyrinic acid in which the Co(CN)2 centre is replaced by a CoAB in which A
and B are selected from inorganic ligands other than CN , especially Cl and OH .
The method of the invention is preferably carried out in an aqueous medium, e.g. in aqueous solution. Corrin complexes appear to be somewhat pH dependent. A convenient pH is about pH 9.
Similarly the method is found to work over a range of temperatures, and the rate of dehalogenation generally increases with increasing temperature. Conveniently ambient temperature (ca 20C) may be used, and an upper optimum practical limit appears to be ca 80C. In some cases illumination of the medium may be beneficial.
As the corrin complexes used in the method of the invention may in some cases have one or more functional substituents such as amine, amide, hydroxy and acid groups and may in some cases have a complex stereochemistry, they may exist in a number of ionised or protonated forms depending upon the pH, etc. of the medium in which they are contained, and may also exist in a number of complexed forms or in an ionised form combined with a counter-ion, e.g. Cl.
The method of the invention includes all forms of the complex, and all stereoisomeric forms thereof.
It is essential that the medium in which the reaction of the method takes place contains a reducing agent.
These may be inorganic reducing agents such as borohydride, dithionite, sulphite, phosphite, hypo phosphite, sulphide etc. Organic reducing agents such as dithioerythreitol, dithiothreitol, mercaptosugars etc may also be used. Many such chemical reducing agents may be used and are well known to those skilled in the art. Additionally or alternatively microorganisms which create a reducing environment or are capable of carrying out reduction may also be employed as a reducing agent, and included among these are known anaerobic microorganisms such as those which are found in soil.
The method of the invention is found to work over a wide range of concentrations of the complex, the organohalogen compound and the reducing agent. For quantitative dehalogenation of the organohalogen it is important that the medium contains at least one molar equivalent of the reducing agent per atom of halogen to be removed. Generally the complex is not used up in the method, but appears to function essentially as a catalyst assisting transfer of electrons from the reducing agent to the organohalogen compound. The ratio of complex to organohalide 1 33~31 3 does not therefore appear to be critical.
In many cases the kinetics of the reaction between the complex and the halogenated organic compound shows first order kinetics, and hence the rate at which dehalogenation occurs depends upon the relative concentrations of the complex and the compound. These may be varied between wide limits and will depend upon the environment or medium in which the reaction occurs. For example the method may be used at organohalide concentrations down to ppm level as experienced in many pollution situations, and experiments have shown method to be effective at 1 x 10 5M concentrations of organohalide.
The presence of other chemicals in the medium does not in many cases interfere with the method of the invention but in the case of the corrin complexes, excess cyanide in the medium may be detrimental. This cyanide may therefore be removed using known methods.
The method of the invention is suitable for dehalogenation of a wide range of halogenated organic compounds, wherein the halogents) may be chlorine, bromine or iodine. In general the method is more effective at dehalogenating compounds in which the halogen atom is attached to an aliphatic carbon atom than those in which the halogen is attached directly to an aromatic ring. With this reservation the compounds may for example be alkyl halides, alkenyl halides, haloalkanes or alkenes, halogenated nitrile or nitro compounds, aryl-alkyl or aryl-alkenyl halides, halo-ethers, or other halogenated poly-cyclic aliphatic or r~ ~
~ j 28472-52 -aromatic compounds etc.
The method is particularly attractive for the degradation by dehalogenation of halogenated organic compounds which are considered to be environmental pollutants, for example DDT, lindane, dieldrin, hexachloro-butadiene (considered a priority pollutant by the European Economic Community). It is possible that in some circumstances the method may be used to degrade the pollutant dioxin. Other organohalogen compounds for which the method may be used will be apparent to those skilled in the art.
In many cases the method of the invention may dehalogenate these compounds to form products which are considered to be environmentally acceptable or which may be further degraded by other processes. For example the method of the invention may be used to cause an initial didechlorination of lindane to tetra-chlorocyclohexene, followed by a further dechlorination to monochloro-benzene.
In an industrial environment, the method may for example be applied by simply mixing an appropriate quantity of a metal corrin complex with an industrial waste solution containing the undesirable organohalide, ensuring that the solution is reducing, adjusting the pH and leaving the mixture to stand for a suitable length of time, during which the quantity of the organohalide may be monitored. Other methods of treating such industrial wastes, or polluted rivers, lakes or ground etc will be apparent to those skilled in the field.
In a preferred way of performing the dehalogenation method of the invention, the complex is immobilised on an insoluble substrate and a solution containing the halogenated organic compound is brought into contact with the immobilised complex. To ensure that a reducing agent is present the solution may contain a reducing agent or the substrate may have a reducing agent bonded or absorbed onto it.
This way of performing the method offers the advantage that the method may be made continuous or semi-continuous, ie a solution to be dehalogenated ~eg an industrial or agricultural effluent) may be passed through a bed containing a complex immobilised on a substrate, and the method need only be discontinued for regeneration of the bed.
The flow rate to achieve a suitable residence time for the solution to be dehalogenated will of course depend upon the nature of the compound to be dehalogenated, the concentration etc, but experimentation of a relatively straightforward nature can determine these parameters.
The substrate may be any insoluble material, preferably otherwise inert to the solution, onto which the complex can be immobilised. To ensure that the complex is firmly immobilised onto the substrate it is preferred that the complex is chemically bound to the substrate by means of interaction between functional groups on the corrin ring and appropriate functional groups on the substrate. In view of the fact that the corrin complexes have carboxylate (COOH) and amide (CONH2) functional substituents on their rings respectively, preferred substrates are materials which have functional groups which are capable of combining with these on their surface. For example amine (NH2) and amide groups on the substrate may react with carboxylate groups on the complex, and carboxylate groups on the substrate may react with amine or amide groups on the complex, to form chemical bonds.
Many suitable substrates having such functional groups are known in particular the substrates commonly used for affinity chromatography. For example derivatised polysaccharides such as celluloses, agarose, dextrose and dextran, polyacrylamides and copolymers of these materials such as polyacrylamide-agarose gels, which may be either cross linked or non-cross linked. Alternatively derivativised inorganic oxides such as silica, alumina, titania or zirconia, or glass beads may be used. Polymeric materials such as polystyrene beads or ion-exchange resins may also be used.
Preferred substrates are derivatised forms of the known polysaccharide Sepharose*, particularly AH - Sepharose and CH - Sepharose having respectively amino and carboxylate functional groups on their surface.
When AH - and CH - Sepharoses are used to immobilise the corrins in this way, the reaction scheme may be as below:

E *Trade-mark - 22 ~ l 3383 1 3 Sepharose -NH-(CH2)6-NH + HOOC-(CH2)n -Porphyrin/ Corrin (AH - Sepharose) 2 Il V
Sepharose-NH(CH2)6-NHC-(CH2)n -Prophyrin/ Corrin o Sepharose-NH(CH2~6-COOH + H2NC -(CH2)n--Corrin/ Porphyrin (CH - Sepharose) l ~ H20 O O
1~ 11 Sepharose- NH(CH2)6-C-NH-C- (CH2)n Corrin/ Porphyrin (where n is 0, 1 or 2) The complex may be bound directly to the substrate by standard methods, eg the use of a carbodiimide coupling agent. It i5 preferred to bind the corrin first to the substrate and then to add the metal ion. Binding of the corrin to the substrate may also use standard methods, eg the use of a carbodiimide, but a preferred method for binding the corrin complexes to a substrate which consists of a derivatised polysaccharide such as AH - or CH - *Sepharose is to prepare a suspension of the substrate in a solution containing the appropriate corrin at pH7 then rapidly adjusting the pH to 12 followed by a rapid adjustment of the pH to 2, then finally rapidly adjusting the pH back to 7.
The substrate plus immobilised corrin may then be filtered off, washed, and then exposed to a solution containing metal ions, to form the immobilised complex.

When the immobilised complex is prepared in this way it is preferred to use a ratio of corrin to substrate in which the amount of corrin is in excess of that required to E

- 22a - 1 33831 3 occupy all the available binding sites on the substrate so as to reduce any subsequent problem caused by the organohalogen compound binding to the substrate. It is also preferred to use an excess of the metal ion to ensure that as far as possible all the corrin rings contain a complexed metal ion.
According to further aspect of the invention there is provided a water-insoluble substrate, having immobilised thereupon a corrin complex as defined above for use in the method for dehalogenation of a halogenated organic compound.
Suitable and preferred forms of such a substrate and immobilised complex are as indicated above. Such materials may be supplied separately for use in the method of the invention as discussed above, or for example contained in a cartridge through which an effluent solution to be dehalogenated may be passed.
In most cases no regeneration of the corrin complex appears to be necessary after the complex has been used for dehalogenation, but if the complex begins to lose its activity then exposure to a reducing agent such as that used in the dehalogenation process results in regeneration.
In a further way of carrying out the dehalogenation method of the invention, a complex of the corrin either in a free form or immobilised on an immobilised substrate may be mixed with a suitable quantity of a reducing agent prior to use. Such a mixture may subsequently be introduced into an environment containing a halogenated organic compound to be dehalogenated, for example used containers for these compounds prior to disposal.

- 22b -As mentioned above, the method of the invention is preferably carried out with the halogenated organic compound present in an aqueous solution. However the method may readily be applied to the dehalogenation of halogenated organic compounds dispersed or suspended in an aqueous medium, or when contained in a solid or in a gas such as contaminated air. For example to treat solids, the solid may be suspended or dissolved in an aqueous medium so that the organohalogen compound partitions into the aqueous phase, where lt may be dehalogenated using the method of the inventlon .
To treat gases, the gas may for example be bubbled through an aqueous medium containing the corrin complex and the reducing agent. In a preferred way of treating gases, the gas is passed through a column packed with a bed of a substrate having immobilised thereupon the corrin complex as described above, and a current of an aqueous medium containing a dissolved reducing agent is also passed through the bed. In both cases the organohalogen partitions between the gas and liquid phases and is dehalogenated in the liquid phase.
The invention also provides an apparatus for dehalogenation of a halogenated organic compound using the method of the invention. Preferably the apparatus uses a substrate having immobilised thereon a complex as described above and incorporates a bed of such a substrate plus complex contained within a body and being capable of having a liquid or gas containing the halogenated organic compound passed E

- 22c -through. Such an apparatus may incorporate a replaceable cartridge containing the bed, in a construction similar to a conventional water softener or gas scrubber apparatus.
Non-limiting examples illustrating the invention as well as related art will now be described, with reference to Figs 1 and 2 which show apparatus for dehalogenation of halogenated organic compounds according to the invention.
Abbreviations: The abbreviation ~Me" is used for CH3 herein 1. PreParation of PorPhYrin/metal ion comPlexes Porphyrins (15 ~g) containing no metal ions (protoporphyrins, coproporphyrin, uroporphyrin and haematoporphyrin), were dissolved in 100 mM Tris/HCl buffer (150 ~l), pH 9.0, prior to incubation with equimolar solutions of a range of metal ions (present as the chloride) at 37C for 30 min in the dark.
A further series of complexes was prepared using protoporphyrin under conditions identical to those described above except that 100 mM sodium acetate buffer at pH 5.5 was used instead of the Tris/HCl.
lA Complexinq of metal ion with liqands Samples (15 ~g) of either commercially obtained cobalt contain$ng protoporphyrin were dissolved in 100 mM
Tris/HCl buffer (150 ~l), pH 9.0, prior to incubation with equimolar solutions a variety of ligands at 37C for 30 min in the dark. Samples (10 ~l) of the porphyrin/ligand complex were removed and assayed for the ability to dehalogenate lindane. The absorbance spectrum of each sample was E
i 28472-52 J

- 22d - 1 338313 determined between 250 and 700 nm in a recording spectrophotometer (Shimadzu Model UV 240, V A Howe Ltd, London).
lB Dehaloqenation of lindane Lindane dehalogenation was assayed in the following reaction mixture: 1 ml 100 mM Tris HCl buffer, pH 9.0, containing 5 mM dithiothreitol (DTT) and 10 mg/l lindane.
The reaction was initiated by the addition of 10 ~1 of a sample of a solution of a complex as prepared in 1 or 2 above, and the reaction mixture was purged with nitrogen prior to incubation at 37C for 30 minutes. The reaction mixture was extracted with 2 ml hexane:

l `--23 l 3383 1 3 diethyl ether (85:15, v:v) and 0.5 ,ul Or this extract was analysed by lr~ electron capture GLC. The chromatograph was equipped with a 1.5 m x 4 mm silanised glass column, packed with 3% SE30 on a 100/120 mesh Supelcoport~
with notrogen (40 ml/min) as the carrier gas. The in~ector and detector were maintained at 250 C, whllst the column over was maintalned at 190 C.

In order to asse8s the klnetics Or dehalogenatlon the following reactlon mlxture was used: 10 ml Tris HCl buffer, pH 9.0, contalning 5 mM
DTT and 10 mg/l Lindane. The reaction mixture was equillbrated at 37 C
prlor to the addltlon Or 100 ~1 Of a æample of the comple~ solution pre-pared in 1 or 2 above, and then purged with nitrogen and sealed with a butyl rubber 8eptum and incubated at 37C. At 5 minUte intervals, a hy~-odermic ~yringe was used to withdraw 0.5 ml samples, which were extracted with lml hexane:diethyl ether (85:15 v:v), and 0.5 yl of this ext~act 15 was analysed by GLC as describel above.
lC Re~ults The results are expressed ln Table 1, 2 and 3 below.

In Table 1, the various metal/porphyrln complexes without ligands which were prepared are llsted together with an indicator Or thelr relat-lve ability to dehalogenate Lindane.
In Table 2, the efrect Or complexing the cobalt atom in a cobalt protoporphyrin complex with additional ligands is shown.

Table 3 shows comparative data for knownmetal/porphyrin complexes, for uncomplexed porphyrins and for the two known compounds cobalt phthalocyanine and cobalt protoporphyrin. In Table 3 the identity Or the metal centre is indicated.

3 The results presented in Tables 1 and 2 demonstrate that metal/
porphyrin complexes may be prepared which are erfective at dehalogenating Lindane. Table 3 shows clearly that many metal/porphyrin complexes, and porphyrins without metal centres, are very ineffective in comparison with the speciric complexes identified by the invention.

~ r~ k Table 1 ~ 3 3 8 3 ~ 3 Dehalogenation of Lindane by porphyrin/metal ion complexes Porphyrin Base Proto- Urop Copro- Haemato-5 Metal Ion Porphyrinporphyrin porphyrin porphyrin pH 5.5 pH 9.0pH 9.0 pH 9.0 pH 9.0 None 0 0 . 0 0 0 Cobalt (II) 320 0 160 280 35 10 Copper (II) 0 0 0 0 0 Iron (II) 240 56 110 250 Iron (III) 250 0 110 280 Magnesium (II)350 0 140 3 35 Manganese (II)0 0 0 0 0 15 Molybdenum (III) 260 0 120 240 250 Nickel (II) 220 0 130 210 200 Vanadium (V) 20 0 24 16 30 Zinc (II) 0 0 Results expressed as nmole Lindane removed/min/mg porphyrin Porphyrins and metal ions were preincubated together for 30 minutes at the pH shown in the dark priorto assay.
Table 2 . Effect of Ligands on Lindane dehalogenation Ligand Co-Protoporphyrin None 1300 Cyanide 1250 Perchlorate 1300 Thiocyanate 1300 Thiosulphate 1280 Sulphite 1250 Results expressed as nmole Lindane dehalogenated/min/mg porphyrin.
All-incubations carried out in the dark at 37 C.

_~ 1 3383 1 3 Table 3 ~ -- -Dehalogenation of Lindane by a variety of porphyrins and analogues Porphyrin M Activity Bacteriochlorophyll a (dark) Mg 0 Chlorophyll a (dark) Mg 0 Chlorophyll b (dark) Mg 0 Bacteriochlorophyll a (light~ Mg 0 Chlorophyll a (light) Mg 0.1 Chlorophyll b (light) Mg 0 10 Cytochrome c Fe o Haemocyanin Cu 0 Haemoglobin Fe (II) 10 Haemin Fe (III) 380 Haematin Fe (III) 710 15 Uroporphyrin _ 0 Coproporphyrin -Protoporphyrin - 0 Co Phthalocyanine Co 560 Cu Phthalocyanine Cu 0 20 Co Protoporphyrin Co 1300 Results are expressed as nmole lindane dehalogenated per minute per mg of porphyrin. All incubations were at 37C in dark unless ind-icated otherwise.
2 . Dehalogenation using ~orrin Comp~exes.

2A Complexing of corrin with ligands Samples (15 ~g) of commercially obtained cyanocobalamin were dissolved in 100 mM Tris/HC1 buffer (150 Jul), pH 9.0, prior to incubation with equimolar solutions of a variety of ligands at 37C
for 30 min in the dark. Samples (10 ~1) of the corrin!ligand complex were removed and assayed for the ability to dehalogenate Lindane. The absorbance spectrum of each sample was determined between 250 and 700 nm in a recording spectrophotometer (Shimadzu Model UV 240, V A Howe Ltd, London).

~5 26 1 3383 ~ 3 2B Removal of Cyanide T;e~ndS from Cobinamide.
Cobinamide (5Bi, having two CN ligands complexed to its central cobalt III ion) (lOmg) was dissolved in water (lOml) prior to addition of O.lM HCl to pH 2Ø The absorbance spectrum of the sample before and after acidification was determined between 250 and 700nm in a recording spectrophotometer. The acid-ified sample was freeze-dried overnight and subsequently re-dissolved in 100 mM Tris/HCl buffer (lOml), pH 9.0, and the pH
adjusted to 9.0 by the addition of O.OlM NaOH. The absorbance spectrum of the sample was then reletermined. Samples (10 ul) were diluted in 100 mM Tris/HCl buffer (90 ul), pl~ 9.0, and 10 ul of this diluted material was assayed for the ability to dehalogenate lindane.
2C L~PAm;nation of Cob2lamin Cobalamin (5A, 80 mg) was dissolved in 3M sodium hydroxide B (20 ml) and incubated at 80 C for 72 hr, prior to gel filtration using Fractogel TSK-40 (column dimensions 2 x 50 cm) equilibrated in water. The corrin fraction was eluted using water pumped at a flow rate of 30 ml/hr. Analysis of the corrin fraction by mass spectroscopy indicated the loss of both the ribazole moiety anl the amino groups in the amide substituents around the corrin ring, leading to a cobyrinic acid or an isomer thereof.
2D ~ehalogenation of Lindane Lindane dehalogenation was assayed in the following reaction 25 mixture: 1 ml 100 mM Tris HCl buffer, pH 9.0, containing 5 ml~l dithiothreitol and 10 mg/l Lindane. The reaction was initiated by the addition of lO,ul of a sample of a solution of a complex as prepare~ in 2A above, and the reaction mixture was purged with nitrDgen prior to incubation at 37 C for 30 minutes. The reaction 30 mixture was extracted with 2ml hexane : diethyl ether (85 : 15 v : Y) and 0.5 ~ul o~ this extract was analylsed by electron glc.
The chromatograph was equipped with a 1.5 m x 4mm silanise-1 glass column packed with 3% SE30 on a 100/120 mesh Supelcoport with nitrogen (40ml/min) as the carrier gas. The injector anl detector were maintained at 250 C, whist the column oven was maintained at 190C.

* Tr~ ~k t 3383 1 3 In order to assess the kinetics of dehalogenation the following reaction mixture was used:lO d lOO~M Tris HCl buff~r, pH 9.0, containing 5 mM DTT and 10 mg/l Lindane. The reaction mixture was equilibrated at 37C prior to the addition of lOO ~l of a solution of the corrin complex (l~g/lO~L). The reaction vessel was purged with nitrogen then sealed with a butyl rubber septum and incubated at 37C. At 5 minute intervals, a hypodermic syringe was used to withdraw O.5 ml samples, which were extracted with lml hexane:diethyl ether (85:15 v:v), and 0.5 ~l of this extract was analysed by GLC as described above.
~ 10 Results The various cyanocobalamin - ligand comlexes which were prepared, together with the rate at which they dehalogenated lindane (nmole lindane min mg complex) at 37~C in the dark, are listed below in table 4 . The equivalent results for cyanocobalamin and adenosyl-cobalamin are also given as a comparison.
Table 4 Corrin Rate of Dehalogenation adenosylcob~l~.m; n 75o cyanocob~rin-sulphite complex 760 cyanocob~l~.m; n-perchlorate complex7~0 cyanocok~ r;n 800 cyanocobalamin-thiosulphate complex800 z5 dicyanocob~ m; n ca.800 cyanoco~ ;n-thiocyanate complex 820 cobinamide (with two CN ligands) 6750 cobinamide (without CN ligands) 6~25 cobyrinic acid (without CN ligands)~ 6~25 From the results presented in table 4 it is clear that corrin ~,0 coplexes have been identified which are substantially more effective at dehalogenating lindane than cyanocobalamin itself.

~5 28 l 3383 1 3 3. Immobilisation of Porphyrins and Corrins onto Substrates 3A Immobilisation of Porphyrins onto AH-Sepharose 4B Substrate AH-Sepharose 4B (2g) was swollen in 0.5M NaCl (20ml), and washed with this solution (400ml). The Sepharose was then washed in demineralised water adjusted to pH 4.5 (lOOml). Haematoporphyrin (40mg) was dissolved in water (40ml) and added to the Sepharose.
The pH of the slurry was adjusted to pH 12 by addition of NaOH (lOM) and held at this pH for 2 min. The pH was then adjusted to pH 2 by addition of HCl (6M) and held at this pH for a further 2 min. The slurry was then adjusted to pH 7 by further addition of NaOH prior to washing of the gel with distilled water.
Alternatively, haematoporphyrin was bound to the Sepharose by carbodiimide coupling. AH-Sepharose 4B (2g) was swollen in 0.5M
NaCl (20ml), and washed with this solution (400ml). The Sepharose was then washed in demineralised water adjusted to pH 4.5 (lOOml).
Haematoporphyrin (40mg) was dissolved in water (40ml) and added to the Sepharose. The pH of the slurry was adjusted to pH 5.0, prior to the addition of N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) to a final concentration of lOOmM. The slurry was stirred overnight at room temperature in the dark, prior to washing with distilled water. This ratio of haematoporhyrin to sepharose ensured an excess of porphyrin to available binding sites.
The substrate plus porphyrin was filtered off, washed, and treated with a large excess of the metal ion (lmg/ml) in solution eg as the chloride, in a molar ratio ion porphyrin of 10 : 1.
Excess unbound metal ion was removed by extensive washing in deionised water.
3B Immobilisation of cob~l~ ;n onto CH-Sepharose 4B
CH-Sepharose 4B (2g) was swollen in 0.5M NaCl (20ml), and washed with this solution (400ml). The Sepharose was then washed in demineralised water adjusted to pH 4.5 (lOOml). Cobalamin (5A) (40mg) was dissolved in water (40ml) and added to the Sepharose.
The pH of the slurry was adjusted to pH 5.0, prior to the addition of EDC to a final concentration of lOOmM. The slurry was stirred overnight at room temperature in the dark, prior to washing with distilled water. Problems were encountered in the immobilisation of cob~l~ i n onto CH-Sepharose 4B, probably due to the preæence of the carbonyl group of the amide.
3C Immobilisation of alkali-modified cob~l~ i n onto AH-Sepharose AH-Sepharose 4B (2g) was swollen in 0.5M NaCl (20ml), and washed with this solution (400ml). The Sepharose was then washed in demineralised water adjusted to pH 4.5 (lOOml). Alkali-modified cobal~l ;n prepared as in 2C above (40mg) was dissolved in water (40ml) and added to the Sepharose. The pH of the slurry was adjusted to pH 5.0, prior to the addition of EDC to a final concentration of lOOmM. The slurry was stirred overnight at room temperature in the dark, prior to washing with distilled water.
f 3D Immobilisation of alkali-modified cob~l~ ; n onto QAE-Sephadex QAE-Sephadex A-50 (5g) was mixed with alkali-modified cob~ ;n prepared as in 2C above (4mg/ml; lOOml) for 20 minutes, and the slurry then poured into a column and washed with distilled water (250ml) prior to use.
3E Immobilisation of corrins onto Amberlite XAD-2 Amberlite~kXAD-2 (4g) was added to a solution of cobal~ ;n (5A) 20 (80mg) dissolved in lOOmM Tris/HCl, pH 7, (20ml). The amberlite was then washed in the same buffer (200ml). It was found that washing of the substrate plus corrin with water led to a ælow leaching of the cobalamin from the Amberlite.
3F Immobilisation of modified cob~l~ ;n onto polystyrene beads Alkali-modified cobala ;n prepared as in 2C above was immobilised onto two types of polystyrene beads, differentiated by their functional groups, either hydrazide or alkylamine moieties.
Hydrazide-derivatized poly~ ~ene beads (6mm diameter) (25) were placed in a solution of alkali-modified cob~l~l ;n (4mg/ml in water; lOml), and the pH ad justed to 5 . 5 prior to the addition of EDC to a final concentration of lOOmM. After mixing overnight at room temperature in the dark on a bottle-roller, the beads were washed with distilled water prior to use.
Alkylamine-derivatized polystyrene beads (25) were placed in a solution of alkali-modified cobal~ ;n (4mg/ml in water:ethanol (l:l;v:v); lOml), and the pH adjusted to 8Ø After mixing for ~ '7J~a~ ,7~ ~k 2 hours at room temperature in the dark on a bottle roller, the beads were washed with distilled water prior to use.

4. Dehalogenation Assays: Liquid Phase 4A All of the immobilised catalysts were tested for the ability to dehalogenate either lindane ( ~ -hexachlorocyclohexane), carbon tetrachloride, trichloroethylene or dichloromethane. The immobilised catalysts were poured into a column to provide a bed volume of 5ml, with the exception of the polystyrene beads where 25 beads were used in a column. A solution of lOOmM Tris/HCl, at a pH of either 7.0 or 9.0, cont~;ning 5mM DTT and either lOppm lindane or lOOppm of carbon tetrachloride, dichloromethane or trichloro-ethylene was pumped through the column at flow rates suitable to give residence times of 5, 10 and Z0 minutes. Effluent from the column (lml) was extracted with diethyl ether/hexane (15:85, v:v;
2ml) prior to analysis by electron-capture GLC.
4B Dehalogenation using Immobilised Porphyrins Immobilisation of haematoporphyrin onto AH-Sepharose, either by pH shift or carbodiimide coupling, and subsequent washing in a solution of either cobalt chloride or magnesium chloride (as described in 3A), resulted in the formation of a catalyst capable of the dehalogenation of lindane (Tables 5 and 6), although dehalo-genation by the column equilibrated with cobalt was more effective than that equilibrated with magnesium. The column equilibrated with cobalt was able to dehalogenate lindane at over 99% dehalogenation of a lOppm solution at a residence time of 10 minutes for over 76 days. After 257 days this column was still able to dehalogenate 66% of the lindane under the same conditions.

Table 5 Dehalogenation using bound Cobalt-Haematoporphyrin Days of operation Residence time (minutes) S Lindane dehalogenated 0 10 99.6 1 5 98.4 1 10 99.5 1 20 99.8 2 10 99.5 99.5 9 10 99.3 13 5 96.8 13 20 99.6 99.4 99.6 18 10 99.4 21 5 99.3 21 20 99.8 28 5 98.8 28 10 99.3 33 5 99.5 33 10 99.7 33 20 99.9 99.2 99.6 , 99.4 61 5 99.5 61 lO 99.5 61 20 99.3 76 5 99~
91 5 98.5 91 10 9~.8 91 20 98.8 257 10 66.2 Table 6 Dehalogenatlon uslng bound Magnesium-Haematoporphyrin Day~ of operation Residence tlme (minute~) % Lindane dehalogenated Using the method of examples 1, 2 and 3 above it was also possible to dehalogenate carbon tetrachloride, methane being the ultim~te product 4C Dehalogenation using Immobilised Corrins When immobilised onto AH-Sepharose, alkali-modified cobalamin (3C product~ was capable of the dehalogenation of lindane. Over 99%
of a lOppm solution of lindane could be dehalogenated by this system at a residence time in the column of 5 minutes.
When immobilised onto QAE-Sephadex, alkali-modified cobalamin (3D product) dehalogenated over 99% of a lOppm solution of lindane at a residence time of 5 minutes. Both carbon tetrachloride and dichloromethane were dehalogenated by this system: 99% of a lOOppm ~3 t 3383 1 3 solution of either compound could be dehalogenated at a residence time of 10 minutes. In both cases, methane was identified as an end product. No dehalogenation of trichloroethylene was observed with this system, and the presence of trichloroethylene appeared to cause a slow leaching of the alkali-modified cobAl~ ;n from the Sephadex.
When alkali-modified cobRl~ in was immobilised onto hydrazide-derivatized polystyrene beads (3F product) by coupling with EDC, over 99% of a lOppm solution of lindane was dehalogenated when the solution was delivered at a flow rate equivalent to that necessary to provide a residence time of 5 minutes for the other matrices (ie 60ml/h). Carbon tetrachloride,dichloromethane and trichloro-ethylene were not dehalogenated by this system.
When immobilised onto alkylamine-derivatized polystyrene beads (3F product), alkali-modified cob~l~ in again catalysed the dehalogenation of over 99% of a lOppm solution of lindane when the solution was delivered at a flow rate of 60ml/h. In addition, 99%
of lOOppm solutions of either carbon tetrachloride or dichloro-methane could be dehalogenated when pumped at flow rates of 60ml/h.

5. Gas-phase dehalogenation In order to assesæ the potential of immobilised corrins to dehaiogenate gaseous organohalides, alkali-modified cobalamin (2C
product) immobilised onto both QAE-Sephadex and alkylamine-derivatized polystyrene beads was tested for their ability to dehalogenate dichloromethane. Air saturated with dichloromethane was pumped through a column of either QAE-Sephadex (5ml) or alkylamine-derivatized poly~y.ene beads (25) to which alkali-modified cob~l~ in had been bound, at a flow rate of 400ml/h. In addition, 500mM DTT was pumped onto the column at a flow rate of 4ml/h. The gas phase emerging from the column was bubbled through diethyl ether/hexane (15:85; v:v; lOml), which was periodically assayed by electron capture GLC for the presence of dichloromethane.
The levels of dichloromethane passing through the columns in the absence of DTT were taken as controls.
When air saturated with dichloromethane (approx 400ppm) was passed through the column of alkali-modified cob~l~ ;n immobilised to QAE-Sephadex, approximately 92% of the dichloromethane was dehalogenated. Similarly, when air saturated with dichloromethane was passed through the column of alkali-modified cobal~l in immobilised to alkylamine-derivatized polystyrene beads, approximately 70% of the dichloromethane was dehalogenated.

6. Dehalogenation Apparatus Figs 1 and 2 show respectively apparatus for dehalogenation of aqueous or gaseous effluent.
The apparatus comprises a body (11, 21), having at its upper end an upper closure (12, 22) and at its lower end a lower closure (12A, 22A), the seals (13, 23) between the body (11, 21) and the closures (12, 12A, 22, 22A) being releasable but watertight or air-tight as appropriate. Each body (11, 21) is largely filled with polystyrene beads (14, 24) having immobilised thereon a corrin (eg the 3F product) retained in place in the body (11, 21) by retaining grids (15, 25).
In the lower closure (12A) are connected inlets (16), (17), through which flow may be controlled by valves (16A), (17A). The upper closure (12) is an outlet (18) flow through which may be controlled by a valve (18A~.
In the lower closure (22A) is an inlet (26), and an outlet (27), and flow through these may be controlled by valves (26A) and (27A). In the upper closure (22) there is an inlet (28), flow through which may be controlled by valve (28A). The tube (28) communicates with a sprinkler (29) inside the closure (22). There is also an outlet (30) in the closure (20), flow through which is controlled by a valve (30A).
An aqueous effluent to be dehalogenated is passed through inlet (16). A solution of a reducing agent is passed through inlet (17), mixing with the effluent. The mixture passes up the body (11) and contacts the beads (14), upon which dehalogenation takes place.
Dehalogenated effluent leaves via outlet (18).
A gaseous effluent to be dehalogenated is passed through inlet (26). At the same time a solution of a reducing agent is passed through inlet (28) so as to moisten all the beads (24) with the reducing solution. As the gaseous effluent contacts the beads (24), ` i dehalogenation of the effluent occurs, and dehalogenated effluent leaves via outlet (30). Excess reducing agent leaves via outlet (27) and may for example be treated with the apparatus of Fig 1 or otherwise disposed of.
The grids (15, 25) prevent escape of the beads (14, 24). The - effluent from outlets (18, 30) may be monitored, and when the beads(14, 24) appear to be exhausted, the seals (13, 23) may be released and a whole new body (11, 21) put in its place, ie as a replaceable dehalogenation cartridge.
References Wade R S & Castro C E J Am Chem Soc (1973) 95, 226-230.
Miskus R P, Blair D P & Casida J E J Agr Food Chem (1965) 13, 481-483.
Zoro J A, Hunter J M, Eglinton G, Ware G C, Nature (1974) 247, 235-237 Castro C E, J Am Chem Soc (Comm) (1964), 86, 2310-2311 Stotter D A, J-Inorg-Nucl Chem (1977), 39, 721-727 Ohisa N, Yamaguchi M, Kurihara N, Arch Microbiol (1980) 125, 221 Bieniek D, Mosa P N, Klein W and Korte F (1970), Tetrahedron Lett 47, 4055-4058 Jagnow G, Haider K, Ellwart P C, (1977), Arch-Microbiol, 115, 285 Bonnett R, Godfrey J M, Math V B J Chem Soc (C) (1971) 3736-3743 Gossauer A, Heise K, Cotze H, Inhoffen H, Liebigs Ann Chem (1977) Bormann D, Fischli A, Keese R, Eschenmoser A Angew Chem Int Edn (1967) 6(10) 868-871 Bieganowski R, Friedrich W, Z Naturforsch (1930) 36 9-15 Holze G, Gossauer A, Helv Chim Acta (1986) 69 1567-1570

Claims (14)

1. A method for dehalogenation of a halogenated organic compound, which comprises causing the compound to react with a reducing agent in the presence of a complex of a corrin containing a metal centred ring system of the formula:

wherein M is a metal atom or ion; A and B are coordinating ligands which may be the same or different; a and b are each O
or 1; R1 is NH2 or OH, R2 is H, CH2CH2COOH or CH2CH2CONH2, R3 is H, CH2CH2COOH or CH2CH2CONH2, and R4 is NHCH2CH(OH)CH3, OH
or NH2.

2. A method according to claim 1 wherein M is cobalt, nickel, molybdenum, iron or magnesium.

3. A method according claim 1 wherein A and B are each selected from the group consisting of ClO4-, CN-, SCN-, SO32-, H2O, Cl- and OH-.

4. A method according to claim 1 wherein the complex is selected from the group consisting of cyanocobalamin- SCN- or S2O32- complexes, conbinanide, neocobinanide, cobyric acid, neocobinamide, cobyric acid, neocobyric acid, cobyrinic acid, neocobyrinic acid or analogues of any of these in which the Co(CN)2 centre is replaced by a CoAB centre in which A and B
are each perchlorate, thiocyanate, sulphite, thiosulphate, water, hydroxyl or chloride.

5. A method according to claim 2 wherein M is cobalt and the complex is a product of the hydrolysis of cyanocobalamin (5A) or Neovitamin B12.

6. A method according to any one of claims 1 thorough 5, wherein the complex is immobilised on a water insoluble substrate.

7. A method according to claim 6 wherein the substrate is a derivatised polysaccharide, a polyacrylamide, polystryrene, a derivatised inorganic oxide or an ion-exchange resin.

8. A method according to any one of claims 1 through 5, wherein the dehalogenation is carried out at ambient temperature.

9. A method according to any one of claims 1 through 5 the dehalogenation is carried out at a temperature between 20°C and 80°C.

10. A method according to claim 9 wherein the dehalogenation is carried out at about 37°C.

11. A method according to any one of claims 1 through 5 wherein the dehalogenation is carried out at a pH of about 9.

12. A water-insoluble substrate having immobilised thereon a complex of the formula:

wherein M is a metal atom or ion A and B are coordinating ligands which may be the same or different; a and b are each 0 or 1; R1 is NH2 or OH, R2 is H, CH2CH2COOH or CH2CH2CONH2, R3 is H, CH2CH2COOH or CH2CH2CONH2, and R4 is NHCH2CH(OH)CH3, OH
or NH2:
the substrate being adapted for use in a method as in claim 6.

13. A substrate according to claim 12 wherein the substrate is a derivatised polysaccharide, a polyacrylamide, polystyrene, a derivatised inorganic oxide or an ion-exchange resin, and the complex of the corrin is cobalamin, cobyrinic acid or an isomer thereof, or a hydrolysis product of cyanocobalamin.

14. An apparatus for dehalogenation of a halogenated organic compound which comprises a bed of a water-insoluble substrate according to claim 12 or 13 contained within a body, the bed being capable of having a liquid or gas containing a halogenated organic compound passed therethrough.