Mineralogy and Technical Properties of Clayey Diatomites from North and Central Greece

Cent. Eur. J. Geosci. • 1(4) • 2009 • 393-403 DOI: 10.2478/v10085-009-0034-3 Central European Journal of Geosciences Mineralogy and technical properties of clayey diatomites from north and central Greece Research Article Ioanna K. Ilia1∗, Michael G. Stamatakis2† , Theodora S. Perraki3‡ 1 National Technical University of Athens (NTUA), Faculty of Mining Engineering, Department of Geological Sciences, 157 80 Zographou, Athens, Greece 2 National & Kapodistrian University of Athens (NKUA), Department of Geology, Section of Economic Geology & Geochemistry, Panepistimiopolis 157 84 Ano Ilissia, Athens, Greece 3 National Technical University of Athens (NTUA), Faculty of Mining Engineering, Department of Geological Sciences, 157 80 Zographou, Athens, Greece Received 15 April 2009; accepted 11 September 2009 Abstract: Two bulk samples of clayey diatomite of Upper Miocene age originated from Western Macedonia, northern Greece and Thessaly central Greece were examined for their efficiency to be used as industrial absorbents. The samples were characterized using X-Ray Diffraction, Thermo-Gravimetric and Fourier Transform Spectroscopy, Scanning Electron Microscopy and ICP-MS analytical methods. The absorption capability of the clayey samples in oil and water were also examined. The mineralogy of both samples is predominated by the presence of clay minerals and amorphous silica. The clay minerals prevailed in the Klidi (KL) bulk sample, with muscovite being the dominant phase, and kaolinite and chlorite occurring in minor amounts. In the Drimos (DR) bulk sample, vermiculite was the predominant clay phase. Smectite was not found in either sample, whereas detrital quartz and feldspars were present in significant amounts. The amorphous silica phase (opal-A) occurs mainly with the form of disck-shaped diatom frustules. The chemistry of the samples is characterized by the predominance of silica, alumina, and iron, whereas all the other major and the trace elements are in low concentrations. Both clayey diatomite rocks exhibited sufficiently good oil and water absorption capacity, ranging between 70 to 79% in the clay-rich sample KL and 64 to 70% in the opal-A-rich sample DR. Comparing the properties of the rocks studied with other commercial absorbents, it is concluded that they may find applications as absorbents in industrial uses. Keywords: diatomite • absorption • clays • vermiculite • kaolinite • TG/DTG • XRD • FT-IR © Versita Warsaw 1. Introduction ∗E-mail: [email protected] † E-mail: [email protected] ‡ E-mail: [email protected] Generally speaking, the amorphous silica of biogenic ori- gin is found in nature in the form of siliceous microfossils such as diatom frustules, radiolarian cells, silicoflagel- 393 Mineralogy and technical properties of clayey diatomites from north and central Greece late skeletons and sponge spicules, which are commonly estimated reserves are more than 5 000 000 m3 each. characterised as diatomite rock or diatomaceous earth [1]. Diatomite is a chalk-like, soft, friable, earthy, very fine- grained, siliceous sedimentary rock, usually light in colour (white if pure, commonly buff to grey in situ, and rarely black) with low thermal conductivity and a rather high fusion point. Besides the amorphous silica (opal-A), diatomite rocks may also contain clay and carbonate minerals, quartz, feldspars and volcanic glass. Most of the silica content of the diatomaceous rocks is reactive, being amorphous, and hence these rocks are characterised as raw materials with significant pozzolanic properties, ap- propriate in cement additive applications [1, 2]. Worldwide statistics on the usage of diatomite are generally unavailable. Some 1993 estimates however, suggest that the absorption applications represent 11% [3]. For more than 50 years, diatomite of lower purity has been used to absorb liquid spills. Both granules and powders of various grades are manufactured and may be calcined to increase hardness, improve durability after absorbing a fluid and reduce the tendency to produce dust [4]. Clayey diatomite is currently used principally as ad- Figure 1. Map of Greece showing the studied locations of the Klidi sorption and insulation materials, while carbonaceous di- and Drimos areas. atomite is used mainly for the production of Clinker and the neutralization of acid-water drainage [5–7]. The basins are of Upper Miocene through Pliocene age Diatomite deposits of commercial grade have been located and are developed above metamorphic rocks and ophio- in marine and lacustrine deposits of Miocene and Pliocene lites belonging to the Pelagonian Geotectonic Zone. Even age worldwide [8]. Although several diatomite deposits are though the Florina Basin hosts significant Upper Miocene located in Greece, their usage as adsorption materials has lignite deposits, the Elasson-Sarantaporo Basin hosts not been established thus far [9]. Two diatomite beds of only insignificant lignite seams of the same age [11–19]. a total 3 m thick occurring as intercalations in tuffaceous The diatomaceous beds are mostly homogenous and occur rock of Milos Island, Aegean Sea, Greece, are co-extracted as overburden of the lignite layers in both basins. Rare with the tuffs and used as a cement additive by the Greek siltstone and sandstone beds are interbedded to the di- cement company TITAN S.A. The aim of the present study atomaceous rocks. Fe-Ca phosphates such as anapaite is therefore to examine the mineralogical composition and and mitridatite (surface samples) and Fe-phosphates such the absorption capacity of the raw materials originating as vivianite (borehole samples) occur in both basins in the from the Florina Basin (Amynteo area) and the Drimos- form of organic material replacements [20, 21]. Sarantaporo Basin (Elasson area), in order to characterize them as industrial absorbents. 3. Materials and methods 2. Geological settings Two bulk samples of 100 kg each were collected from the Klidi-Florina (KL) and the Drimos Sarantaporo (DR) di- The Klidi area is part of a broader Neogene Basin in NW atomaceous rocks, which represent a total thickness of Macedonia (Greece). The basin extends from Monastiri 20 m of the clayey rocks. The samples were very fine- (F.Y.R.O.M), in a NNW-SSE direction, up to the hills of grained and homogenous, having bluish and yellowish Kozani through the cities of Florina, Amynteo and Ptole- color respectively. The KL sample was extracted from mais. The specific basin is almost 100 km long and 15 - the Klidi lignite mine, located SW of Amynteo village, 20 km wide [10]. The Drimos-Sarantaporo Basin is of whereas the DR sample was extracted from a technical the same age and extends to the South of the aforemen- outcrop NE of Elasson village. tioned basin (Figure 1). Based on field measurements of The mineralogical composition of the collected samples several natural and artificial outcrops of both basins, the was determined by X-Ray Diffraction (XRD), Thermo- 394 Ioanna K. Ilia, Michael G. Stamatakis, Theodora S. Perraki Gravimetric (TG/DTG) and Differential Thermal Analysis 4. Results and discussion (DTA), Fourier Transform (FT-IR) spectroscopy and Scan- ning Electron Microscopy analysis (SEM). 4.1. Mineralogy of the Klidi-Florina region The X-Ray power diffraction patterns were obtained using 4.1.1. X-Ray Diffraction (XRD) analysis a Siemens D-5000 diffractometer, with Ni-filtered CuKa1 The clay minerals prevailed in the sample, with muscovite radiation (G = 1.5405 Å), operating at 40 kV, 30 mA. For X- being the dominant phase, followed by kaolinite and chlo- Ray Diffraction (XRD) analyses, samples were prepared rite (Figure 2). Smectite was not found in the sample. as non-oriented and oriented mounts. The latter, which Quartz was identified, feldspars and opal-A. Minor contri- < consisted of 53 μm material in order to avoid most of bution of carbonates (dolomite) were also present (< 10%). the detrital minerals, was firstly separated by centrifuging and then placed on a glass slide as a thin layer and al- lowed to dry at room temperature. Clay fractions were an- alyzed after glycolation and after heating to 500°C, 850°C, and 1 100°C in order to identify the various clay mineral phases. The IR measurements were carried out using a Fourier Transform IR (FT-IR) spectrophotometer (Perkin Elmer 880). The FT-IR spectra, in the wave number range from 400 cm−1 to 4 000 cm−1, were obtained using the KBr pellet technique. The pellets were prepared by pressing a mixture of the sample and of dried KBr (sample: KBr approximately 1:200), at 8 tons cm−2. Figure 2. XRD diagram of a representative diatomite sample from The Thermo-Gravimetric (TG/DTG) analysis was obtained Klidi-Florina. Mu:Muscovite, Ka:Kaolinite, Chl:Chlorite, simultaneously using a Mettler Toledo 851 instrument. Qz:Quartz, Fd:Feldspars, Do:Dolomite. Opal-A is repre- The samples were heated from 20°C to 1 200°C at a con- sented by the hump occurring between 20-28 degrees. stant rate of 10°C min−1. A Jeol-JSM-5600 SEM-EDS type of Scanning Electron Microscope was used in order to examine the minute struc- ture of the biogenic silica, mostly diatom frustules, con- tained in the bulk samples. Chemical analyses of the samples were carried out in ALS Chemex Laboratories at Saskatchewan, Canada. The major oxides were determined by lithium meta or tetra bo- rate fusion and ICP-AES, while trace elements were anal- ysed by HF-HNO3-HClO4 acid digestion, HCl leach and a combination of ICP-MS and ICP-AES. Figure 3. XRD diagram of a representative diatomite sample from Oil and Water Adsorption were carried out following the Klidi-Florina. a) “as it is” b) after heating up to 500°C. British Standard method (BS-3483: part B7) for testing pigments for paints and the procedures used by the BGS, UK [22] and by LITHOS Laboratory (I.G.M.E. Athens). Quartz was identified by its typical peaks (101) at d_spac- 2 kg of the bulk samples were prepared using the quar- ing=3.34 Å and (100) at d-spacing=4.26 Å, while feldspars tering method.

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