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

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.