For the purpose of increasing the dispersibility and thermal conductivity of fluid containing nanoparticles, raw multi-walled carbon nanotubes (MWCNTs) were treated by strong acids. The purified structures were dispersed into aqueous solution by using wet grinding conditions at various rotation speeds (300-600 rpm) merged with ultrasonication. The particle size analyzer reveals that the agglomerated size of ground particles at rotation speed of 300 rpm was 39.811 mu m. Nevertheless, the agglomerated size of particles significantly decreased to 11.482 mu m after grinding at rotation speed of 600 rpm. The maximum absorbance (4.0 abs at wavelength of 300 nm) and highest thermal conductivity (0.6074 W/mk at 30 degrees C) of the suspension corresponds to the grinding speed of 600 rpm assisted by ultrasonication dispersion. From the overall results, grinding method with high rotation speed plays can be significantly increased both the dispersibility and thermal conductivity of MWCNTs in aqueous solution. (c) 2012 Elsevier B.V. All rights reserved.