Dechlorination of 2,4-dichlorophenol by nanoscale magnetic Pd/Fe particles: Effects of pH, temperature, common dissolved ions and humic acid

• Pd/Fe-Fe3O4 nanocomposites showed synergy effects on 2,4-DCP dechlorination.
• Weak acidic condition and high temperature favored 2,4-DCP dechlorination.
• Common dissolved anions and cations were found to affect 2,4-DCP dechlorination.
• HA adsorbed on nFe3O4-Pd/Fe would inhibit 2,4-DCP dechlorination.
• High stabilities and durable reactivity were observed in consecutive experiments.

In this study, magnetic Pd/Fe nanoparticles were synthesized using nanoscale Fe3O4 (nFe3O4) and nanoscale zero-valent iron (nZVI) to significantly enhanced 2,4-DCP dechlorination. nFe3O4 was found to restrain the formation of passivated layer on nZVI surface and promoted the electron transfer. Earlier, only 35.8% 2,4-DCP (Cinitial = 20 mg L−1) was removed by 3.0 g L−1 Pd/Fe nanoparticles, whereas it remarkably increased to 76.4% by magnetic nanocomposites (2.0 g L−1nFe3O4 and 3.0 g L−1 Pd/Fe). A satisfactory long-term stability of nFe3O4-Pd/Fe was exhibited and the 2,4-DCP removal efficiency reached to 100%, 100%, 93.5%, 93.0%, and 90.1% in five consecutive cycles, respectively. Moreover, the nanocomposites were easily separated from the solution after reaction and that reduced environment related risks of nanoparticles. Weak acidic condition was considered feasible for 2,4-DCP dechlorination. Negative co-precipitation occurred on nFe3O4-Pd/Fe surface in the presence of common dissolved anions (such as Cl−, PO43-, and HCO3-) and humic acid (HA). The 2,4-DCP dechlorination was notably accelerated by dissolved metallic ions (Fe2+, Cu2+, and Ni2+), and 2,4-DCP was completely removed in 5 h reaction time. The application of nFe3O4-Pd/Fe nanocomposites could be highly effective for an in situ pollutants remediation measures.

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