Reduction of polychlorinated dibenzodioxins and dibenzofurans in contaminated muds by mechanically induced combustion reactions

Some selected results are reported from an ongoing study concerning mechanochemical dehalogenation reactions carried out under autopropagating high-temperature regimes. Our work shows that instantaneous burning reactions can be ignited in highly exothermic systems involving chloroorganics when subjected to intensive mechanical treatments. A reference trial using calcium hydride-hexachlorobenzene is first presented. No residual traces of the organohalide compound were found in the reacted powders or in the gaseous phase sampled from the headspace of the milling reactor. The solid products of the reaction were restricted to CaHCl and CaCl2 salts and graphite. Similar combustion-like phenomena were observed when contaminated mud samples were added to initial reactants. The contaminated mud was obtained from a waste site and contained traces of polychlorodibenzodioxins and polychlorodibenzofurans. It was observed that an effective chemical oven was created which caused the thermochemical breakdown of the hazardous compounds. A transformation yield greater than 99.6% was obtained with a decrease of the toxic equivalent concentration from 2492 to 0.788 mu g/kg. Unlike conventional incineration methods, the mechanically induced burst processes run under a strictly confined environment and controlled conditions.