Experimental investigation of water self-diffusion coefficient and tracer diffusion coefficient of tert-butanol in water-based silica nanofluids

• Mass diffusivity in silica/water nanofluids is measured.
• No enhancement in mass diffusivity is observed in the presence of nanoparticles.
• Temperature influences self-diffusion of nanofluids similar to the base liquid.

Water self-diffusion coefficient and tracer diffusion coefficient of tert-butanol in water-based silica nanofluids were measured by using pulsed field gradient nuclear magnetic resonance (PFG-NMR) method for silica nanoparticle volume fractions ranged from 0.005% to 1% at three different temperatures (15, 25 and 35 °C). In this work, formation of dye–nanoparticle complexes was minimized and undesirable primary advection effects induced by solute injection were also eliminated. Insignificant enhancement (mostly less than 10% increase) in both water self-diffusion coefficient and tracer diffusion coefficient of tert-butanol in nanofluids was observed. These results indicate that probably Brownian motion of nanoparticles and induced micro-convection tend to enhance mass transfer but the obstruction effect of solid nanoparticles limits this enhancement by reducing the free volume face to diffusion path of molecules.