Preparation And Performance Study Of Illite/TiO₂Composite Pigment By Liquid Deposition

The optical properties of TiO2are excellent, so it is named of the best white pigment.However, its complicated manufacturing technique, high cost, and environmentalpollution restrict its development. Taking illite as substrate, the illite/TiO2compositepigment was prepared, which extended the application of TiO2and solved the contractionbetween supply and demand.In this paper, the elemental composite, crystal structure, morphology, whiteness, andparticle size of five kinds of ores (dolomite, barite, sepiolite, chlorite, and illite) werecomprehensively analysized, the illite was taken as substrate. Taking NH3H2O asprecipator, the TiO2-coated illite composite pigment was prepared via hydrolysis ofTi(SO4)2on the surface of illite. Some factors that influence the coating processes of TiO2were investigated in single-factor tests, and the whiteness, oil absorption value, andlightening power of coating products were tested, in accordance with this method, theoptimal coating and calcination conditions were obtained. X-ray diffraction analysis,scanning electron microscopy, energy-dispersive X-ray spectroscopy, zeta potentialanalysis, and X-ray photoelectron spectroscopy were performed to characterize the crystalstructure, morphology, surface element composition, surface electrokinetic behavior, andchemical environment of the elements, respectively. In addition, the coating mechanismwas studied based on experiment. Density functional theory calculations of the energeticstability and electronic structure of illite substrate and TiO2-coated illite were used toanalyze the chemical activity and bonding position between the anatase film and the illiteparticle.The results show the composite pigments reach a whiteness of95.73%, an oilabsorption value of33.82g/100g, and a hiding power of97.55%, with the optimumcoating and calcination parameters of hydrolysis temperature of90℃, pH value of1.5,titanium sulfate dosage of25g/100g illite, aging time of3h, calcination temperature of900℃, calcination time of2h. The experimental data of XRD, XRD refinement, zetapotential analysis, SEM and EDS demonstrate that the illite is stability at high temperature, Firstly, the TiO2is absorbed onto the surface of illite by electrostatic attraction and thecoating layer is uniform anatase in which mass fraction is21.4%. From the results of XPSand theoretical calculation it can ben concluded that calcined illite is more suitable formetatitanic acid coating, in addition, the powerful chemical interaction between theanatase film and the illite substrate mainly relies on Al from the Si layer of illite and Ofrom the anatase.