CA2191580A1 - Water treatment - Google Patents
Water treatmentInfo
- Publication number
- CA2191580A1 CA2191580A1 CA002191580A CA2191580A CA2191580A1 CA 2191580 A1 CA2191580 A1 CA 2191580A1 CA 002191580 A CA002191580 A CA 002191580A CA 2191580 A CA2191580 A CA 2191580A CA 2191580 A1 CA2191580 A1 CA 2191580A1
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- CA
- Canada
- Prior art keywords
- water
- silver
- ligand
- silver ions
- organic ligand
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/50—Treatment of water, waste water, or sewage by addition or application of a germicide or by oligodynamic treatment
- C02F1/505—Treatment of water, waste water, or sewage by addition or application of a germicide or by oligodynamic treatment by oligodynamic treatment
-
- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
- A01N59/00—Biocides, pest repellants or attractants, or plant growth regulators containing elements or inorganic compounds
- A01N59/16—Heavy metals; Compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/4606—Treatment of water, waste water, or sewage by electrochemical methods for producing oligodynamic substances to disinfect the water
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Agronomy & Crop Science (AREA)
- Health & Medical Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Pest Control & Pesticides (AREA)
- Plant Pathology (AREA)
- Electrochemistry (AREA)
- Dentistry (AREA)
- General Health & Medical Sciences (AREA)
- Wood Science & Technology (AREA)
- Zoology (AREA)
- Environmental Sciences (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
Abstract
Water is treated with silver ions as an antimicrobial agent, accompanied by a complexing agent to render the silver ions more effective, more stable or both. The complexing agent is an organic ligand which forms a soluble complex with silver ions. Preferred are polymeric materials incorporating at least three carboxylate groups capable of coordinating to silver. Also preferred are amphoteric/zwitterionic surfactants and polyethers.
Description
~ W'096/01231 2 ~ ~ ~ 5 '~0 r~l ~ l540 W~TER T~A~M~NT
This invention relates to the hygienic treatment of water.
There are a number of applications where it is desirable to treat water so as to counteract any microbial cont~m;n~ntq therein. Frequently it is adequate to kill any such microbial cont~min~ntq.
A known techni~ue for doing this is to liberate silver ions into the water, by an electrochemical reaction.
Silver ions are known to have an antimicrobial action.
This use of electrochemically generated silver ions has been discussed in a number of literature articles including Spadaro et al Antimicrobial Agents and Chemotherapy 6, 637 - 642, (lg74).
Landeen et al Water Sci Tech 21, 267-70, (1989) Yahya et al Can. J. Microbiol 36 109-116, (1990) Pyle et al J. Applied Bacteriology 72. 71-9 (lg92) UK Patents 1507324 and 1512146.
The silver is normally liberated into a solution at a concentration which does noL exceed 0.1 parts per million (ppm~. It may be noted that standards for potable water in UK and USA impose limits of 0.08 and 0.05 ppm respectively. At such concentrations, silver is rather slow in its cell killing action.
Suppliers of equipment for the electrolytic liberation of silver ions into water are Tarn-Pure Limited, High Wycombe, England and Tarn-Pure USA, Las Vegas, Nevada, USA. As mentioned in the Yahya et al and Pyle et al articles, copper and silver ions may be generated together, using an anode which contains both metals.
WO96/01231 ~¦ q ~ PCT/GB95/01~40 -We have now found that silver can be rendered more effective or more stable or both by including ir. the water a material which is able to form a co-ordiration complex with the silver ions.
Accordinsly the present invention provides a method of killing microbial cmnt~mi n~n~ in water by introducing silver ior.s into solution in the water characterised by including in the water an organic ligand which is able to form a soluble co-ordination complex with the silver ions, especially an amphoteric or ~witterionic surfactant, a polyether, or a polycarboxylate.
The invention is particularly applicable when the silver lS ions are liberated into solution by the known step of electrochemical reaction, although the silver could conceivably be introduced into the water in some other way, such as by adding a solution of a silver salt.
~o The electrolytic liberation of silver ions requires apparatus which provides an electrolytic cell, with a silver-containing anode in contact with water to be treated. This water may be in contact also with the cathode, or the cathode may be located in diffe~ent electrolyte separated by a permeable memorane from the water Lo be treated.
The anode may be silver, or a silver alloy from which both silver ions and other ions are liberated.
Various metals may be used as the cathode. Stainless steel (which is an alloy principally containing iron, chromiùm and nickel) is satisfactory. Silver itself may usefully be used as She cathode, and the directior. of the current may be reversed periodically, so that both electrodes are consumed.
WO96101~1 ~ I q~ O PCT/GB95/01540 The water to be treated needs some conductivity. The concentration of ions which occur in normal water supplies is usually sufficient for this. If required, a small quantity of an electrolyte may be added to the water.
A considerable number of organic chemicals can serve as ligands able to form water soluble complexes with silver.
9uch ligands should have a functional group capable of taking a negative charge for co-ordinating to silver.
These groups will generally contain such heteroatoms as oxygen, sulphur and phosphorus. Examples of functional groups which bind to silver are thioethers, ethers, thiocarbonates, amines, imines, pyrazoles, benzimidazoles and phosphines. The ligands do not need to carry an overall negative charge. For instance zwitterionic molecules can serve as ligands.
One preferred category of material which is useful for forming co-ordination complexes is polycarboxylates, especially polycarboxylates wherein each ligand molecule contains at least three carboxylate groups able to co-ordinate to silver. Particularly suitable are oligomers and polymers bearir.g carboxylate groups such that a ligand molecule bears at least three carboxylate groups capable of co-ordinating to silver.
Such ligands display a high affinity for silver and can enhance the stability of the silver ions against precipitation by hydroxyl or chloride ions. Surprisingly, however, the coordination complexes of silver with such ligands also display good antimicrobialJbiocidal activity - which would not be expected when the silver is strongly bound by the ligand.
Preferably such ligands cor.tain an average of more than one carboxylate group per monomer residue in the oligomer or polymer. Such ligands may contain monomer residues W0961Q1231 r~ 5~1540 ~
J ~ a which each contribute a plurality of carboxylate groups.
Examples of such monomers are maleate, fumarate, itaconate, and aconitate.
It is preferred that the oligomers and polymers contain a majority of monomer residues bearing carboxylate groups, especially a ma~ority of monomer residues which, 2S
discussed, each contain a plurality of carboxylate groups.
A polycarboxylate will, usually, be made from olefinically unsaturated monomers. It may be a random or bloc~
copolymer. One or more monomers which bear a plurality of carboxylate groups, such as maleate, may be copolymerised with monomers which bear a single carboxylate grGup, such as acrylate or methacrylate. Other possible comonomers do not have ionisable carboxylate groups, as for example vinyl acetate.
A preferred category of monomers, which may provide 20 mole% or more, especially 50 mole% or more, Gf a poiymer or oligomer, have the formula R CH CO M
1\ / 2 2 1 = C
R2 CH2C02~12 wherein each of Rl and R2, which may be the same or different, represents a hydrogen atom, a methyl sroup or an ethyl group, and each of Ml and M2, which may be the same or different, is a hydrogen atom or a solubilising cation.
Itaconate is an example of such a monomer. Such mGnomers may be used to provide 20 to 95 mole % of a polymer or oligomer in which the residues of comonomer have the ~ WO 96101231 ~ J (~ a PCTIGB9S/01540 formula C 2 f wherein R3 represents a hydrogen atom or ar. acyl group -COR4 in which R4 i.s a C1 to C4 alk.yl group.
Polymeric ligands can be prepared by conventional polymerisation techniques. For example a procedure for the polymerisation of maleic anhydride is given by Lang et a in J. Polymer Sci. issue 16Z, page 532 (1961). The resulting polymer can readily be hydrolysed to polymaleate by treatment with aqueous sodium hydroxide.
In gereral, olefinically unsaturated acids and diacids can be polymerised alone or jointly with other olefinic monomers such as vinyl acetate by conventional techniques for radical polymerisation.
Polyitaconate homopolymers are described in US 3055 873 and 3405060. Copolymers with acrylic acid are disclosed in EP 506 246. Other polycarboxylates are described in EP 193 360 and US 4725655.
Polycarboxylates can also be obtained from monomers which do not contain olefinic unsaturation but instead undergo cnn~nq~tion polymerisation. Examples are malonate, isocitrate, citrate, succinate, tartrate, oxaloacetate, methylmalonate, carballylate, aspartate, glutamate and gamma-carboxyglutamate.
Another type of material which is useful as the organic ligand is amphoteric surfactants cnnt~ln;ng amino groups and carboxylate groups. Preferred among these are amphoteric surfactants containing at least two secondary amino groups as well as a carboxylate group.
WO 96101~31 PCI/GB9~101~0 q ~ ~ S ~
Amphoteric aurfactants will also generally incorporate an alkyl or alkenyl chain of 7 to 18 carbon atoms.
Yet another type of material which may be used aa the organic ligand is a betaine notably amido betaines of formula:
_ '+
R4 CONE~- (CH2) n~~\ -CH2-C02 rn both formulae R4 is a C7 to C18 straight or branched alkyl or alkenyl group; R5 and R6 are each C1 to C-3 alkyl or C1 to C3 hydroxyalkyl. n is 2 to 4 especially 3.
This invention relates to the hygienic treatment of water.
There are a number of applications where it is desirable to treat water so as to counteract any microbial cont~m;n~ntq therein. Frequently it is adequate to kill any such microbial cont~min~ntq.
A known techni~ue for doing this is to liberate silver ions into the water, by an electrochemical reaction.
Silver ions are known to have an antimicrobial action.
This use of electrochemically generated silver ions has been discussed in a number of literature articles including Spadaro et al Antimicrobial Agents and Chemotherapy 6, 637 - 642, (lg74).
Landeen et al Water Sci Tech 21, 267-70, (1989) Yahya et al Can. J. Microbiol 36 109-116, (1990) Pyle et al J. Applied Bacteriology 72. 71-9 (lg92) UK Patents 1507324 and 1512146.
The silver is normally liberated into a solution at a concentration which does noL exceed 0.1 parts per million (ppm~. It may be noted that standards for potable water in UK and USA impose limits of 0.08 and 0.05 ppm respectively. At such concentrations, silver is rather slow in its cell killing action.
Suppliers of equipment for the electrolytic liberation of silver ions into water are Tarn-Pure Limited, High Wycombe, England and Tarn-Pure USA, Las Vegas, Nevada, USA. As mentioned in the Yahya et al and Pyle et al articles, copper and silver ions may be generated together, using an anode which contains both metals.
WO96/01231 ~¦ q ~ PCT/GB95/01~40 -We have now found that silver can be rendered more effective or more stable or both by including ir. the water a material which is able to form a co-ordiration complex with the silver ions.
Accordinsly the present invention provides a method of killing microbial cmnt~mi n~n~ in water by introducing silver ior.s into solution in the water characterised by including in the water an organic ligand which is able to form a soluble co-ordination complex with the silver ions, especially an amphoteric or ~witterionic surfactant, a polyether, or a polycarboxylate.
The invention is particularly applicable when the silver lS ions are liberated into solution by the known step of electrochemical reaction, although the silver could conceivably be introduced into the water in some other way, such as by adding a solution of a silver salt.
~o The electrolytic liberation of silver ions requires apparatus which provides an electrolytic cell, with a silver-containing anode in contact with water to be treated. This water may be in contact also with the cathode, or the cathode may be located in diffe~ent electrolyte separated by a permeable memorane from the water Lo be treated.
The anode may be silver, or a silver alloy from which both silver ions and other ions are liberated.
Various metals may be used as the cathode. Stainless steel (which is an alloy principally containing iron, chromiùm and nickel) is satisfactory. Silver itself may usefully be used as She cathode, and the directior. of the current may be reversed periodically, so that both electrodes are consumed.
WO96101~1 ~ I q~ O PCT/GB95/01540 The water to be treated needs some conductivity. The concentration of ions which occur in normal water supplies is usually sufficient for this. If required, a small quantity of an electrolyte may be added to the water.
A considerable number of organic chemicals can serve as ligands able to form water soluble complexes with silver.
9uch ligands should have a functional group capable of taking a negative charge for co-ordinating to silver.
These groups will generally contain such heteroatoms as oxygen, sulphur and phosphorus. Examples of functional groups which bind to silver are thioethers, ethers, thiocarbonates, amines, imines, pyrazoles, benzimidazoles and phosphines. The ligands do not need to carry an overall negative charge. For instance zwitterionic molecules can serve as ligands.
One preferred category of material which is useful for forming co-ordination complexes is polycarboxylates, especially polycarboxylates wherein each ligand molecule contains at least three carboxylate groups able to co-ordinate to silver. Particularly suitable are oligomers and polymers bearir.g carboxylate groups such that a ligand molecule bears at least three carboxylate groups capable of co-ordinating to silver.
Such ligands display a high affinity for silver and can enhance the stability of the silver ions against precipitation by hydroxyl or chloride ions. Surprisingly, however, the coordination complexes of silver with such ligands also display good antimicrobialJbiocidal activity - which would not be expected when the silver is strongly bound by the ligand.
Preferably such ligands cor.tain an average of more than one carboxylate group per monomer residue in the oligomer or polymer. Such ligands may contain monomer residues W0961Q1231 r~ 5~1540 ~
J ~ a which each contribute a plurality of carboxylate groups.
Examples of such monomers are maleate, fumarate, itaconate, and aconitate.
It is preferred that the oligomers and polymers contain a majority of monomer residues bearing carboxylate groups, especially a ma~ority of monomer residues which, 2S
discussed, each contain a plurality of carboxylate groups.
A polycarboxylate will, usually, be made from olefinically unsaturated monomers. It may be a random or bloc~
copolymer. One or more monomers which bear a plurality of carboxylate groups, such as maleate, may be copolymerised with monomers which bear a single carboxylate grGup, such as acrylate or methacrylate. Other possible comonomers do not have ionisable carboxylate groups, as for example vinyl acetate.
A preferred category of monomers, which may provide 20 mole% or more, especially 50 mole% or more, Gf a poiymer or oligomer, have the formula R CH CO M
1\ / 2 2 1 = C
R2 CH2C02~12 wherein each of Rl and R2, which may be the same or different, represents a hydrogen atom, a methyl sroup or an ethyl group, and each of Ml and M2, which may be the same or different, is a hydrogen atom or a solubilising cation.
Itaconate is an example of such a monomer. Such mGnomers may be used to provide 20 to 95 mole % of a polymer or oligomer in which the residues of comonomer have the ~ WO 96101231 ~ J (~ a PCTIGB9S/01540 formula C 2 f wherein R3 represents a hydrogen atom or ar. acyl group -COR4 in which R4 i.s a C1 to C4 alk.yl group.
Polymeric ligands can be prepared by conventional polymerisation techniques. For example a procedure for the polymerisation of maleic anhydride is given by Lang et a in J. Polymer Sci. issue 16Z, page 532 (1961). The resulting polymer can readily be hydrolysed to polymaleate by treatment with aqueous sodium hydroxide.
In gereral, olefinically unsaturated acids and diacids can be polymerised alone or jointly with other olefinic monomers such as vinyl acetate by conventional techniques for radical polymerisation.
Polyitaconate homopolymers are described in US 3055 873 and 3405060. Copolymers with acrylic acid are disclosed in EP 506 246. Other polycarboxylates are described in EP 193 360 and US 4725655.
Polycarboxylates can also be obtained from monomers which do not contain olefinic unsaturation but instead undergo cnn~nq~tion polymerisation. Examples are malonate, isocitrate, citrate, succinate, tartrate, oxaloacetate, methylmalonate, carballylate, aspartate, glutamate and gamma-carboxyglutamate.
Another type of material which is useful as the organic ligand is amphoteric surfactants cnnt~ln;ng amino groups and carboxylate groups. Preferred among these are amphoteric surfactants containing at least two secondary amino groups as well as a carboxylate group.
WO 96101~31 PCI/GB9~101~0 q ~ ~ S ~
Amphoteric aurfactants will also generally incorporate an alkyl or alkenyl chain of 7 to 18 carbon atoms.
Yet another type of material which may be used aa the organic ligand is a betaine notably amido betaines of formula:
_ '+
R4 CONE~- (CH2) n~~\ -CH2-C02 rn both formulae R4 is a C7 to C18 straight or branched alkyl or alkenyl group; R5 and R6 are each C1 to C-3 alkyl or C1 to C3 hydroxyalkyl. n is 2 to 4 especially 3.
2~ Correaponding sulphobetaines have the abo~re formula with -CH2CO2 replaced by OH
-(CH213SO3 or -C~2-CHCH2 SO3 A further category o~ materials useful as organic ligands are a group of naturally occurring antibiotics known as 3~ polyether ionophores. These ~olecules incorporate a number of oxygen atoms, freguently in furan and pyran rings so that they are polyethers. They are known to have cation complexing properties.
A review and listing of such materials is provided in "Polyester antibiotics" edited by J.W. Westley.
Ideally water treatment in accordance with this invention is carried out using the organic ligand and silver ions in such quantities that complexing of the silver is not restricted by shortage of ligand.
~ W096/01231 r~ 0 I 5 ~3 0 In practice some surplus of ligand will usually be harmless, while the benefit of the invention will be obtained in part if there is some surplus of silver ions in solution. Conseauently it is preferred that substantially all the silver is in the form of a complex, and is accompanied by surplus ligand.
Usually th.e mole ratio of silver to ligand will be from lO:l up to l:lOO. Preferably there will be enough ligand to provide the stoichiometric equivalent of the concentration of silver ions so that the silver to ligand mole ratio lies in a range from l:l to l:lOO. Frequently the concentration of organic ligand will lie in a range from O.OOl or 0.005 to 3,000 ppm, especially 0.5 or lppm up to 500 ppm. Concentrations of ligand higher than 3,000 ppm may be employed if desired.
The concentration of silver which is maintained in the water will frequently lie in a broad range from O.OOl to lOOO ppm, especially O.Ol or O.l to lOO ppm. The concentration more preferably does not exceed 25 ppm.
If the invention is applied to tr.e treatmer.t of a body of water which is kept for a lonc time - notably a body of water which is kept in circulation, such as the water of a swimming pool or an air conditioning system, a single addition of ligand to the water may suffice for a long period.
On the other hand if the water is being consumed and replaced, the organic ligand will have to be added to it regularly or continuously, and the introduction of silver ions, preferably by electrolytic liberation, will need to be regular or continuous.
W096101231 ~ PCT/GB9$/U1~4U ~
~ 7 '7 1 ~ ~ O
F.~nle l.
Silver ions were generated electrolytlcally in water, and in aqueous solutions of an organic ligand. A control has water with nelther silver nor organic ligand present. The water, which was also used for the preparation of the ligand solutions, was sterlle distilled water to which had been added a very small crystal of sodium sulphate to confer conductivity. The ligand was a commercial mixture of amphoteric surfactants of formulae CIZH2s-NH- (cH2) 3-NHCH2C02~-and C12H2s-NH-(CH2)-NH-(CH2)-NHCH2C02H
available as Amphobac 4 from Lonza Inc. It was used at concentrations of 2ppm and ~Oppm.
Silver was generated electrolytically, using a pair of silver wires dipping into the water or ligar.d solution as electrodes. These were connected to a cor.stant current direct current supply, for sufficient time to liberate 3 ppm silver ions ir.to solution.
lOml volumes of each solution were ther. inoculated with O-l ml of an ar~ueous suspension containing five species of microorganism, and thoroughly mixed. The five species were four bacteria, namely Staphylococcus aureas, Streptococcus faecalis, Pse11~r~n~ aeruginosa and ~roteus mirabilis and a yeast, Saccharomyces cerevisiae.
After a period of 5 minutes a l ml portion was removed and transferred to a qnrnr~;ng solution containing sufficient sodium thiosulphate to precipitate the silver ions. In a separate test, the e~fect of sodium thiosulphate on the microorganisms was checked: it was found that it did not reduce their ~iability.
The quantities of surviving micro organisms were determined by serial dilutior., spreading the diluted ~ WO9~/01231 2 1 ~iJ ~ r~ v.''0l540 solution on an agar plate, incubating and counting the number of colonies of each species. From this count, and the extent of dilution, the concer.tration of surviving micro organisms in the test solution was calculated.
The results are set out in the followins table and are given as the logarithm of th.e number of survivors.
.
logl~ cells survivirg after 5 minutes staphyl- strept- pseudo- proteus yeast ococcus ococcus monas water 7.44 6.77 7.81 8.Q3 5.45 electrolytic 3.14 4.06 3.32 2.69 <2 silver Amphobac4, 7.23 6.90 7.14 7.32 3.00 2ppm Amphobac4, 2ppm +
electrolytic c2 <2 3.30 <2 <2 silver Amphobac4, 3.50 2.00 4.60 5.38 <2 20pDm Amphobac4, 2Oppm +
electrolytic c2 c2 <2 <2 <2 silver As can be seen from the above table, electrochemically liberated silver reduces the microorganism concentratior.s by three or four orders of magnitude, but a conslderably greater reduction is achieved when the organic ligand is also present.
Wo96JOI~1 , ~ 71 ~ & ~ PCT/GB9~01 Fx~Tle 2 The procedure cf Exa~ple 1 was repeated, using ~asalocid as organic ligand, at a concentration of l~ppm. T,asalocid is a polyether anti~iotic or for~ula ~;-ONa H CHsCH3~,~C~H2CH3,~CH2CH3 Cl l,~O~CH2C~t3 ~ WO96/01~1 P~ 41~
21 ~ i ~8i~
Results are given in Table 2 below.
T~3LE 2 log1~ surviving cells after 5 minutes staphyl- strept- pseudo- proteus yeast ococcus ococcus monas water 7.57 6.85 ~.01 7.52 5.54 electrolytic 3.51. 4.96 5.83 ~2 ~2 silver Lasalocid, 3.54 3.50 3.43 3.23 ~2 15ppm Lasalocid, 15ppm +
electrolytic c2 ~2 2.90 3.30 c2 silver WO96~01~1 ~ PCT/GB9.5101~40 Exam~le ' The procedure of Example l was repeated uEing a longer contact time, using E.coli and Staph aureus aa the microoraanism species, and using an amidopropyl be~aine as ligand. This had the formula C13H~ O~ CH2) 3 N~-CH~C03-and was used at a concentration of lO ppm so as to provide an excess of ligand over silver. It is available as Tegobetaine from ~oldschmidt.
The silver concentration was 2 ppm.
The results obtained were:
log.~ surviv;na cells after l hour E.coli 9t. aureua water 7.07 6.49 Tegobetaine 6.36 3.47 ~5 Silver 2.61 2.91 Silver + Tegobetaine <l 1.60 ~wog6/0l23l 2 ~ o r~"~ .;01540 ~r~le 4 A copolymer was prepared from 20 mole % vinyl acetate and 80 mole ~ itacor.ic acid.
This polymer had the formula CH2COONa COONa OR3 n m wherein R3 indicates an acetyl group, and the indices n and m indicate the numbers of repeating units.
Vinyl acetate ~9.4ml, 0.1 mole), itaconic acid (48g, 0.4 mol) and degassed water (200 ml) were charged into a flange flask and stirred at 40~C under a nitroger.
atmosphere. The redox initiator, comprising sodium persulphate (0.8g~ and sodium metabisulphite (0.4g), was added in three. increments each of 0.3g over four days.
The polymer-contair.ing solution was concentrated to approximately half volume using a rotary evaporator and the concentrate poured into acetone. This precipitated the polymer which was washed with portions of acetone. A
small sample was taken for analysis and molecular weight determination. The copolymer was then dissolved in water, neutralised with 6% sodium hydroxide solution to a pH of 8.5 and freeze dried.
The procedure of Example 3 was repeated using the copolymer as the ligand, at a concentration of 16 ppm, again providir.g an excess of ligand over silver.
WO96/01231 2 ~ G PCrl~BgS101540 The results obtained were log.O s~rvivinq cells ~fter 1 hott~
E.coli St. aureus water 7.G7 6.49 Copolymer 6.36 5.49 Silver 2.61 2.91 Silver + Copolymer cl 3.07 It can be seen that the copolymer enhanced the activity agairLst E.coli without signi~icant deteriment to the activity against St. aureus.
~ WO96~1231 2 1 9 I S g ~ r~ ol~o rle S
lOOg of the polyitaconate-vinyl acetate copolymer in sodium salt form, as in the previous Example, was dissolved in 500ml water. Silver nitrate (30g) dissolved in 80ml water was added over about 5 minutes. The whole mixture was stirred for twenty minutes and then e~hanol ~1.5 litre) was added. A fine white precipitate formed, which was filtered off and dried.
Analysis by 1H n.m.r in deuterium oxide confirmed presence of the polyitaconate-vinyl acetate copolymer. Silver analysis by silver selective electrode showed 15~ silver by weight. Analysis was confirmed by atomic absorption spectroscopy.
0.25g of the above complex was dissolved in 250ml dilute acid to yield a solution containing 1000 ppm of the complex. Sodium hydroxide solution was slowly added.
~easurements were made of pH and simultaneous measurements were made of free silver ion concentration. At pH 5 all the silver ions were in solution. Increasing alkalinity reduced the concentration of free silver as ionisation of the polymer enabled it to complex with silver ions. The pH was progressively increased to pH 10.5 without precipitation occurring. This absence of precipieation was shown by the optical transmission, which remained constant.
By contrastl a solution of silver nitrate (11 ppm) was rendered alkaline. At pH 8.0 or greater a brown precipitate of silver oxide was observed.
WO96/01231 ~ 80 F~l, D~
~ rle 6 The stability of the above complex towards cAloride ion was compared with the stability of silver nitrate.
To 25ml of an aqueous solution containing 11 ppm silver nitrate (1.63 x 10 6 moles) was added lml of 0.005M
potassium chloride solution ~i.e. 5 x 10 6 moles). The concentration of free silver ion dropped to cO.3 ppm (limit of detection by apparatus) due to precipitation of insoluble silver chloride. The optical transmission of the solution dropped immediately from 100~ to 70~ relative to distilled water due to the formation of a silver chloride precipitate.
A sample of silver polyitaconate-vinyl acetate complex, prepared in Example 5, 10.133~) was dissolved in 25ml water. This contained about 1.8 x 10 4 gram atoms of silver and represents a total silver concentration of about 800 ppm. However, the measured free silver ion Z0 concentration was only 5.2 ppm. To tAis solution was added lml of 0.005~ potassium chloride solution ~i.e. 5 x 10 6 moles~. The concentration of free silver ion dropped to 4.5 ppm. The optical transmission of the solution changed from 99~ to 99.5~ relative to di6tilled water. No insoluble particles were observed.
A further sample of the same complex ~16.6 m~) was dissolved in 25ml water, made alkallne to p~ 10 with sodium hydroxide solution. This was about 10 gram atoms of silver and a silver concentration of lOOppm.
An excess of potassium chloride solution was added llml of O.lM solution) - 10 moles. TAere was no visible formation of precipitate during a period of tAirty minutes.
~ WO96101231 ~ 5 (S 0 PCT1GB951015~0 Examole 7 An aqueo~s suspension was prepared ccntaining Candida parapsilopsis (yeast), Penicillium and Aspergillus spores (mould) Escherichia coli (Gram negative bacterium) and Staphylococcus aureus (Gram positive bacterium).
lml of this suspension was mixed with 9ml of an aaueous solution of the silver complex of Exampie l, containing l0 ppm silver. As a comparison a similar portion was mixed with an aqueous solution of the ligand only. As a control, a third portion was treated with water only.
After 30 minutes the numbers of surviving organisms were determined by serial dilution, plating on agar growth media and counting viable colonies.
The results obtained were as set out in the following table which shows that the ligand alone had no antimicrobial action whereas the silver complex was highly effective.
TF.EATMENT LOG1~ SURVI~ORS AFTER 30 MINS CONTACT
CANDIDA MOULDS E.COLI S. AUREUS
ITACONATE 5.61 6.14 7.54 7.63 COPOLYMER
30 ITACONATE ~l 1.60 POLYMER + Ag ~ATER 5.6g 5.47 7.49 7.25
-(CH213SO3 or -C~2-CHCH2 SO3 A further category o~ materials useful as organic ligands are a group of naturally occurring antibiotics known as 3~ polyether ionophores. These ~olecules incorporate a number of oxygen atoms, freguently in furan and pyran rings so that they are polyethers. They are known to have cation complexing properties.
A review and listing of such materials is provided in "Polyester antibiotics" edited by J.W. Westley.
Ideally water treatment in accordance with this invention is carried out using the organic ligand and silver ions in such quantities that complexing of the silver is not restricted by shortage of ligand.
~ W096/01231 r~ 0 I 5 ~3 0 In practice some surplus of ligand will usually be harmless, while the benefit of the invention will be obtained in part if there is some surplus of silver ions in solution. Conseauently it is preferred that substantially all the silver is in the form of a complex, and is accompanied by surplus ligand.
Usually th.e mole ratio of silver to ligand will be from lO:l up to l:lOO. Preferably there will be enough ligand to provide the stoichiometric equivalent of the concentration of silver ions so that the silver to ligand mole ratio lies in a range from l:l to l:lOO. Frequently the concentration of organic ligand will lie in a range from O.OOl or 0.005 to 3,000 ppm, especially 0.5 or lppm up to 500 ppm. Concentrations of ligand higher than 3,000 ppm may be employed if desired.
The concentration of silver which is maintained in the water will frequently lie in a broad range from O.OOl to lOOO ppm, especially O.Ol or O.l to lOO ppm. The concentration more preferably does not exceed 25 ppm.
If the invention is applied to tr.e treatmer.t of a body of water which is kept for a lonc time - notably a body of water which is kept in circulation, such as the water of a swimming pool or an air conditioning system, a single addition of ligand to the water may suffice for a long period.
On the other hand if the water is being consumed and replaced, the organic ligand will have to be added to it regularly or continuously, and the introduction of silver ions, preferably by electrolytic liberation, will need to be regular or continuous.
W096101231 ~ PCT/GB9$/U1~4U ~
~ 7 '7 1 ~ ~ O
F.~nle l.
Silver ions were generated electrolytlcally in water, and in aqueous solutions of an organic ligand. A control has water with nelther silver nor organic ligand present. The water, which was also used for the preparation of the ligand solutions, was sterlle distilled water to which had been added a very small crystal of sodium sulphate to confer conductivity. The ligand was a commercial mixture of amphoteric surfactants of formulae CIZH2s-NH- (cH2) 3-NHCH2C02~-and C12H2s-NH-(CH2)-NH-(CH2)-NHCH2C02H
available as Amphobac 4 from Lonza Inc. It was used at concentrations of 2ppm and ~Oppm.
Silver was generated electrolytically, using a pair of silver wires dipping into the water or ligar.d solution as electrodes. These were connected to a cor.stant current direct current supply, for sufficient time to liberate 3 ppm silver ions ir.to solution.
lOml volumes of each solution were ther. inoculated with O-l ml of an ar~ueous suspension containing five species of microorganism, and thoroughly mixed. The five species were four bacteria, namely Staphylococcus aureas, Streptococcus faecalis, Pse11~r~n~ aeruginosa and ~roteus mirabilis and a yeast, Saccharomyces cerevisiae.
After a period of 5 minutes a l ml portion was removed and transferred to a qnrnr~;ng solution containing sufficient sodium thiosulphate to precipitate the silver ions. In a separate test, the e~fect of sodium thiosulphate on the microorganisms was checked: it was found that it did not reduce their ~iability.
The quantities of surviving micro organisms were determined by serial dilutior., spreading the diluted ~ WO9~/01231 2 1 ~iJ ~ r~ v.''0l540 solution on an agar plate, incubating and counting the number of colonies of each species. From this count, and the extent of dilution, the concer.tration of surviving micro organisms in the test solution was calculated.
The results are set out in the followins table and are given as the logarithm of th.e number of survivors.
.
logl~ cells survivirg after 5 minutes staphyl- strept- pseudo- proteus yeast ococcus ococcus monas water 7.44 6.77 7.81 8.Q3 5.45 electrolytic 3.14 4.06 3.32 2.69 <2 silver Amphobac4, 7.23 6.90 7.14 7.32 3.00 2ppm Amphobac4, 2ppm +
electrolytic c2 <2 3.30 <2 <2 silver Amphobac4, 3.50 2.00 4.60 5.38 <2 20pDm Amphobac4, 2Oppm +
electrolytic c2 c2 <2 <2 <2 silver As can be seen from the above table, electrochemically liberated silver reduces the microorganism concentratior.s by three or four orders of magnitude, but a conslderably greater reduction is achieved when the organic ligand is also present.
Wo96JOI~1 , ~ 71 ~ & ~ PCT/GB9~01 Fx~Tle 2 The procedure cf Exa~ple 1 was repeated, using ~asalocid as organic ligand, at a concentration of l~ppm. T,asalocid is a polyether anti~iotic or for~ula ~;-ONa H CHsCH3~,~C~H2CH3,~CH2CH3 Cl l,~O~CH2C~t3 ~ WO96/01~1 P~ 41~
21 ~ i ~8i~
Results are given in Table 2 below.
T~3LE 2 log1~ surviving cells after 5 minutes staphyl- strept- pseudo- proteus yeast ococcus ococcus monas water 7.57 6.85 ~.01 7.52 5.54 electrolytic 3.51. 4.96 5.83 ~2 ~2 silver Lasalocid, 3.54 3.50 3.43 3.23 ~2 15ppm Lasalocid, 15ppm +
electrolytic c2 ~2 2.90 3.30 c2 silver WO96~01~1 ~ PCT/GB9.5101~40 Exam~le ' The procedure of Example l was repeated uEing a longer contact time, using E.coli and Staph aureus aa the microoraanism species, and using an amidopropyl be~aine as ligand. This had the formula C13H~ O~ CH2) 3 N~-CH~C03-and was used at a concentration of lO ppm so as to provide an excess of ligand over silver. It is available as Tegobetaine from ~oldschmidt.
The silver concentration was 2 ppm.
The results obtained were:
log.~ surviv;na cells after l hour E.coli 9t. aureua water 7.07 6.49 Tegobetaine 6.36 3.47 ~5 Silver 2.61 2.91 Silver + Tegobetaine <l 1.60 ~wog6/0l23l 2 ~ o r~"~ .;01540 ~r~le 4 A copolymer was prepared from 20 mole % vinyl acetate and 80 mole ~ itacor.ic acid.
This polymer had the formula CH2COONa COONa OR3 n m wherein R3 indicates an acetyl group, and the indices n and m indicate the numbers of repeating units.
Vinyl acetate ~9.4ml, 0.1 mole), itaconic acid (48g, 0.4 mol) and degassed water (200 ml) were charged into a flange flask and stirred at 40~C under a nitroger.
atmosphere. The redox initiator, comprising sodium persulphate (0.8g~ and sodium metabisulphite (0.4g), was added in three. increments each of 0.3g over four days.
The polymer-contair.ing solution was concentrated to approximately half volume using a rotary evaporator and the concentrate poured into acetone. This precipitated the polymer which was washed with portions of acetone. A
small sample was taken for analysis and molecular weight determination. The copolymer was then dissolved in water, neutralised with 6% sodium hydroxide solution to a pH of 8.5 and freeze dried.
The procedure of Example 3 was repeated using the copolymer as the ligand, at a concentration of 16 ppm, again providir.g an excess of ligand over silver.
WO96/01231 2 ~ G PCrl~BgS101540 The results obtained were log.O s~rvivinq cells ~fter 1 hott~
E.coli St. aureus water 7.G7 6.49 Copolymer 6.36 5.49 Silver 2.61 2.91 Silver + Copolymer cl 3.07 It can be seen that the copolymer enhanced the activity agairLst E.coli without signi~icant deteriment to the activity against St. aureus.
~ WO96~1231 2 1 9 I S g ~ r~ ol~o rle S
lOOg of the polyitaconate-vinyl acetate copolymer in sodium salt form, as in the previous Example, was dissolved in 500ml water. Silver nitrate (30g) dissolved in 80ml water was added over about 5 minutes. The whole mixture was stirred for twenty minutes and then e~hanol ~1.5 litre) was added. A fine white precipitate formed, which was filtered off and dried.
Analysis by 1H n.m.r in deuterium oxide confirmed presence of the polyitaconate-vinyl acetate copolymer. Silver analysis by silver selective electrode showed 15~ silver by weight. Analysis was confirmed by atomic absorption spectroscopy.
0.25g of the above complex was dissolved in 250ml dilute acid to yield a solution containing 1000 ppm of the complex. Sodium hydroxide solution was slowly added.
~easurements were made of pH and simultaneous measurements were made of free silver ion concentration. At pH 5 all the silver ions were in solution. Increasing alkalinity reduced the concentration of free silver as ionisation of the polymer enabled it to complex with silver ions. The pH was progressively increased to pH 10.5 without precipitation occurring. This absence of precipieation was shown by the optical transmission, which remained constant.
By contrastl a solution of silver nitrate (11 ppm) was rendered alkaline. At pH 8.0 or greater a brown precipitate of silver oxide was observed.
WO96/01231 ~ 80 F~l, D~
~ rle 6 The stability of the above complex towards cAloride ion was compared with the stability of silver nitrate.
To 25ml of an aqueous solution containing 11 ppm silver nitrate (1.63 x 10 6 moles) was added lml of 0.005M
potassium chloride solution ~i.e. 5 x 10 6 moles). The concentration of free silver ion dropped to cO.3 ppm (limit of detection by apparatus) due to precipitation of insoluble silver chloride. The optical transmission of the solution dropped immediately from 100~ to 70~ relative to distilled water due to the formation of a silver chloride precipitate.
A sample of silver polyitaconate-vinyl acetate complex, prepared in Example 5, 10.133~) was dissolved in 25ml water. This contained about 1.8 x 10 4 gram atoms of silver and represents a total silver concentration of about 800 ppm. However, the measured free silver ion Z0 concentration was only 5.2 ppm. To tAis solution was added lml of 0.005~ potassium chloride solution ~i.e. 5 x 10 6 moles~. The concentration of free silver ion dropped to 4.5 ppm. The optical transmission of the solution changed from 99~ to 99.5~ relative to di6tilled water. No insoluble particles were observed.
A further sample of the same complex ~16.6 m~) was dissolved in 25ml water, made alkallne to p~ 10 with sodium hydroxide solution. This was about 10 gram atoms of silver and a silver concentration of lOOppm.
An excess of potassium chloride solution was added llml of O.lM solution) - 10 moles. TAere was no visible formation of precipitate during a period of tAirty minutes.
~ WO96101231 ~ 5 (S 0 PCT1GB951015~0 Examole 7 An aqueo~s suspension was prepared ccntaining Candida parapsilopsis (yeast), Penicillium and Aspergillus spores (mould) Escherichia coli (Gram negative bacterium) and Staphylococcus aureus (Gram positive bacterium).
lml of this suspension was mixed with 9ml of an aaueous solution of the silver complex of Exampie l, containing l0 ppm silver. As a comparison a similar portion was mixed with an aqueous solution of the ligand only. As a control, a third portion was treated with water only.
After 30 minutes the numbers of surviving organisms were determined by serial dilution, plating on agar growth media and counting viable colonies.
The results obtained were as set out in the following table which shows that the ligand alone had no antimicrobial action whereas the silver complex was highly effective.
TF.EATMENT LOG1~ SURVI~ORS AFTER 30 MINS CONTACT
CANDIDA MOULDS E.COLI S. AUREUS
ITACONATE 5.61 6.14 7.54 7.63 COPOLYMER
30 ITACONATE ~l 1.60 POLYMER + Ag ~ATER 5.6g 5.47 7.49 7.25
Claims (16)
1. A method of killing microbial contaminants in water by introducing silver ions into solution in the water, characterised by including in the water an organic ligand which forms a water-soluble co-ordination complex with the silver ions.
2. A method according to claim 1 wherein the silver ions are liberated into solution in the water by electrochemical reactions.
3. A method according to claim 1 or claim 2 wherein the concentration of silver ions in the water lies in the range 0.01 to 100 ppm, and the mole ratio of silver ions to ligand which is able to form a said complex therewith is from 10:1 up to 1:100.
4. A method according to claim 3 wherein the concentration of silver ions in the water does not exceed 50 ppm.
5. A method according to claim 3 wherein the concentration of organic ligand in the water lies in the range 0.01 to 3000 ppm.
6. A method according to claim 3 wherein the concentration of organic ligand in the water lies in the range 0.01 to 500 ppm.
7. A method according to claim 3 wherein the mole ratio of silver ions to ligand which is able to form a said complex therewith lies in a range from 1:1 to 1:100.
8. A method according to claim 1 wherein the organic ligand is an amphoteric or zwitterionic surfactant, a polyether, or a polycarboxylate.
9. A method according to claim 1 wherein the organic ligand is an amphoteric or zwitterionic surfactant containing an alkyl or alkenyl chain of 7 to 18 carbon atoms.
10. A method according to claim 1 wherein the organic ligand is a polyether.
11. A method according to claim 1 wherein the organic ligand is a polycarboxylate wherein each ligand molecule contains at least three carboxylate groups capable of co-ordinating to silver.
12. A method according to claim 11 wherein the ligand is a oligomer or polymer of one or more olefinically unsaturated monomers, and which contains an average of at least 1 carboxylate group per monomer residue.
13. A method according to claim 12 wherein at least 30 mole % of the monomer residues include one or more carboxylate groups.
14. A method according to claim 12 wherein the organic ligand comprises at least 20 mole % of monomer residues of the formula I
wherein each of R1 and R2, which may be the same or different. represents a hydrogen atom, a methyl group or an ethyl group, and each of M1 and M2, which may be the same or different, is a hydrogen atom or a solubilising cation.
wherein each of R1 and R2, which may be the same or different. represents a hydrogen atom, a methyl group or an ethyl group, and each of M1 and M2, which may be the same or different, is a hydrogen atom or a solubilising cation.
15. A method according to claim 12 wherein the ligand is a block copolymer comprising (i) from 20 to 95 mole % of monomer units of the formula I
wherein each of R1 and R2, which may be the same or different, represents a hydrogen atom, a methyl group or an ethyl group, and each of M1 and M2, which may be the same or different, is a hydrogen atom or a solubilising cation; and (ii) from 5 to 80 mole % of monomer residues of the formula II:
wherein R3 represents a hydrogen atom or the group -COR4, wherein R4 is an alkyl group of 1 to 4 carbon atoms.
wherein each of R1 and R2, which may be the same or different, represents a hydrogen atom, a methyl group or an ethyl group, and each of M1 and M2, which may be the same or different, is a hydrogen atom or a solubilising cation; and (ii) from 5 to 80 mole % of monomer residues of the formula II:
wherein R3 represents a hydrogen atom or the group -COR4, wherein R4 is an alkyl group of 1 to 4 carbon atoms.
16. A method according to claim 15 wherein R4 in the formula II represents a methyl group.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9413299A GB9413299D0 (en) | 1994-07-01 | 1994-07-01 | Water treatment |
| GB9413299.0 | 1994-07-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2191580A1 true CA2191580A1 (en) | 1996-01-18 |
Family
ID=10757683
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002191580A Abandoned CA2191580A1 (en) | 1994-07-01 | 1995-06-29 | Water treatment |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0768987A1 (en) |
| AU (1) | AU2801595A (en) |
| BR (1) | BR9508174A (en) |
| CA (1) | CA2191580A1 (en) |
| GB (1) | GB9413299D0 (en) |
| TR (1) | TR199500775A2 (en) |
| WO (1) | WO1996001231A1 (en) |
| ZA (1) | ZA955353B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2318349A (en) * | 1996-10-15 | 1998-04-22 | Gyre Ltd | Biocidal composition for wet environment |
| AU4770599A (en) * | 1998-05-29 | 1999-12-13 | Corby, Michael Peter | Lubricant compositions |
| US6242009B1 (en) | 1999-04-20 | 2001-06-05 | Kareem I. Batarseh | Microbicidal formulations and methods to control microorganisms |
| US6630172B2 (en) | 2001-01-22 | 2003-10-07 | Kareem I. Batarseh | Microbicidal composition containing potassium sodium tartrate |
| DE10130298A1 (en) | 2001-06-22 | 2003-01-23 | Nutrinova Gmbh | Antimicrobial acesulfame complexes, process for their preparation and their use |
| GB2402880B (en) * | 2003-06-20 | 2008-01-23 | Johnson & Johnson Medical Ltd | Antimicrobial compositions comprising silver |
| US9180229B2 (en) * | 2005-05-19 | 2015-11-10 | Ethicon, Inc. | Antimicrobial polymer compositions and the use thereof |
| US9149558B2 (en) * | 2005-05-19 | 2015-10-06 | Ethicon, Inc. | Antimicrobial polymer compositions and the use thereof |
| WO2017034871A1 (en) | 2015-08-21 | 2017-03-02 | G&P Holding, Inc. | Silver and copper itaconates and poly itaconates |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB748283A (en) * | 1952-06-21 | 1956-04-25 | Ions Exchange And Chemical Cor | Improvements in or relating to organic metal compounds and processes for making such compounds |
| JPS59222405A (en) * | 1983-05-31 | 1984-12-14 | Hirobumi Arino | Antimicrobial agent using silver complex |
| NZ211976A (en) * | 1984-05-04 | 1989-04-26 | Tripolymer Int Pty Ltd | Algicidal and fungicidal swimming pool additive containing copper sulphate |
| CH673225A5 (en) * | 1986-04-22 | 1990-02-28 | Sanosil Ag | |
| US5149354A (en) * | 1991-01-10 | 1992-09-22 | Delaney Brendan J | Composition for treating swimming pools |
| US5366636A (en) * | 1994-03-18 | 1994-11-22 | Kansas State University Research Foundation | Method of treating water with resin bound ionic silver |
-
1994
- 1994-07-01 GB GB9413299A patent/GB9413299D0/en active Pending
-
1995
- 1995-06-28 ZA ZA955353A patent/ZA955353B/en unknown
- 1995-06-29 CA CA002191580A patent/CA2191580A1/en not_active Abandoned
- 1995-06-29 WO PCT/GB1995/001540 patent/WO1996001231A1/en not_active Application Discontinuation
- 1995-06-29 TR TR95/00775A patent/TR199500775A2/en unknown
- 1995-06-29 BR BR9508174A patent/BR9508174A/en not_active Application Discontinuation
- 1995-06-29 EP EP95923461A patent/EP0768987A1/en not_active Withdrawn
- 1995-06-29 AU AU28015/95A patent/AU2801595A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| ZA955353B (en) | 1996-12-30 |
| WO1996001231A1 (en) | 1996-01-18 |
| AU2801595A (en) | 1996-01-25 |
| GB9413299D0 (en) | 1994-08-24 |
| BR9508174A (en) | 1997-11-11 |
| TR199500775A2 (en) | 1996-06-21 |
| EP0768987A1 (en) | 1997-04-23 |
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