Fabrication of Pd NCs@GO(Fe3O4) as a magnetically separable and reusable catalyst for catalytic conversion of three types of pollutants from water resources

Abstract

In recent years, organic contaminants have become so detrimental to both the environment and human health that it is imperative to remove them from water. In this study, Magnetic Pd NCs@GO(Fe3O4) composite microspheres were successfully synthesized, which graphene oxide (GO) was encapsulated with Fe3O4 microspheres serving as the core, and subsequently, palladium nanocubes were deposited in situ onto the GO layer. The samples were thoroughly characterized using XRD, TEM, EDS, FT-IR, Raman, XPS, UV-Vis, VSM, DLS NMR and Zeta techniques. At room temperature, the presence of KBH4 effectively reduced 4-nitrophenol (4-NP), 4-nitroaniline (4-NA), and Congo red (CR). Specifically, 4-NP was fully reduced in three minutes with a TOF of up to 464 min⁻¹; 4-NA was completely reduced in seven minutes, achieving a TOF of up to 280 min⁻¹; And CR was fully reduced in eight minutes, yielding a high TOF of 74.86 min⁻¹. Furthermore, the magnetic Pd NCs@GO(Fe3O4) composite microsphere catalyst demonstrated excellent recovery and high conversion rates after five consecutive cycles, maintaining a minimum value of over 90 %. The reaction rate constants for the catalysts were found to be K4-NP = 1.12 min⁻¹, K4-NA = 0.606 min⁻¹, and KCR = 0.394 min⁻¹, respectively. The underlying catalytic mechanism was also discussed. Overall, this study presents a rapid and environmentally friendly method for synthesizing magnetic noble metal nanocatalysts for the efficient reduction of Congo red (CR), 4-nitroaniline (4-NA), and 4-nitrophenol (4-NP).