Process for decreasing the toxicity of Cr(VI)-contaminated solid and liquid waste materials

摘要

The invention relates to a process for decreasing the hazardous nature of Cr(VI)-contaminated solid and liquid waste materials, in particular soils, building rubble and waste waters. The object underlying the present invention is to indicate a process by which the toxicity of Cr(VI)-contaminated solid or liquid waste materials can be decreased to the extent that hazard-free disposal is possible. According to the invention the contaminated material is subjected to a reductive treatment under acidic conditions; the Cr(VI) compounds are selectively and completely reduced under these conditions to Cr(III) compounds. It is advantageous to convert the Cr(III) compounds formed in the chemical treatment into water-insoluble compounds and thus to immobilise them. By means of the selection of optimum process conditions, in particular the pH and if appropriate the addition of metal cations, preferably iron, the Cr(III) compounds formed can be preserved and fixed and are highly resistant to chemical attack. All reactants used and the reaction products formed are for the most part environmentally compatible so that the chemical treatment products can be supplied for disposal in accordance with the legal stipulations.