Enhanced removal of 2,4-dichlorophenol by Fe-Pd@ZIF-8 via adsorption and dechlorination
Recently, bimetallic Fe-Pd nanoparticles were integrated with metal organic frameworks (MOFs) to produce a new composite catalyst with significant potential for organic contaminant removal due to enhanced adsorption and reduction. Here, 85.9 % of 2,4-dichlorophenol (2,4-DCP) was successfully removed from aqueous solution within 120 min when using a zinc-based zeolitic imidazolate framework (ZIF-8) embedded with Fe-Pd (Fe-Pd@ZIF-8). In comparison only 77.4 and 48.3 % was removed when using ZIF-8 or Fe-Pd alone. Thus, to better understand the function of composite components (ZIF-8 and Fe-Pd) in the removal of 2,4-DCP, and the specific removal mechanism involved, Fe-Pd@ZIF-8 was characterized before and after exposure to 2,4-DCP. This comparison revealed that 2,4-DCP was adsorbed onto the surface of the composite during exposure. Moreover, while ZIF-8 maintained stability following the removal of 2,4-DCP, Fe 0 was partially oxidized and Pd functioned as a catalyst in the removal process. Furthermore, kinetic studies demonstrated that the initial adsorption of 2,4-DCP conformed to a pseudo-second-order model and the subsequent reduction conformed to a pseudo-first-order model, whereas isothermal adsorption best fit the Freundlich adsorption model. This observation suggested that removal mechanism of 2,4-DCP involved both adsorption and dechlorination. Finally, Fe-Pd@ZIF-8 was applied to practically remove 2,4-DCP from wastewater, showing a 74.4 % removal efficiency which indicated that the composite was a potential new nanomaterial for practically removing organic contaminants from wastewater.
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