Mechanochemical destruction of pentachloronitrobenzene with reactive iron powder

Abstract

Pentachloronitrobenzene (PCNB) has been identified as a potential persistent organic pollutant, and received concerns from many countries for regulation due to its impurities such as dioxins and furans. Considering the need for its disposal, the mechanochemical destruction approach was investigated for the applicability. PCNB was co-ground with reactive iron powder in a high energy planetary ball mill at room temperature. PCNB was found to be destructed finally, and the Dioxins and coplanar-PCBs concentrations in PCNB had been degraded from 1146 ng-TEQ/kg to 0.04 ng-TEQ/kg finally. Pentachloroaniline (PCA), 2,3,5,6-tetrachloroaniline (2,3,5,6-TeCBA) and 3,4,5,6-tetrachloroaniline (3,4,5,6-TeCBA) were detected as intermediates during the ball milling process and were destructed completely after 8 h milling. The amount of water soluble chlorides (Cl −) reached 95.8% of the theoretical amount of chlorine in original PCNB sample after 12 h ball milling. The solvent acetone might play a role as the main hydrogen donor, which gives rise to the amination reaction of nitro-group. Metastable structures with high molecular were proposed to be formed during the ball milling process as intermediates. Carbonization was confirmed by Raman spectrum as the final degradation product of PCNB.