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Effect of Shear on Polymer Aided Flocculation of Suspensions Nlcholas D. Sylvester' and Mousa P. Toure Department of Chemical Engineering, Resources Engineering Division, University of Tulsa, Tulsa, Oklahoma 74 104
The effect of shear on t h e flocculating effectiveness of two cationic polymers (NALCO 671 and Aquafloc 418), two anionic polymers (NALCO 8175 and 8170), and one nonionic polymer (NALCO 110-A) was evaluated. The flocculating effectiveness of the polymers tested was determined by conducting jar tests on 1 wt % kaolinite suspensions. The jar tests showed that each polymer possessed an optimum flocculation concentration resulting in a maximum reduction in t u r b d i . Shearing of the polymer solutions resulted in degradation of the polymer molecules, manifested by a decrease in solution viscosity. Degradation increased with increasing shearing time and continuously decreased the flocculation effectiveness of the polymers.
Introduction During the past few years, synthetic polymers, including polyelectrolytes, have come to occupy a unique position in industrial liquid-solid separations as a challenging substitute for the traditional inorganic electrolytes. Polyelectrolytes are the most efficient and most versatile modern flocculating agents. They are long-chain, high molecular weight, water-soluble organic materials. All synthetic and natural polyelectrolytes can be classified on the basis of the type of charge on the polymer chain when the polymer is in solution. Polymers possessing negative charges are anionic, while those carrying positive charges are cationic polyelectrolytes. The extreme length and the high charge density of the molecules are important characteristics in polyelectrolyte behavior. It is now generally agreed that a bridging mechanism as well as electrostatic action account for the flocculation activity of these compounds (La Mer et al., 1957). In its simplest form, the bridging theory of La Mer (1963) postulates that polyelectrolyte molecules attach themselves to the surface of the solid particles in suspension, at one or more active sites, and that part of the polymer extends into the bulk of the solution. This part of the molecules is then able to adsorb onto another suspended particle, and the polymer bridges or links two particles. This process is a dynamic one in which adsorption and desorption take place rapidly until a condition is established in which most of the polymers become attached to one or more sites on the suspended particles. Increasing agglomeration of more particles results in an over-sized floc whose eventual growth is limited by its ability to withstand the hydrodynamic shear forces imposed upon it by agitation. It has been shown experimentally that optimum flocculation is obtained when the surface of the particles is partially occupied by adsorbed polymer (Birkner and Edzwald, 1969; Michaels and Morelos, 1955; Michaels and Bolger, 1964; Simha and Frich, 1954). Recent experimental work has stressed the importance of the structure of the polymer molecule itself on its flocculating efficiency. Linear polymers have been found to be more effective than branched molecules in liquidsolid separations. Also polymer effectiveness increases with increasing molecular weight for the linear polymers, but an optimum molecular weight has been found for branched polymers (Tchobangoglous, 1970). Aside from the bridging or adsorption aspects, three basic mechanisms (not necessarily exclusive) have been proposed to explain the flocculation-coagulation process: 0019-7890/78/1217-0347$01 .OO/O
(1)enmeshment, (2) electrokinetics, and (3) orthokinetics.
The mechanism of enmeshment involves the combination of particles by physical enmeshment within the random coil of the polymer, or attachment to precipitating products of reactions involving the coagulant polyions. Particle removal is primarily a function of pH which directly affects the formation of solid coagulant species and the degree of interaction between particles to be coagulated. Electrokinetic theory stipulates coagulation may be brought about or enhanced by lowering the electrostatic forces of repulsion between particles in suspension through reduction of the {potential. The latter may result from ionization at reactive sites on the particles or by adsorption of ions from solution. The pH, ion strength, and coagulant concentration and charge affect the extent of coagulation through changes in the { potential. Orthokinetic flocculation is induced by the presence of velocity gradients in the continuous phase. The velocity gradients cause the particles to travel at different velocities and collisions result. The kinetic energy imparted to the suspended particles is high enough to overcome the energy barrier between particles. When choosing a polymeric coagulant for a given use, it is important to consider the following characteristics: size of the polymer (e.g., molecular weight and chain length) charge, structure, and concentration. A number of jar tests conducted under adequate operating conditions will normally indicate a flocculation-coagulation program giving an optimum result. Research on the application of polyelectrolytes in industrial processes has been in two main areas. First, theoretical considerations have been investigated relating to adsorption isotherms, adsorption kinetics, adsorption thermodynamics, effective floc size and strength, effect of chain structure and molecular weight, and other surface chemistry parameters (Hahnna, 1968). Secondly, the more empirical type investigations related to pH effect, salt effect, dosage effect, and type of polymer charge have been done. In addition, other parameters such as temperature, suspension type and concentration, and ,(potential have received considerable study. The flocculation-coagulation process is an integral part of all wastewater treatment systems. It is used extensively in the food, paper, chemical, petroleum, and metals industries. Specific applications include meat and poultry processing, paper pulp manufacturing, paint and rubber latex isolation, synthetic fiber production, refinery air flotation processes, and steel manufacturing. The flocculation-coagulation process is performed by mixing two
0 1978 American Chemical Society
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miscible phases (colloidal and polymer solution) which results in a high degree of turbulence, and considerable shearing forces are developed. I t is well known that the shearing of polymer solutions causes degradation which results in a decrease in the polymer molecular weight and a decrease in solution viscosity (Sylvester and Kumor, 1973). The numerous publications and researches on the flocculating function of polymers have left aside the influence of shearing on polymer flocculating efficiency. Thus, the purpose of this study is to investigate experimentally how shearing, which occurs during mixing, affects the flocculating ability of polymers for suspended colloidal particles. Experimental Section The purpose of this work was to evaluate the effect of shearing of polymer solutions on their flocculating ability. The optimum polymer dosage was determined for the destabilization of dilute colloidal clay suspensions under controlled conditions of pH, initial colloidal concentration, shearing intensity, and duration of solution agitation. Plan of Investigation. First jar tests were run on each polymer solution to determine the optimum dosage before any shearing operations. A 250 ppm solution of each type of polymer was sheared at constant rpm for variable periods of time. T o determine the effect of shearing, jar tests were run after each shearing period. Kaolin was selected as the test suspension because it is well known and has well characterized properties (Michaels and Bolger, 1964). Materials. The clay used in this investigation was a Dresser Kaolin (Filler Grade P). Kaolinite clay is a naturally occuring two-layer aluminosilicate having a cation-exchange capacity of 3 to 15 mequiv/100 g; thus, it contains a number of negatively charged sites on its surface. The number mean dry particle diameter according to manufacturer specification was approximately 0.8 pm. The polymers selected for this work were the Nalcolytes 110-A, 671, 8170, 8175, and Aquafloc 418. The four Nalcolytes were provided by the Nalco Chemical Co., whereas the Aquafloc was obtained from Dearborn Chemical Co. Nalcolyte 110-A is a nonionic, high molecular weight linear polymer; Nalcolyte 8170 and 8175 are two high charge density anionic, high molecular weight polymers. Finally, Nalcolyte 671 and Aquafloc 418 are cationic, high molecular weight polymers. Specifications and descriptions of the polymers and the clay used are available (Toure, 1974). Equipment. Four standard multiple laboratory stirrers were used to prepare the polymer solutions. The same stirrers served the mixing purpose in the jar tests. The shearing of polyelectrolyte solutions was performed by three variable speed mixers. Turbidity was determined with a Hellige Turbidimeter. Turbidity is an optical property of a suspension and depends not only on solids concentration, but on the nature of solids present, their size, size distribution, the nature of the incident light, and to a lesser extent to the solids shape, surface charge, and hydration characteristics. Thus, it was necessary to calibrate the optical measurements. In this study the same solids were used for all experiments, and calibration curves were prepared so that a reliable and reproducible measure of solids concentration was obtained. Polymer solution viscosities were measured with two Ubbelhode capillary viscometers. The viscometers were suspended in a constant-temperature bath capable of keeping the temperature constant to f O . l "C. A Curtin-Matheson (Model 5) pH meter was used to ensure suspensions of constant initial pH of 7.0.
Procedures. 1. Preparation of Solutions. All clay suspensions were standardized to pH 7 with potassium hydroxide and contained clay concentrations of 100 ppm. The suspensions were made from a 1000 ppm kaolin stock solution using distilled water. The polymers were dissolved in distilled water by continuous mixing for a t least 24 h. 2. Turbidimeter Operation. The Hellige turbidimeter and two sample tubes of 20- and 50-mm viewing depth were used to determine the percent of suspended solids removed by the flocculation process. All the measurements of turbidity were taken with a maximum error between 1 and 2%. 3. Jar Tests. The coagulation-flocculation jar tests were carried out to determine the optimum polymer dosages. All rapid and slow mixing operations were performed with a multiple position stirrer. One-liter Griffin beakers were used as mixing containers. Five hundred cubic centimeter clay suspension samples (100 ppm) were rapidly mixed for 5 min a t approximately 100 rpm while adding the polyelectrolyte solution in 0.1-cm3 increments from 0.1 to 5 cm3. Following the rapid mixing, the samples were subjected to an additional 10 min of slow mixing at approximately 20 rpm. A 15-min sedimentation period was given to all test samples to allow the flocs, formed during the coagulation-flocculation reactions, to settle from the suspension. Aliquots (150 cm3) of the destabilized suspension were removed from the mixing vessel at a level 1.5 in. below the surface of the liquid and used for residual turbidity measurements. 4. Shearing Operation. Five hundred cubic centimeter polymer samples of concentration 250 ppm were subjected to a constant uniform stirring of 1000 rpm for 3 h at first, then 6-h, 12-h, and finally, 24-h stirring. Three mixers having paddles of the same configuration and the same size were used for this purpose. After each shearing period, a sample was withdrawn and employed for the jar tests and viscosity measurements. 5. Viscosity Measurements. The intrinsic viscosity of a polymer solution is a convenient and fairly reliable measure of the size of a polymer molecule in solution, or perhaps more correctly of the volume occupied by a polymer molecule in solution. If the polymer molecule involved is a flexible chain, the intrinsic viscosity should be directly proportional to the molecular weight of the polymer and hence its chain length (Dollimore and Horridge, 1972). The viscometric measurements of the polymer solutions were made a t 25 "C using two Ubbelhode viscometers. Five measurements were taken for each sample. The reproducibility of these measurements was 0.1 s. Additional information concerning the experimental equipment and procedures is available (Toure, 1974). Discussion of Results The effect of shearing on polymer flocculation was shown by determining the optimum polymer dosage for the flocculation of kaolinite suspensions as a function of polymer type and shearing time. Figure 1 shows the effect of shearing on the reduced viscosity of the Nalco 8175 polymer. Similar results were obtained for the other polymers tested. In each case, the shearing caused a continuous and significant decrease in the measured reduced viscosities clearly demonstrating polymer degradation. From Table I it can be seen that: (1)Aquafloc 418 had the largest percent decrease; (2) Nalco 671 had the smallest percent decrease; (3) Nalco 8175 had the highest initial reduced viscosity level; (4)Nalco 110-A had the lowest initial reduced viscosity level; (5) for the nonionic and cationic polymers, the first 3 h of shearing
Ind. Eng. Chem. Prod. Res.
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Table I. Effect of Shearing o n Reduced Viscosities reduced viscosity a t 50 ppm shearing time, h polymer
0
3
6
12
24
% decrease
Nalco 110-A (nonionic) Nalco 8170 (anionic) ' Nalco 8175 (anionic) Nalco 6 7 1 (cationic) Aquafloc 4 1 8 (cationic)
4.00 12.63 144.90 39.46 13.68
4.18 9.06 135.10 51.74 14.20
3.48 6.79 131.20 37.52 7.93
2.61 4.88 124.30 35.54 4.96
2.18 4.09 118.00 33.45 2.61
45.5 67.6 18.6 15.2 80.9
I
'
0 0 0
A
I
I
NO SHEARING 3HRS SHEARING 6HRS SHEARING 12HRS SHEARING 24 HRS SHEARING
50 100 150 200 250 CONCENTRATION OF POLYMER (ppm)
1
Figure 1. Reduced viscosities of Nalcolyte 8175. "
resulted in an increase in reduced viscosity due to a reduction of the entanglements among the polymer molecules of the initial solution. It is well known that the reduced viscosity of a polymer solution is a convenient and fairly reliable measure of the relative size of polymer molecules in solution (Sylvester and Tyler, 1970). In the case of polyelectrolytes, the apparent chain length in aqueous solution is profoundly influenced by the hydration and the solubilization of the polymer. For ionic polyelectrolytes at infinite dilution, all the ionizable groups may be dissociated and the polymer chain will be fully charged. The repulsion between similarly charged centers on the chain causes it to assume an extended configuration accompanied by maximum charge separation. A t higher concentrations some of the oppositely charged ions will be drawn back to the polymer chain owing to high charge density, thereby neutralizing some of the charges on the chain. This causes them to assume a less extended configuration due to a decrease in the intramolecular Coulombic repulsion. This change in the polymer coil size is accompanied by a change in the hydrodynamic volume and consequently is reflected by the reduced viscosity. Similar behavior of polyelectrolytes was evidenced by Fuoss and Sadek (1949). Figure 1also shows a decrease of the reduced viscosity with increasing shearing. The decrease may be explained by the chain-breaking phenomena. In effect, a highly ionized polyelectrolyte will have its chains greatly extended (one well documented effect attributable to this is the increase in the vs,/C vs. C curve) and an intensive shearing action will tend to break the extended long chains. As a result of this, the solution will contain a larger number of smaller chains and have a lower reduced viscosity. The results substantiate this conclusion. Figure 2 is representative of the optimum dosage plots for the polymers studied. The most effective flocculant was found to be the cationic Aquafloc 418, which removed 96% of the suspended solids at the optimum dose. The maximum removals for the other polymers were: (1)65% removal for cationic Nalco 671; (2) 60% removal for anionic Nalco 8170; (3) 54% removal for anionic Nalco 8175; and (4) 30% removal for nonionic Nalco 110-A.
0.2
0.4 0.6 08 WSAGE OF POLYMER (pprn)
I .o
Figure 2. Optimum dosage curve for Aquafloc 418.
In all cases, the optimum polymer dose was found to be between 0.5 and 0.75 ppm for the nondegraded solutions. The results show that an optimum polymer dose existed as expected from the interparticle bridging mechanism. Among the five polymers tested, the cationic Aquafloc 418 with a 6 ppm residual concentration of kaolin suspension had the best aggregating capacity with an optimum dose of 0.8 ppm. It was found that at very low polymer concentrations there was very little flocculation. As more polymer was added, the flocculation increased to an optimum. At saturation (higher polymer concentration), the flocculation decreased and then leveled off. This type of behavior has been explained by Dixon et al. (1967), Hahnna (1968), and Riddick (1961) for cationic polyelectrolytes; Birkner and Edzwald (1969) for nonionic polymers; and Michaels and Morelos (1957) for anionic polyelectrolytes. For cationic polyelectrolytes, it has been postulated that (Dixon et al., 1967) the addition of high molecular weight cationic polyelectrolytes neutralizes the negative charges on clay particles and consequently their electrostatic repulsion. As a result, the particles are able to approach each other close enough for hydrogen bonding forces to cause polymer bridges to form between them and flocculation occurs. As additional polymer is added, adsorption increases, the surface coverage increases causing bridging to be reduced, and the charge increases to a high positive value. This causes electrostatic repulsion which finally overcomes the bridging effect and redispersion begins. Even though the anionic and nonionic polymers were not very effective as flocculants for kaolin, the flocculation which did take place can be explained by the bridging theory. For these two types of polymers, it has been shown that (Birkner and Edzwald, 1969) high molecular weight components are able to extend from negatively charged surfaces sufficiently far for bridging to occur, thus causing flocculation, without interference from the repulsive forces. In other words, for flocculation to occur with anionic or nonionic polyelectrolytes requires a high molecular weight
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,
x
1
Table 11. Effect of Shearing on Flocculating Effectiveness percent reduction in turbidity at oDtimum dose shearing time, h
12
2n
40c 3 HRS SHEARING
v) 3 v)
-I
3
12 HRS SHEARING
20-
0
24 HRS SHEARING
0
8 K
O
1
polymer
0
3
12
24 %change
Nalco110-A Nalco 8170 Nalco 8175 Nalco 671 Aquafloc418
41 60 54 62 97
40 40 31 48 90
27 35 29 37 85
19 25 27 33 83
54 58 50 47 14
Table 111. Effect of Shearing on Optimum Polymer Dose optimum polymer dose, ppm
Figure 3. Effect of shearing on the flocculating efficiency of Nalcolyk 671.
.
polymer. Like the cationic polymers, the nonionic and anionic ones adsorb on the surface of the particles. At high polymer dosages, as particle surface saturation is approached, the clay particles assume more of the characteristics of the polymer; in consequence, no additional adsorption takes place and redispersion begins. In either case, the configuration of the polymer molecules at the liquid-solid interface is the most probable influencing factor in the bridging action of the polymer. To be effective, the polymer concentration must be less than that required for complete coverage of the particles as this would result in particles being enveloped by a polymer instead of being attached to other particles (Weber, 1972). Another factor to be mentioned is that the adsorption of a regular size flocculant molecule on a particle will result in a rapid shortening of the polymer segment still extending outward into the solution; thus, successful and better flocculation depends on minor changes in the system, on polymer chain length, and its molecular weight. Figure 3 is representative of the effect of shearing on the optimum dosages for the five polymers studied. This figure clearly illustrates that polymer degradation, caused by shearing, resulted in a decreased flocculation effectiveness. It also shows that shearing had a slight effect on the optimum polymer dose. In each case the flocculating capacity was higher before the polymers were subjected to shearing. The longer the shearing time, the lower the efficiency of the various polymers. The effect of shearing can be better understood and explained by some related studies. Variation of filtration rate with flocculant molecular weight as reported by La Mer and Healy (1963) and Walles (1968) has suggested that the more important parameter is not how much polymer has adsorbed onto the surface of the suspended particles, but the length of the extended polymer chain into the solution which affects the probability of a collision and the probability of forming a bridge. Warkentin and Miller (1958) have demonstrated that long anionic polymers can better remove turbidity than can short-chain polymers of the same degree of solubilization. In light of these results, the decrease in the flocculating capacity of the sheared polyelectrolyte solutions is explained below. The long-chain polymers responsible for bridging were broken by the shearing action into shorter chains. The reduction in the polymer chain length resulted in a decrease in the amount of interparticle bridging. In addition, the highest molecular weight components of the polymeric sample, which are primarily responsible for flocculation (because they are able to extend from the charged surface sufficiently far for bridging to occur), are preferentially
shearing time, h polymer
0
3
12
24
Nalco 110-A Nalco 8170 Nalco 8175 Nalco 671 Aquafloc 418
0.6 0.7 0.8 0.5 0.8
0.5 0.7 0.8 0.4 0.7
0.3 1.2 0.7 0.6 0.9
0.4 1.0 0.8 0.5 0.9
broken by shearing (Sylvester and Kumor, 1973). The resulting decrease in molecular size is responsible for the decrease in the flocculating ability of the original material. Table I1 quantifies the effect of shearing on the flocculating effectivenessof the polymers studied. The percent reduction in turbidity at the optimum polymer dose is tabulated for four shearing times. The percent change due to shearing is also shown. The most effective flocculant (Aquafloc 418) also shows the most resistance to degradation. All the Nalco polymers showed a similar change in flocculation effectiveness for 24-h shearing. Table 111 shows that shearing had only a minor effect on the optimum polymer dose. It was expected that, since the shearing caused polymer degradation and reduced the average molecular weight of the polymers, the optimum dosage values would increase with increased shearing in light of the results of Walles (1968) and Caskey et al. (1974). Conclusions As expected, the flocculating efficiency of polymers is very much affected by viscosity and shearing. Within the limits of the experimental conditions and data taken, several important conclusions can be drawn from this study: (1) The reduced viscosity of the polymer solutions decreased with increased shearing time. (2) All polymers studied exhibited an optimum dose for turbidity reduction. (3) In all cases polymer degradation caused by shearing reduced the flocculation effectiveness. Acknowledgment The authors gratefully acknowledge partial support of this work by the University of Tulsa Environmental Protection Projects program and the Department of Chemical Engineering. Thanks are due to Mr. John J. Byeseda for his interest and encouragement. The authors also express their appreciation to the Nalco Chemical Company and the Dearborn Chemical Company for supplying the polymer samples and Dresser Mineral Industries for providing the clay samples. Literature Cited Birkner, F. G., Edzwald, J. K.. J . Am. Water Works Assoc., 61. 645 (1969). Caskey, J. A,, King, P. H., Martin, J. T., presented at 77th National AlChE Meeting, Pittsburgh, Pa., June 1974. Dixon, J. K., La Mer, V . K., Linford, t i . E., J . Colloid Interface Sci., 23, 465
(1967). Dollimore, D., Horridge, T. A., Water Res., 6 , 703-720 (1972).
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 4, 1978 Fuoss, R. M., Sadek, N., Science, 110, 552-554 (1949). Hahnna, H. H.,J . Colloid Interface Sci., 28, 134-144 (1968). La Mer, V. K., Healy, T., Rev. Pure Appl. Chem., 13, 3 (Sept 1963). La Mer, V. K., Smellie, R. H.,Lee, P. K., J . Colloid Sci., 12, 566 (1957). Michaels, A. S., Morelos, O., Ind. Eng. Chem., 47 (9). 1801 (1955). Michaels, A. S., Boiger, J. C., J . Ind. Eng. Chem. Fundam., 3, 14 (1964). Rlddick. T. M.. J . Am. Water Works Assoc.. 53, 1013 (1961). Simha, R., Frich, H. L., J . Phys. Chem., 58, 507 (1954). Sylvester, N. D., Tyler, J. S., Ind. Eng. Chem. Prod. Res. Dev., 9, 548 (1970). Sylvester. N. D.. Kumor, S. M., AlChESymp. Ser, 69, No. 130, 69-81 (1973).
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Tchobangoglous, G., J . Water Pollut. Control Fed., 42 (4), 604 (1970). Toure, M. P., M.S. Thesis, University of Tulsa, Tulsa, Okla., 1974. Weber, W. J., Jr., "Physic-Chemical Processes for Water Quality Control", Wiley-Interscience, New York, N.Y., Warkentin, B. P.,Miller, R. D., Soil Sci., 85, 14 (1958). Wailes, E. W., J . Colloid Interface Sci., 27 (4), 797 (1968).
Received for revieu; March 20, 1978 Accepted August 14, 1978
Isolation of Brassins by Extraction of Rape (Brassica napus L.) Pollen N. Mandava,"' M. Kozempel,' J. F. Woriey,' D. Matthees,' J. D. Warthen, Jr.,' M. Jacobson,' G. L. Steffens,' H. Kenney,* and M. D. Grove3 United States Department of Agriculture, Science and Education Administration, 5eltswille Agricultural Research Center, 5eltsville, Maryland 20705, Eastern Regional Research Center, Philadelphia, Pennsylvania 19 1 18, and Northern Regional Research Center, Peoria, Illinois 6 1604
Rape pollen was used as a source for the production of new natural plant growth-promoting substances, brassins, which contain mostly mixtures of plant lipids. A pilot-scale extraction method was devised to isolate brassins in relatively large quantities. This method utilizes the extraction of rape pollen with 2-propanol followed by solvent partition and a two-step column chromatographic procedure to give biologically active brassins. Similar extraction procedures are suggested for the isolation of natural growth-regulating substances present in minute amounts from other plant sources.
Introduction Since we reported (Mitchell et al., 1970; Mandava, 1971; Mandava and Mitchell, 1971a) that brassins exhibited unusual growth effects, our attention has been directed to the chemical identification of the biologically active constituent(s). This group containing lipoidal substances has been isolated from rape (Brassica napus L.) pollen and has caused growth effects that have never been noted with the known plant hormones (Worley and Mitchell, 1971; Mitchell et al., 1971a; Worley and Krizek, 1972; Mitchell and Gregory, 1972). The active constituents are present in minute quantities; several attempts were made previously to identify them by microanalytical techniques such as GC-MS, but with little success (Mandava and Mitchell, 1972; Grove et al., 1978). Earlier we reported (Mandava et al., 1973) a convenient method for obtaining brassins on a laboratory scale and this method enabled us to produce enough brassins for a series of greenhouse and field experiments. Larger quantities were required for detailed chemical identification. Therefore, we devised a pilot plant size procedure for the extraction of pollen followed by purification of the crude extract. In this paper, we report an isolation method that is useful for the production of brassins and also can be adapted for plant growth-regulating substances from other natural sources (Mandava and Mitchell, 1971b; Mitchell et al., 1971b). Experimental Section Materials used. Rape pollen collected by honeybees in rape fields was obtained from Canada. All solvents used for extraction and isolations were reagent grade. Silica gel Beltsville Agricultural Research Center. Eastern Regional Research Center. Northern Regional Research Center.
60 (70-230 mesh) and preparative silica gel (thick layer) plates were obtained from EM Laboratories, Inc., Elmsford, N.Y. Apparatus. A Coleman Junior spectrophotometer (Model 6A) (Coleman Instruments, Maywood, Ill.) was used for monitoring column chromatographic fractions. All evaporations were carried out either on a laboratory concentrator (GCA/Precision Scientific Co., Chicago, Ill.) or a large Rotavapor (Buchi/Brinkmann Rotavapor R-10, Brinkman Instruments, Inc., Westbury, N.Y.). Pollen Extraction. (1) Laboratory Method. Experiments were carried out to determine suitable pilot plant processing conditions. Rape pollen was washed for 30 min with deionized water (4 mL of water/l g of pollen) and filtered; the process was repeated seven times. The filter cake was dried to less than 1% water and then extracted for 1 h with 2-propanol (3 mL of solvent/l g of pollen). Extractions (6) were carried out until the biological activity of the last extract showed minimal (or marginal) activity on the basis of the amount of extractable active material per unit volume of 2-propanol solution. (2) Pilot Plant Extraction. The pilot plant extraction procedure is shown in Figures 1 and 2. Rape pollen (45.5 kg) was extracted with deionized water (20 pmho) in a 227-L scraped wall kettle, Hamilton style A, double motion scraper agitator (Hamilton Copper and Brass Works Co., Hamilton, Ohio). The slurry was filtered in a Sparkler filter, size 18D10 (Sparkler Manufacturing Co., Conroe, Texas), using A-7 filter paper. The filter cake was continuously washed with deionized water until the filtrate was clear and virtually colorless. The washed pollen (filter cake) was freeze-dried in an F. J . Stokes Corp. (Philadelphia, Pa.) Model 338P dryer. The freeze-dried pollen was then extracted with about 114 L of 2-propanol in the Hamilton kettle and the slurry pumped to the Sparkler
This article not subject to U S . Copyright. Published 1978 by the American Chemical Society
