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 (AlO and SiO) modified with a plasmonic metal (silver, Ag) nanoparticles (NPs)-based nanofluid (NF) formulation for environmental remediation purposes. Firstly, we prepared the AlO and SiO NFs of different concentrations (0.2 to 2.0 weight %) by ultrasonic-assisted dispersion of AlO and SiO 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 AlO and SiO NPs were then catalytically activated by loading silver NPs to obtain AlO/SiO@Ag composite NPs. The catalytic reduction of 4-nitrophenol (4-NP) with AlO/SiO@Ag based NFs was followed. The catalytic efficiency of AlO@Ag NF and SiO@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 AlO@Ag NF (92.9 × 10 s) as compared to the SiO@Ag NF (29.3 × 10 s). Importantly, the enhanced catalytic efficiency of 2% weight AlO@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.