CN102176830A - Synergistic peroxide-based biocide compositions - Google Patents

Abstract

Disclosed herein are methods for controlling microbial growth in aqueous systems containing sulfite and/or bisulfite residuals by adding a peroxide compound at a pH greater than 5. Also disclosed are methods for stabilizing an active halogen biocide in an aqueous system containing peroxide by adding an N-hydrogen compound to the active halogen biocide prior to combining the active halogen biocide with the peroxide-containing aqueous system. Further disclosed herein are optimized papermaking biocide protocols consisting of an initial treatment of sulfite-bleached pulp with peroxide and subsequent application of an N-hydrogen-stabilized active halogen compound to the papermaking white water, as well as analytical methods for determining peroxide concentrations in aqueous systems in the presence of sulfite and/or bisulfite.

Description

Synergistic peroxide-based biocide compositions

technical field

The present invention relates to methods of controlling microbial growth in aqueous systems comprising sulfite and/or bisulfite residues, such as solutions or suspensions obtained after application of sulfite-based reducing bleaches. The present invention further relates to methods of stabilizing active halogen biocides in aqueous systems containing peroxides.

Background technique

Reducing bleaches are frequently used in papermaking. This bleaching process usually uses bisulfite or a solution that generates bisulfite. While enhancing paper brightness, the use of such solutions can also result in sulfite residues remaining in the resulting pulp. Sulfite residues make stock preservation and subsequent control of paper machine deposits more difficult because many paper slimicides and preservatives such as Biological agents become unstable in the presence of sulfites.

Surprisingly, it has been found that at an optimized pH, application of an oxidizing biocide to a system containing residual sulfite not only succeeds, but even provides synergistic microbial control. In particular, it has been found that hydrogen peroxide can be used to effectively, even synergistically, treat sulfite-bleached pulp after pH optimization to enhance bleaching and microbial control.

The rapid neutralization of hydrogen peroxide in acidic media (pH<5) by sulfite is well known and is the basis of the standard analytical method of hydrogen peroxide titration. It has been found that at elevated pH these generally incompatible materials can coexist for a period of time sufficient to allow bleaching and microbial control applications.

Contents of the invention

According to the present invention, microbial growth in aqueous systems containing sulfite and/or bisulfite residues can be controlled by adjusting and maintaining the aqueous system at pH > 5, preferably pH 6-11, more preferably 7.5 -10, and add peroxygen compound. The pH ranges and any numerical ranges defined by upper and lower limits in the present invention should be understood to also include all subranges formed by combinations of any upper limit and any lower limit.

Preferred peroxygen compounds include hydrogen peroxide, inorganic peroxygen compounds such as alkali metal or alkaline earth metal perborates, percarbonates or persulfates, organic peroxyacids such as peracetic acid or perbenzoic acid, other organic peroxygen compounds Oxygen compounds such as carbamide peroxide, and mixtures of the foregoing. The term "persulfate" includes both monopersulfates (eg, salts of permonosulfuric acid (H ₂ SO ₅ )) and peroxodisulfates (ie, salts of peroxydisulfuric acid (H ₂ S ₂ O ₈ )).

The effectiveness of peroxygen compounds can be increased by the addition of bleach activators such as tetraacetylethylenediamine (TAED).

A particularly preferred peroxygen compound is hydrogen peroxide.

If necessary, the pH of the aqueous system can be controlled by adding alkali or basic salts such as alkali metal or alkaline earth metal hydroxides, carbonates, bicarbonates, borates, metasilicates or mixtures thereof and/or buffer.

In a preferred embodiment, the sulfite and/or bisulfite and the freshly added peroxygen compound are present in concentrations of 1-300 ppm each, more preferably 5-200 ppm each, most preferably 10-100 ppm each.

Applications that may benefit from sulfite/peroxide compatibilization according to the present invention include pulp and papermaking, recycled pulp and papermaking, pulp or biomass bleaching, fabric bleaching, and similar applications.

Since treatment of an aqueous system (such as a stock slurry) with a peroxygen compound (such as hydrogen peroxide) will form a range of peroxide concentrations or residues in the aqueous system, any subsequent application of biocides is critical for peroxidation It is very important that the residues of peroxides or peroxides remain stable. It has been found that solutions containing hydrogen peroxide, such as dilute papermaking stocks, can be successfully treated with stabilized active halogens. This additional result was unexpected since it is well known that active halogen species are neutralized in the presence of peroxide (since hydrogen peroxide acts as both an oxidizing and reducing agent).

It has also been specifically found that active halogen species having nitrogen-bound halogens are surprisingly stable in the presence of peroxides. According to the present invention, active halogen biocides in aqueous systems containing peroxides or peroxide residues can be obtained by adding N -Hydrogen compounds for stabilization. N-hydrogen compounds here and below are organic or inorganic compounds having at least one hydrogen atom bonded directly to a nitrogen atom.

The novel method is best suited for applications where both peroxides and active halogens are used.

Active halogen biocides are biocides comprising a halogen in oxidation state 0 or +1, especially chlorine or bromine, eg elemental chlorine or bromine and hypochlorite or hypobromite.

In a preferred embodiment, the concentration of active halogen (calculated as Cl ₂ ) stabilized by N-hydrogen compounds is 0.1-20 ppm. Here and below the expression "in terms of _Cl2 " denotes the concentration of elemental chlorine that is stoichiometrically equivalent to the concentration of active halogen in a given system.

Preferred N-hydrogen compounds are selected from ammonia, ammonium salts, such as ammonium sulfate and ammonium bromide, other nitrogen compounds without carbon-hydrogen bonds, such as urea, biuret, isocyanuric acid and sulfamic acid, organic N- Hydrogen compounds such as p-toluenesulfonamide, 5,5-dialkyl-hydantoin, methanesulfonamide, barbituric acid, 5-methyluracil, imidazoline, pyrrolidone, morpholine, acetanilide, Acetamide, N-ethylacetamide, phthalimide, benzamide, succinimide, N-methylolurea, N-methylurea, acetylurea, methyl allophanate, amino Methyl formate, phthalohydrazide, pyrrole, indole, formamide, N-methylformamide, dicyandiamide, ethyl carbamate, 1,3-dimethylbiuret, methylphenylbiuret , 4,4-Dimethyl-2-oxazolidinone, 6-methyluracil, 2-imidazolinone, ethylene urea, 2-pyrimidinone, azetidin-2-one, 2-pyrrolidone , caprolactam, benzenesulfinimide, benzenesulfinimide-based amides, diaryl- or dialkylsulfinimide, isothiazoline-1,1-dioxide, hydantoin Urea, glycine, piperidine, piperazine, ethanolamine, glycinamide, creatine, and glycoluril.

More preferred N-hydrogen compounds are 5,5-dimethylhydantoin, urea, ammonia or ammonium salts.

The peroxide or peroxide residue in the aqueous system is preferably hydrogen peroxide, alkali metal or alkaline earth metal percarbonate, perborate or persulfate, organic peroxyacid, or both or both of the foregoing. A mixture of more than one, most preferably hydrogen peroxide.

Preferred applications of either discovery (i.e., the synergistic performance of peroxide-treated sulfite pulp and the stability of active halogens against degradation by peroxide or peroxide residues) are in pulp and paper processing, recycling Pulp and paper, deinking, stock bleaching, biomass bleaching, fabric bleaching or slime bleaching. Preferred aqueous systems are stock and papermaking slurries and liquors, recycled stock slurries, stock slabs, deinking liquor slurries, stock or biomass bleaching slurries and liquors, fabric bleaching liquors and slimes.

Other preferred applications are in water treatment such as wastewater, papermaking liquors and water, pond and spa water, industrial cooling water, water exposed to reverse osmosis filters or ion exchange resins, and in applications including fractionation tanks and downhole applications or hard surface disinfection Aqueous systems in oilfield applications.

Other preferred applications are in aqueous systems found in food and crop protection applications including fruit and vegetable washing, meat and poultry processing, beverage processing, fish farming and aquaculture.

Combining these two findings (i.e., the synergistic performance of peroxide-treated sulfite pulp and the stability of active halogens against degradation by hydrogen peroxide or peroxide residues) results in a cost-effective Definition of Microbial Control Program. The scheme involves pulp bleaching with sulfites followed by peroxide treatment and conversion of the pulp into paper in the presence of an active halogen biocide with nitrogen-bound halogens.

In a preferred embodiment, the peroxide-comprising aqueous system is obtainable by adding a composition comprising at least one peroxygen compound to said aqueous system at a pH greater than 5.

In the preferred combined process application, the aqueous system is selected from pulp and papermaking slurries, recycled stock slurries, stock slabs, deinking liquor slurries, stock or biomass bleaching slurries and liquors, fabric bleaching solutions and sticky mud.

According to the invention, the combination of sulfite and peroxy compound (optionally in combination with an activator such as tetraacetylethylenediamine), combined application of peroxy compound and active halogen or combined application of sulfite and peroxy compound and subsequent Combined application or generation of peroxygen compounds and active halogens to optimize cost performance. Such combined application is currently prohibited by the rapid mutual neutralization of these substances. The present invention demonstrates methods for using these types of compounds in combination and even synergistically.

Another object of the present invention is an analytical method for determining the concentration of peroxides in aqueous systems containing sulfites and/or bisulfites. The method comprises the steps of:

(i) adding a defined amount of excess N-hydrogen stabilized active chlorine compound to immediately destroy the sulfite and/or bisulfite while leaving an amount of unreacted N-hydrogen stabilized active chlorine compound,

(ii) measuring the amount of unreacted N-hydrogen stabilized active chlorine compound to determine the sulfite and/or bisulfite concentration, and

(iii) Determine the peroxide concentration.

The amount of unreacted N-hydrogen stabilized active chlorine compound in step (ii) can be measured by any method known in the art, in particular by the known DPD method according to ISO 7393-2. The sulfite and/or bisulfite concentration corresponds to the amount of N-hydrogen stabilized active chlorine compound added in step (i) to the unreacted N-hydrogen stabilized active chlorine measured in step (ii) The difference in the amount of the compound.

The peroxide concentration in step (iii) can be determined by one of the methods known in the art, for example by titration with potassium iodide using thiosulfate as indicator.

A preferred N-hydrogen stabilized active chlorine compound for use in the above analytical method is 1-chloro-5,5-dimethylhydantoin (MCDMH).

The following non-limiting examples are intended to illustrate the invention in more detail.

Example

The expression "1 g cfu/mL" means the common (decimal) logarithm of the number of colony-forming units per milliliter, in the sense that the term "reduction" when combined means the number of colony-forming units per milliliter before treatment and the number of colony-forming units per milliliter after treatment Ordinary logarithm of the ratio of quantities. All percentage or ppm concentrations are by weight unless otherwise indicated.

Example 1

The aqueous solution containing sodium sulfite and hydrogen peroxide was mixed at 21° C. to obtain a solution with a sulfite content (calculated as SO ₃ ²⁻ ) of 40 ppm, a hydrogen peroxide content of 20.0 ppm and a pH of 6.7. The temperature of the solution was maintained at 21°C and the residual sulfite and peroxide levels were determined 15, 30 and 60 minutes after mixing. This step involves adding to the sample a known amount of 1-chloro-5,5-dimethylhydantoin (MCDMH) in excess relative to the estimated residual sulfite content. The remaining MCDMH concentration was then measured by the standard DPD total halogen method. Since sulfite rapidly neutralizes MCDMH at all pHs, the concentration of sulfite was the added concentration of MCDMH minus the measured concentration of MCDMH, see Equation 1 below. This step is effective in the presence of _H2O2 , since _H2O2 does not react with _MCMDH , and does not interfere with the total active halogen method, since _the method is performed at approximately neutral pH.

(1) [Sulphite] = [MCDMH _added ] - [MCDMH _measured ]

The _{H2O2 concentration} can be determined by recording the _{H2O2 concentration} measured by acid thiosulfate titration with a KI indicator (HACH HYP-1 Hydrogen Peroxide Test Kit - Hach Co., Loveland, CO). Since the titration is performed _at acidic pH, this method achieves a _H2O2 concentration in excess relative to the sulfite concentration in the sample. Since the sulfite concentration can be obtained from MCMDH analysis and Equation 1, _{the H2O2} concentration can be calculated by Equation 2 below:

(2) [H ₂ O ₂ ]=[H ₂ O _{2 Measured} ]+[Sulphite _Calculation ]

The estimated error of this method is ±1ppm.

The results are shown in Table 1, which shows the apparent residual concentrations of both substances observed even after 30 minutes.

Table 1

Example 2

The procedure of Example 1 was repeated except that the pH of the mixed solution was 9.0, and the residue concentration was measured at 5, 15, 30, 60, 120 and 1080 minutes after mixing. The results are shown in Table 2, which demonstrates that the co-stability of hydrogen peroxide and sulfite was further enhanced at pH 9.0, where a significant increase in both peroxide and sulfite was observed even after 2 hours. residual concentration.

Table 2

Example 3

The synergistic biocidal performance of the combined application of sulfite and hydrogen peroxide at elevated pH was investigated. Sulfite and peroxide at concentrations indicated in Table 3 below were added to an aqueous solution consisting of (a) deionized water, (b) NaHCO ₃ , resulting in a carbonate buffer concentration of 200 ppm (as CaCO ₃ total alkalinity meter), (c) sulfite bleached pulp slurry at a final concentration of 0.05%, carrying a minimum concentration associated with residual sulfite of 6 ppm, and (d) NaOH, to achieve a pH of 9.0.

Microbial populations can be provided by preparing slurry slurries 24-48 hours prior to testing and storing at room temperature to allow microbial growth to high test levels. For the untreated control population, 1 g cfu/mL = 5.9 for the 3-hour exposure test and 1 g cfu/mL = 6.5 for the 24-hour exposure test. Populations reported are total aerobic counts by soy tryptone agar plating. The test results are shown in Table 3.

table 3

It appeared that the mere presence of sulfite had no appreciable effect on the bacterial population at sulfite concentrations of 32-128 ppm. In contrast, hydrogen peroxide showed a less developed level of sterilizing efficacy, resulting in a 1.2-3.5 reduction in 1 g cfu/mL in 3 hours and a reduction of 5.5 in 24 hours. Surprisingly, at 3 hours of exposure, the partially mixed sulfite/hydrogen peroxide system (Test Nos. 7 and 9) provided greater efficacy than hydrogen peroxide alone (Test No. 5).

The observed performance levels show a clear synergy between sulfite and peroxide at elevated peroxide concentrations. Since sulfite alone has no bactericidal efficacy, the observed increase in the potency of hydrogen peroxide in the presence of sulfite is the result of a synergistic effect. This result can be quantified by the method of Kull et al. (F.C.Kull, P.C.Elisman, H.D.Sylwestrowicz and P.K.Mayer, Appl. Microbiol, 1961, 9, 538), which states that when the observed synergy according to Equation 3 Synergy is present when the index (SI) is less than 1.0.

(3) SI=(level of A)/(effective level of A)+(level of B)/(effective level of B)

Setting A as the concentration of sulfite and B as the concentration of peroxide, the following results can be obtained: Since sulfite is basically incapable of sterilization, the denominator of the first term becomes infinite, making the value of the first term zero. If we set the effective level at a level that produces a reduction of 1 g cfu/mL in 3 hours to 3.5, the denominator of the second term becomes 160 ppm (according to test number 5 of Table 3). The Synergy Index for Test Nos. 7 and 9 at 3 hours of exposure is then less than 1.0 according to Equation 4 below, since these tests generate greater reduce.

(4) SI=0+(<160)/160=(<1.0)

Example 4

The synergy of combined application of sulfite and hydrogen peroxide at higher sulfite and hydrogen peroxide concentrations was examined. The conditions are the same as in Example 3. The microbial population of the untreated control was 1 g cfu/mL = 6.26 at 3 hours of exposure and 1 g cfu/mL = 6.18 at 24 hours of exposure. The results are shown in Table 4.

Table 4

As shown in Table 4, the application of sulfite at a concentration of 128-512 ppm had no significant effect on the microbial population. In contrast, hydrogen peroxide at concentrations of 120-160 ppm showed a less developed level of sterilizing efficacy, resulting in a 3.3-4.0 reduction in 1 g cfu/mL in 3 hours and a reduction of 3.7-5.5 in 24 hours. It is also surprising that some mixed sulfite/hydrogen peroxide systems provide higher potency than hydrogen peroxide alone. The observed performance levels show a clear synergy between sulfite and peroxide at elevated peroxide concentrations. Since sulfites themselves do not exhibit bactericidal efficacy, the observed increase in the potency of hydrogen peroxide in the presence of sulfites is the result of a synergistic effect. Test No. 9 may prove synergy completely rigorously. If the desired effect is set at 1 g cfu/mL reduction of 4.2, we can see that >512 ppm of sulfite is required to achieve this effect. The amount of hydrogen peroxide alone to achieve this effect is 150 ppm or higher. This forms Equation 5:

(5) SI=32/(>512)+(<120)/150=(<0.063)+(<0.8)=(<0.86)

Example 5

The sterilizing efficacy of solutions comprising sulfite and hydrogen peroxide was further investigated in the absence of slurry. The efficacy of inhibition of Pseudomonas aeruginosa growing in the nutrient in the presence of 83 and 830 ppm sulfite was measured. The sulfite-containing Pseudomonas aeruginosa culture was then diluted 1:99 with Butterfield buffer, pH 7.0. The sulfite concentrations in Table 5 below are those of the final dilution. The dilutions were then contacted with 50 ppm hydrogen peroxide for 3 hours at 37°C. The untreated control population (Test 1) was 1 g cfu/mL = 6.0. The test results are shown in Table 5.

table 5

As shown in Table 5, hydrogen peroxide was surprisingly more effective (1.5 reduction in 1 g cfu/mL) against Pseudomonas aeruginosa grown at 830 ppm sulfite and diluted to 8.3 ppm upon application than against P. The bactericidal efficacy observed for Pseudomonas aeruginosa grown in the presence of sulfite (0.9 reduction at 1 g cfu/mL). Thus, the surprising enhancement of hydrogen peroxide sterilization efficacy by the addition of sulfite was further validated in the absence of slurry.

Example 6

The stability of nitrogen-bound active halogen species in the presence of residual H ₂ O ₂ was investigated. Free and total chlorine concentrations _were measured by standard DPD methods, and total _H2O2 concentrations were measured by acid sulfite titration. The MCDMH concentration is the total active halogen minus the concentration of free active halogen. _{The H2O2} concentration is the total oxide concentration minus the MCDMH concentration. Combining 2.1 ppm (0.062 mM) _H2O2 with 1 ppm (0.014 mM ₎ NaOCl (as _Cl2 ) resulted in an immediate stoichiometric reduction of the two species, resulting in a _H2O2 residue of ~1.6 ppm (0.048 _mM ), with no measurable free chlorine. The above reaction is shown in Equation 6.

(6)NaOCl+H ₂ O ₂ →H ₂ O+NaCl+O ₂

The inherent _instability of active halogens in the presence of _H2O2 is shown in Table 6.

Table 6

¹⁾ - Measured using HACH HYP-1 Hydrogen Peroxide Test Kit (Hach Co., Loveland, CO)

Example 7

The effect of adding an equimolar amount of 5,5-dimethylhydantoin (DMH) to the NaOCl solution prior to combining with hydrogen peroxide was investigated. The results are shown in Table 7. The MCDMH concentration is the total active halogen concentration minus the free active halogen concentration. _{The H2O2} concentration is the total oxide concentration minus the MCDMH concentration.

Table 7

¹⁾ - Measured using HACH HYP-1 Hydrogen Peroxide Test Kit (Hach Co., Loveland, CO)

It can be seen that the addition of DMH can simultaneously stabilize the combined active chlorine and hydrogen peroxide. No significant decomposition was observed even after a contact time of 1 hour.

Claims (22)

1. A method of controlling microbial growth in an aqueous system containing sulfite and/or bisulfite residues, said method comprising adding a composition comprising at least one peroxygen compound to said aqueous system having a pH greater than 5 . 2. The method of claim 1, wherein the peroxy compound is selected from the group consisting of hydrogen peroxide, alkali metal percarbonate, alkaline earth metal percarbonate, alkali metal perborate, alkaline earth metal perborate, Alkali metal persulfates, alkaline earth metal persulfates, organic peroxyacids and mixtures thereof. 3. The method of claim 2, wherein the peroxygen compound is hydrogen peroxide. 4. The method of any one of claims 1-3, wherein the composition further comprises a bleach activator. 5. The method of claim 4, wherein said bleach activator is tetraacetylethylenediamine. 6. The method according to any one of claims 1-5, wherein the pH is between 6 and 11. 7. The method of claim 6, wherein the pH is between 7.5 and 10. 8. The method according to any one of claims 1-7, wherein the pH of the aqueous system is selected from alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal bicarbonates, alkaline earth metal bicarbonates , alkali metal carbonates, alkaline earth metal carbonates, alkali metal metasilicates or mixtures thereof. 9. The method according to any one of claims 1-8, wherein the concentrations of the sulfite and/or bisulfite and the freshly added peroxy compound are each 1-300 ppm. 10. A method of stabilizing an active halogen biocide in a peroxide-containing aqueous system, said method comprising adding to the active halogen biocide before the active halogen biocide is combined with said peroxide-containing aqueous system agent to add N-hydrogen compounds. 11. The method of claim 10, wherein the concentration of active halogen (calculated as Cl ₂ ) stabilized by N-hydrogen compounds is 0.1-20 ppm. 12. The method as claimed in claim 10 or 11, wherein the N-hydrogen compound is selected from ammonia, ammonium salts, such as ammonium sulfate and ammonium bromide, nitrogen compounds without carbon-hydrogen bonds, such as urea, biuret, Sulfamic acid and isocyanuric acid, substituted N-hydrogen compounds such as methylsulfonamide, p-toluenesulfonamide, 5,5-dialkylhydantoin, barbituric acid, 5-methyluracil , imidazoline, pyrrolidone, morpholine, acetanilide, acetamide, N-ethyl-acetamide, phthalimide, benzamide, succinimide, N-methylolurea, N-methyl Urea, acetyl-urea, methyl allophanate, methyl carbamate, phthalohydrazide, pyrrole, indole, formamide, N-methylformamide, dicyandiamide, ethyl carbamate, 1,3- Dimethylbiuret, methylphenylbiuret, 4,4-dimethyl-2-oxazolidinone, 6-methyluracil, 2-imidazolinone, ethyleneurea, 2- Pyrimidinone, azetidin-2-one, 2-pyrrolidone, caprolactam, benzenesulfinimide, phenylsulfinimide amides, diarylsulfinimide, dialkylsulfinyl Imine, isothiazoline-1,1-dioxide, hydantoin, glycine, piperidine, piperazine, ethanolamine, glycinamide, creatine, glycoluril and mixtures thereof. 13. The method of claim 12, wherein the N-hydrogen compound is 5,5-dimethylhydantoin. 14. The method of claim 12, wherein the N-hydrogen compound is urea, ammonia or an ammonium salt. 15. The method of any one of claims 10-14, wherein the peroxide is selected from the group consisting of hydrogen peroxide, alkali metal percarbonate, alkaline earth metal percarbonate, alkali metal perborate, alkaline earth metal Perborates, alkali metal persulfates, alkaline earth metal persulfates, organic peroxyacids and mixtures thereof. 16. The method of claim 15, wherein the peroxide is hydrogen peroxide. 17. The method according to any one of claims 10-16, wherein the aqueous system is selected from the group consisting of pulp and papermaking slurry, slurry of recycled stock, stock slab, deinking liquid stock, stock or biomass Bleach slurries and liquids, fabric bleach solutions and slime. 18. The method of any one of claims 10-16, wherein the aqueous system is selected from wastewater, papermaking liquor and water, pond and spring water, industrial cooling water, water exposed to reverse osmosis filters or ion exchange resins and aqueous systems in oilfield applications including fractionating tanks and downhole applications. 19. The method of any one of claims 10-16, wherein the aqueous system is selected from the group consisting of food and crop protection applications including fruit and vegetable cleaning, meat and poultry processing, beverage processing, fish farming and aquaculture , an aqueous solution. 20. The method according to any one of claims 10-19, wherein the aqueous system comprising peroxide has been obtained by the method according to any one of claims 1-9. 21. A method for determining the concentration of peroxide in an aqueous system in the presence of sulfite and/or bisulfite, said method comprising the steps of: (i) adding a defined amount of excess N-hydrogen stabilized active chlorine compound to immediately destroy the sulfite and/or bisulfite while leaving an amount of unreacted N-hydrogen stabilized active chlorine compound, (ii) measuring the amount of unreacted N-hydrogen stabilized active chlorine compound to determine the sulfite and/or bisulfite concentration, and (iii) Determine the peroxide concentration. 22. The method of claim 21, wherein the N-hydrogen stabilized active chlorine compound is 1-chloro-5,5-dimethylhydantoin.