Experimental study of stabilization of sludge containing toxic metal by hydraulic binders

摘要

Heavy metals term implying a concept of toxicity, among these elements: vanadium, chromium, cobalt, nickel, copper, arsenic, selenium, cadmium, mercury, etc. In addition, stabilization is defined like the process which makes it possible to reduce the dangerous potential and lixiviability of a material (waste, ground, etc.) by converting these contaminants in less soluble forms, mobiles or toxics. The concept of stabilization is often associated with the concept of solidification; we always find the term stabilization/solidification (S/S). Solidification makes it possible to transform a material into one monolith solid having a good physical integrity and structurally homogeneous. Solidification inevitably does not imply chemical reaction between the waste and the agent of solidification: that can be a mechanical trapping of waste in the solid. In the same way for stabilization, who can only be one modification of environment (like a change of pH). The objective of our study is to find a solution with solid waste produced from shovels and cranes complex (Ain Smara Constantine, Algeria) (CPG) who are represented by great quantities of sludge charged mainly of trivalent chromium (after reduction of Cr(VI)). We tried to stabilize or solidify toxic metal by a hydraulic cement at the cement factory (Hamma Bouziane, Constantine, Algeria); the experiments which were carried out on the level of the complex (CPG) are: determination of the content of hexavalent chromium before and after treatment (liquid phase), and determination of the chromium quantity contained in produced sludge by fluorescence X-rays. On the level of the cement factory, we carried out the chemical analyses (determination of oxides...), with the mechanical tests and physics on pure cement, cement and sludge (container of chromium); and the mixture before cooking vintage "Cru" and sludge (charged of chromium). In addition, we tried to act upstream by adsorption of Cr (VI) before its reduction in Cr(III) to recover it while reducing thus quantity of produced sludge.