Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/02—Alkylation
• • 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
• • 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
  • A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/30—Introducing nitrogen atoms or nitrogen-containing groups

Definitions

• the present invention relates to the use of highly crosslinked, porous N-halamine biocidal polymers for inactivating pathogenic microorganisms and viruses in water and air filtration applications, thereby rendering the water and/or air safe for human consumption.
• the invention also relates to the use of these polymers for inactivating microorganisms such as bacteria, fungi, and yeasts that can cause noxious odors and infections in commercial products, such as disposable diapers, infant swimwear, incontinence pads, bandages, sanitary napkins, pantiliners, sponges, mattress covers, shoe inserts, animal litter, carpets, fabrics, and air filters, thereby rendering the products free of noxious odors and pathogenic organisms under normal use conditions.
• biocidal polymers e.g., quaternary ammonium salts, phosphonium materials, halogenated sulfonamides, and biguanides (see Trends Polym. Sci. 4:364 (1996))
• N-halamines a relatively new class of compounds known as N-halamines has been shown to have far superior properties including biocidal efficacy, long-term stability, and rechargeability once the efficacy has been lost.
• biocidal N-halamine polymer is poly- 1,3- dichloro-5-methyl-5-(4'-vinylphenyl)hydantoin, which is an inexpensive derivative of polystyrene, and which was first described in U.S. Patent No. 5,490,983, incorporated herein by reference in its entirety. Subsequent disclosures of its biocidal properties for use in disinfecting applications for water filters have recently occurred [see Ind. Eng. Chem. Res. 55:168 (1994); Water Res. Bull. 32:193 (1996); Ind. Eng. Chem. Res. 34:4106 (1995); J. Virolog. Meth. 66:263 (1997); Trends in Polym. Sci.
• the polymer is effective against a broad spectrum of pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Klebsiella terrigena, Legionella pneumophila, and rotavirus, among others.
• the polymer causes large log reductions in contact times on the order of a few seconds in water disinfectant applications.
• the polymer is effective at pH values at least in the range of about 4.5 to about 9.0 and at temperatures at least in the range of about 4°C to about 37°C, and is capable of action even in water containing heavy chlorine demand caused by bioburden.
• the biocidal hydantoin polymer is insoluble in water and organic compounds and will thus not migrate in liquid media.
• the polymer is stable for long periods of time in dry storage (a shelf life of at least one year at ambient temperature).
• the polymer can be produced on an industrial scale. Furthermore, all evidence obtained to date suggests that the polymer is non-toxic and non-sensitizing to humans and animals upon contact.
• a variety of microorganisms such as certain bacteria, fungi, and yeasts are capable of aiding the decomposition of bodily fluids, such as urine and blood, or in the formation of biofilms, that produce undesirable odors in otherwise useful commercial products.
• Bacteria such as Bacterium ammoniagenes and Proteus mirabilis are known to accentuate the decomposition of urea to form noxious ammoma gas through a urease enzyme catalysis mechanism (see for example U.S. Patent No. 5,992,351).
• the polymer poly-l,3-dichloro-5-methyl-5-(4'-vinylphenyl)hydantoin has been shown to be effective at inactivating Proteus mirabilis and thus minimizing the undesirable odor created by ammonia gas (U.S. Patent Application No. 09/685,963, incorporated herein by reference in its entirety). Also, the polymer is insoluble in bodily fluids so as not to migrate to skin surfaces, thus rendering it useful for disposable diapers, incontinence pads, bandages, sanitary napkins, and pantiliners.
• the present invention relates to a polymer having repeating styrene units that have pendant halogenated and nonhalogenated N-halamine groups linked to the benzene ring of the styrene through a methylene group.
• the non-halogenated forms are referred to as N-halamine precursors.
• the present invention relates to methylated polystyrene compounds having pendant N-halamine precursors and to the biocidal methylated polystyrene compounds having N-halamine groups and to the methods for their preparation.
• An N-halamine group is a heterocyclic, monocyclic 4 to 7 membered ring, wherein at least 3 members of the ring are carbon, from 1 to 3 members of the ring are nitrogen heteroatom, from 0 to 1 member of the ring is oxygen heteroatom, and wherein 0 to 2 carbon members are carbonyl. At least one ring nitrogen has a chlorine or bromine atom bonded to it.
• a precursor N-halamine group is the heterocyclic group without any chlorine or bromine atoms on any ring nitrogens.
• a precursor N-halamine group has a hydrogen, or a hydroxy alkyl group bonded to all ring nitrogens that are not bonded to a linking group.
• the linking group is a methylene group.
• N-halamine and N-halamine precursor groups bonds the N-halamine or N-halamine precursor group to the benzene ring of polystyrene.
• Representative of N-halamine and N-halamine precursor groups are the halogenated and nonhalogenated hydantoins, imidazolidinones, oxazolidinones, and isocyanurates.
• the polymeric compounds of the invention are preferably derived from methylated polystyrene particles.
• the particles can be used in absorbent articles that have an absorbent core with absorbent material.
• Methylated polystyrene refers to a polystyrene having a methylene group bonded to the benzene ring of the polystyrene. The methylene group is a linkage to the N-halamine or N-halamine precursor group.
• a representative methylated polystyrene is poly(p-methyl)styrene.
• a representative functionalized methylated polystyrene is poly(p-chloromethyl)styrene.
• chloromethylated polystyrene crosshnked with divinylbenzene is used as a starting material for making the compounds of the invention.
• other crosslinking agents may be utilized.
• Anticipated uses for the biocidal compounds of this invention are for the disinfection of a variety of bacteria-carrying media, including, but not limited to, water, oil, and air.
• the compounds of the invention can be combined with absorbent materials and incorporated into absorbent products for the disinfection and the prevention of noxious odors caused by the decomposition of organic materials contained in bodily fluids.
• a further embodiment of the invention relates to the synthesis of methylated polystyrene having N-halamine precursor groups, and their biocidal derivatives.
• N- halamine precursors are made biocidal when at least one ring nitrogen is bonded to a halogen.
• the halogen is either a chlorine or bromine atom.
• porous beads of highly crosshnked functionalized methylated polystyrene reactive toward N-halamine precursors is used as the starting material.
• the methylated polystyrene is functionalized by placing a halogen, such as a chlorine atom, on the methyl group, making the polystyrene reactive toward a N-halamine or a N-halamine precursor group.
• the invention provides a polystyrene having a N-halamine precursor group bonded to at least some of the benzene rings of the polystyrene by a methylene group.
• the invention provides a polystyrene having a biocidal N- halamine group bonded to at least some of the benzene rings of the polystyrene by a methylene group.
• the invention provides a method for making a methylated polystyrene having pendant N-halamine precursor groups.
• the method includes reacting a functionalized methylated polystyrene with an N-halamine precursor and an alkali metal base to produce a methylated polystyrene having pendant N-halamine precursor groups.
• the appropriated functionalized methylated polystyrene is reacted with an N-halamine precursor and the base for from about 12 to about 96 hours at a temperature of from about 70° to about 120°C.
• To make the polystyrene biocidal requires halogenating the methylated polystyrene having pendant N-halamine precursor groups to produce the biocidal methylated polystyrene having pendant N-halamine groups.
• An alternate embodiment for making a methylated polystyrene having pendant N-halamine precursor groups includes reacting an N-halamine precursor with an alkali metal base to produce an alkali metal salt of the N-halamine precursor.
• the N-halamine precursor is reacted with the alkali metal base for from about 15 minutes to about 2 hours at a temperature of from about 25° to about 100°C.
• the method includes reacting the alkali metal salt of the N-halamine precursor with a functionalized methylated polystyrene to produce a methylated polystyrene having pendant N-halamine precursor groups.
• the appropriated functionalized methylated polystyrene is reacted with the N-halamine precursor salt for from about 4 to about 96 hours at a temperature of from about 70° to about 120°C.
• Either method of making a methylated polystyrene having pendant N-halamine precursor groups is used to make the biocidal derivative, and involves halogenating the methylated polystyrene having pendant N-halamine precursor groups to produce the biocidal methylated polystyrene having pendant N-halamine groups.
• One embodiment of the invention relates to the use of the biocidal polymeric compounds in filters for the disinfection of water and air.
• One embodiment of the invention relates to the disinfection and control of odor in bodily fluids in applications such as disposable diapers, infant swimwear, incontinence pads, bandages, sanitary napkins, pantiliners, and the like.
• Biocidal compounds made according to the present invention using chloromethylated polystyrene beads as a starting material require fewer steps to synthesize and produce less chlorine outgassing than the previously produced N-halamine polymer of U.S. Patent No. 5,490,983 to Worley et al., while maintaining a reasonable biocidal efficacy.
• Chloromethylated polystyrene beads have been utilized in the past to prepare ion-exchange resins and weakly biocidal polyquatemary ammonium salts (U.S. Patent No. 4,349,646 and U.S. Patent No. 4,826,924), but have not been functionalized with potent biocidal N-halamine moieties.
• One embodiment of the invention provides a polymer having a repeating unit, wherein the repeating unit has the structure:
• the moieties R of the repeating unit are selected from among the following:
• Ri, R2, R3, and R are independently selected from C1-C 4 alkyl, phenyl, or aryl;
• X is hydrogen, chlorine, or bromine, at least one of which must be chlorine or bromine when the compound is a biocidal N-halamine, X is not chlorine or bromine for N-halamine precursors.
• "Independently selected” encompasses all the combinations of the one or more R n groups possible with the moieties selected from C1-C 4 alkyl, phenyl and aryl.
• the R n groups can all be the same group or can all different groups or any other combination.
• the repeating unit appears consecutively if the polymeric compound is a homopolymer, or alternatively with one or more different repeating units if the polymeric compound is a copolymer.
• methylated polystyrene having pendant N-halamine precursor groups and biocidal methylated polystyrene having pendent N-halamine groups are provided, wherein the N-halamine and N-halamine precursor groups are either a halogenated or nonhalogenated hydantoin, imidazolidinone, oxazolidinone, or isocyanurate.
• the invention provides a methylated polystyrene having pendant N-halamine precursor groups.
• the methylated polystyrene is derived from highly crosshnked chloromethylated polystyrene.
• the methylated polystyrene having pendant N-halamine groups is biocidal by virtue of the halogen bonded to a nitrogen of the heterocyclic moiety.
• the methylated polystyrenes of the invention are highly crosshnked and therefore are insoluble polymer beads.
• the methylated polystyrene having pendant N-halamine groups is a biocidal polymer bead.
• the biocidal polymer beads can be employed in a filter for water, cutting oils, or air disinfection.
• the biocidal polymer beads can be mixed with an absorbent material.
• Suitable absorbent materials include the materials in disposable diapers, including natural and synthetic fibers. Among the natural fibers are cellulose fibers, most commonly derived from wood pulp. Synthetic fibers include polyolefins, among others. Polyolefins include polypropylene and polyethylene. Superabsorbent polymers may be combined with the biocidal polymers of the present invention.
• the biocidal polymer of the invention can make up from about 0.1 to about 5.0 weight percent, more preferably a weight percent of about 1.0 for applications involving bodily fluids, including disposable diapers, infant swimwear, incontinence pads, bandages, sanitary napkins, pantiliners, mattress covers, shoe inserts, sponges, and animal litter.
• the weight percent is based on the combined weight of the polymer and any absorbent core components, such as wood pulp, any synthetic or natural fibers, cellulose fibers, polyolefin fibers, superabsorbent polymers, and the like.
• a weight percent of from about 0.1 to about 2.0, more preferably a weight percent from about 0.5 to about 1.0 is considered suitable. The weight percent is based on the combined weight of polymer and any filler materials.
• the biocidal polymer beads of the invention will inactivate pathogenic microorganisms and viruses contained in water or air media that comes in contact with the beads. In some applications, it is desirable to allow the media to flow through and contact the beads.
• the biocidal beads prevent or minimize noxious odors. It is believed the biocidal beads inactivate the microorganisms that enhance the decomposition of organic matter in bodily fluids to ammonia or other noxious materials. When biocidal, the beads will prevent or minimize noxious odors in air filters by inactivation of microorganisms including those that cause mildew and molds, as well as those from any liquid or aerosol which might contact the surface of the beads.
• the mechanism of action of the biocidal polymer is believed to be a result of surface contact of the microorganism with chlorine or bromine atoms covalently bound to the N-halamine groups of the polymer.
• the chlorine or bromine atoms are transferred to the cells of the microorganisms where they cause inactivation through a mechanism not completely understood, but probably involving oxidation of essential groups contained within the enzymes comprising the organisms.
• a wide variety of cartridge filtration devices can be used that incorporate the biocidal polymer beads, including very large units in small water treatment plants and in the air-handling systems of large aircraft, hotels, and convention centers, and small filters as might be employed in household carafes and for faucets and portable devices for backpacking and military field use.
• a broad variety of absorbent and filler materials can be used in combination with the biocidal polymer to aid in preventing noxious odors.
• Absorbent materials are able to hold fluids, aerosol particles, and solid contaminants for sufficient periods of time such that the biocidal polymer beads can make contact with the odor-causing microorganisms.
• Absorbent materials include, but are not limited to, swellable clays, zeolites, alumina, silica, cellulose, wood pulp, superabsorbent polymers and fibers, including polyolefin fibers, such as polypropylene fibers and polyethylene fibers.
• the absorbent material can contain further adjuvants such as deodorants, fragrances, pigments, dyes, and mixtures of these for cosmetic purposes.
• the biocidal polymer beads can be used within the absorbent cores of diapers, incontinence products, infant swimwear, pantiliners, sanitary napkins, and the like.
• a marked advantage of the biocidal polymer beads of this invention over prior odor-controlling technology is that the beads of the invention are much more effective biocides against pathogenic microorganisms, such as S. aureus and P. aeruginosa, than are the commercial biocides, such as the quaternary ammonium salts.
• the biocidal polymer beads can serve a dual function: inactivation of odor-causing microorganisms and inactivation of disease-causing pathogens. For this reason, the biocidal polymer beads will have widespread use in medical settings.
• the present invention provides methods for making methylated polystyrene having pendant N-halamine precursor groups and methylated polystyrene having pendent N-halamine groups.
• a methylated polystyrene is obtained that has been functionalized to react toward an N-halamine precursor or an N- halamine group.
• the methylated polystyrene is functionalized by bonding a chlorine atom to the methylene group.
• One representative functionalized methylated polystyrene is poly(p-chloromethyl)styrene. Crosshnked poly(chloromethyl)styrene is available from commercial vendors ranging up in size from very small microparticle sizes.
• the particles size of the biocidal polymer bead is preferably in the range of from about 100 to about 1500 ⁇ m, more preferably in the range of from about 200 to about 800 ⁇ m. Particle sizes within these ranges provide adequate flow characteristics for microbiologically contaminated fluids and lessen the risk of exposure of the respiratory systems of workers to fine aerosolized particles.
• the biocidal polymer beads should have pore sizes in the range of from about 10 to about 100 nm, more preferably, in the range of from about 30 to about 70 nm.
• the porous structure is advantageous in the synthetic reaction step because the highly crosshnked beads are insoluble in organic solvents and water.
• the degree of crosslinking of the starting chloromethylated polystyrene should be in the range of from about 3 to about 10 weight percent to ensure hardness and lack of solubility. In one embodiment, the degree of crosslinking is from about 5 to about 8 weight percent.
• Representative methods of making a methylated polystyrene having pendant N-halamine precursors are as follows.
• clean, highly crosshnked porous chloromethylated polystyrene beads are suspended in a medium, such as DMF.
• the chloromethylated polystyrene beads are reacted with an N-halamine precursor, such as 5,5-dimethylhydantoin, in the presence of an alkali metal carbonate, such as potassium carbonate, at a temperature from about 70° to about 120°C, preferably about 95 °C, for about 12 to about 96 hours to yield the methylated polystyrene having pendant N-halamine precursor groups.
• the time for this reaction is typically 72 hours when an alkali metal carbonate is employed.
• the alkali metal salt of the N-halamine precursor is prepared first by reacting an N-halamine precursor with an alkali metal base for from about 15 minutes to about two hours at a temperature of from about 25° to about 100°C.
• the alkali metal base is preferably a carbonate, a hydroxide, or a hydride, and includes an alkali metal chosen from sodium or potassium. The reaction time between the N-halamine precursor and chloromethylated polystyrene is reduced if the alkali metal salt of the N-halamine precursor is prepared first.
• the salt is then used in the subsequent reaction between the alkali metal salt of the N-halamine precursor with the chloromethylated polystyrene to yield the methylated polystyrene having pendant N-halamine precursor groups.
• the time and temperature for this subsequent reaction is from about 4 to about 96 hours at a temperature of from about 70° to about 120°C, but typically is about 12 hours or less.
• the overall preparation time can be reduced by employing the latter two-step reaction method.
• the isolated product beads made through either method are washed in boiling water for purification purposes.
• an aqueous suspension of the bead is chlorinated or brominated to render the bead biocidal.
• Halogenation is accomplished by exposing the bead to a source of free chlorine (e.g., gaseous chlorine, sodium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate) or free bromine (e.g., liquid bromine, sodium bromide/potassium peroxymonosulfate) in aqueous base.
• a source of free chlorine e.g., gaseous chlorine, sodium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate
• free bromine e.g., liquid bromine, sodium bromide/potassium peroxymonosulfate
• the reactor is preferably chilled to about 10°C to prevent undesirable side reactions.
• Ambient temperature can be employed for the other noted sources of free halogen, and the reactions can be carried out in a reactor or in situ in a cartridge filter packed with the unhalogenated precursor. Using these methods, typical loadings of about 6-7% by weight chlorine and about 8-9% by weight bromine on the beads are generally obtained.
• the present invention is more particularly described in the following examples which are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art.
• EXAMPLE 2 An Alternative Representative Preparation of Chlorinated Methylated Polystyrene Hydantoin Beads
• the potassium salt of 5,5-dimethylhydantoin was prepared by reacting 25.6 grams (0.2 mole) of 5,5-dimethylhydantoin with 11.2 grams (0.2 mole) of potassium hydroxide in 100 mL of boiling ethanol with stirring. The ethanol and product water were removed under vacuum to obtain the white salt. The salt was added to 200 mL of anhydrous DMF and heated to 95°C until all of the salt dissolved. Then 8.12 grams (about 0.048 mole of active chlorine) cleaned chloromethylated polystyrene beads were added and the mixture was heated with stirring at about 100°C for 12 hours.
• Example 1 The unreacted potassium salt of the hydantoin and the DMF were recycled for further use, and the beads functionalized with hydantoin groups were washed and dried under vacuum at 85°C until constant weight as in Example 1.
• the weight of the beads prepared in this manner was 11.0 grams (35.5% by weight add-on). Chlorination of the beads as in Example 1 produced a chlorine loading of 6.3% by weight. This alternate method of preparing the chlorinated beads would appear to be superior to that in Example 1 as the reaction time for functionalization with the hydantoin moiety is reduced considerably (from 72 to 12 hours).
• Example 1 were suspended in a solution containing 40 mL of 10% sodium hypobromite and 40 mL of water. The pH was adjusted to 7.0 using 2 N acetic acid. The mixture was stirred for 1 hour at 25°C. The brominated beads were removed by filtration, washed with three 100 mL portions of water, and dried under vacuum until constant weight was obtained. The bromine content determined by sodium thiosulfate/iodometric titration was 8.2% by weight. An infrared spectrum of a small sample of the beads (crushed to a powder) in a KBr pellet exhibited prominent bands at 1714 and 1776 cm -1 consistent with the presence of a monobrominated hydantoin functional group.
• Polystyrene Hydroxymethylhydantoin Beads Porous beads of 5.6% crosshnked chloromethylated polystyrene (containing 20.85%) by weight chlorine) obtained from Suqing Group (Jiangyin, Jiangsu, PRC) having particle sizes in the range 180 to 425 ⁇ m, but undetermined pore sizes, were cleaned as described in Example 1. Following drying to constant weight under vacuum at 50°C, 10.57 g (about 0.062 mole of active chlorine) of the beads were suspended in 150 mL of anhydrous DMF in a 250 mL flask fitted with a condenser.
• TMIO 2,2,5,5- tetramethylimidazolidin-4-one
• the mixture was stirred at 95°C for 48 hours, cooled, filtered, and the beads functionalized with imidazolidinone groups were washed with two 100 mL portions of water and then held in boiling water for 15 minutes. After filtration, the beads were again washed with two 100 mL portions of water and then dried under vacuum at 75°C until constant weight (6.65 g) was obtained. The percent by weight add-on was 10.8%. This add-on percentage was lower than for the other beads described in previous examples.
• Example 1 (5.0 g) were dried under vacuum at about 50°C until constant weight was obtained. These beads were stored in a capped brown bottle. Periodically over 90 days samples were removed for analytical determination of chlorine content using a sodium thiosulfate/iodometric titration procedure. The data are shown in Table 1.
• the beads as prepared in Examples 1-4 were tested for biocidal activity against two pathogens contained in water. In the tests, about 3.3-3.4 g of biocidal halogenated beads were packed into glass columns having inside diameter 1.3 cm to a length of about 7.6 cm; the empty bed volumes of the beads ranged from 2.9 to 4.4 mL. Identical sample columns of unhalogenated beads were prepared to be used as controls.
• Odor Control Beads prepared as described in Example 1 containing chlorine loadings of about 6.2% by weight were evaluated as to their efficacies in controlling ammonia generation through inactivation of Proteus mirabilis.
• Blends of 5-10 mg of chlorinated beads and 1.0 g of wood pulp (0.5 or 1.0% by weight beads) were prepared by mixing with 200 mL of distilled water in a blender (Hamilton Beach 7 Blend Master Model 57100, whip setting). Following vacuum filtration, which produced wood-pulp pads, and drying in air at 25°C, the samples were placed in Petri dishes. An inoculum known to provide a high level of odor was formulated.
• the formulation included 9 mL of a mixture of 25 mL of pooled human female urine and 1.25 g of urea and 1 mL of an aqueous suspension of about 1.3 x 10 8 CFU/mL of Proteus mirabilis.
• Each sample including a control of wood pulp with nonhalogenated polymer, was inoculated with 1 mL of the formulation described above, and the Petri dishes were sealed with parafilm and incubated at 37°C for 24 hours. The samples were then measured for ammonia production using Drager tubes (Fisher Scientific, Pittsburgh, PA, and Lab Safety Supply, Janesville, WI) capable of detection in the range 0.25 to 30 mg/L.
• the control sample registered an ammonia concentration greater than 30 mg/L in a contact time interval of 2 to 4 hours, while the chlorinated samples (0.5 and 1.0% bead/wood pulp mixtures) registered ammonia concentrations of only 1.5 to 2.0 mg/L after 4 hours contact and only about 2.0 mg/L after 24 hours contact. It can be concluded that the porous chlorinated beads are highly effective at preventing ammonia generation and hence noxious odor even at very low blends with an absorbent material like wood pulp.

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