Berlinger, H.

Grasselly, Gyula

English

Three montmorillonite-amino acid complexes (montmorillonite-glicine, montmorillonitearginine and montmorillonite-lysine) were prepared. The complexes were studied by DTA, X-ray and IR-spectroscopy. DTA measurements indicate a strong interaction between montmorillonite and organic material. .There is a mutual stabilization as evidenced by the shift of peak temperatures of both the structural decomposition of the montmorillonite and the decomposition of the organic material. X-ray measurements support the results obtained by other methods. IR-spectra support the existence of the montmorillonite-organic material interactions. Complex formation brings about such conjugational relationships which result in the appearance of a new absorption band in the IR-spectra

Berlinger H.

Grasselly Gyula

University of Szeged

Acta Mineralogica—Petrographica, Szeged, XXII//1, 159—164, 1977 S T U D I E S O N P R O P E R T I E S O F M O N T M O R I L L O N I T E - A M I N O A C I D C O M P L E X E S H . BERLINGER a n d GY. GRASSELLY ABSTRACT Three montmorillonite-amino acid complexes (montmorillonite-glicine, montmorillonite-arginine and montmorillonite-lysine) were prepared. The complexes were studied by DTA, X-ray and IR-spectroscopy. DTA measurements indicate a strong interaction between montmorillonite and organic material. .There is a mutual stabilization as evidenced by the shift of peak temperatures of both the structural decomposition of the montmorillonite and the decomposition of the organic material. X-ray meas-urements support the results obtained by other methods. IR-spectra support the existence of the montmorillonite-organic material interactions. Complex formation brings about such conjuga-tional relationships which result in the appearance of a new absorption band in the IR-spectra. INTRODUCTION The well known characteristic of clay minerals is that they readily take up organic matter [EGLINTON, 1969]. Montmorillonite especially features that habit. Montmorillonite stabilizes the absorbed organic material against bacterial degra-dation, and — under favourable conditions — catalyzes the alteration of the organic substance. However, in the course of the transformation of the organic material, montmorillonite itself turns into a more "illite-like" material [ROLOFF, 1965]. TSUNASHIMA et al. [1975] carried out hydrothermal synthesis of montmorillonite-lysine, montmorillonite-glicine and ammonium-mica complexes, respectively. It was proved that the organic component can play an important role in clay formations during the sedimentation and the following diagenetic phases. This paper reports on the preparation of montmorillonite-amino acid complexes. In the course of the work the amino acid uptake of a given montmorillonite, the type of changes effected by the built-in organic material upon the structure of the montmorillonite, the presence and type of interactions between the clay mineral and the organic matter and their effects upon the thermic properties of the materials involved were studied. EXPERIMENTAL Experiments were started with Mad-Koldu (Hungary) bentonite as raw mate-rial. X-ray diffractometric and DTA measurements revealed that this material was a mixture of kaolinite and montmorillonite. The raw material was subjected to repeated sedimentation and centrifugation resulting in a practically pure mont-morillonite fraction, with grain size of <0.5 micron. Complexes were prepared from that montmorillonite and analytical grade amino acids. 159 The cation-exchange capacity of montmorillonite was determined by the NH4Cl-method according to HOFMANN and GIESE. Absorption isotherms were obtained at constant pH, equilibration period, temperature, and amount of the absorbent and only the amino acid concentrations were changed. 2 g absorbents were weighed, mixed with 40 ml distilled water, then agitated for 20 hours on a shaking machine. Different amounts of amino acids corresponding to the different concentration levels were weighed and dissolved in distilled water, then, in turn, added to the montmorillonite suspension. The pH was adjusted and the volume- of the suspension was brought to 100 ml. The pH values of the montmorillonite-glyci-ne; montmorillonite-arginine and montmorillonite-lysine complexes were 3,2, 8 and 9 respectively. This procedure was followed by a 24 hours mechanical agitation-equilibration procedure on the shaking machine. The complex was cenrifuged, the supernatant phase separated and sampled for an automatic amino acid analyser to determine the amounts of the unreacted amino acids. The complex obtained was washed four times with 60 ml portions of distilled water. Part of the complex was subjected to DTA, the other part to X-ray investigations. A suspension of 0.5% of the complexes was prepared and the clay mineral-amino acid complex was sedi-mented onto a sample holder to obtain an oriented sample. Having determined the conditions of the greatest amino acid uptake on the basis of adsorption isotherms, larger quantities of the complexes were prepared and their DTA curves were recorded. Transformation temperatures of the complexes were determined from the DTA curves, then 2 g samples of the respective complexes were subjected to heat treatment. Complexes were heated for an hour in N2 or air stream in tube furnaces at predetermined temperatures. DTA curves of the heat-treated samples were also recorded. Infrared spectra of both the montmorillonite, the original and heat treated complexes were recorded. 800 mg spectral grade KBr and 3 mg material to be tested were mixed, homogenized and pelletized. , RESULTS The cation-exchange capacity of montmorillonite was found to be 96 meq/100 g. Based on the adsorption isotherms the maximum amounts of amino acids adsorbed 250 meq/100 g; 560 meq/100 g and 585 meq/100 g in the case of montmorillonite-glicine, montmorillonite-arginine, and montmorillonite-lysine complexes, respectively. However, it should be noted that only apparent absorbed quantities can be spoken about. That means that only a part of these amounts are bound by chemosorption and incorporated into the clay-structure. The greater part of amino acids is bound only by physical absorption forces to the surfaces. It is evidenced by the fact that having subjected the complexes to vigorous agitation and repeated washings, most of the originally absorbed amino acid is removed. The considerable amount of amino acid thus returned into the solution stabilizes the suspension, so the complex can not be separated during the usual centrifugation time. X-ray diffraction studies X-ray diffraction measurements support the results of DTA measurements to be discussed below. The d001 values are 12.44 A; 13.38 A and 13.48 A in the case of the montmorillonite-glicine, montmorillonite-arginine and montmorillonite-lysine comp-lexes, respectively. These figures agree well with data in the literature. 160 DTA measurements When the complexes obtained by determining the absorption isotherms ex-periments were studied, it was observed that only a part of the absorbed amino acid is incorporated into the montmorillonite structure. The amount of organic material could be evaluated from the weight losses observed on the TG curves. These calculations may be to a certain extent imprecise, yet this fact does not effect the usefulness of the data obtained. The following cation-exchange capacity values could be derived from the DTA measurements: 33meq/100g; 77meq/100g and 88.3 meq/100 g in the case of montmorillonite-glicine, montmorillonite-arginine and montmorillonite-lysine complexes, respectively. DTA measurements made on complexes obtained at different points of the absorption isotherms revealed that due to the 24 hours long shaking process the amount of the absorbed amino acid did more or less approach the exchange capacity value at quite low amino acid concentrations. Based on the DTA curves of the untreated complexes it can be concluded that there is a strong interaction between the montmorillonite and the organic material (Fig. 1). In the case of the montmorillo-nite-glicine complex the temperature of the second endothermic peak is shifted from 560° C to 590° C, while that of the peak denoting the final structural de-composition is shifted from 870° C to 890° C. Furthermore, an other exothermic peak, so far undetected on the DTA curves of the original montmorillonite, appeared at 920° C. On the DTA curves of the montmorillonite-arginine and montmorillonite-lysine complexes the endothermic effect corresponding to the decomposition of the montmorillonite structure is almost totally distorted and covered by two intense exothermic peaks appearing between 630° C and 730° C. The exothermic effect, however, can well be observed at each these complexes at 930° C and 970° C, -respectively. It can be seen from the DTA curves of the heat-treated samples that the peak temperature values corresponding to the structural decomposition of montmorillo-nite are shifted towards higher temperatures. The montmorillonite-organic matter interaction manifests itself in increased thermal stability of the organic material. The DTA curves-based thermal stability order is as follows: glicine, lysine and arginine. Thermal cracking of the organic substance bound in the complex occurs at a significantly higher temperature than that derived from the melting point. IR-measurements Infrared spectra of the montmorillonite samples agree well with those published by MOENKE [1962], shown in Table 1. It can be seen, that bands belonging to the organic material do not occur equally frequently in the case of different substances (Fig. 2 and 3). Organic bands can best be identified in the case of the montmorillo-nite-lysine complex, while in the IR-spectra of the other two complexes only one band in each can be identified. The organic bands are as follows: y s>CH2 at 1342 cm-1 J3S>CH2 at 1405 cm-1 y?-NH3+ and amide II at 1510 cm"1 vs-NH3+ at 2950 cm-1 and v.,-NH, at 3290 cm-1. 11 161 b) montmorillonite-glycine c) montmorillonite-arginine d) montmorillonite-lysine Bands assigned to the organic substance disappeared in samples subjected to heat treatment at elevated temperatures. Treating the samples at 600° C and 800° C for 1 hour a number of bands corresponding to montmorillonite fundamental vibrations disappeared (at 430 cm"1, 353 cm - 1 ; 925 c m " \ and 3635 cm"1), while new bands appeared (at 740 cm - 1 , and 810 cm -1). There is a dublette at 2370 and 2350 cm"1 in the IR spectra of each complex; a peak nonexistent in the IR spectrum of the original montmorillonite but always present in the complexes. It is probably due to the special conjugation conditions brought about by the complex formation. 162 Fig. 2. Infrared spectra of montmorillonite-amino acid complexes a) montmorillonite-glycine b) montmorillonite-arginine c) montmorillonite-lysine TABLE 1 Major bands in the IR-spectra of montmorillonites Group; type of vibration Wave number range cm"1 Montmorillonite bands in MOENKE's MAD-KOLDU-samples cm"1 cm"1 Fundamental vibrations of the - Si04 tetrahedron and A106 octahedron (600—350) 470 525 630 426 475 530 vs (Si—O)—Si 850—800 850 810 vas (Si—O)—Al(6) 1000—830 920 920 vas (Si—0)—Al(4> 1055—980 1040 1040 vas (Si—0)—Si 1120—1070 1100 1100 p—OH 1680—1600 1650 1650 v H—O—H 3600—3000 3430 3470 v —OH 3760—3520 3628 3630 11* 163 Fig. 3. Infrared spectra of heat treated samples d) montmorillonite-lysine (800 °C) f ) montmorillonite-arginine (420 °C) e) montmorillonite-lysine (600 °C) g) montmorillonite-arginine (320 °C) SUMMARY Results of DTA and IR measurements yield valuable information relating to the montmorillonite-amino acid complexes. There is a mutual stabilization between the organic substance and montmorillonite resulting in 20-40° C higher temperature values for the structural changes of montmorillonite and increased thermal stability of the amino acids. Since the remaining products and none of the gases evolved could be studied by the DTA investigations, it would be proper to extend these tests and to study the gases evolved as well. Bands corresponding to the organic material and montmorillonite occur at separate wave numbers. There are vibrations in the 2370-2350 cm - 1 range, which can be assigned to the complex formation. REFERENCES EGLINTON, G., MURPHY, M. T. J. [1969]: Organic Geochemistry. Springer-Verlag, Berlin—Heidel-berg—New York. ROLOFF, E. K. [1965]: Über die Rolle glimmerartigen Schichtsilicaten bei der Entstehung von Erdöls und Erdöilagerstadten. Diss., Heidelberg. TSUNASHIMA, A . , KANAMARU, F . , UEDA, S., KOIZUMI, M . , MATSUSHITA, T . [1975]: H y d r o t h e r m a l Synthesis of Amino Acid-Montmorillonites and Ammonium-Micas. Clay and Clay Minerals 23, 2. MOENKE, H. [1962]: Mineralspektren. Akademie-Verlag, Berlin. Kiss—ERŐSS, K. [1974]: Az infravörös spektroszkópia analitikai alkalmazása. (Analytical Applica-tion of Infrared Spectroscopy), Műszaki Könyvkiadó, Budapest. Manuscript received, July 10, 1977 H . BERLINGER PROF. DR. GY. GRASSELLY Institute of Mineralogy, Geochemistry and Petrography Attila József University H-6722 Szeged, Egyetem u. 2—6. Hungary 164 

Studies on properties of montmorillonite-amino acid complexes

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Studies on properties of montmorillonite-amino acid complexes

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