Efficient destruction of hexachlorobenzene by calcium carbide through mechanochemical reaction in a planetary ball mill

Mechanochemical destruction (MCD) is a good alternative to traditional incineration for the destruction of persistent organic pollutants (POPs), like hexachlorobenzene (HCB), and the key is to find an efficient co-milling reagent. Toward this aim, HCB was milled with various reagents in a planetary ball mill at room temperature, and CaC2 was found to be the best one. HCB can be destroyed completely within 20 min at a mass ratio of CaC2/HCB = 0.9 and a rotation speed of 300 rpm. The ground samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results show that the destruction products are nonhazardous CaCl2 and carbon material with both crystalline and amorphous structures. On these bases, possible reaction pathways were proposed. Considering its excellent efficiency and safety, CaC2 may be the most feasible co-milling regent for MCD treatment of HCB. Further, the results are instructive for the destruction of other POPs. [Display omitted] •HCB is completely destroyed by CaC2 within 20 min via mechanochemical treatment.•CaC2 shows much higher reactivity than traditional alkaline co-milling regents.•HCB is converted to nonhazardous CaCl2 and carbon materials.•HCB is destroyed via nucleophilic substitutions of C-Cl by alkynyl in CaC2.