In the present study, 3 different Hellenic fly ashes were utilized for the precipitation of hexavalent chromium Cr (VI) and other heavy metals Cr(total), Cu, Ni, Pb, Zn and Cd from aqueous solutions. Each FA sample was separated into five (5) different fractions with a grain diameter range of: (0-25) (25-45) (45-90) (90-150) (>150) μm. The different FA grain fractions were evaluated in terms of their chemical composition, pH, loss on ignition (LOI) and CaOf (％). Batch adsorption experiments were carried out by adding 10g of each FA type and fraction in 50ml of Cr(total),-Cr(VI)-Cu-Ni-Pb-Zn-Cd aqueous solution (about 0.2g of each metal/1L of solution except Cd that was 0.02g.L-1 ) in glass tubes and then implementing mechanical stirring at 200rpm. The incubation period was set at 24h. The supernatant solution was filtered and subjected to spectroscopy using the 1,5-diphenylcarbohydrazide colorimetric method (at a wavelength of 540nm) to determine the remaining concentrations of Cr(VI) and to graphite furnace adsorption spectroscopy (GFAAS) and flame atomic adsorption spectroscopy (FAAS) to determine that of the rest heavy metals. The various fractions of the siliceous MFA were better at the precipitation of Cr (VI) but less capable of retaining Cu, Ni, Pb and Zn. It is verified, via this research study, that fly ashes can be more effective in the field of industrial wastewater remediation when separated into their fractions, as different groups of FA particles demonstrate different kinds of the desirable properties. It therefore depends on the nature of the pollutant-to-be retained, the optimum FA type (and fraction) to be selected.
Lignite fly ash particle size distribution Cr (VI) wastewater decontamination heavy metal removal
G. ITSKOS N. KOUKOUZAS S. ITSKOS CH. VASILATOS I. MEGREMI A. MOUTSATSOU
Institute for Solid Fuels Technology and Applications, Centre for Research and Technology Hellas, 35 Institute for Solid Fuels Technology and Applications, Centre for Research and Technology Hellas, 35 Department of Chemical Technology and the Environment, Steam Electric Station of Amynteon-Filotas, P Department of Economic Geology & Geochemistry, Faculty of Geology and Geoenvironment, National & Kap Laboratory of Inorganic and Analytical Chemistry, School of Chemical Engineering, National Technical