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Cent. Eur. J. Geosci.DOI: 10.2478/v10085-009-0034-3

Central European Journal of Geosciences

Mineralogy and technical properties of clayeydiatomites 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, Panepistimiopolis157 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, northernGreece and Thessaly central Greece were examined for their efficiency to be used as industrial absorbents. Thesamples 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 samplesin oil and water were also examined. The mineralogy of both samples is predominated by the presence of clayminerals and amorphous silica. The clay minerals prevailed in the Klidi (KL) bulk sample, with muscovite beingthe 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 quartzand feldspars were present in significant amounts. The amorphous silica phase (opal-A) occurs mainly withthe form of disck-shaped diatom frustules. The chemistry of the samples is characterized by the predominanceof silica, alumina, and iron, whereas all the other major and the trace elements are in low concentrations. Bothclayey diatomite rocks exhibited sufficiently good oil and water absorption capacity, ranging between 70 to79% in the clay-rich sample KL and 64 to 70% in the opal-A-rich sample DR. Comparing the properties of therocks studied with other commercial absorbents, it is concluded that they may find applications as absorbentsin industrial uses.

Keywords: diatomite • absorption • clays • vermiculite • kaolinite • TG/DTG • XRD • FT-IR

© Versita Warsaw

∗E-mail: [email protected]†E-mail: [email protected]‡E-mail: [email protected]

1. Introduction

Generally speaking, the amorphous silica of biogenic ori-gin is found in nature in the form of siliceous microfossilssuch as diatom frustules, radiolarian cells, silicoflagel-

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

late skeletons and sponge spicules, which are commonlycharacterised 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 rarelyblack) with low thermal conductivity and a rather highfusion point. Besides the amorphous silica (opal-A), di-atomite rocks may also contain clay and carbonate min-erals, quartz, feldspars and volcanic glass. Most of thesilica content of the diatomaceous rocks is reactive, beingamorphous, and hence these rocks are characterised asraw materials with significant pozzolanic properties, ap-propriate in cement additive applications [1, 2].Worldwide statistics on the usage of diatomite are gener-ally unavailable. Some 1993 estimates however, suggestthat the absorption applications represent 11% [3]. Formore than 50 years, diatomite of lower purity has beenused to absorb liquid spills. Both granules and powdersof various grades are manufactured and may be calcinedto increase hardness, improve durability after absorbing afluid and reduce the tendency to produce dust [4].Clayey diatomite is currently used principally as ad-sorption and insulation materials, while carbonaceous di-atomite is used mainly for the production of Clinker andthe neutralization of acid-water drainage [5–7].Diatomite deposits of commercial grade have been locatedin marine and lacustrine deposits of Miocene and Plioceneage worldwide [8]. Although several diatomite deposits arelocated in Greece, their usage as adsorption materials hasnot been established thus far [9]. Two diatomite beds ofa total 3 m thick occurring as intercalations in tuffaceousrock of Milos Island, Aegean Sea, Greece, are co-extractedwith the tuffs and used as a cement additive by the Greekcement company TITAN S.A. The aim of the present studyis therefore to examine the mineralogical composition andthe absorption capacity of the raw materials originatingfrom the Florina Basin (Amynteo area) and the Drimos-Sarantaporo Basin (Elasson area), in order to characterizethem as industrial absorbents.

2. Geological settings

The Klidi area is part of a broader Neogene Basin in NWMacedonia (Greece). The basin extends from Monastiri(F.Y.R.O.M), in a NNW-SSE direction, up to the hills ofKozani through the cities of Florina, Amynteo and Ptole-mais. The specific basin is almost 100 km long and 15 -20 km wide [10]. The Drimos-Sarantaporo Basin is ofthe same age and extends to the South of the aforemen-tioned basin (Figure 1). Based on field measurements ofseveral natural and artificial outcrops of both basins, the

estimated reserves are more than 5 000 000 m3 each.

Figure 1. Map of Greece showing the studied locations of the Klidiand Drimos areas.

The basins are of Upper Miocene through Pliocene ageand are developed above metamorphic rocks and ophio-lites belonging to the Pelagonian Geotectonic Zone. Eventhough the Florina Basin hosts significant Upper Miocenelignite deposits, the Elasson-Sarantaporo Basin hostsonly insignificant lignite seams of the same age [11–19].The diatomaceous beds are mostly homogenous and occuras overburden of the lignite layers in both basins. Raresiltstone and sandstone beds are interbedded to the di-atomaceous rocks. Fe-Ca phosphates such as anapaiteand mitridatite (surface samples) and Fe-phosphates suchas vivianite (borehole samples) occur in both basins in theform of organic material replacements [20, 21].

3. Materials and methods

Two bulk samples of 100 kg each were collected from theKlidi-Florina (KL) and the Drimos Sarantaporo (DR) di-atomaceous rocks, which represent a total thickness of20 m of the clayey rocks. The samples were very fine-grained and homogenous, having bluish and yellowishcolor respectively. The KL sample was extracted fromthe Klidi lignite mine, located SW of Amynteo village,whereas the DR sample was extracted from a technicaloutcrop NE of Elasson village.The mineralogical composition of the collected sampleswas determined by X-Ray Diffraction (XRD), Thermo-

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

Gravimetric (TG/DTG) and Differential Thermal Analysis(DTA), Fourier Transform (FT-IR) spectroscopy and Scan-ning Electron Microscopy analysis (SEM).

The X-Ray power diffraction patterns were obtained usinga Siemens D-5000 diffractometer, with Ni-filtered CuKa1radiation (G = 1.5405 Å), operating at 40 kV, 30 mA. For X-Ray Diffraction (XRD) analyses, samples were preparedas non-oriented and oriented mounts. The latter, whichconsisted of < 53 µm material in order to avoid most ofthe detrital minerals, was firstly separated by centrifugingand 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 mineralphases.

The IR measurements were carried out using a FourierTransform IR (FT-IR) spectrophotometer (Perkin Elmer880). The FT-IR spectra, in the wave number range from400 cm−1 to 4 000 cm−1, were obtained using the KBrpellet technique. The pellets were prepared by pressinga mixture of the sample and of dried KBr (sample: KBrapproximately 1:200), at 8 tons cm−2.

The Thermo-Gravimetric (TG/DTG) analysis was obtainedsimultaneously using a Mettler Toledo 851 instrument.The samples were heated from 20°C to 1 200°C at a con-stant rate of 10°C min−1.

A Jeol-JSM-5600 SEM-EDS type of Scanning ElectronMicroscope 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 ALSChemex Laboratories at Saskatchewan, Canada. The ma-jor 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 anda combination of ICP-MS and ICP-AES.

Oil and Water Adsorption were carried out following theBritish Standard method (BS-3483: part B7) for testingpigments for paints and the procedures used by the BGS,UK [22] and by LITHOS Laboratory (I.G.M.E. Athens).2 kg of the bulk samples were prepared using the quar-tering method. Oil absorption was determined throughthe addition of linseed oil (specific gravity of 0.95) by bu-rette drops to 100 g of sample, followed by rubbing witha palette knife, till a paste of smooth consistency wasformed.

4. Results and discussion

4.1. Mineralogy of the Klidi-Florina region

4.1.1. X-Ray Diffraction (XRD) analysis

The clay minerals prevailed in the sample, with muscovitebeing the dominant phase, followed by kaolinite and chlo-rite (Figure 2). Smectite was not found in the sample.Quartz was identified, feldspars and opal-A. Minor contri-bution of carbonates (dolomite) were also present (< 10%).

Figure 2. XRD diagram of a representative diatomite sample fromKlidi-Florina. Mu:Muscovite, Ka:Kaolinite, Chl:Chlorite,Qz:Quartz, Fd:Feldspars, Do:Dolomite. Opal-A is repre-sented by the hump occurring between 20-28 degrees.

Figure 3. XRD diagram of a representative diatomite sample fromKlidi-Florina. a) “as it is” b) after heating up to 500°C.

Quartz was identified by its typical peaks (101) at d_spac-ing=3.34 Å and (100) at d-spacing=4.26 Å, while feldsparswere identified by the peaks (002) at d-spacing=∼3.19 Åand (220) at d-spacing=∼3.24 Å. The broad hump reg-istered between 20 and 26 2S, indicated the presence ofopal A. Dolomite was identified by its typical peak (100) atd-spacing=∼2.8 Å. In addition, muscovite was identified


by the sharp diffraction peak (001) at d-spacing=∼10 Åand (003) at d-spacing=∼3.34 Å. Kaolinite was identifiedby its typical (001) and (002) peaks at ∼7.1 Å and d-spacing=∼3.5 Å, and chlorite by (001) and (002) peaks atd-spacing=∼14 Å and d-spacing=∼7 Å, respectively. Inan orientated sample (Figure 2) the overlap of the kaoli-nite and chlorite peak (d_spacing=∼7.1 Å) is shown. Inorder to identify these two minerals (kaolinite and chlo-rite), the thermal behavior of the samples was examined(Figure 3).The samples were heated up to 500°C for 2 hours, ina static oven, and cooled down at room temperatureand examined by x-ray power diffraction. A decrease inthe intensity of the characteristic diffraction peaks at d-spacing=∼7.1 Å and d-spacing=∼3.52 Å, due to the col-lapse of kaolinite as shown in Figure 3, clearly indicatesthe presence of kaolinite. No smectite was found in thestudied samples, as its typical peak (100) should be shiftedfrom d-spacing=∼14 Å to (d-spacing=∼17 Å) lower 2Safter saturation with ethylene glycol (Figure 4).

Figure 4. XRD diagram of a representative diatomite sample fromFlorina. a) “as it is” b) after saturation with ethyleneglycol.

The mineralogical composition of the examined samplesfrom Klidi-Florina region which was identified after beingheated up to 1 100°C is shown in Table 1.

4.1.2. Fourier Transform Infrared Specrtoscopy (FT-IR)

From the derived FT-IR spectra of representative samples(Figure 5) from Florina, the following results are inferred:

• The ∼3 694 cm−1 strong band arises from the in-phase symmetric stretching vibration of the OHgroups, either outer or inner surface OH of the oc-tahedral sheets, which form weak hydrogen bondswith the oxygens of the next tetrahedral layer [23].On the other hand, the ∼3 612 cm−1 strong bandis due to the stretching vibrations of the “inner OH

Table 1. Mineralogical composition of the studied samples fromFlorina region, before and after being heated at varioustemperatures.

“KL” Qtz Op Fld Dol Ka Mu Chl

as it is MD MD MD TR MJ MJ MDafter heated MD MD MD TR TR MJ MJ

at 500°Cafter heated MJ MJ MD – – MD –

at 850°Cafter heated MJ MJ MD – – – –at 1 100°CQtz:Quartz, Op:opal-A (poorly crystallised opal-CT at1 100°C), Fld:Feldspars, Dol:Dolomite, Ka:Kaolinite,Mu:Muscovite, Chl:Chlorite

groups”, lying between the tetrahedral and the oc-tahedral sheets [24].

• The broad band, near 3 436 cm−1, is due to H-O-Hvibration of absorbed water.

• The band at ∼1 632 cm−1 is due to OH bendingvibrations 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 stretch-ing 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 OHtranslational vibration [24, 25].

• The bands at around ∼649, ∼529 cm−1 originatefrom Si-O-AlVI vibrations (Al in octahedral co-ordination), while the band at around 468 cm−1 isattributed to the Si-O-Si bending vibrations [24,26].

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

4.1.3. TG and DTG analysis

The results of the thermal study of the samples examinedafter heating up to 1 200°C, at a rate of 10° min−1 confirmthe presence of muscovite, kaolinite, and chlorite. Fromthe TG and DTG curves of a representative sample (Fig-ure 6), we conclude that:

• In the temperature range from 25°C to 100°C, theweight loss due to absorbed water is 2.66%.

• The crystalline water contained in the opal-A islost at about 120 degrees [27].


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

• In the temperature range from 400°C to 500°C, therapid weight loss (4.32) is documented by the steepslope of the TG curve and a characteristic peak onthe DTG curve, which extends up to the temper-ature of ∼600°C. This is attributed to the dehy-droxylation of the kaolinite, (due to the loss of OHgroups, surrounding the AlVI atoms) and the pro-gressive transformation from the octahedral coordi-nated Al, in kaolinite, to a tetrahedral coordinatedform, in metakaolinite, through the breaking of OHbonds [20].

• The at ∼780°C and ∼1 000°C peaks on the DTGcurve correspond to chlorite and muscovite respec-tively.

Figure 6. Typical TG curve of a representative diatomite samplefrom Florina. Mu:Muscovite, Ka:Kaolinite, Chl:Chlorite.

4.2. Mineralogy of Drimos-Sarantaporo re-gion

4.2.1. X-Ray Diffraction (XRD) analysis

In the bulk sample of this area, clay minerals prevailedas in the Florina sample, but vermiculite was present in-stead of chlorite. Opal-A is the dominant phase, followedby muscovite, kaolinite and vermiculite (Table 2 and Fig-ure 7). Detrital minerals such as quartz and feldspars werealso reported. Carbonate minerals were not detected.

Figure 7. XRD diagram a representative diatomite samplefrom Drimos-Sarantaporo. Mu:Muscovite, Ka:Kaolinite,Ve:Vermiculite, Qz:Quartz, Fd:Feldspars. Opal-A is re-ported as the hump located between 20-28 degrees.

The discrimination among vermiculite, chlorite and smec-tite, was succeeded by the study of the thermal behaviorof the samples, as well as their behavior after saturationwith ethylene glycol (Figure 8 and Figure 9). The sampleswere heated up to 500°C for 2 hours, in a static oven (Fig-ure 8). Samples were then cooled at room temperature andexamined by x-ray power diffraction. The absence of thetypical peak at d-spacing=∼14 Å, in combination with itsshifting from d-spacing=∼14 Å to d-spacing=∼16.3 Å ofthe glycolated sample, indicated the absence of chloriteand 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 followingresults:

• The ∼3 694 cm−1 strong band arises from the in-phase symmetric stretching vibration of the OHgroups, either outer or inner surface OH of the oc-tahedral sheets, which form weak hydrogen bondswith the oxygens of the next tetrahedral layer [23].On the other hand, the ∼3 616 cm−1 strong bandis due to the stretching vibrations of the “inner OH


Figure 8. XRD diagram of a representative diatomite sample fromDrimos-Sarantaporo. a) “as it is”, b) after heating up to500°C.

Figure 9. XRD diagram of a representative diatomite sample fromDrimos-Sarantaporo. a) “as it is” b) after saturation withethylene glycol.

groups”, lying between the tetrahedral and the oc-tahedral sheets [24].

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

• The band at ∼1 637 cm−1 is due to OH bending vi-brations of adsorbed water in sheetsilicate mineralsas well as the H2O of opal-A.

• The 1 093 cm−1 band is attributed to the stretchingvibration of Si-Oapical and the 1 040 cm−1 bandarises from the Si-O-Si vibration.

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

• The band at around 529 cm−1 originates from Si-O-AlVI vibration (Al in octahedral co-ordination), whilethe band at around 470 cm−1 is attributed to theSi-O-Si bending vibrations [24, 26].

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

Table 2. Mineralogical composition of the studied samples fromDrimos-Sarantaporo region, before and after being heatedat various temperatures.

“DR” Qtz Op Fld Il-Mu Ka Chl Ve Cr Ens

as it is MD MD MD MJ MD TR MD Ve –after heated MD MD MD – – – – Ve –

at 500°Cafter heated MD MD MD – – – – Ve TR

at 850°Cafter heated MJ MJ MD – – – – TR –at 1 100°CQtz:Quartz, Op:opal-A (poorly crystallised opal-CT at1 100°C), Fld:Feldspars, Il-Mu:Illite-Muscovite, Ka:Kaolinite,Chl:Chlorite, Ve:Vermiculite, Cr:Cristobalite, Ens:Enstatite

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

Figure 10. FTIR spectrum of a representative diatomite samplefrom Drimos-Sarantaporo.

4.2.3. TG and DTG analysis

The results of the thermal study of the examined samplesafter being heating up to 1 200°C, at a rate of 10°C min−1

confirm the presence of kaolinite, muscovite and vermi-culite. From the TG and DTG curves of a representativesample (Figure 11), we conclude that:


• In the temperature range from 25°C to 100°C, theweight loss due to absorbed water is 2.32%.

• The second dehydration step observed in the tem-perature range 100-300°C, corresponds to the re-lease of water molecules, which were in the in-terlayer space of vermiculite [29]. Opal-A loosesthe crystalline water at the same range of temper-atures [27].

• In the temperature range from 400°C to 600°C, therapid weight loss (2.26%) is documented by thesteep slope of the TG curve, as well as the charac-teristic peak on the DTG curve. This is attributedto the dehydroxylation of the kaolinite, (due to theloss of OH groups, surrounding the AlVI atoms) andthe progressive transformation from the octahedralcoordinated Al, in kaolinite, to a tetrahedral coordi-nated form, in metakaolinite, through the breakingof OH bonds [26]. The dehydroxylation of the ver-miculite is observed in the same temperature range.It is important to mention that chlorite and mont-morillonite give peaks at higher temperatures.

Figure 11. Typical TG curve of a representative diatomite samplefrom Drimos-Sarantaporo. Ka:Kaolinite, Ve:Vermiculite

4.3. Scanning Electron Microscope analysis(SEM)

The SEM study of the diatomaceous rocks indicated thatthe diatom frustules were mostly well preserved, havingdisk or oblong shape and ranged in size from 5 to 30 µm(Figure 12, Figure 13). The predominant shape of the di-atoms in the DR clayey diatomite were that of disk shapesbelonging to Cyclotella sp., while in KL clayey diatomitecould be observed also as oblong frustules. Most diatomfrustules retained their minute structure, indicating that

silica diagenesis was not promoted within the specific de-posits, probably due to low permeability of the clayeydiatomite.

Figure 12. Disc-shaped diatom frustules (cyclotella sp.) sunk in aclayey Matrix, bulk sample DR of Drimos-Sarantaporoarea.

Figure 13. Well presented diatom frustules surrounded by detritalcrystals, 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 sampleswere 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 commonlya waste or recycled material, whereas the latter is com-monly used for absorption applications in industrial scale.Silica, alumina and iron oxide were the main constituentsof the samples. The SiO2 content corresponded to sil-ica polymorphs (quartz and opal-A) and aluminosilicateminerals, while Fe2O3 to the amounts of chlorite and ver-miculite present in Klidi-Florina and Drimos-Sarantaporosamples respectively.The trace element content of both samples was typicalfor clayey rocks and there was no heavy or base metalenrichment. The concentration of Cu and Zn were higherin the fine grained fractions (< 0.3 mm) which were richerin clay minerals. These enrichments could be attributedto the ability of clay fractions to absorb various metals(Figure 14).


Table 3. ICP-MS chemical analysis of the clayey diatomite rocksamples of Florina KL and Drimos-Sarantaporo regionsin grain fractions of less than 0.3 mm and 0.3-1.7 mmrespectively.

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

SiO2 64.70 64.10 65.20 65.70Al2O3 13.55 12.90 16.60 16.60Fe2O3 10.90 12.20 6.33 6.74CaO 2.51 2.30 1.92 1.69MgO 1.86 1.80 1.92 2.02Na2O 1.47 1.22 1.52 1.24K2O 1.92 1.83 2.57 2.57TiO2 0.65 0.60 0.87 0.82MnO 0.20 0.24 0.11 0.21P2O5 0.37 0.62 0.13 0.17SO3 0.02 0.02 0.65 0.63LOI 2.26 2.25 2.71 2.10

Total 100.41 100.08 100.53 100.49

Figure 14. Water and Oil absorption of KL and DR dried andheated bulk samples showing the stabilization or thedecrease in adsorption capability of heated samples.

4.5. Oil and water absorption

The oil and water absorption test was carried out in thefine grained fractions (< 0.3 mm) of the examined samplesand resulted in good absorption capacity of both KL andDR bulk samples (Figure 14). Tests were performed ina raw state and also on heated samples at temperaturesof 400°C, 670°C and 800°C. Sintering of both materialsoccurred at about 1 100°C.In detail, there seemed to be an increase in the absorp-tion capability in the heated materials compared with theraw ones. From the diagram in Figure 14, it is clearthat the absorption capacity is either stabilized, or de-creased in the range of temperatures between 670°C and800°C for the examined samples of both Klidi-Florina and

Table 4. Trace element content of fine-grained fractions of less than0.3 mm and 0.3-1.7 mm, from bulk samples of FlorinaKL and Drimos-Sarantaporo DR regions, analyzed by ICP-MS.

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

Ag 0.1 0.1 0.3 0.2As 2.6 2.8 11.3 10.2Ba 580 650 390 380Be 3.4 3.5 3.0 3.0Bi 0.5 0.6 0.5 0.4Cd 0.2 0.3 0.6 0.6Ce 75.6 80.1 58.4 54.1Co 16.7 24.7 30.5 28.5Cr 59 61 106 111Cs 4.9 5.5 5.4 5.5Cu 412 45.4 306 56.2Ga 24.5 26.1 20.8 19.4Ge 0.2 0.3 0.2 0.2Hf 0.5 0.5 0.8 0.7ln 0.1 0.1 0.1 0.1La 37.3 39.6 29.9 27.3Li 38.5 42.5 30.6 29.5

Mo 1.2 1.5 1.1 1.1Nb 14.4 14.5 13.5 12Ni 38.3 46.7 83.6 83.6Pb 20.2 26.8 26.0 23.1Rb 125 141 122 116Sb 0.3 0.3 0.6 0.5Sc 17.1 17.6 12.7 11.5Se 2.0 2.0 2.0 2.0Sn 3.0 3.1 2.5 2.3Sr 181 166 162 129Ta 1.1 1.1 1.0 0.9Te 0.1 0.1 0.2 0.1Th 13.4 14.6 13.5 12.7Tl 0.8 0.9 1.1 1.0U 3.3 3.7 3.8 3.7V 113 119 124 130W 6.1 6.8 3.6 3.9Y 30.7 31.5 25.3 23.5Zn 147 115 156 132Zr 15.1 15.4 26.6 23.8

Drimos-Sarantaporo areas. The above mentioned stabi-lization presented in both oil and water treatment is at-tributed to the early and partial vitrification of the ma-terial. In all temperatures and grain-size fractions, theFlorina samples in which clay minerals predominate, haveslightly better absorption capacity than that of Saranta-poro, in which opal-A predominates. It could be concludedthat the specific clay minerals mixture of the studied ar-


eas have higher absorption capacity than the biogenic dueto (probably particle size distribution, grain size, shape,crystal/mineral structure).The oil and water absorption capacity of the samples stud-ied were compared to that of already examined materials(Figure 15). As far as the oil absorption capacity wasconcerned, both the KL and the DR samples showed com-parable values to that of diatomite and bentonite ‘’Jor-dan” whereas they had higher absorption capacity thanthe specific kaolinite and lower than the palygorskite-richsamples of Greece (Figure 15). The water absorption ca-pacity of the samples studied showed higher values thankaolinite and lower values than that of bentonite and pa-lygorskite (Figure 15).

Figure 15. Diagram of oil and water absorption in materials fromthe studied areas and other regions [30–32].

5. Conclusions

The evaluation of raw and thermally treated clayey di-atomite bulk samples from northwest and central Greece,by means of XRD, TG/DTG, FTIR spectroscopy, and SEM;as well as Oil and Water absorption capability, concludedthat:

• The mineralogy of Florina and Drimos-Sarantaporoclayey diatomite bulk samples is dominated by thepresence of clay minerals and opal-A of biogenicorigin. Concerning the clay minerals, muscoviteis the dominant phase in Florina sample, followedby kaolinite and chlorite. Minerals of the mont-morillonite group were not identified. Opal-A ismostly represented by well preserved diatom frus-

tules. In addition, quartz and feldspars of detritalorigin are significant components of the sample. Inthe Drimos-Sarantaporo sample, muscovite is thepredominant clay mineral phase, whereas kaolin-ite and vermiculite are also significant clay min-eral phases. Minerals of the montmorillonite groupwere not identified. Opal-A is also represented bydiatom frustules, and the detrital minerals phasesby quartz and feldspars.

• The diatom frustules idnetified in the bulk samplesof both areas constitute a significant portion of theclayey rock and hence, play an important role inthe absorption capability of the samples studied.

• The measurement of Oil and Water Absorption ca-pacity of the studied samples, range from 70 to 79%and 64 to 70% for Florina and Drimos-Sarantaporosamples respectively. The dominance of clay min-erals in the Florina sample compared with that ofthe Drimos-Sarantaporo sample could be related tothe higher absorption capacity of the Florina sam-ple, indicating that the clay minerals of the studiedsamples have higher absorption capacity than thatof the diatom frustules that dominate in the Drimos-Sarantaporo sample.

• The given measurements indicate that the exam-ined clayey diatomite bulk samples are appropri-ate for use as absorption materials in an industrialscale. As presented from literature data [33], cur-rently used industrial absorbents have an efficiencyto absorb up to 60-70% of their weight in liquid,hence the samples studied are capable for such ap-plications. In addition, taking into account that thetotal market for industrial spillage absorbents inEurope is around 120 000 to 150 000 tpa, with di-atomite being the biggest volume absorbent [33], thetested clayey diatomite have significant industrialpotential.

Acknowledgments

Thanks are expressed to Ms. Chalikiopoulou Fotini, geol-ogist and to Mr. Athanasio Tselo, technician, of LITHOSLaboratory of I.G.M.E., Athens, for their valuable technicalsupport during the implementation of the laboratory teston absorption capacity of the studied samples. We alsothank Mr. Evangelos Michailidis, Geology and Geoenvi-ronment Department, NKUA, for his assistance during theSEM analysis.


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