Action of Mineral Ion Exchange Resins an Milk Constituents C. W. GEHRKW AND E. F. ALLMY The Ohio State University, Columbus, Ohio w h e n 0.100 N solutions of hydrochloric, phosphoric, or citric acids are subjected to anion exchange using DeAcidite, the order of adsorption was phosphoric > citric > hydrochloric; but when using binary or ternary mixtures totaling 0.100 N for the acids present, the order changed to hydrochloric > phosphoric > citric. Amberlite IR-4B (anion exchanger) adsorbed monosodium dihydrogen phosphate more effectively than it did disodium hydrogen phosphate. A solution whose concentration approximates the ionic composition of cheddar cheese whey was passed
through beds of Zeo-Karb-H (cation exchanger) and DeAcidite in series. The calcium and magnesium ions were completely removed. The adsorption affinity of the cations was Ca++ > Mg++ > K + > Na+ ion. The chloride and phosphate ions were effectively removed. The chloride ion was preferentially adsorbed. Zeo-Karb-€I effectively adsorbed urea, creatine, and creatinine; DeAcidite, an anion exchanger, did not. The cation and anion exchangers used did not remove lactose from a solution at different pH values.
T
change system waR used by Newkirk and Handelman (17)in a pilot plant refinery for producing dextrose by the hydrolysis of starch. Block ( 4 ) reported an application of ion exchangers to the removal of basic amino acids derived from proteins, and Cannan ( 6 ) described a method for the quantitative separation of the dicarboxylic amino acids from protein hydrolyzates. Various laboratories have been experimenting with the properties of the many new synthetic ion exchange materials when used to treat milk. However, it was believed that some fundamental studies should be made on the action of typical anion exchanger and cation exchanger resins with simple solutions of the known major inorganic milk constituents, lactose, and nonprotein nitrogenous substances at such concentrations as they normally appear in milk. Although this work was done with exchangers of the Amberlite and Permutit types, any of the anion and cation exchangers now available, of equivalent characteristics, could be expected to act in similar fashion to the types used here. However, in this rapidly developing field many new and special purpose exchange materials are becoming available; these would require separate study under the conditions used here before conclusions could be drawn as to their characteristics. Thus Amberlite IR-4B is characterized by special high affinity for phosphoric acid when compared to De-Acidite or to other types of Amberlite or other anion exchange resins of different characteristics. Complete general characteristics of various ion exchange materials are now available from the manufacturers.
HE process of ion exchange may be defmed as a reversible interchange of ions between the liquid and solid phases. This interchange is governed by the law of mass action according to 3onie investigators, but others regard it as a typical adsorption isotherm phenomenon. Boyd et al. ( 5 ) hold that the process should be called "chemisorption," as it possesses characteristics of both adsorption and chemical equilibrium. The newer synthetic organic ion exchangers have been used in scoi es of industrial and laboratory applications. Sussman and Mindler ( 2 0 ) have classified the applications of the ion exchange resins in terms of five major ion exchange reactions. Synthetic ion exchange materials have been described by numwous investigators; typical reports are those of Harrison, Myers, and Herr (11) and Rlvers, Eastes, and Urquhart (26). These substance8 may be grouped into two major divisionscation active and anion active. An early paper on the application of the mineral ion exchange principle to a food product was that of Lyman, Browne, and Otting (16). They used a base exchange silicate to alter the calcium and phosphorus content of milk. Josephson and Reeves ( 1 2 ) found that when mineral ion exchange treated milk was added to evaporated milk it was capable of stabilizing the evaporated product against coagulation during sterilization at 240" F. for 15 minutes. Mineral ion exchange milk was found to be effective in stabilizing milks exhibiting a wide range of instability to heat. Almy and Garrett ( 1 ) reported that on the complete demineralization of sweet cheese whey the percentages of calcium, phosphorus, and chlorine in the original whey (0045% Ca, O & B % P, 0,114% C1) were decreased to 0,002% Ca, 0.004% P, and 0.003% C1 in the ion exchange whey effluent. Also, removals for calcium from cation exchanged skim milk start at 83 and drop eo 39% as thc ion exchange run progresses, whereas the adsorption for phosphorus remains constant at 7 to 8%. Otting (18) discusses the problems which were surmounted in the application of the mineral ion exchange principle in milk products and the equipment and procedure to be used. Numerous applications of the ion exchange principle to other food products have been made in the last few years-for example, Legault et al. ( 1 4 ) recovered tartaric acid from winery still slop by exchange adsorption on an anion exchanger in the chloride form; Ham and Stadtman ( 1 0 ) used ion exchange resins to separate and identify types of compounds involved in browning of apricot concentrates. A triple-pass, countercurrent ion ex1
Present address, University of Missouri, Columbia, hlo.
EXPERIMENTAL
This investigation was undertaken to learn the action of mineral ion exchange resins on simple solutions of the major anions found in milk and for solutions of lactose and nonprotein nitrogen by: 1. Determining the adsorption characteristics of such exchangers in removing the various ions from less complicated solutions. 2. Studying the effect of the presence of one ion or molecule on the adsorption of another. 3. Determining the extent of the adsorption of lactose by these exchangers a t different p H values. 4. Studying the changes in the composition of solutions containing nonprotein nitrogen. 5. Observing the effeet on the composition of solutions containin different phosphate ions. 6. %earning what action these synthetic exchangers have on the composition of a synthetic whey solution whose ionic composition approximates that of cheddar cheese whey.
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November 1950
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
The mineral ion exchange materials selected as typical and used in this investigation were Zeo-Karb-H, De-Acidite, and Amberlite IR-4B. The general procedure followed has been reported previously by the authors (9); it consisted of passing the Rolution to be treated downflow through a column of the ion exchange material contained in a glass tube. The depth of column and rate of passage were determined experimentally for each type influent to be processed. ION EXCHANGE CHARGES.Amberlite IR-4B was selected for use in this study because it is a resin with a high capacity for phosphate ions. Zeo-Karb-H and De-Acidite were selected as a representative pair of commercial cation and anion exchange resins. The column characteristics and charges used were as follows: The weight of Zeo-Kerb-H (cation exchanger) put into one column was 97.592 grams; the column was 90 cm. long and allowed for 100% bed expansion during backwaahing. This column waa prepared for use in comparing anion and cation exchangers with respect to their action on solutions of lactose and nonprotein nitrogen. A De-Acidite (anion exchanger) column, 86.886 grams of the moist resin, was prepared. Another column containing 132.350 grams of Amberlite I R 4 B (anion exchan er) waa also prepared. In each of the above columns the bactwashed and drained volume (Band D)of the bed was 200 ml. The beds were each initially conditioned by two cycles of preliminary exhaustion and regeneration with appropriate solutions. BREAK-THROUGH POIIVT.The break-through point (B.T.P.) designated as that point a t which the concentration of the ioii or molecule in the effluent reached a value which was 6% of the initial concentration and 95% was still being adsorbed by the exchanger. The volume of solution passed through the bed to the B.T.P. times the normality of the solution equals the milliequivalents adsorbed to the B.T.P. OPERATING DATA. Approximately 2OOO d.of the influent solution were passed into the exchanger at the rate of 50 ml. per minute. The effluent was collected in 100-ml. samples and quantitatively analyzed for the ion or molecule in the solution. The exchanger was then backwashed with distilled water for 10 minutes a t a flow rate which gave a 50% bed expansion. The bed was regenerated downflow with 280 ml. of 0.750 N sodium carbonate at an introduction rate of 4.5 ml. per minute. The regeneration waa followed by a slow rinse downflow with 200 ml. of distilled water at 4.5 ml. per minute, then a fast rinse a t normal downflow of 60 ml. per minute until the effluent alkalinity was such that 10 ml. of effluent showed an acid reaction to methyl orange on the addition of 1 drop of 0.10 N hydrochloric acid. The exchanger was thus prepared for the next test h. The gaa pockets that formed in the bed during regeneration of the De-Acidite and Amberlite IR-4B exchangers were effectively removed by backwashing or by thrusting a long piece of glass rod down into the bed. SOLUTIONSSTUDIED, Solutions of the following ions and molecules were passed through the exchangers and the concentration of each present in the effluent waa quantitatively determined. The solution concentrations were selected to give approximately the concentration of the respective ions or solutes found in milk or whey. Through De-Acidite column: WUR
1. Solutions of 0.1000 N hydrorhloric, phosphoric, and citric acids. 2. A 0.1OOO N solution of binary mixtures of these three acids (each acid being present in 0.050 N concentration), 3. A 0.1OOO N ternary solution containing the three acids (each acid being present in 0.033 N concentration). 4. A 5 7 lactose solution at p H 6.0 and 8.5. 5. A sofution which approximates the ipnic composition of cheddar cheese whey+(Figure2 shows cqmposition). 6. A 0.6% solution of urea, creatine, and creatinine (each being present in 0.20% concentration).
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Through Amberlite IR-4B column: 1. A 0.1368 N solution of phosphoric acid. 2. A 0.1000 N solution as an acid of disodium hydrogen phos-
phate.
3. A 0.100 N solution as an acid of monosodium dihydrogen phosphate.
Through Zeo-Kerb-H column: 1. A 5% lactose solution at p H 3.7 and 10.0. 2. A solution which approximates the ionic composition of
cheddar cheese whey (concentration of solution given in legend of Figure 2). 3. A 0.6y0 solution of urea, creatine, and creatinine (each being present in 0.20%concentration). QUANTITATIVE CHEMICAL PROCEDURES. The moisture content of the ion exchange materials was determined by drying 3 grama of the substance a t 105" C. for 3 hours. The pH of the effluent was determined by means of the Leeds and Northrup glass electrode instrument with No. 7661-A1 assembly. The total acidity of the effluent was obtaincd by titrating a 25-ml. aliquot with 0.1000 N sodium hydroxide to the first faint pink color using thymolphthalein aa the indicator. This indicator changes color a t the second ionization stage of phosphoric acid. Calcium was determined on an aliquot of the effluent as described in Kolthoff and Sandell (13). Magnesium was determined by the titan yellow procedure as described by Sandell (19) except that the Coleman Model 10s spectrophotometer was employed using a wave length of 550 mp and a previously prepared concentration-transmittance curve. Sodium was determined by the magnesium uranyl acetate precipitation method as described (8). Potassium was determined by the perchloric acid alcohol precipitation method as described in Fales and Kenny (8). Phosphorus was determined by a method adapted for the photoelectric colorimeter from the colorimetric procedure described in "Cereal Laboratory Methods" (9). The Coleman Model 10s spectrophotometer was used. The citric acid content of the effluent waa calculated indirectly from the data obtained for the total acidity. The hydrochloric and phosphoric. acid content of the effluent was quantitatively determined, the citric acid content then being obtained by difference. The chloride ion concentration was determined by the Mohr titration method as outlined in Kolthoff and Sandell ( 19 ) . The lactose concentration was determined by means of the quartz wedge saccharimeter, Bates type. The nonprotein nitrogen was determined by the Kjeldahl procedure as described (9). RESULTS
Figure 1 presents data for the adsorption of acids by an anion exchange resin, De-Acidite, from single, binary, and ternary solutions containing hydrochloric, phosphoric, and citric acids. Duplicate runs gave close agreement; the figures cited are typical values of various runs. When 0.1000 N (10 me. per 100 ml.) solutions of the acids were singly passed through the exchanger, 110 me. of hydrochloric acid, 130 me. of citric, and more thrtn 200 me. of phosphoric acid were removed to the B.T.P. The resin effected a nearly complete removal of the acids to the B.T.P. after which the acid concentration in the effluent increased sharply. All the hydrochloric acid was adsorbed from the first 2000 ml. of a binary mixture containing 5 me. of hydrochloric and 5 me. of 'citric acid per 100 ml. of influent. The adsorption of citric acid to the B.T.P. was 40 me., and more than 100 me. of hydrochloric acid were removed (Figure 1D). As shown in Figure lE, in a binary mixture containing 5 me. of each acid per 100 ml., 170 me. of phosphoric were adsorbed
INDUSTRIAL AND ENGINEERING CHEMISTRY
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z2t
20
0 HYDROCHLORIC
H
ACID
CITRIC A C I D PHOSPHORIC A C I D NOT REACHED
U B.T.P.
F
G
Figure 1. Adsorption of Acids by Anion Exchange Resin from Single, Binary, and Ternary Solutions A = hydrochloricacid, 100 me./liter B = citric acid, 100 me./liter C = phosphoricacid, 100 me./liter D = binary solution of hydrochloric and eitric acids, 50 me. of each perliter E = binary solution of phosphoric and citric acids, 50 me. of each per liter F = binary solution of hydrochloric and phosphoric acids, 50 me. of each per liter G P ternary solution of hydrochloric, phosphoric, and citric acids, 33.3 me. of each per liter Influent flowrate, 50 ml./min.
Vol. 42, No. 11
During the first part of the run the effluent was slightly acidic; it turned alkaline after 800 ml. of effluent were obtained and remained alkaline until 1500 ml. of efRuent were collected when it again turned slightly acidic for the remainder of the run. The calcium and magnesium ions were completely adsorbed from the 1700 ml. of solution passed through the columns. The number of milliequivalents of calcium and magnesium ions removed to the B.T.P. exceeded 35.7 and 20.4, respectively, and 36.9 me. of potassium and 18.6 me. of sodium ions were adsorbed to the B.T.P. (Figure 2B). The relative order of adsorption of the cations from the synthetic whey solution was found to be C a + + > M g + + > K + > N a +ion. To the B.T.P., 68 me. of chloride ions and 44.2 me. of phosphorus as phosphate ion were removed from the synthetic whey by the anion exchanger (De-Acidite, Figure 2 0 ) . Figure 2A and 2C show that once the B.T.P. for a particular ion was reached, its concentration in the effluent from that point on increased rapidly and in some cases exceeded the initial concentration. The concentration of the chloride and phosphate ions in the effluent of the synthetic whey solution leveled off at about 3 me. per 100 ml. after the passage of 1400 ml. of solution and a t no time exceeded the initial influent ion concentration. The initial sodium ion concentration was 2.33 me. per 100 ml., and after the passage of 900 ml. of solution through the columns the concentration exceeded this value. For the potassium ion the initial concentration was 3:52 me. per 100 ml. This concentration was exceeded after the passage of 1500 ml. of synthetic whey. Amberlite IR-4B, a resin with a high capacity for phosphatt: ions, was used to study the removal of the monobasic and dibasic sodium phosphates and phosphoric acid. The adsorption of the
L
:
51
i
A
3
24LL
W
i
= 3-
0
to the B.T.P., whereas only 85 me. of citric acid were removed. After the B.T.P. was reached the citric acid concentration in the effluent increased to a maximum, then decreased as the phonphoric acid increased in concentration in the effluent. On passage of a binary solution containing 5 me. per 100 ml. of hydrochloric and phosphoric acids through the resin bed, 105 and 100 me. of acid, respectively, were adsorbed to the B.T.P. (Figure 1F). The hydrochloric acid concentration in the effluent increased to 0.33 me. per 100 ml. after 2.1 liters of solution were passed through the exchanger; it then decreased in value to 0.03 me. per 100 ml. after the passage of 2.5 liters of binary solution. The hydrochloric acid was completely removed from a ternary solution containing 3.33 me. per 100 ml. each of phosphoric, citric, and hydrochloric acids. The milliequivalents of acids removed to the B.T.P. were: hydrochloric acid, more than 99; phosphoric acid, 79; and citric acid, 46 (Figure 1G). For the binary mixtuies of phosphoric, citric, and hydrochloric acids the adsorption affinity was found to be hydrochloric> citric, phosphoric>citric, and hydrochloric>phosphoric. The order of adsorption for tho ternary system of acids was hydrochloric>phosphoric> citric. A solution was prepared whose concentration is given in the legend of Figure 2. This solution approximates the ionic composition of cheddar cheese whey. The adsorption of the ions in this solution by Zeo-Karb-H and by De-Acidite columns arranged in series was studied quantitatively to determine the effect of ion exchange materials on a more complex solution. The experimental results are preeented in Figure 2.
0 \
EZ-
50 LL
0 1-
d W
z 0'
1 4 8 12 16 20 VOLUME OF EFFLUENT IN ML.X 100
CL- ION W
a 0 W
Figure 2. Adsorption of Ions by Zeo-Karb-H and DeAcidite Columns, in Series, from Synthetic Cheddar Cheese Whey Concentration of influent solution in me. per 100 ml.: Ca++ion, 2 10. M g + + ion, 1.201 K + ion, 3.52. Na+ ion 2.938 C1- ion, 5.92; 4:02'me. of phosphorus added as kHaPO4. influent flow rate 50 ml./min.; Cat+ and M g + + ions were completely adaorbed from first 1700 ml. of effluent
November
1950
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
monosodium dihydrogen phosphate was^ greater than the adsorption of the disodium hydrogen phosphate. A 70% removal of the dihydrogen salt w a effected ~ from the first 400 ml. of effluent. T h e adsorption gradually decreased to 32% removal of the salt after 1700 ml. of the solution were passed through the IR-4B bed, and the adsorption leveled off a t this value. For the monohydrogen salt a 30% removal was obtained from the first 300 ml. of effluent; this gradually decreased to 5% removal after the passage of 1600 ml. of solution through the exchanger. The phosphoric aoid was Completely adsorbed from 2000 ml. of a 0.1368N influent solution. The B and D volume of the bed changed significantly only with the phosphoric acid; B and D start, 208 ml., and end, 225 ml. The lactose in 5% solutions of lactose a t initial pH values of 8.70and 6.90 w a not adsorbed when passed through a bed of DeAcidite. The effluent pH remained constant a t 8.30 and 5.90, respectively. The lactose in a 5 % solution of lactose at pH 3.70 was not removed by Zeo-Karb-H, and Zeo-Karb-Na did not adsorb the lactose from a 5%solution at p H 10.0, De-Acidite did not adsorb urea, creatine, and creatinine from a solution the concentration of which was 0.2% in respect to each component. When this solution was passed through a bed of Zeo-Karb-H these substances were completely removed from the first 400 ml. of effluent, and after 1600 ml. of effluent were obtained t h e removal effected by the exchanger was still greater than 50%. The pH of the solution remained constant at 3.70. DISCUSSION
When 0.1OOO N solutions of hydrochloric, citric, and phosphoric acids were passed singly through a column of De-Acidite, the adsorption affinity was found to be: phosphoric>citric> hydrochloric acid. The resin effected a nearly complete removal of the acids studied up to the B.T.P., after which the concentration of the acid in the effluent increased rapidly. The adsorption affinity of De-Acidite for 0.1OOO N binary and ternary solutions of these three acids was found to be: hydrochloric>phosphoric>citric acid. When the acids were passed through the exchanger singly the acid with the highest ionization constant was adsorbed least, whereas when the binary and ternary solutions were passed through the column the stronger acids had the greater adsorption affinity. The order of adsorption was in the order of the magnitude of the ionization constant. This, in the mixtures, is perhaps due to a repression of the ionization of the weaker acids by the stronger acids, according to the common ion effect, and results in more unionized molecules of the weaker acids. These are not adsorbed by the resin exchanger to the same extent as the stronger acid. Exchange adsorption is dependent on other factors, such as forces binding the ions to the lattice, total concentration of the ions, accessibility of the lattice ions, and solubility effects. Boyd et aZ. (6) showed that adsorption affinities were determined chiefly by the magnitude of the charge and the hydrated radius of the ions in solution. Some of the ions in the test solutions that would be competing for positions on the exchanger would be: C1-, HPO,’, and H-citrate. A consideration of the results obtained indicates that the cations present in a complex solution, such aLi synthetic whey, that appear to be adsorbed from the effluent are actually removed during the first part of the exchange run and then released later by the regeneration effect, according to the law of mass action, of the other cations which are in the solution and which are preferentially adsorbed. The chloride ion was preferentially adsorbed from the synthetic whey. The removal of chloride and phosphate followed a pattern similar to that found for the removal of these anions from less complicated solutions. From a knowledge of the ionic composition of a solution to be treated by ion exchangers the adsorption pattern could be predicted. This would be of great
2347
value in setting up experimental problems on the ion exchanger treatment of various substances found in solution. Amberlite IR-4B adsorbed the monosodium dihydrogen phoaphate more effectively than it did the disodium hydrogen phosphate. The phosphoric acid solution was completely adsorbed. A 70% removal of the dihydrogen salt was effected in the first 400 ml. of effluent, whereas for the monohydrogen salt a 30% removal was obtained. The p H of the solution was found to be important in phosphate removal by IR-4B. As the p H of the solution changes the relative proportion of the different kinds of phosphate ions present also changes, and thus the adsorption by the resin of phosphate ions is dependent on the pH of the solution. Zeo-Karb-H completely adsorbed urea, creatine, and Creatinine from the first 400 ml of a 0.6% solution of these materials, and a 50% adsorption still occurred after 1600 ml. of the solution were passed through the bed. These substances were not adsorbed by De-Acidite. From the basic nature of urea, creatine, and creatinine the adsorption mechanism should be similar to that for the amino acids a6 explained by Englis and Fiess (7). ACKNOWLEDGMENT
,The authors express their appreciation to the Resinous Products and Chemical Company, Inc., Philadelphia, Pa., to the Permutit Company, New York, N. Y.,and to the Infilco Corporation, Chicago, Ill., who supplied the exchangers. LITERATURE CITED
(1) Almy, E. F., and Garrett, 0. F. (to M. and It. Dietetic Laboratories), U. 8.Patent 2,477,558(Aug. 2, 1949). (2) American Assoc. Cereal Chemists, 110 Expt. Sta. Hall, Lincoln, Neb., “Cereal Laboratory Methods,” 1941. (3) Assoc. Official Agricultural Chemists, 540 Benjamin Franklin Station, Washington 4,D. C., “Official and Tentative Methods of Analysis,” 6th ed., p. 122 (1945). (4) Block, R.J.,Proc. SOC.Ezptl. Bid. M e d . , 41,352 (1942). (5) Boyd, G.E., Schubert, J., and Adamson, A. W., J. A m . Chem. SOC.,69,2818-29 (1947). (6) Cannan, K. R., J . Biol. Chem., 152, No.2,401 (1944). (7) Englis, D. T.,and Fiess, H. A., IND.ENG.CHIM.,36, 604-6 (1944). (8) Fales, H.A,, and Kenny, P.,“Inorganic Quantitative Analysis,’’ p. 568, New York, D. Appleton-Century Co., Inc., 1939. (9) Gehrke, C. W.,and Almy, E. F., Science, 110,556-8 (1949). (10) Haas, V. A.,and Stadtman, E. R., IND.ENC.CHEM., 41,983-5 (1949). (11)Harrison, J. W.E., Myers, R. J., and Herr, D. S., J . Am. Pharm. ASSOC., Sei. Ed., 32,121-8 (1943). (12) Josephson, D.V.,and Reeves, C. B., J . Dairy Sci., 30, 727-46 (1947). (13) Kolthoff, I. M.,and Sandell, E. F., “Quantitative Inorganio Analysis,” rev. ed., p. 569, New York, Macmillan Co., 1943. (14) h g a d t , R.R.,Nimmo, C. C., Hendel, C. E., and Notter, G. K., IND. ENQ.CHEM.,41,466-71 (1949). (15) Lyman, J. F., Browne, E. H., and Otting, H. E., Ihld., 25, 1297-8 (1933). (16) Myers, R.J., Eastes, J. W., and Urquhart, D., Ihid., 33, 1270-5 (1941). (17) Newkirk, T.H.,and Handelman, M., Ibid., 41,452-7 (1949). (18) Otting, H.E., Ibid., 41,457-9 (1949). (19) Sandell, E.B., “Colorimetric Determination of Traces of Metals,” New York, Interscience Publishers, Inc., 1944. (20) Susaman, S., and Mindler, A. R., Chem. Inds., 56, 789 (1945). RECEIVED October 12, 1949. Presented before the Division of Agricultural SOCIETY, Atand Food Chemistry, 116th Meeting, AMERICANCHEMICAL lantio City, N.J. The data in this artiole are a part of dissertation presented by C. W.Gehrke in fulfillment of the requirements for the degree of dootor of philosophy, graduate sohool, Ohio State University.
