CAPACITY OF CHROME IONS FIXATION BY BLAST FURNACE SLAG

摘要

Storage of industrial wastes in landfills often generates leachates with high heavy metal concentrations. Conventional solidification/stabilisation process using ordinary Portland cement shows a lack of mineralogical control on some elements, especially on Cr ions. Addition of blast furnace slag seems to allow fixation of Cr ions, in particular Cr~(6+). The aim of this study was to compare and especially quantify the effect of blast furnace slag and Type 1 ordinary Portland cement in the presence of solutions rich in Cr ions. Results show that the blast furnace slag exerts a solubility control on Cr and Mo concentrations and that there is no ionic competition between these two ions. Blast furnace slag completely fixes Cr~(6+) present at a concentration of 1000 ppm in a sample with a slag to solution ratio of 1:5. X-ray diffraction results on this sample reveal the presence of calcite, merwinite and two calcic chromium oxides (Ca(CrO_2)_2 and CaCrO_3). These oxides were not detected by scanning electron microscope analysis, which confirmed the presence of calcite and highlighted the presence of calcium silicate hydrates and hydrated calcium aluminate phases.