COMPLEMENTARY REFINING WITH PULVERULENT MIXTURES
OF POLAR RlESlNOUS ADSORBENTS, ACTIVATED CARBON, AND INORGANIC ADSORBENTS B E R N A R D
N.
D I C K I N S O N
A N D
H A R O L D
E .
B A R R E T T ,
J R . '
Resinous Products Diuision, Diamond Shamrock Chemical Co., Redwood City, Calif. 94064 Properly selected combinations of finely divided adsorbents consisting of polar resinous adsorbents, activated carbon, and/or inorganic adsorbents complement each other in purifying substrates such as sugar solutions, water, a n d organic liquids by the removal of color, color precursors, and haze. This mutual enhancement of the refining powers of the individual adsorbents yields a purification much greater than would be expected from considering the refining capacities of the separate adsorbents alone. Micronized ion exchange resins constitute a n iimportant class of polar resinous adsorbents.
THEremoval of color from crude sugar solutions or from water by adsorption on granular resins is well known. Reports have been published on the use of columns of particulate ion exchange and adsorbent resins employed cyclically to decolorize beet sugar and starch-hydrolyzate solutions (Abrams and Dickinson, 1949) and water (Jayes and Abrams, 1966). Siamberg (1963) reported the chemical structures and properties of granular resinous color adsorbents. Granular resinous adsorbents used in columnar operations must be regenerated by chemical means. Usually regeneration is incomplete, leaving an increment of irreversibly adsorbed impurities after each cycle. This causes a gradual decline in bed capacity, which creates difficulties in scheduling plant production. Mixtures of resinous and natural adsorbents which would exhibit high refining capacities a t low dosage levels are therefore of interest. Such mixtures would not be regenerated. Little has been published on mixtures of micronized adsorbents. Colloidal bentonite has been employed in conjunction with activaied carbon to clarify and decolorize sugar solutions (GraR and Pittman, 1941). Mixtures of diatomaceous earth and cation exchangers of standard mesh sizes have been claimed for wine clarification and stabilization (van Dyk, 1952). The present effort relates to the complementary refining benefits resulting from the use of micronized ion-exchange and adsorbent resins admixed with micronized natural adsorbents such as activated carbon and, or inorganic adsorbents. Activated carbon is a very efficient adsorbent, but it is subject t o the law of diminishing returns. Hence, carbon dosages become exclessive when the limit of complete impurity removal is to be approached. Polar resinous
' Deceased.
adsorbents complement the action of carbon especially by adsorbing the refractory impurities more effectively and reducing the carbon requirements materially. Color bodies, for example, are frequently ionic and amenable to selective adsorption when the polarity of the resinous adsorbent results from weak- or strong-base groups. Experimental
Procedure. T o substrates weighed out in 40-ml. vials were added the desired amounts of adsorbents whose moisture contents had been found by drying for 16 hours under a vacuum of 2 mm. of Hg in the presence of a desiccant. This allowed the establishment of weight ratios of bone-dry adsorbents to solids in sugar solutions or to substrate for water or organic liquids. Adsorbents were dispersed in the sealed vials by magnetic stirring for 5 minutes. The vials were then rotated in a constant temperature bath a t the rate of 88 r.p.m. Typically, the tumbling time was 30 minutes and the bath temperature 60" C. Immediately after tumbling, the sealed vials were transferred to an ice bath and chilled for 10 minutes to deactivate the adsorbents-substrate system, which was then promptly filtered through a Whatman No. 42 paper fitted to a filter cone. Filtration time was 15 to 20 minutes. Filtration without chilling led to a detectable drift in final color of the substrate compared to the deactivated system. On the other hand, final color of substrates filtered at intervals from equivalent equilibrated systems held a t ice bath temperature was stable over a 1-hour period. Light absorbed by the filtrate was measured in a 10-cm. cell at 450 mp, which gave color of soluble chromophores plus apparent color from light lost from scattering by haze. The latter was determined by measuring degree of absorbance a t 600 mp. Subtraction of A 6 0 0 from Asso gave the color due t o soluble chromophores. The pH VOL. 8 NO. 2 JUNE 1 9 6 9
199
Table I. Principal Adsorbents Used in Tests“
Adsorbent
Description
LAD-500
Phenol-formaldehyde-polyethylene-polyamine condensate. Total capacity = 9.1 meq. i dry g. Chloride form LAD-501 Epichlorohydrin-polyethylene-polyamine condensate. Total capacity = 10 meq./dry g. Chloride form LAD-502 Strong-base anion exchanger, Type I, low crosslinked. Exchange capacity = 4.2 meq./dry g. Chloride form. LAD-503 Phenol-formaldehyde condensate LAD-504A Phenol-formaldehyde-ammonia condensate. N = 4.5% LAD-504H Same as LAD-504A with N = 5.lC: Same as LAD-504A with N = 6.5% LAD-504M LAD-505 Strong-basesulfonium anion exchanger. Exchange capacity = 3.4 meq./dry g. Chloride form Urea-formaldehyde-ammonium condensate LAD-506 Strong-acidcation exchanger, 8% DVB. LAD-507 Sodium form LAD-508 Melamine-formaldehyde condensate LAD-509 Strong-base anion exchanger, Type 11, standard. Exchange capacity = 4 meq./dry g. Chloride form LAD-510 Experimental weak-base anion exchanger containing imidazoline groups. Total capacity = 8 meq./dry g. Chloride form LAD-511 Melamine-guanidine-formaldehydecondensate LAD-512 Guanidine-formaldehyde condensate LAD-513 Nitrated styrene-divinylbenzenecopolymer (8% DVB) LAD-516 Acid-treated natural silicious ore LAD-527 Modification of LAD-504M LAD-531 Modification of LAD-500 Darco S-51 Commercial activated carbon Nuchar CEE Commercial activated carbon Nuchar C-190N Commercial activated carbon DEAE-Sephadex Commercial crosslinked dextran activated with amines Britesorb 30 Commercial adsorptive magnesium silicate Commercial gel form Caa (POA a LAD-504A, LAD-504H, LAD-504M, LAD-508, LAD-51 1, and LAD-512 are primarily adsorbents with wry limited weak-base capacities: 1.0 to 1.5 meq,/dry g. p K values 4 to 5.5 lisually they i w e employed in chloride form.
of the treated substrate was adjusted to that of the raw substrate to eliminate the indicator effect of chromophores. Once ambient-Le., existing-color had been found as indicated, color precursors were estimated by heating the filtrate a t 100”C. for 1 hour and remeasuring the subtraction of Am from A4;0. This accelerated test was intended to simulate changes in refined corn sirups which may be stored up to 8 weeks a t 38O C. Adsorbents Used. The adsorbents used are listed in Table I. Duolite LAD code numbers are shown for the polar resinous adsorbents. Particle sizes fell in the 1- to 100micron range, the peak occurring between 20 and 40 microns. Definitions. PRINCIPAL ADSORBENT. I n complementary refining, usually one species constitutes the major component and is conveniently designated as the principal adsorbent. Often, but not necessarily, it is a natural adsorbent. COMPLEMENTARY ADSORBENT, the minor component or components. 200
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
C,, C F , AND C F F ,differences in absorbances a t the two wavelength (AGO-AMO) values for the raw substrate, treated substrate measured for ambient color, and treated substrate measured for color precursors, respectively. FREUNDLICH ISOTHERMS. For this application this longestablished method of representing equilibrated adsorptive systems takes the form of plotting logarithms of C F or CFFus. the logarithms of (C, - CF)/rn or (C, - C F F ) / m ratios, respectively, where n is the total adsorbent dosage as per cent on solids for solutions or on substrate for water and organic liquids. Plots fell on straight linesa straight-line plot verified the validity of the experimental results. Strictly speaking, Freundlich isotherms are derived from completely equilibrated systems which usually require hours of contact time to attain. However, contact times exceeding 1 hour are not practical industrially. Thus, in general, the 85 to 95% approach to equilibrium achieved with 30 to 60 minutes’ contact times was adequate for this study. Standard Curves. These were isotherms prepared by measuring CF or CFFa t various dosages of the principal adsorbent with the substrate in question under the equilibrating conditions used. Complementary Effect and Relative Efficiency. By comparing the standard curve with the corresponding complementary isotherm, the ratio of dosage of principal adsorbent used alone to dosage of principal adsorbent employed in a complementary mixture needed to achieve the same CF or CFI.value could be found. This ratio was deemed the “complementary effect.” The ratio of dosage of principal adsorbent used alone to dosage of complementary mixture was defined as “relative efficiency.” Results and Discussion
isotherms. Figure 1 gives a representative standard carbon isotherm for ambient color removal, the isotherm for the LAD-531 employed, and the corresponding complementary isotherm for an acid-enzyme hydrolyzate of corn starch having 47.4% solids and a pH of 4.0. Equilibrating conditions were 30 minutes a t 60’C. LAD531 was maintained a t 1 0 7 of the total dosage. The basic data and the derived complementary effects and
I
ISOTHERM FOR LAO-531
t
! I I I
oL I
ISOTHERM FOR
E
MREHT / / COMPLEMENTARY M
NUCHAR CEE FoF
003-
n I, 0 01
1
I
I
I
003
005
0.1
0 2
cF Figure 1. Carbon, LAD-531, and complementary isotherms for a corn sirup
Table II. Results of Treating an Acid-Enzyme Hydrolyzate of Corn Starch with Varying Dosages of Carbon, LAD-531, and a Complementary Mixture
Per Cent Adsorhents Nuchar
LAD-531
CF
0 (blank) 0.3 0.5 0.8 1.o 2.0 0 0 0 0 0 0 0 0.27 0.54 0.72 0.90 1.26
0 0 0 0 0 0 0.03 0.05 0.1 0.2 0.5 1.o 1.8 0.03 0.06 0.08 0.10 0.14
0.273 0.103 0.083 0.062 0.054 0.036 0.185 0.156 0.115 0.098 0.084 0.077 0.071 0.075 0.045 0.035 0.027 0.0215
Compkmentay Effect
Relative Efiiency
... ...
...
... ... ...
... ... ... ... ... ...
... ...
...
... ...
...
... .
.
I
2.10 2.62 2.94 3.33 3.83
80 DARCO 5-51, I TO 8 0 MICRONS
70
-
60
-
...
... ... ... ...
...
1.89 2.39 2.65 3.00 3.45
0
1
1
I
2
4
6
1
8
1
10
I 12
EQUILIBRATING TIME I N HOURS A T 80' relative efficiencies are shown in Table 11. CF on the blank was found by treating the substrate under the specified conditions in the absence of adsorbents. The linear portion of the LAD-531 isotherm is steepi.e., no great refining benefit accrues from increasing dosage. Above about 0.2% LAD-531-i.e., the dosage range used in the complementary mixtures- the isotherm begins to deviate from the linear curve because color removal was less than would be projected from an extrapolation of the linear part of the isotherm. Nevertheless, such light dosages added to carbon gave refining results equivalent to those secured with much larger dosages of carbon used alone. For example, 0.03% LAD-531 used alone gave CI. = 0.185, while from the isotherm 0.27'7 carbon used alone would give C F = 0.109. The two used together to form a total 0.3% dosage gave CF = 0.075, which corresponds to 0.57% carbon alone or 1.32% of LAD-531 alone. T h u s 0 . 3 7 additional carbon or 1.29% LAD-531 would be required to perform the refining achieved by the complementary adsorbent. At the 1.4% Complementary dosage level, 3.56% extra carbon alone or a massive additional dosage of LAD-531 alone would be needed to yield the value of C F = 0.0215 secured. So evidently there was a mutual enhancement of the refining powers of the individual adsorbents. Using the isotherms of Figure 1, complementary CI; values fairly close to the ones measured can be calculated from the formula:
c, - CF (I-
CI
1
from LAD-531 alone x ( C Ffrom carbon alone)
e.g., CF calculated = 0.074 us. C F measured = 0.075 for carbon = 0.27% and LAD-531 = 0.03% and CF calculated = 0.0195 us. CIFmeasured = 0.0215 for carbon = 1.26'r and LAD-531 = 0.14%. This indicated that when used in complementary reactions the LAD-531 adsorbed about the same per cent of chromophores left by the carbon as from the raw substrate.
1
I4
C
Figure 2. Influence of particle size of LAD503 on rate of approach to equilibrium
Data of Table I1 show complementary effect to increase with complementary dosage, linearly up to the value 3.33. Effect of Particle Size. Figure 2 shows per cent of ambient color removed us. equilibrating times for various particle size distributions of LAD-503. The curve for Darco S-51 is also shown. 'The substrate was process greens, the molasses spun off dextrose crystals derived from starch hydrolyzates. Complementary Effects. 'Table 111 lists the complementary effects secured in a number of cases on ambient color removal. These data indicate the wide range of adsorbent-substrate combinations for which complementary action exists. Percentages in Table 111 refer to weight ratios of bonedry adsorbents to dry solids in substrate for sugar solutions or to the total substrate for other liquids. Equilibrating conditions were 30 minutes and 60°C. Examples in Table I11 are divided into sections for the various substrates--- process greens, acid-enzyme hydrolyzate of corn starch, refined beet sugar melt, crude dicyclopentadiene, natural pond water buffered a t p H 7, and crude monosodium glutamate. I n the acid-enzyme hydrolyzate section, the principal adsorbent was fixed but its dosage varied, while both the species and dosage of complementary adsorbent varied. As noted in Table 11, total complementary dosage has an effect, but the main cause of changes in complementary effect seemed to come from the different polar groups in the various species of complementary adsorbents and their reactions with the chromophores of the substrate. For the refined beet sugar series, only the complementary species varied and the controlling factor appeared to be the nature of polar group and its reaction with the chromophores of the substrate. I n the natural pond water sequence, species of both principal and complementary adsorbent and their dosages were varied. However, differences in the properties of the carbons employed are not great. Again the nature of the complementary polar group seemed paramount. VOL. 8 N O . 2 JUNE 1 9 6 9
201
Discrete (or macro) porosity in the complementary adsorbent seems to play a minor role in complementary refining. Table IV gives the complementary effect for both ambient color ( C F ) and color precursors found by measuring CFF after heating the CF-filtrate for 1 hour a t 100" C. An acid-enzyme hydrolysis product of a corn starch slurry treated for 30 minutes at 60°C. with 0.5% Nuchar C E E and 0.05% LAD-504A gave a complementary effect of 3.6 for ambient color and of 18 for haze. The latter was established by measurements a t 600 mp on Nuchar C E E alone to make the standard isotherm and on the complementary mixture. Complementary effects for both ambient color and color precursors were measured using buffered raw cane sugar melts of 52" Brix which had been clarified by bone char filtration. Systems were equilibrated for 30 minutes a t
Table 111. Complementary Effect on Ambient Color for Various Substrates"
Principal Adsorbent
Complementary Adsorbent
Substrate Process greens
2.41
Xuchar CEE, 17 c
LAD-504A, 0.15
3.0
Nuchar CEE, 0.8'5
LAD-505, 0.045
Acid-enzyme hydrolyzate of corn starch Acid-enzyme hydrolyzate of corn starch Acid-enzyme hydrolyzate of corn starch
LAD-500, 0.15 LAD-508, 0.15 Ca?(PO,), gel, 0.1%
Refined beet sugar melt Refined beet sugar melt Refined beet sugar melt
6.00
Nuchar C-190N, 17c
LAD-504H, 0.17
Crude dicyclopentadiene
2.1
Nuchar CEE, 15c Nuchar CEE, 0.4'0 Nuchar C-lgON, 0.5c-i Darco S-51, 1% Darco S-51, 0.55 Nuchar CEE, 15 Darco S-51, 17, Nuchar CEE 17%
LAD-501,
Nuchar CEE, 0.2'7,
Natural pond water, pH buffered a t 7 LAD-505, Natural pond water, 0.05'; p H buffered a t 7 LAD-506, Katural pond water, 0.05"o p H buffered a t 7 LAD-509, Natural pond water, 0.15 pH buffered a t 7 Natural pond water, LAD-510, 0.056 pH buffered a t 7 LAD-511, Natural pond water, 0.19, pH buffered a t 7 LAD-512, Natural pond water, 0.1CC p H buffered a t 7 LAD-513, Natural pond water, 0.16 pH buffered a t 7 LAD-516, Natural pond water, 0.l"C p H buffered a t 7 DEAE-Seph- Katural pond water, adex, 0.1 p H buffered a t 7
Complementao Adsorbent
Kuchar CEE,
LAD-504A, 0.15 LAD-505, 0.04rc LAD-507, 0.2cc
0.85
3.43 2.81
Principal Adsorbent LAD-501, 0.55
LAD-531, 0.02cc
Crude monosodium glutamate, carbon refined
10.0 2.04 4.41 2.72 3.3 3.94
4.5 8.8
l & E C PRODUCT RESEARCH A N D DEVELOPMENT
2.19
2.19
1.32
1.91
2.96 2.88 3.07
3.08 2.06
...
Table VI. Polar Resins as Principal Adsorbent"
4.96
1.58
3.0
Complementay Effect Ambient color Color precursors
6.0 7.0 7.85
O.lW0
1.21
3.0
Table V. Complementary Effects for Clarified and Buffered Raw Cane Sugar Solutions
Buffered p H 1.32
ComplementarS Eflect Ambient Color color precursors
Substrate Acid-enzyme hydrolyzate of corn starch
2.19
Equilibrating conditions 30 minutes and 60" C.
202
Principal Adsorbent
Complementary Effect
LAD-502, 0.17
Darco S-51, 1%
Table IV. Complementary Effects for Ambient Color and Color Precursors
15
Nuchar C-190Ni, 1"'
LAD-507, 0.2Lc
60°C. with 1% Nuchar CEE and 0 . 1 5 LAD-504H based on solids to establish CF (Table V). Complementary effects for ambient color using LAD resins as principal adsorbents were measured (Table V I ) . Carbon equivalent values were found by matching the ambient color removal with a given complementary mixture and a point yielding the same ambient color removal on a standard carbon isotherm for the same substrate. Nuchar CEE was the carbon employed. Influence of Polarity. Figure 3 demonstrates that a linear relationship exists between nitrogen content in a particular phenol-formaldehyde-ammonia resin and complementary effect. Substrate tested was process greens. Complemen-
LAD-504H, 0.4% LAD-504H, 0.2% LAD-500, 0.5%
Complementary Adsorbent
Substrate
Complementa3 Carbon Eflect Eguibalent
LAD-500, 0.15
Refined beet sugar melt, 52.8" Bnx, pH = 7.05 LAD-504H, Refined beet 0.19 sugar melt, 52.8" Brix, pH = 7.05 LAD-505, Refined beet 0.15 sugar melt, 52.8O Bnx, pH = 7.05 LAD-508, Refined beet 0.16 sugar melt, 52.8" Brix, pH = 7.05 Nuchar CEE, Natural 0.1% pond water LAD-505, Natural 0.045 pond water LAD-502, Katural 0.16 pond water LAD-505, Natural 0.170 pond water Britesorb 30, Natural 0.lTG pond water
'Equilibrating conditions 30 minutes and 6OCC.
1.65
8.1
3.66
24.4
1.31
3.21
9.32
8 27
2.1
...
4.4
7.9
2.54
1.69
2.16
1.47
5.38
4.16
P
F
2.2
I . _
0
2
I
3
4
5
6
7
% NUTROGEN IN RESIN Figure 3. Influence clf nitrogen content in a particular type of phenol-formalclehyde-ammonia condensate on complementary effect
tary dosage was 1% Nuchar C E E and 0.1% polar resin based on solids. The systems were equilibrated for 30 minutes a t 60" C. Surface Area of Complementary Adsorbents. N o correlation was found between complementary effect and surface area of complementary polar resinous adsorbents, as measured by the B E T method. This is illustrated in Table VII, which lists results secured by equilibrating 1%Xuchar C E E and 0.1% of various LAD resins with a natural pond water for 30 minutes at 60" C. Seemingly, strength and concentration of polar groups in the complementary adsorbent, as well as the rate of diffusion into the resinous phase, could override the effect of discrete porosity as measured by the B E T method. Simultaneous us. Sequential Addition of Adsorbents. Five methods of equilibrating were pursued: Adsorbent mixture added to substrate, equilibrated, and removed. Carbon added and equilibrated, then resin added and equilibrated, followed by removal of both. Resin added and equilibrated, then carbon added and equilibrated, followed by removal of both. Carbon added, equilibrated, and removed, followed by the same procedure with resin. Resin added, equilibrated, and removed, followed by the same procedure with carbon.
used in the chloride form, so only minor fluctuations in p H occurred during the various steps (Table VIII). I n this tripartite system simultaneous or sequential addition of principal and complementary adsorbents accomplished comparable results if both were allowed to equilibrate together before removal. However, if either class of adsorbent was eliminated before the other was introduced, complementary refining was drastically reduced. Further, the complementary resinous adsorbents appeared to protect the principal carbon adsorbent to a greater extent than in the reverse situation-compare the results from the fourth and fifth methods. Compositional Curve. The effect of varying the weight ratio of resinous adsorbent to complementary mixture (complementary ratio) was measured. C p values were found for different weight ratios of LAD-504H to LAD504H plus Luchar C E E on an acid-enzyme hydrolyzate of corn starch. Per cent of LAD-504H plus carbon, referred to substrate solids, was kept fixed a t 0.2. The substrateNuchar C E E isotherm was also prepared. Thus the Nuchar CEE equivalent for any measured complementary ratio could be established. Equilibration conditions for the system were 30 minutes and 60" C. Results plotted in Figure 4 show that the complementary ratio approached a plateau of efficacy a t about 0.05. Increasing the per cent of resin beyond this point gave only small improvements up to a complementary ratio of 0.4. But from that point on, efficacy increased rapidly up to a peak a t a complementary ratio of 0.7. Complementary Refining Plus Column Deionization. An unrefined acid-hydrolyzed corn sirup containing 42.6% solids and p H of 4.75 was treated for 30 minutes a t 76.5. C. with 0.8';; Darco S-51 alone and with a complementary mixture composed of 0.8'; Darco S-51and 0.085 LAD-527, and the filtrate then percolated a t 4 bed volumes per hour through the sequence of Duolite C-%D ( H ) and A-6. C p p values were measured after heating the Cpfiltrates for 15 hours a t 60°C. (Table IX). Benefits of complementary refining per se and as a pretreatment before columnar ion-exchange refining are evident. General and Economic Observations
The substrate was an acid-enzyme hydrolyzate of corn starch of pH 4.05. The equilibration period was 30 minutes a t 60°C. The principal adsorbent consisted of 0 . 8 5 Nuchar C E E based on solids in each case. The LAD resins were
Although possessing great promise in many applications, complementary refining is no panacea. Most spectacular results often occur when the principal natural adsorbent is doing a relatively poor job. I n one starch hydrolyzate, the ratio of hydroxy t o amide groups in nonsugar solids appeared t o be related directly to the efficacy of complementary refining-for example, a 9 t o 1 ratio of hydroxy to amide groups was tractable; a 1 to 1 ratio, very refractory Resinous adsorbents are expensive relative t o natural ones. However, a complementary mixture of 1'; carbon
Table VII. Influence of Surface Area of Adsorbent on Complementary Effect
Table VIII. Complementary Effects for Simultaneous and Sequential Addition of Adsorbents
LAD 500 501 502 503 Nuchar CEE
Surface Area, Sq.M G
Complementarq Eflect
20.5 1.5 1.0 123.3 740.0
3.38 4.96 2.56 1.35
...
Method
Complementan Effect, Ambient C'olor 5.5 5.63 5.63 2.86 3.61
Complementay adsorbents. LALL504H, 0.08' . LAD-,505, 0.04' .
VOL. 8 NO. 2 JUNE 1 9 6 9
203
Table IX. Complementary Refining Combined with Deionization
Substrate Treatment Blank Carbon alone Carbon + ion exchange Complementary mixture Complementary mixture
+ ion exchange
CF
CPi
0.308 0.029 0.009 0.018 0.005
0.319 0.044 0.010 0.024 0.006
economic benefits and a mitigation of waste-disposal problems. Acknowledgment
I 0
I
02
I 0.4
I
I
I
06
08
10
LAD-504 H ( L A D - 5 0 4 H +NUCHAR C E E ) Figure
4. Compositional
curve
Complementary rotios of LAD-504H to (LAD-504H
+ Nuchar CEE)
per cent Nuchor CEE used alone needed to produce some
VI.
The late Harold E. Barrett, Jr., was in direct charge of the program from which results are reported here and is listed as a posthumous author, although deceased before the final writing of the present paper. Barrett worked under the egis of the senior author, but deserves full credit for development of the techniques employed and the data evolved, as well as the many original ideas he contributed to the program. I. M. Abrams, George F. Stoneman, and Leo L. Benezra have provided many useful suggestions.
C F volue.
Complementary mixture kept constant at 0.2% of substrate solids
and 0.1% LAD resin producing a complementary effect of 3-a refining equivalent to 3% carbon alone-would permit a cost up to $2.80 per pound for the LAD resin with no penalty in direct cost of adsorbents, since good standard carbons sell a t about $0.14 per pound. The added cost advantages would be less filter cake for disposal per volume of substrate treated, more substrate treated in existing filtration stations, and less sweet water from filter cake.
Literature Cited
Abrams, I. M., Dickinson, B. N., Ind. Eng. Chem. 41, 2521 (1949). Graff, R. A . , Pittman, E. E. (to Girdler Corp.), U. S. Patent 2,261,920 (Nov. 4, 1941). Jayes, D. A,, Abrams, I. M., International Water Conference, Engineers Society of Western Pennsylvania, 1966. Stamberg, Jiri, L k t y Cuhrouar. 79, 6 (1963). van Dyk, J. C. (to Product Developers), U.S. Patent 2,600,085 (June 10, 1952).
Conclusions
Complementary refining of liquids using micronized mixtures of resinous and natural adsorbents offers both
204
l & E C PRODUCT RESEARCH A N D DEVELOPMENT
RECEIVED for review Xovember 25, 1968 ACCEPTED March 10, 1969
