Enhanced dechlorination of 2,4-dichlorophenol by Pd/FeFe3O4 nanocomposites

► Pd/FeFe3O4 nanocomposites showed higher dechlorination efficiency. ► nFe3O4 was favored to recycle the nanocomposites with an external magnetic field. ► Sulfate poisoned palladium catalyst and inhibited the dechlorination. ► Cu2+, Ni2+ and Fe2+ promoted corrosion of nZVI and enhanced the dechlorination.