Abstract
Copper oxide (CuO) and cerium oxide (CeO2) of various concentrations have been prepared through an ultrasonically assisted dispersion of CuO and CeO2 nanoparticles (NPs) in which water and nanofluids (NFs) were formulated. The morphological properties of the CuO and CeO2 NPs are reported. Few of the physicochemical properties that can influence the photocatalytic activities of the NFs are evaluated, such as viscosity, activation energy, density, thermal conductivity, electrical conductivity, alternating current (AC) conductivity, pH, stability, refractive index and optical band gap of the CuO and CeO2 NFs. Viscosity studies have been made at four different temperatures (303 K, 308 K, 313 K and 318 K) and the activation energy is calculated and compared between the CuO and CeO2 NFs. The thermal conductivity of the two NFs is calculated and compared. Electrical conductivity is measured for CuO and CeO2 NFs using an impedance analyzer at different frequencies at 303 K. The dielectric constant and AC conductivity were studied. The electrical conductivity and pH of the prepared NFs are measured and the results are compared. The stability of the NFs is determined from Zeta potential values obtained from dynamic light scattering measurements. UV-Visible diffuse reflectance measurements were used to deduce the optical bandgap of the respective metal oxide NPs in the NFs. The photocatalytic efficiencies of the CuO NFs and CeO2 NFs were evaluated using methylene blue (MB) as the model dye. The rate constant for the photodegradation of MB was higher for CuO NF as compared CeO2 NF and also higher than simple NPs-based photocatalysts. A plausible explanation for the role of NFs over the simple NPs-based photocatalytic solution is presented.
Highlights
A Comparative Evaluation of PhysicochemicalProperties and Photocatalytic Efficiencies of Cerium Oxide and Copper Oxide Nanofluids
The ever-increasing demand for developing strategies towards utilization of waste heat and management of high heat fluxes poses a significant bottleneck and provides the drive to searchCatalysts 2020, 10, 34; doi:10.3390/catal10010034 www.mdpi.com/journal/catalystsCatalysts 2020, 10, 34 for advanced heat transfer fluids
With advances in nanomaterial synthesis and with the proven fact that nanomaterials are known to enhance the thermophysical properties of fluids, a great number of NFs are developed as next-generation heat transfer fluids. and studies on effective thermal conductivities have been extended by many researchers [3,4,5,6,7]
Summary
Properties and Photocatalytic Efficiencies of Cerium Oxide and Copper Oxide Nanofluids. 1 , Vaithinathan Karthikeyan 3 , Vellaisamy A. L. Roy 4 , Anantha-Iyengar Gopalan 5 , Gopalan Saianand 6 , Wha-Jung Kim 5, * and Venkatramanan Kannan 1, *. Received: 6 December 2019; Accepted: 23 December 2019; Published: 26 December 2019
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