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 origin 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 analyzed 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 structure of the biogenic silica, mostly diatom frustules, contained 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. Oil absorption was determined through were identified by the peaks (002) at d-spacing=∼3.19 Å the addition of linseed oil (specific gravity of 0.95) by bu- and (220) at d-spacing=∼3.24 Å. The broad hump reg- rette drops to 100 g of sample, followed by rubbing with istered between 20 and 26 2S, indicated the presence of a palette knife, till a paste of smooth consistency was opal A. Dolomite was identified by its typical peak (100) at formed. d-spacing=∼2.8 Å. In addition, muscovite was identified

395 Mineralogy and technical properties of clayey diatomites from north and central Greece

by the sharp diffraction peak (001) at d-spacing=∼10 Å and (003) at d-spacing=∼3.34 Å. Kaolinite was identified Table 1. Mineralogical composition of the studied samples from by its typical (001) and (002) peaks at ∼7.1 Å and d- Florina region, before and after being heated at various temperatures. spacing=∼3.5 Å, and chlorite by (001) and (002) peaks at d-spacing=∼14 Å and d-spacing=∼7 Å, respectively. In “KL” Qtz Op Fld Dol Ka Mu Chl an orientated sample (Figure 2) the overlap of the kaoli- as it is MD MD MD TR MJ MJ MD nite and chlorite peak (d_spacing=∼7.1 Å) is shown. In after heated MD MD MD TR TR MJ MJ order to identify these two minerals (kaolinite and chlo- at 500°C rite), the thermal behavior of the samples was examined after heated MJ MJ MD – – MD – (Figure 3). at 850°C The samples were heated up to 500°C for 2 hours, in after heated MJ MJ MD – – – – a static oven, and cooled down at room temperature at 1 100°C and examined by x-ray power diffraction. A decrease in Qtz:Quartz, Op:opal-A (poorly crystallised opal-CT at the intensity of the characteristic diffraction peaks at d- 1 100°C), Fld:Feldspars, Dol:Dolomite, Ka:Kaolinite, spacing=∼7.1 Å and d-spacing=∼3.52 Å, due to the col- Mu:Muscovite, Chl:Chlorite lapse of kaolinite as shown in Figure 3, clearly indicates the presence of kaolinite. No smectite was found in the groups”, lying between the tetrahedral and the oc- studied samples, as its typical peak (100) should be shifted tahedral sheets [24]. from d-spacing=∼14 Å to (d-spacing=∼17 Å) lower 2S after saturation with ethylene glycol (Figure 4). • The broad band, near 3 436 cm−1, is due to H-O-H vibration of absorbed water.

• The band at ∼1 632 cm−1 is due to OH bending vibrations of adsorbed water in phylosilicate min-

erals as well as the H2O of opal-A.

•The∼1 093 cm−1 band is attributed to the stretching vibration of Si-Oapical and the ∼1 039 cm−1 band arises from the Si-O-Si vibration.

•The∼792 cm−1 band occurs because of the OH translational vibration [24, 25].

• The bands at around ∼649, ∼529 cm−1 originate Figure 4. XRD diagram of a representative diatomite sample from from Si-O-AlVI vibrations (Al in octahedral co- Florina. a) “as it is” b) after saturation with ethylene ordination), while the band at around 468 cm−1 is glycol. attributed to the Si-O-Si bending vibrations [24, 26]. The mineralogical composition of the examined samples from Klidi-Florina region which was identified after being From the above mentioned results it is clear that the FT- heated up to 1 100°C is shown in Table 1. IR spectra confirm the presence of muscovite, kaolinite and chlorite in all the studied samples from Florina. 4.1.3. TG and DTG analysis 4.1.2. Fourier Transform Infrared Specrtoscopy (FT-IR) The results of the thermal study of the samples examined From the derived FT-IR spectra of representative samples after heating up to 1 200°C, at a rate of 10° min−1 confirm (Figure 5) from Florina, the following results are inferred: the presence of muscovite, kaolinite, and chlorite. From •The∼3 694 cm−1 strong band arises from the in- the TG and DTG curves of a representative sample (Fig- phase symmetric stretching vibration of the OH ure 6), we conclude that: groups, either outer or inner surface OH of the oc- • In the temperature range from 25°C to 100°C, the tahedral sheets, which form weak hydrogen bonds weight loss due to absorbed water is 2.66%. with the oxygens of the next tetrahedral layer [23]. On the other hand, the ∼3 612 cm−1 strong band • The crystalline water contained in the opal-A is is due to the stretching vibrations of the “inner OH lost at about 120 degrees [27].

396 Ioanna K. Ilia, Michael G. Stamatakis, Theodora S. Perraki

4.2. Mineralogy of Drimos-Sarantaporo region 4.2.1. X-Ray Diﬀraction (XRD) analysis In the bulk sample of this area, clay minerals prevailed as in the Florina sample, but vermiculite was present in- stead of chlorite. Opal-A is the dominant phase, followed by muscovite, kaolinite and vermiculite (Table 2 and Fig- ure 7). Detrital minerals such as quartz and feldspars were also reported. Carbonate minerals were not detected.

Figure 5. FTIR spectrum of a representative diatomite sample from Klidi-Florina.

• In the temperature range from 400°C to 500°C, the rapid weight loss (4.32) is documented by the steep slope of the TG curve and a characteristic peak on the DTG curve, which extends up to the temperature of ∼600°C. This is attributed to the dehydroxylation of the kaolinite, (due to the loss of OH Figure 7. XRD diagram a representative diatomite sample VI from Drimos-Sarantaporo. Mu:Muscovite, Ka:Kaolinite, groups, surrounding the Al atoms) and the pro- Ve:Vermiculite, Qz:Quartz, Fd:Feldspars. Opal-A is re- gressive transformation from the octahedral coordi- ported as the hump located between 20-28 degrees. nated Al, in kaolinite, to a tetrahedral coordinated form, in metakaolinite, through the breaking of OH The discrimination among vermiculite, chlorite and smec- bonds [20]. tite, was succeeded by the study of the thermal behavior of the samples, as well as their behavior after saturation • The at ∼780°C and ∼1 000°C peaks on the DTG with ethylene glycol (Figure 8 and Figure 9). The samples curve correspond to chlorite and muscovite respec- were heated up to 500°C for 2 hours, in a static oven (Fig- tively. ure 8). Samples were then cooled at room temperature and examined by x-ray power diﬀraction. The absence of the typical peak at d-spacing=∼14 Å, in combination with its shifting from d-spacing=∼14 Å to d-spacing=∼16.3 Å of the glycolated sample, indicated the absence of chlorite and smectite and the presence of vermiculite [28] (Fig- ure 9). 4.2.2. Fourier Transform Infrared Spectroscopy (FT-IR) From the derived FT-IR spectra of representative samples (Figure 10) from Drimos area, we inferred the following results:

•The∼3 694 cm−1 strong band arises from the in- phase symmetric stretching vibration of the OH groups, either outer or inner surface OH of the octahedral sheets, which form weak hydrogen bonds Figure 6. Typical TG curve of a representative diatomite sample from Florina. Mu:Muscovite, Ka:Kaolinite, Chl:Chlorite. with the oxygens of the next tetrahedral layer [23]. On the other hand, the ∼3 616 cm−1 strong band is due to the stretching vibrations of the “inner OH

397 Mineralogy and technical properties of clayey diatomites from north and central Greece

From all the above mentioned results it is clear that the FT-IR spectra conﬁrm the presence of muscovite, kaolinite and vermiculite in all the studied samples from Drimos- Sarantaporo.

Table 2. Mineralogical composition of the studied samples from Drimos-Sarantaporo region, before and after being heated at various temperatures.

“DR” Qtz Op Fld Il-Mu Ka Chl Ve Cr Ens as it is MD MD MD MJ MD TR MD – – Figure 8. XRD diagram of a representative diatomite sample from after heated Drimos-Sarantaporo. a) “as it is”, b) after heating up to MD MD MD – – – – – – 500°C. at 500°C after heated MD MD MD – – – – – TR at 850°C after heated MJ MJ MD – – – – TR – at 1 100°C Qtz:Quartz, Op:opal-A (poorly crystallised opal-CT at 1 100°C), Fld:Feldspars, Il-Mu:Illite-Muscovite, Ka:Kaolinite, Chl:Chlorite, Ve:Vermiculite, Cr:Cristobalite, Ens:Enstatite

The mineralogical composition of the Drimos-Sarantaporo samples heated at 500, 850 and 1 100°C is shown in Ta- ble 2.

Figure 9. XRD diagram of a representative diatomite sample from Drimos-Sarantaporo. a) “as it is” b) after saturation with ethylene glycol.

groups”, lying between the tetrahedral and the octahedral sheets [24].

• The broad band, near 3 435 cm−1, is due to H-O-H vibration of absorbed water.

• The band at ∼1 637 cm−1 is due to OH bending vibrations of adsorbed water in sheetsilicate minerals

as well as the H2O of opal-A.

• The 1 093 cm−1 band is attributed to the stretching Figure 10. FTIR spectrum of a representative diatomite sample −1 vibration of Si-Oapical and the 1 040 cm band from Drimos-Sarantaporo. arises from the Si-O-Si vibration.

•The∼792 cm−1 band occurs because of the OH 4.2.3. TG and DTG analysis translational vibration [24, 25]. The results of the thermal study of the examined samples • The band at around 529 cm−1 originates from Si-O- after being heating up to 1 200°C, at a rate of 10°C min−1 AlVI vibration (Al in octahedral co-ordination), while conﬁrm the presence of kaolinite, muscovite and vermi- the band at around 470 cm−1 is attributed to the culite. From the TG and DTG curves of a representative Si-O-Si bending vibrations [24, 26]. sample (Figure 11), we conclude that:

398 Ioanna K. Ilia, Michael G. Stamatakis, Theodora S. Perraki

• In the temperature range from 25°C to 100°C, the silica diagenesis was not promoted within the speciﬁc de- weight loss due to absorbed water is 2.32%. posits, probably due to low permeability of the clayey diatomite. • The second dehydration step observed in the temperature range 100-300°C, corresponds to the re- lease of water molecules, which were in the in- terlayer space of vermiculite [29]. Opal-A looses the crystalline water at the same range of temperatures [27].

• In the temperature range from 400°C to 600°C, the rapid weight loss (2.26%) is documented by the steep slope of the TG curve, as well as the characteristic peak on the DTG curve. This is attributed to the dehydroxylation of the kaolinite, (due to the Figure 12. Disc-shaped diatom frustules (cyclotella sp.) sunk in a loss of OH groups, surrounding the AlVI atoms) and clayey Matrix, bulk sample DR of Drimos-Sarantaporo area. the progressive transformation from the octahedral coordinated Al, in kaolinite, to a tetrahedral coordinated form, in metakaolinite, through the breaking of OH bonds [26]. The dehydroxylation of the vermiculite is observed in the same temperature range. It is important to mention that chlorite and montmorillonite give peaks at higher temperatures.

Figure 13. Well presented diatom frustules surrounded by detrital crystals, bulk sample KL of Klidi-Florina area.

4.4. Chemical analysis

The chemical analysis of the bulk samples is shown in Ta- bles 3 and 4. Two grain-size fractions of both bulk samples were studied, one of less than 0.3 mm and another of 0.3- 1.7 mm. The former was very ﬁne in size, and is commonly Figure 11. Typical TG curve of a representative diatomite sample from Drimos-Sarantaporo. Ka:Kaolinite, Ve:Vermiculite a waste or recycled material, whereas the latter is commonly used for absorption applications in industrial scale. Silica, alumina and iron oxide were the main constituents

of the samples. The SiO2 content corresponded to sil- 4.3. Scanning Electron Microscope analysis ica polymorphs (quartz and opal-A) and aluminosilicate (SEM) minerals, while Fe2O3 to the amounts of chlorite and vermiculite present in Klidi-Florina and Drimos-Sarantaporo The SEM study of the diatomaceous rocks indicated that samples respectively. the diatom frustules were mostly well preserved, having The trace element content of both samples was typical disk or oblong shape and ranged in size from 5 to 30 μm for clayey rocks and there was no heavy or base metal (Figure 12, Figure 13). The predominant shape of the di- enrichment. The concentration of Cu and Zn were higher atoms in the DR clayey diatomite were that of disk shapes in the ﬁne grained fractions (< 0.3 mm) which were richer belonging to Cyclotella sp., while in KL clayey diatomite in clay minerals. These enrichments could be attributed could be observed also as oblong frustules. Most diatom to the ability of clay fractions to absorb various metals frustules retained their minute structure, indicating that (Figure 14).

399 Mineralogy and technical properties of clayey diatomites from north and central Greece

Table 3. ICP-MS chemical analysis of the clayey diatomite rock Table 4. Trace element content of ﬁne-grained fractions of less than samples of Florina KL and Drimos-Sarantaporo regions 0.3 mm and 0.3-1.7 mm, from bulk samples of Florina in grain fractions of less than 0.3 mm and 0.3-1.7 mm KL and Drimos-Sarantaporo DR regions, analyzed by ICP- respectively. MS.

% KL-0.3 KL-0.3-1.7 DR-0.3 DR-0.3-1.7 ppm DR-0.3 DR-0.3-1.7 KL-0.3 KL-0.3-1.7

SiO2 64.70 64.10 65.20 65.70 Ag 0.1 0.1 0.3 0.2

Al2O3 13.55 12.90 16.60 16.60 As 2.6 2.8 11.3 10.2

Fe2O3 10.90 12.20 6.33 6.74 Ba 580 650 390 380 CaO 2.51 2.30 1.92 1.69 Be 3.4 3.5 3.0 3.0 MgO 1.86 1.80 1.92 2.02 Bi 0.5 0.6 0.5 0.4

Na2O 1.47 1.22 1.52 1.24 Cd 0.2 0.3 0.6 0.6

K2O 1.92 1.83 2.57 2.57 Ce 75.6 80.1 58.4 54.1

TiO2 0.65 0.60 0.87 0.82 Co 16.7 24.7 30.5 28.5 MnO 0.20 0.24 0.11 0.21 Cr 59 61 106 111

P2O5 0.37 0.62 0.13 0.17 Cs 4.9 5.5 5.4 5.5

SO3 0.02 0.02 0.65 0.63 Cu 412 45.4 306 56.2 LOI 2.26 2.25 2.71 2.10 Ga 24.5 26.1 20.8 19.4 Total 100.41 100.08 100.53 100.49 Ge 0.2 0.3 0.2 0.2 Hf 0.5 0.5 0.8 0.7 ln 0.1 0.1 0.1 0.1 La 37.3 39.6 29.9 27.3 Li 38.5 42.5 30.6 29.5 Mo 1.2 1.5 1.1 1.1 Nb 14.4 14.5 13.5 12 Ni 38.3 46.7 83.6 83.6 Pb 20.2 26.8 26.0 23.1 Rb 125 141 122 116 Sb 0.3 0.3 0.6 0.5 Sc 17.1 17.6 12.7 11.5 Se 2.0 2.0 2.0 2.0 Sn 3.0 3.1 2.5 2.3 Sr 181 166 162 129 Ta 1.1 1.1 1.0 0.9 Figure 14. Water and Oil absorption of KL and DR dried and Te 0.1 0.1 0.2 0.1 heated bulk samples showing the stabilization or the decrease in adsorption capability of heated samples. Th 13.4 14.6 13.5 12.7 Tl 0.8 0.9 1.1 1.0 U 3.3 3.7 3.8 3.7 4.5. Oil and water absorption V 113 119 124 130 W 6.1 6.8 3.6 3.9 The oil and water absorption test was carried out in the Y 30.7 31.5 25.3 23.5 fine grained fractions (< 0.3 mm) of the examined samples Zn 147 115 156 132 and resulted in good absorption capacity of both KL and Zr 15.1 15.4 26.6 23.8 DR bulk samples (Figure 14). Tests were performed in a raw state and also on heated samples at temperatures of 400°C, 670°C and 800°C. Sintering of both materials Drimos-Sarantaporo areas. The above mentioned stabi- occurred at about 1 100°C. lization presented in both oil and water treatment is at- In detail, there seemed to be an increase in the absorp- tributed to the early and partial vitrification of the ma- tion capability in the heated materials compared with the terial. In all temperatures and grain-size fractions, the raw ones. From the diagram in Figure 14, it is clear Florina samples in which clay minerals predominate, have that the absorption capacity is either stabilized, or de- slightly better absorption capacity than that of Saranta- creased in the range of temperatures between 670°C and poro, in which opal-A predominates. It could be concluded 800°C for the examined samples of both Klidi-Florina and that the specific clay minerals mixture of the studied ar-

400 Ioanna K. Ilia, Michael G. Stamatakis, Theodora S. Perraki

eas have higher absorption capacity than the biogenic due tules. In addition, quartz and feldspars of detrital to (probably particle size distribution, grain size, shape, origin are significant components of the sample. In crystal/mineral structure). the Drimos-Sarantaporo sample, muscovite is the The oil and water absorption capacity of the samples stud- predominant clay mineral phase, whereas kaolin- ied were compared to that of already examined materials ite and vermiculite are also significant clay min- (Figure 15). As far as the oil absorption capacity was eral phases. Minerals of the montmorillonite group concerned, both the KL and the DR samples showed com- were not identified. Opal-A is also represented by parable values to that of diatomite and bentonite ‘’Jor- diatom frustules, and the detrital minerals phases dan” whereas they had higher absorption capacity than by quartz and feldspars. the specific kaolinite and lower than the palygorskite-rich samples of Greece (Figure 15). The water absorption ca- • The diatom frustules idnetified in the bulk samples pacity of the samples studied showed higher values than of both areas constitute a significant portion of the kaolinite and lower values than that of bentonite and pa- clayey rock and hence, play an important role in lygorskite (Figure 15). the absorption capability of the samples studied. • The measurement of Oil and Water Absorption capacity of the studied samples, range from 70 to 79% and 64 to 70% for Florina and Drimos-Sarantaporo samples respectively. The dominance of clay minerals in the Florina sample compared with that of the Drimos-Sarantaporo sample could be related to the higher absorption capacity of the Florina sample, indicating that the clay minerals of the studied samples have higher absorption capacity than that of the diatom frustules that dominate in the Drimos- Sarantaporo sample.

• The given measurements indicate that the examined clayey diatomite bulk samples are appropri- ate for use as absorption materials in an industrial scale. As presented from literature data [33], currently used industrial absorbents have an efficiency to absorb up to 60-70% of their weight in liquid, Figure 15. Diagram of oil and water absorption in materials from hence the samples studied are capable for such ap- the studied areas and other regions [30–32]. plications. In addition, taking into account that the total market for industrial spillage absorbents in Europe is around 120 000 to 150 000 tpa, with diatomite being the biggest volume absorbent [33], the 5. Conclusions tested clayey diatomite have significant industrial potential. The evaluation of raw and thermally treated clayey diatomite bulk samples from northwest and central Greece, by means of XRD, TG/DTG, FTIR spectroscopy, and SEM; Acknowledgments as well as Oil and Water absorption capability, concluded that: Thanks are expressed to Ms. Chalikiopoulou Fotini, geol- ogist and to Mr. Athanasio Tselo, technician, of LITHOS • The mineralogy of Florina and Drimos-Sarantaporo Laboratory of I.G.M.E., Athens, for their valuable technical clayey diatomite bulk samples is dominated by the support during the implementation of the laboratory test presence of clay minerals and opal-A of biogenic on absorption capacity of the studied samples. We also origin. Concerning the clay minerals, muscovite thank Mr. Evangelos Michailidis, Geology and Geoenvi- is the dominant phase in Florina sample, followed ronment Department, NKUA, for his assistance during the by kaolinite and chlorite. Minerals of the mont- SEM analysis. morillonite group were not identified. Opal-A is mostly represented by well preserved diatom frus-

401 Mineralogy and technical properties of clayey diatomites from north and central Greece

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