A process for producing synthetic rutile from Panzhihua titanium slag

• Process of upgrading Panzhihua titanium slag with high content of Fe, Mg, and Si to prepare synthetic rutile was successfully developed.
• Synthetic rutile and glass were generated by roasting with H3PO4.
• Ca and Mg, which are sensitive for the chloride process, were effectively removed by hydrochloric acid leaching.
• Synthetic rutile containing 95.34% TiO2 and 0.37% (MgO + CaO) was obtained.

Synthetic rutile was prepared by treating Panzhihua titanium slag with H3PO4 followed by leaching. To this end, the effects of oxidation temperature and H3PO4 dosage on the phase transformation of titanium slag were studied by XRD, while the microstructure and composition of the treated slag were characterized by SEM and EDAX. It was determined that roasting with H3PO4 promoted the transformation of titanium slag into rutile. Furthermore, hydrochloric acid leaching of treated titanium slag was investigated in terms of the effect of HCl concentration, and leaching temperature, time and liquid-to-solid mass ratio on leaching. The results show that Fe, Mg, Ca and Al can be effectively removed by leaching with 20 wt.% HCl at a liquid-to-solid ratio of 5:1 at 110 °C for 2 h. It was found that a NaOH leaching step is necessary to remove Si and P to improve the purity of synthetic rutile. Using this process, synthetic rutile containing 95.34% TiO2 and 0.37% (MgO + CaO) was obtained.