Kleopas Michailidis

Mineralogy, geochemistry and physical properties of fly ash from the Megalopolis lignite fields, Peloponnese, Southern Greece

Results are given on the mineralogy, morphology, geochemistry and physical characteristics of fly ash from the Megalopolis lignite fields, Peloponnese (S. Greece). The main mineral species present are quartz, anhydrite, plagioclase, haematite, gehlenite and calcite. Also present, in minor and trace amounts, are lime, alkali feldspars, bassanite, gypsum, mica and unburnt lignite. Morphologically, fly ash consists of irregularly shaped, oval and spherical particles, of widely varying sizes. Chemically, the fly ash samples examined fall in the pozzolan field in the triangular diagram CaOSiO2Al2O3. The trace elements As, Cd, Mo and Se, and Ni, V and Zn, of great and moderate environmental concern respectively, occur in concentrations higher than the respective Clarke values. Ash fusion temperatures vary within the range 1257°C (initial deformation temperature) to 1339°C (flow temperature) on average. Fouling and slagging parameters of the ash are within the preferred ranges of empirical practice. The chemistry of the fly ash reveals properties of concern to the construction industry, to the prediction of lignite-fired boiler performance and to health and environment.

IC-ICP-MS and IC-ICP-HEX-MS determination of arsenic speciation in surface and groundwaters: preservation and analytical issues

Abstract Understanding the biogeochemical behaviour of arsenic in the weathering and shallow subsurface environment depends critically upon determining the nature and distribution of the chemical species present in natural waters. To this end, coupled ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) is widely used, though species fractionation during ultrasonic nebulization, and matrix-dependent ionization in the plasma are analytical issues that need to be addressed. Hexapole collision cell technology is shown to be effective in suppressing chloride-based polyatomic interferences. Irrespective of the analytical technique used, As(III)/As(V) ratios of natural waters may change substantially during storage due to (1) differential adsorption of arsenic species on hydrated ferric oxides (HFOs); and (2) microbial activity. A wide range of apparently contradictory speciation changes observed by various workers can be rationalized in terms of the differences of microbial consortia present in different water samples. Arsenic speciation in certain water types can be stabilized for days or even weeks by combined filtration, acidification and refrigeration whilst the addition of EDTA and the use of 0.1 μm filters is indicated for iron-rich waters and waters with high activities of redox-active bacteria, respectively. Although the use of hydrochloric acid has been reported elsewhere as resulting in the apparent oxidation of As(III), we show that for certain water types it acts as an extremely effective preservative of arsenic speciation.

Technical properties of compounded kaolin sample from Griva (Macedonia, Greece)

Abstract The purpose of this paper is to establish the possible industrial applications of Griva kaolin. This kaolin comes from the alteration of gabbroic rocks from the Griva area, Macedonia, Greece. Mineralogically, the kaolin is composed mainly of kaolinite associated with vermiculite and plagioclases, and traces of quartz, amphiboles, halloysite and smectites. The kaolin grain-size analysis shows that the kaolin is mostly finer than

Zoned chromites with high Mn-contents in the Fe-Ni-Cr-laterite ore deposits from the Edessa area in Northern Greece

The mineralogy of the transported Fe-Ni-Cr-laterite ore bodies from the Edessa area in Northern Greece was studied. The special emphasis was on the textural features and chemistry of chromite. The chromite was residually inherited in laterites from weathered ultramafic rocks and it displays zonation. Three main zones were optically distinguished: an inner chromite zone, an intermediate ferritechromite zone and a magnetite rim. These three zones have distinct compositions. The major oxides MgO and Al2O3 decrease from the chromite core to the ferritechromite zone, while FeOt increases and Cr2O3 either increases or decreases. A characteristic chemical feature of the chromite is the very high Mn-content in the ferritechromite zone, up to 20%wt MnO. Chemical zonation has, however, been detected in optically unzoned chromite cores rimmed by magnetite.The zoning and the high Mn-content of the chromite is a result of serpentinization in the presence of Mn-rich fluids, following lateritic weathering and finally Alpine low-grade metamorphism.

The geology and coal petrology of a Pleistocene lignite profile at Horemi mine, Megalopolis Basin, Peloponnese (southern Greece)

Abstract The present study describes the geology, coal petrology and geochemistry of a Pleistocene coal-bearing succession at Horemi mine, Megalopolis Basin (southern Greece). Within a 45-m interval 9 coal seams are exposed, ranging in thickness from 20 cm to 10 m. Reflectances measured on the maceral-type eu-ulminite B range between 0.24 and 0.31% mean R random . This indicates a coalification stage in the transition zone between peat and lignite rank of the A.S.T.M. classification for the Horemi coals. Petrographic studies demonstrated the immature nature of these coals and the low degree of compaction during diagenesis. Compositionally, the Horemi coals are characterized by low amounts (5.3 vol%) of the inertinite group macerals, moderate amounts (11.9 vol%) of liptinite group macerals and very high amounts (82.8 vol%) of the huminite group macerals (on average and mineral-matter-free basis). Within the latter group densinite, attrinite and ulminite make up the bulk of the samples. Results from proximate and ultimate analysis gave on average 53.7% bed moisture, and 37.3% ash, 45.8% volatiles and 18.1% fixed carbon (d.b). Calorific value determinations vary between 1805 and 5470 kcal/kg. Mineral matter is high, varying within the range 20.8–51.9 vol%. Identifiable mineral constituents include quartz, anhydrite, illite, feldspars, calcite, gypsum and chlorite, and minor amounts of barite and pyrite. Reflectances obtained from ulminite were found to be negatively correlated with volatile matter, whereas there is a trend for a positive correlation of them with calorific values.

Correlation of the methylating capacity of river and marine sediments to their organic sediment index

Methylation experiments of the metals Sn, Pb and Hg were carried out using representative terrestrial and marine sediment samples from the Axios river and Thermaikos Gulf in northern Greece. GC-FID, GC-TCD and GC-MS were used. The experiments were carried out on sterilised and bioactive samples by adding pure metals and metal salts (chloride, nitrate, oxalate, acetic, penicillaminic, methioninic and cysteinic). Except for sterilised HgCl2, methylated derivatives of Sn, Pb and Hg were produced only from bioactive sediments, and therefore higher yields were measured when nutrients were added to the sediments. Volatile products (CH4, CO2, H2S) of biological activity range between 35 and 250 mg l-. The correlation of methylation yield with organic sediment index (OSI), determined as the wt% product of [organic carbon] × [organic nitrogen], is positive for all the metals and metal salts added in the sediments. Methylation yields for Hg are found to be four orders of magnitude higher than those of Pb and Sn. In low OSI (terrestrial) sediments, the rate of Hg-methylation is higher than those of Pb and Sn. In high OSI (marine) sediments, where methylation of most of the contained Hg has taken place, methylation of Pb is slightly faster than Sn.

An X-ray, EPMA, and oxygen isotope study of vermiculitized micas in the ultramafic rocks at Askos, Macedonia, Greece

Abstract Extensive metasomatic zones of vermiculite-, tremolite-, chlorite-, and talc-rich rocks have been developed at the contacts of serpentinized ultramafic bodies and surrounding two-mica gneisses in the Askos area, Macedonia, Greece. These zones are probably related to the intrusion of acid magmatic bodies in the area. X-ray and EPMA studies confirmed the formation of vermiculite through a layer-by-layer transformation of original micas. In decreasing abundance, the following mixed-layer and discrete phases were identified: biotite/trioctahedral vermiculite (hydrobiotite), biotite/smectite, trioctahedral chlorite/trioctahedral vermiculite (corrensite), vermiculite/smectite and discrete biotite, vermiculite, chlorite and talc. The 2–20 μm fraction of the vermiculitic samples consists mostly of biotite/vermiculite (>40%) with the biotite percentage dominating in the mixed phase. Lower abundances (20–40%) of biotite/smectite and chlorite/vermiculite occur in both finer fractions (2–20 and

Lead removal from aqueous solutions by natural Greek bentonites

Abstract Three bentonite samples (B1, B2, B3) from Milos Island, Greece, were investigated by XRD, AAS, DTA-TG, FTIR and specific surface area measurement techniques. A laboratory batch study has been performed to investigate the adsorption characteristics of lead ions (Pb2+) onto natural bentonite samples. The effect of various physicochemical factors that influence adsorption, such as solution pH (2-6), adsorbent dosage (1-10 g L-1), contact time (20-360 min), and initial metal ion concentration (5-150 mg L-1) was studied. A number of available models like the Lagergren pseudo first-order kinetic model, the pseudo second-order kinetic model and intra-particle diffusion were utilized to evaluate the adsorption kinetics. The adsorption of Pb2+ was modelled with the Langmuir, Freundlich and D-R isotherms. The maximum Pb2+ adsorption capacities for B1, B2 and B3 were 85.47 mg g-1, 73.42 mg g-1 and 48.66 mg g-1, respectively.

An EPMA and SEM study of the Mn-oxide mineralization of Kato Nevrokopi, Macedonia, northern Greece: Controls on formation of the Mn4+ oxides

Abstract EPMA and SEM studies of tunnel-structured todorokite and nsutite and layer-structured chalcophanite and birnessite from the Kato Nevrokopi battery grade Mn-mineralization were performed. The chemistry of todorokite, formed at hypogene and supergene environments in an increasing order of weathering, reflects different pH and oxidation conditions. The data also point to a clear dependence of the development of late stage hypogene and early supergene Mn4+-oxide paragenesis on the host rock and protore composition and the mobilities of base metals (mainly Zn), alkalis and alkaline earths (mainly Ca). The chemistry and development of (large cation-bearing) nsutite as in situ oxidations and banded poorly crystalline (with structural defects) aggregates in veins and associated karstic cavities, together with birnessite, indicates the influence of climate, oxidation and water table fluctuations. The data on chalcophanite revealed a deposition, under low fO2 conditions, from acid meteoric fluids produced by weathering of vein sulphides. Birnessite formation reflects a prevalence of higher fO2 in weathered veins and karstic cavities. The evolution of well developed layer structures through poorly crystalline to amorphous tunnel-structured nsutite is probably controlled by a Zn-saturation of the ore fluids.

Kaolin weathering crusts on gabbroic rocks at Griva, Macedonia, Greece

Abstract The hydrothermal and weathering alteration products of the gabbroic rocks at Griva, Macedonia, Greece, are examined using petrographic, mineralogical and chemical data. The kaolin crusts have a thickness of 1 to 8 m and extend over an area of about 5 km 2 . Many gabbro-pegmatitic veins crosscut the semi-friable kaolins. The crusts have not been intensively washed and thus the primary minerals exist within the weathered profile in significant amounts. Essential constituents are plagioclase, actinolite, clinopyroxene, clinozoisite, dolomite, kaolinite, corrensite and pyrophyllite, with varying proportions in the different particle size fractions. The 18 O values. According to the classification of Konta the kaolins studied are of the low grade type and probably only suitable for the ceramic industry.