In-situ synthesis of ultra-small Ni nanoparticles anchored on palygorskite for efficient reduction of 4-nitrophenol

Abstract

4-nitrophenol (4-NP) is an environmental pollutant with high toxicity and strong stability, which is difficult to degrade naturally. Reduction of 4-NP to 4-aminophenol (4-AP), an important chemical intermediate, is an economical and green method. The reduction process demands high-efficient catalysts, and ultra-small metal nanoparticles (NPs) are the great potential ones. Herein, ultra-small and monodisperse Ni nanoparticles (NiNPs) (5.1 nm) were successfully anchored on palygorskite (Pal), using nickel silicate (NiSi) as a welding-like joint, and the ultimate catalysts were NiNPs/NiSi/Pal nanocomposites. The NiNPs were in-situ reduced from the NiSi precursor, which was previously and in-situ grown on Pal. The size of NiNPs was adjustable by the NiSi precursor, while the size of the NiSi precursor was controlled by the etching degree cations of the crystal structure of Pal. The etching degree affected the amounts of octahedral released from Pal, and thus affected the amounts of freshly exposed SiO- bonds, which could capture Ni2+ ions, form SiONi bonds and promote the generation of NiSi. The as-prepared NiNPs/NiSi/Pal nanocomposites exhibited excellent catalytic activity for the reduction of 4-NP (52.67 × 10-3 s−1), and satisfactory recyclability. The excellent catalytic performance is mainly attributed to the full exposure of ultra-small NiNPs, which provides enough active sites and enables fast electron transfer between the catalysts and substrates. It is expected that the work could develop a new avenue for designation of ultra-small and monodisperse non-precious metal NPs, and contribute to the treatment of waste water containing 4-NP.