Effects of Mg/Al/Fe and Modified Coal Gasification Slag on Hydrothermal Hydrolysis of TiOSO4

Abstract

Hydrothermal hydrolysis of TiOSO4 is a critical step in recovering titanium from sulfuric-acid leachates derived from titanium-bearing blast furnace slag (TBFS). This research examined the effects of Mg, Al, and Fe impurities on TiOSO4 hydrolysis and assessed modified coal gasification slag (m-CGS) as a substrate for TiO2 deposition. Mg, Al, and Fe sulfates suppressed Ti hydrolysis but yielded smaller, more highly dispersed metatitanic acid particles; at comparable hydrolysis ratios, the mean particle size decreased from 305 to 143 nm. Thermodynamic calculations indicated that the additional sulfate reduced the [TiO2+][OH−]2 concentration product and the theoretical hydrolysis ratio. In contrast, m-CGS accelerated hydrolysis, particularly at lower temperatures. The lower Avrami exponents observed upon the addition of m-CGS indicated an increased contribution of heterogeneous particle growth. Particle size distribution analysis and TEM-EDS confirmed Ti deposition on the m-CGS surfaces. These results support direct TiO2 deposition from impurity-bearing TiOSO4 solutions as a route to the integrated utilization of TBFS and CGS.