MXPA97008987A - Hypobromit of alkaline metal or alkalinoterreo, stabilized, and process for your producc - Google Patents

Abstract

The present invention relates to a method for preparing a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite, characterized in that it comprises: a. mixing an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent halogen available as chlorine, with a water-soluble bromide ion source, b. allowing the bromide ion source and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 70 weight percent unstabilized alkali metal or alkaline earth metal hypobromite, c. adding to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulphamate in an amount to provide a molar ratio of alkali metal sulfamate to alkaline or alkaline earth metal hypobromite from about 0.5 to about 7; and d. recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite

Description

mPOBRQ METAL METAL AT.rAT.1TJn n STABILIZED,? PKQCESQ FOR Sü sTSODO CTÓ l FIELD OF THE. INVENTION The present invention relates to a method for preparing an alkaline or alkaline earth metal hypobromite, stabilized to control microbioincrustation, more specifically, a stabilized sodium hypobromite solution, the characteristics of which include non-volatility, high residual free halogen, reduced bromate formation, reduced generation of absorbable organic halogen in the processing waters, as well as improved operation against biofouling.

Aqueous solutions of sodium hypochlorite are widely used to cool cooling towers; blamaqueado processes; treatment of recreational waters that include pool water, slip waters and other water play equipment, spas and whirlpools; disinfectants; detergents for laundry and industrial biocides "that include applications in the REP: 26241 oil. However, a major disadvantage of NaOCl is its instability. As is well known in the art, various methods are used to stabilize NaOCl. The reference of Self et al., (U.S. Patent No. 3,328,294) describes a continuous process for stabilizing hypochlorite with an equal molar ratio of sulfamic acid. This process is improved based on the preference of Rutkiewic (US Pat. No. 3,767,586) "who adds a buffer which helps in pH control by increasing the stability of concentrated solutions. Bromine has several advantages over chlorine for water treatment such as better performance at high pH or environments with amine and better volatility. However, sodium hypobromite, the bromine analogue of chlorine bleach, is not stable under typical storage conditions, and as such, is not commercially available. Instead, bromine is typically released to water treatment systems by various inefficient or inconvenient methods. The technique described by Self et al., Or by Rutkiewic does not mention a method for stabilizing the well-known, precarious, sodium hypobromite molecule, as described within this invention. Furthermore, this description improves with respect to the prior art of Rutkiewic in formulating a more stable concentrated NaOBr solution, in the absence of a buffer. In such a bromine delivery method, NaBr is in situ oxidized by producing gaseous chlorine or NaOCl in the process water stream. Another technique uses a stable perbromide solution (Br3.) Containing 30-40 percent bromine. The perbromide solution releases bromide and bromine when injected into water systems. Bromine formed instantly hydrolyzes hypobromous and hydrobromic acids. Alternatively, bromine chloride can be added to aqueous process streams where it hydrolyzes to hypobromous and hydrochloric acids. All these bromine release systems have inherent disadvantages. Chlorine gas, perbromide and bromine chloride have high halogen vapor pressures, which poses safety concerns in handling and storage. In addition, these concentrated halogen solutions are corrosive to many metal surfaces found in process equipment either because of their high vapor pressures or because of the release of one or more moles of hydrohalic acid in aqueous systems, which provides pH environments Low located. As such, none of these methods provides a stable bromine product that can be handled safely and easily and at the same time satisfies environmental requirements (which are discussed more fully below), such as a low generation of bromate and halogen Absorbable organic, and having high residual free halogen and low volatility (resulting in highly reduced vapor phase odor and corrosion). further, a portion of the expensive bromine compound is wasted through a byproduct that is not effective in some supply schemes. Therefore, the need for a product for water treatment with stable, economical, convenient and safe bromine still remains. The reference by Goodenough et al., (U.S. Patent No. 3,558,503) describes the stabilization of bromine using any compound which reacts reversibly with bromine. The disclosed compounds include: (a) primary or secondary water-soluble amines or amines; and (b) sulfamic acid and its water soluble salts. However, bromine solutions prepared according to the teachings of Goodenough et al. , are not high enough for practical use in commercial cooling water, in oil fields and in other industrial applications.

Sulfamic acid is used, according to the reference of Goodenough et al., As a free acid or as one of its water-soluble salts such as the sodium, potassium or ammonium salt. However, the manner in which the bromine solutions are prepared provides relatively low stabilities and low available halogen concentrations compared to the claims claimed within the description of this invention. The reference by Goodenough et al. , charges elemental bromine in aqueous solution before stabilization. Because elemental bromine is used in the process described in the reference by Goodenough et al., This process is difficult to carry out and at the same time is potentially dangerous since elemental bromine is a fuming, corrosive and toxic liquid. The reference by Goodenough et al. Mentions that the concentration of bromine available immediately after the preparation is about 1 weight percent. The low concentration of bromine obtained by this method is due in part to the fact that bromine is soluble only at 4 percent in cold water. Additionally, bromine is wasted in the process described in the reference by Goodenough et al. The reaction according to this process is as follows: Br2 + H20? HOBr + HBr Because the HBr produced does not function as a biocide, half of the bromine does not add anything to the strength of the biocidal species, HOBr. This description of the invention improves the reference of Goodenough et al., By means of a safer, easier and more economical process. Much higher concentrations of available halogen are obtained using the invention described in this application, as shown in Table 1 below, by stabilizing the sodium salt (NaOBr) generated during manufacture. As mentioned previously, sodium hypobromite is unstable and therefore not commercially available. If a stabilized form of NaOBr is proposed, the stabilization process should occur rapidly after NaOBr is prepared. The method described in the reference by Goodenough et al. Does not obtain these increased bromine concentrations since the order of addition of reagents described in the reference is not considered critical to the operability of the method. Since NaOBr is synthesized from the following reaction, NaOCl + NaBr-NaOBr + NaCl, the addition of the stabilizer before the oxidation of bromide does not allow the formation of NaOBr.

When treating water with many halogenated biocides, undesirable halogenated organic substances can be generated as by-products. These compounds are causing growing environmental and health concerns. It is generally known that halogenated organic substances of low molecular weight are degraded biologically more easily compared to high molecular weight species. However, low molecular weight forms can be more toxic to aquatic organisms and mammals. The differentiation of these halogenated organic substances is expensive, time consuming and requires the use of gas chromatography, high performance liquid chromatography or gel permeation chromatography. The organic absorbable halogen "AOX" is chosen as the method for measuring the sum of halogenated organic compounds without differentiation. The AOX is used as a verification parameter for effluents from water or wastewater in Europe and North America. In the United States, the environmental protection agency ("EPA") is closely seeking AOX downloads in the pulp and paper industry. An objective of the present invention is to provide a stable solution of NaOBr which can be used to control microbial encrustation with a minimum generation of AOX. The problems associated with the control of AOX concentrations have recently generated environmental concerns and have not been previously resolved in the industry. The United States EPA extrapolates some cases of animal carcinogenesis with the presence of low bromate concentrations found in drinking water. Bromate can appear from the ozonation of water containing bromide, which has generated certain concerns in the drinking water industry. Bromate can also be formed by disproportion of hypobromite. This reaction is carried out at a higher speed in alkaline environments. ThusIf bleach is added to a solution of NaBr, the high pH of the environment can lead to an undesirable production of bromate. One use of the present invention, which was previously unknown and is surprising, is to greatly minimize the formation of bromate by stabilizing the hypobromite when conditions are favorable for the production of bromate. The petroleum industry experiences biological problems, including microbiologically affected corrosion, both localized and general, of water in oil wells. In addition, the bacteria can plug the surfaces of the drilling wells in water flow injection wells. Mud plug bacteria reduce injection capacity. Treatment with waters containing stable bromine is a convenient method to solve these problems and similar problems. It is an object of the present invention to provide a process by which aqueous solutions of sodium hypobromite can be produced which are relatively resistant to degradation and / or decomposition and which are relatively non-corrosive and non-volatile, and which still retain a capacity improved for oxidation and bacterial activity. Another objective of the present invention is to provide a stable solution of sodium hypobromite in which the formation of AOX is minimized and at the same time to improve a control of microbial encrustation. Other objects and advantages of the present invention will become apparent from the following description thereof.

BRIEF DESCRIPTION OF THE INVENTION The invention, according to one embodiment, is a method for preparing a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite. The method comprises the steps of: a. Mix an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent available halogen as chlorine, with a water-soluble bromide ion source. b. Allow the source of the bromide ion and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 70 weight percent unstabilized hypobromite of alkali metal or alkaline earth metal. c. Add to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulphamate in an amount to provide a molar ratio of alkali metal sulfamate to alkali metal or alkaline earth metal hypobromite from about 0.5 to about 7; and d. Recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite.

One embodiment of the invention is a method for preparing a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite. The method comprises the steps of: a. Mix an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent available halogen as chlorine, with a water-soluble bromide ion source. b. Allow the source of the bromide ion and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 70 weight percent unstabilized hypobromite of alkali metal or alkaline earth metal. c. Add to the unstabilized solution of alkali metal or alkaline earth metal hipcjbromite an aqueous solution of an alkali metal sulfamate in an amount to provide a molar ratio of alkali metal sulfamate to alkali metal or alkaline earth metal hypobromite from about 0.5 to about 7; and d. Recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite. The alkali metal or alkaline earth metal hypochlorite is selected from the group consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite, lithium hypochlorite and calcium hypochlorite. The amount of hypochlorite used will depend on which hypochlorite salt is used. The bromide ion source is selected from the group consisting of sodium bromide, potassium bromide, lithium bromide and hydrobromic acid. As shown in the examples, in a more preferred embodiment, the alkali metal or alkaline earth metal hypochlorite is sodium hypochlorite, the bromide ion source is sodium bromide, and the alkali metal or alkaline earth metal hypobromite is sodium hypobromite. The aqueous solution of the non-stabilized alkali metal or alkaline earth metal hypobromite may contain from about 0.5 to about 70 weight percent alkali metal or alkaline earth metal hypobromite, more preferably from about 1 to about 30 weight percent hypobromite alkaline or alkaline earth metal, more preferably from about 4 to about 15 percent alkaline or alkaline earth metal hypobromite. The pH of the alkaline or alkaline earth metal hypobromite stabilized aqueous solution is from about 8 to about 14, and more preferably from about 11 to about 14. The molar ratio of the alkali metal sulphamate to the sodium hypobromite is preferably is from about 0.5 to about 7, more preferably from about 0.5 to about 4, and much more preferably from about 0.5 to about 2.

Another embodiment of the invention is a stabilized aqueous solution of an alkali metal or alkaline earth metal hypobromite which is prepared by the steps of: a. Mix an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent halogen available as chlorine, with a source of water-soluble bromide ion. b. Allow the source of the bromide ion and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 70 weight percent unstabilized hypobromite of alkali metal or alkaline earth metal. c. Add to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulphamate in an amount to provide a molar ratio of alkali metal sulfamate to alkaline or alkaline earth metal hypobromite from about 0.5 to about 7.; and d. Recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite. The alkali metal or alkaline earth metal hypochlorite is selected from the group consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite, lithium hypochlorite and calcium hypochlorite. The amount of hypochlorite used varies based on which hypochlorite salt is used. The bromide ion source is selected from the group consisting of sodium bromide, potassium bromide, lithium bromide and hydrobromic acid. As shown in the examples, in a more preferred embodiment, the alkali metal or alkaline earth metal hypochlorite is sodium hypochlorite, the source of the bromide ion is sodium bromide and the alkali metal or alkaline earth metal hypobromite is sodium hypobromite. The non-stabilized alkali metal or alkaline earth metal hypobromite solution may contain from about 0.5 to about 70 weight percent alkali metal or alkaline earth metal hypobromite, more preferably from about 1 to about 30 weight percent metal hypobromite alkaline or alkaline earth metal, and more preferably from about 4 to about 15 weight percent of alkali metal or alkaline earth metal hypobromite. The pH of the alkaline or alkaline earth metal hypobromite stabilized aqueous solution is from about 8 to about 14, and more preferably from about 11 to about 14. The molar ratio of alkali metal sulfamate to sodium hypobromite is preferably is from about 0.5 to about 7, more preferably from about 0.5 to about 4, and much more preferably from about 0.5 to about 2. The invention can be used in an industrial water system. Such systems would contain from about 0.05 to about 1000 ppm, more preferably from about 0.05 to about 10 ppm, and more preferably from about 0.1 to about 5 ppm of the stabilized aqueous solution of an alkaline or alkaline earth metal hypobromite. The invention can be used in laundry of soiled garments in which the soiled garments are washed in an aqueous medium such as water, which contains a detergent and a bleaching agent. The stabilized aqueous solution of an alkali metal or alkaline earth metal hypobromite can be used as the bleaching agent. The invention can also be used in the manufacture of cellulosic materials in which the cellulosic fibers are bleached with an oxidizing agent. The stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite can be used as the oxidizing agent.

The invention can be used in the control of microbioincrustations in a recreational water systems in which the oxidizing agent is added to control the microbioincrustation. The stabilized aqueous solution of an alkali metal or alkaline earth metal hypobromite can be used as the oxidizing agent. The invention can be used in the control of microbioincrustation that occurs in surfaces of equipment in contact with waters in oil fields. An effective amount against microbioincrustation of a stabilized aqueous solution of an alkaline or alkaline earth metal hypobromite may be added to the producing oil field waters. The invention can also be used in the control of microbioincrustation in aqueous systems. An amount effective against microbioincrustation of a stabilized aqueous solution of an alkali metal or alkaline earth metal hypobromite can be added to aqueous systems. In another embodiment, the invention is a method for preventing micro-fouling on surfaces of the equipment in contact with an industrial water system. The method comprises adding to the aqueous system an effective antimicrobiological amount of a stabilized sodium hypobromite solution. The stabilized sodium hypobromite solution is prepared by the steps of: a. Mix an aqueous solution of sodium hypochlorite having from about 5 percent to about 30 percent available halogen (such as chlorine), with sodium bromide; b. Allow sodium bromide and sodium hypochlorite to react to form an aqueous solution of 0.5 to 30 percent by weight of unstabilized sodium hypobromite; c. Add to the unstabilized solution of sodium hypobromite an aqueous solution of an alkali metal sulphamate in an amount to provide a molar ratio of alkali metal sulphamate to sodium hypobromite from about 0.5 to about 7; and d. Recover a stabilized aqueous solution of sodium hypobromite. Industrial water systems include cooling water systems, cooling dams, reservoirs, freshwater applications, decorative fountains, pasteurizers, evaporative condensers, hydrostatic sterilizers and retorts, gas elimination systems and air washing systems.

Another embodiment of the invention is a method for preparing a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite when the concentration of halogen available as chlorine is less than about 5 percent. The method comprises the steps of: a. Mix an aqueous solution of alkali metal or alkaline earth metal hypochlorite [in which the available halogen percent (such as * chlorine) is less than about 5] with a source of water-soluble bromide; b. Allowing the source of the bromide ion and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.0 to 5 weight percent of alkaline or alkaline earth metal hypobromite not stabilized; c. Add to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulfamate having a temperature of at least 50 ° C in an amount to provide a molar ratio of alkali metal sulfamate to hypobromite alkali metal, or alkaline earth metal from about 0.5 to about 7; and d. Recover a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite.

When the concentration of halogen available as chlorine is below about 5 percent, the amount of water in which the stabilizer, the alkali metal sulfamate, dissolves must decrease. At this point, the amount of water is low enough so that the alkali metal sulphamate is only sparingly soluble in the water. Thus, the temperature of the aqueous solution of alkali metal sulphamate should be maintained above 50 ° C to keep the alkali metal sulfamate in solution until the solution is added to an aqueous solution of unstabilized sodium hypobromite. Once mixed with the sodium hypobromite solution, solubility is no longer a concern and the resulting stabilized solution of sodium hypobromite does not need to be maintained at a temperature above 50 ° C. The alkali metal or alkaline earth metal hypochlorite is selected from the group consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite, lithium hypochlorite and calcium hypochlorite. The amount of hypochlorite used varies based on which hypochlorite is used. The bromide ion source is selected from the group consisting of sodium bromide, potassium bromide, lithium bromide and hydrobromic acid. As shown in the examples, in a more preferred embodiment, the alkali metal or alkaline earth metal hypochlorite is sodium hypochlorite, the source of the bromide ion is sodium bromide and the alkali metal or alkaline earth metal hypobromite is sodium hypobromite. The non-stabilized alkali metal or alkaline earth metal hypobromite solution may contain from about 0.05 to about 70 weight percent alkali metal or alkaline earth metal hypobromite, more preferably from about 1 to about 30 weight percent hypobromite alkaline or alkaline earth metal, and most preferably, from about 4 to about 15 weight percent alkali metal or alkaline earth metal hypobromite. The pH of the alkaline or alkaline earth metal hypobromite stabilized aqueous solution is from about 8 to about 14, and more preferably from about 11 to about 14. The molar ratio of the alkali metal sulphamate to the sodium hypobromite, so preferable is from about 0.05 to about 7, more preferably from about 0.5 to about 4, and much more preferably from about 0.5 to about 2.

Another embodiment of the invention is a stabilized aqueous solution of an alkali metal or alkaline earth metal hypobromite, which is prepared by the steps of: a. Mixing an aqueous solution of alkali metal or alkaline earth metal hypochlorite [wherein the available halogen percent (such as chlorine) is less than about 5] with a source of water-soluble bromide ion; b. Allowing the bromide ion source and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 5 weight percent hypobromite of alkaline or non-stabilized alkaline earth metal; c. Add to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulfamate having a temperature of at least 50 ° C in an amount to provide a molar ratio of alkali metal sulfamate to hypobromite alkaline or alkaline earth metal from about 0.5 to about 7; and d. Recover a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite. As described above, when the concentration of halogen available as chlorine is less than about 5 percent, the amount of water in which the stabilizer, the alkaline earth metal sulfamate, is dissolved, must decrease. At this point, the amount of water is so low that the alkali metal sulfamate is only sparingly soluble in water. Therefore, the temperature of the aqueous alkali metal sulfamate solution should be maintained above 50 ° C to keep the alkali metal sulfamate in solution until the solution is added to the aqueous solution of unstabilized sodium hypobromite. Once mixed with the sodium hypobromite solution, solubility is no longer a concern, and the resulting stabilized sodium hypobromite solution does not need to be maintained above 50 ° C. The alkali metal or alkaline earth metal hypochlorite is selected from the group consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite, lithium hypochlorite and calcium hypochlorite. The amount of hypochlorite used will vary based on which hypochlorite is used. The bromide ion source is selected from the group consisting of sodium bromide, potassium bromide, lithium bromide and hydrobromic acid. As shown in the examples, in a more preferred embodiment, the alkali metal or alkaline earth metal hypochlorite is sodium hypochlorite, the source of the bromide ion is sodium bromide and the alkali metal or alkaline earth metal hypobromite is sodium hypobromite. The non-stabilized alkali metal or alkaline earth metal hypobromite solution may contain from about 0.5 to about 70 weight percent alkali metal or alkaline earth metal hypobromite, more preferably from about 1 to about 30 weight percent metal hypobromite alkaline or alkaline earth metal, and more preferably from about 4 to about 15 weight percent of alkali metal or alkaline earth metal hypobromite. The pH of the alkaline or alkaline earth metal hypobromite stabilized aqueous solution is from about 8 to about 14, and most preferably from about 11 to about 14. The molar ratio of the alkali metal sulphamate to the sodium hypobromite is preferably is from about 0.5 to about 7, and more preferably from about 0.5 to about 4, and most preferably from about 0.5 to about 2. In another embodiment, the invention is a method to prevent microbioincrustation on the surfaces of equipment in contact with an industrial water system. The method comprises adding to the aqueous system an effective antimicrobiological amount of a stabilized solution of sodium hypobromite. The stabilized solution of sodium hypobromite is prepared by the stages of: a. Mix an aqueous solution of sodium hypochlorite [in which the available halogen percent (such as chlorine) is less than about 5] with sodium bromide; b. Allow sodium bromide and sodium hypochlorite to react to form an aqueous solution of 0.5 to 5 percent by weight of unstabilized sodium hypobromite; c. Add to the unstabilized solution of sodium hypobromite an aqueous solution of an alkali metal sulphamate having a temperature of at least 50 ° C in an amount to provide a molar ratio of alkali metal sulfamate to sodium hypobromite from about 0.5 to approximately 7; and d. Recover a stabilized aqueous solution of sodium hypobromite. As described above, when the concentration of halogen available as chlorine is less than about 5 percent, the amount of water in which the stabilizer is dissolved, the alkali metal sulfamate should decrease. At this point, the amount of water is low so that the alkali metal sulfamate is only sparingly soluble in the water. Therefore, the temperature of the aqueous alkali metal sulphamate solution should be maintained at least at 50 ° C to keep the alkali metal sulphamate in solution until the solution is added to the aqueous solution of unstabilized sodium hypobromite. Once mixed with the sodium hypobromite solution, solubility is no longer a concern, and the resulting sodium hypobromite solution does not need to be maintained at least 50 ° C. This invention provides several differences with respect to the known art, including the specific order of addition in the manufacturing process, whereby a stabilized solution of sodium hypobromite having improved stability, non-volatility, reduced formation of bromate is produced. and from AOX, an improved control of microbioincrustation and a residual free halogen increased in cooling water. The stability of the stabilized hypobromite solution, in comparison with the stabilized bromine described in the Goodenough et al. Reference, and the unstabilized sodium hypobromite in Table I, is greatly increased. Based on the surprisingly increased stability of the stabilized sodium hypobromite of this invention, it is evident that the order of action in the manufacturing process is critical.

The chemical mechanism for the stabilization of halogen biocidal by sulfamic acid has been proposed as follows: HO-X + H-NH- SO3H-NH-SO3H H20 (Xlibrβ) (stable X ') When X is Cl, the reaction is applied to the stabilized chlorine. When X is Br, the reaction is applied to stabilized bromine.

The degree of stabilization is expressed as the ratio in X-stable concentration to X-free. The concentration of Xlibre stabilized bromine is detectable, while «that the concentration of X? Ibre for stabilized chlorine does not. It is concluded that the chlorine in the stabilized chlorine is completely stabilized, while the bromine in the stabilized bromine exists in both free and stabilized forms. This contributes, in part, to the increased antimicrobial properties of stabilized NaOBr with respect to stabilized NaOCl which will be described in greater detail in Example 3. The organic absorbable halogen (AOX) is an important environmental parameter particularly in Europe. AOX can be formed from the reaction of certain halogenated compounds with organic substances. The minimization of AOX by stabilizing NaOBr is a surprising benefit described in this description.

Track A: AOX training by HOX HO-X R-X X-R H20 Where R-H can be organic contaminants in cooling water or biomacromolecules, and X-R is measured as AOX.

Via B: X-NH-S03H + R-H? R-NH-SO3H + HX This stabilized halogen reaction does not generate XR (AOX) as in channel A. When free chlorine ((HOCl) or free bromine (HOBr) is used, AOX will be formed according to the mechanism described in channel A. When stabilized chlorine is used as a biocide, it is only It is possible to route B because there is no free HOC1 in the system, therefore, nothing or very little AOX will be formed using this product (see table II below) When stabilized bromine is used, free and stabilized forms coexist Therefore, both routes, A and B, are carried out and result in some AOX formation, however, the amount of AOX will be much lower when all of the halogen is in the form of free bromine (HOBr) Apparently, the proposed mechanism explains the cause of AOX reduction due to the use of biocides and stabilized halogen The mechanism may be applicable to other stabilized halogen products when ammonia, amines or amides are used as the stabilizing agents.

In order to reduce the formation of AOX by a stabilized halogen biocide, it is preferable to select • strong stabilizing agents so that the B path prevails. However, the drawback to a very stable halogen compound is generally a diminished potency of action which, in most cases, directly correlates with its biocidal efficacy. Tests have shown that stabilized bromine is much more effective as a biocide than stabilized chlorine. Therefore, to reduce the formation of AOX and at the same time maintain the biocidal efficacy of the compounds a very balanced selection of the stabilizing agent is required. The following examples are presented to describe the preferred embodiments and utilities of the invention and do not signify limitation of the invention, unless otherwise stated in the appended claims.

Example 1 Preparation dft hypnfít? I f > you? "~ n M | ,, M 1 -" ft rm? m opifln < ift critical criticism In order to demonstrate the constancy of stabilized NaOBr, solutions of sodium hypochlorite and sodium bromide that form NaOBr are mixed and then stabilized with sodium sulfamate as described below. The sodium hypochlorite solution is diluted with water as required. The diluted solution is titrated by the DPD-FAS method. The concentration of available chlorine in the original solution is determined to be 15 percent. 42.4 grams of the pure NaOCl solution are added to 20.5 grams of a 45% solution of NaBr. This reaction forms NaOBr unstabilized. The stabilization solution is formulated with 9.6 grams of sulfamic acid, 14 grams of water and 13.2 grams of 50 percent sodium hydroxide. The stabilization solution is then added with stirring to NaOBr. The order of addition is critical in this process which differs from that of Goodenough et al. For example, if the stabilizer is added to NaOCl prior to the introduction of NaBr, the bromide would not be oxidized to hypobromite. In addition, bromine solutions prepared in the manner mentioned above provide more stable oxidizing species compared to the prior art. Stabilized bromine solutions as explained in the Goodenough et al. Reference, show a decrease in halogen activity from an initial concentration of 1 percent to 0.77 percent after 14 days, which represents a loss of active ingredient of 23 percent. The stabilization procedure described in the present improvement with respect to that of the prior art since the decline of the active ingredient is only 1 percent after 84 days (see table 1 above). An unstabilized NaOBr solution prepared in a similar process by substituting sulfamic acid with distilled water loses 94 percent available halogen during the same period.

Ejey? P'l "2 fíft sign tmv? a * oy and «« - > ? »< -H "n« «A * TiaiAym» «^ tab1 * i-« ^ " AOX is a generic class of compounds which include all organic molecules that contain halogen. The limits for the discharge of AOX from cooling water systems has already been established in some European countries. To simulate the formation of AOX during the formation of the stabilized and unstabilized sodium hypochlorite action in cooling water, a mixed bacterial culture typically grown in cooling water in L-broth is grown overnight, and the cells are cultured. they collect by centrifugation. The cell pellet is washed with synthetic cooling water (90 ppm of calcium, 50 ppm of magnesium, 100 ppm of "M", alkalinity, pH 8.0-8.2) twice, to eliminate the remaining organic medium. The cells are then resuspended in an equal volume of cooling water. A bottle in the dark and covered serves as a reactor. The synthetic cooling water is added to the bottle after washing the bacterial accumulation which provides 107 cells / ml. Stabilized NaOBr or unstabilized NaOBr is metered into this bacterial suspension at a final concentration of 1, 2, 3 or 4 ppm of total halogen (as chlorine). The free space in the bottle is minimized to avoid the loss by evaporation of halogenated organic compounds and the solution is stirred for 24 hours to simulate a typical cooling system. Immediately before analysis for AOX, the sample is acidified to pH 2.0 with concentrated nitric acid. A Mitsubishi TOX-10 analyzer is used according to the US EPA 9020 method to measure the concentration of AOX in the samples. Ultrapure water is used for the preparation of all reagents and standard solutions to avoid any contamination. The amount of AOX formed in each of such treatments is shown in Table 2 below. Cooling water with stabilized NaOBr forms less AOX than treatments using NaOBr without stabilizing at equivalent concentrations of halogen. Linear radiations are performed in both data sets to obtain the linear fit equations shown below for stabilized and unstabilized NaOBr: stabilized NaOBr: AOX (ppb) = 23.3 X Dosage (ppm) NaOBr unstabilized: AOX (ppb) = 53.9 X Dosage (ppm) Evidence is also shown that the stabilization of NaOCl reduces the generation of AOX to dosed cooling water to two residual total ppm (see Table II).

EÍejpr¿lo__l Activity - anti- Usacteriana da po-arrcm-i ¡a aod Q stabilized Freshly prepared solutions of stabilized and unstabilized sodium hypobromite are diluted and then added to cooling water in order to obtain 1 ppm free residual halogen (such as chlorine). Sodium hypochlorite is stabilized in the same manner as described for NaOBr in Example 1, except that "NaBr is directly replaced with distilled water. Stabilized and unstabilized sodium hypochlorite is diluted and then added to cooling water to a final concentration of 1 ppm residual free halogen (such as chlorine). The volumes of all the solutions are recorded as needed to obtain 1 ppm free residual halogen (such as chlorine). After 6 and 21 days of storage in the dark, identical dilutions of stabilized and unstabilized sodium hypohalide solutions are prepared and the volume originally required for 1 ppm free residual halogen (as chlorine) is added to the cooling water containing about 10S cells of Pseudcmsnas aerugzLosa / 'ml. Aliquots are removed at 10 and 30 minutes of cooling water dilution blank containing a halogen neutralizer (0.05 percent Na2S203) and then enumerated on glucose extract and tryptone agar. The stabilized NaOBr retains its antibacterial activity after storage while the unstabilized form loses its effectiveness against Pseudornonas auroginosa (see table III below). The results were even more noticeable when storage periods are increased. This effect is probably due to a lack of proportion of unstable hypobromite ion in the non-biocidal species of bromide and bromate. In a surprising way, NaOCl stabilized in the same way «that NaOBr is, comparatively, ineffective under the conditions tested (table III) what 4; -of - formation - of brómat - posterior stabilization, sodium hypobromite It is known that hypohalite ions are separated or disproportionated in halide and halide under alkaline conditions. Halato ions are undesirable degradants as they are suspected to be carcinogenic and are under consideration for government regulation. The reaction of NaBr with NaOCl can provide significant amounts of bromate in high pH environments. Surprisingly, the stabilization of NaOBr with sodium sulfamate greatly minimizes the formation of bromate (see Table IV below). Stabilized and non-stabilized solutions of sodium hypobromite are prepared as described in example 1. These solutions are stored in the dark at room temperature during the course of the study. Tests are conducted for bromate in eight-month-old samples of stabilized and unstabilized NaOBr, both maintained at pH 14, a suitable condition for the formation of bromate. A Dionez 4000 series gradient ion chromatography system equipped with column AG9-SC / AS9-SC and a conductivity detector was used to determine the bromate concentration in the samples. The chromatograph operates according to the method currently under investigation by EPA for the analysis of bromate in ozonated potable water. Purified water from the deionization system of Interlake Water Systems is used for the preparation of all reagents and standard solutions to avoid contamination.

As indicated in the above, the pH of these solutions is high, which favors the formation of bromate. However, NaOCl, which contains significant amounts of NaOH, is typically diluted with system water prior to the introduction of the bromide species in most industrial applications. The pH of this diluted system is lower than that of the pure NaOCl / NaBr formulation described above, which theoretically minimizes bromate formation. The available chlorine in a NaOCl sample diluted (1: 100) with distilled water is titrated by the DPD-FAS method. A solution of 45% sodium bromide is added to dilute NaOCl in a molar ratio of 1 Cl2: 1 Br "which forms NaOBr This reaction is allowed to proceed for thirty minutes, then the appropriate volumes of this NaOBr solution are added. diluted to cooling water (pH 8.3) which provides available halogen concentrations of 1, 2, 3 and 4 ppm (as Cl2) determined by the DPD-FAS method. stabilized sodium (1: 100) in distilled water, diluted stabilized NaOBr is added to cooling water (pH 8.3), which provides total available halogen concentrations of 1,2,3 and 4 ppm (as Cl 2) determined by the method of DPD-FAS The bromate analysis is then carried out in the manner described above Bromate does not detect any of the cooling water samples dosed with diluted NaOBr stabilized or unstabilized at typical use concentrations. they mean a safety factor for the bromate accumulation in the stabilized sodium hypobromite formulation as well as the industrial oxidation zin if your NaBr with diluted NaOCl.

Kj-aflo 5 » free residual in a system of agina gives «anf r * tnjenfrp recirculantß compared with other cc ^ y» «*; fl d "h ^ gg ^^ ^ ñt.flhil 17? f? QR A major drawback of some commercial stabilized chlorine products for industrial water treatment is the low percentage of residual free chlorine supplied to the water system. This effect is due to the strength of the chemical bond between the stabilizer, usually a nitrogenous compound, and chlorine. Chloramines, that is, combined chlorine, are microbiocides that are weaker than free chlorine. However, bromamines are considered almost as effective against microorganisms as free bromine. Therefore, it is essential to have a high percentage of total available halogen in free form when using chlorine products. Inversely, this phenomenon is not crucial when using stabilized NaOBr. In a commercial heating cooling system, ventilation and air conditioning ("HVAC") is treated sequentially with stabilized NaOCl, a bromochloroalkylidantoin and finally stabilized NaOBr. There is a low percentage of free chlorine in relation to the total available halogen present in the system treated with stabilized NaOCl (see table V below). A lower percentage of free halogen was measured when using a different stabilization system, an alkynidadein, with bromine and chlorine (see table V below). However, when this stabilized NaOBr system is fed, the percentage of available free halogen in relation to the rapidly increased total residual measured (see table V below). This phenomenon implies that stabilized NaOBr is required to obtain a free available halogen residual compared to an equivalent amount of stabilized NaOCl.

Example Seia Stabilization gives «ipobr myth or sodium reduces volatility If a biocide is highly volatile, its operation may be adversely affected. For example, the biocide can be released by flash evaporation under highly designed conditions of a cooling tower or an air scrubber. This would decrease the concentration of biocide in the cooling water that is wasted in the product. The volatility of halogen also leads to corrosion of the vapor phase of susceptible equipment surfaces. In addition, the volatility of halogen can cause discomfort to workers due to the "pool" aroma. Therefore, a need for an effective oxidant biocide with low volatility is evident. The concentrated solutions of both NaOCl, stabilized NaOBr are added to a beaker. Halogen vapors are detected from the NaOCl and NaOBr solutions. No odors are perceived from stabilized NaOBr. This is an improvement over existing products by minimizing halogen odors in product storage areas.

The bleach, NaOCl is not commonly used in air washing systems for some of the reactions mentioned above. Once an effective microbial control dose is obtained, the halogen odor can be so strong that workers are not able to operate comfortably in treated areas. The low volatilization of stabilized NaOBr solves this drawback. Sodium hypobromite stabilizer at high use concentrations is added to two textile mill air washers in order to investigate their volatility. Then the air is checked through the mill. A Sensidyne air verification device fitted with tubes for halogen detection is used to instantly detect halogen in the air. The lower limit of detection is 50 ppb, which is below the threshold-limit limit value for short-term exposure to bromine as established by OSHA. In addition, halogen labels are placed through the textile mills in order to detect halogen vapors over extended periods of time. No monitoring system detected any halogen present in the air after the high stabilized NaOBr dose. No halogen odors were found in the air wash unit or the return air. The microbial population was enumerated before and after the addition of stabilized NaOBr. The microbial population after dosing is reduced by more than one order of magnitude. This example demonstrates the utility of stabilized sodium hypobromite to control the bacterial population and at the same time does not generate a halogen odor in the system area. Changes may be made in the composition, operation and arrangement of the method of the present invention described herein without departing from the concept and scope of this invention, as defined in the following claims. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (21)

REIVT ^ ICACIQNES

1. A method for preparing a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite, characterized in that it comprises: a. aezclar an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent halogen available as chlorine, with a source of water-soluble bromide ion. b. Allow the source of the bromide ion and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 70 weight percent unstabilized hypobromite of alkali metal or alkaline earth metal. c. adding to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulphamate in an amount to provide a molar ratio of alkali metal sulfamate to alkali metal or alkaline earth metal hypobromite from about 0.5 to about 7; and d. recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite.

2. The method according to claim 1, characterized in that the alkali metal or alkaline earth metal hypobromite is selected from the group consisting of sodium hypochlorite, potassium hypochlorite, lithium hypochlorite, magnesium hypochlorite and calcium hypochlorite.

3. The method according to claim 1, characterized in that the bromide ion source is selected from the group consisting of sodium bromide, potassium bromide, lithium bromide and hydrobromic acid.

4. The method according to claim 1, characterized in that the alkali metal or alkaline earth metal hypochlorite is sodium hypochlorite, the source of the bromide ion is sodium bromide and the alkali metal or alkaline earth metal hypobromite is sodium hypobromite.

5. The method according to claim 1, characterized in that the non-stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite contains from about 1 to about 30 weight percent hypobromite of alkali metal or alkaline earth metal.

6. The method according to claim 1, characterized in that the non-stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite contains from about 4 to about 15 weight percent hypobromite of alkali metal or alkaline earth metal.

7. The method according to claim 4, characterized in that the aqueous solution of unstabilized sodium hypobromite contains from about 1 to about 30 weight percent sodium hypobromite.

8. The method according to claim 4, characterized in that the aqueous solution of unstabilized sodium hypobromite contains from about 4 to about 15 weight percent sodium hypobromite.

9. The method according to claim 7, characterized in that the pH of the stabilized aqueous solution of sodium hypobromite is from about 8 to about 1.

10. The method according to claim 8, characterized in that the pH of the stabilized aqueous solution of sodium hypobromite is from about 11 to about 14.

11. The method according to claim 9, characterized in that the molar ratio of alkali metal sulfamate to sodium hypobromite is from about 0.5 to about 4.

12. The method according to claim 10, characterized in that the molar ratio of the alkali metal sulphamate to the sodium hypobromite is from about 0.5 to about 2.

13. A stabilized aqueous solution of an alkali metal or alkaline earth metal hypobromite, characterized in that it is prepared by the steps of: a. mixing an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent available halogen as chlorine, with a water-soluble bromide ion source; b. providing that the source of the bromide ion and the alkali metal or alkaline earth metal hypochlorite react to form an unstabilized aqueous solution of 0.5 to 30 weight percent alkali metal or alkaline earth metal hypobromite; c. adding to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulfamate in an amount to provide a molar ratio of alkali metal sulfamate to alkali metal or alkaline earth metal hypobromite from about 0.5 to about 7; and d. recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite.

14. An industrial water system characterized in that it contains from about 0.05 to about 1000 ppm of the solution according to claim 13.

15. An improved method for washing soiled garments in which soiled garments are washed in an aqueous medium containing a detergent and a bleaching agent, the improvement is characterized in that it comprises using as the bleaching agent the solution according to claim 13.

16. An improved method for the manufacture of cellulosic materials in which the cellulosic fibers are bleached with an oxidizing agent, the improvement is characterized in that it comprises using the oxidizing agent solution according to claim 13.

17. An improved method for microbioincrustation control in a recreational water system in which the oxidizing agent is added to control the microbioincrustation, the improvement is characterized in that it comprises using the solution according to claim 13 as the oxidizing agent.

18. An improved method for the control of microbioincrustation that occurs on surfaces of equipment in contact with waters in producing oil fields, the improvement is characterized in that it comprises adding to the producing oil field waters an effective amount antimicrobioincrustante of the solution in accordance with Claim 13

19. A method for controlling microbioincrustation in an aqueous system characterized in that it comprises adding to the aqueous system an effective and antimicrobioincrustant amount of the solution according to claim 13.

20. A method for preventing microbioincrustation on surfaces of equipment in contact with an industrial water system characterized in that it comprises adding to the aqueous system an effective antimicrobiological amount of a stabilized solution of sodium hypobromite, the solution has been prepared by the steps of: a. mixing an aqueous alkali metal or alkaline earth metal hypochlorite solution having from about 5 percent to about 70 percent halogen available as chlorine, with a water-soluble bromide ion source; b. allowing the bromide ion source and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 30 weight percent of unstabilized hypobromite of alkali metal or alkaline earth metal; c. adding to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulfamate in an amount to provide a molar ratio of sulfamate to hypobromite from about 0.5 to about 7; and d. recover the stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite.

21. The method according to claim 20, characterized in that the industrial water system is selected from the group consisting of: a cooling water system; freshwater system; a gas elimination system and an air washing system. The invention is a method for preparing a stabilized aqueous solution of alkali metal or alkaline earth metal hypobromite. The method comprises the steps of: a) mixing an aqueous solution of alkali metal or alkaline earth metal hypochlorite having from about 5 percent to about 70 percent available halogen as chlorine with a source of water-soluble bromide ions; b) allowing the bromide ion source and the alkali metal or alkaline earth metal hypochlorite to react to form an aqueous solution with 0.5 to 70 weight percent of alkaline or alkaline earth metal hypobromite, not stabilized; c) adding to the non-stabilized solution of alkali metal or alkaline earth metal hypobromite an aqueous solution of an alkali metal sulphamate in an amount to provide a molar ratio of alkali metal sulfamate to alkaline or alkaline earth metal hypobromite from about 0.5 to about 7; and d) recovering the alkaline or alkaline earth metal hypobromite stabilized solution.