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Studies on the organophilic montmorillonites

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Studies on the organophilic montmorillonites

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Content STUDIES ON THE ORGANOPHILIG MONT MORHiLONZCES y>j .Pulak Nath Sanyal A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (Chemistry) January 19f>6 UMI Number: EP41609 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI EP41609 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 U N IV E R S IT Y O F S O U T H E R N C A L IF O R N IA G R A D U A T E S C H O O L U N IV E R S IT Y P A R K L O S A N G E L E S 7 c ‘ S t , sxze This thesis, written by < .Pt^ak..Nath.Sa®j:al....... under the guidance of hi.B—-Faculty Committee, and approved by all its members, has been pre sented to and accepted by the Faculty of the Graduate School, in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE 1 ?. e D ate... Jamiary.. Faculty C om m ittee. ACKNOWLEDGMENT The author wishes to express his sincere thanks to Dr. R. D. Void, for his guidance during the course of this investigation. A special note of gratitude is due Dr. M. J. Void for her generous assistance in the X-ray diffraction phase of this investigation. The acknowledgment would not be complete without expressing sincere thanks to Mr. J. C. Kovarik, Engineer, Great Lakes Carbon Corporation, Dicalite Division, Walteria, California, who drew all the figures presented in this thesis. TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION......... ............................. 1 II. PLAN AND OBJECTIVE OF RESEARCH . .......... 6 III. PREPARATION OF DODECYL AMMONIUM BENTONITE.......... 10 Materials.................................... 10 Determination of Base Exchange Capacity of Volclay Bentonite 200 . .............. ...... 12 Preparation of Dodecyl Ammonium Volclay Bentonite Batch I and II ......................... 13 IV. X-RAY DIFFRACTION STUDIES WITH DODECYL AMMONIUM BENTONITE ................................... 17 X-Ray Technique............. ................... 17 Slide Preparation for X-Ray Diffraction Experiments..................................... 17 Instrument Settings....................... 19 Location of Peaks ....................... 20 Intensity and Half Width of Diffraction Peaks ... 21 Materials Used for X-Ray Diffraction Studies ... 22 Details of Individual Sample Preparation ..... 23 Results of X-Ray Diffraction Studies ............ 28 Discussion of X-Ray Diffraction D a t a ............ Ii7 CHAPTER V. SEDIMENTATION VOLUME EXPERIMENTS ......... Significance of Volume Occupied by Powdered Solid in Liquids ........... ........ Materials................................. Methods . . . . . . . . . . . . . . . . . . . . Results ........ ........ Discussion of the Sedimentation Volume Data . . VI. SUMMARY REFERENCES ............................. ............. LIST OF TABLES TABLE PAGE I. Spatial Relationship for Homologous Alkyl Ammonium Bentonites ................... 3 II. Base Exchange Capacity of Volclay Bentonite 200 . . 11* III. Diffraction Patterns of Volclay Bentonite 200 Air and Ovendried and of Dodecyl Ammonium Bentonite Ovendried....................................... 29 IV. X-ray Diffraction Pattern of Dodecyl Ammonium Bentonite after Exposure to Nitrobenzene, Gyclohexanone, and Benzylalcohol ........... 30 V. X-ray Diffraction Patterns of Dodecyl Ammonium Bentonite - Solvent Systems. Fresh slides from Freshly Prepared Bulk Sample. Unidirectional Stroking............. 31 VI. X-ray Diffraction Patterns of Air Aged Fresh Slides of 10 and 20% Dodecyl Ammonium Bentonite - Nitrobenzene Systems. Unidirectional Slides .... 32 VII. Effect of Solvent Evaporation on X-ray Diffraction Patterns of a 10$ Dodecyl Ammonium Bentonite - Nitrobenzene System. Sample Aged in Air at Room Temperature ....... . ...... 33 vii TABLE PAGE VIII. Series I - Volumes of Dodecyl Ammonium Bentonite in Various Organic Solvents. The Solvents were Taken in 100 ML Graduates and the Solid Dropped in Them ............... ........ . 63 IX. Volumes Occupied by Dodecyl Ammonium Bentonite in Various Organic Solvents, Followed with Time After Shaking ............ ........... 65 X. Volumes Occupied by Dodecyl Ammonium Bentonite in Various Organic Solvents, Series II .... . 67 XI. Specific Volumes of Dodecyl Ammonium Bentonite in Various Organic Solvents, Observed Volumes Computed for One Gram of Dodecyl Ammonium Bentonite ...... .......... ........ 68 f LIST OF FIGURES FIGURE PAGE 1. The Intensity and Half Width Computation of a Typical X-Ray Diffraction Peak ............ 34 2. X-Ray Diffraction Patterns of Volclay Bentonite 200 and Dodecyl Ammonium Bentonite .................... 3$ 3. X-Ray Diffraction Patterns of Dodecyl Ammonium Bentonite When Exposed to Nitrobenzene. Diffraction Pattern Followed with Time of Exposure........ 36 4. X-Ray Diffraction Patterns of Dodecyl Ammonium Bentonite When Exposed to Cyclohexanone. Diffraction Pattern Followed with Time of Exposure ........ 37 5. X-Ray Diffraction Patterns of Dodecyl Ammonium Bentonite When Exposed to Benzylalcohol. Diffraction Pattern Followed with Time of Exposure ........ 38 6. X-Ray Diffraction Patterns of 10$ Dodecyl Ammonium Bentonite - Nitrobenzene System............... . 39 7. X-Ray Diffraction Patterns of 10$ Dodecyl Ammonium Bentonite - Nitrobenzene System. Bulk Sample Aged in Closed Vial ....................................... 40 8. X-Ray Diffraction Patterns of 10$ Dodecyl Ammonium Bentonite - Nitrobenzene System. A Slide was Prepared From Bulk Sample and Then Aged in a Nitrobenzene Atmosphere................................... 41 FIGURE PAGE 9 , X-ray Diffraction Patterns of 10$ Dodecyl Ammonium Bentonite Nitrobenzene System. Fresh Slides From Bulk Sample With Surfaces Tilted at Various Angles ( 4>) to Impinging X-rays bZ 10. Effect of Solvent Evaporation on the X-ray Diffraction Pattern of 10$ Dodecyl Ammonium Bentonite Nitrobenzene System at Room Temperature......... 1x3 11. X-ray Diffraction Pattern of 10$ Dodecyl Ammonium Bentonite 90$ Gum Tragacanth Mixture.............. i t l * 12. X-ray Diffraction Patterns of 20$ Dodecyl Ammonium Bentonite Nitrobenzene System......... 1x3 13. X-ray Diffraction Patterns of 33$ Dodecyl Ammonium 1 Bentonite Solvent Systems . . . . . . . . . . . . . I 46 CHAPTER I I INTRODUCTION i 1 l | Ain alkyl ammonium bentonite is defined as being the reaction I j ! ! product of an organic amine salt and bentonite* Bentonite belongs to S i i I . * the montiaorillonite - beidellite - nontronite series of clays. These j clays are hydrous aluminum silicate minerals. The basie building ! | units are silicon tetrahedron, the aluminum octahedron, and the ! j magnesium octahedron (8). i ! 1 ! Bentonite, as a result of isomorphous substitution in the | i ! | lattice (aluminum for silicon, etc.) carries a net negative charge I [ | in lattice and to counterbalance is associated with cations like j I , 5 _ ’ j sodium or potassium. These counter ions can be exchanged with other 1 - S i . : ! cations. This exchange reaction^ commonly known as base exchange or S i ' ■ ' " I : ion exchange,, was first reported by Way and systematically investigated! ' ■ 1 i by Thomson ( 8). ■ Smith (16) reported that organic amine salts could be base i I « exchanged with bentonite. The reaction was metathetical in nature ! and resulted in the flocculation of the initially hydrophilic clay. • ' ! i i ■ It was subsequently observed that alkyl ammonium bentonite, where < ; | the alkyl chain contained 1G or more carbon atoms, assumed a ( I hydrophobic nature. In solvents like nitrobenzene or methylalcohol - i ; | toluene mixtures, these complexes gave rise to gels of considerable mechanical strength. ( 10) | Bentonite is crystalline in nature. The clay examined under electron microscope is found to he composed of long plate-like | particles which has been substantiated by flow birefringence methods j | (ID. j I From X-ray diffraction patterns of alkyl ammonium bentonites, it j has been concluded that the organic molecules are attracted more or | less in their entirety onto the surface of mineral plates ( 9, 13). | The nitrogen atom of the alkyl ammonium salt is held at the base 1 ; exchange site by an ionic bond and the aliphatic radicals are i I | apparently held as flat as possible against the surface of the clay |by van der Waals forces (10). The extent to which the surface of clay ■ platelets are covered by the alkyl chains obviously depends on the I size and nature of the chains, i.e. whether they are straight chain I or branched. As a result, the clay particles more or less acquire an oleophilic nature depending on the type of alkyl coating on their I surface. Jordan (10) has calculated for a bentonite having a base i ■ exchange capacity of 100 milliequivalents per 100 milligramsof clay, !the surface area of the clay platelets coated by various homologous ’alkyl amine salts on base exchange. The values are given in Table I. The alkyl ammonium bentonites made by using a straight chain j ■ alkyl ammonium salt possesses two types of surface; namely, the part 'which is covered by the organic amine chain and therefore potentially ^oleophilic, and the part which is uncovered and thus still hydrophilic. Table I. Spatial Relationship for Homologous Alkyl Ammonium Bentonites (from Jordan (10) Carbon atoms in amine chain 001 o spacing, A Separation of o clay flakes, A Bayers of amine Calculated amine area A02 Calculated area of clay coated by amine, % 0 9.60 0 *T" — 3 13.3 3 .9 1 38 23 8 13.3 3.7 1 69 lt2 10 13.6 lt.0 1 81 I t 9 12 17.it 7.8 2 9lt 57 lit 17.lt 7.8 2 106 6k 18 17.6 8,0 2 131 79 For such incompletely clad alkyl ammonium bentonites, the oleophilic property is not pronounced until the alkyl ammonium chain contains j 10 or more carbon atoms and dodecyl ammonium bentonite occupies a ! critical position in this series (10). Even when using the dodecyl j I ammonium bentonite, the organic liquid must have a certain degree of j polar character for the amine bentonite complex to show a relatively significant oleophilic character. Such a representative single | solvent can be nitrobenzene. The necessary polar material can be j I provided by addition of a minor amount (e.g. 10$) of a strongly polar j liquid} say, methylaleohol to a nonpolar hydrocarbon like toluene. j ! Alkyl ammonium bentonites, whose alkyl part consists of long J aliphatic radicals in side chains, seem to possess pronounced 1 oleophilic nature even with liquids having little or no polarity ( 10). \ It is significant that these alkyl ammonium bentonites have greater proportion of their surface covered by the organic radical as compared i to the amine-bentonite complexes with straight chain amine salts. Bentones, or the oleophilic alkyl ammonium bentonites, are commercially available as products of National Lead Company. "Bentone ! 18" is produced on base exchanging with octadeeyl ammonium salt. It is a good gelling agent for polar and mixed polar and nonpolar liquid systems. "Bentone 3U" is made from a detergent containing two long chain aliphatic radicals per molecule} the impure commercial detergent, which is used approximates a dimethyl dicetyl ammonium salt in composition ( 18). 5 Bentones are finding uses where a great affinity for an organic dispersion medium is desired. Paints> varnishes, greases, etc. can be incorporated writh these oleophilic bentones. Their use for oil drilling purposes is being investigated. \ ! CHAPTER II I i ! PLAN AND OBJECTIVE OF RESEARCH j I i j It was the purpose of this investigation to study and to j s j elucidate, as far as possible, the mechanism by which the alkyl 1 1 j ammonium bentonites are able to produce gels with organic liquids. ! i ' ■ i t ■ - . • : i Questions of particular interest were the following: j j 1. What controls the extent of solvation of an alkyl ammonium } | bentonite in an organic solvent? What would be a probable explanation j • 1 • ‘ i i. ' • - • • • i | for the diverse behavior exhibited by an alkyl ammonium bentonite in ! - * \ various organic solvents? j 2. How is solvation related to the extent of gelation? Are the 1 particles in a bentone gel held in position by virtue of long range j t I i ! | forces extending from particle to particle through the solvating j | liquid layer, or must there be an extensive particle to particle j 1 i i contact to form the network structure for the gel? > j The second question pertains to a mechanistic analysis of gel ; i ' i | foimation which is still an unsettled question. Some 2$ years back, ; ! » | D. Jordan Lloyd observed HThe colloidal condition, the gel, is one j j which is easier to recognize than to define1 * (12). This aptly ! . - i j !describes the situation even now. i It was not expected that final conclusions should be reached on ! | i I these questions*; however, it was intended that all data and other ; • i !observations should be carefully examined with regard to any pertinent j I contribution that might be made. It was decided that the primary j | ! | feature of the present work would be exploratory in nature, which was, j ! j j in effect, the securing of data which would give an indication of the j ■ i j j | extent and intensity of solvation of a bentone in representative j i i organic liquids. j j The alkyl ammonium bentonite that was used in our investigation I was prepared in our laboratory. We decided to use dodecyl ammonium | bentonite for our experiments because it has been shown to possess a j j critical oleophilic property (10). The details of its preparation J ! - j ! are given in Chapter III. ! i *' i : . i | We selected nitrobenzene, cyclohexanone, and benzylalcohol as j ! [ j representative solvents for dodecyl ammonium bentonite. Nitrobenzene ! * i ! has been claimed to be extremely conducive to gel formation. i ' i Benzylalcohol and cyclohexanone are inferior in this respect. | Bentonite is crystalline in nature and electron microscopic \ _ I ! investigations have revealed that it is composed of long plate-like ! particles (11). The ’001' or the 'Cr spacing which measures the : intersheet separation of the clay flakes can be easily measured. The ' ’C' spacing is quite sensitive to the treatments to which the clay is ; subjected and experiments based on this property have given some valuable information. Hendricks (9) equilibrated the Wyoming bentonite | with water vapor at various relative humidities and found considerable ; I : expansion of the clay lattice along the ‘C* axis. This was explained | as due to the solvation of Na ions with the water molecules coming ! 8 ! into these interlattice spaces and prying open the individual clay i • . . ' flakes. McEwan (13) studied the adsorption of various organic liquids I | on montraorillonite and was able to follow the expansion along the I ' *C* lattice from X-ray powder diagrams. The organic molecules were i , I found to enter between the structural sheets of clay mineral arid | arranged themselves as flat as possible on the clay surface. ' Jordan (10) measured the 'C* spacing of various homologous straight | \ ■ chain alkyl ammonium bentonites and found a stepwise increase in the ; *C* spacing with increasing length of carbon chain of the amine. The ( i separation by steps of UA° which is equivalent to the van der Waal's i diameter of the methyl group indicated that the amine chains were | being adsorbed flat on the interlattice surfaces of the clay flakes. i ; When more than half the clay surface was covered by the amine molecule, , the individual clay particle could approach each other no closer than ! 8A0 and such is the case with dodecyl ammonium bentonite. The critical position of dodecyl ammonium bentonite was explained as due to the greater initial separation of individual clay flakes; thus inducing .easier solvation. (See Table I) It is evident that for solvation of an alkyl ammonium bentonite, \ ;the solvating molecules will have to gain access into the interlattice spaces. In doing so, they will affect the 'G' spacing of the alkyl : ammonium bentonite. So, it was decided to investigate the effect on the 'C1 spacing of the dodecyl ammonium bentonite by exposing them to the various organic solvents for evaluating the intensity of | 9 i solvation. 1 | It was also decided to find out whether or not in the dodecyl j | ammonium bentonite - solvent systems* the dodecyl amine retained its ! crystalline nature. X-ray diffraction studies of such suspensions J j (or gels) were considered to be capable of giving us some information i las to the nature of dispersion of the dodecyl ammonium bentonite particles in such systems. We also investigated the sedimentation volumes of the dodecyl j ammonium bentonite in various organic solvents. We were primarily i i I interested to find out whether such volumes were equilibrium values, i ! |and also, were they really the ''swelling volumes" as Jordan has (Claimed them to be, or merely sedimentation volumes. CHAPTER III PREPARATION OF DODECYL AMMONIUM BENTONITE Materials The bentonite which was used in this investigation was a volclay sample from the American Colloid Company. The specifications of this "volclay bentcnite 200“ are reported in the physical characteristics of volclay bentonite, data sheet 202 of the American Colloid Company (16). It is reported to be a sodium montmorillonite sample with the following particle size distributions when dispersed in water: 96.$% finer than i i i * microns 93. 5$ finer than 5 microns 88. 0$ finer than 0.$ microns 62.f>$ finer than 0 .1 microns The reported base exchange capacity is as follows: Na+ = 85.5 milliequivalents/lOO grams K+ = 5.0 railliequivalents/100 grams Ca+^ = 2 2 .0 railliequivalents/1 0 0 grams Mg+2 e . i.o milliequivalents/lOO grams Sum corrected for sulphates 89.2 railliequivalents/100 grams The dodecyl amine used for base exchanging with the volclay bentonite was obtained from the Amour and Company. It was labeled as pure and specified to contain a minimum 97. 0$ of the primary amine. We prepared two batches of the dodecyl ammonium bentonite. Batch I 11 was prepared with the "as received" sample of dodecyl amine. Batch I !dodecyl amine bentonite was used for sedimentation volume studies. I The dodecyl amine, as received from the Armour and Company, was I I | distilled at a 23 millimeters of mercury vacuum in a distillation t !flask without a column. The first fraction coming out had a strong j i smell of ammonia, and was rejected. The fraction that came out in the | temperature range of 135 to li* 5°C, was collected and used for the | preparation of Batch II dodecyl ammonium bentonite. The distilled t !amine had a white crystalline appearance. i | In order that an equivalent amount of dodecyl amine salt be i ■ added to the volclay sample, in the preparation of the dodecyl I |ammonium bentonite, it was necessary that the base exchange capacity of the volclay bentonite be determined. Since the volclay bentonite dispersion in water contained some nonclay sediment, the nonclay i percentage of the sample also had to be determined. For determination of nonclay sediment, the following procedure was adopted: A five gram sample of the clay sample was dispersed ■ thoroughly in about a liter of distilled water. It was allowed to I settle for 12 hours. The supernatant liquid containing the finer bentonite particles was withdrawn very carefully, and the sediment was redispersed in 200 ml of distilled water in a 1*00 ml beaker. It I was allowed to settle for an hour and the supernatant liquid was again withdrawn carefully. This step was repeated two more times and | then the sediment was transferred to a weighed 50 ml beaker ■quantitatively. The sediment was dried to a constant weight at ^110°C in an oven. The determination of nonclay sediment was done in ! i |duplicate and the precision was high. The average nonclay sediment j | | |for volclay bentonite 200 was found to be 6.76$. The average moisture j |. ] -content of the volclay was found to be 8.80$. I j :Determination of Base Exchange Capacity of Volclay Bentonite 200 j | | ; There are two principal methodsfor the determination of the base I | j r | :exchange capacity of clays ( 6,16): ! ! | I 1. Electrodialysis method - The clay is converted to a hydrogen ! Iclay by prolonged electrodialysis. The hydrogen clay is then j ! j Ipotentiometrically titrated against standard alkali and the number j i i !of equivalents of hydrogen ion per 100 gms. of clay equal the base ! ;exchange capacity. 2. Ammonium acetate leaching method - The clay is leached with ammonium acetate thoroughly and converted to ammonium clay. The ; I • excess ammonium acetate is washed with alcohol. The ammonium acetate ! 1 combined with the clay is determined by Kjeldahl’s distillation method.< The equivalents of ammonia per 100 gms. of clay equal the base i j exchange capacity. We used the ammonium acetate method of Graham and Sullivan ( 6) ! ;as modified by Stratton (18) in this laboratory for base exchange ( i * 'capacity determination. I A very detailed and thorough description of the apparatus and i jprocedure for this modified method of determination of base exchange i capacity is given in Dr. Stratton's Ph.D. thesis. We followed his ! • . I i directions completely and hence, we shall refrain from giving the ! ! details of this method. The average base exchange capacity determined j j on several samples was found to be 87.82 milliequivalents per 100 gms. i \ i i j | of "as received" clay. When corrected for moisture and nonclay j i sediment percentage, the average base exchange capacity was 102 ! i ‘ | milliequivalents per 100 gms. of pure dry clay. The data are given \ } i \ in Table II. \ i j i I ! ! Preparation of Dodecyl Ammonium Volclay Bentonite I ■ i It was decided that the dodecyl ammonium bentonite would be i j prepared such that the base exchange capacity of the volclay bentonite | ; i \ ! I was just satisfied. It has been reported in literature that the j greatest oleophilic property for the dodecyl ammonium bentonite is obtained in the region of complete saturation of the base exchange capacity with neither excess nor insufficient amine present. The Batch I dodecyl ammonium bentonite was prepared before the base exchange capacity of the volclay bentonite was determined. It > ; was subsequently found that in the Batch I dodecyl ammonium bentonite, j / j ! 112 milliequivalents of amine hydrochloride was reacted with 100 gms. of pure dry clay. Batch II was prepared such that the base exchange capacity of the clay was just satisfied. The following procedure was \ ; followed in the preparation of the dodecyl ammonium bentonites. i Preparation of Batch I Dodecyl Ammonium Bentonite i lU TABLE II BASE EXCHANGE CAPACITY OF VOLCLAY BENTONITE 200 Average Moisture Content % 8.80 ; Average Nonclay Sediment % 6.76 | ; Average Base Exchange Capacity j on Mas received” clay Basis ! Milliequivalents/lOO gms. 87.82 * Average Base Exchange Capacity : on Pure Dry Clay Basis I Milliequivalents/lOO gms. 102 | ! I I i ! 1 5 I | 20 grains of volclay bentonite "as received" was dispersed in 1 ’ i | j 5 liters of deionised water with an air stirrer. The dispersion was , ' ■ I |agitated for an hour and then allowed to settle for 12 hours. The ! i • \supernatant liquid containing the finely dispersed particles was !carefully decanted and 20 milliequivalents of dodecyl ammonium i • !hydrochloride, (nonpurified) were added to it slowly with vigorous j i j ’stirring. After addition of the amine hydrochloride, the flocculated j I I 'mass was stirred for another half an hour. Then the flocculated mass | I . ! jwas filtered and dispersed in a liter of distilled water and j :refiltered. This step was repeated three more times. Finally, the imass was spread on an evaporating dish and kept in an oven at 65°C. Drying was very slow and took about 3 days. After drying, the material was ground up in a porcelain mortar until it appeared finely ground. |Correcting for the nonclay sediments and moisture content of the ; volclay and assuming 97% purity of dodecyl amine, 19.lt milliequivalents j of dodecyl ammonium hydrochloride were added to 17.3 gms. of pure dry •clay. Hence, the amine clay ratio was 112 m.eqvs. per 100 gms. of ;pure clay. Preparation of Batch II Dodecyl Ammonium Bentonite The procedure was exactly the same as in preparation of Batch I ‘except the following: A 20 gm. sample of volclay was reacted with 17.6 milliequivalents of dodecyl ammonium hydrochloride. The dodecyl amine was distilled as previously mentioned. Assuming 100 percent purity for the amine, Batch II had an amine clay ratio of 102 m.eqvs. 16 | per 100 gms. of pure dry elay. Hence, in this case, the base j | exchange capacity of the clay was exactly satisfied. The mass was j | dried in a vacuum oven at 6$ + £°C for 12 hours, and ground up. Both i i Batch I and Batch II - dodecyl ammonium bentonites were kept in a j ( desiccator while they were not used. j I i i i i CHAPTER IV X-RAY DIFFRACTION STUDIES WITH DODECYL AMMONIUM BENTONITE X-ray Technique The X-ray diffraction patterns were taken with the standard \ Norelco geiger counter X-ray spectrometer, No. 12021. Full description! I | of this instrument can be found in literature (7). We shall discuss, j i f \however, certain aspects of the X-ray spectrometer unit and its i ? ' • j , jaccessories that are pertinent in understanding the technique that we j i : i i |used in our study, j | Slide Preparation for X-ray Diffraction Experiments i As pointed out in Chapter II, we decided to investigate this | 'problem from two general directions: s ; a) To expose the dodecyl ammonium bentonite to vapors of organic \ I solvents, and follow the effect on the *C• spacing of the former with 1 ;exposure times. t b) To prepare dodecyl ammonium bentonite - organic solvent jsystems, and take diffraction patterns of these systems. Based on these two general ideas, the experiments we performed can be classified as follows: j 1. Diffraction pattern of volclay bentonite 2G0. 2. Diffraction pattern of dodecyl ammonium bentonite. . 3* Diffraction pattern of dodecyl ammonium bentonite - gum ! 18 ! i tragacanth mixture in the ratio 10:90. I . ! k* Diffraction patterns of dodecyl ammonium bentonite after i ! exposure to nitrobenzene, cyclohexanone, and benzylalcohol. i j 5. Diffraction patterns of dodecyl ammonium bentonite - organic I 1 solvent systems. I j Clay particles are susceptible to orientation because of their j I thin plate-like particles (11). Strong X-ray diffraction pattern I should be expected from the ' C1 spacing of the clay particles when j ! they are lined up parallel to the surface. So, in preparing slides | of these clay systems, one should try to prepare the slides such that i the sample in the slide has a smooth surface ( 16). { S ■ j We used glass slides for our experiments. The slide consisted ; of a rectangular glass strip with a circular hole bored in it. ; Another full glass slide could be attached to it with scotch tape such 1 that a base for the circular hole was formed in which the experimental J sample could be placed. The dimensions of the glass slides were - diameter of circular hole = 1.50 cans, depth of circular hole ■ 1.20 mms. | For preparation of slides of powdered materials, such as the volclay bentonite, etc., the powder was taken into the slide hole and i the surface smoothed by pressing with another glass slide firmly, • such that a smooth and compact surface in level with the surface of i the sample slide could be exposed to the X-ray beam. For preparation of sample slide of dodecyl ammonium bentonite - j solvent systems, the moist mass was taken into the slide hole and the t i j surface smoothed by 60 unidirectional strokes with a nickel spatula. ! A few slides were prepared with multidirectional stroking to find i ) whether the direction of stroking affected the orientation of clay i j particles. It was found that the diffraction pattern was independent I of the direction of stroking (Figure 6). i I k I Instrument Settings ! 1. Slit System ' The width of primary beam is regulated by the choice of one | of the three vertical slits (course, medium, and fine). The height j is controlled by a horizontal metal slide with a tapered slit from 1 i to 7 mm. opening. A similar slit system on the geiger counter just j : in front of the nickel filter selects a fraction from the center of the diffracted beam, j 2. Recorder System The strip chart recorder is a Brown Instrument Company :potentiometer, Model No. 153X12V-X-30, with a $0 millivolt full scale :reading. Chart speed used is 1 inch per minute which corresponds to :1° of 2 © scanned by the 1 RPM goniometer motor. 3» Counting System The output of the geiger tube is fed to a counting rate meter, ■ Model 1610B supplied by the Nuclear Chemical Company. A 100 fold variation in sensitivity (voltage indication per unit output from the •geiger tube) is available. The lowest setting (50,000) was used 20 throughout. Three settings of “fluctuating'1 control are available, 2/S, B%) and V~>%. This means all voltage signals different than 2% from mean, are eliminated and screened out from the voltage fed by the rate meter to the recorder. For all our X-ray diffraction experiments, we used the following instrumental setting: X-ray slit fine geiger slit - medium X-ray slide - 7 geiger slide - 7 Amplitude - 5o,ooq dancing 2% jLocation of Peaks j i j j The angular position of a peak is found from its location in the i ! ; strip chart of the Brown recorder. The scanning speed of the geiger- I : Muller counter was one degree per minute in all experiments (using the ; | ; one RPM motor) and the chart speed, one inch per minute. Thus, one i ‘ ; ; inch on the abscissa of the recorder chart which is divided into i decimal parts of the inch, corresponds to one degree of the diffraction! j angle 2 0. ' Using the Bragg equation, • I _d_ . X n 2S in 0 j f d * the distance between two consecutive (h,k,l) planes i * n = the diffraction order of the diffraction cone X = wave length of the X-ray beam \ I > 9 = the angle of incidence of the X-ray beam 21 i I It is evident that peaks are obtained, when the Bragg equation j } is satisfied. The X-ray tube of Norelco X-ray spectrometer has a ! ° i copper target so, X = 1.5U18A. From the recorder chart, the 2 0 , j the diffraction angle, i.e. (the angle between incident and diffracted j i beams) can be read corresponding to the peak position. Synchronization! between geiger counter goniometer motor and the recorder is essential. I The recorder drive is started with the recording pen on a whole degree mark when the vernier of the scanning arm indicates a whole degree (17). The — values corresponding to the 2 © value measured at the peak maximum can be directly obtained from a chart. In our case, we I measured the 2 0 values corresponding to the first order of the | diffraction cone. ; i i jIntensity and Half Width of Diffraction Peaks (17) Two other features of the diffraction peak are of significance; : i [namely, the intensity and the half width of the peak. The intensity' I ’ ; i • 1 i of a peak is a measure of the electron density of the planes which j are involved in the diffraction of the X-ray beam* It is measured by !the area under the peak obtained on the recorder chart. For peaks of ( i : !similar shape, the areas under the curves are directly proportional to | 1 i 1 their height; therefore, the practice is tbo record the height and i I width at half height. The intensity is measured along the ordinate * I .... : !of the strip chart and can be expressed in scale units, ten units I j corresponding to 28 mms.. The intensity of the line is determined at j ! i , the same angle as the location of the peak, close to the peak maximum, ! < _ _ _ j [ 22 j | and is computed above the irregular background scattering. For this j j j purpose,- a base line is drawn so as to join the lowest points of the j t ! I X-ray curve directly on each side of the peak. I i ; i 5 The intensity values give some indication about the number of j I lattice planes which give rise to the peak. The more parallel lattice ; | j planes there are in a crystal, the stronger will be the corresponding I \ i j reflection. ; ! j [ Theoretically, a peak resulting from an infinite number of j s . j ; equivalent parallel lattice planes, should appear at an infinitely j ^ • ’ : narrow value of the diffraction angle satisfying the Bragg equation. j ; Experimentally it is observed that a diffraction maximum is smeared ! \ i ; | ! out over a certain angular range, centered at the value of 2 9 given j i ' ■ t by Bragg equation, with the intensity falling off rapidly in both ; directions with changing diffraction angle. J The angular breadth of diffraction maximum can thus indicate s certain structural arrangement. This is measured in terms of the ' 1 half width* which is the width of a peak at a point where its ! • • i intensity is one half of the full value. Half width is thus expressed i ! in terms of degrees of the diffraction angle 2 9,. and is conveniently i measured on the spectrometer curve by the width of the peak at half ; height,, the height being computed above the background scattering. j The intensity and half width computation for a typical spectrometer :curve is illustrated graphically in Figure 1. Materials used for X-ray Diffraction Studies s 23 i ■ 1. Volclay bentonite 200. | 2. Dodecyl ammonium bentonite - Batch II, ovendried. The | specifications of volclay bentonite and details of preparation of idodecyl ammonium bentonite, are given in Chapter III. j i 3. Solvents - (a) Nitrobenzene (C.P) Braun Corporation ! i (b) Cyclohexanone (C.P) Mathieson Co., Inc. | (c) Benzylalcohol (C.P) Mathieson Co., Inc. i ! ; Details of Individual Sample Preparation I ■ ■ 1. Diffraction patterns were obtained both for airdried and ! ovendried (11G°C, 3 hrs.) volclay bentonite samples. The volclay jbentonite was in a finely powdered state and hence, used without any (further grinding. 2. The dodecyl ammonium bentonite (Batch' II) was grouhd in a ! mortar until it appeared finely powdered. It was then dried in a vacuum oven at 67 1 5°C for 12 hours. This dried sample was used for ■all the X-ray experiments involving dodecyl ammonium bentonite. 3. For studies involving exposure of dodecyl ammonium bentonite :to vapors of organie solvent, the following technique was used - about 1 1 gm. of dried ground dodecyl ammonium bentonite was taken in a weighed Ishallow petri dish. In another shallow petri dish, the organic solvent Iwas taken. The petri dishes were covered by a bell jar and left to I equilibrate. At certain time intervals (i.e. after 3> 6, and 150 hours of exposure of the dodecyl ammonium bentonite to the solvents), I the petri dish containing the dodecyl ammonium bentonite was weighed i and the amount of solvent picked up was computed. The mass was then thoroughly mixed up with a spatula, to ensure uniformity, and a slide ! was prepared for X-ray diffraction studies. After the X-ray I 1 diffraction pattern was taken at each of these intervals, the sample t } • in the slide was poured back into the petri dish, which was reweighed. > The main mass of dodecyl ammonium bentonite was kept in the solvent I atmosphere most of the time except when it was being weighed,, to i I minimize the tendency of the imbibed solvent to evaporate. j • !*. It is best to discuss preparation of solvent - dodecyl | ammonium bentonite systems that were prepared for X-ray diffraction | study individually. | Dodecyl ammonium nitrobenzene systems of 1G, 20, and 33% i solid contents were prepared in the following manner - The required ) I amounts of the solid and the solvent were put in a screw eapped vials, i The mass was then mixed thoroughly with a nickel spatula at room ; temperature. In the course of the mixing, it could be felt that the ’ resistance to the motion of the spatula was gradually increasing. Big lumps of wetted solid were broken down with the nickel spatula j and after 15 minutes of vigorous mixing* a nice yellow colored mass was obtained, which did not flow when the vial was tipped over its ;mouth even at 10$ solid content. The bulk sample was kept in the I closed vial to prevent any evaporation of nitrobenzene. With cyclohexanone as a solvent, the 10 and 20$ dodecyl ammonium [bentonite produced rather thin and easily flowing systems. Sample 25 I 1 slides with smooth and compact surfaces, could not be prepared from t | these systems. Hence, we had to restrict ourselves to a 33% dodecyl | ammonium bentonite - cyclohexanone system, of which we could prepare i | a satisfactory sample slide. The method of preparation was exactly ! the same as the corresponding nitrobenzene system as outlined above. i The bulk sample in this case, however, lacked the high consistency I i ! of the corresponding nitrobenzene systems. This was qualitatively j inferred from the ease with which the nickel spatula could be worked ; in the mass. j 5. A rather peculiar phenomenon was observed with the fresh I slide prepared from the 10 and 20% dodecyl ammonium bentonite - ' nitrobenzene systems} namely, the fresh slide gave a diffraction i ! pattern with only diffused scattering and no definite peak. However, as this slide was aged for about 2 hours in air at room temperature, : there was a peak in the diffraction pattern, the position of which (2 © = li.21) agreed very closely to the peak position that was obtained when dodecyl ammonium bentonite was exposed to nitrobenzene for about 150 hours (2 © = it.51°). This behavior was independent of j i the manner of stroking the sample surface. Sample slides prepared • with strokes, whether unidirectional or multidirectional, behaved identically. Also, if we mixed up the contents of the aged slide ! after a peak was obtained in the diffraction pattern, and then ; resmoothed the surface, the diffraction pattern from this reformed : slide was again diffused (Figure .60). On the basis of the various experiments we devised to elucidate j this phenomenon, it appeared that the explanation of the behavior was probably as follows: The 10% dodecyl ammonium bentonite - nitrobenzene; system had a random configuration in the bulk sample and hence, the diffused diffraction pattern of the fresh slide. When the fresh j ! slide aged in the air, surface drying of the sample took place due to ] ! I evaporation of the nitrobenzene from the surface. As a result, the ! \ clay platelets arranged themselves in a configuration parallel to the j surface and formed, so to say, “a well ordered skin over the rest of I i the sample with random configuration.M This surface layer gave the i diffraction peak. j 1 i We investigated the possibility that the freshly prepared 10% ! dodecyl ammonium bentonite nitrobenzene system was in a metastable stage which reverted back to a stable configuration of the clay platelets, which resulted in some order in their arrangement and hence,; gave a diffraction peak. We let the bulk sample age in a closed vial (to prevent any solvent evaporation) and prepared fresh slides from it at certain intervals (i.e. after 30 minutesj 1, 2, and 18 hours' aging) and examined their diffraction pattern (Figure 7). All the diffraction patterns were diffused and had no peaks. A slide made from the fresh bulk sample, when aged in nitrobenzene atmosphere instead of in air, developed no peaks in the diffraction pattern on standing as long as Hi hours (Figure 8). The possibility that the clay platelets had some order in their 27 orientation in the fresh slide but that the axis of orientation was at an angle to the surface of the sample slide, was also investigated by mounting the fresh slide on a special mount (19), such that the stir face of the sample can be tilted at various angles (<j> ) to the impinging X-ray beam (Figure 9). This measures diffraction from crystallites inclined the sample surface. The absence of such crystallites were shown in the diffused diffraction pattern obtained so the appearance of diffraction peak in the slide aged in air was not due to any reversion of some existing axis of orientation to a position parallel to the slide surface. So, it appeared that it was the surface drying that resulted in appearance of diffraction peak in this system. To test the effect of solvent evaporation, we took about one gram of the bulk sample and spread it on a weighed glass slide (7.6 x 2.5 cms) in a thin layer. The slide was allowed to age in air at room temperature. At certain intervals (i.e. 9, 12, and 27 hours of aging), the slide was weighed and the concentration of solid phase computed. The mass was then mixed with a spatula to ensure uniformity and diffraction patterns were taken for sample slides at each of these intervals. After 27 hours drying, with a solid phase concentration of 27.5$, there was only an indication of a possible peak between the 2 9's i t and 5°, (Figure 10). As it was subsequently found that even a 33$ dodecyl ammonium bentonite - nitrobenzene system had only a very diffused indication of a peak in the 2 0 range of k to 5°, the surface drying j of the 10% fresh hulk sample slide must achieve a higher concentration I ! I I of solid phase on the surface of the slide• j ' i ! i 1 Results of X-ray Diffraction Studies j j The results are given in Tables III to VII. i i j The original X-ray diffraction patterns were traced on a tracing I i |paper and then photostatically reduced to half the original size. I These reduced prints are given in Figures 2 to 13. j TABLE III DIFFRACTION PATTERNS OF VOLCLAY BENTONITE 200 AIR AND OVENDRIED, AND OF DODECIL AMMONIUM BENTONITE OVENDRIED Sample 2 6 Corresponding To First Order Peak Degrees Interplaner or •C1 Spacing In A Half Width Of Peak In Degrees of 2 0 Intensity of Peak In Chart Units Corresponding Diffraction Patterns Volclay Bentonite 200, Airdried 6.95 12.72 1. 1 + 8 20 Figure 2 Volclay Bentonite 200 Ovendried 7.60 11.63 2.2 18.0 Figure 2 Dodecyl Ammonium Bentonite Ovendried 5.60 15.78 1.52 20.0 Figure 2 ro vo TABLE IV X-RAY DIFFRACTION PATTERN OF DODECYL AMMONIUM BENTONITE AFTER EXPOSURE TO NITROBENZENE, CYCLOHEXANONE, AND BENZYLALCOHOL Solvent Time of Exposure of Sample to Solvent in Hours ia Solvent Absorbed by Sample Position of First Order Peak in 2 9 Degrees •C1 Spgcing in A Units Expansion in *C* Spacing in A Units Half Width in 2 © Degrees Intensity in Chart Units Corresponding Diffraction Pattern Nitro None . . . 5.60 15.78 - - - 1.52 20 Figure 3 benzene 3 o,44 5.1*5 16.21 0.43 1.50 16 6 0.66 5.1*5 16.21 0.43 1.50 13 150 10.2 4.5o 19.64 3.86 1.65 17 Cyclo- None - - - 5.60 15.78 - - - 1.52 16 Figure 4 hexanon J 3 0.5 5.55 15.92 0.14 1.52 14 6 1.0 5.55 15.92 0.14 1.55 15 150 1.2 5.5o 16.07 0.29 1.55 12 Benzyl- None - - - 5.60 15.78 - - - 1.52 20 Figure 5 alcohol 3 o.44 5.55 15.92 0.14 1.52 16 6 0.56 5.48 16.12 0.34 1.40 13 1^0 3.78 5.00 17.67 1.89 1.60 19 TABLE V X-RAY DIFFRACTION PATTERNS OF DODECYL AMMONIUM BENTONITE - SOLVENT SYSTEMS Fresh Slides From Freshly Prepared Bulk Sample, Unidirectional Stroking - Solvent % Dodecyl Ammonium Bentonite Position of Peak in 2 © First Order Degrees •C1 Spacing in A Half Width in 2 © Intensity in Chart Units Corresponding Diffraction Patterns Nitrobenzene 10 Diffused pattern no peaks observed Figure 6 Patterns A & C Nitrobenzene 20 Diffused pattern evidence of peak in the 2 © range i * to $ Figure 12 Pattern A Nitrobenzene 33 Diffused pattern evidence of peak in the 2 © range i i to Figure 13 Pattern A Cyclohexanone 33 £.6o l£.78 1.1 Figure 13 Pattern B TABLE VI X-RAY DIFFRACTION PATTERNS OF AIR-AGED FRESH SLIDES OF 10 AND 20$ DODECYL AMMONIUM BENTONITE - NITROBENZENE SYSTEMS UNIDIRECTIONAL SLIDES Sample Aging of Sample in Slide Position of Peak in 2 9 Degrees ’C1 Spacing in A Units Half Width of Peak in 2 9 Degrees Intensity in Chart Units Corresponding Diffraction Pattern 10$ Dodecyl Ammonium Bentonite Nitrobenzene Fresh Slide 2 : hours Diffused Scattering U.21 20.99 1.2 7.5 Figure 6 20$ Dodecyl Ammonium Bentonite Nitrobenzene System Fresh Slide Evidence of Diffused Peak in 2 9 - Range of Ut©5° ... Figure 12 2 hours il.21 20.99 0.83 10.5 | TABLE VII ! I ! . 1 I I { EFFECT OF SOLVENT EVAPORATION ON X-RAY DIFFRACTION PATTERNS OF A j j j | 10$ DODECYL. AMMONIUM BENTONITE - NITROBENZENE SYSTEM | f • ; j SAMPLE AGED IN AIR AT ROCM TEMPERATURE j I UNIDIRECTIONAL SLIDES Time of Aging in hours % Dodecyl Ammonium Bentonite in the System Diffraction Pattern Corre spending Diffraction Patterns 0 10 Diffused and no evidence of peak Figure 10 9 12.1 Diffused and no evidence of peak Figure 10 12 13.3 Diffused and no evidence of peak Figure 10 27 27.5 Evidence of possible peak in the range of 2 0 U to 5G Figure 10 HALF W ID TH OF PEAK IN DEGREES -© ■ 1 - ------- -— z-e---------- - j THE INTENSITY AND HALF WIDTH COMPUTATION OF A T Y P IC A L y -R A Y - d i f f r a c t i o n p e a k - FIG.- I 35 1 J ? *1 r * 4 > N» * • u> K O OO n a - AIR DRIED VOLCLAY BENTONITE 2 0 0 1 A 1 V 0 \ °* 1 VOI V V I \ <t>\ M| (O u> C T > — <o I b - OVEN DRIED VOLCLAY B ENTO N ITE 2 0 0 r >- H tO z Hf P» - £ 7 - 2 D — ( U) in «p oo C - OVEN DRIED DODECYL AMMONIUM BENTONITE X -R A Y -D IF FR A C TIO N PA TTER N S OF VOLCLAY BENTONITE 2 0 0 AND DODECYL AMMONIUM BENTONITE FIG 2 FIG.- 5 0 2-e 4 5 ze H 2 m 0) n X* RAY-DIFFRACTION patterns of dodecyl ammonium bentonite WHEN EXPOSED TO NITRO BENZENE. DIFFRACTION PATTERN FOLLOWED WITH TIME OF EXPOSURE. o FIG.- INTENSITY X-RAY-DIFFRACTION PATTERNS OF DODECYL AMMONIUM BENTONITE WHEN EXPOSED TO CYCLOHEXANONE . DIFFRACTION PATTERN FOLLOWED W ITH TIME OF EXPOSURE HNT1HS»TY-*| (V 4> 00 \ 4 .5 2 0 =5.6 X-RAY-DIFFRACTION PATTERNS OF DODECYL AMMONIUM BENTONITE WHEN EXPOSED TO BENZYL ALCOHOL. DIFFRACTION PATTERN FOLLOWED WITH TIME OF EXPOSURE . 39 ----------- Q . ONI- DIRECTIONS- FRESH u> rF ~ T o o ' <r > SLt DC iA-i iW ( K \ r- ^ IN - |* 1 » l < t > N M il 11 VHyli 4*vH< b, UNl- DIRECTIONAL , SLIDE AGED Z HOURS IN AIR VijK Pi T^= 'us ' v j > C/ MULTI-DIRECTIONAL., FRESH SLIDE > in z Iu H Z -2-©— I • W ^ i W V r- lo o d i M U LTl'-D IR EC TIO N A L, SLID E AGED 2 HOURS \N AIR -«=— td ) MIKED WITH SPATULA , AND C, SAMPLE IN SLIDE R E SMOOTHED. P \ G ~ 6 in z u U L i z O h- 2 t* IL IX X UJ l — in x to UJ z UJ N Z U J oo o o e : UJ z o h- z U J C O z o z z <r j 5 O m » o 5 ° a. js k 2 MNTENSVTY T < t > X-RAY- DIFFRACTION PATTERNS OF 10*70 DODECYL AMMONIUM BENTONITE, NITRO BENZENE SYSTEM. BULK SAMPLE AOED IN CLOSED VIAL. k l T ~ > f m z Ui P Z h z-e- (O . 3- fin vS (v . Q , S L ID E A G E D I H O U R . 0~> lo (_ 9 r - ~ S L ID E A G E D 3 H O U R S . 00 b m m in T j ? ) f i i j uO { T > C , S H O E A 'G E D \A H O U R S . X -R A Y -D IF F R A C T IO N PATTERNS O F IO % D O D E C Y L AMMONIUM B ENTO N ITE, NITRO B ENZENE S Y S T E M A S L ID E WAS PREPARED F R O M BULK SAMPLE AND TH E N AGED IN A NITRO B E N Z E N E A T M O S P H E R E FIG.- 8 - INTENSITY - T no 0> .1 . T1 «5 P o . I 0 6 C£> X- RAY - DIFFRACTION PATTERNS OP IO°7o DODECYL AMMONIUM BENTONITE NITRO BENZENE SYSTEM. FRESH SLIDES FROM BULK SAMPLE WITH SURFACES TILTED AT VARIOUS ANGLES IpH TO IMPINGING X-RAYS. INTENSITY ov Vo a , FRESH SLIDE FROM lOVo DODECYL AMMONIUM BENTONITE, HITRO BENZENE SYSTEM . To SOLID PHASE 12,1 % .. } U - ! rt in t t > r~ ao < r > F R ES H S L ID E A F T E R 12 HOURS D R Y IN G , S O U D PHASE 1 3 .3 % r d , F R E S H S LID E A FTEfc Z i HOURS D R Y IN G , SO U D PH A SE 2 7 .5 °7© ' EFFV E C T O F SOLVENT EVAPORATION ON THE X-RAY - DIFFRACTION PATTERN O F 10% D O D E C Y L AM M O NIUM BENTONITE - NITRO BENZENE SYSTEM, A T ROOM TEMPERATURE. r * Y- in iu u r- Z 7 1-2* J in X-R A Y-D IFFR A C TIO N PATTERN OF IO % DODECYL AMMONIUM BENTONITE, 9 0 % GUM T R A G A C M T H M IX T U R E . FIG.-I 1 \ m j n n , __________________ " t * o ' l a * 5 5 *00 ^ n « u T v» t » C L , F R E S H S L ID E . ® Ro R5 b . s l id e - A g e d 2 h o u r s . • s X - R A Y - D IF F R A C T IO N P A T T E N S OF 20*7© DODECYL A M M O N IU M & E N T 0 W T E , N IT R O B E N Z E N E S Y S T E M . FIG - 12 INTENSITY ! T i_ l_ __ b xn m 03 F R E S H S L ID E O F 3 3 % DO DECYL AMMONIUM B E N T O N IT E , N IT R O B E N Z E N E S Y S T E M . “ t — \ \ A 1 \ / q j \ \ y1 r 5 5 * \ ? ! \ i \ J 4>| \ NI 1 V 1 V - -- *- in V P h © t , F R E S H S LID E O F 3 3 °7 o OODECYL AMMONIUM B ENTO NITE, CYCLO HEYANONE S Y S T E M . X -R A Y -D IFFR A C TIO N PATTERNS OF 33°7o DODECYL. AMMONIUM BENTONITE, S O LV E N T S Y S T E M S . FIG. 13_______ ( Discussion of X-ray Diffraction Data | The following points are brought out from the data given in the |Tables: (III-VII) i 1. The interplaner spacing of volelay bentonite ovendried at i o :110°C for 3 hours was found to be 11.63A (Table III). This does not ! © |agree with the value of 9.6a reported by other workers (10,13). It 1 jseems rather improbable that the ovendried sample would contain any i lextraneous moisture in its interlattice spaces, which can account for | o this difference of 2.03A in the 'C' spacing. Some possibilities iremain, however, e.g. the sample of volelay bentonite 200 may differ i istructurally from other bentonites, or even when it was ovendried, i jsome water molecules were left in the interlattice spaces. i 0 | 2. The airdried volelay bentonite gave a 1C* spacing of 12.72A ;(Table III). The moisture content of the airdried sample was 8.8%. ■The increase in the ' C' spacing over the ovendried sample is thus, | o ;1.09A. Since the van der Waal's thickness of a layer of water is o ; about 3A and if one assumes the extraneous moisture of the airdried sample formed at least a monomolecular layer, one should expect a o difference of 3A in the 'C' spacing of the air and ovendried clay o i samples rather than the observed value of 1.09A. ; 3. The ovendried dodecyl ammonium bentonite had a 'C* spacing ! o o jof 15.78A (Table III). Taking II.63A as the basal 'C spacing, this ; © . . icorresponds to an increase of ii.l^A in the interlattice distance, j (which also is approximately the van der Waal's diameter of a methyl U8 group. This indicates, as others have found, that the dodecyl amine chain was lying flat on the clay surface. However, for the dodecyl o ammonium bentonite, Jordan observed an increase of 8A in the 1C* o spacing over the basal spacing 9 ,6 k , He computed that for dodecyl ammonium bentonite, the basal plane surfaces were covered with the amine chains to the extent of 57$. Hence, two clay platelets with o their amine coating could approach each other no closer than 8A, or the equivalent of two hydrocarbon thickness. If, however, for some amine salt the basal surfaces are covered to the extent of 50$ or o less, the effective separation would be only 1*A. This is illustrated below: (a) V / / M / M / / / A - coverage amine coating clay platelet amine coating (b) v / j r n O f i i i A 1 t t " i-------- -T-. . ~ mm coverage In our sample of dodecyl ammonium bentonite, the amine coating seems to be monomolecular and if one follows Jordan’s line of thought, one would be inclined to infer that in our sample of dodecyl ammonium bentonite, the bentonite clay platelets had only 50$ or less of their k9 j i surface covered by the amine chain. | i I If the basal plane surface determines the colloidal property of | i the clay, a $0% surface coverage by the amine chain would strike an j equal balance between the hydrophilic and oleophilic properties of the J i clay. A surface coverage of less than 50$ would indicate predominance j of hydrophilic surface but our sample of the dodecyl ammonium bentonite j I behaved essentially in a maimer which paralleled Jordan's findings (see sedimentation volume experiments, Chapter V). So it appears that | I the dodecyl ammonium bentonite we prepared was oleophilic. To j compromise between these two conflicting notions, we can only speculate! i a) possibly there could be some lateral displacement between clay i platelets to accommodate the amine coating in excess of 50% and thus, ) i o maintain an effective separation of UA - V //./. / . / .///X V / / // // M A amine coating , W Z Z Z Z Z Z Z ^ B ^ — cl&y platelet k2222222Zl The lateral displacement may not be as pronounced as to destroy the order necessary for peak formation in the X-ray diffraction pattern. b) Or, possibly the edges of the clay platelet should not be neglected while considering the surface characteristics of the clay platelets. (Jordan neglects them) It may be that the amine chain may fold over along the edges (not to the extent as to produce a strain in the molecule) and the edges accommodate a part of the amine coating such that only $0% or less of the basal plane surface is covered by the 50 amine chain. Yet considering the entire clay surface more than 50$ surface is covered by the amine chain. U. On exposing the dried dodecyl ammonium bentonite to vapors of various solvents, we found the following: (Table IV) (a) At the end of 100 hours of exposure to nitrobenzene, cyclohexanone, and benzylalcohol, expansions in the 1C' spacings o o o observed were 3•86a, 0.29A, and 1.89A, respectively. The amounts of solvents absorbed by the sample in that order were; 10.2, 1.2, and 3.78$. (b) The expansion of the 'C* spacing was of a continuously progressing type rather than stepwise. To understand what we mean by ; stepwise, we have to consider the following: We would assume that the solvent molecules, when they enter the interlattice spaces, would take up a configuration in relation to the surface of the clay platelets which would provide the closest approach of the entire molecule to the surface. This will be the condition of greatest stability whether van der Waal's type of attractive forces : be operative or there be actual hydrogen bonding between the hydrogen “ atoms of the solvent molecules and the oxygen atoms of the clay : platelets. We shall further consider only nitrobenzene and : benzylalcohol and neglect cyclohexanone which showed negligible effect on the 'C* spacing. The most stable configuration for either of these molecules would be with the aromatic rings lying flat on the clay surface. According to Pauling (ll*) one could picture the nitrobenzene | and benzylalcohol molecules as illustrated below schematically - I °* , G I 3*7A_ I f phenyl ring nitro group < > o o The plane of nitro group is parallel to the plane of phenyl ring. So effective thickness of nitrobenzene molgcule when lying flat on the clay surface is 3.7A. phenyl group ; Here -CH2 OH group would determine the effective thickness of the benzylalcohol when it assumes a j configuration which has the benzine ring flat on the clay surface. Effective thickness U.OA. i The above thicknesses can be used to at least interpret the rC' spacing expansion somewhat quantitatively. They represent van der Waal’s type of binding. i Theoretically, one would expect that even the introduction of one molecule of a solvent in each of the interlattice spaces should result in a separation of the clay platelets equalling the effective thickness of the solvent molecules. From this point on, as more solvent is imbibed, the first molecule layer of the solvent on the surface of the platelet would be completed. No further changes in i 52 jthe 'c' spacing should be observed during this stage. If there could jbe formation of multilayers of solvent, the 'C' spacing should go up iby units of the effective thickness of the molecule. This is thus a istepwise separation. For dodecyl ammonium bentonite, this could be I ! represented schematically as follows: ¥ZZZ77// / / / / / & 7 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Solvent Molecules (O) ^ / / / / J ^ //^ ] p xPanded O O P . N Spacing OOOGO Y//////AOQOOO O O O CG Q YA Multiple layers followed by V//S///A Z/////z Ultimate Dispersion ^ Q Q Q O \////7 7 M Y//////A OOOOOOO Monomolecular Formaltioh ! of Solvent Layer ! ' The schematical representation of solvent imbibition brings out one additional point, i.e. the solvent molecules come into contact with; ithe amine coating as well as the hydrophilic surface of the clay jplatelet. Therefore, for a solvent to be imbibed on the dodecyl i ammonium bentonite crystallites, it should solvate the organic coating effectively (Jordan's organic character of solvent) and be effectively adsorbed on the exposed hydrophilic surface (Jordan's polarity ;requirement of solvent). ! j | Nitrobenzene has a dipole moment of 3*95 in debye units compared ; 53 | j to 1.6? for benzylalcohol (16). Both have in common the aromatic j i | I ring. So, one could explain on the basis of greater polarity of ! > r i ! O j nitrobenzene the greater expansion of ' C' axis 3.86A as compared to | { 0 ! I.89A for benzylalcohol for 150 hours' exposure, as well as the greaterI ! uptake for the former. I As previously mentioned, instead of stepwise expansion of 'C' lattice on exposure, we observed progressive expansion in fractions of effective thickness of the solvent molecules. After 6 hours' exposure j to nitrobenzene, the sample picked up 0.66$ solvent and showed an | 0 | expansion of 0.^3A, or only 11$ of the effective thickness of the | nitrobenzene molecule. With benzylalcohol for the same amount of exposure, 0.56$ solvent was imbibed, and expansion in 'C' spacing was only 8.5$ of its effective molar thickness. I ! We shall consider two possibilities - i 1. (a) , dodecyl ammonium jgentonite crystal ' C* spacing 15.78A (b) dodecyl ammonium bentonite exposed to solvent. 'C' spacing expanded due to uptake of solvent molecules. su Supposing that the sample was a mixture of the two types of I crystallite; one would obtain their two discreet peaks, one | corresponding to each spacing. There should not be an overlap of the * ; two peaks which can possibly give an intermediate peak position | because the effective thickness of the solvent molecules are 3*7 or I ° [ liA, which corresponds to a 2 9 value of about 1° in this region of ; 'C* spacing values. i j • • . . . j 2. Supposing that in a single crystallite we have mixed layers i i as illustrated - j ! Z Z H Z ^ . 7 B I : --L : 1 ______ p-l5.7& + solvent thickness j In this case no resolution to two peaks, as (1.) would be : observed. The peak that will be obtained would correspond to a mean value of the two spacings depending on the proportion of the two, as well as their distribution. This type of explanation has been offered for the continuous change in the 1C* spacing observed while studying ; o o : the passage of nongraphite carbon (3.i*i|A) to graphite carbon (3.35>A) ;'(5). The continuous change in the *Cr spacing of dodecyl ammonium ;bentonite on exposure to solvents can be explained on this basis. As 'more solvent was imbibed, the proportion of expanded lattices in a jcrystallite increased and the mean 'G' spacing value increased. I Whether we reached a steady state in 15>0 hours1 exposure is I uncertain. However, in the time of exposure, it appears nitrobenzene I | ' molecules formed a monomolecular layer around the clay platelets, i o ! while for benzylalcohol the expansion of I.89A corresponded to about i j half of a molecular thickness. Presumably, this can be explained on j the basis of mixed spacing in the crystallite. I 0 j The difference of 1.09A in the 'C1 spaeings of airdried volelay i ° j bentonite and ovendried volelay bentonite, instead of 3A corresponding i to one molecular layer of water, probably can be explained on the i same basis of mixed layers; some being hydrated, and some not. ! | ! 5. The 10, 20, and 33$ dodecyl ammonium bentonite - nitrobenzene 1 i i systems gave diffraction patterns which were diffused and no peaks j were evident (Table V). A 90$ gum tragacanth - 10$ dodecyl ammonium . bentonite gave a peak which corresponded to the peak position of 1 dodecyl ammonium bentonite although the intensity of the peak (i* chart ■ divisions) was considerably less than that obtained with the dodecyl ; ammonium bentonite alone (20 chart divisions) (Figure 11). So, the absence of peak in 10$ dodecyl ammonium bentonite - ; nitrobenzene system was not due to excessive dilution of crystallites with an amorphous diluent. Presumably in this system, there was ; complete dispersion of the clay platelets, which was responsible for i the diffused diffraction patterns. With cyclohexanone on the other hand, the 33$ system gave a peak - ;at 2 6 = 5.60, which corresponded to the basal spacing of the dodecyl | ammonium bentonite crystals. This indicates in cyclohexanone the | dispersion of the dodecyl ammonium bentonite was poor, which agrees 1 \ with our experiments on sample exposures to solvents. | | On the basis of these experiments, then it appears that | | nitrobenzene is the superior solvent for dodecyl ammonium bentonite - 2 I ' i this is in agreement with Jordan (10). CHAPTER V J ! | SEDIMENTATION VOLUME EXPERIMENTS i Significance of Volume Occupied by Powdered Solid in Liquids In the previous chapter, we have described the X-ray diffraction experiments with dodecyl ammonium bentonite. It seemed that in ! ! nitrobenzene, the dodecyl ammonium bentonite was solvated to the i | greatest extent (as judged from the largest expansion of 'C' spacing, j ! | | obtained from exposure to the solvent), whereas solvation capacities j j # ! | of benzylalcohol and cyclohexanone were significantly poorer. | | i I When a powdered solid is suspended in different liquids, the j ! ! I character of dispersion may be observed by the final relative volumes i I ! . of the suspended solid. This method has been used by many i • investigators and the results are sometimes of considerable interest j ! ! ! because difference in both solids and:liquids may be examined and j i [ ( f | the influence of reagents may be studied (U). j ! ' ' i ! . A < ; The volume occupied by an alkyl ammonium bentonite in various i | organic solvents was given great importance by Jordan (10). He 1 . i j considered these volumes as 'swelling volumes' and inteipreted them j as a measure of oleophilic property of the alkyl ammonium bentonite ' i I • * j in various organic solvents. j i This method that was used by Jordan (10) may possibly be the ! determination of the spontaneous swelling volume of the powdered alkyl i ammonium bentonite, when in the presence of a large excess of the i ; 58 |liquid. His technique consisted of dropping the powdered sample I carefully, in portions, into the solvent in a 100 or 2$0 ml graduates, so that each portion was allowed to settle before the next was added. 1 |The sample in the liquid was allowed to stand for 2U hours and the ! volume was observed. I I J An inert material-like titanium dioxide will settle in organic |solvents and occupy an equilibrium sedimentation volume, which will |depend on the particle size, wettability of the particle in solvent, jetc.. Energetically, the system would assume a state whereby it s ipossesses the least free energy. j If the liquid is pure, the equilibrium sedimentation volume for a 'given solid have been correlated with the interfaeial tensions of the liquids measured against water or with the corresponding spreading coefficients. For powders that could be described as hydrophilic, in liquids of high spreading coefficients, the sedimentation volume is low; in liquids of low spreading coefficients, the volume is high (1*). Experiments of Ostwald and Haller (3) on sedimentation of hydrophilic pigments in various organic solvents showed a correlation between dielectric constant of the liquid and final volume of solid. The trend was towards lowest volumes in liquids of highest dielectric constant. For hydrophilic pigments suspended in a liquid of high ; interfaeial tension against water, the sedimentation volume was high. For solids which were hydrophobic, high sedimentation volume was associated with high spreading coefficient of the liquid against water. 5 ? ; These results seem to indicate that for hydrophilic solids, good j j * dispersion is likely to result in a low sedimentation volume, whereas j ! ' ! , any degree of flocculation would tend to increase the sedimentation j « * i i j volume. This can be also visualized as dependent on the extent of j j i I surface wetting. The more completely the surface of a polar solid is 1 i - j : wetted by dispersion medium, the greater is the deflocculation of the I i | | particles and smaller the sedimentation volume. No such generalization) ! j | has yet been suggested for nonpolar solids. McBain (15) is of the j ! | I opinion that changing the liquid does not affect the sedimentation I i I : volume of nonpolar graphite. However, Ross and Schaeffer (15) found j i | j that for graphite and water dioxane mixtures, the sedimentation volume J i I | decreased on increasing dioxane percentage in the mixture, indicating ! < I f I ! that better surface wetting by dioxane resulted in deflocculation and ■ i . ' ; lower sedimentation volume. i i I One, however, encounters another class of systems like rubber in ' | : organic solvents or hydrophilic bentonite clay in water, where the ; solid phase imbibes the liquid and as a result, undergoes a process of * swelling (16). The extent of swelling may be limited or may result in ( 1 complete deflocculation of the solid phase. The volume occupied by the dodecyl ammonium bentonite in the | organic solvents could be either a sedimentation volume or a } j spontaneous swelling volume, as Jordan claims. A decision between the \ two is important. Moreover, whether the volume occupied by the solid i after 2k hours in the liquid represents an equilibrium volume, as | 60 Jordan measured them, is also important to know. We planned two series of experiments to gain some knowledge about the dodecyl ammonium bentonite - organic liquid systems. These were primarily intended to find out whether these volumes were equilibrium volumes. However, the same experiments permitted us to establish the comparative j volumes of the dodecyl ammonium bentonite in a variety of organic | solvents. i i \ | Materials i | i | The dodecyl ammonium bentonite, Batch I, which was dried at 65°C j I I for 3 days and then ground in a mortar until it appeared finely j i powdered was used for our study without any further drying over j | powerful desiceants like phosphorous pentoxide, etc.. Such precautions j ! are worthwhile because even traces of water may affect settled volumes ; j I of powdered solid in liquids quite considerably. However, in view of j ■ the exploratory nature of our work, the omission of this step is j perhaps understandable even though not quite justifiable. However, i ' ; we did store the dodecyl ammonium bentonite over calcium chloride in ia desiccator prior to use. i i The solvents used are listed below - j 1. Nitrobenzene (C.P) Braun Corporation I 2. Toluene (C.P) Baker Chemical Company ! \ \ 1 3. Ethyl Acetate (C.P) Baker Chemical Company J 4. Benzylalcohol (C.P) Mathieson Co., Inc. ! 5. Furfural (C.P) Mathieson Co., Inc. 1 6. Cyclohexanone (C.P) Mathieson Co., Inc, j * ' I j 7. Pyridine (Reagent Grade) Allied Chemical and Dye ! i Corporation • - ! j 8. Benzonitrile (C.P) Eastman Kodak Company j j j i 9. Methylalcohol (Absolute,refined) Merck and Co., Inc. I | j \ ! j : Methods i 1 1 ■ I I As noted previously, we planned two series of experiments. In i ! Series I, we first established the spontaneous settling volume as I I follows: The organic liquids were taken in a number of one hundred I ■ milliliters graduates in quantities ranging from 90 to 95 milliliters. \ ; . I The weighed amount of dodecyl ammonium bentonite was then dropped j I i i into them very carefully in several portions so that each portion was j i ! i allowed to settle before the next was added. The graduates were 1 j stoppered and after standing at room temperature for 2k hours, the settled volumes were noted. ; I ! As it would be noted that in the above experiments the complexes were allowed to settle under gravity without any mechanical dispersion,1 | we wanted to investigate the effect of shaking on these settled | volumes. So, these graduates were shaken vigorously for 5 minutes I and then the volumes of the settled complexes were observed over a i period of time. i , In Series II experiments, the dodecyl ammonium bentonite was . weighed in 15 mis graduated centrifuge tubes, and a total of lli mis ! of solvent was added to it* The test tubes were shaken well for 62 I ! about 5 minutes and then, a milliliter of the solvent was added to i | wash down the solid particles adhering to the sides of the tube. ! | I I They were then stoppered and left undisturbed at room temperature. ) j • ! I ; j The settled volumes were observed after 21* and 1*8 hours. They were j then centrifuged at a speed of 2000 RPM for 15 minutes, and then the i 1 i j I volumes were observed over a period of time. j j j I i { Results of Sedimentation Volume Experiments j { The results are given in Tables ¥111 to XI. I ; * ! ! i ! TABLE VIII SERIES I - VOLUMES OF DODECIL AMMONIUM BENTONITE IN VARIOUS ORGANIC SOLVENTS. THE SOLVENTS WERE TAKEN IN 100 MLS GRADUATES AND THE SOLID DROPPED IN THEM. NO MECHANICAL AGITATION. Solvent Weight of Dodecyl Ammonium ' Bentonite (grams) Volume of Solid Phase after 21* Hours(mis) Remarks 1. Nitrobenzene 2.02 The system was cloudy; on tipping the cylinder over its mouth, large lumps adhered to the bottom and walls of the graduate. 2. Ethyl Acetate (10) Toluene (90) 2.01 23.0 Easily flowing suspensions. 3. Methylalcohol (10) Toluene (90) 1.12 33.7 Easily flowing suspensions. k* Benzonitrile 1.28 10.0 System extremely adherent to the cylinder walls. On tilting the cylinder on its mouth it did not flow at all. f>. Benzylalcohol 1.11 9.0 Rather easily flowing; on tilting the cylinder on its mouth, soft lumps adhered to the side and bottom of the cylinder. 6. Furfural l.liS 13.0 Rather easily flowing; on tilting the cylinder on its mouth, soft lumps adhered to the side and bottom*of the cylinder. On V j J TABLE VIII (Continued) Solvent Weight of Dodecyl Ammonium Bentonite (grams) Volume of Solid Phase after 2k Hours(mis) Remarks 7. Cyclohexanone o.?£ 7.0 Rather easily flowing; on tilting the cylinder on its mouth, soft lumps adhered to the side and bottom of the cylinder. 6. Pyridine 1.07 lluO Rather easily flowing; on tilting the cylinder on its mouth, soft lumps adhered to the side and bottom of the cylinder. TABLE IX 1 SERIES I - VOLUMES OCCUPIED BX DODECXL AMMONIUM BENTONITE IN VARIOUS ORGANIC SOLVENTS ! FOLLOWED WITH TIME AFTER SHAKING VOLUME IN SOLVENTS IN MLS Time of Observation Nitro benzene Ethyl Acetate (10) Toluene (90) Methyl- alcohol (10) Toluene (90) Benzo- nitrile Benzyl alcohol Furfural Cyclo hexanone Pyri dine l5 min. after shaking Complete 51.0 No boundary observed 8.0 U.5 2 i*.5 No boun dary ob served 25 min. after shaking a O H- - ry 0 1 .......... 36.0 No boundary observed 8.6 8 3 5 15.5 • 1*5 min. after shaking c o CD c t > 3 2 33.0 No boundary observed 9.0 11 ( - ‘ •’ O CO < S3 O © CD O CO c+ 4 H C f t W- Vd 5.2 i5.o 1 hr. 35 min. after shaking CD H- 0- O P 31.0 88.5 9.0 10.8 clc led ible emer 5.5 13.0 3 hrs. after shaking g 30.0 65.5 9.8 9.0 c *- CO £ M (+ ® Q, O O . H M. M- 5.9 13.0 9 hrs. after shaking CO © c +- 30.0 60.0 10.0 8.5 S h < 6 © a o 13 o 6.0 12.5 21 hrs. after shaking ... . . . . . ^ — H H* f c J c m 30.0 1*9.0 10.0 9.0 e the . Not furthei lume. 6.0 13.0 i TAB1E IX (Continued) i Time of Observation Nitro benzene Ethyl Acetate (10) Toluene (90) Methyl- alcohol (10) Toluene (90) Benzo- nitrile Benzyl- alcohol Furfural S a B < Cyclo- hexanone Pyri dine U6 hrs. after shaking 0 s S B 29.8 UO.O 11.5 8.8 p £ < & c * - H tf‘ Ns O ® O H- p 3 C O a H t s H • ' T O 0 c+ H; 0 ) 0 6.0 13.5 70 hrs. after shaking c+ ® c* <+ H ® h i 2 9.8 35.0 12.5 8.5 O ® H cL'q H ^ C D H* g 3 ® 3 H* ( D . Ct 6.0 13.5 9h hours after shaking t s & o t j H‘ C f l n * r 1 29.8 . 33.0 12.5 8.5 i y b t? «r . 0 <+ < 4 » ® ® 6.0 13.5 11 days after shaking cr ® w 1 < D C O H M. 29.6 29.0 lil.5 B.5 1, 7 6.0 13.5 15 days after shaking < 0 ® 0 29.3 28.5 15.5 B.5 7 6.0 13.5 36 days after shaking 29.3 28.5 19.5 8.5 . 10 6.0 13.5 Volumes originally occupied before shaking «3.5 23.0 33.7 10 9 13 7 ili.o I TABLE X SERIES II - VOLUMES OCCUPIED BY DODECYL AMMONIUM BENTONITE IN VARIOUS ORGANIC SOLVENTS i i Nitro benzene Pyridine Cyclo- hexanone Benzyl- alcohol Methyl alcohol (10) Toluene (90) Furfural j Weight of Sample 0.21*89 0.273k 0.1908 0.1987 0.1$83 0.21*1*2 I in grams j ( AFTER 21* HRS. 8.1* 1.70 1.20 1.10 1.90 1.62 1 Volume in mis ( settling i ( AFTER 1*8 HRS. 8.1*2 1.69 1.20 1.10 1.90 1.62 | ( IMMEDIATELY :Volume after ( AFTER L.70 0.9$ 0.7$ 0.60 1.20 1.00 !Centrifugation( AFTER 12 HRS, 1*.80 1.0^ 0.90 0.68 1.30 1. 0$ ( AFTER 18 HRS. 1*.80 1.0$ 0.90 0.68 1.30 1.0$ 1 ( AFTER 21* HRS. l*.8o 1.0$ 0.90 0.68 1.30 1.0$ ! ! ON -J TABLE XI SPECIFIC VOLUMES OF DODECXL AMMONIUM BENTONITE IN VARIOUS ORGANIC SOLVENTS i Observed Volume Computed for One Gram of Dodecyl Ammonium Bentonite SPECIFIC VOLUMES Solvent Series I Series II Before Shaking 28 Hrs. Standing 38 Days After Shaking Before Centrifuging 28 Hours Standing 28 Hours After Centrifuging Nitrobenzene 81.5 Stable Sol 33.70 19.30 Metbylalcohol (10) Toluene (90) 30 25.5 12 8.22 Pyridine 13.1 12.6 7.98 8.93 Furfural 11.6 8.5 6.69 8.51 Ethyl Acetate (10) Toluene (90) 11.5 1U.6 Cyclohexanone 9.8 8.0 6.30 ii.72 Benzylalcohol 8.1 7.7 5.53 3.82 Benzonitrile 7.8 15.2 •• - i Discussion of the Sedimentation Volume Data l«lll«nm»l.l Ml ■ I I ——— — I ■■■■■■WIHII—! ! ■ ■ ■ HMWI— —« — — . I I H I . — I I . . ! ■ 1 ■■■■■■■ ■■ ■■ H I M ■ ! The following points are brought out from the data given in i | Tables VIII to XI: ! I j 1. The absolute magnitude of the specific volumes of dodecyl ! ammonium bentonite in various organic liquids do not agree between j Series I and II, observed under conditions of ’spontaneous swelling' 1 ; following Jordan (10)(Table XI). The explanation for it can only be i \ guessed. There were some differences in the techniques. In Series I, i i the dodecyl ammonium bentonite was dropped in portions into the liquid, i ] ! whereas in Series II, the solid was wetted by adding the liquid. This I difference may be significant when the medium has poor dispersion i : power, especially when little or no mechanical dispersion was used. i ; Secondly, it is not certain all these solid samples which varied ; greatly in amount had equivalent particle size distribution. = 2. The specific volumes in both series, however, followed the order - nitrobenzene>methylalcohol (10) - Toluene (90)y pyridine > furfural> cyclohexanone> benzylalcohol. This is essentially the : order that Jordan obtained except in his experiments, furfural gave a i greater volume than pyridine. 3. Apparently the specific volume of the dodecyl ammonium ; bentonite is dependent on the nature of the solvent. However, in this icase, if one tries to correlate these volumes with the degree of I dispersion and consider these volumes just sedimentation volume, one !has to infer then, that in benzylalcohol, the finest dispersion of I the dodecyl ammonium bentonite was obtained and the least in i j nitrobenzene. However, when the Series I samples, after standing for j | i J ' i ! 2k hours were shaken, nitrobenzene - dodecyl ammonium bentonite system j j was converted to a stable sol which did not settle in 38 days' j 1 standing, whereas in the corresponding benzylalcohol system, within j | 15 minutes of shaking, a sediment was observed whose volume was 50% I of the final volume (Table IX). It appeared from these data that the I | complex was poorly dispersed in benzonitrile, benzylalcohol, furfural, 1 ! and cyclohexanone because in each of these systems, a sediment I appeared within 15 minutes after shaking which increased in volume J with further sedimentation. In ethyl acetate - toluene and | 1 metbylalcohol - toluene, the dispersion was finer because here a | 1 | boundary gradually receded from the top and no sediment was observed 1 | within 15 minutes from shaking. 1 • On these bases, one is tempted to consider these volumes as ‘ 'spontaneous swelling’ volumes, similar to the rubber - benzene system.' i In the case of the dodecyl ammonium bentonite, a swelling tendency 1 t , could arise by virtue of the solvation (or solution) of the dodecyl I 1 ! 1 iamine chain in the solvent. By this means the fugacity of the solvent ; inside the crystal lattices would be reduced and solvent from the | outside having higher fugacity would force its way into the inter- | 1 jlattice spaces. However, during this process, as illustrated ; I I schematically (Chapter IV, Page 5?), the solvent molecules would come , j into contact with the exposed hydrophilic surfaces of the clay 1 i j ; platelets and the extent to which the clay platelets would be solvated j ; and swell will depend on the adsorption energy of the solvent molecules: i ; | for the hydrophilic surface. i Moreover, it appears that these volumes are dependent on the I ! i : suitable balance between the forces of aggregation and those of j 1 ; | dispersal. For forces of aggregation, the lyophobic spot theory of j ! Bungenburg de Jong (2,18) can be applied to these systems. The forces j i i I t I of aggregation would be the attraction between the lyophobic spots of : j j i the clay platelets (exposed hydrophilic surfaces on the basal plane or : ; } i ' on the edges of the platelets) and forces of dispersal would be the I swelling pressure of the solvent and thermal motion of the particles. | . ■ Nitrobenzene compared to other solvents evidently strikes the t | best balance between these forces of aggregation and dispersion. It : solvates the amine chains well, and by virtue of its high dipole : moment, can also decrease the forces of aggregation among the lyophobic; ;spots. A solvent which either lacks the capacity to solvate the amine chain, or has no polar nature to be adequately adsorbed on the lyophobic spots, would show inferior swelling volume. Even with nitrobenzene, only limited swelling is observed; hence, some forces of aggregation due to existence of lyophobic spots must be operative. The failure of the nitrobenzene - dodecyl ammonium bentonite system and others to go back to starting condition on either mechanical shaking or centrifuging (Tables IX and X) may indicate that for the :former case, the forces of aggregation were overcome by the mechanical i energy and the dispersed clay platelets arranged themselves such that ' i ; ! the lyophobic spots were farther from each other, and also the i I i : ■ I ! adsorption energy of nitrobenzene for these spots was adequate to ! I ■ i j stabilize the system. In solvents where such conditions did not ! jprevail (benzylalcohol, etc.), there was immediate settling of the ! jpoorly dispersed particles. On centrifugation of the nitrobenzene j j | system, the compression of these day platelets cause them to S 5 • I i ; | interpenetrate such that lyophobic spots in any one aggregate come i J I in contact with lyophobic spots in the neighboring aggregates. . So, j ! ; \ 1 at this stage, forces of aggregation predominate. j f . j ! The sedimentation volume experiments in essence agree with the • | ’ ; X-ray diffraction data. It appears that by far, for dodecyl ammonium j !bentonite, nitrobenzene is the most suitable solvent. i It would have been interesting if we could determine the :solubility of the dodecyl amine in various organic solvents, and also could measure the heat of adsorption of these solvents on the i , hydrophilic bentonite surface. This can possibly lead us to a point .where we could semewhat quantitatively distinguish between these I ; : organic solvents in regards to their behavior towards an alkyl i : ammonium bentonite. A direct correlation between the 'swelling volumes' of dodecyl ammonium bentonite obtained by Jordan, and properties like dipole moment or dielectric constants of the solvents, is nonexistent ( 16). CHAPTER VI SUMMARY i The dodecyl ammonium bentonite - organic solvent systems were studied through X-ray diffraction methods, as well as sedimentation volume determinations. The results from these two different types of experimentation compliment each other. In both cases, nitrobenzene was found to have the greatest intensity of solvation for the dodecyl ammonium bentonite. "When dodecyl ammonium bentonite was exposed to organic solventsj i | nitrobenzene showed the greatest expansion of the 'C* spacing, j benzylalcohol was next, with cyclohexanone least. However, the i jexpansions were continuously progressive type rather than stepwise. t | ! This was explained in terms of a crystallite having mixed layers : (Chapter IV). I i The 10, 20, and 33% dodecyl ammonium bentonite - nitrobenzene j • ! systems gave diffused diffraction patterns, whereas the corresponding I 33% cyclohexanone system gave a peak which corresponded with the 1 I ; basal 'C* spacing of the dodecyl ammonium bentonite. This is also i ■ indicative of ultimate dispersion of clay platelets in the i | nitrobenzene systems. These systems had a high consistency because j j they did not flow on tipping the vials in which they were kept. 33% ! | cyclohexanone system was much easier flowing (Chapter IV). i It appears the sedimentation volumes are possbily 'swelling I 7k \ volumes.' The degree of swelling is dependent on the balance of t | aggregating forces and dispersal forces which depend on the nature of i I solvent. This is discussed in terms of lyophobic spot theory of I I j Bungeriburg de Jong. The mechanism that is presented for the ! j explanation of large sedimentation volume can be easily extended to a 1 | speculative discussion of mechanism of gel formation. The diagram illustrates this: Swelling Volume Dodecyl Ammonium Bentonite + Solvent (Sedimentation Volume) Limited Swelling Stable Sol Weaker Gel Stronger Gel ------1 j Of the questions we raised in Chapter II, we have probably been j |able to answer question (1.) which was to understand why the dodecyl i • ammonium bentonite behaves diversely in various organic solvents. Regarding question (2.) on a mechanistic picture of gel formation i of these alkyl ammonium bentonite in organic solvents, no clear cut ;decision could be made; however, it appears that solvation does play i ;an important part in gel formation. j REFERENCES | i 1. Alexander> A* E*, and Johnson, P., Colloid Science, Vol. 2, I 1 i ! ) I Chapter XXV, Published by Oxford University Press, 19U9 Edition. i | 2. de Jong, Bungenburg, Zeitschrift fur Physikalische Chemie., i | 130, 205 (1927). f ! 1 1 i 3. Donald, M. B., Chemistry and Industry, 59, 105 (19U0). i ! I it. Fischer, E. K., Colloidal Dispersions, pp. 108-113, Published i ! ! I by John Wiley and Sons, 1950 Edition. j i 5. Franklin, R. E., Acta Crystallographies, it, 253 (1951). i 6. Graham, R., and Sullivan, J., J. Am. Ceram. Soc., 21, 176 (1938). | j i I 7. Grandine, J. D., Ph.D. Dissertation, University of Southern j | California, (19it9). ! j 8. Hauser, E. A., and LeBeau, D. S., Colloid Chemistry, Edited by i i Alexander, J., Vol. VI, p. 191, Reinhold Publishing Corporation, 19U6 Edition. . 9. Hendricks, S. B., J. Phys. Chem*, k5, 65 (I9itl). 10. Jordan, J. W., J. Phys. Coll. Chem., 53, 29k (19k9)s 55, 1196 (1950). 11. Lewis, W. K., Squires, L., and Broughton, G., Industrial Chemistry i of Colloidal and Amorphous Materials, pp. it5l-it53, Published by ! Mcmillan Company (19lt2). 12. Lloyd, D. J., Colloid Chemistry, Vol. I, p. 767, 1926 Edition, Edited by Alexander, J., Published by Chemical Catalogue Co., Inc. j 13. McEwan, D. M. C., Trans. Faraday Soc., U;, 3k9 (19U8). | I i lil. Pauling, L. C., The Nature of Chemical Bond and Structure of ; Molecules and Crystals, Cornell University Press (1939). j i 15. Ross, S., and Schaeffer, H. F., J. Phys. Chem., $ 8 , 865 (195U). j . I 16. Sanyal, P. N., Research Report 7901., June, 1952. ! ! 17. Schott, H., Masters Thesis, University of Southern California j (1951). I 5 18. Stratton, C. A., Ph.D. Dissertation, University of Southern j California (1952). j j 19. Void, M. J., Final Technical Report on the Project, X-ray Studies j t of the Orientation of Compacted Asymmetric Particles, Contract j da-0U-4*95-QRD-3©3, August, 1953. j i 5 Gniversity of Southern California

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Creator Sanyal, Pulak Nath (author)

Core Title Studies on the organophilic montmorillonites

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