From hexafluorotitanate waste to TiO2 powder: Characterization and evaluation of the influence of synthesis parameters by the experimental design method

Abstract

This paper was focused on the possible chemical synthesis routes to obtain titanium dioxide, TiO2, from hexafluorotitanate waste and it was aimed to identify the parameters affecting the formation of crystalline titanium dioxide, TiO2, phases (anatase or rutile). An experimental design method, inspired from the Taguchi approach, was used to assess the positive or negative impact of input factors on the formation of rutile and anatase, which were the output factors of interest. An experimental matrix was built up with coded values for each factor and coefficients were computed to point out a correlation between outputs and inputs. Particular attention was paid to the chemical compounds (decomplexing agents) added to precipitate TiO2 from hexafluorotitanates and to the dehydration temperature used to obtain TiO2 crystallized phases. The powders resulting from the syntheses were investigated by X-Ray diffraction analysis. Their chemical compositions were determined by Inductively Coupled Plasma Atomic Emission Spectroscopy. Data-matching revealed the best synthesis conditions in terms of crystallized TiO2 content, and this was confirmed by calculating the processing yields. The results showed that silica and calcium hydroxide were the most efficient decomplexing agents leading to the formation of anatase.