Beneficiation of titania by sulfuric acid pressure leaching of Panzhihua ilmenite

• This leaching was conducted without a high temperature pretreatment of ilmenite.
• The waste sulfuric acid discharged from the sulfate TiO2 process can be used to upgrade Panzhihua ilmenite.
• Formation of the adsorbed electric triple layer may be responsible for the agglomeration of primary particles.

The beneficiation of titania (TiO2) by sulfuric acid (H2SO4) pressure leaching of Panzhihua ilmenite was investigated. The reaction temperature, H2SO4 concentration, and concentration of ferrous ions (Fe2 +) had significant effects on the enrichment of TiO2. With increasing reaction temperatures, the dissolution of iron from ilmenite was enhanced, while the titanium loss was reduced. Increasing the concentration of Fe2 + had an adverse effect on the beneficiation of TiO2. In contrast, the dissolution of iron from ilmenite was accelerated by increasing concentrations of H2SO4, up to 40 wt.% H2SO4. SEM analyses of the leach residues under different leaching conditions indicated that severe agglomeration occurred among the primary hydrolysate particles at high concentrations of H2SO4 or with the addition of ferrous sulfate (FeSO4). Furthermore, a compact layer was formed on the surface of unreacted ilmenite particles, thus retarding the ilmenite leaching. The agglomeration might have resulted from the adsorption of H2SO4 on the primary particle surfaces, as revealed by energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). The optimal conditions for the beneficiation process were as follows: H2SO4 concentration 40 wt.%, acid/ore mass ratio 2:1, reaction temperature 150 °C, and reaction time 3 h. Thus, a Ti-rich material with a TiO2 content of ~ 85 wt.% was obtained. Moreover, the results demonstrated the technical feasibility of upgrading Panzhihua ilmenite in 40 wt.% sulfuric acid obtained by concentrating the diluted acid waste discharged from the sulfate TiO2 process.