Coupling the dechlorination of aqueous 4-CP with the mechanochemical destruction of solid PCNB using Fe-Ni-SiO2

► Toxic PCNB was completely destroyed by ball milling using Fe-Ni-SiO2. ► Nonhazardous destruction residue can effectively dechlorinate the 4-CP in water. ► Dechlorination mechanism involving reactions on 3 interfaces (Fe-Ni, Fe-C and Fe-C-Ni) was proposed.