CA2163857A1 - Water purification system and removal of halides - Google Patents
Water purification system and removal of halidesInfo
- Publication number
- CA2163857A1 CA2163857A1 CA002163857A CA2163857A CA2163857A1 CA 2163857 A1 CA2163857 A1 CA 2163857A1 CA 002163857 A CA002163857 A CA 002163857A CA 2163857 A CA2163857 A CA 2163857A CA 2163857 A1 CA2163857 A1 CA 2163857A1
- Authority
- CA
- Canada
- Prior art keywords
- silver
- water
- activated carbon
- iodine
- iodide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/50—Treatment of water, waste water, or sewage by addition or application of a germicide or by oligodynamic treatment
- C02F1/505—Treatment of water, waste water, or sewage by addition or application of a germicide or by oligodynamic treatment by oligodynamic treatment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
- C02F1/766—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens by means of halogens other than chlorine or of halogenated compounds containing halogen other than chlorine
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/18—Removal of treatment agents after treatment
- C02F2303/185—The treatment agent being halogen or a halogenated compound
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Water Treatment By Sorption (AREA)
Abstract
A process for the purification of water to render it fit for drinking. It is passed first through a halogenated resin and after this through activated carbon impregnated with silver, which contains a comparatively high silver content, of at least two per cent by weight, and up to about 14 weight per cent. A purification system for carrying out such process comprising a sequence of a layer of halogenated resin followed by activated carbon impregnated with at least two weight per cent silver. The impregnated silver absorbs efficiently a high percentage of bromide/bromine, iodide/iodine or mixtures of these.
Description
W O 94/292~8 21 6 3 8 5 7 PCT~US94/05849 WATER PURIFICATION SYSTEM AND REMOVAL OF HALIDES
Fiel~ ~f the Invention Methods for impregnating activated carbon with silver to yield silver loadings much higher than that available commercially are provided, which provide products useful for purifying water, especially from iodides and bromides which may be eluted from iodinated and halogenated disinfecting resins, lowering the concentrations.of the cont~nAting halides to levels acceptable for continuous drinking 10 applications and enabling regeneration of the silver and possibly also of iodine from the precipitated silver halides.
Backqr~un~ of the Invention 15 Silver impregnated activated carbon, (Ag-GAC), is a well known product, used widely for purifying process-water and drinking-water. The function of the silver bound to the activated carbon is to avoid bacterial growth on the carbon bed an~ in the water in contact with it. Filter cartridges 20 contA;nl; ng Ag-GAC do not kill bacteria during normal filtration rates. For this reason Ag-GAC is described as a Bacteriostatic medium and not a Bactericide.
The ~;~um admissible concentration of silver in drinking 25 water is : 0.05 mg/L ( 50ppb) in the USA and Canada and 0.01 mg/L (10 ppb) in the EEC. Therefore, in order to enable application of Ag-GAC for purifying drinking water, the loading of silver on the carbon is low, usually lower than one percent. The highest silver loading offered commercially 30 is 1.0~%.
W094/29~8 2 ~ 6 ~ 8 5 ~ ` PCT~S94/05849 Recently iodinated and halogenated resins have been introduced as water purifiers capable of "instantaneously"
killing bacteria and viruses upon contact between the treated water and the disinfecting resin. The use of equipment 5 contA;~;ng such disinfecting resins for purifying drinking water has been approved by the US-EPA for emergency and intermittent applications, not for continuous consumption, because disinfecting resins elute minute amounts of iodine and iodides into the treated water, and excessive consumption 10 of iodine/iodide may cause hyperthyroidism. The "ad~usted acceptable daily intake" (AADI), of iodine/iodide has been determined to be 1.19 mg/L (Handbook of Water Quality, Standards and Controls by John De Zuane, P.E., Van Nostrand Reinhold, New York 1990). The concentrations of iodine/iodide 15 eluted to the treated water by commercial disinecting resins vary between 2 to 15 ppm (mg/L), depending on the type of the resin and on the salinity and temperature of the treated water. Therefore, application of equipment containing iodinated resins for purifying drinking water for continuous 20 consumption can be possible only if the drinking water purifier contains means which reduce the concentration of iodine/iodide in the product water to 1.19 ppm and preferably considerably lower.
25 Iodides can be removed almost absolutely from a~ueous solutions by precipitating them with silver ions. The solubility product of AgI at 25C is 1.5x10-16, a million times lower than that of AgCl (1.56x10-1) at the same temperature. Therefore, iodides can effectively be eliminated wo 94,2g~8 2 1 6 3 8 S 7 PCT~S94/05849 from drinking water via precipitation as AgI, even in the presence of a large excess of chloride ions such as those existi~g in drinking water. Metallic silver or silver chloride can generate sufficient concentrations of silver ions for precipitating iodides. However, in order to be effective, the surface area of the silver-ion generating solid must be very large. Otherwise it will very quickly be coated with AgI precipitate and become "blind" to the aqueous solution. Granular Activated Carbon (GAC), has a large 10 surface area and can be an efficient "carrier" for silver.
Indeed, Ag-GAC has proven to be effective in removing iodide ions from drinking water.
Nevertheless, commercially available Ag-GACs are not 15 practical for removing iodides from water disinfected by iodinated resins because their silver loading is very low.
Thus, even if we take GAC impregnated with 1.05% silver (the highest silver loading available commercially), than 300 ml of such Ag-GAC (the amount which can be included in a 10"
20 CounterTop Drinking Water Purifier) weigh ~150 grams and contain only -1.50 gr. (1,500 mg) of silver. This amount of silver can, theoretically, precipitate only 1.5x(126.9/107.9) = 1.76 gr. of iodides. Practically, the precipitation efficiency is less than 80%. If we assume that the 25 concentration of iodine/iodide in the water disinfected by an iodinated resin is only 3 ppm, then 300 ml. of 1.05% Ag-GAC
would be sufficient for treating less than 470 liters ~f disinfected water, which is too low a capacity. The minimum reasonable capacity for a 10" CounterTop Drinking Water -W094/29~8 2 ~ ~ ~ 8 ~ ~ PCT~S94/05849 Purifier (which contains a 5~ PreFilter, 300 ml iodinated resin and 300 ml of Ag-GAC) is 1,500 liters - the annual drinking water consumption of one person. With 1.05% Ag-GAC
we can attain less than one third that value.
SummarY of the Invention The present invention relates to a purification device for 10 producing potable water for drinking by humans, comprising a sequence of a bed of a halogenated resin, followed by a bed or separate container containing silver-impregnated activated carbon, loaded with more than two weight per cent of silver.
The carbon is preferably loaded with from 4 to 14 weight-% of 15 silver and a filter is provided for filtering out particulate material.
The invention further relates to a process for the purification of water and for the purpose of converting it to 20 water fit for human consumption comprising passing feed water through a sequence of a halogenated resin, followed by a bed of silver-impregnated activated carbon containing at least two weight per cent of silver. Preferably the resin used is an iodinated one, and preferably the impregnated carbon 25 contains between 4 and 14 weight per cent silver.
The invention also relates to the novel silver impregnated activated carbon containing at least two percent by weight of silver. The system is useful for the purification or 30 treatment of water for reducing the concentration of iodide/iodine in water and also for reducing the ~ 5 - PCT~S 94/ 05 ~ 4~ ~ PEA/Us 2 7 D~C 1~9~
concentration of bromide/bromine, or of mixed iodide/bromide in water. It can be used as a post treatment for water disinfected by passage through an iodinated or halogenated resin. It can be used in conjl~nction with iodinated resins, utilizing the precipitated silver iodide for regenerating silver and iodine.
Ag--GAC loaded with at least 3% silver is therefore desired for practical elimination of iodine/iodide from water disinfected by iodinated resins. Such a product also enables a considerable reduction of the cost of water purification by disinfecting resins, because both the eYrencive silver and the ~Yp~ive iodine when precipit:ated as AgI can easily be trapped (filtered out) by a coarse post filter and regenerated. Furthermore, due to the extremely low solubility of AgI, p}acement of Ag-GAC treatment down-stream the iodinated-resin-filter guarantees that the concentration of both silver and iodine will be lower than the maximum permissible l~vels for continuous dri nki nq applications.
A device for purifying water cont~i~ing iodine, anion ~Ych~ge resin and bacteriostatic carbon has been described in U.S. Patent 4,769,143. This device contains a commercial silver impregnated activated carbon in which the silver lo~n~ i8 1.05% or less. The p~L~- q of 1naoL~oL~ting thi~ Ag-GAC in thQ device is to prevent bacteria, growth in the activated carbon chamber at the exit port.
~he inv~ntors apparently were ~naware that the pre~nc~ of relatively high conc~tration ~2-15 ppm) of iodide ions in the treatéd wate~ would qu$ckly convert the small amount (~ 1.05%) of - silver present to silver iodide, which i8 inactive as a bacteriostat. ~o mention is made of the need to lower the level of - ~E~E~ S~E~
~16~8S7 _ 5/1 - P ~ 9 4 / 0 5 ~ ~ 9 IPEAIUS 2, DE~ 1994 iodine in the treated water for making it suitable for continuous human consumption, nor is such a function claimed or hinted at.
Furthe~ore, the device contains so little silver that it would be useless for rendering the treated water relatively free of iodide S ions for more than a very limited use. Therefore, although the prior alt does reveal the existence of highly silver impregnated carbon CU.S. Patent 3,294, 572), there is no mention of the use of silver lmpregnated carbon, of any silver loading, for rendering wàter treated with iodinated resins suitable for long term human consumpt:ion. As stated above, the reduction of iodine levels is a requirement for the ~Y~n~e~ utilization of iodinated resin te~-h~ology for treating un~afe dri~k~ ng water, a ma~or health menace worldwide.
BRIFF D~C~TPTION OF T~ FIGr~:
The invention i~ illustrated with reference to the enclosed schematical graphical ~ s~ntations in which:
Fig. l i~lustrates total iodine elimination of AG/GAC against quantity of water p~ through the filer, according to Example 1.
Fig. 2 i~ a similar graph, relating to Example 2.
Fig. 3 i8 a similar graph, relating to Example 3.
Fig. 4 is a similar graph, relating to Example 4 Fiq. 5 illustrat-s the effectivity of activates carbon with different.silver content i~ reducing iodin~ content.
Fig. 6 illu~trates the use of 10 percent ~ilver im~e~.. ated active c:arbon with prefiltration in a water purifier.
~l~h~cl~ SHE~ ' W094/2g~8 PCT~S94/05849 2~G3~S~ -6-E x a m P l e s .
A. Preparation of HiqhlY T.o~e~ Aq-GAC.
Example 1: 25.8 g Silver nitrate, 70 ml water, and 31 ml of a 25% Ammonia (as NH3) solution and were combined and stirred until dissolved. The solution was added slowly in 10 ml portions to 165 g 20-50 mesh granulated activated carbon, 10 which had been previously washed with nitric acid and dried.
Agitation between additions was necessary to assure an even mixture. After standing 15 minutes a solution of 15 g fructose in 80 ml o~ water was added. The mixture was placed in an 80C oven for 68 hrs. The small amount of supernatant 15 liquid showed no precipitate with HCl. The product was rinsed well with water and dried at 250C. The yield was 181.2 g, corresponding to 9% silver.
Example 2: 81 g of nitric-acid-washed, dried GAC and 25 20 ml of a cold 1.65 M Hydrazine solution were combined and mixed. A solution chilled to - 8C containing 12.6 g silver nitrate, 5 g EDTA, 45 ml water and 20 ml of a 2S% ammonia solution was added. The mixture was left at room temperature for one hour. The supernatant liquid was tested with 0.1 N
25 HCl and no precipitate was observed, indicating complete reaction. The product GAC was washed and dried at 250C, yielding 97.6 g, corresponding to 8.2% silver.
Example 3: To 90 g of nitric-acid-washed, dried GAC was 30 added 18 g silver nitrate dissolved in 50 ml water with gentle stirring. The mixture was let stand for 15 min. A
~ WO 94/~ 28 216 3 8 5 7 PCT/US94105849 solution ContA~ ni ng 100 ml water, 8.5 g sodium hydroxide and 26 g sodium dithionite (sodium hydrosulfite, 85% min assay) was added rapidly and mixed gently. After 1 hr the GAC is rinsed with water and dried at 250C. The yield was 103 g, corresponding to 11.1% silver; however, it appeared that some silver was lost during the rinse.
Example 4: To 170 ml of nitric-acid-washed, dried GAC
(91.4 g) was added a solution a solution of 10.8 g silver 10 nitrate in 100 ml water giving a moist mixture with no free solution. This mixture is added slowly with stirring to a solution of 50 g sodium chloride in 500 ml deionized water.
The supernatant solution was filtered, revealing oniy 0.7 g of residue (mostly carbon fines). After rinsing and drying 15 the weiyht was 100.8 g corresponding to 6.8% silver as silver chlorid~e.
B. ~-; in~tion of Iodine/Iodides from Water treated by an 20 Iodinatea Resin .
Figure I is a graph of total iodine content in feed water and treated water as a function of the quantity of water passed through a sample of example 1. Figure 2 is a similar graph 25 relating to example 2. Figure 3 is a similar graph relating to example 3. Figure 4 is a similar graph relating to example 4. Figure 5 is a graph of the same parameters, relating to four samples of commercially prepared compositions of the invention. Figure 6 is a graph of eluted wo 94,2gZ~ 7 ~ PCT~S94/05849 ~
iodine and iodide versus the quantity of water passed through a Counter-Top water purifier conta;n;ng disinfecting resin (PDR) and an EC-10 Ag/GAC sample of figure 5.
Figures 1 to 4 demonstrate the effectiveness of the samples of Ag-GAC prepared according to Examples 1 to 4, above in reducing the concentrations o~ iodine/iodide contained in water treated by PuroTech Disinfecting Resin (PDR - a commercial iodinated resin) to levels permissible for 10 continuous human drinking applications. The water treated is Tel-Aviv City tap water, having a conductivity of 950-1,600 ~S/cm, and at a temperature of 21-25C. The water was passed through a chamber containing PDR and then through 150-160 ml of the Ag-GAC sample at a rate of 2 liters/min. Samples were 15 taken of water entering and leaving the Ag-GAC chamber, as shown in the individual graphs.
Figure 5 demonstrates the effectiveness of various types of 5-10~ Ag-GAC, produced specially for these tests by 20 manufacturers of activated carbon and of Ag-GAC, in reducing the concentrations of iodine/iodide contained in Tel-Aviv City tap water treated by PDR, as described above, to levels permissible for continuous human drinking applications. The relevant properties of the Ag-GAC samples tested in this 25 experiment, and their actual performance, are summarized in the Table below. In these tests, 120 ml samples were treated with the same feed stream at a flow rate of 0.72 liters/min each.
~ WOg4/2g~8 21 6 3 ~ ~ ? PCT~S94/05849 _9_ Code EC-10 PC-7 EC-5 SS-5 Density , gr/ml 0.606 0.537 0.573 0.560 Silver Content, % w/w 10 7 5 5 5 gr/L 60.6 37.6 28.6 28.0 Theoretical Capacity for 2.5 ppm I- Feed, liter 28,500 17,700 13,450 13,200 Practical Capacity for 10 < 1 ppm I- Product, lit 21,000 11,000 10,050 9,500 Practical Efficiency, % 74 62 75 72 Figure ~ illustrates the practical use of 10% silver impregnated granular activated carbon together with 5~
prefiltration and iodinated resin disinfection in a single 10" standard CounTertop drinking water purifier. The amount 20 of Ag-GAC used in this example was 280 ml. The capacity of the filter is limited by the permissible maximum or average level of iodide in the product water. Using the "ad~usted acceptable daily intake" tAADI), of iodine/iodide, determined to be 1.19 mg/L, as mentioned previously, the capacity of the 25 filter is approximately 5,000 liters. At the average daily use of 4 liters per person, this capacity is sufficient for a family of four for over nine months or a family of seven for six months, both practical figures, common to many popular water filtration devices.
Fiel~ ~f the Invention Methods for impregnating activated carbon with silver to yield silver loadings much higher than that available commercially are provided, which provide products useful for purifying water, especially from iodides and bromides which may be eluted from iodinated and halogenated disinfecting resins, lowering the concentrations.of the cont~nAting halides to levels acceptable for continuous drinking 10 applications and enabling regeneration of the silver and possibly also of iodine from the precipitated silver halides.
Backqr~un~ of the Invention 15 Silver impregnated activated carbon, (Ag-GAC), is a well known product, used widely for purifying process-water and drinking-water. The function of the silver bound to the activated carbon is to avoid bacterial growth on the carbon bed an~ in the water in contact with it. Filter cartridges 20 contA;nl; ng Ag-GAC do not kill bacteria during normal filtration rates. For this reason Ag-GAC is described as a Bacteriostatic medium and not a Bactericide.
The ~;~um admissible concentration of silver in drinking 25 water is : 0.05 mg/L ( 50ppb) in the USA and Canada and 0.01 mg/L (10 ppb) in the EEC. Therefore, in order to enable application of Ag-GAC for purifying drinking water, the loading of silver on the carbon is low, usually lower than one percent. The highest silver loading offered commercially 30 is 1.0~%.
W094/29~8 2 ~ 6 ~ 8 5 ~ ` PCT~S94/05849 Recently iodinated and halogenated resins have been introduced as water purifiers capable of "instantaneously"
killing bacteria and viruses upon contact between the treated water and the disinfecting resin. The use of equipment 5 contA;~;ng such disinfecting resins for purifying drinking water has been approved by the US-EPA for emergency and intermittent applications, not for continuous consumption, because disinfecting resins elute minute amounts of iodine and iodides into the treated water, and excessive consumption 10 of iodine/iodide may cause hyperthyroidism. The "ad~usted acceptable daily intake" (AADI), of iodine/iodide has been determined to be 1.19 mg/L (Handbook of Water Quality, Standards and Controls by John De Zuane, P.E., Van Nostrand Reinhold, New York 1990). The concentrations of iodine/iodide 15 eluted to the treated water by commercial disinecting resins vary between 2 to 15 ppm (mg/L), depending on the type of the resin and on the salinity and temperature of the treated water. Therefore, application of equipment containing iodinated resins for purifying drinking water for continuous 20 consumption can be possible only if the drinking water purifier contains means which reduce the concentration of iodine/iodide in the product water to 1.19 ppm and preferably considerably lower.
25 Iodides can be removed almost absolutely from a~ueous solutions by precipitating them with silver ions. The solubility product of AgI at 25C is 1.5x10-16, a million times lower than that of AgCl (1.56x10-1) at the same temperature. Therefore, iodides can effectively be eliminated wo 94,2g~8 2 1 6 3 8 S 7 PCT~S94/05849 from drinking water via precipitation as AgI, even in the presence of a large excess of chloride ions such as those existi~g in drinking water. Metallic silver or silver chloride can generate sufficient concentrations of silver ions for precipitating iodides. However, in order to be effective, the surface area of the silver-ion generating solid must be very large. Otherwise it will very quickly be coated with AgI precipitate and become "blind" to the aqueous solution. Granular Activated Carbon (GAC), has a large 10 surface area and can be an efficient "carrier" for silver.
Indeed, Ag-GAC has proven to be effective in removing iodide ions from drinking water.
Nevertheless, commercially available Ag-GACs are not 15 practical for removing iodides from water disinfected by iodinated resins because their silver loading is very low.
Thus, even if we take GAC impregnated with 1.05% silver (the highest silver loading available commercially), than 300 ml of such Ag-GAC (the amount which can be included in a 10"
20 CounterTop Drinking Water Purifier) weigh ~150 grams and contain only -1.50 gr. (1,500 mg) of silver. This amount of silver can, theoretically, precipitate only 1.5x(126.9/107.9) = 1.76 gr. of iodides. Practically, the precipitation efficiency is less than 80%. If we assume that the 25 concentration of iodine/iodide in the water disinfected by an iodinated resin is only 3 ppm, then 300 ml. of 1.05% Ag-GAC
would be sufficient for treating less than 470 liters ~f disinfected water, which is too low a capacity. The minimum reasonable capacity for a 10" CounterTop Drinking Water -W094/29~8 2 ~ ~ ~ 8 ~ ~ PCT~S94/05849 Purifier (which contains a 5~ PreFilter, 300 ml iodinated resin and 300 ml of Ag-GAC) is 1,500 liters - the annual drinking water consumption of one person. With 1.05% Ag-GAC
we can attain less than one third that value.
SummarY of the Invention The present invention relates to a purification device for 10 producing potable water for drinking by humans, comprising a sequence of a bed of a halogenated resin, followed by a bed or separate container containing silver-impregnated activated carbon, loaded with more than two weight per cent of silver.
The carbon is preferably loaded with from 4 to 14 weight-% of 15 silver and a filter is provided for filtering out particulate material.
The invention further relates to a process for the purification of water and for the purpose of converting it to 20 water fit for human consumption comprising passing feed water through a sequence of a halogenated resin, followed by a bed of silver-impregnated activated carbon containing at least two weight per cent of silver. Preferably the resin used is an iodinated one, and preferably the impregnated carbon 25 contains between 4 and 14 weight per cent silver.
The invention also relates to the novel silver impregnated activated carbon containing at least two percent by weight of silver. The system is useful for the purification or 30 treatment of water for reducing the concentration of iodide/iodine in water and also for reducing the ~ 5 - PCT~S 94/ 05 ~ 4~ ~ PEA/Us 2 7 D~C 1~9~
concentration of bromide/bromine, or of mixed iodide/bromide in water. It can be used as a post treatment for water disinfected by passage through an iodinated or halogenated resin. It can be used in conjl~nction with iodinated resins, utilizing the precipitated silver iodide for regenerating silver and iodine.
Ag--GAC loaded with at least 3% silver is therefore desired for practical elimination of iodine/iodide from water disinfected by iodinated resins. Such a product also enables a considerable reduction of the cost of water purification by disinfecting resins, because both the eYrencive silver and the ~Yp~ive iodine when precipit:ated as AgI can easily be trapped (filtered out) by a coarse post filter and regenerated. Furthermore, due to the extremely low solubility of AgI, p}acement of Ag-GAC treatment down-stream the iodinated-resin-filter guarantees that the concentration of both silver and iodine will be lower than the maximum permissible l~vels for continuous dri nki nq applications.
A device for purifying water cont~i~ing iodine, anion ~Ych~ge resin and bacteriostatic carbon has been described in U.S. Patent 4,769,143. This device contains a commercial silver impregnated activated carbon in which the silver lo~n~ i8 1.05% or less. The p~L~- q of 1naoL~oL~ting thi~ Ag-GAC in thQ device is to prevent bacteria, growth in the activated carbon chamber at the exit port.
~he inv~ntors apparently were ~naware that the pre~nc~ of relatively high conc~tration ~2-15 ppm) of iodide ions in the treatéd wate~ would qu$ckly convert the small amount (~ 1.05%) of - silver present to silver iodide, which i8 inactive as a bacteriostat. ~o mention is made of the need to lower the level of - ~E~E~ S~E~
~16~8S7 _ 5/1 - P ~ 9 4 / 0 5 ~ ~ 9 IPEAIUS 2, DE~ 1994 iodine in the treated water for making it suitable for continuous human consumption, nor is such a function claimed or hinted at.
Furthe~ore, the device contains so little silver that it would be useless for rendering the treated water relatively free of iodide S ions for more than a very limited use. Therefore, although the prior alt does reveal the existence of highly silver impregnated carbon CU.S. Patent 3,294, 572), there is no mention of the use of silver lmpregnated carbon, of any silver loading, for rendering wàter treated with iodinated resins suitable for long term human consumpt:ion. As stated above, the reduction of iodine levels is a requirement for the ~Y~n~e~ utilization of iodinated resin te~-h~ology for treating un~afe dri~k~ ng water, a ma~or health menace worldwide.
BRIFF D~C~TPTION OF T~ FIGr~:
The invention i~ illustrated with reference to the enclosed schematical graphical ~ s~ntations in which:
Fig. l i~lustrates total iodine elimination of AG/GAC against quantity of water p~ through the filer, according to Example 1.
Fig. 2 i~ a similar graph, relating to Example 2.
Fig. 3 i8 a similar graph, relating to Example 3.
Fig. 4 is a similar graph, relating to Example 4 Fiq. 5 illustrat-s the effectivity of activates carbon with different.silver content i~ reducing iodin~ content.
Fig. 6 illu~trates the use of 10 percent ~ilver im~e~.. ated active c:arbon with prefiltration in a water purifier.
~l~h~cl~ SHE~ ' W094/2g~8 PCT~S94/05849 2~G3~S~ -6-E x a m P l e s .
A. Preparation of HiqhlY T.o~e~ Aq-GAC.
Example 1: 25.8 g Silver nitrate, 70 ml water, and 31 ml of a 25% Ammonia (as NH3) solution and were combined and stirred until dissolved. The solution was added slowly in 10 ml portions to 165 g 20-50 mesh granulated activated carbon, 10 which had been previously washed with nitric acid and dried.
Agitation between additions was necessary to assure an even mixture. After standing 15 minutes a solution of 15 g fructose in 80 ml o~ water was added. The mixture was placed in an 80C oven for 68 hrs. The small amount of supernatant 15 liquid showed no precipitate with HCl. The product was rinsed well with water and dried at 250C. The yield was 181.2 g, corresponding to 9% silver.
Example 2: 81 g of nitric-acid-washed, dried GAC and 25 20 ml of a cold 1.65 M Hydrazine solution were combined and mixed. A solution chilled to - 8C containing 12.6 g silver nitrate, 5 g EDTA, 45 ml water and 20 ml of a 2S% ammonia solution was added. The mixture was left at room temperature for one hour. The supernatant liquid was tested with 0.1 N
25 HCl and no precipitate was observed, indicating complete reaction. The product GAC was washed and dried at 250C, yielding 97.6 g, corresponding to 8.2% silver.
Example 3: To 90 g of nitric-acid-washed, dried GAC was 30 added 18 g silver nitrate dissolved in 50 ml water with gentle stirring. The mixture was let stand for 15 min. A
~ WO 94/~ 28 216 3 8 5 7 PCT/US94105849 solution ContA~ ni ng 100 ml water, 8.5 g sodium hydroxide and 26 g sodium dithionite (sodium hydrosulfite, 85% min assay) was added rapidly and mixed gently. After 1 hr the GAC is rinsed with water and dried at 250C. The yield was 103 g, corresponding to 11.1% silver; however, it appeared that some silver was lost during the rinse.
Example 4: To 170 ml of nitric-acid-washed, dried GAC
(91.4 g) was added a solution a solution of 10.8 g silver 10 nitrate in 100 ml water giving a moist mixture with no free solution. This mixture is added slowly with stirring to a solution of 50 g sodium chloride in 500 ml deionized water.
The supernatant solution was filtered, revealing oniy 0.7 g of residue (mostly carbon fines). After rinsing and drying 15 the weiyht was 100.8 g corresponding to 6.8% silver as silver chlorid~e.
B. ~-; in~tion of Iodine/Iodides from Water treated by an 20 Iodinatea Resin .
Figure I is a graph of total iodine content in feed water and treated water as a function of the quantity of water passed through a sample of example 1. Figure 2 is a similar graph 25 relating to example 2. Figure 3 is a similar graph relating to example 3. Figure 4 is a similar graph relating to example 4. Figure 5 is a graph of the same parameters, relating to four samples of commercially prepared compositions of the invention. Figure 6 is a graph of eluted wo 94,2gZ~ 7 ~ PCT~S94/05849 ~
iodine and iodide versus the quantity of water passed through a Counter-Top water purifier conta;n;ng disinfecting resin (PDR) and an EC-10 Ag/GAC sample of figure 5.
Figures 1 to 4 demonstrate the effectiveness of the samples of Ag-GAC prepared according to Examples 1 to 4, above in reducing the concentrations o~ iodine/iodide contained in water treated by PuroTech Disinfecting Resin (PDR - a commercial iodinated resin) to levels permissible for 10 continuous human drinking applications. The water treated is Tel-Aviv City tap water, having a conductivity of 950-1,600 ~S/cm, and at a temperature of 21-25C. The water was passed through a chamber containing PDR and then through 150-160 ml of the Ag-GAC sample at a rate of 2 liters/min. Samples were 15 taken of water entering and leaving the Ag-GAC chamber, as shown in the individual graphs.
Figure 5 demonstrates the effectiveness of various types of 5-10~ Ag-GAC, produced specially for these tests by 20 manufacturers of activated carbon and of Ag-GAC, in reducing the concentrations of iodine/iodide contained in Tel-Aviv City tap water treated by PDR, as described above, to levels permissible for continuous human drinking applications. The relevant properties of the Ag-GAC samples tested in this 25 experiment, and their actual performance, are summarized in the Table below. In these tests, 120 ml samples were treated with the same feed stream at a flow rate of 0.72 liters/min each.
~ WOg4/2g~8 21 6 3 ~ ~ ? PCT~S94/05849 _9_ Code EC-10 PC-7 EC-5 SS-5 Density , gr/ml 0.606 0.537 0.573 0.560 Silver Content, % w/w 10 7 5 5 5 gr/L 60.6 37.6 28.6 28.0 Theoretical Capacity for 2.5 ppm I- Feed, liter 28,500 17,700 13,450 13,200 Practical Capacity for 10 < 1 ppm I- Product, lit 21,000 11,000 10,050 9,500 Practical Efficiency, % 74 62 75 72 Figure ~ illustrates the practical use of 10% silver impregnated granular activated carbon together with 5~
prefiltration and iodinated resin disinfection in a single 10" standard CounTertop drinking water purifier. The amount 20 of Ag-GAC used in this example was 280 ml. The capacity of the filter is limited by the permissible maximum or average level of iodide in the product water. Using the "ad~usted acceptable daily intake" tAADI), of iodine/iodide, determined to be 1.19 mg/L, as mentioned previously, the capacity of the 25 filter is approximately 5,000 liters. At the average daily use of 4 liters per person, this capacity is sufficient for a family of four for over nine months or a family of seven for six months, both practical figures, common to many popular water filtration devices.
Claims (12)
1. A process for the purification of drinking water for use over prolonged periods of time without adverse effects due to iodine ingestion, which comprisescontacting the water to be purified with an iodinated resin so as to eliminate bacteria and viruses, followed by passing the disinfected water containing iodide and iodine eluted from the iodinated resin through a bed of activated carbon which is loaded with at least 2 weight percent of silver so as to reduce the concentration of iodine/iodide in the potable water to an acceptable value.
2. A process according to claim 1, where the final iodide/iodine concentration is less than 1.19 ppm.
3. A process according to claim 1, where the activated carbon is granulated and contains from 4 to 14 weight-% of silver.
4. A process according to claim 1, where the silver and iodine are recovered by working up the precipitated silver iodide.
5. A purification device for producing potable water which can be drunk by humans over prolonged periods of time without any adverse effect due to intake of too much iodine/iodide, which comprises a bed of an iodinated resin, followedby a bed of granulated activated carbon carrying at least 2 weight-% silver.
6. A device according to claim 5, where there is provided also a filter for filtering out particulate material.
7. A device according to claim 5, which contains granular activated carbon loaded with from 4 to 14 weight-% silver.
8. Use of silver impregnated activated carbon containing at least two percent by weight of silver for the purification or treatment of water.
9. Use of silver impregnated activated carbon containing at least two percent by weight of silver for reducing the concentration of iodide/iodine in water.
10. Use of silver impregnated activated carbon containing at least two percent by weight of silver for reducing the concentration of bromide/bromine, or of mixed iodide/bromide in water.
11. Use of silver impregnated activated carbon containing at least two percent by weight of silver as a post treatment after iodinated or halogenated resin.
12. Use of silver impregnated activated carbon containing at least two percent by weight of silver in conjunction with iodinated or halogenated resin and utilizing the precipitated silver halide for regenerating silver.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IL105905A IL105905A (en) | 1993-06-03 | 1993-06-03 | Device and process for purification of water |
| IL105905 | 1993-06-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2163857A1 true CA2163857A1 (en) | 1994-12-22 |
Family
ID=11064906
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002163857A Abandoned CA2163857A1 (en) | 1993-06-03 | 1994-05-25 | Water purification system and removal of halides |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0723526A4 (en) |
| JP (1) | JPH08510958A (en) |
| KR (1) | KR960702817A (en) |
| BR (1) | BR9406788A (en) |
| CA (1) | CA2163857A1 (en) |
| IL (1) | IL105905A (en) |
| WO (1) | WO1994029228A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997029995A1 (en) * | 1996-02-12 | 1997-08-21 | Aqua System A/S | Plant for production of drinking water from unfiltered water |
| AUPP474198A0 (en) * | 1998-07-17 | 1998-08-13 | Worldwide Water Technologies Pty Ltd | Portable water treatment apparatus |
| US7402239B2 (en) | 2001-01-09 | 2008-07-22 | Ionics Perpetual, Inc. | Water purification apparatus and method of using the same |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3294572A (en) * | 1963-03-08 | 1966-12-27 | Pittsburgh Activated Carbon Co | Impregnation of carbon with silver |
| US4187183A (en) * | 1975-03-28 | 1980-02-05 | Aqua-Chem, Inc. | Mixed-form polyhalide resins for disinfecting water |
| US4151092A (en) * | 1977-07-11 | 1979-04-24 | Teledyne Industries, Inc. | Portable water filter |
| US4298475A (en) * | 1980-07-18 | 1981-11-03 | Gartner William J | Water purification system |
| DE3108991A1 (en) * | 1981-03-10 | 1982-09-23 | Gesellschaft für Strahlen- und Umweltforschung mbH, 8000 München | METHOD FOR SEPARATING AND COLLECTING IODINE |
| US4769143A (en) * | 1987-02-17 | 1988-09-06 | Or-Tsurim | Device for purifying water |
| GB2215325B (en) * | 1988-02-29 | 1991-10-16 | Pre Mac | Portable water-purifying devices |
| US4995976A (en) * | 1990-05-31 | 1991-02-26 | Water Technologies Corporation | Water purification straw |
-
1993
- 1993-06-03 IL IL105905A patent/IL105905A/en not_active IP Right Cessation
-
1994
- 1994-05-25 CA CA002163857A patent/CA2163857A1/en not_active Abandoned
- 1994-05-25 EP EP94919230A patent/EP0723526A4/en not_active Withdrawn
- 1994-05-25 JP JP7501845A patent/JPH08510958A/en active Pending
- 1994-05-25 WO PCT/US1994/005849 patent/WO1994029228A1/en not_active Application Discontinuation
- 1994-05-25 BR BR9406788A patent/BR9406788A/en not_active Application Discontinuation
- 1994-05-25 KR KR1019950705404A patent/KR960702817A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0723526A1 (en) | 1996-07-31 |
| KR960702817A (en) | 1996-05-23 |
| IL105905A (en) | 2006-04-10 |
| EP0723526A4 (en) | 1996-12-18 |
| BR9406788A (en) | 1996-01-30 |
| WO1994029228A1 (en) | 1994-12-22 |
| JPH08510958A (en) | 1996-11-19 |
| IL105905A0 (en) | 1993-10-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |