Sustainable simultaneous synthesis of titanium-bearing materials from silicon waste and TiO₂-bearing slag

Abstract

A sustainable simultaneous synthesis method of TiB2-Ti5Si3 mixtures is developed as an alternative recovery route of silicon waste from the photovoltaics industry. TiO2-CaO-B2O3 ternary was reduced by molten silicon at 1500 °C, producing TiB2 within 3 h and Ti5Si3 within 10 h. The lab-scale experiments were designed to study the reaction kinetics of the reaction. SiO2 diffusion rate controlling kinetic model was derived to describe the reaction process. The reaction rate constant was recommended to be ∼5 × 10-4 s-1. B2O3 content in slag was suggested to have an insignificant effect on the reaction rate constant, whereas more titanium and boron could be reduced by silicon with higher B2O3 content in slag. Stability of the reaction interface was simulated using phase field model. A decreased interfacial tension in B2O3-containing system was indicated to be the reason for emulsification of phases.