P. Gamaletsos

Characterisation and management of ash produced in the hospital waste incinerator of Athens, Greece

Bottom and fly ash samples (BASH and FASH) from the APOTEFROTIRAS S.A. medical waste incinerator (Athens, Greece) were investigated. Powder-XRD data and geochemical diagrams showed BASH to be an amorphous material, analogous to basaltic glass, and FASH consisting of crystalline compounds (mainly CaClOH). Bulk analyses by ICP-MS and point analyses by SEM-EDS indicated a high content of heavy metals, such as Fe, Cu and Cr, in both samples. However, BASH was highly enriched in Ni while FASH was additionally enriched in Zn and Pb. Gamma-ray measurements showed that the radioactivity of both ash samples, due to natural and artificial radionuclides ((137)Cs, (57)Co), was within the permissible levels recommended by IAEA. According to EN-type leaching tests, BASH was practically inert with regard to the mobility of the hazardous elements in aqueous media. FASH, however, showed a relatively high EN (and TCLP) leachability with regard to Pb and Zn. Finally, the stabilisation method, suggested for the treatment of FASH, included compression of the powder into briquettes using an appropriate machine and embedding the briquettes into pozzolanic cement blocks. After this treatment, TCLP and EN-type tests showed minimal release of Pb and Zn, thereby demonstrating a reliable management of ash waste.

The role of nano-perovskite in the negligible thorium release in seawater from Greek bauxite residue (red mud)

We present new data about the chemical and structural characteristics of bauxite residue (BR) from Greek Al industry, using a combination of microscopic, analytical, and spectroscopic techniques. SEM-EDS indicated a homogeneous dominant “Al-Fe-Ca-Ti-Si-Na-Cr matrix”, appearing at the microscale. The bulk chemical analyses showed considerable levels of Th (111 μg g−1), along with minor U (15 μg g−1), which are responsible for radioactivity (355 and 133 Bq kg−1 for 232Th and 238U, respectively) with a total dose rate of 295 nGy h−1. Leaching experiments, in conjunction with SF-ICP-MS, using Mediterranean seawater from Greece, indicated significant release of V, depending on S/L ratio, and negligible release of Th at least after 12 months leaching. STEM-EDS/EELS & HR-STEM-HAADF study of the leached BR at the nanoscale revealed that the significant immobility of Th4+ is due to its incorporation into an insoluble perovskite-type phase with major composition of Ca0.8Na0.2TiO3 and crystallites observed in nanoscale. The Th LIII-edge EXAFS spectra demonstrated that Th4+ ions, which are hosted in this novel nano-perovskite of BR, occupy Ca2+ sites, rather than Ti4+ sites. That is most likely the reason of no Th release in Mediterranean seawater.

Mordenite-bearing tuffs from Prassa quarry, Kimolos island, Greece

We studied the geological and technological features of altered pyroclastic rocks from the main Bentomine Kimolian Enterprises S.A. quarry, in the Prassa region on the northeastern part of the Kimolos island, Greece. Particular emphasis was given to a MOR-type (mordenite) zeolite-rich material, tuff, which also contains K-feldspars, opal-CT and clays (mainly smectite) according to X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS). Additionally, it was characterised by a relatively low SiO 2 component (av. 70 wt%) compared to surrounding volcanic rocks. Mordenite crystals are alkali- (Na- and moreover K-) rich. According to trace-element discrimination diagrams (Zr/TiO 2 -Nb/Y), the protoliths of the mordenite-bearing tuffs could be trachyandesites, whereas Ti/Al-Eu/Eu* diagrams indicated a clear felsic affinity. Normalised REE patterns confirmed an expected negative Eu anomaly and a relative HREE depletion, whereas relevant multi-element diagrams indicated positive Cs, Rb, Th, Pb, U and Ta, negative Ba, P and Ti and compatible elements anomalies. The SSA BET of the rocks reached a value of 63 m 2 /g. In that case, the CEC was measured to be 98 meq/100 g. The above data suggest that the industrial minerals exploited in the Prassa quarry show good capabilities for the development of new products for innovative industrial and daily uses.

Isotopic analysis for degradation diagnosis of calcite matrix in mortar

Mortar that was used in building as well as in conservation and restoration works of wall paintings have been analysed isotopically (δ13C and δ18O) in order to evaluate the setting environments and secondary processes, to distinguish the structural components used and to determine the exact causes that incurred the degradation phenomena. The material undergoes weathering and decay on a large proportion of its surface and in depth, due to the infiltration of water through the structural blocks. Mineralogical analysis indicated signs of sulphation and dissolution/recrystallisation processes taking place on the material, whereas stable isotopes provided information relative to the origin of the CO2 and water during calcite formation and degradation processes. Isotopic change of the initial δ13C and δ18O in carbonate matrix was caused by alteration of the primary source of CO2 and H2O in mortar over time, particularly by recrystallisation of calcite with porewater, evaporated or re-condensed water, and CO2 from various sources of atmospheric and biogenic origin. Human influence (surface treatment) and biological growth (e.g. fungus) are major exogenic processes which may alter δ18O and δ13C in lime mortar.