Mustafa ÇINAR, Mehmet Sabri ÇELİK

Yüksek viskoziteli endüstriyel uygulamalarda sepiyolitin öğütme mekanizması

Bu çalışmada yaş ve kuru olarak uygulanan farklı öğütme tekniklerinin sepiyolit liflerini serbestleştirmedeki etkinliği boyut kontrolü ile birlikte araştırılmıştır. Katı konsantrasyonu, karıştırmanın şiddeti-süresi ve öğütme şeklinin sepiyolitin reolojik özellikleri üzerinde önemli etkisinin olduğu görülmüştür. Kuru öğütme işlemlerinin öğütme süresindeki artışla beraber sepiyolitin yapısına zarar verdiği ve 2 saatlik öğütme süresinden sonra tekrar floklaşmadan dolayı tane boyutunun irileştiği ve lifsi yapısının kaybolduğu, yerini şekilsiz kürelerin aldığı görülmüştür. Yaş öğütmede ise sepiyolitin lifsi yapısının korunduğu tespit edilmiştir. Elde edilen verilerin değerlendirilmesinde zeta potansiyel, yüzey alanı ve SEM (taramalı elektro mikroskop) görüntülerinden faydalanılmıştır.

Grinding mechanism of sepiolite for high viscosity industrial applications

Clay minerals have a wide range of industrial applications including thickeners and flow regulators which are known as rheological additives. For this purpose, bentonite type layered smectite group clays and needle structured sepiolite and attapulgite type clays are used. The mechanisms of gelling for both clays are different due to their unique structures. The rheological properties of these suspensions depend on such parameters as concentration, the intensity of agitation and pH. These properties make sepiolite suspensions very useful thixotropic materials and thickeners. In this study, the effect of mode of grinding, dry and wet on disintegration of sepiolite fibers was investigated under controlled particle size. Physical parameters are shown to impart a pronounced effect on the viscosity of sepiolite; the viscosity increases with increasing the energy of agitation, but increase in viscosity against solids concentration is not linear but polynomial. The results were interpreted with zeta potential, surface area measurements and SEM photographs. It is shown that the mode of grinding has a significant effect on the rheological properties of sepiolite. Dry grinding process adversely affects the structure of sepiolite and after 2 hours of grinding, the grain size is enlarged due to agglomeration of fibers into spheres. In wet grinding, the fiber structure of sepiolite was preserved along with a plausible size reduction. These results were also corroborated with zeta potential results.

PDF

___

Aglietti, E.F., Porto Lopez, J.M. ve Pereira, E., (1986a). Mecanochemical effects in kaolinite grinding, I. Textural and physicochemical aspects, International Journal of Mineral Process, 16, 125-133.
Aglietti, E.F., Porto Lopez, J.M. ve Pereira, E., (1986b). Mecanochemical effects in kaolinite grinding, II. Textural and physicochemical aspects, International Journal of Mineral Process, 16, 135-146.
Blahoslov, C. ve Kranz, G., (1981). Mechanism of montmorillonite structure degradation by precussive grinding, Clay Minerals, 16, 151-162.
Cornejo, J. ve Hermosin, M.C., (1988). Structural alteration of sepiolite by dry grinding, Clay Minerals, 16, 151-162.
Dellisanti , F. ve Valdre, G., (2005). Study of structural properties of ion treated and mechanically deformed commercial bentonite, Applied Clay Science, 28, 233-244.
Henmi, T. ve Yoshinaga, N., (1981). Alteration of imogolite by dry grinding, Clay Minerals, 16, 139-149.
Hlavay, J., Jonas, K., Elek, S. ve Inczedy, J., (1977). Characterisation of the particle size and the crystallinity of certain minerals by infra red spectrophotometry and other instrumental methods, I. Investigations on clay minerals, Clays Clay Minerals, 25, 451-456.
Juhasz, A.Z. ve Opoczky, L., (1990). Mechanical activation of minerals by grinding, Martin V.E., Garciaes A., Martin A. et al., eds., 234-240 Pulverising and morphology of particles, Aked Kiado, Budapest.
Keller, W.D., (1955). Oxidation of montmorillonite during laboratory grinding, American Mineralogist, 40, 348.
Keren, R., 1991. Adsorbed sodium fraction’s effect on rheology of montmorillonite-kaolinite suspensions, Soil Science Society of America Journal, 55, 376-379.
Lagaly G., (1989). Principles of flow of kaolinite and bentonite dispersions, Applied Clay Science, 4, 105-123.
Lagaly, G., (1993). Coagulation and Flocculation, Chapter I, Eds. Dobias, B., Marcel Dekker, New York.
Mingelgrin, V., Kliger, L., Gal, M. ve Saltzman, S., (1978). The effect of grinding on the structure and behaviour on bentonites, Clays Clay Minerals., 26, 299-307.
Papirer, E. ve Roland, P., (1981). Grinding of chrysotile in hydrocarbons, alcohol and water, Clays Clay Minerals, 29, 161-170.
Perez-Rodriguez, J.L., Sanchez Del Villar, L.M. ve Sanchez-Soto, P.J., (1988). Effects of dry grinding on pyrophyllite, Clay Minerals, 23, 399- 410.
Perkins, A.T. ve Dragsdorf, R.D., 1952. Decomposition of bentonite as affected by H, Ca, Mg and dry grinding, Soil Science Society of America Process., 16, 312-316.
Permien, T. ve Lagaly G., (1994). The rheological and colloidal properties of bentonite dispersionsin the presence of organic compounds: I. Flow behaviour of sodium-bentonite in water-alcohol, Clay Minerals, 29, 751-760.
Santaren, J., 1993. Sepiolite: a mineral thickener and rheology additive, Modern Paint and Coatings, 98-72.
Schrader, R., Kutzer, H.Y. and Hofman, B., 1970. Uber die mechanische Aktivierung von Kaolinit, Tonind, Chemiker-Zeitung., 94, 410.
Shaw, B.T., (1942). The nature of colloidal clay as revealed by the electron mikroscope, The Journal of Physical Chemistry, 46, 1032-1043.
Simonton, T.C., Komarneni, S. ve Roy, R., (1988). Gelling properties of sepiolite versus montmorillonite, Applied Clay Science, 3, 165- 176.
Sondi, I., Stubicar, M., ve Pravdic, V., (1997). Surface properties of ripidolite and beidellite clays modified by high-energy ball milling, Colloids and Surfaces, 127, 141-1149.
Suraj, G., Iyer, C.S.P., Rugmini, S. ve Lalithambika, M., (1997). The effect of micronization on kaolinites and their sorption behaviour, Applied Clay Science, 12, 111-130.
Suquet H., (1989). Effects of dry grinding and leaching on the crystal structure of chrysotile, Clays Clay Minerals, 37, 439-445.
Vucelic, D., Simic, D., Kovacevic, O., Dojcinovic, M. ve Mitrovic, M., (2002). The effects of grinding on the physicochemical characteristics of white sepiolite from Golesh, Journal of the Serbian. Chemical Society, 67, 197-211.
Wiewiora, A., Sanchez-Soto, P.J., Aviles, M.A., Justo, A. ve Perez-Rodriguez, J.L., 1993. Effect of dry grinding and leaching of polytypic structure of pyrophyllite, Applied Clay Science, 8, 261-282.