C. Sikalidis

Caesium selectivity and fixation by vermiculite in the presence of various competing cations

Caesium selectivity coefficients (k(G)) that were determined with respect to Na-, Mg-, Ca-, Sr- and Ba-ions, for Kent and Libby vermiculites,ranged from 4.8 to 11 (litres/mol) [Formula: see text], much higher than those with respect to K- and NH(4)-ions (0.01 to 0.06), indicating the high affinity of vermiculite for the weakly hydrated cations. Higher K(G) values were also found for low and extremely low Cs concentrations. Vermiculite samples were very effective in removing (137)Cs from solutions containing traces of (137)Cs (4 ng litre(-1)) and extremely higher quantities of K-, NH(4)-, Na-, Mg- and Ca-ions (500 mg litre(-1)). 0.5N chloride solutions of H, NH(4), K, Na, Mg and Ca were unable to remove Cs from Cs-saturated v vermiculite samples which had undergone heating at 110 degrees C. Significant quantities (50-65%) of fixed Cs were removed from these samples only after treatment with strong acids. The high preference and fixing ability of vermiculite for Cs suggests the use of this mineral as a radioactive Cs decontaminating agent.

Utilisation of municipal solid wastes for mortar production

In this study we examined the thermal co-processing of municipal solid waste (MSW) and other raw materials needed for the production of clinker, and consequently of mortar, without causing environmental problems. The technique is related to a method of manufacturing mortar by firing at high temperature a mixture of mineral raw materials (limestone, clayey materials, silicates and iron oxides) together with dried and properly treated solid wastes, according to the Greek Patent 1003333. The MSW is separated into two fractions; the heavy one containing mainly earthen materials, stones, broken ceramics, glass and other similar materials and the light one containing mainly paper, wood, light plastics, leather and cloth pieces, various fibres and other similar combustible materials. The dried and crushed heavy fraction is introduced directly at the ∼1100 °C zone of a specific two stages rotary kiln, where it meets the mixture of the mineral raw materials. The light fraction is used with a mixture of pet-coke, in an appropriately designed jet burner to heat the rotary kiln. The clinker obtained is milled together with gypsum to produce a hydraulic mortar for building applications. The main advantages of the method are the significant volume reduction of municipal solid wastes by incineration without toxic gas emissions and the production of a valuable material. An economic analysis and evaluation was carried out. It was concluded that the installation of a unit, treating 500 t/day of MSW and producing about 433 t/day of mortar, seems to be economically profitable.

Distribution of fission products in dust samples from the region of Thessaloniki, Greece, after the Chernobyl nuclear accident

The distribution of the fission products (95)Zr, (95)Nb, (103)Ru, (106)Ru (determined through (106)Rh), (125)Sb, (129m)Te, (134)Cs, (137)Cs, (140)Ba, (140)La, (141)Ce and (144)Ce has been determined in dust samples from the region of Thessaloniki, Greece, after the nuclear accident at Chernobyl. The samples studied also included (110m)Ag, not belonging to the products of (235)U fission. Samples showing higher concentrations of radionuclides also show a higher content in clay minerals, whereas samples having low concentrations of radionuclides usually contain large amounts of quartz and feldspars. Desorption and leaching experiments using solutions of chlorides of sodium, potassium, calcium and magnesium (0.5 N), as well as distilled and tap water, were also performed. Sodium and potassium chloride solutions were found to be efficient in desorbing and/or leaching of caesium and ruthenium isotopes to an extent of about 30%.

Thermal characterization of carbonate rocks, Kozani area, North-western Macedonia, Greece

Representative carbonate rock samples collected from the broader area of Kozani (NW Macedonia, Greece) are examined. The participation of constituents in the formations was determined combining three different methods of analysis, atomic absorption spectroscopy (AAS), X-ray diffraction analysis (XRD) and thermogravimetry (TG). The three methods are used in a complimentary way in order to specify the exact composition of the samples. Although the question about the composition can be answered by AAS, the percentage of the included calcite and dolomite can be determined with accuracy, only through TG analysis, under the appropriate conditions, regarding the gas carrier. The results of the analysis lead to a more complete view of the geological conditions that predominated in the studied area.

Ceramic building materials for electromagnetic interference shielding using metallurgical slags

Abstract Abstract The technological properties and the electromagnetic shielding efficiency of clay based ceramic building products prepared by using electric arc furnace slag (EAFS) and ladle furnace slag (LFS) as admixtures and fired at various temperatures were investigated. Chemical and mineralogical analyses were performed to characterise EAFS and LFS. The results showed that the ceramic specimens prepared by the addition of EAFS to the clayey material presented better shielding efficiency than the relevant of LFS, both tested in the same X-band frequency range (8–12 GHz). The prepared specimens showed water absorption, flexural and compressive strengths and firing shrinkage within accepted limits. Modulus of rupture and compressive strength values were slightly decreased by increasing the addition of EAFS and LFS. The technological characteristics were found to be affected by both the percentage of EAFS and LFS added as well as their grain size. Finally, the leaching test performed showed stabilisation of all studied toxic elements within the sintered ceramic structure.

Ammonium exchange capacity of the Xerovouni zeolitic tuffs, Avdella area, Evros Prefecture, Greece

Abstract Zeolitic tuffs from the Xerovouni location of the Avdella area (Evros Prefecture, Greece) contain on average 54 wt.% HEU-type zeolite, 6 wt.% smectite, 4 wt.% mica (64 wt.% microporous minerals), 8 wt.% alkali feldspar, 9 wt.% plagioclase, 11 wt.% cristobalite and 8 wt.% quartz (36 wt.% non-microporous minerals). The chemical formula of the HEU-type zeolite is Ca2.4K0.6Na0.4Mg0.3Al6.7Si29.3O72·17H2O and the tuffs contain on average 72.3 wt.% SiO2, 11.9 wt.% Al2O3, 1.2 wt.% Fe2O3, 1.0 wt.% MgO, 2.8 wt.% CaO, 1.3 wt.% Na2O and 1.9 wt.% K2O. The zeolitic tuffs show an average ammonium exchange capacity of 144 meq/100 g. HEU-type zeolite accounts for the most of the ammonium exchange capacity, while smectite and mica contribute to a relatively small extent. The ammonium exchange capacity of the Xerovouni zeolitic tuffs showed positive correlations with (a) the HEU-type zeolite content, (b) the total microporous minerals content, (c) the loss on ignition content and (d) the CaO content. Such materials could be used in a large variety of agricultural, aquacultural, industrial and environmental applications.

Immobilization of EAFD heavy metals using acidic materials

This study was undertaken to determine the chemical and leaching characteristics of the Electric Arc Furnace Dust (EAFD) generated by a Greek plant and to investigate various acidic materials efficiency on the EAFD stabilization. In order to investigate how [OH−] neutralization influences EAFD heavy metals leachability, Na HCO3 −, HNO3 and H3PO4 were used as acidic materials. The concentration of Pb in leachate was found between 40 and 3.7 × 103 mg Pb/kg of EAFD, exceeding in all EAFD samples the maximum acceptable limit (MAL) 25 mg/kg for landfill disposal. Neutralization of [OH−] with HCO3 − decreased Pb concentration in leachate at 350 mg Pb/kg of EAFD, while excess over a stoichiometry in HCO3 − addition increased leachability of Pb, Cd, Cr, Cu as well as F. Using HNO3 as an acidic material decreased leachability of almost all the parameters concerning the EC directive 33/19-01-2003 in a pH value up to 7.2, in exception of Zn. Zinc leachability showed a U shape curve as a function of pH value. The concentration of Zn was minimized in a concentration lower than 1 mg Zn/kg EAFD in a pH range 10.5 to 9 and exceeded the MAL 90 mg/kg at a pH value 7.2. However, the major disadvantage of HNO3 was proved to be its leachability, since NO3 − concentration in leachate was equal to HNO3 dose. H3PO4 was found the most promising acidic material for the chemical immobilization of heavy metals, since it decreased their leachability in a concentration significantly lower than MAL at a pH value up to 7.1. Finally, the concentration of Cl− ranged between 18 and 33 × 103 mg Cl−/kg EAFD exceeding in all EAFD samples the MAL 17 × 103 mg/kg. This high concentration of Cl− is attributed to the scrap and it could be reduced only by modification of its composition.

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.

Anticancer drugs loading into and in vitro release from faujasite

Abstract This investigation was carried out to determine whether the adsorptive and ionexchange properties of faujasite (FAU) could be used to delivery locally the anticancer drugs gemcitanine hydrochloride (dFdU.HCl) and oxaliplatin (DACH-Pt). A soaking procedure was used for the determination of the maximum adsorption capacity of FAU and the mechanism described here was achieved. 274 mg dFdU.HCl/g FAU were adsorbed in 16 h, while 48 h were needed for the adsorption of 79.7 mg DACH-Pt/g FAU. Drug release studies were carried out by soaking the samples of loaded FAU in simulation body fluids (SBF). After only one hour 76% of dFdU.HCl was released while the release of DACH-Pt from the FAU was more normal since 38% of DACH-Pt was released in the first 24 h.