Facile Use of Silver Nanoparticles-Loaded Alumina/Silica in Nanofluid Formulations for Enhanced Catalytic Performance toward 4-Nitrophenol Reduction

The introduction of toxic chemicals into the environment can result in water pollution leading to the degradation of biodiversity as well as human health. This study presents a new approach of using metal oxides (Al 2 O 3 and SiO 2 ) modified with a plasmonic metal (silver, Ag) nanoparticles (NPs)-based nanofluid (NF) formulation for environmental remediation purposes. Firstly, we prepared the Al 2 O 3 and SiO 2 NFs of different concentrations (0.2 to 2.0 weight %) by ultrasonic-assisted dispersion of Al 2 O 3 and SiO 2 NPs with water as the base fluid. The thermo-physical (viscosity, activation energy, and thermal conductivity), electrical (AC conductivity and dielectric constant) and physical (ultrasonic velocity, density, refractive index) and stability characteristics were comparatively evaluated. The Al 2 O 3 and SiO 2 NPs were then catalytically activated by loading silver NPs to obtain Al 2 O 3 /SiO 2 @Ag composite NPs. The catalytic reduction of 4-nitrophenol (4-NP) with Al 2 O 3 /SiO 2 @Ag based NFs was followed. The catalytic efficiency of Al 2 O 3 @Ag NF and SiO 2 @Ag NF, for the 4-NP catalysis, is compared. Based on the catalytic rate constant evaluation, the catalytic reduction efficiency for 4-NP is found to be superior for 2% weight Al 2 O 3 @Ag NF (92.9 × 10 −3 s −1 ) as compared to the SiO 2 @Ag NF (29.3 × 10 −3 s −1 ). Importantly, the enhanced catalytic efficiency of 2% weight Al 2 O 3 @Ag NF for 4-NP removal is much higher than other metal NPs based catalysts reported in the literature, signifying the importance of NF formulation-based catalysis.