At present, more than 90% of the world's titanium ore is used to make titanium dioxide. And the total production of titanium dioxide shows an increasing trend year by year, which will inevitably produce a lot of wastewater and solid waste. However, these wastewater and solid waste contain a lot of available resources, if not recovered, it will not only cause environmental pollution, but also cause a great waste of resources. For example, in the process of producing titanium dioxide by sulfuric acid method, each ton product produced 8-10 tons of acidic wastewater, which contains 20-25% sulfuric acid, 3-5% iron, 0.3-0.6% titanium, and a certain amount of chromium, vanadium, scandium and so on. The resource utilization of these wastes can not only reduce the production cost of enterprises, increase additional benefits, but also help to reduce environmental pollution and save environmental resources.

Preparation of LiFePO4 From Titanium Dioxide Slag

To further reduce the production cost of LiFePO4 cathode material and promote the resource utilization of titanium dioxide slag solid waste. Guo et al. taken titanium dioxide slag rich in iron(II) sulfate as raw material to prepare LiFePO4. The results showed that the purity of iron(II) sulfate in the purified titanium dioxide slag could reach 99.97% by using a composite precipitant formulated with ammonium bifluoride and reduced iron powder. And the prepared LiFePO4 by the purified iron(II) sulfate was similar to the electrochemical performance of LiFePO4 prepared from battery-grade iron(II) sulfate [1]. These results indicate that the preparation of LiFePO4 from titanium dioxide slag purification may become a new way to solve the problem of solid waste utilization of titanium dioxide slag.

Fig.1. LiFePO4 preparation process flowchart (FS-T and FS-B refer to high-purity iron(II) sulfate from titanium dioxide slag and commercially available battery-grade iron(II) sulfate, respectively).

Recovery of Ti, Fe and Mn From Titanium Dioxide Wastewater

Liu et al. utilized a collaborative utilization process of titanium dioxide wastewater and pyrolusite to recover both Ti, Fe from the wastewater. The recovery of titanium reached 95%. After the extraction of titanium, a portion of ferrous sulfate heptahydrate was separated using the freezing crystallization method and the morphology of the ferrous sulfate heptahydrate was better and the loss of titanium was reduced. Then, the pyrolusite was leached with a leaching efficiency of 93% for manganese. Compared to traditional method for treating acid wastewater and pyrolusite, this process achieves the recovery of valuable metals and the utilization of sulfuric acid at the same time [2].

Fig.2. Synergistic utilization process of titanium dioxide acidic wastewater and pyrolusite.

Recovery of Vanadium From Titanium Dioxide Wastewater

Zhen et al. used sodium chloride and di (2-ethylhexyl) phosphate(P2O4) synergistic extraction to recover vanadium from acidic wastewater of titanium dioxide. The results showed that under the conditions of initial pH value of 2.3, NaCl addition of 75g/L, oscillation rate of 220 r/min and time of 5min, the unipolar extraction rate of vanadium could reach a good result of 92.38% [3].