Enhanced dechlorination of 2,4-dichlorophenol by Pd/Fe-Fe_3O_4 nanocomposites

摘要

The Pd/Fe-Fe_3O_4 nanocomposites showed higher dechlorination efficiency of 2,4-dichlorophenol (2,4-DCP) rather than bare Pd/Fe nanoparticles in the batch dechlorination experiments. nFe_3O_4 provided a convenient way to recycle the nanocomposites with an external magnetic field and significantly enhanced 2,4-DCP dechlorination. 2.0gL~(-1) nFe_3O_4 was the optimal dosage in the presence of 3gL~(-1) Pd/Fe nanoparticles in our system, removing 76.4% 2,4-DCP within 5 h in the aqueous environment. This was much higher than bare Pd/Fe nanoparticles (35.8%), 1.0gL~(-1) nFe_3O_4 (58.0%) and 2.5gL~(-1) nFe_3O_4 (66.3%) employed under the same conditions. However, excessive nFe_3O_4 (3.0 g L~(-1)) partially overlapped on Pd/Fe nanoparticles to obstruct their contact with 2,4-DCP, and then 2,4-DCP removal efficiency was dropped to 7.4%. Efficiencies of dechlorination and phenol formations were increased significantly when the amount of Pd increased, whereas the highest 2,4-DCP removal efficiency was observed 98.2% at 0.20wt% Pd loading. Moreover, SO_42 would also inhibit the dechlorination while Cu~(2+), Ni~(2+) and Fe~(2+) enhanced the dechlorination of 2,4-DCP by Pd/Fe-Fe_3O_4 nanocomposites. The nanocomposites showed stable catalytic activity, fairly good mechanic stability, and promising to recycle during the process.