Preparation of TiO₂-coated barite composite pigments by the hydrophobic aggregation method and their structure and...

We obtained hydrophobic barite (BaSO₄) and rutile titanium dioxide (TiO₂) particles (as raw materials) by organic surface modification. Subsequently, TiO₂-coated barite composite pigments were prepared via the hydrophobic aggregation of heterogeneous particles in a water medium. The pigment properties of the TiO₂-coated barite composite pigments were characterized and evaluated by determining their hiding power, oil absorption value and whiteness. The optical properties were determined by obtaining their UV-vis diffuse reflectance spectra and using the CIE-L*a*b* method. The morphology and bonding properties were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (IR). The results show the similarity between the composite pigment and pure rutile TiO₂: when the mass ratio of rutile TiO₂ in the composite pigment was 60%, the hiding power of the TiO₂-coated barite composite pigment was 90.81% of that of pure rutile TiO₂. Moreover, the surfaces of the barite particles were uniformly and firmly coated by TiO₂, with a hydrophobic association occurring between the hydrophobic carbon chains on the surfaces of barite and TiO₂ particles.