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Abstract: Pd/Fe bimetallic nanoparticles were synthesized for treatment of 2,4-dichlorophenol (2,4-DCP) in the presence of humic acid (HA), in order to understand their applicability for in situ remediation of groundwater. In this case, 2,4-DCP was catalytically dechlorinated to form the final products – phenol (P) via two intermediates, namely o-chlorophenol (o-CP) and p-chlorophenol (p-CP). We demonstrated that the carbon mass balances during the dechlorination were in the range of 82–91%, and other carbons were absorbed on the surface of Pd/Fe bimetallic nanoparticles. Our results suggest the dechlorination reaction of 2,4-DCP by Pd/Fe bimetallic nanoparticles in the presence of HA followed pseudo-first-order kinetics. HA competed for reaction sites on the Pd/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. Efficiencies of dechlorination and phenol formations increased significantly as the Pd content increased from 0.10wt.%, 0.15wt.% to 0.20wt.%, the removal percentage of 2,4-DCP increased from 70.4%, 98.4% to 99.4% within 300min, respectively, the nitrate (NO3 −) content in water also has a significant impact on 2,4-DCP dechlorination efficiency. Our results show that no other intermediates were generated besides Cl−, o-CP, p-CP and phenol during the catalytic dechlorination of 2,4-DCP. [ABSTRACT FROM AUTHOR]

The dechlorination of 2,4-dichlorophenol (2,4-DCP) by Ni–Fe nanoparticles in the presence of humic acid (HA) was investigated to understand the feasibility of using Ni–Fe for the in situ remediation of contaminated groundwater. 2,4-DCP was first adsorbed by Ni–Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). However, the introduction of HA decreased the removal percentage of 2,4-DCP, as a result, the phenol production rates dropped from 86% (in the absence of HA) to 29% within 2h. Our data suggested that the dechlorination rate was dependent on a number of factors including Ni–Fe availability, Ni loading percentage over Fe, temperature, pH, and HA concentration. In particular, the removal percentage of 2,4-DCP was determined to be 100, 99, 95, 84 and 69%, for HA concentrations of 0, 5, 10, 30 and 40mgL−1, respectively. The kinetic calculations for the dechlorination of 2,4-DCP indicated that k values for 2,4-DCP dechlorination dropped from 0.14, 0.051, 0.039, 0.021 to 0.011min−1 with increasing concentrations of HA from 0, 5, 10, 30 to 40mgL−1. [Copyright &y& Elsevier]