 |
Description  |
|
|
BACKGROUND OF THE INVENTION
It has heretofore been known to the art of water treatment to effect
disinfection and reduction in the bacterial content thereof to treat
contaminated water, for drinking purposes, for use in swimming pools and
for other purposes and in other environments, by passing the same through
strong base polyhalide bacteriocidal anion-exchange resins in which the
exchange sites of said anion-exchange resins have attached to a
predominant number of such sites polyhalide anions, notably triiodide
ions, satisfying certain formulae conditions. After suitable preparations
of such polyhalide bacteriocidal resins, the contaminated or possibly
contaminated water to be treated is passed therethrough to effect
decontamination or disinfection thereof.
Among the prior art references which disclose procedures following the
approaches which have been referred to above are U.S. Pat. Nos. 3,817,860;
4,187,183; 4,190,529; and published articles appearing in Proceedings
Second World Congress, International Water Resources Association, New
Delhi, India, December, 1975, Vol. II, pp. 53-59; and Applied
Microbiology, Nov. 1970, Vol. 20, No. 5, pp. 720-722.
In U.S. Pat. No. 4,187,183, it has been suggested, generally, that, in the
production of the mixed-form polyhalide bacteriocidal resin, there be
added to a strong base anion exchange resin a slurry mixture of elemental
iodine, interhalogen, or bromine and an appropriate amount of an iodide or
bromide salt, and it is pointed out that the preferred amount of iodide or
bromide is less than the stoichiometric amount required for complete
loading of triiodide or tribromide ions on all available resin sites, and
the X.sub.2 :X.sup.- ratio is always greater than one. It points out,
further, that iodine or bromine liberated from such bacteriocidal resins
during water treatment by the passage of water therethrough may be readily
scavenged from said treated water by an unloaded anion-exchange resin, and
the hypohalous acid which is formed can be removed by additional treatment
with activated charcoal. In the description of the preferred embodiment of
the invention of said U.S. Pat. No. 4,187,183, the strong base
anion-exchange resin, in chloride or sulfate form, is reacted with a
mixture of iodine and a pre-selected amount of iodide salt to form a
polyhalide resin product but, while the use of iodine and an iodide salt
is thereafter discussed as indicative of the particularly advantageous
embodiment of the invention of said patent, bromide or an appropriate
interhalogen may be substituted for iodine, and that a bromide salt may be
substituted for the iodide salt to produce other resins which are within
the scope of the invention of said patent. The particular results obtained
and reported are, however, as noted above, directed to the use of iodine
and potassium iodide in the production of the polyhalide bacteriocidal
resin, and the formulae stated in the claims of said patent are likewise
defined in relation to the exchange sites and related facets in terms of
the use of iodine and potassium iodide in the production of the polyhalide
bacteriocidal resins. Similar disclosures and reports of results appear in
U.S. Pat. No. 4,190,529.
The earlier U.S. Pat. No. 3,817,860 also discloses the preparation and
utilization of a strongly basic anion-exchange resin containing combined
triiodide in insolubilized form in said resin, and the disinfection of
contaminated or bacteria-containing water by passage through a bed of a
porous granular material or beads comprising said previously prepared
triiodide strongly basic anion-exchange resin. The aforesaid U.S. Pat. No.
3,817,860 also refers to an earlier U.S. Pat. No. 3,316,173 in which water
is treated with bromine and wherein a strong base anion-exchange resin is
used as a source of diatomic or elemental bromine, the bromine being
eluted from the resin to form a relatively concentrated aqueous solution,
which is subsequently mixed with a larger volume of water, such as the
water in a swimming pool, to provide a bacteriocidal concentration of
bromine. In accordance with the teachings of U.S. Pat. No. 3,316,173, the
bromine is eluted from the resin in concentration of from 10 to 10,000
p.p.m., which is stated to be far above physiologically acceptable levels
of bromine in water for human consumption.
Still another prior art disclosure dealing with the treatment of water to
effect disinfection thereof or to control microorganisms therein in U.S.
Pat. No. 3,462,363. This patent refers to U.S. Pat. No. 3,316,173 and
points out that, because the residual halogen picked up by water treated
by strong base quaternary ammonium anion-exchange resins in polybromide
form, prepared pursuant to the aforementioned U.S. Pat. No. 3,316,173, or
in strong base quaternary ammonium anion-exchange resins in other
previously known polyhalide forms, is unduly high, as is directly
indicated in U.S. Pat. No. 3,462,363, to effect substantial reduction in
the content of residual halogen in the finally treated water, said U.S.
Pat. No. 3,462,363 finds it necessary to resort to a two-step or tandem
treatment with a strong base quaternary ammonium anion-exchange resin in a
polyhalide form, namely, the scavenging resin.
As will be seen below, in light of the description of my present invention,
and the purposes and objects of my invention, such are readily
distinguished from the disclosures in the aformentioned patents. As will
also be pointed out below, the teaching and disclosures of the
aforementioned U.S. Pat. Nos. 3,817,860; 4,187,183; 4,190,529; 3,316,173
and 3,462,363, as well as the published articles referred to above which
deal with experimental work related to U.S. Pat. No. 3,817,860, fail to
provide any teachings of my present invention and the advantages that are
achieved thereby over the disclosures of said prior art references taken
singly or as a whole.
By way of further background information, relevant to my present invention,
it has been known, generally speaking, that under certain limited
conditions, while the U.S. Environmental Protection Agency (USEPA)
approves of the use of iodine and also of bromine as drinking water
disinfectants, up to the present time, policy statements in reference
thereto which issued in 1973 by USEPA have remained fundamentally
unchanged. Chlorination of water is regarded as a safe procedure and it
is, and long has been, in common usage for public water supply as well as
for general use. On the other hand, in the case of iodinated or brominated
water for human usage for drinking purposes, the policy promulgated by
USEPA in 1973 indicates that the presence of iodine or bromine in
emergency situations in water supplies would be considered tolerable or
not harmful where the consumption of iodinated or brominated water is
brief, for instance, of the order of not more than about 3 weeks, and
where the iodine or bromine content of the water is in the range of about
0.5 to 1.0 mg. of iodine or bromine per liter. In general, however, iodine
disinfection of public water supplies is not recommended because of
possible adverse effects on individuals with impaired thyroid function or
on the unborn child. In any event, so fas as I am at present aware, no
disinfecting systems heretofore have been developed, involving the use of
iodine or bromine, which are acceptable and approved for long term or
in-line usage for disinfecting water because the effluent from all known
systems, of which I am aware, contains an unacceptably high level of
residual iodine/iodide or bromine/bromide. Thus, while the disclosures of
such prior patents as those referred to above, indicate or purport to meet
USEPA conditions for long term usage, so far as I am aware they possess
the deficiency that the effluents from the triiodide or polybromide
strongly basic anion-exchange resins thereof still contain sufficient
residual iodine/iodide or bromine which precludes their acceptability for
use in public water supply systems, particularly where the treated water
is intended for long term or in-line drinking purposes.
The ultimate design of an iodine or bromine bacteriocidal system would be a
demand mechanism, i.e. bacteriocidal materials are released only as
demanded by the presence of microorganisms in the water to be treated.
In the aforementioned U.S. Pat. Nos. 3,187,860; 4,187,183; 4,190,529, as
discussed, in part, above, as well as in U.S. Pat. No. 3,923,665, methods
are disclosed for making bacteriocidal resins and a formula is specified
in said U.S. Pat. Nos. 4,187,183 and 4,190,529 which provides conditions
to be satisfied for producing certain of such bacteriocidal resins.
Generally speaking, over and above what has heretofore been stated in
regard thereto, this formula centers around the use of potassium iodide
(KI) and elemental iodine (I.sub.2) to form "triiodide" ions that can be
attached to a synthetic ion exchange resin. This is accomplished by
preparing a stoichiometrically balanced solution of I.sub.2 in KI. The
resin is then stirred into the solution and allowed to react. The
aforesaid U.S. Pat. Nos. 4,187,183 and 4,190,529 claim that the
polyhalides, specifically triiodide, occupy certain resin sites as
follows:
a is I.sup.-.sub.3-
b is I.sup.-.sub.5
wherein:
a=0.4 to 0.8 of the exchange sites
b=0.1 to 0.3 of the exchange sites
a+b=a predominant number of the anion sites available for exhange and a+2
(b) equals or exceeds 1.0.
As has also previously been discussed above, reference is made in certain
of said patents for the need to use a bed of scavenger resin downstream of
the triiodide resin in order to cope with the relatively high levels of
iodine/iodide in the effluent from the system, the scavenger resin serving
to react with the excess iodine/iodide in order to remove it from water
streams.
THE PRESENT INVENTION
In accordance with my present invention, novel polyhalide bacteriocidal
strong base anion-exchange resins are produced which generate an effluent
with extremely low iodine and bromine contents, or, in other words, the
novel resins of my present invention are characterized by very low iodine
and bromine residuals and they are "demand" bacteriocidal materials which
rely solely on water contact with the resins to destroy microorganisms.
In the production of the novel polyhalide bacteriocidal resin compositions
of my invention, a strong base anion-exhange resin, generally in the form
of granules or beads, having anion-exchange sites, is advantageously
contacted in an aqueous medium containing a solution of elemental iodine
and water-soluble salts of iodine and of potassium bromide. While such
water-soluble iodide salts may be sodium iodide or ammonium iodide, it is
especially satisfactory to use potassium iodide. However, for the
effective practice of my invention I have found it to be essential to
utilize potassium bromide. Mixtures of the various water-soluble iodides
can be used but, again, potassium iodide is especially satisfactory, and
potassium bromide is essential.
The following examples are illustrative of the practice of my present
invention. It will be understood that various changes may be made therein
within the scope of the guiding principles and teachings disclosed herein,
without departing from the fundamentals of my invention, and the invention
is, therefore, not to be construed as being limited to said illustrative
examples.
EXAMPLE 1
22.75 pounds of elemental iodine, 9.9 pounds of potassium iodide and 1.98
pounds of potassium bromide are mixed together. Then 4.94 pounds of
deionized water are added and the resulting solution is mixed at room
temperature for about 60 minutes while 1 cubic foot of a damp strong base
anion-exchange resin, desirably Ionac ASB-1 in the chloride form, in the
conventional form of beads or granules, is added during the mixing step.
Upon completion of the mixing step, the mixture is allowed to stand
quiescently for about 16 to 20 hours. Washing is then carried out with
about 4 to 5 gallon volumes of deionized water. The foregoing ratio of
weights is based upon the milliequivalent wet exchange capacity of the
resin. The resin used in this example is one having 1.44 meq/ml. This
formulation results in a polyhalide complex of iodine and bromine ions.
In the foregoing Example 1, the ratios of the ingredients utilized in the
preparation of the novel polyhalide bacteriocidal strong base
anion-exchange resins made and utilized in accordance with my present
invention are as follows:
______________________________________
Ratios
______________________________________
Iodine 0.517 22.75 p 220 g
KBr 0.045 1.98 p 20 g
KI 0.225 9.90 p 100 g
H.sub.2 O 0.071 4.94 p 50 g
Starting Resin
1 1 Cft 0.6 Liter
______________________________________
Notes:
p = pounds
L = liters
1 = Cft Resin weight 44 pounds
0.6 L Resin weighs 425 grams
EXAMPLES 2-14, inclusive
The following Examples are carried out in the manner described in Example
1, using the herein stated proportions of the specified ingredients:
______________________________________
2 3 4 5 6 7
______________________________________
Iodine 230 g 230 g 200 g
210 g 220 g
220 g
KBr 20 g 10 g 20 g
20 g 20 g
30 g
KI 120 g 110 g 100 g
100 g 100 g
100 g
H.sub.2 O
50 g 50 g 50 g
50 g 50 g
50 g
Starting 0.6 L 0.6 L 0.6 L
0.6 L 0.6 L
0.6 L
Resin
______________________________________
8 9 10 11 12 13 14
______________________________________
Iodine 215 g 225 g 220 g 220 g
220 g 220 g
220 g
KBr 20 g 20 g 10 g 15 g
20 g 25 g
20 g
KI 100 g 100 g 110 g 100 g
100 g 100 g
90 g
H.sub.2 O
50 g 50 g 50 g 50 g
60 g 50 g
50 g
Starting
0.6 L 0.6 L 0.6 L 0.6 L
0.6 L 0.6 L
0.6 L
Resin
______________________________________
Notes:
1 Cft Resin weighs 44 pounds
0.6 L Resin weighs 425 grams
It will be noted, as pointed out in Example 1, as well as in the additional
working Examples, that the ingredients utilized in the preparation of the
polyhalide bacteriocidal anion-exchange resins of the present invention
are employed in certain ratios by weight to each other. The maintenance of
certain ratios of the materials to each other is important in order to
achieve the significant improvements which are obtained in accordance with
my invention.
Generally speaking, the materials for the production of the
iodine/iodide-bromine bromide polyhalide bacteriocidal strong base
anion-exchange resins of my invention are used in the following ranges of
proportions, by weight:
Elemental Iodine--200-230 g
KBr--10-30 g
Water-soluble iodide salt, particularly KI--90-120 g
H.sub.2 O--40-60 g
Starting Resin--0.6 to 1L or in reasonable excess of 1L, but, most
desirably, less than 1L and most advantageously in the range of about 0.6
to about 0.7L.
with the proviso that the mixture of the elemental iodine, KBr,
water-soluble iodide salt and water forms essentially a solid-free and
particularly a wholly solid-free solution prior to being contacted with
the starting strong base anion-exchange resin.
It will also be noted that on the weight basis, the elemental iodine is in
definite excess over the potassium iodide or other water-soluble iodide
salt; the potassium iodide or water-soluble iodide salt is in definite
excess over the KBr; and that the elemental iodine is in definite excess
over the sum of the potassium iodide or other water-soluble iodide salt
and the potassium bromide.
Of the foregoing illustrative embodiments of resin compositions made in
accordance with my invention, Example 1 represents the best embodiment,
overall, of which I am presently aware. The other Examples represent
suitable and operable embodiments of resin compositions which are useful
in the practice of my invention and represent improvements over
bacteriocidal resins which have heretofore been known to the art.
Comparative tests were run with the bacteriocidal resin of Example 1 of the
present invention with what, so far as I am aware, is the best embodiment,
or at least a particularly preferred embodiment, of a bacteriocidal
triiodide resin made in accordance with the aforementioned U.S. Pat. No.
3,817,860. The latter resin is made in accordance with the teachings,
utilizing 220 g of elemental iodine, 140 g of potassium iodide, and 70 g
of deionized water, mixed together to form a solid-free solution, and then
contacting said solution with 1 liter of a strong base anion-exchange
resin, in usual damp form and in the form of granular particles or beads,
followed by washing with distilled water prior to use for the treatment of
bacteria-contaminated water.
Using a flow rate of 5 liters/minute through a 100 ml bed of the said resin
of U.S. Pat. No. 3,817,860, water-effluents with residual iodine-iodide in
the range of 0.8 to 1.3 mg/L were obtained in a series of such tests.
Carrying out the same tests under the same conditions but using, instead,
the bacteriocidal resin of Example 1 of the present application resulted
in water effluents having a total halogen residual (iodine+bromine and
ions) of less than 0.2 mg/L.
In another series of tests, using in one case the same bacteriocidal resin
as that described above of U.S. Pat. No. 3,817,860, and, in the other
case, the bacteriocidal resin of Example 1 of the present application, and
the same 100 ml bed and the same bacteria-contaminated water, but using a
flow rate of 1 liter/minute, the bacteriocidal resin of U.S. Pat. No.
3,817,860 produced an effluent with 2.8 mg/L of iodine/iodide; whereas,
with the bacteriocidal resin of Example 1 of the present application, an
effluent was produced with a halogen residual (iodine+bromine and ions) of
0.4 mg/L.
The exact reasons for and the mechanism accounting for the materially
improved results which are achieved by the practice of my present
invention have not been elucidated and are not fully understood other than
an unknown complex of predetermined proportions of iodine and bromine is
produced and apparently occupies ion exchange sites of the starting strong
base anion-exchange resins. The mere incorporation, broadly, of bromine
and/or bromides with iodine and/or iodides, to the extent that such may be
suggested in U.S. Pat. Nos. 4,187,183 and 4,190,529, for the production of
bacteriocidal resins generally is ineffective and, in most instances, is
inoperative to produce the results achieved by my present invention.
Indeed, these U.S. patents make specific reference to utilizing, in an
after-treatment step, the use of unloaded anion-exchange resins for
scavenging water-effluents to remove liberated iodine or bromine from
water treated by the bacteriocidal resins disclosed in said patents. The
use of such scavenging procedures has not been found to be necessary in
the normal and usual practice of my invention.
The strong base anion-exchange resins which are used as starting materials
for the preparation of the polyhalide bacteriocidal resins of the present
invention are well known to the art and are disclosed, by way of
illustration, in the patents referred to above, the disclosures with
respect to which are incorporated herein by reference. Particularly
preferred are those which contain quaternary ammonium groups. It will be
understood, of course, that identical results are not obtained with the
various strong base anion-exchange resins which are used as starting
resins, but, generally speaking, utilizing the teachings of my present
invention, improvements will normally be obtained to a reasonably
appreciable extent over practices of the prior art as exemplified by the
aforesaid patents and published articles. While the starting strong base
anion-exchange resins are gnerally usable in the form of their sulfates or
chlorides, it is usually preferable to employ them in their chloride form.
Ionac ASB-1 has been found to be particular satisfactory in the practice
of my present invention, but numerous other strong base anion-exchange
resins such as are disclosed, for instance, in the aforesaid patents can
be used very effectively.
* * * * *
|
|
 |
|
 |
Description |
|
