Hydrolysis of titanic acid in hydrochloric acid solution for synthesis of tio2 powder with controlled particle size: processes, morphology, and kinetics study

A method for producing pure titanium dioxide with controlled particle size and morphology has been developed. The TiO2 powder produced by this method can be used as the starting material to produce pure Ti metal powder. In this method, the upgraded Ti-slag (UGS) is used as the starting material. Upgraded Ti-slag is first roasted with NaOH to produce sodium titanate. The roasted product is washed by water to remove alkaline soluble impurities like Si and Al. The titanate is then dissolved into HCl solution and filtered to prepare the solution for hydrolysis of titanic acid. Hydrolysis of titanic acid is performed at different temperatures with varied free acid concentration and equivalent TiO2 concentration. The titanic acid is then calcined to remove combined water to produce TiO 2 powder. The particle size and morphology of the titanic acid particles produced by this method depend strongly on factors including temperature, free acid concentration, equivalent TiO2 concentration, and agitation. To optimize the parameters of the hydrolysis process, a systematic parametric study was conducted. TiO2 powders with different morphology and particle size were obtained. The desired morphology of TiO2 powder is determined to be around 30µm, with a round shape and smooth surface. Porosity was found on the surface of TiO2 particles after calcination. The dependence of particle size and morphology of solid titanic acid particles on those process parameters was studied. The effect of the process parameters on the kinetics of the hydrolysis process were also studied. The mechanisms of nucleation and growth of titanic acid particles during hydrolysis was discussed.