Internationale Vereinigung zum Studium der Tone Межлунаролная ассоциация по изучению глин

The members of the Tunisian Clay Group (TCG) Executive Committee are:

	Photo 13: Plenary lecture during XV ICC in Rio de Janeiro, Brazil (Photo courtesy of Fakher Jamoussi).
	Photo 14: Participation of the representative of TCG in the XV ICC in Rio de Janeiro, July 2013, Brazil (Photo courtesy of Fakher Jamoussi).
	Photo 15: Scientific excursion for the students of the University of Sfax in the context of the valorization of Clays organized by the TCG, March 2013. (Photo courtesy of Fakher Jamoussi).

For further information, please contact:

Prof. Fakher Jamoussi, TCG President

Centre National de Recherche en Sciences des Matériaux,

Technopôle de Borj Cédria

BP 273, 8020, Soliman

Tunisia

E-mail: tunisianclaygroup@yahoo.fr

February / 2014

The work is focused on sedimentation stability and aging of the aqueous suspension of Laponite in the presence of cetyltrimethylammonium bromide (CTAB). The concentration of Laponite was fixed at the level of Cl = 2 %wt, which corresponds to the threshold between equilibrium gel IG1 and repulsive gel IG2 phases. In the presence of CTAB, the Laponite aqueous suspensions were unstable against sedimentation; they separated into upper and bottom layers (U- and B-layers, respectively). The dynamic light scattering technique revealed that the addition of CTAB even in rather small concentration, Cs = 0.0164 %wt (0.03CEC), induced noticeable changes in the aging dynamics of U-layer; it was explained by equilibration of CTAB molecules that were initially non-uniformly distributed between different Laponite particles. Accelerated stability analysis by means of analytical centrifugation with rotor speed 500 − 4000 rpm revealed three sedimentation regimes: continuous (I, Cs < 0.14 %wt), zone-like (II, 0.14 < Cs < 0.2 %wt) and gel-like (III, Cs > 0.2 %wt). It was demonstrated that B-layer was ”soft” in the zone-like regime.

Two different methods (quantitative X-ray diffraction and fluorescent analysis) for analytical determination of cation exchange capacity (CEC) of montmorillonite in bentonite and artificial mixtures were compared. The impacts of impurities present in minerals and preliminary sonication on the estimated value of CEC were established. Also, the express technique for CEC determination was proposed.

The studies were focused on applications of the natural sorbents in the water treatment process, especially on kinetics of dye adsorption by the natural Saponite. Saponite deposits are spread on the territory of Ukraine. The Saponite layer thickness in Khmelnitsky region is of 10-40 m. The capacity of the most explored deposits of Tashkiv and Varvariv Saponite is about 60 million tons. The results of integrated research of natural and modified forms of Saponite showed that activation and modification of their surface can be used for changing the nature and concentration of superficial active centers. It provides possibility of creating attractive sorbents, catalysts, transmitters and fillers with the predictable properties. It was demonstrated that Saponite and Saponite-based composite materials can be effectively used for water treatment processes.

The work studies the adsorption of methylene blue dye by novel hybrid sorbent consisting of Laponite and multiwalled carbon nanotubes. The sorbent was obtained by sonication of aqueous suspensions of nanotubes at different concentrations of Laponite. The sonication resulted in formation of hybrid particles with a core-shell structure. The size and the shape of hybrid particles were determined by nanotubes, while their adsorption properties were determined by Laponite particles attached to the surface of nanotubes. The Laponite content in hybrid particles was corresponding to the Laponite to nanotubes ratio in the initial suspension XL = 0 – 1. The adsorbing capacity of the sorbent was much higher as compared to the adsorbing capacity of pure nanotubes, and it was directly proportional to the Laponite content in hybrid particles. This sorbent may be used either as a purifying additive or as a filtering layer if it is deposited on the surface of a supporting membrane. Due to relatively large size of hybrid particles, they may be easily separated from the purified solution by filtration or centrifugation.

It was shown that adding of a small amount (0.1 wt. %) of organomodified laponite (LapO) nanoplatelets resulted in drastic changes in dielectric and electro-optical characteristics of the suspensions of carbon nanotubes (CNTs) in nematic liquid crystal 5CB. Addition of LapO leads to the absence of classical percolation of conductivity and dielectric constant of 5CB-CNTs composites, as well as reduction of Frederiks threshold and significant growth of the contrast ratio of the 5CB-CNTs samples.

The reactivity of phenothiazine (PTZ) in PTZ–laponite mixtures, prepared by three different methods, was investigated using diffuse reflectance UV–visible absorption spectroscopy (DRUVv) at room temperature, T = 293 K. It was shown that formation of different charge separated states (CSS), depending on procedure of mixture preparation, could be observed in PTZ–laponite mixtures. PTZ_+ radical cations, adsorbed on the external surface of laponite, and PTZ2+ di-cations, intercalated inside the interlayer space, occurred in PTZ–laponite mixtures, based on laponite dehydrated under argon. In PTZ–laponite mixtures, based on hydrated laponite (dry-air state), the PTZ-species could be adsorbed only on the external surface of laponite in the form of PTZ_+ radical cations. It was also shown that if hydrated laponite powder is used, PTZ can penetrate with the help of a swelling agent (acetone) into the interlayer space and can be stabilized as a di-cation. The proposed schemes of spontaneous ionization of PTZ are in agreement with the data of wide angle X-ray diffraction analyses. The observed differences in formation of charge separated states in PTZ–laponite mixtures, prepared using different methods, reflect the effects of confinement on the structure and mobility of adsorbed and intercalated PTZ species

The studies on hybrid composites containing nematic liquid crystals carbon nanotubes and montmorillonite were continued. Comparative studies of different liquid crystal dispersions of rod-like carbon nanotubes (CNT) and plate-like exfoliated particles of organo-modified Laponite and montmorillonite (MMT) clays, were carried out.

Articles:

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  Loginov, M. et al. (2013), 'Electro-dewatering of drilling sludge with liming and electrode heating', Separation and Purification Technology 104, 89-99.
  
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  Loginov, M. et al. E. (2013), 'Determination of filtration properties of mineral suspensions from analytical centrifugation data', Filtration 13(1), 58-64.
  
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  Savenko, V.; Bulavin, L. et al. (2013), 'Sedimentation stability and aging of aqueous dispersions of Laponite in the presence of cetyltrimethylammonium bromide', Phys. Rev E 88, 052301 (arXiv:1305.6629).
  
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  Shaydyuk, E. et al. (2013), 'The photo-activity in phenothiazine-Laponite mixtures', Journal of Molecular Structure 1056-1057, 1-6.
  
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  Tomylko, S.; Yaroshchuk, O. Peculiarities of Liquid Crystal-Carbon Nanotube Dispersions Doped with a Small Amount of Nanoparticles of Synthetic Clay, et al. in Fesenko, O.; Yatsenko, L. & Brodin, M., ed., (2013), Nanomaterials Imaging Techniques, Surface Studies, and Applications, Springer-Verlag, New York Inc.
  

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  Sokol G.M., Ganzyuk A.Y. et al. The new modified sorbent for wastewater treatment // Abstracts of the XLVІ Session of the Students Scientific Circles, AGH University of Science and Technology, Cracow, Poland, 9-10 May, 2013. – P. 54 –55. ; Sokol G.M., Ganzyuk A.Y., Kamenskyh D.S. Saponite is an environmentally friendly universal sorbent // Abstracts of the Ninth International Scientific Congress “A secure world- understanding-trust-responsibility” organized by Societas Humboldtiana Polonorum, Poznan, Poland, 4-7 July, 2013 ; Ganzyuk A.Y., Sokol G.M. Universal sorbent on the basis of natural mineral saponite // Abstracts of the V Ukrainian-Рolish scientific dialogues, Jaremche, Ukraine, 16-19 October, 2013. – P. 118 – 120.
  
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  Loginov, M. et al.; (2013), Filtration/consolidation in analytical photo-centrifuge: A simple method for quantitative evaluation of filterability, in 'FILTECH 2013, Wiesbaden, Germany'.
  

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  Lisetski, L. et al., (2013), 'Liquid crystalline composite and method for its preparation'(Patent of Ukraine, N 102723).
  
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  Karvan S.A. et al. (2013), 'Paste based on natural mineral sorbents for cleaning of contaminated surfaces'.(Patent of Ukraine N79412, МПК (2006.01) С11D 3).
  
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  Loginov M. et al. (2013), Utilisation de nanotubes de carbone et d'argile minerale synthetique pour la purification d'eaux contaminees (Patent of France, N2.987.357).
  

The following institutes of the National Academy of Sciences of Ukraine were involved into the studies: Institute of BioColloid Chemistry, Institute of Physics, Instutite of Macromolecular Chemistry, Kiev National University of Technology & Design, Institute for Scintillation Materials of STC “Institute for Single Crystals”. The courses directly related with colloids and clay science are also presented in many Ukrainian universities, e.g. “Surface phenomena and disperse systems”, “Solid state chemistry”, and (Khmelnitsky National University), “Physical and colloidal chemistry” (Lviv National Medical University named Daniel Galician), “Surface phenomena” (Kherson State Technical University), “Physical and Colloid Chemistry” Lviv Polytechnica etc.

Photo 16: Kh. Ganzyuk (the second from the left) has participated in the International Sustainable World Energy Engineering Environment Project Olympiad, Houston, Texas, USA, May 8-13, 2013 She has obtained the silver Medal for the presented project “Universal sorbent on the basis of natural mineral saponite” (Photo courtesy of Nikolai Lebovka).