US5223149A

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United States Patent 115)

{MUTT UA A

US005223149A

(11) Patent Number: 5,223,149

Antelman [45] Date of Patent: Jun, 29, 1993
[54] TRIVALENT SILVER WATER TREATMENT 5,098,582 3/1992 Antelman ..... 210/759
COMPOSITIONS Primary Examiner—Peter Hruskoci
[75] Inventor: Marvin S, Antelman, Rehovot, Israel Assistant Examiner—Neil M. McCarthy
[73] Assignee: N. Jonas & Co., Inc., Bensalem, Pa. Attorney, Agent, or Firm—Salter, Michaelson & Benson
(21) Appl. No.: 884,712 (57] hod f Mee eee h of
aoa, A method for controlling the growth of bacteria and
[22] Filed: May 18, 1992 algae in utilitarian bodies of water such as industrial
51} Int. CL$ C02F 1/50 cooling towers, swimming pools and hot tubs is de-
Pi
{52} U.S. Cl. 210/764; 210/167; scribed. The method comprises adding to the water
210/169; 424/618; 424/668; 422/19; 422/28; novel trivalent silver compounds. Said compounds are
422/37; 422/905; 514/495 light stable and can be supplied as liquid concentrates
[58] Field of Search ............... 210/167, 169, 764, 916; which will not precipitate any silver whatsoever from
514/495; 424/618, 668; 422/19, 28, 905, 37 saline waters nor will the concentrates stain skin or
< discolor surfaces. Said compounds meet the rigid EPA
[56] References Cited

U.S. PATENT DOCUMENTS

5,073,382 12/1991 Antelman
5,078,902 1/1992 Antelman
5,089,275 2/1992 Antelman

. 210/764
. 210/764
. 210/764

standards of killing 100% of select coliforms within ten
minutes and are efficacious at concentrations as low as
1-2 PPM.

12 Claims, No Drawings

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5,223,149

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TRIVALENT SILVER WATER TREATMENT
COMPOSITIONS

BACKGROUND OF THE INVENTION

The present invention relates to the employment of
trivalent silver (Ag[III]) compounds as bactericidal and
algicidal agents in water treatment. Water soluble triva-
lent silver compounds are part of the class of multiva-
lent silver compounds which have been the subject of
patents granted to the instant inventor for water treat-
ment. To date five such patents have been granted,
namely, U.S. Pat. Nos. 5,017,295; 5,073,382; 5,078,902;
5,089,275; and 5,098,582. These patents all deal with
divalent silver compounds and compositions that are
anti-pathogenic but more particularly with (respec-
tively) soluble complexes, alkaline pH stable composi-
tions, halides, solid stabilized complexes and solid black
oxide. All of said compounds more particularly related
to treating utilitarian bodies of water defined as bodies
of water having an ultimate use such as swimming
pools, hot tubs, industrial cooling towers and municipal
reservoirs where pathogens are known to proliferate.
While all of the cited patents describe multivalent silver
compounds which have many novel advantages in
treating said bodies of water and while they all conform
to regulatory requirements for treating said bodies of
water, such as the rules and regulations of the Environ-
mental Protection Agency for treating swimming pools,
none of the above inventions provides for an antipatho-
genic composition which embodies all of the following
characteristics:

1. A liquid composition;

2. Not precipitated out by halides present in the water
treated;

3. Non-staining in concentrated form to human skin

and to the surfaces of the containing vessel of said bod-
ies of water.
None of the previously patented compounds or compo-
sitions met all of these three criteria, despite the fact that
each invention embodied unique compositions of Ag(II)
moieties. The first patent, for example, in its preferred
embodiments dealing with Ag(II) complexes, though of
liquid composition, stained the skin in concentrated
form and precipitated: cupious white material when
introduced into saline bodies of water. While of all the
previous patents the silver halides were free of this
nuisance and were nonstaining, they all were solid com-
positions which were totally insoluble in water. Ac-
cordingly, a composition meeting these three criteria
was sought. Therefore, attempts were made to synthe-
size water soluble Ag(III) compounds, and testing and
evaluation of their efficacy to see whether they met all
the aforementioned criteria. The Ag(II) compositions
were all light stable and it was verified as anticipated for
Ag(III) as well. Accordingly, the tests and evaluations
proved successful which has led to the final develop-
ment of this invention, namely, trivalent silver composi-
tions capable of killing and/or preventing the replica-
tion of gram positive and gram negative bacteria, as
well as algae in utilitarian water bodies, such as swim-
ming pools, which can be supplied in liquid concentrate
form which will not stain the skin nor precipitate in the
presence of halides.

In the course of the testing of the compositions of this
invention, another previously unanticipated advantage
of these compositions became evident. Whereas all the
previous Ag(II) compositions required additions of

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oxidizing agents, such as alkali metal persulfates, to
synergize their efficacy, these compositions required no
such additions and were efficacious in themselves.

OBJECTS OF THE INVENTION

The main object of this invention is to provide com-
positions embodying trivalent silver compounds capa-
ble of killing and/or inhibiting the growth of bacteria
and algae, particularly in utilitarian bodies of water
when said compositions are added to said water supply.

Another object of the invention is to provide a source
of trivalent silver ions capable of meeting the regular
EPA standards for swimming pools and hot tubs,
mainly, a bactericide capable of achieving 100% kills
within ten minutes.

Still another object of the invention is to provide for
a trivalent silver composition which will perform the
aforementioned anti-pathogenic functions and will not
be subject to the formation of a precipitate in the pres-
ence of halides.

Still another object of the invention is to provide a
trivalent silver composition having all of the aforemen-
tioned functions and characteristics, but which will not
stain the skin nor discolor surfaces with which it is in
contact in its concentrated liquid form.

Still another object of the invention is to provide a
trivalent silver composition having all of the aforemen-
tioned functions, but which can be formulated into a
marketable concentrated liquid product for utilization
in utilitarian bodies of water.

Still another object of the invention is to provide a
trivalent silver composition having all of the aforemen-
tioned functions and characteristics, but which can
perform its anti-pathogenic functions without the need
of adding an oxidizing agent to the composition.

A final object of the invention is to provide a trivalent
silver composition having all of the aforementioned
functions and characteristics, but which is also light
stable, unlike monovalent silver compounds.

Other objects, features, functions and characteristics
of the present invention will become apparent to those
skilled in the art when the present invention is consid-
ered in view of the accompanying examples. It should,
of course, be recognized that the accompanying exam-
ples illustrate preferred embodiments of the present
invention and are not intended as a means of defining
the limits and scope of the present invention.

SUMMARY OF THE INVENTION

This invention relates to the utilization of trivalent
silver compounds for bactericidal and algicidal applica-
tions in utilitarian bodies of water, such as swimming
pools, hot tubs, municipal and industrial water supplies,
as for example, cooling towers.

More particularly, this invention concerns stable Ag-
{III) complexes designated by the principal quantum
number, n=4, and the second quantum number |=2,
delineating sublevel d having eight electrons, the ac-
cepted conventional expression being d® complexes in
contradistinction to the d° divalent complexes and d!0
monovalent complexes of silver.

Trivalent silver complexes were prepared by either
reacting Ag(I-III) tetrasilver tetroxide with a ligand
bearing compound capable of forming Ag(III) com-
plexes or reacting an Ag(I) salt in the presence of said
ligand with an oxidizing agent, such as alkali persulfate,
or in the alternative, by reacting Ag(III) hydroxide

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5,223,149

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complex formed electrolytically by the anodic oxida-
tion of silver in an alkali solution.

Said trivalent silver complexes were subsequently
evaluated as to their efficacy in killing gram positive
and gram negative bacteria in algae in accordance with
the EPA protocols for swimming pools, which require
100% kills of bacteria within ten minutes. The com-
pounds far exceeded the bacteria requirements at con-
centrations of one PPM or less of silver. They were
evaluated with and without persulfate salts at 10 PPM
and were effective without persulfates as bactericides.

The complexes were then evaluated with salt concen-
trations as high as 10% without precipitating halide.

The complexes, which were colored from deep
orange to brown and maroon, were left exposed in clear
glass bottles for three months with constant exposure to
daylight. The complexes were stable and did not de-
compose to silver.

Ag(III) complexes were applied to human skin in
concentrated form containing as much as 5,000 PPM
silver without any silver staining of the skin whatso-
ever.

Of all the Ag(III) complexes prepared, the easiest to
prepare were periodate complexes. Accordingly, a par-
ticular Ag(III) periodate complex was selected for eval-
uation against algae and it proved effective.

The particular Ag(III) periodate selected was pre-
pared by the action of potassium hydroxide on tetrasil-
ver tetroxide (Ag4O4) and is depicted by the following
reaction:

AggOs+6KOH + 4K104= 2K sH2fAg(10¢6)2] + Ag-
20+H20

The Ag(III) periodate complexes can be depicted by
the following structure:

5.

H

oe. 00 0.00
N\VN ZF NY
1 Ag 1
SN ZN ZN

ooo o 00
H

Several Ag(III) periodates have been identified which
conform to this structure, in addition to the aforemen-
tioned one, which was designated by Servian, J. and
Buenafama, H.D., Inorganic Nuclear Chemistry Letters,
1969, 5, 337-8. Another formula is:

K3H4 [Ag(1O¢)2]

(Cohen, G. and Atkinson, G., Inorganic Chemistry 1964,
3, 2, 1741-2.)

DESCRIPTION OF THE PREFERRED
EMBODIMENTS

As illustrative of the preferred embodiments of this
invention are the following examples.

EXAMPLE 1

An Ag(III) periodate was prepared by calculating the
amounts of reactant necessary to form the periodate
complex according to the aforementioned reaction
equation involving KOH, 0.15 grams; tetrasilver tetrox-
ide 1.0 gram and potassium periodate 2.0 grams. The
KOH was first dissolved in 20 ml. of distilled water and
the subsequent ingredients were added, and the entire

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mixture was heated and kept at 65 degrees C. for two
hours. At the end of that time, the supernatant liquid,
which had a rich orange-maroon color, was separated
and was filtered and submitted for analysis to an inde-
pendent laboratory, after it was diluted to a total vol-
ume of 100 ml. in a volumetric flask. The resulting
solution assayed 3290 mg./L Ag and represented a 76%
yield of Ag(III) periodate based on the aforementioned
reaction stoichiometry. Having evaluated the silver
concentration via an independent EPA certified labora-
tory, Ag(III) periodate aliquots were submitted to an-
other EPA certified laboratory for bactericidal evalua-
tion of the Ag(IIT) complex. Accordingly, good labora-
tory practice was followed in accordance with FIFRA
and ffdea/40 CFR 160, May 2, 1984. The bacteria em-
ployed were E. coli, a gram negative pathogenic bacil-
lus. The protocol employed for the evaluations was that
as set forth in AOAC (15th) 1990:965:13 at colony den-
sities of 100K /cc.;,utilizing two exposure times, i.e., five
and ten minutes. Concentrations of Ag(III evaluated
were 0.5, 1.0 and 3.0 PPM. The evaluation pH was 7.5.
Testing was done with controls and with and without
potassium persulfate at a concentration of 10 PPM.
There was 100% inhibition of the colonies after ten
minutes at all concentrations and after five minutes
except for the 0.5 PPM solution.

Having completed the aforementioned evaluations,
another EPA certified laboratory was chosen for more
comprehensive testing according to the aforementioned
protocols excepting that sodium persulfate at 10 PPM
was added to the Ag(III) periodate and tested against
said periodate at zero persulfate and testing was also
done on cultures of Streptococcus faecalis.

Here is a summary of the results in terms of the time
required to give 100% kills of bacteria.

PERS Ag TIME
BACTERIA STRAIN (PPM) (PPM) —_ (MIN)
Strep. 6569 0.0 2.0 40
faecalis 10.0 20 0s
0.0 1.0 5.0
10.0 10 2.0
E. coli 11229 0.0 2.0 2.0
10.0 2.0 05
0.0 1.0 5.0
10.0 1.0 2.0
EXAMPLE 2

An ATTC strain of Chorella. was grown in nutrient
Medium 866 broth under the required lighting. When
optimal growth was reached, the number of organisms
per ml. were determined by microscopic count and then
subcultured. The first Ag(III) periodate complex was
applied to the algae at concentrations of 2 PPM and 4
PPM. The algae were left in contact for one hour, one
day and ten days. The protocol for these tests involved
procedures described in the Water and Waste Water
Manual of the United States Public Health Service. The
exposure tests involved post inoculation in order to
determine whether the compound was algicidal or algi-
static. The Ag(III) periodate complex was found to be
algistatic at 2 PPM and algicidal at 4 PPM after one
hour’s exposure. After one day and ten days, there were
no positive flasks at all. Ten flasks of subculture were
utilized for each test.

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5,223,149

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EXAMPLE 3

Trivalent silver biguanide (Ag[III] bg) was prepared
by modifying the procedure of D. Sen described in the
Journal of the Chemical Society (A) 1969, p. 1304. Bigua-
nide sulfate was stirred in suspension in distilled water
using 6 g./100 cc. of the compound (pH =2.8-3.0). 5 g.
of sodium bicarbonate were added slowly to adjust the
PH. The final pH was 7.7. Accordingly, the pH adjust-
ment resulted in a clear solution. 5 cc. of 10% silver
nitrate were then added to the clear solution followed
by 20 cc. of a 5% sodium persulfate solution. At the end
of two hours, a beautiful precipitate of maroon colored
Ag(III) bg was obtained, which was decanted, purified
and separated. The resulting compound was then sus-
pended in distilled water and serially diluted with dis-
tilled water so as to give a resulting solution which was
3 PPM in Ag(III). Sodium persulfate was then added to
this solution to give a final concentration of 10 PPM of
persulfate. The resulting solution was submitted to the
same testing laboratory for the same type of E. coli
efficacy as described in Example 1. There was 100%
inhibition of E. coli within five minutes.

While there is shown and described herein certain
specific examples embodying the invention, it will be
manifest to those'skilled in the art that various modifica-
tions and rearrangements of the invention may be made
without departing from the spirit and scope of the un-
derlying inventive concept and that the same is not
limited to the particular forms herein shown and de-
scribed except insofar as indicated by the scope of the
appended claims.

What is claimed is:

1. A method for limiting the growth of bacteria and
algae in the water of swimming pools, industrial cooling

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towers, hot tubs and reservoirs which comprises adding
to the water a stable trivalent silver compound.

2. The method as claimed in claim 1 wherein the
trivalent silver compound is a periodate.

3. The method as claimed in claim 1 wherein the said
water is salt water, and wherein no silver halide is
caused to precipitate.

4. The method as claimed in claim 2 wherein the said
water is salt water, and wherein no silver halide is
caused to precipitate.

5. The method as claimed in claim 1 wherein said
trivalent silver compound is supplied as a liquid concen-
trate.

6. The method as claimed in claim 2 where said triva-
lent silver periodate is supplied as a liquid concentrate.

7. The method as claimed in claim 1 wherein said
trivalent silver compound is employed without adding
an oxidizing agent.

8. The method as claimed in claim 2 wherein said
trivalent silver periodate is employed without adding an
oxidizing agent.

9. The method as claimed in claim 1 where said triva-
lent silver compound concentrate will not stain skin or
surfaces with which it is in contact.

10. The method as claimed in claim 2 where said
trivalent silver periodate concentrate will not stain skin
or surfaces with which it is in contact.

11. The method as claimed in claim 1 where said
trivalent silver compound is light stable so as not to
discolor or leave black silver films on the inner surface
of vessels containing the water to be treated.

12. The method as claimed in claim 2 where said
trivalent silver periodate is light stable so as not to dis-
color or leave black silver films on the inner surface of

vessels containing the water to be treated.
* £ £ ke