Preparation of functionalized Pd/Fe-Fe3O4@MWCNTs nanomaterials for aqueous 2,4-dichlorophenol removal: Interactions, influence factors, and kinetics.

Magnetic multi-walled carbon nanotubes (MWCNTs) were prepared to support Pd/Fe nanoparticles, inhibit the aggregation and passivation, and achieve magnetic separation to avoid the environmental risk of nanoparticles. Rapid adsorption of initial contaminant, steady dechlorination, and gradual desorption of final product was observed. The micromorphology, chemical structure, and components of the nanohybrids were comprehensively characterized by a series of analysis technologies, such as EDX, XRD, SEM, TEM, and XPS. The interactions between the nanohybrids compositions were discussed according to the characterization and experimental data. The whole insight of 2,4-dichlorophenol (2,4-DCP) adsorption- dechlorination-desorption was studied in detail, including the pathways, influence factors, dechlorination kinetics and selectivity. Weak acidity (pH=5.0 and 6.5) favored the 2,4-DCP removal. Satisfactory reactivity of the Pd/Fe-Fe3O4@MWCNTs nanohybrids was observed in five consecutive runs, and 99.2%, 89.6%, 92.1%, 99.8%, and 99.9% of 2,4-DCP was removed, respectively. Most of the final product (phenol) was steadily desorbed to the liquid phase, resulted in the re-exposure of active sites on the nanohybrids and maintained a longer activity.