Preparation and characterization of calcium carbonate–titanium dioxide core–shell (CaCO3@TiO2) nanoparticles and application in the papermaking industry

• Titanium sulfate was chosen as Ti resource to prepare core–shell composite particles CaCO3@TiO2 via precipitation method.
• Compared with pure fiber paper, the whiteness of CaCO3@TiO2 incorporated paper sheet improved 3 percentage point.
• The retention rate values of both CaCO3@TiO2 and pure TiO2 are similar.
• CaCO3@TiO2 had a stronger absorption intensity than pure TiO2.

A novel and convenient method for preparing TiO2-coated CaCO3 composite particles was proposed and authenticated, meanwhile, the reaction mechanism was discussed. In this paper, carbonization was selected to prepare calcium carbonate, titanium sulfate was the titanium source, as it had a relatively low price compared to organic titanium sources, and urea was the precipitant to synthesize the target product with the direct precipitation method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis results proved that CaCO3 was covered by TiO2 particles. As verified by Field Emission Scanning Electron Microscopy (FESEM), a film of TiO2 had coated the surface of the CaCO3 core. The average nanoparticle size of the composite was found to be about 250 nm and well-dispersed. UV–visible absorption spectra in the solid phase study results showed that CaCO3@TiO2 possessed high ultraviolet absorption capacity. The whiteness of the CaCO3@TiO2 filler-containing paper sheet was 73.8%, which is similar to TiO2-incorporated paper (73.16%), and higher by about 3% than pure fiber paper (70.35%).

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