Synthesis, characterization, and determination of the catalytic roles of tungsten (VI) oxide-supported Pd (0) nanoparticles in the reduction of nitroaromatic pollutants

Abstract

One of the most important approaches for industrial and environmental catalytic applications is to develop a promising, simple, and effective method. Toxic organic pollutants in wastewater, such as nitroaromatic contaminants, have become a global issue, threatening aquatic life and obstructing essential elements required for the survival of living organisms. In this study, a palladium pre-catalyst supported on tungsten (VI) oxide (Pd2+/ WO3) was prepared with a 2 % metal loading using a simple and conventional wet impregnation method. The efficiency of this pre-catalyst was investigated for the reduction of nitroaromatic pollutants (2-nitrophenol (2 NP), 4-nitrophenol (4-NP), and 2,4-dinitrophenol (2,4-DNP)) into their corresponding aminophenol compounds in the presence of an excess amount of NaBH4 as the reducing agent. Characterization techniques such as ICPOES, XRD, SEM, SEM/EDX, TEM, and XPS analysis revealed that Pd (0) nanoparticles were well-dispersed on the WO3 support, with an average particle size of 2.2 +/- 0.1 nm. The catalytic activities of Pd (0) nanoparticles for the reduction of nitroaromatic pollutants to aminophenols in the presence of NaBH4 were determined in terms of initial TOF, calculated as 127.2 min(-1) for 2-NP, 109.4 min(-1) for 4-NP, and 353.1 min(-1) for 2,4-DNP. The results demonstrated that the Pd/WO3 nanocatalyst exhibited excellent catalytic efficiency and stability (>85 %) even after five catalytic cycles in the reduction of nitroaromatic pollutants. Considering both the simple preparation process and the effective catalytic reduction of nitroaromatic pollutants, this study presents a great opportunity for the practical application of the Pd/WO3 nanocatalyst in wastewater treatment.