(15) Andronov, B. E., Sergeeva, T. I., Gaeva, T. Y., Yudina, A. K.,
Sb. Navehn Rabot Znst. Okhrany Truda Uses. Tsentr. Sou. Profsoyuzou, 6.89 (1962): Chem. Abs.. 60.15142e. (16) Capkeviciene, E., Vopr. Epidemiol. Gig. Lit. SSR, 1967, 205 (1967); Chem. Abstr., 70,14207e. (17) Bavika, L. I., Shinkarenko. L. S.. Neftekhim. Nefteoererab. 9. -, 40 (1971); Chem. Abstr., 75,154691m. ' (18) Ellis, B. A., "The Investigation of Atmospheric Pollution", 17th Rep., H. M. Stationery Office, 1931. (19) Barton, S. C., McAdie, H. G., International Clean Air Congress, Washington, D.C., Dec. 6-11, 1970 (paper CP-7D). (20) Leahy, D., Siegel, R., Klotz, P., Newmann, L., Atmos. Enuiron., 9,219 (1975). (21) Dubois, L., Thomas, R. S., Teichman, T., Monkman, J. L., Mikrochim. Acta (Wien), 1969, (6), 1268. I
.
(22) Maddalone, R. F., Shendrikar, A. D., West, P. W., ibid. p 391. (23) Scaringelli, F. P., Rehme, K. A., Anal. Chem., 41,707 (1969). (24) Maddalone, R. F., McClure, G. M., West, P. W., ibid., 47, 316 (1975). (25) McClure, G. L., Anal. Chim. Acta, 64,289 (1973). (26) West, P. W., Gaeke, G. C., Anal. Chem., 28,1916 (1956). (27) Thomas, R. L., Dharmarajan, V., West, P. W., Environ. Sci. Technol., 8,930 (1974). (28) West, P. W., Chiang, J. J., J.Air Pollut. Control Assoc., 24, 671 (1974).
Receiued for reuiew March 10, 1975. Accepted October 15, 1975. Work supported by the NSF Foundation Grant No. GP-18081.
Surface Chemistry Parameters in Ecological Cleanup of Oily Wastewater Samuel Kaufman Naval Research Laboratory, Washington, D.C. 20375
Oily wastewater that accumulates on ships must: be freed of oil before discharge overboard to comply with environmental regulations. Current technology employs coalescer filters, usually composed of glass fibers held together by resinous binders. Emulsified oil droplets adhere to the fibers and coalesce, thus separating the oil from the effluent water. However, surfactants in the wastewater interfere with the separation. Six solid substrates, five typical oils, seawater, distilled water, two military specification detergent formulations, and one nonspecification detergent formulation were studied in various combinations. The pertinent measurable surface chemistry parameters were the oil-water interfacial tension, the oil-solid contact angle, and the oil-solid energy of adhesion. Glass and the binders were the least effective substrates for separation, while polypropylene and polytetrafluoroethylene were the most effective. The detergent formulation showing most promise was the nonspecification cleaner.
Oils from various sources on naval ships find their way, by leakage and spills, into the bilge. Surfactants naturally present and intentionally compounded in oils, and others used aboard ships for a variety of cleaning purposes also accumulate in the bilge. These and bilge-cleaning detergents lead to stable dispersions of oil in the bilge water. Periodically, the bilge must be emptied, but environmental requirements prohibit contamination of natural waters with oil, and it becomes necessary to remove the oil from the bilge water before its discharge overboard. In the absence of any treatment of the bilge contents, oil is dispersed in the water in three distinct modes, namely, simple solubility, solubilization (1-3), and emulsification (3,4). The simple solubilities of pure paraffin hydrocarbons of carbon number 1-8 range from less than 1 ppm to about 60 ppm (5). Among these paraffins, solubilities usually decrease with increasing carbon number, and increase with increasing branching. The olefinic, acetylenic, cycloparaffinic, and aromatic hydrocarbons range in solubility from about 3-3600 ppm. However, it should not be expected that these most water-soluble species should be extracted by water in molecularly dispersed (dissolved) form from a 168
Environmental Science & Technology
practical oil to the extent of their solubilities. They are much more soluble in the oil than in water. The extent to which they would be water extracted in true solution would be far less, and would depend upon their concentrations in $he oil, their relative solubilities in oil and water, and the water-to-oil ratio (6). However, other organic species, usually polar, which may or may not contribute to solubilization or emulsification, are present in petroleum oils, and have been observed to be extracted to a much higher degree by the water with which the oil is in contact because of their much greater solubility in water than in oil (6). These substances can also constitute a source of pollution, the seriousness of which depends upon their various individual toxicities, and their concentrations. The contribution of solubilized oil to the total carbon content of artificial seawater can be as high as 5000 ppm ( 3 ) and it is probable that this quantity can be exceeded, depending upon the solubilizing agent, its concentration, and the water-to-oil ratio. Solubilizing agents are usually also emulsifying agents, and can stably emulsify oil. Emulsions are turbid because the sizes of the dispersed oil droplets sufficiently exceed the molecular scale and scatter light appreciably. Surfactants promote emulsification because their polar molecules surround the small droplets of the oil phase which then repel each other due to the electrical charges of like polarity maintained by the sheaths of polar surfactant molecules enveloping the droplets. In the absence of intentionally added surfactant, the coalescer method of separating oil-in-water mixtures has been reasonably successful experimentally. Here the mixture is passed through a coalescer filter, usually composed of glass fibers secured to each other with a resinous binder. Dispersed oil droplets become attached to the fibers as the water passes through. As additional droplets are trapped by the unit they coalesce with those previously attached. When large drops accumulate, they are channeled through and rise to form a separate layer of oil which can be drained off. However, if detergent is present in quantities likely to be used for cleaning operations on board ships, the system fails. The oil droplets do not coalesce, but pass through dispersed essentially as they were in the influent to the coalescer. The objective of the present investigation is to study this failure and ultimately to circumvent the obstacles to a
by 1 cm2 each. The energy required to effect this change, then, is
WA = Tow + Yaw - Yeo
/
\
WATER
(a)
(b) 8 MORE T H A N
B L E S S THAN 90’
WA = yow(1 90’
Figure 1. Contact angle, 0, of oil drop under water
SOLID ( S )
ysw
4
WATER ( W )
Figure 2.
Forces at the oil/water/solid junction
workable separation of oil from bilge water in the presence of detergent. A satisfactory solution to the problem necessitates a careful balance of two antipathetic objectives. On the one hand is the necessity to use effective cleaning formulations aboard ships. These materials accomplish their cleaning function by emulsifying and solubilizing the oil. On the other hand, to maintain a satisfactory ecology the wastewater must be freed of oil, but detergents interfere with the separation. Solubilization and emulsification occur in varying degrees, depending upon the nature of the surfactant in question. In general, however, emulsification is the more troublesome of the two, because its quantitative magnitude usually exceeds that of solubilization. Principles
The principal measurements made were those of the contact angles of oil drops under water on a solid and the interfacial tensions between oil and water. The contact angle, 0, is the angle subtended by the base of the drop against the solid surface and the tangent to its dome where it meets the solid, as in Figure 1. Interfacial tension, the tendency of an interface to contract, may be expressed in terms of either energy or force. In either case the numerical magnitude is the same. Interfacial tensions at liquid-solid interfaces are not experimentally accessible. Consequently, the only accessible approach to the pertinent interfacial study is consideration of the contact angle of the oil on the solid and the interfacial tension at the oil-water interface. If all other effects are considered equal, the lower the oilsolid contact angle, the greater is the mutual attraction between the oil and the solid. Similarly, the lower the interfacial tension between any two phases, the greater is their mutual attraction. A mathematical consideration of the pertinent phenomena is more revealing than this qualitative concept. Figure 2 represents the pertinent interfacial forces and contact angle under water at the oil-water-solid junction of a drop of oil on a solid, where ysw, yso, and yoware the interfacial tensions, respectively, at the solid-water, solid-oil, and oil-water interfaces. At balance, = Yso
+ Yow cos 0
(1)
If the interface between oil and solid is diminished by 1 cm2, the oil-water and solid-water interfaces are increased
+ cos 0)
(3)
The energy of adhesion, then, is a measure of how energetically the oil adheres to or wets the solid, how likely it is to become trapped, or how much energy is required to displace it. Theoretically, this energy can vary between the limits of 0 and 2 yow.From the operational point of view it is a measure of how likely the separation between the two liquid phases will occur a t the oil-water-solid interface. The separation can be viewed as a competition between the two phases for residence on the solid. In Figure l a , if 0 is for instance 20°, its supplement is 180’ - 0 or 160’. The contact angle for the water, then is 160°, an angle whose cosine is negative. Thus 1 cos 160’ is less than unity, whereas 1 cos 0 is greater than unity. The energy of adhesion of the oil to the solid is greater than that of the water to the solid, so the competition favors trapping the oil, all other effects being equal. The oil-water interfacial tension is the same in both cases. Had the magnitudes of the two angles been reversed as in Figure I b , the competition would not favor trapping oil from water; the parameters would favor trapping water from oil.
+
ysw
(2)
where W A is the energy of adhesion, or the energy of displacement of the oil drop from the solid. Combining Equations l and 2 leads to
+
Materials
The following materials were studied: Oils
Description Military spec. Curacao SDR MIL-F-24376A M I L-F-24397 California = l California T F ~ M I L- F-2439 7 Bahrain $1 M I L- F-2439 7 Texaco 2190 TEP M I L-L-17331 F Detergents Description Military spec. Cleaning compound, fuel tank a n d bilge MIL-C-22230A (Purchase I ) Cleaning compound, fuel tank a n d bilge MIL-C-22230A (Purchase I I ) The above two cleaners were purchased to conform to the appropriate military specification, which does not specify composition except for exclusions. Cleaning Fluid A No specification Approximate Composition Component Butyl cellosolve Monoethanolamine soap Monoethanolamine Monoal kylolamide Potassium phosphate Water Isobutyl alcohol 1,2-ethy lene dichloride
%
8.9
7.9 1.1 0.8 3.1 78.0 Trace Trace
Water Distilled water Artificial seawater prepared as directed from distilled water a n d “sea salt” (ASTM D1141-52, Formula a , purchased from Lake Products Co., Inc., St. Louis, Mo.) Solids Teflon (polytetrafluoroethylene), commercial grade Polyvinyl chloride, commercial grade Glass (microscope slide) Polypropylene, commercial grade Binder A Binder B Volume 10, Number 2, February 1976
169
Experimental Procedures All measurements were made a t 25 f 0.3 "C. Artificial seawater was either decanted or filtered to exclude insoluble solid matter present in the sea salt from which it was prepared. The unused binders were proprietary phenolic resin emulsions supplied by Velcon Corp. of San Jose, Calif. They were prepared for use by coating them on microscope slides and curing a t 375 O F for 20 min. The polyvinyl chloride, Teflon, and glass plates had no special treatment. However, the polypropylene plate had a rough surface initially; it was placed between clean polished metal surfaces and compressed in a heated hydraulic press to render its surface flat and glossy. Before each use, the solid plates were thoroughly cleaned with a laboratory cleaning detergent, exhaustively rinsed with distilled water, shaken free of water drops, and air dried. The glass plate, after cleaning with detergent, was further cleaned in a hot nitric-sulfuric acid bath, because a water rinse was judged insufficient to remove traces of interfering detergent and other organic matter from previous use. The other plates are less susceptible to this interference because of their lower surface energies. A plate of the solid to be studied was placed in a holder designed to fit into a rectangular glass cell having a plane viewing side. The essentials of the experimental arrangement have been illustrated by Hamilton (7). After positioning the plate horizontally in the cell, the latter was filled with the requisite volume of water to cover the plate. A drop (1 to 2 ~ 1 of) the pertinent oil was dispensed onto the under side of the plate through a J-shaped needle attached to a microsyringe. The contact angle was then measured with the NRL contact angle goniometer (8). An aggregate of 18 observations were made and averaged for each oilwater-solid combination on a minimum of 3 drops. Because of the slight difference (-0.15 glcc) between the densities of the water and oil, the buoyancy effect of the drop was negligible, and therefore neglected. Interfacial tensions were determined by the drop-weightvolume method by measuring the volume of a drop of water under oil, at equilibrium conditions, that falls from the tip of a tube of known dimensions. Pyrex tubes of appropriate dimensions, and fitted with special tubing connectors, were specially fabricated for this study. The tip of each tube must be turned round and have a flat, lightly ground surface square to the axis, but its edges must be sharp and free of chips, and its external sides must be polished smooth. The bore of the tube should be a capillary whose diameter is small compared to the external diameter of the tip. The glass tube was connected by means of a length of smallbore Teflon hypodermic tubing to a calibrated digital micrometer syringe used to dispense and measure the water. The first few falling drops may yield erratic results, but serve as an approximation, following which concordant results emerge. The average number of drops from which valid results were calculated was about 7. The procedure is exceedingly tedious and time-consuming as compared with the more rapid and easier study of pure liquids with the duNouy ring tensiometer. However, because of the extremely complex nature of the materials to be investigated in this particular study, the ring method was considered to have too many uncertainties associated with it to be used without previous validation against the drop-weight-volume method that is free of the pertinent uncertainties. Densities of the oil and water phases were determined by weighing a metered volume (from a micrometer syringe) of each fluid after equilibration and separation of the two phases. 170
Environmental Science & Technology
The oil-water interfacial tension, yawis calculated from the observed data by the equation, v4pgqJ =-
(4) 2 iTr where u is the drop volume, 4p is the difference between the densities of the two phases, g is the acceleration of gravity, r is the external diameter of the tip of the tube, / ~ , and tabulated by and 4 is a function of r / ~ ~developed Harkins and Brown (9) who perfected the experimental method. Values of the function 4 were later refined by Strenge ( I O ) , who published an equation describing the value of the function F of rlv1l3 where F = $12 r. (9) reveals that the Inspection of the plot of l/+vs. reliability of the measurement is greatest in a limited range Yaw
CURACAO SDR (MIL - F - 24376A) SOLID SURFACE
AQUEOUS PHASE
I
I
L
I
PVC T FP E P
I
D I S T I L L E D WATER
BA 80 GLASS ARTIFICIAL SEA WATER
GLASS PVC
ARTIFICIAL S E 4 W4TER CLEANING FLUID A 2 O O p p m
PP
BB GLASS
1
PP BA
GLASS PVC rFE PP BA BB IO
1
ARTIFICIAL SEA W4TER MIL-C-222304 I I I l 2 0 0 ppm
I 0
ARTIFICIAL S E I WATER MlL-C-22230A~Il.200PPm
20 30 ERGSKM~
40
50
I ENERGY OF ADHESION X INTERFACIAL TENSION PVC P O L Y V I N Y L CHLORIDE TFE TEFLON ?P POLYPROPYLENE 84 BINDER "A" BB BINDER " 0 "
Figure 3. Interfacial tension and adhesion with Curacao oil (MIL-F24376A) CALIFORNIA ' 1
(MIL-F-243971
SOLID SURFACE
AQUEOUS PHASE
GLASS D I S T I L L E D WATER BA
PP BA BB
I
GLASS
'
PP
I
PP
I
,
ARTIFICIAL SEAWATER M I L - C - 2 2 2 3 0 A 11).2 0 0 0 0 m
1
ARTlFICl4L S E 4 WATER M I L - C - 2 2 2 3 0 4 ( I l l 2OOopm
GL4SS PP 0A
is
p 1 O
IO
I X
PVC TFE P? BA BB
I
I
20 30 ERGSKM~
ARTIFICIAL SEA W4TER CLEANING F L U I D A 2000pm
1
I
40
50
ENERGY O F ADHESION INTERFACIPL TENSION P O L Y V I N Y L CHLORIDE TEFLON POLYPROP,ILENE BINDER "A BINDER "0"
Figure 4. Interfacial tension and adhesion with California # 1 oil (MILF-24397)
Oil Curacao SDR Calif. #1 Calif. # 2 B a h r a i n $1
Texaco TEP
Table I . Contact Angles ( 6 , '), for Oil on Substrates PolyproPolyvinyl Glass chloride Teflon pylene Aqueous Phase: Distilled Water 133.2 131.6 136.4 135.2 148.0
55.2 46.2 49.9 63.1 61.2
13.9 21.6 17.0 26.1 15.8
Binder A
Binder B
19.3 26.5 26.0 23.5 26.0
69.5 -
80.7 -
19.9 21.1 26.5 19.5 22.7
51.4 83.6 118.2 123.8 123.8
61.2 77.6 110.2 110.9 111.0
97.6 105.0 111.9 125.3 134.4
72.4 75.3 100.4 105.4 114.9
Aqueous Phase: Artificial Seawater Curacao SDR
Calif. el Calif. #2 Bahrain --1
Texaco TEP
143.0 144.2 168 144.6 160.4
53.9 54.8 53.6 57.7 68.3
11.6 19.1 15.3 21.7 28.7
Aqueous Phase: Artificial Seawater, 200 Ppm Cleaning Fluid A Curacao SDR Calif. #l Calif. r;2 Bahrain k l
Texaco TEP
136.2 120.1 138.7 137.9 133.8
54.4 47.4 53.6 57.2 68.3
19.0 17.8 12.7 20.1 18.9
20.0 17.6 19.0 19.6 20.9
Aqueous Phase: Artificial Seawater, 200 P p m M IL-C-22230A (Purchase I ) Curacao SDR Calif. t'l Calif. i i 2 Bahrain #1
Texaco TEP
159.1 -170 167.5 163.4 164.1
64.1 71.6 63.8 73.8 94.1
23.8 17.9 18.8 21.2 52.1
18.4 25.9 23.3 29.0 22.5
87.5 134.4 158.0 162.6 163.8
61.1 102.3 132.0 161.8 156.1
Aquepus Phase: Artificial Seawater, 200 Ppm MIL-C-22230A (Purchase I I ) Curacao SDR Calif. +1 Calif. k 2 Bahrain +tl
Texaco TEP
141.5 171.7 160 143.8 163.6
58.9 47.3 59.5 58.9 69.9
of r/v1l3. Therefore the series of special tubes mentioned above provided the necessary choices of tube for the various magnitudes of interfacial tensions to be measured. Oil-water combinations to be studied were prepared by combining 1 volume of oil with 59 volumes of the selected water or water-detergent formulation in a conical flask, and stirring as gently as possible with a magnetic stirrer for a minimum of 72 h, for which duration preliminary experiments indicated equilibrium had been attained. Vigorous stirring was avoided to prevent appreciable emulsification which might interfere with the measurements to be executed. The extremely small droplets of an emulsion cannot be used for measuring either the contact angle or the interfacial tension by available methods, and the employed mode of preparation approximates the same interfacial equilibrium that would be extant in an emulsion, or a t least should reveal the same trend of effects among the different combinations of oil and water. Following the equilibration, the contents of the flask were transferred to a separatory funnel and allowed to stand until a clean separation occurred between the oil and water phases. Then each phase was collected in a separate container for use in the measurements. On a very few occasions it was necessary to centrifuge the oil phase to obtain the clean separation required for reliable measurement.
Results and Discussion Table I is a compilation of the contact angles derived from the experimental measurements, and Figures 3 to 7 display the interfacial tensions and energies of adhesion found. Each of the figures graphically shows the data associated with one oil and illustrates comparatively the inter-
17.7 15.9 15.1 13.9 26.4
21.2 23.3 19.6 23.7 21.0
90.2 96.8 115.7 123.8 138.6
58.2 79.6 93.1 104.0 116.3
facial tensions and the effects of the detergents, compositions of the water, and the solid surfaces upon the energies of adhesion for the combinations studied. It becomes obvious that for each combination of liquid phases in the array of data, the lowest energy of adhesion is exhibited by the oil on the glass surface. Polypropylene and Teflon, without exception, are the solid surfaces upon which the oil exhibits the highest energies of adhesion, and there is very little difference between these two in this respect. Polyvinyl chloride rates next to Teflon and polypropylene in all cases except with the Curacao oil (Figure 3). There, in the cases of artificial seawater and artificial seawater with the specification cleaner (Purchase 111, the polypropylene rates respectively, slightly lower than Binder A, and approximately equal to Binder B. With these two exceptions, the binders rate lower than all the other solids but glass. The discrepancies are so slight as to be considered insignificant. Considering the aforementioned discussion of principles, the energies of adhesion derived from the measurements are believed to serve as ratings of operational effectiveness. High values of these energies, then, indicate high driving forces for separation of the two phases, and low values indicate the opposite. I t now becomes apparent that polypropylene and Teflon should serve best among the solids investigated as prospective materials for the internal structure of coalescer filters. The interfacial tension, one mathematical component of the energy of adhesion (Equation 3), has some significance if considered separately, although it is not as revealing as the adhesion cqnsiderations. It is observed that in the cases of all the seawater-detergent compositions, the interfacial tensions are highest where Cleaning Fluid A is the deterVolume 10, Number 2, February 1976
171
CALIFORNIA
*2
(MIL-F-24397)
SOLID SURFACE
T E X A C O T E P STEAM TURBINE SOLID SURF4CE
AQUEOUS PHASE
I
k
OIL M I L - L - 1 7 3 3 1 F 4QUEOUS PHASE
I
D I S T I L L E D W4TER
PP Flb ""
BE
1
GLASS PVC TFE EA P P E6
GLASS PVC
4RTtFlClAL SE4 W4TER
4RTiFlCl4L SE4 W4TER
P TFE P E4 BE
I
4RTlFlCl4L S E 4 V,ATER CLE4NlNG FLUID A , 200 ppm
I PP en
GLASS
__
PP
~
91
EB 10
C
20 30 ERGS/CMZ
1
I
40
50
ARTlFlCl4L SEA WATER M I L - C - 2 2 2 3 0 4 1 1 1 ZOOuum
ARTiFIClAL S E 4 W4TER M I L - C - 2 2 2 3 0 A i I l . 2 0 0 Dum
ARTIFICIAL SEA W4TER MIL-C-22230A IIIl,200ppm
ARTIFICIIL SEA WATER M I L - C - 2 2 2 3 O A ( U I , 200 uum
I ENERGY OF ADHESION X INTERFACIAL TENSION PVC W L Y V I N Y L CHLORIDE TFE TEFLON PP POLYPROPY-ENE EA EINDER 4 E6 BINDER E
I ENERGY OF ADHESION X INTERF4CIAL TENSION POLYVINYL CHLORIDE TEFLON PP POLYPROPYLENE EA BINDER "4" E6 6lNDER"E' PVC TFE
Flgure 5. F-24397)
Interfacial tension and adhesion with California #2 oil (MIL-
Flgul'e 7. Interfacial tension (MIL-L-1733 1F)
and adhesion with Texaco 2190 TEP oil
F-24397)
in turn, its interfacial tension against oil. Because of the extreme complexities of these mixtures, no speculation is offered for this unexpected fact. Nevertheless, the interfacial tensions observed are consistent with the energies of adhesion; the examples with distilled water all show higher energies of adhesion than those with seawater for any given oil. The contact angles (Table I) are also significant when considered alone. They constitute an anticipated performance rating of the solid surface of interest. Low contact angles suggest high performance and vice versa. It is observed that the lowest contact angles are those on Teflon and polypropylene; again this is consistent with the highest energies of adhesion for these two solids. In addition to considering the contact angle as a mathematical component of the energy of adhesion (Equation 3), it can be viewed from a geometric point of view. The lower the contact angle of the oil on the solid, the greater is its degree of spreading. For a given drop volume, then, a low contact angle will result in more surface coverage of solid than would be the case for a high angle, as in Figure l a and l b . This should lead to high probability for coalescence and superior operational performance in the coalescer. At the present time it is not known which of the ingredients of Cleaning Fluid A are responsible for the superior showing this formulation has made.
gent. The trend shows agreement with the findings of Pontello et al. ( I I ) , that the Cleaner A gave the best overall performance characteristics of the detergents tested in their coalescence study. It is further observed in every case, with the exception of the Curacao case, that the interfacial tensions are lower with seawater in the presence of detergents than they are in the absence of detergent. This effect is to be expected on the basis of the universal experience with detergents. The interfacial tension alone, then, can be considered a factor in evaluating a detergent for operational predictions. One fact contained in the data may not have been expected, namely that the distilled water combinations exhibit higher interfacial tensions than those with seawater, in the absence of detergent. It is usually anticipated that salts in water will increase surface tension and,
Conclusions Significant conclusions derived from this study are: 1. Glass and the binders (high energy solids) used for fiberglass filters show the least promise of the materials studied as prospects for the internal structure of coalescers for separating oil-in-water dispersions. 2. Teflon and polypropylene (low energy solids) show the most promise as the materials for the same purpose, and here little difference in their merits was found. 3. Of the detergents studied, Cleaning Fluid A is the one which should interfere least with the oil-water separation. 4. Adhesion of oil to the solid surfaces observed is best in distilled water, poorest in artificial seawater containing detergents, and intermediate in seawater in the absence of detergents.
BAHRAIN
#I
(MIL-F-24397)
SOLID SURFACE
4QUEOUS PH4SE
I
I
1
x
1
1
I
GLASS DISTILLED W4TER
PP EA
I
4RTlFICl4L SEA WATER
P T FPE
BB GL4SS PVC TFE
4RTIFlClAL SEA W 4 T E R CLEANING F L U I D 4 2 0 0 D u m
00
EA
BE PVC GLASS
4RTlFlClAL SE4 WATER M I L - C - 2 2 2 3 0 4 I11 2 0 0 Dum
TFE PP
GLASS PVC TFE PP EA
ARTIFlCl4L SEA W4TER MIL-C-222301 iIII,200uum
BB
1 0
10
1
1 20 30 ERGSKM~
I
I 40
50
I ENERGY O F ADHESION X
PVC TFE PP EA
BB
INTERFACIAL TENSION POLYVINYL CHLORIDE TEFLON POLYPROPYLENE BINDER "A" ElNDER ' " 0 "
Figure 6. Interfacial tension and adhesion with Bahrain #1 oil (MIL-
172
Environmental Science & Technology
5. It is unlikely that all commercial varieties of the solids studied here would yield precisely the same results. However, it is judged that the rankings would be comparable. 6. The surface chemistry parameters studied here should be important considerations in selecting detergent formulations which may become mixed with oily wastewaters requiring ecological cleanup, and in choosing substrates for the internal structures of coalescer filters. Literature
Cited
(1) McBain, M. E. L., Hutchinson, E., “Solubilization and Related
Phenomena”, Academic Press, New York, N.Y., 1955. (2) Kaufman, S., in C. A. Hampel and G. G. Hawley, Eds., “The Encyclopedia of Chemistry”, 3d ed., p 1021, Van NostrandRheinhold, New York, N.Y., 1972.
(3) Kaufman, S., unpublished Navy report, “Fourth Progress Report on Oil-Water Demulsification, Project No. SF53-554-70616469-01, NRL Problem 61CO2-20.203’’ (5 October 1973). (4) Becher, P., “Emulsions, Theory and Practice,” 2d ed., Rheinhold, New York, N.Y., 1966. ( 5 ) McAuliff, C., J . Phys. Chem., 70,1267 (1966). (6) Sniegoski, P., Water Res., 9,421 (1975). (7) Hamilton, W. C., J . Colloid Interface Sci., 40,219 (1972). ( 8 ) Fox, H. W., Zisman, W. A., J. Colloid Sci., 5,514 (1950). (9) Harkins, W. D. and Brown, F. E., J . Am. Chem. SOC.,41, 499 (1919). (10) Strenge, K. H., J. Colloid Interface Sci., 29, 732 (1969). (11) Pontello, A. P., et al., unpublished Navy report, “Oilmater Pollution Program, Phase 11”, NAPTC-PE-46, October 1974. Receiued for reuiew June 30, 1975. Accepted November 11, 1975. Work supported by the Naual Sea Systems Command.
Sensitive Chemical Method for Routine Assay of Cobalamins in Activated Sewage Sludge Robert A. Beck and John J. Brink” Department of Biology, Clark University, Worcester, Mass. 0 16 10
A method for the routine determination of 1.0-10 wg of total extractable cobalamins from activated sewage sludge has been described. The method involves benzyl alcohol extraction of cobalamins; removal of spectrophotometrically interfering substances from cobalamins using a combination of gel filtration and chromatography on alumina; concentration of trace extracts by lyophilization; and direct quantitation of total cobalamins by high-speed liquid chromatographic (HSLC) peak areas compared to cyanocobalamin standards. The HSLC technique utilized a reverse phase column and a detector a t 550 nm. Radioactive tracer recovery studies for the benzyl alcohol extraction step ranged from 80.2-92.3% depending on sample size.
In recent years a number of studies have implicated cobalamin concentration levels to the population dynamics of phytoplankton as well as dinoflagellates responsible for the red tide (1-8). In view of the mounting evidence that cobalamins may have a significant impact on the marine or freshwater environments, a routine analytical procedure for the direct determination of cobalamins in activated sewage sludge was sought, one that avoided the long meticulous techniques presently available in addition to being quantitative in the 1.0-10 pg range. The method described has been developed for the assay of activated sewage sludge since it is a particularly abundant source of cobalamins. Classical methodologies for the qualitative and quantitative determination of cobalamins in activated sludge have relied heavily on microbiological assays (9-13), each of which has its own idiosyncratic interfering response to one or more compounds such as methionine, thymidine, or deoxyribonucleosides that commonly occur in chemically complex environmental samples. Indirect analyses for cobalamins have been reported (14-16), but such methods are not suitable for activated sewage sludge because of its complex chemical composition.
A method for the determination of cobalamins has been described by Rudkin and Taylor (17) based on the differences in the absorption spectra between cyanocobalamin and the dicyanide complex. The major difficulty with the method is its inability to separate and differentiate cobalamins from colored impurities that interfere with spectrophotometric analyses, especially in the case of activated sludge. Moreover, the method requires a relatively large sample size so that accurate cobalamin absorption spectra may be determined. The direct assay of cobalamins reported in this study is partially based on the combined extraction methods of Rudkin and Taylor (17) and Bacher et al. (18); however, it significantly deviates from available methodologies in that trace cobalamin extracts are concentrated by lyophilization of water rather than heated evaporation; spectrophotometrically interfering colored impurities are effectively separated from cobalamins by means of gel filtration prior to chromatography on activated alumina; and total extractable cobalamins are directly quantitated using high-speed liquid chromatographic (HSLC) analysis. Experimental Sodium nitrite and potassium cyanide were respectively mixed with a sample of known volume or slurry having a known weight of solid in a ratio of 0.5 : 0.2 g per 100 ml, and the p H was adjusted to 4.0. The sample was boiled for 5 min and if necessary, octanol was used as a defoaming agent (18). Zinc acetate dihydrate was dissolved in the pH 4.0 solutions or slurry to a final concentration of 10% w/v (to eliminate the formation of emulsions) and the pH adjusted to 8.5 using sodium hydroxide (50%w/w). The zinc hydroxide floc was separated from the clarified liquor using suction filtration, and the filtrate was mixed with sodium sulfate (20% w/v) and then extracted three times with one-tenth volume of benzyl alcohol (17). One-half volume of chloroform was added to the comVolume
IO, Number 2, February 1976
173
