Ind. Eng. Chem. Res. 2003, 42, 5715-5720
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APPLIED CHEMISTRY Biocidal Polystyrenehydantoin Beads. 2. Control of Chlorine Loading Yongjun Chen,† S. D. Worley,*,† Jangho Kim,‡ C.-I. Wei,§ Tay-Yuan Chen,| J. Suess,| H. Kawai,| and J. F. Williams| Department of Chemistry, Auburn University, Auburn, Alabama 36849, Korea Atomic Energy Research Institute, 150 Duckjin-dong, Yuseong-Gu, Daejeon, 305-353, Korea, Department of Nutrition and Food Science, Auburn University, Auburn, Alabama 36849, and Vanson HaloSource, Inc., Redmond, Washington 98052
It has been demonstrated that the biocidal polymers poly-1,3-dichloro-5-methyl-5-(4′-vinylphenyl)hydantoin and the alkali metal salt and protonated forms of its monochlorinated derivative can be prepared as insoluble porous beads by careful control of the pH in the chlorination step. While the dichloro derivative will be primarily useful in flowing water disinfection applications, particularly for potable water and recreational water, the monochloro compounds will find use in applications in which disinfection contact time is of lesser importance, such as for recirculating water treatment and odor control. Biocidal efficacy and chlorine stability data have been presented, and the potential use patterns of the several derivatives have been discussed. Introduction Work in these laboratories for over two decades has proceeded concerning the development of novel biocidal N-halamine derivatives.1 The focus of the work has been to prepare heterocyclic N-halamine compounds having superior biocidal efficacies, but also having long-term stabilities in contact with aqueous solution, as well as in dry storage. The compounds have derived from the classes oxazolidinones, imidazolidinones, and hydantoins; in general, their hydrolysis equilibrium constants are very low (on the order of 10-10 for the oxazolidinones and imidazolidinones and less than 10-6 for the hydantoin derivatives) such that very little “free halogen” (HOCl or HOBr) is liberated into aqueous solution. This exceptional stability is a consequence of their chemical structures. Those compounds developed in these laboratories have electron-donating alkyl groups substituted on the heterocyclic rings adjacent to the oxidative N-Cl or N-Br moieties which hinder the release of “free halogen” into aqueous solution through a combination of mechanisms (electronic destabilization of negative charge developing on nitrogen, steric hindrance of hydrolysis of Cl+, and prevention of dehydrohalogenation). The combined N-halamines thus serve as contact biocides in aqueous solution and when immobilized on surfaces. [Although it is conventional to refer to “free chlorine” in terms of available Cl2, clearly only one of the two Cl atoms can be functional in oxidation of a cell. We believe that it is more accurate to refer to “free * To whom correspondence should be addressed. Phone: 334-844-6980. Fax: 334-844-6959. E-mail:
[email protected]. † Department of Chemistry, Auburn University. ‡ Korea Atomic Energy Research Institute. § Department of Nutrition and Food Science, Auburn University. | Vanson HaloSource, Inc.
chlorine” as Cl+ for the biocidal moiety and Cl- as being inactive in a biocidal event.] Although the original work done in these laboratories concerned water-soluble N-halamine monomers, more recently the direction of the studies has focused on functionalizing insoluble polymers with N-halamine moieties.2-10 The field of biocidal polymers has expanded rapidly in recent times, and outstanding work has been concentrated on several classes of polymers, e.g., the halogenated poly(styrene-divinylbenzenesulfonamides),11 polymeric phosphonium materials,12 and polymeric quaternary ammonium compounds.13 The N-halamine polymers developed in our laboratories possess several attributes that are advantageous such as the ability to immobilize high concentrations of chlorine to enable rapid biocidal activities, the capability of regeneration upon exposure to aqueous free halogen after the initial charge is spent, and the liberation of very low amounts of corrosive free chlorine into water (less than 1 mg/L). Probably the most important N-halamine polymers that have been developed in our laboratories are the N-halogenated poly(styrenehydantoins)2-6 because of their potential for economical disinfection of potable water, thus improving world health. It was shown that the biocidal polymers poly[1,3-dichloro-5-methyl-5-(4′vinylphenyl)hydantoin] (Poly1-Cl) and poly[1,3-dibromo5-methyl-5-(4′-vinylphenyl)hydantoin] (Poly1-Br) could be prepared by a three-step procedure2 as amorphous solids that were insoluble in water and could be packed into glass columns that functioned as a cartridge filters. It was observed that the filters inactivated numerous species of bacteria, fungi, and even rotavirus in only seconds of contact time in flowing water.2-6 However, the filters containing the amorphous solid tended to plug due to the presence of fine particles causing a deterioration in performance over time. This limitation was circumvented in a surprising development by converting
10.1021/ie0303303 CCC: $25.00 © 2003 American Chemical Society Published on Web 10/17/2003
5716 Ind. Eng. Chem. Res., Vol. 42, No. 23, 2003
Figure 1. The structural formulas of the chlorinated polystyrene hydantoin compounds prepared in this study.
highly cross-linked polystyrene porous beads of uniform size through a series of heterogeneous reactions into biocidal polymers, while maintaining particle size control; the beads, when fully halogenated, provided biocidal efficacies comparable to the amorphous solid.14 However, for applications such as disinfection of recirculating industrial water and odor control in diapers and incontinence pads, it can be envisioned that fully halogenated beads may not be necessary, or even desirable. In this work, it will be shown how, by carefully controlling the halogenation conditions and by appropriate pH adjustments, that the objective noted above can well be accomplished. The stuctures of the four chlorinated poly(styrenehydantoin) compounds to be prepared are shown in Figure 1. Experimental Methods Preparation of Chlorinated Porous Beads. Porous beads of 5.6% cross-linked polystyrene having particle sizes in the range of 250-600 µm and pore sizes of about 50 nm were converted into poly(4-vinylacetophenone) porous beads utilizing a Friedel-Crafts acylation reaction and then into poly(5-methyl-5-(4′-vinylphenylhydantoin) (PSH) cross-linked porous beads as described previously.14 The porous beads were chlorinated under controlled pH conditions in order to achieve specific chlorine loadings. To prepare the dichlorinated beads, poly[1,3dichloro-5-methyl-5-(4′-vinylphenyl)hydantoin] (Poly1Cl), it was found that the chlorination reaction step could be performed either with chlorine gas bubbled into a flask containing the PSH beads in alkaline solution or by the addition of sodium hypochlorite solution (bleach) upon adjustment of the pH below 8.0. An infrared spectrum of a small sample of the beads (crushed to a powder) in a KBr pellet exhibited prominent bands at 1756 and 1807 cm-1 in good agreement with that of the powdered poly[1,3-dichloro-5-methyl5-(4′-vinylphenyl)hydantoin]15 disclosed in U.S. Patent 5,490,983 indicative of an efficient heterogeneous reaction of chlorine with the insoluble, highly cross-linked, porous poly-5-methyl-5-(4′-vinylphenyl)hydantoin beads. An iodometric/thiosulfate titration of weighed, crushed beads prepared as described above indicated that the beads contained about 20.0 wt % chlorine. These beads developed a noticeable chlorine odor in the headspace of a capped vial. When industrial grade sodium hypochlorite bleach (12.5% NaOCl) was used in lieu of chlorine gas, and the pH was held in the range of 8.08.5 using 2 N HCl, the Cl loading could be held at about 17 wt %, at which the “chlorine odor” emitted from the beads was minimal. The infrared spectrum of the beads
from this batch (crushed to a powder) in a KBr pellet exhibited prominent bands at 1751 and 1805 cm-1, slightly lower in frequency than those for the beads containing 20.0 wt % Cl. To obtain a monochlorinated derivative, the chlorination can be performed at higher pH. For example, treatment of the PSH beads with a bleach solution held at pH 8.8 (utilizing 2 N HCl) provided a titrated chlorine content of only 13.3 wt %, and the infrared spectrum then contained prominent bands at 1602, 1731, and 1801 cm-1. The band at 1602 cm-1 is characteristic of the sodium salt of a monochlorinated hydantoin derivative. The two low-frequency bands had similar intensities indicating a mixture of the dichloro derivative and a substantial amount of the monochloro sodium salt. In another experiment, the PSH beads were first chlorinated to high loading (19% indicative of the dichloro derivative) and then treated with dilute NaOH (0.05 N) at 25 °C for 5 min which caused partial formation of the sodium salt. This treatment caused a decline in chlorine loading to 15.5 wt % (IR bands at 1601, 1749, and 1804 cm-1). The 1601 cm-1 band had moderate intensity but was weaker than for the sample discussed above having only 13.3% chlorine loading, indicative of a lesser proportion of monochlorinated sodium salt for this sample. Finally, when the same material (19.0 wt % chlorine loading) was soaked in saturated NaHCO3, which is a much weaker base than NaOH, for 40 min at 25 °C, the resulting beads contained a chlorine loading of 17.3 wt % (IR bands at 1607 (weak), 1751 (strong), and 1806 (moderate) cm-1) indicative of beads containing primarily the dichloro derivative but some of the monochloro sodium salt. Beads having chlorine loadings of about 10 wt % can be prepared by two methods. In one procedure, the porous PSH beads chlorinated at pH 6.5 with bleach (to produce a chlorine loading of 19.0 wt %) were soaked in 0.05 N NaOH for 20 min at 25 °C. The resulting beads contained a chlorine loading of 10.8 wt % (IR bands at 1599 (very strong), 1728 (moderate), and 1784 (weak) cm-1) indicative of beads containing primarily the monochloro sodium salt, but a small amount of the dichloro derivative. In the other procedure, the porous PSH beads were stirred with industrial 12.5 wt % NaOCl and without pH adjustment (the pH of the suspension was 12.5) for 45 min (a similar result occurs in 5 min) at 25 °C. The resulting beads contained a chlorine loading of 10.3 wt % (IR bands at 1598 (very strong), 1724 (moderate), and 1784 (weak) cm-1) indicative of beads containing primarily the monochloro sodium salt but some of the dichloro derivative as in the first procedure. Even with a large stoichiometric excess of free chlorine from NaOCl, the beads were only chlorinated to the 10.3% level at the natural highly basic pH of the suspension. For higher chlorine loadings, downward pH adjustment is necessary. Beads having chlorine loadings lower than about 10 wt % can be prepared by lowering the amount of free chlorine available for reaction with them. For example, 1.0 g samples of the porous PSH beads were reacted with stirring with three different volumes of saturated calcium hypochlorite (1165 mg/L free Cl+) for 1 h each at 25 °C. Following filtration, washing with water, and drying in air under normal laboratory lighting, the samples were titrated for chlorine content. The results were as follows (mL of Ca(OCl)2 solution, % Cl by weight): 100, 6.8%; 150, 9.8%; 200, 10.2%. The infrared
Ind. Eng. Chem. Res., Vol. 42, No. 23, 2003 5717
spectrum of the sample giving the 6.8 wt % loading contained a very strong band at 1596 cm-1 attributable to the calcium salt of the monochlorinated derivative and prominent bands at 1728 and 1782 cm-1 which may be attributed to unreacted PSH. Similar results were obtained when a less than stoichiometric amount of NaOCl was used as the source of free chlorine. Finally, it is possible to convert any sodium salt of the monochloro derivative present to its protonated form (porous poly[1-chloro-5-methyl-5-(4′-vinylphenyl)hydantoin] beads) by addition of dilute acid after isolation of the salt. For example, the beads having 10.3 wt % chlorine discussed above were immersed in 0.6 N HCl for 3 min with stirring at 25 °C. A sample was titrated and found to contain a chlorine loading of 10.8 wt %. The infrared spectrum of the crushed beads now contained prominent bands at 1730 and 1791 cm-1, but the intense, broad band found at 1598 cm-1 for the monochlorinated sodium salt disappeared, leaving only a weak, sharp band at 1607 cm-1 attributable to the aromatic rings of the polystyrene backbone. Biocidal Efficacy Testing. The beads chlorinated as discussed above were tested for biocidal activity against Staphylococcus aureus (ATCC 6538) and, in some cases, Escherichia coli O157:H7 (ATCC 43895) contained in water. Typically, about 3-4 g of chlorinated beads were packed into glass columns having inside diameters of 1.3 cm to a length of about 7.6 cm; the empty bed volumes were in the range of 3.3-4.4 mL. An identical sample column of unchlorinated beads was prepared to be used as a control. After the chlorinated column was washed with demand-free water until less than 0.2 mg/L of free chlorine could be detected in the effluent, an aqueous solution of 50 mL of pH 7.0 phosphate-buffered, demand-free water containing 0.691.3 × 107 CFU (colony-forming units)/mL of the Grampositive bacterium S. aureus or the Gram-negative bacterium E. coli O157:H7 was pumped through the column at a measured flow rate of about 3.0 mL/s. The effluent was quenched with 0.02 N sodium thiosulfate before plating. The microbiological procedures utilized in these laboratories have been described elsewhere.16 Stability and Rechargeability Studies. The dichlorinated and monochlorinated (sodium salt and protonated) beads were tested for retention of chlorine under dry storage. Freshly chlorinated beads initially containing 20.14% chlorine loading (dichlorinated), 17.30% Cl (mixture of dichloro compound and some monochloro sodium salt), 10.55% Cl (monochloro sodium salt), and 10.31% Cl (protonated monochloro compound) were washed thoroughly with chlorine-demand-free water, dried in air at 50 °C for 1 h, and stored in capped vials at ambient temperature with laboratory lighting excluded. Periodically over a 90 d storage time, samples were subjected to oxidative chlorine analysis using an iodometric/thiosulfate titration procedure. Furthermore, the dichloro and monochloro sodium salt beads were also tested for retention of chlorine over an 8-week period at temperatures of 4, 21, and 50 °C when stored in a capped vial containing water (2 g of beads in 6 mL of distilled, deionized water). Similarly, vacuum-packed dichloro beads (initial chlorine loading of about 21%) were stored for 53 weeks at temperatures of 4, 21, and 50 °C and evaluated for retention of chlorine and the extent to which they could be regenerated by further exposure to free chlorine. Also, the same procedures were followed for beads from
the same batch stored for the 53 weeks in a capped vial (not evacuated) at 21 °C for comparison purposes. Odor Control Experiments. Beads prepared as described above with different chlorine loadings (16.5%, primarily poly[1,3-dichloro-5-methyl-5-(4′-vinylphenyl)hydantoin]; 10.2%, primarily the sodium salt of the monochloro derivative; 7.3, entirely the sodium salt of poly-1-chloro-5-methyl-5-(4′-vinylphenyl)hydantoin) were evaluated as to their efficacies in controlling ammonia generation through inactivation of Proteus mirabilis. Blends of 5-10 mg of chlorinated beads and 1.0 g of wood pulp (0.5 or 1.0 wt % beads) were prepared by mixing with 200 mL of distilled water in a blender (Hamilton Beach 7 Blend Master model 57100). Following vacuum filtration, which produced wood-pulp pads, and drying in air at 25 °C, the samples were placed in Petri dishes. An inoculum known to provide a high level of odor was formulated. The formulation included 9 mL of a mixture of 25 mL of pooled sterile human female urine and 1.25 g of urea and 1 mL of an aqueous suspension of 1.3 × 108 CFU/mL of P. mirabilis. Each sample, including a control of wood pulp pad with no biocidal polymer, was inoculated with 1 mL of the formulation described above, and the Petri dishes were sealed with Parafilm and incubated at 37 °C for 24 h. The samples were then measured for ammonia production using Drager tubes (Fisher Scientific, Pittsburgh, PA and Lab Safety Supply, Janesville, WI) capable of detection in the range 0.25 to 30 mg/L. Results and Discussion Preparation of Chlorinated Porous Beads. The biocidal porous beads can be prepared with a range of chlorine loadings from about 6 to 21 wt %. The variables pH, free chlorine concentration and source, nature of base and its concentration, and reaction time are clearly important in production of chlorinated poly(styrenehydantoin) beads with a given chlorine loading. This is an important finding in that the desired disinfection application may require an optimum loading to achieve the desired results while minimizing costs of production and possible undesirable limitations such as emission of free chlorine into solution, outgassing of chlorine vapors, and free-radical side reactions. If the starting PSH beads were 100% pure with no divinylbenzene cross-linking and no unreacted styrene or acetophenone moieties, a percent chlorine loading in poly[1,3-dichloro-5-methyl-5-(4′-vinylphenyl)hydantoin] (Poly1-Cl) of 24.91 would be theoretically possible. Prior work has indicated that the yield of PSH starting from poly(styrene) is about 90%.14,15 This fact, plus the fact that the porous poly(styrene) beads used as the starting material were 5.6% cross-linked with divinylbenzene, a necessary consequence of maintaining bead integrity in the heterogeneous reaction sequence, explains why a maximum loading of only about 20-21% Cl could be obtained when chlorine gas was used with no pH control. The higher the chlorine loading on the beads, the more rapid should be the biocidal event, but other undesirable properties may then be observed. For example, the beads loaded to 20% do emit a noticeable chlorine odor when confined in a capped container, albeit less than that from a container of calcium hypochlorite, and much less than that from a bottle of commercial sodium hypochlorite bleach. Particularly in moist, humid conditions, free-radical chlorination of the
5718 Ind. Eng. Chem. Res., Vol. 42, No. 23, 2003
styrene backbone or other organics present can occur at this high level of chlorination; the exothermicity of this process could conceivably lead to a spontaneous combustion process. Thus, we believe that a lower chlorine loading of the beads is desirable to enhance safety in use and storage. It has been shown that a loading of 17-18% performs extremely well as a disinfectant for biologically contaminated potable water while not presenting the safety hazards mentioned above.14 For most other disinfection applications considerably lower loadings are sufficient. Although an iodometric/thiosulfate titration procedure appears to be the recommended approach for measuring chlorine loadings on the beads, a rapid qualitative indication can be obtained from an infrared spectrum of crushed beads in a KBr pellet. This was first observed to be the case in these laboratories during an ATR-FTIR study of Nylon 66 which had been functionalized by a chlorinated hydantoin moiety.17 Primarily dichlorinated beads (18%) exhibit an IR spectrum with two prominent bands at about 1806 and 1751 cm-1. These two bands correspond to the carbonyl stretching vibrational modes for the dichlorinated hydantoin moiety. For unchlorinated PSH, these bands red shift to about 1777 and 1724 cm-1. As the chlorine loading increases, the two bands blue shift, e.g., at 10.0% to 1784 and 1728 cm-1 and at 13.3% to 1801 and 1731 cm-1. Furthermore, under high pH conditions at which a monochloro derivative exists, the presence of the sodium or calcium salt is signified by a prominent band at about 1600 cm-1 which disappears upon protonation under acidic conditions. In this case, the chlorine is bound to the amide nitrogen of the hydantoin moiety; the imide proton, being more acidic, is removed by the base. As discussed in the Experimental Methods, the dichloro bead derivative is prepared predominantly when the pH is adjusted below 8.5. We recommend the use of sodium hypochlorite over chlorine gas as the chlorinating agent for safety considerations and ease of handling. The pH should not be allowed to go below 6, as excessive amounts of HOCl, and even chlorine, can result in the reactor which can lead to free-radical chlorination of the poly(styrene) backbone, an exothermic reaction, which could cause a combustion process and/or emission of chlorine gas into the atmosphere. Thus, it is wise to perform the chlorination in a fume hood or, at least, in a well-ventilated area. For the monochloro alkali metal salt bead derivative, sodium hypochlorite or calcium hypochlorite should be used for chlorination with no pH adjustment being necessary as it will remain above 12 and 11, respectively, in which case the chances of an exothermic free-radical process are minimal and no chlorine gas will be produced. The monochloro sodium salt can also be produced from the dichloro derivative by exposure of the dichloro beads to dilute sodium hydroxide. The reason for this is that the hypochlorite anion is more stable in aqueous solution than is the imide N-Cl moiety, the order of stability being amide N-Cl > OCl- > imide N-Cl. For the protonated monochloro bead derivative, the alkali metal salt is first isolated, followed by mild acidification. Since no free chlorine is present during the process, there is little danger of undesirable consequences. Biocidal Efficacy Testing. The dichloro bead derivative gave an outstanding biocidal performance against both S. aureus and E. coli O157:H7 in the column filter test. All of the bacteria were inactivated
in one pass through the column, i.e., a 6.9 log reduction in a contact time of less than or equal to 1.1 s for S. aureus and a 7.0 log reduction in a contact time of less than or equal to 1.1 s for E. coli O157:H7. The control column containing unhalogenated beads gave no reduction of either bacterium in a contact time of 1.6 s when the same concentrations of the inocula were employed. This indicates that the bacteria were inactivated by the beads, not merely lost by filtration. A complete discussion of the control experiments routinely performed in these laboratories has been reported.14 Prior work on viruses (MS2 and poliovirus) showed excellent efficacy of the dichloro beads against these as well.14 Although the biocidal tests for the beads were performed for inoculums in chlorine-demand-free water, the previous powder version of the dichloro derivative required only slightly longer contact times for inactivation in an EPA “worst case water” inoculums,3 so we believe that the beads will also be effective at disinfection of water containing chlorine demand. Experiments concerning the volume of contaminated water which can be disinfected by a specific amount of chlorinated beads before chlorine regeneration is necessary are underway, but not yet completed. Efficacies of the porous beads containing medium and low chlorine loadings against the bacterium S. aureus (ATCC 6538) were also determined using a column test. For beads which were primarily the monochlorinated sodium salt (10.2 wt % chlorine), a complete 7.1 log reduction was observed to occur in a contact time interval of 1.4-2.8 s. For beads which were primarily the monochlorinated calcium salt (6.8 wt % chlorine), a complete 7.2 log reduction was observed to occur in a contact time interval of 1.5-3.0 s. For beads which were primarily the monochlorinated protonated derivative (10.5 wt % chlorine), a complete 7.1 log reduction was achieved in a contact time of less than or equal to 1.3 s. Thus, the monochloro alkali metal salt beads at medium and low chlorine loadings are still biocidal in brief contact times, although not quite as efficacious as the beads with high chlorine loadings discussed above, as expected. Also, the protonated forms of these beads appear to be biocidal in somewhat shorter contact times than are their alkali metal analogues, although the difference is small and probably experimentally insignificant. Stability and Rechargeability Studies. Table 1 shows the relative stabilities to loss of oxidative chlorine in dry storage at ambient temperature over a 90 d period for the beads having several different chlorine loadings. The order of stability (in terms of % Cl retention) was dichloro > mixture of dichloro and monochloro > monochloro protonated > monochloro sodium salt. This order can be rationalized as being the same as the order of hydrophobicities. Moist conditions cause an enhanced loss of chlorine for solid-state Nhalamine compounds. The compounds were stored in capped vials containing laboratory air which was replenished at each sampling period. The monochloro sodium salt should clearly be the most hydrophilic of the compounds. Table 2 shows the stabilities to loss of oxidative chlorine over a 56 d period at three different temperatures for the dichloro and monochloro sodium salt beads stored in capped vials in the presence of water. The data show that the loss process is quite temperature dependent as would be expected and that losses are more
Ind. Eng. Chem. Res., Vol. 42, No. 23, 2003 5719 Table 1. Stability toward Loss of Oxidative Chlorine for Chlorinated Beads in Dry Storage in Closed Vials at Ambient Temperature storage time (d)
% Cl loading
0 7 15 30 90 0 10 16 23 90 0 10 16 23 90 0 7 15 30 90
20.14a 20.06 19.98 19.87 19.03 17.30b 17.15 17.13 16.90 16.23 10.55c 10.50 10.44 10.34 8.68 10.31d 10.26 10.19 10.08 9.29
% loss of Cl 0.40 0.79 1.34 5.51 0.87 0.98 2.31 6.18 0.47 1.04 1.99 17.73 0.48 1.16 2.23 9.89
a Dichloro beads. b Mixture of dichloro and monochloro sodium salt beads. c Monochloro sodium salt beads. d Monochloro protonated beads.
Table 2. Stability toward Loss of Oxidative Chlorine for Chlorinated Beads in Water Stored in Closed Vials at Three Temperatures T (°C)
% initial Cl loading
% Cl loading after 56 d
4 21 50 4 21 50
20.97a 20.97 20.97 8.93b 8.93 8.93
19.11 18.89 5.03 8.28 6.14 0.76
a
Dichloro beads. b Monochloro sodium salt beads.
Table 3. Stability toward Loss of Oxidative Chlorine for Dichloro Beads Stored under Vacuum at Three Temperatures Followed by Regeneration with Free Chlorine T (°C)
% initial Cl loading
% Cl loading after 371 d
% Cl loading after regeneration
4 23 50 23a
21.0 21.0 21.0 21.0
19.2 16.9 7.3 17.6
21.0 19.6 17.2 19.5
a This sample was stored in a capped vial with air in the headspace.
noticeable for the beads of both types soaked in water than for those held in dry storage. However, the chlorine can be at least partially be replenished when the beads of both types are exposed to dilute bleach at pH 8-8.5 for the dichloro beads14 and with no pH adjustment for the monochloro beads. Table 3 shows the stabilities to loss of oxidative chlorine over a 371 d period at three different temperatures for the dichloro beads stored in a vacuum so as to eliminate the presence of any moist air. Also shown are the levels to which the samples could be regenerated by exposure to free chlorine after the storage period. A sample which was stored in a capped vial with air in the headspace at ambient temperature is tabulated for comparison. The data show that there was only a loss of 8.6% of the chlorine content for the sample held at 4 °C for the 371 d, and it could be entirely regenerated. At 23 °C, the loss was between 16 and 20%; surprisingly,
the vacuum-packed sample losing more chlorine than the one with the air in the headspace. However, both could be regenerated to within about 7% of their original loadings. Only the sample held at 50 °C showed a large loss of 65% of its Cl loading, but even it could be regenerated to within 18% of its initial loading. Elemental analysis for Cl indicates that the loss of complete apparent regeneration capability is due to some freeradical chlorination of the polymer backbone, the problem increasing as the temperature increases. This causes an increase in unit molecular weight, which thus leads to a lower % of Cl+ as determined by iodometric/ thiosulfate titration. The samples thus affected should maintain their original biocidal efficacies. Thus, we recommend that the chlorinated beads should be stored at low temperature in as dry an atmosphere as possible. Odor Control Experiments. The wood pulp control sample registered an ammonia concentration greater than 30 mg/L, while all samples (0.5 and 1.0% loadings) containing the chlorinated beads (7.3-16.5 wt % chlorine) registered ammonia concentrations less than 0.25 mg/L. It can be concluded that the porous chlorinated beads are highly effective at inactivating the P. mirabilis bacteria which generate ammonia as a byproduct of urea metabolism, causing a noxious odor, even at very low blends with an absorbent material like wood pulp. The beads with low loadings of chlorine (monochloro derivative-sodium salt or protonated form) should be used in this application avoiding the necessity of preparing the dichloro beads, a more costly and possibly more hazardous procedure. Conclusions This study has shown that poly(styrenehydantoin) biocidal beads can be prepared having different chlorine loadings, namely the dichloro or monochloro (alkali metal salt or protonated) derivatives and mixtures of these. The chlorine loading on the beads and hydrophobicity can be controlled by pH adjustments, nature and concentration of the chlorinating agent, and reaction times. The dichloro beads will be useful in potable water disinfection applications, as small filter columns containing them kill microorganisms and viruses in a few seconds’ contact time. In fact, they are undergoing field testing for this purpose. The monochloro beads, which are less expensive and possibly more convenient to prepare, will find application in the disinfection of recirculating water systems such as swimming pools, spas, and cooling water towers. They might also be useful in disposable diapers, incontinence pads, mattress covers, etc., for the purpose of inactivating microorganisms causing noxious odors. Acknowledgment We acknowledge the support of Vanson-HaloSource, Inc., and the USAF through Contract NO. FO8637-01C-6004 for this work. Literature Cited (1) For example, see review articles: Worley, S. D.; Williams, D. E. Halamine Water Disinfectants. Crit. Rev. Environ. Contrl. 1988, 18, 133. Worley, S. D.; Sun, G. Biocidal Polymers. Trends Polym. Sci. 1996, 4, 364. (2) Sun, G.; Wheatley, W. B.; Worley, S. D. A New Cyclic N-Halamine Biocidal Polymer. Ind. Eng. Chem. Res. 1994, 33, 168.
5720 Ind. Eng. Chem. Res., Vol. 42, No. 23, 2003 (3) Sun, G.; Allen, L. C.; Luckie, E. P.; Wheatley, W. B.; Worley, S. D. Disinfection of Water by N-Halamine Biocidal Polymers. Ind. Eng. Chem. Res. 1995, 34, 4106. (4) Sun, G.; Chen, T. Y.; Wheatley, W. B.; Worley, S. D. Preparation of novel Biocidal N-Halamine Polymers. J. Bioact. Compat. Polym. 1995, 10, 135. (5) Sun, G.; Chen, T. Y.; Habercom, M. S.; Wheatley, W. B.; Worley, S. D. Performance of a New Polymeric Water Disinfectant. J. Am. Wat. Res. Assoc. 1996, 32, 793. (6) Panangala, V. S.; Liu, L.; Sun, G.; Worley, S. D.; Mitra, A. Inactivation of Rotavirus by New Polymeric Water Disinfectants. J. Virol. Methods 1997, 66, 263. (7) Lin, J.; Winkelmann, C.; Worley, S. D.; Broughton, R. M.; Williams, J. F. Antimicrobial Treatment of Nylon. J. Appl. Polym. Sci. 2001, 81, 943. (8) Lin, J.; Winkelmann, C.; Worley, S. D.; Kim, J.; Wei, C. I.; Cho, U.; Broughton, R. M.; Santiago, J. I.; Williams, J. F. Biocidal Polyester. J. Appl. Polym. Sci. 2002, 85, 177. (9) Elrod, D. B.; Figlar, J. G.; Worley, S. D.; Broughton, R. M.; Bickert, J. R.; Santiago, J. I.; Williams, J. F. A Novel Biocidal Elastomer. Rub. Chem. Technol. 2001, 74, 331. (10) Eknoian, M. W.; Worley, S. D.; Bickert, J.; Williams, J. F. Novel Antimicrobial N-Halamine Polymer Coatings Generated by Emulsion Polymerization. Polymer 1999, 40, 1367. (11) For example, see: Emerson, D. W.; Shea, D. T.; Sorensen, E. M. Functionally Modified Poly-styrene-divinylbenzene. Preparation, Characterization, and Biocidal Action. Ind. Eng. Chem. Prod. Res. Dev. 1978, 17, 269. Emerson, D. W. Polymer-bound Active Chlorine: Disinfection of Water in a Flow System. Polymer Supported Reagents. 5. Ind. Eng. Chem. Res. 1990, 29, 448. Emerson, D. W. Slow Release of Active Chlorine and Bromine from Styrene-Divinylbenzene Copolymers Bearing N,N-Dichlorosulfonamide, N-Chloro-N-alkylsulfonamide, and N-Brom-N-alkylsulfonamide Functional Groups. Polymer Supported Reagents. 6. Ind. Eng. Chem. Res. 1991, 30, 2426. Bogoczek, R.; Balawejder, E. K. N-Monohalogeno- and N,N-Dihalogeno-poly(styrene-co-divinylbenzene)sulfonamides (P-SO2NXNa, P-SO2NX2). Polym. Commun.
1986, 27, 286. Bogoczek, R.; Balawejder, E. K. Studies on a Macromolecular Dichloramine-the N,N-Dichloro-poly(styrene-codivinylbenzene)sulfonamide. Angew. Makromolec. Chem. 1989, 169, 119. (12) For example, see: Kanazawa, A.; Ikeda, T.; Endo, T. Polymeric Phosphonium Salts as a Novel Class of Cationic Biocides. III. Immobilization of Phosphonium Salts by Surface Photografting and Antibacterial Activity of the Surface-treated Polymer Films. J. Polym. Sci.: Part A: Polym. Chem. 1993, 31, 1467 and references therein. (13) For example, see: Lambert, J. L.; Fina, G. T.; Fina, L. R. Preparation and Properties of Triiodide-, Pentaiodide-, and Heptaiodide-Quaternary Ammonium Strong Base Anion-exchange Resin Disinfectants. Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, 256. Hazziza-Laskar, J.; Nurdin, N.; Helary, G.; Sauvet, G. Biocidal Polymers Active by Contact. I. Synthesis of Polybutadiene with Pendant Quaternary Ammonium Groups. J. Appl. Polym. Sci. 1993, 50, 651; J. Polym. Sci.: Part A: Polym. Chem. 2001, 39, 3073. (14) Chen, Y.; Worley, S. D.; Kim, J.; Wei, C.-I.; Chen, T. Y.; Santiago, J. I.; Williams, J. F.; Sun, G. Biocidal Poly(styrenehydantoin) Beads for Disinfection of Water. Ind. Eng. Chem. Res. 2003, 42, 280. (15) Worley, S. D.; Sun, G.; Sun, W.; Chen, T. Y. Polymeric Cyclic N-Halamine Biocidal Compounds. U.S. Patent 5,490,983, 1996. (16) Williams, D. E.; Worley, S. D.; Barnela, S. B.; Swango, L. J. Bacterial Activities of Selected Organic N-Halamines. Appl. Environ. Microbiol. 1987, 53, 2082. (17) Lin, J.; Cammarata, V.; Worley, S. D. Infrared Characterization of Biocidal Nylon. Polymer 2001, 42, 7903.
Received for review April 17, 2003 Revised manuscript received September 5, 2003 Accepted September 11, 2003 IE0303303
