Process and composition for the chemical treatment of soil or waste material contaminated by chromium compounds

摘要

The known chemical treatment processes have the disadvantage that, from the insoluble chromium(III) hydroxide formed in the soil, at pHs greater than 9.2, soluble chromium compounds in the form of hexahydrochromates can form which are toxic and cause considerable environmental pollution. Starting from this, it was the object of the invention to create a process and provide a composition which ensure stable long-term immobilisation of the chromium(III) hydroxides. As a solution it is proposed that a reaction product comprising at least 35% by weight of soluble iron(II) salt, 20 to 60% by weight of metallic iron, 2 to 4% by weight of elemental sulphur and 1 to 3% by weight of alkali metal halide and/or alkaline earth metal halide is introduced into a soil or waste material having a moisture content of at least 10% H2O, in an amount of 5 to 30% by weight, based on 100% by weight of soil or waste material as dry matter, and that the soil or the waste material is adjusted to a pH of about 7 and a final moisture content of at least 35% by weight of H2O, and is then mechanically compressed in a manner known per se.