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 x 10(3) 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 x 10(3) mg Cl(-)/kg EAFD exceeding in all EAFD samples the MAL 17 x 10(3) mg/kg. This high concentration of Cl(-) is attributed to the scrap and it could be reduced only by modification of its composition.
Mitrakas
Manassis G
MG
Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Sikalidis
Constantinos A
CA
Karamanli
Theoktisti P
TP
D002712:Chlorides / Q000032:analysis; D006878:Hydroxides / Q000737:chemistry; D007220:Industrial Waste; D008669:Metallurgy; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D017942:Nitric Acid / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods*; D017693:Sodium Bicarbonate / Q000737:chemistry; D013232:Steel; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
D002712:Chlorides; D006878:Hydroxides; D007220:Industrial Waste; D019216:Metals, Heavy; D010756:Phosphoric Acids; D014874:Water Pollutants, Chemical; D013232:Steel; D017942:Nitric Acid; D017693:Sodium Bicarbonate; C031356:hydroxide ion; C030242:phosphoric acid