Abstract
Chromium oxide, Cr2O3, was solidified by heating with the mixture of Na2CO3, CaCO3 and SiO2. The leach test was appled to determine the environmental adequacy of the ternary system Na2O-CaO-SiO2 as chemical fixation agents for Crcontaining Sludge. In the present work the content of Cr2O3 was kept at 0.5 mol.% and the mixturs were heated at the temperatures from 800-1200°C for 2 hr. The pH's of the leaching mediums were 1.0, 6.0 and 10.5, respectively. By firing at 1000°C, the heated mass whose composition falled within 15-23 mol.% of Na2O, 0-9% of CaO and 72-81% of SiO2 gave the concentration of extracted Cr less than 2 ppm. At 1100°C such area was extended as 10-26% of Na2O, 0-12% of CaO and 71-86% of SiO2. Further elevation of the firing temperature, however, no longer broadened the compositional area of the solidified mass which gave low concentration of extracted Cr.
