Hypobromite Is Used to Purify Contaminated Water. What Is the Formula for Hypobromite?
A Procedure TO Manufacture STABILIZED Brine OR ALKALINE
EARTH METAL HYPOBROMITE AND USES THEREOF IN WATER
TREATMENT TO CONTROL MICROBIAL FOULING
The nowadays invention relates to a method of preparing a stabilized brine or
alkaline earth metal hypobromite to command microbiofouling, more than specifically, a
stabilized sodium hypobromite solution the characteristics of which include non-
volatility, loftier free halogen residuum, lower bromate formation, reduced generation of
absorbable organic halogen in process waters, as well every bit improved performance
against biofouling.
Background of the Invention
Aqueous solutions of sodium hypochlorite are widely used in cooling h2o
towers; bleaching processes; treatment of recreational waters including pond
pool water, water slide and other water game equipment, spas, and whirlpools;
disinfectants; laundry detergents; and, industrial biocides including applications in
the petroleum industry. However, a major disadvantage of NaOCl is its instability.
As is well known in the art, several methods are used to stabilize NaOCl. The Self et
al. reference (U.South. Pat. No. 3,328,294) described a continuous process to stabilize
hypochlorite with an equal molar ratio of sulfamic acid. This process was improved
upon by Rutkiewic reference (U.S. Pat. No. 3,767,586) who added a buffer which
aided in pH command increasing the stability of full-bodied solutions.
Bromine has diverse advantages over chlorine for water treatment such as
better performance in high pH or amine environments and a lower volatility. However, sodium hypobromite, the bromine analog to chlorine bleach, is not stable
under typical storage conditions, and as such, is not commercially available. Instead,
bromine is typically delivered to h2o handling systems past diverse inefficient or
inconvenient methods. The fine art described past either Cocky et al. or Rutkiewic does not
mention a method to stabilize the well known precarious sodium hypobromite
molecule as disclosed within this invention. Also, this disclosure shall improve upon
the art of Rutkiewic by formulating a more than stable, concentrated NaOBr solution in the
absence of a buffer.
In one such bromine commitment method, NaBr is oxidized in situ by introducing
gaseous chlorine or NaOCl into the process h2o stream. Some other technique uses a
stable perbromide (Br3-) solution containing thirty - 40 percentage bromine. The perbromide
solution releases bromide and bromine when injected into water systems. The formed
bromine hydrolyzes instantly to hypobromous and hydrobromic acids. Alternatively,
bromine chloride may be added to aqueous process streams wherein it hydrolyzes to
hypobromous and hydrochloric acids.
All of these bromine delivery systems have inherit disadvantages. Gaseous
chlorine, perbromide, and bromine chloride take high element of group vii vapor pressures which
present rubber concerns in handling and storage. Also, these full-bodied halogen
solutions are corrosive to many metal surfaces institute in process equipment either past
their high vapor pressures or by the release of one mole of hydrohalic acids in h2o
systems yielding localized low pH environments. As such, none of these methods provide a stable bromine product that can be safely and easily handled while meeting
environmental requirements (more than fully discussed below), such as low bromate and
absorbable organic halogen generation, and having a loftier gratuitous halogen residual and a
depression volatility (resulting in a greatly reduced aroma and vapor-stage corrosion). In
improver, a portion of the expensive bromine compound is wasted through an
ineffective past-product in some commitment schemes. Thus, the need for a safety,
convenient, economical, stable bromine h2o treatment production remains and is
significant.
The Goodenough et al. reference (U.Due south. Pat. No. 3,558,503), teaches
stabilization of bromine using whatever compound which reacted reversibly with bromine.
The disclosed compounds include:
(a) h2o-soluble primary and secondary amines or amides; and,
(b) sulfamic acid and its water-soluble salts.
However, the bromine solutions prepared according to the Goodenough et al.
reference teachings are not stable enough for practical use in commercial cooling
h2o, oil field and other industrial applications.
Sulfamic acrid, according to the Goodenough et al. reference, is employed as a
free acid or as ane of its h2o-soluble salts such as the sodium, potassium or
ammonium salt. However, the manner in which the bromine solutions are prepared
provide relatively low stabilities and low available halogen concentrations compared
with the discoveries claimed inside this invention disclosure. The Goodenough et al. reference charges elemental bromine into aqueous solution prior to stabilization.
Considering elemental bromine is used in the process disclosed in the Goodenough et al.
reference, this process is difficult to complete as well as potentially hazardous since
elemental bromine is a fuming, corrosive, toxic liquid.
The Goodenough et al. reference mentions that the bachelor bromine
concentration immediately post-obit preparation was about one percent by weight. The
low bromine concentration achieved past this method was due in part to bromine being
soluble at just 4 percent in cold h2o. Additionally, bromine is wasted in the procedure
disclosed in the Goodenough et al. reference. The reaction according to this procedure is
as follows:
Br2 + H2O → HOBr + HBr
Because the produced HBr does not function every bit a biocide, one half of the bromine
adds nothing to the strength of the biocidal species, HOBr. This invention disclosure
improves on the Goodenough et al. reference by means of a safer, easier, and more
economic process.
Much higher levels of available halogen for disinfection were attained using
the invention disclosed in this application, as shown in Table I below, by stabilizing
the sodium salt (NaOBr) generated during manufacture. As previously mentioned,
sodium hypobromite is unstable and therefore not commercially available. If a
stabilized form of NaOBr is proposed, the stabilization procedure must occur quickly
later NaOBr is fabricated. The method described in the Goodenough et al. reference could not attain
these increased bromine levels as the order of reagent addition described in the
reference was deemed not critical to the operability of the method. Since NaOBr is
synthesized by the following reaction, NaOCl + NaBr → NaOBr + NaCl, addition of
the stabilizer prior to bromide oxidation would not permit the formation of NaOBr.
When h2o is treated with many halogenated biocides, undesirable
halogenated organics tin be generated as by-products. These compounds are causing
increased environmental and health concerns. It is generally known that low
molecular weight halogenated organics are more easily biologically degraded than
college molecular weight species. However, the low molecular weight forms may be
more than toxic to aquatic and mammalian organisms. Differentiation of these halogenated
organics is costly, time consuming and requires the utilize of gas chromatography, high
performance liquid chromatography or gel permeation chromatography. Absorbable
Organic Element of group vii, "AOX", was chosen every bit a method of measuring the sum of
halogenated organic compounds without speciation. AOX is used equally an effluent
monitoring parameter of water or wastewater in Europe and North America. In the
United States, the Environmental Protection Agency ("EPA") is looking closely at
AOX discharge in the lurid and paper industry. An object of the present invention is
to provide a stable NaOBr solution that tin can be used to control microbial fouling with
minimal AOX generation. The problems associated with controlling AOX levels, existence a more recent developing environmental concern, have non been previously
resolved in the industry.
The The states EPA extrapolates some animate being carcinogenesis with the
presence of low bromate levels found in drinking water. Bromate may announced from
the ozonation of bromide-containing water raising some concerns in the drinking
h2o industry. Bromate may also exist formed by the disproportionation of
hypobromite. This reaction occurs at a greater rate in alkaline environments. Hence,
if bleach is added to a NaBr solution, the high pH environs could lead to the
undesirable production of bromate. One use of the nowadays invention, which was
previously unknown and is surprising, is to greatly minimize bromate formation by
stabilizing hypobromite when conditions are favorable for bromate product.
The petroleum industry experiences biological issues, including
microbiologically influenced corrosion, both localized and general, in oil field waters.
In addition, bacteria can plug the wellbore surface in waterflood injection wells. The
bacteria form slime plugs, reducing injectivity. Handling with stable bromine water
is a convenient method of dealing with these and similar problems.
It is an object of the present invention to provide a procedure whereby 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, yet which retain an improved capacity for oxidation and bactericidal activity. Another object of the nowadays invention is to provide a stable sodium
hypobromite solution in which the formation of AOX is minimized while providing improved microbial fouling control. Other objects and advantages of the present
invention volition become obvious from the following description thereof.
Summary of the Invention
The invention, according to one embodiment is a method for preparing a
stabilized aqueous brine or alkaline earth metal hypobromite solution. The method
comprises the steps of:
a. Mixing an aqueous solution of alkali or alkaline earth metal
hypochlorite having from most 5 per centum to virtually 70 percent available halogen every bit
chlorine with a water soluble bromide ion source;
b. Allowing the bromide ion source and the alkali or alkaline earth metal hypochlorite to react to form a 0.five to 70 percentage past weight aqueous solution of
unstabilized alkali or element of group ii hypobromite;
c. Calculation to the unstabilized solution of alkali or alkaline world metallic
hypobromite an aqueous solution of an alkali metallic sulfamate in a quantity to provide
a molar ratio of alkali metal sulfamate to brine or element of group i earth metal hypobromite is
from almost 0.five to nigh 7; and,
d. Recovering a stabilized aqueous alkali or alkaline earth metal
hypobromite solution.
Description of the Preferred Embodiments One apotheosis of the invention is a method for preparing a stabilized
aqueous brine or alkali metal globe metal hypobromite solution. The method comprises
the steps of:
a. Mixing an aqueous solution of brine or element of group ii
hypochlorite having from about five pct to most 70 percent available halogen equally
chlorine with a water soluble bromide ion source;
b. Assuasive the bromide ion source and the alkali or element of group ii
hypochlorite to react to grade a 0.5 to 70 per centum by weight aqueous solution of
unstabilized alkali or alkaline earth metal hypobromite;
c. Calculation to the unstabilized solution of alkali or alkaline metal earth metallic
hypobromite an aqueous solution of an alkaline sulfamate in a quantity to provide
a molar ratio of alkaline metal sulfamate to alkali or alkaline earth metal hypobromite is
from about 0.five to about seven; and,
d. Recovering a stabilized aqueous alkali or alkaline earth metal
hypobromite solution.
The alkali or alkaline earth metal hypochlorite is selected from the grouping
consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite,
lithium hypochlorite, and calcium hypochlorite. The amount of hypochlorite used will
vary depending upon which hypochlorite salt is used.
The bromide ion source is selected from the grouping consisting of sodium
bromide, potassium bromide, lithium bromide, and hydrobromic acrid. As shown in the examples, in a more preferred embodiment, the alkali or element of group ii
hypochlorite is sodium hypochlorite, the bromide ion source is sodium bromide, and
the alkali or alkaline globe metal hypobromite is sodium hypobromite.
The aqueous solution of unstabilized brine or alkaline earth metal hypobromite
may contain from about 0.5 to nigh 70 percent by weight alkali or element of group i earth
metal hypobromite, more preferrably from nearly 1 to nearly 30 pct by weight
alkali or element of group ii hypobromite, and most preferrably from nearly 4 to about
15 pct by weight alkali or alkaline world metallic hypobromite.
The pH of the stabilized aqueous alkali or alkaline metal earth metallic hypobromite
solution is from about 8 to well-nigh 14 and more preferrably from about 11 to well-nigh 14.
The the molar ratio of the alkali metal sulfamate to the sodium hypobromite is
preferrably from about 0.5 to nigh seven, more preferrably from about 0.5 to about 4, and
most preferrably from about 0.5 to about 2.
Some other embodiment of the invention is a stabilized aqueous solution of an
alkali or alkaline world metal hypobromite which is prepared by the steps of:
a. Mixing an aqueous solution of alkali or alkaline earth metal
hypochlorite having from near 5 percentage to about seventy percentage bachelor element of group vii as
chlorine with a water soluble bromide ion source;
b. Assuasive the bromide ion source and the alkali or element of group i earth metal
hypochlorite to react to form a 0.v to 30 pct past weight aqueous solution of
unstabilized alkali or alkaline world metal hypobromite; c. Adding to the unstabilized solution of alkali or element of group ii
hypobromite an aqueous solution of an brine metal sulfamate in a quantity to provide
a molar ratio of brine metal sulfamate to alkali or alkaline earth metal hypobromite is
from about 0.5 to near vii; and,
d. Recovering a stabilized aqueous alkali or element of group i world metal
hypobromite solution.
The alkali or alkali metal world metallic hypochlorite is selected from the grouping
consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite,
lithium hypochlorite, and calcium hypochlorite. The amount of hypochlorite used will
vary depending upon 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 or alkaline earth metal
hypochlorite is sodium hypochlorite, the bromide ion source is sodium bromide, and
the alkali or element of group i world metallic hypobromite is sodium hypobromite.
The aqueous solution of unstabilized alkali or alkaline earth metal hypobromite
may contain from about 0.5 to about lxx percent by weight alkali or alkaline earth
metallic hypobromite, more preferrably from about 1 to about 30 percent by weight
alkali or alkaline earth metal hypobromite, and most preferrably from about iv to most
15 percentage past weight alkali or alkali metal earth metal hypobromite. The pH of the stabilized aqueous alkali or alkaline metal earth metal hypobromite
solution is from about 8 to well-nigh 14 and more preferrably from well-nigh 11 to about 14.
The the molar ratio of the alkali metallic sulfamate to the sodium hypobromite is
preferrably from nearly 0.5 to about vii, more preferrably from near 0.5 to most 4, and
about preferrably from virtually 0.5 to about ii.
The invention can be used in an industrial water system. Such water systems
would contain from nigh 0.05 to well-nigh thou ppm, more preferably from about 0.05 to
near x ppm, and near preferably from well-nigh 0.i to almost 5 ppm of the stabilized
aqueous solution of an alkali or alkaline earth metal hypobromite.
The invention can be used in the laundering of soiled garments where the
soiled garments are washed in an aqueous media, such every bit h2o, containing a detergent
and a bleaching agent. The stabilized aqueous solution of an alkali or alkaline globe
metal hypobromite tin be used as the bleaching agent.
The invention tin also be used in the manufacture of cellulosic materials in
which cellulosic fibers are bleached with an oxidizing agent. The stabilized aqueous
solution of an brine or element of group ii hypobromite can be used as the oxidizing agent.
The invention tin be used in the control of microbiofouling in a recreational
water system in which an oxidizing agent is added to control microbiofouling. The
stabilized aqueous solution of an alkali or alkaline earth metal hypobromite tin be
used every bit the oxidizing amanuensis. The invention can be used in the control of microbiofouling occurring on the
surfaces of equipment in contact with produced oil field waters. An anti-
microbiofouling effective amount of stabilized aqueous solution of an brine or
alkaline world metal hypobromite can be added to the produced oil field waters.
The invention can besides be used in the control of microbiofouling in aqueous
systems. An effective anti-microbiofouling corporeality of stablized aqueous solution of
an brine or element of group ii hypobromite can be added to aqueous systems.
In another apotheosis, the invention is a method of preventing
microbiofouling on the surfaces of equipment in contact with in an industrial h2o
system. The method comprises adding to the aqueous system an anti-
microbiologically effective corporeality of a stabilized sodium hypobromite solution. The
stabilized sodium hypobromite solution is prepared by the steps of:
a. Mixing an aqueous solution of sodium hypochlorite having from about
v percent to about 30 percentage available halogen (as chlorine) with sodium bromide;
b. Allowing the sodium bromide and the sodium hypochlorite to react to
form a 0.5 to xxx percent by weight aqueous solution of unstabilized sodium
hypobromite;
c. Adding to the unstabilized solution of sodium hypobromite an aqueous
solution of an alkali metal sulfamate in a quantity to provide a molar ratio of alkali
metal sulfamate to sodium hypobromite of from about 0.5 to well-nigh 7; and,
d. Recovering a stabilized aqueous sodium hypobromite solution. The industrial water systems include cooling water systems, cooling ponds,
reservoirs, sweetwater applications, decorative fountains, pasteurizers, evaporative
condensors, hydrostatic sterilizers and retorts, gas scrubber systems, and air washer
systems.
Some other embodiment of the invention is a method for preparing a stabilized
aqueous alkali or alkaline earth metal hypobromite solution when the level of
available element of group vii every bit chlorine is beneath about 5 per centum. The method comprises the
steps of:
a. Mixing an aqueous solution of alkali or element of group ii
hypochlorite [wherein the percent of available halogen (equally chlorine) is less than about
5] with a water soluble bromide ion source;
b. Allowing the bromide ion source and the brine or alkaline earth metal
hypochlorite to react to form a 0.5 to 5 percent by weight aqueous solution of
unstabilized alkali or alkaline world metallic hypobromite;
c. Adding to the unstabilized solution of alkali or element of group ii
hypobromite an aqueous solution of an alkaline sulfamate having a temperature of
at to the lowest degree 50 °C in a quantity to provide a molar ratio of alkali metallic sulfamate to alkali
or alkaline earth metal hypobromite is from virtually 0.5 to nearly vii; and,
d. Recovering a stabilized aqueous alkali or alkaline earth metal
hypobromite solution. When the level of available element of group vii as chlorine is beneath about five percent, the
amount of h2o in which the stabilizer, the alkali metal sulfamate, is dissolved into
must be decreased. At this bespeak, the corporeality of water is depression enough that the alkali
metal sulfamate is only sparingly soluble in the water. Therefore, the temperature of
the aqueous alkali metal sulfamate solution must be maintained higher up 50 °C to keep
the alkali metallic sulfamate in solution until the solution is added to the aqueous
solution of unstablized sodium hypobromite. Once mixed with the sodium
hypobromite solution, solubility is no longer a business organization, and the resulting stabilized
sodium hypobromite solution solution does not need to be maintained higher up 50 °C.
The brine or element of group ii hypochlorite is selected from the group
consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite,
lithium hypochlorite, and calcium hypochlorite. The amount of hypochlorite used volition
vary depending upon which of the hypochlorite is used.
The bromide ion source is selected from the group consisting of sodium
bromide, potassium bromide, lithium bromide, and hydrobromic acrid. Equally shown in
the examples, in a more preferred apotheosis, the alkali or element of group ii
hypochlorite is sodium hypochlorite, the bromide ion source is sodium bromide, and
the alkali or alkaline world metallic hypobromite is sodium hypobromite.
The aqueous solution of unstabilized alkali or alkaline earth metal hypobromite
may contain from about 0.5 to nearly lxx percent by weight alkali or alkaline metal globe
metal hypobromite, more preferrably from well-nigh one to about xxx pct past weight alkali or alkaline earth metal hypobromite, and most preferrably from almost 4 to about 15 percent past weight alkali or alkaline earth metal hypobromite.
The pH of the stabilized aqueous alkali or element of group ii hypobromite
solution is from about viii to nigh fourteen and more than preferrably from well-nigh xi to about 14.
The the molar ratio of the alkali metal sulfamate to the sodium hypobromite is
preferrably from well-nigh 0.v to about 7, more preferrably from well-nigh 0.v to about 4, and
near preferrably from near 0.5 to about two.
Another embodiment of the invention is a stabilized aqueous solution of an
alkali or alkaline earth metal hypobromite which is prepared by the steps of:
a. Mixing an aqueous solution of alkali or alkaline earth metal
hypochlorite [wherein the percent of available halogen (as chlorine) is less than about
5] with a water soluble bromide ion source;
b. Allowing the bromide ion source and the alkali or element of group ii
hypochlorite to react to form a 0.5 to 5 percent by weight aqueous solution of
unstabilized brine or alkaline earth metal hypobromite;
c. Adding to the unstabilized solution of alkali or alkaline world metal
hypobromite an aqueous solution of an alkali metal sulfamate having a temperature of
at least l °C in a quantity to provide a molar ratio of element of group i sulfamate to alkali
or alkaline earth metal hypobromite is from about 0.5 to about 7; and,
d. Recovering a stabilized aqueous alkali or alkaline earth metal
hypobromite solution. As discussed in a higher place, when the level of available halogen as chlorine is beneath
about 5 percent, the corporeality of h2o in which the stabilizer, the brine metal
sulfamate, is dissolved into must be decreased. At this point, the corporeality of water is
low that the alkali metal sulfamate is only sparingly soluble in the water. Therefore,
the temperature of the aqueous alkali metal sulfamate solution must exist maintained
above 50 °C to keep the alkali metal sulfamate in solution until the solution is added
to the aqueous solution of unstablized sodium hypobromite. One time mixed with the
sodium hypobromite solution, solubility is no longer a business concern, and the resulting
stabilized sodium hypobromite solution solution does not need to be maintained higher up
l °C.
The alkali or alkaline earth metal hypochlorite is selected from the group
consisting of sodium hypochlorite, potassium hypochlorite, magnesium hypochlorite,
lithium hypochlorite, and calcium hypochlorite. The corporeality of hypochlorite used will
vary depending upon which of the hypochlorite is used.
The bromide ion source is selected from the group consisting of sodium
bromide, potassium bromide, lithium bromide, and hydrobromic acrid. Every bit shown in
the examples, in a more preferred embodiment, the brine or alkaline globe metal
hypochlorite is sodium hypochlorite, the bromide ion source is sodium bromide, and
the alkali or alkaline earth metal hypobromite is sodium hypobromite.
The aqueous solution of unstabilized alkali or alkaline earth metallic hypobromite
may comprise from about 0.5 to nearly 70 pct past weight alkali or element of group i earth metal hypobromite, more preferrably from about one to well-nigh xxx percentage by weight
alkali or element of group ii hypobromite, and almost preferrably from about iv to about
15 percent past weight alkali or alkaline earth metal hypobromite.
The pH of the stabilized aqueous alkali or alkaline metal earth metal hypobromite
solution is from well-nigh 8 to near fourteen and more than preferrably from about 11 to about 14.
The the molar ratio of the alkaline sulfamate to the sodium hypobromite is
preferrably from about 0.5 to most 7, more than preferrably from about 0.5 to about 4, and
nigh preferrably from virtually 0.5 to almost ii.
In another apotheosis, the invention is a method of preventing
microbiofouling on the surfaces of equipment in contact with in an industrial h2o
system. The method comprises adding to the aqueous arrangement an anti-
microbiologically effective amount of a stabilized sodium hypobromite solution. The
stabilized sodium hypobromite solution is prepared past the steps of:
a. Mixing an aqueous solution of sodium hypochlorite [wherein the
pct of available halogen (as chlorine) is less than nearly 5] with sodium bromide;
b. Allowing the sodium bromide and the sodium hypochlorite to react to
form a 0.5 to v percentage past weight aqueous solution of unstabilized sodium
hypobromite;
c. Adding to the unstabilized solution of sodium hypobromite an aqueous
solution of an element of group i sulfamate having a temperature of at least 50 °C in a quantity to provide a molar ratio of brine metal sulfamate to sodium hypobromite of
from about 0.5 to near 7; and,
d. Recovering a stabilized aqueous sodium hypobromite solution.
As discussed above, when the level of available halogen as chlorine is below
about 5 per centum, the corporeality of h2o in which the stabilizer, the alkaline metal
sulfamate, is dissolved into must exist decreased. At this point, the amount of water is
low that the alkali metal sulfamate is only sparingly soluble in the h2o. Therefore,
the temperature of the aqueous alkali metallic sulfamate solution must be maintained at
at least 50 °C to keep the alkali metal sulfamate in solution until the solution is added
to the aqueous solution of unstablized sodium hypobromite. Once mixed with the sodium hypobromite solution, solubility is no longer a business concern, and the resulting
stabilized sodium hypobromite solution solution does non need to be maintained at at
to the lowest degree 50 °C.
Yet another embodiment of the application provides for the use of an
culling stabilizer to the aqueous alkali metal sulfamate. The contemplated
stabilizer may be selected from the group consisting of acid amide derivatives of:
carbonic acids, hydrogen cyanide, carboxylic acids, amino acids, sulfuric acids,
phosphoric acids and boric acids. More specifically, the preferred stabilizers are
selected from the group consisting of urea, thiourea, creatinine, cyanuric acids, alkyl
hydantoins, mono or di ethanolamine, organic sulfonamides, biuret, sulfamic acid,
organic sulfamates and melamine. All of the stabilizers are compounds having an Northward- H or NH2 group adjacent to an electron withdrawing functional grouping such as C=O,
SO, P=O, or B=O.
This invention provides several differences over the known art, including a
specific club of addition in the manufacturing process whereby a stabilized sodium
hypobromite solution is produced having improved stability, non-volatility, reduced
bromate and AOX formation, improved microbiofouling control, and an increased free
halogen residue in cooling water.
The stability of the stabilized hypobromite solution, every bit compared to the
stabilized bromine disclosed in the Goodenough et al. reference and unstabilized
sodium hypobromite in Table I, is greatly increased. Based on the surprising
increased stability of the stabilized sodium hypobromite of this invention, it is
credible that the guild of improver in the procedure of manufacture is disquisitional.
The chemical mechanism for halogen biocide stabilization past sulfamic acid
has been proposed as follows:
HO-10 + H-NH-SO3H «-» X-NH-SO3H + H,O
(Xfree) (^stable)
When 10 is Cl, the reaction applies to stabilized chlorine. When X is Br, the reaction applies to stabilized bromine.
The degree of stabilization is expressed as the concentration ratio of Xstabie to
Xfree. The Xgratuitous concentration of the stabilized bromine was detectable while the
concentration of the Xfree for stabilized chlorine was not. It was concluded that the
chlorine in the stabilized chlorine was completely stabilized while the bromine in the
stabilized bromine exists in both complimentary and stabilized forms. This contributes in role to
the increased antimicrobial backdrop of stabilized NaOBr over stabilized NaOCl
which will be described in more detail in Case 3.
Absorbable organic halogen (AOX) is an important environmental parameter
peculiarly in Europe. AOX can form from the reaction of some halogenated
compounds with organics. The minimization of AOX past stabilizing NaOBr is a
surprising benefit described in this disclosure.
Pathway A: AOX germination past HOX
HO-X + R-H <→ Ten-R + H2O
Where R-H can be the organic contaminants in cooling water or biomacromolecules
and 10-R is measured as AOX.
Pathway B:
X-NH-SO3H + R-H → R-NH-SO3H + HX
This stabilized halogen reaction generates no X-R (AOX) every bit in Pathway A. When free
chlorine (HOC1) or free bromine (HOBr) is used, AOX will be formed in accordance with the mechanism described past Pathway A. When stabilized chlorine is used as a biocide, only Pathway B is possible
because no free HOCl exists in the system. Thus, no or very low AOX will be formed
using this product (encounter Tabular array II below).
When stabilized bromine is used, both costless and stabilized bromine forms
coexist. Thus, both pathways A and B keep and consequence in some AOX germination.
However, the amount of AOX will be far less than when all of the halogen is in the
form of free bromine (HOBr).
Evidently, the proposed mechanism explains the crusade of AOX reduction due
to the utilise of stabilized halogen biocides. The machinery should be applicable to
other stabilized halogen products when ammonia, amines or amides are used equally the
stabilizing agents.
In society to reduce the AOX germination by a stabilized halogen biocide, it is
preferable to select strong stabilizing agents then that Pathway B can dominate.
Withal, the drawback to a very stable halogenated compound is the more often than not
decreased oxidation ability that, in most cases, is directly correlated to its biocidal
efficacy. Testing has shown that stabilized bromine is much more than effective equally a
biocide than stabilized chlorine. Therefore, to reduce the AOX formation and at the
same time maintain the chemical compound's biocidal efficacy requires a well balanced
selection of the stabilizing agent. The post-obit examples are presented to describe preferred embodiments and
utilities of the invention and are not meant to limit the invention unless otherwise
stated in the claims appended hereto.
Example ane :
Preparation of Stabilized Sodium Hypobromite with a Critical Lodge of Addition
In order to demonstrate the constancy of stabilized NaOBr, solutions of sodium
hypochlorite and sodium bromide were mixed forming NaOBr then stabilized with
sodium sulfamate as described beneath. Sodium hypochlorite solution was diluted in
need-free h2o. This diluted solution was titrated by the DPD-FAS method. The
available chlorine level present in the original solution was determined to exist 15
percent. 42.4 grams of the not bad NaOCl solution were added to twenty.five grams of a 45
percent NaBr solution. This reaction forms unstabilized NaOBr. The stabilization
solution was formulated with 9.6 grams of sulfamic acid, fourteen grams of h2o, and 13.2
grams of 50 per centum sodium hydroxide. The stabilization solution is and so added with
stirring to the NaOBr. The order of add-on is critical in this process which differs
from the Goodenough et al. reference. For instance, if the stabilizer was added to
NaOCl prior to NaBr introduction, the bromide would not be oxidized to hypobromite.
Likewise, bromine solutions prepared in the manner referenced to a higher place gave more stable
oxidizing species than the prior art. Bromine solutions stabilized equally explained in the
Goodenough et al. reference exhibited a decrease in halogen action from an initial
concentration of 1 percent to 0.77 percent later on fourteen days representing an agile
ingredient loss of 23 pct. The stabilization procedure described here improved on the prior fine art as the decline of agile ingredient was but i percentage later on 84 days (encounter
Table I above). An unstabilized NaOBr solution prepared in an similar process past
replacing sulfamic acid with distilled water lost 94 percent bachelor halogen during
the same period.
Example 2:
Less AOX is Formed in Stabilized Halogen Solutions
AOX is a generic class of compounds which includes all organic molecules
containing halogen. Limits for AOX discharge from cooling water systems have
already been established in some European countries. To simulate AOX germination
during stabilized and unstabilized sodium hypobromite activity in cooling water, a
mixed bacterial civilization typically establish in cooling h2o was cultivated in L-broth
overnight and the cells harvested past centrifugation. The cell pellet was washed with
synthetic cooling water (ninety ppm calcium, 50 ppm magnesium, one ten ppm "Grand"
alkalinity, pH 8.0 -8.2) twice to remove the remaining organic medium. Cells were
then resuspended into an equal book of cooling water. A capped dark bottle served
equally the reactor. Synthetic cooling water was added to the bottle followed by the
washed bacterial stock yielding approximately 10 cells/ml. Stabilized NaOBr or
unstabilized NaOBr was dosed into this bacterial suspension at a final concentration of
i, two, 3, or 4 ppm full halogen (as chlorine). Headspace in the canteen was minimized
to avoid the evaporative loss of halogenated organics and the solution stirred for 24
hours to simulate a typical cooling arrangement. Immediately earlier AOX assay, the sample was acidified to pH 2.0 with concentrated nitric acid. A Mitsubishi TOX-10
Analyzer was used according to U.s.a. EPA Method 9020 to measure the AOX
concentration in the samples. Ultrapure water was used for the preparation of all
reagents and standard solutions to prevent any contamination. The amounts of AOX
formed in each such treatment is shown in Table II below. Cooling water with
stabilized NaOBr formed less AOX than treatments using unstabilized NaOBr at
equivalent halogen concentrations. Linear regressions were performed on both sets of
data to obtain linear-fit equations shown below for both stabilized and unstabilized
NaOBr:
Stabilized NaOBr: AOX (ppb) = 23.3 Ten Dose (ppm)
Unstabilized NaOBr: AOX (ppb) = 53.9 10 Dose (ppm)
Testing also showed that stabilization of NaOCl reduced AOX generation in
cooling water dosed with two ppm full balance (see Table II).
Instance 3:
Antibacterial Activity of Stabilized Sodium Hypobromite Freshly prepared solutions of stabilized and unstabilized sodium hypobromite
were diluted then added to cooling water in order to achieve a one ppm gratis halogen
residual (as chlorine). Sodium hypochlorite was stabilized in the aforementioned mode as
described for NaOBr in Example One with the exception that NaBr was directly
replaced with distilled water. Stabilized and unstabilized sodium hypochlorite were
diluted then added to cooling h2o at a final concentration of ane ppm gratuitous element of group vii
residual (every bit chlorine). The volumes of all solutions needed to achieve a one ppm free
halogen remainder (as chlorine) was recorded. Following vi and 21 days of dark storage,
identical dilutions of stabilized and unstabilized sodium hypohalite solutions were
prepared and the volume originally required for a one ppm gratuitous element of group vii residual (as
chlorine) was added to cooling h2o containing approximately 10 Pseudomonas
aeruginosa cells / mL. Aliquots were extracted at 10 and 30 minutes into cooling
water dilution blanks containing a halogen neutralizer (0.05 percent Na2Due south2O3) then
enumerated on tryptone glucose extract agar. Stabilized NaOBr retained its
antibacterial activity subsequently storage while the unstabilized grade lost its efficacy against
Pseudomonas aeruginosa (see Tabular array III below). The results were even more dramatic
as the storage catamenia increased. This effect was likely due to the disproportionation of
the unstable hypobromite ion into the not-biocidal species bromide and bromate.
Surprisingly, NaOCl stabilized in the aforementioned fashion as NaOBr was insufficiently
ineffective under the conditions tested (Table 3).
Example iv:
Depression of Bromate Germination Following Stabilization of Sodium Hypobromite
Hypohalite ions are known to disproportionate into halate and halide nether
alkaline conditions. Halate ions are undesirable degradants being suspect carcinogens
and are nether consideration for governmental regulation. The reaction of NaBr with
NaOCl can yield significant amounts of bromate in elevated pH environments.
Surprisingly, the stabilization of NaOBr with sodium sulfamate greatly minimized
bromate formation (run across Tabular array 4 beneath). Stabilized and unstabilized sodium
hypobromite solutions were prepared as described in Case Ane. These solutions
were stored in the night at room temperature during the grade of the study. Eight
month former samples of stabilized and unstabilized NaOBr, both maintained at pH 14, a status suitable for bromate formation, were assayed for bromate. A Dionex 4000
serial gradient ion chromatography system equipped with AG9-SC/AS9-SC columns
and a conductivity detector was used to measure the bromate concentration in the
samples. The chromatograph was operated according to a method currently under
investigation past the EPA for the analysis of bromate in ozonated drinking water.
Purified water from an Interlake Water Systems deionization arrangement was used for the
preparation of all reagents and standard solutions to preclude contagion.
Equally noted above, the pH of these solutions was high which favors bromate
formation. Withal, NaOCl, which contains significant amounts of NaOH, is
typically diluted with organization water prior to the introduction of the bromide species in
virtually industrial applications. The pH of this diluted arrangement would be lower than the
great NaOCl / NaBr conception described to a higher place theoretically minimizing bromate
formation. The available chlorine in a NaOCl sample diluted (1 : 100) with distilled
water was titrated by the DPD-FAS method. A solution of 45 percent sodium bromide
was added to the dilute NaOCl at a molar ratio of i Cl2 : 1 Br" forming NaOBr. This
reaction proceeded for thirty minutes. Then, appropriate volumes of this dilute NaOBr
solution were added to cooling water (pH viii.3) giving total available halogen levels of 1, 2, 3, and four ppm (as Cl2) as determined by the DPD-FAS method. Similarly, a
dilution of stabilized sodium hypobromite (1 :100) was made in distilled water. Dilute
stabilized NaOBr was added to cooling water (pH 8.3) giving total available element of group vii
levels of i, 2, 3, and 4 ppm (as Cltwo) as determined by the DPD-FAS method. Bromate
analysis then proceeded in the manner described above. Bromate was not detected in
whatsoever of the cooling water samples dosed with either stabilized or unstabilized dilute
NaOBr at typical utilise concentrations. These results signify the prophylactic factor for
bromate congenital into the stabilized sodium hypobromite formulation as well as the
industrial in situ oxidation of NaBr with dilute NaOCl.
Example 5:
Apply of Stabilized NaOBr Increased the Percentage of Free Residual in a
Recirculating Cooling Water System Compared to Other Stabilized Halogen
Compounds
A major drawback to some commercial stabilized chlorine products for
industrial water treatment is the low pct of complimentary chlorine residuum delivered to
the h2o organisation. This consequence is due to the strength of the chemical bail betwixt the
stabilizer, unremarkably a nitrogenous compound, and chlorine. Chloramines, ie. combined
chlorine, are weaker microbicides than gratuitous chlorine. Withal, bromamines are
considered to be nearly as effective confronting microorganisms as gratis bromine. Thus, it
is essential to accept a high percentage of the full available halogen in the gratis grade
when chlorine products are employed. Conversely, this phenomenon is not every bit crucial when employing stabilized NaOBr. A commercial heating, ventilation and air
conditioning ("HVAC") cooling system was sequentially treated with stabilized
NaOCl, a bromochloroalkylhydantoin, and finally stabilized NaOBr. In that location was a low
percentage of free chlorine relative to total bachelor element of group vii present in the stabilized
NaOCl treated system (see Table V beneath). A lower percentage of free halogen was
measured when a dissimilar stabilization system, an alkylhydantoin, was employed with
bromine and chlorine (see Tabular array V below). However, when stabilized NaOBr was fed
into this organisation, the percentage of free available halogen relative to the total residual
measured quickly increased (encounter Table V below). These phenomena imply that less
stabilized NaOBr is required to obtain a gratuitous available halogen residual than the
equivalent amount of stabilized NaOCl.
Example Six:
Stabilization of Sodium Hypobromite Reduces Volatility
If a biocide is highly volatile, its functioning may be adversely affected. For
example, the biocide may flash off in the highly aerated conditions of a cooling tower
or an air washer. This would lower the biocide concentration in the cooling water wasting the production. Element of group vii volatility besides leads to vapor-phase corrosion of
susceptible equipment surfaces. In addition, element of group vii volatility may cause worker
discomfort due to the "swimming puddle" odor. Thus, the need for an efficacious
oxidizing biocide with depression volatility is axiomatic.
Concentrated solutions of either NaOCl, NaOBr, or stabilized NaOBr were
added to a beaker. Halogen vapors were detected from the NaOCl and NaOBr
solutions. No odors were noticed from the stabilized NaOBr. This is an improvement
over existing products by minimizing halogen odors in product storage areas.
Bleach, NaOCl, is not unremarkably used in air washer systems due to some of
the reasons listed above. In one case an effective microbial control dose is achieved, the
halogen odor may be and then overwhelming that workers would not be able to comfortably
operate in the treated areas. The low volatilization of stabilized NaOBr overcomes
this drawback. Stabilized sodium hypobromite was added at elevated employ
concentrations to two textile manufactory air washers in order to investigate its volatility.
Then the air was monitored throughout the mill. A Sensidyne air monitoring device
outfitted with halogen detection tubes was used to instantaneously detect halogen in
the air. The lower detection limit was fifty ppb which is below the Threshold Limit
Value-Brusk Term Exposure Limit for bromine as established past OSHA. In add-on,
halogen badges were placed throughout textile mills in order to detect halogen vapors
over extended periods of fourth dimension. Neither monitoring system detected any halogen
present in the air following the elevated stabilized NaOBr dose. No element of group vii odors were encountered in either the air washer unit or the render air. The microbial
population was enumerated before and afterward stabilized NaOBr add-on. The microbial
population following dosing was reduced by greater than one order of magnitude.
This example demonstrates the utility of stabilized sodium hypobromite in controlling
the bacterial population while adding no halogen odor to the organisation area.
Changes can be made in the composition, operation and organization of the
method of the present invention described herein without departing from the concept
and scope of the invention as defined in the post-obit claims:
Source: https://patents.google.com/patent/WO1999006320A1/en
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