Factors influencing the dechlorination of 2,4-dichlorophenol by Ni-Fe nanoparticles in the presence of humic acid

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 2 h. 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 40 mg L−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 0.011 min−1 with increasing concentrations of HA from 0, 5, 10, 30 to 40 mg L−1.