  Anionic surfactants based on fatty acids are usually used to modify the
particle surface properties of CaCO$_3$ with the aim to enhance its dispersion
and compatibility with polymer matrices. In this study sodium oleate was used
for the preparation of ultra-hydrophobic CaCO$_3$ nanoparticles using a wet
carbonation route. The effect of sodium oleate on the characteristics, particle
size, morphology, surface potential, thermal decomposition and hydrophobicity
of CaCO$_3$, was investigated using X-ray diffraction (XRD), Fourier transform
infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Zeta
potential, thermogravimetric analysis (TGA) and water contact angle measurement
(WCA). The results showed that the addition of 2 wt% sodium oleate helps in
reducing the particle size from 2 {\mu}m length scalenohedral particles to 45
nm rhombohedral particles and modifying of the hydrophobic property of
CaCO$_3$.
