ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Optimization of ferrous iron removal conditions by freezing from industrial titanyl sulfate solution for high purity TiO₂ preparation

Congxue Tian

School of Vanadium and Titanium, Panzhihua University, Panzhihua, People’s Republic of China

E-mail: tcx7311@163.com

Received: 5 October 2022  Accepted: 3 March 2023

Abstract:

Removing ferrous iron from the industrial titanyl sulfate (TiOSO₄) solution by freezing was an effective sustainable and green method to prepare high purity TiO₂. Using response surface methodology based on the Box–Behnken design approach, the freezing conditions were conducted to determine the effects of three independent freezing factors (freezing temperature, freezing time and concentration of TiO₂) on the Fe content. The freezing conditions had great effects on the Fe content of TiOSO₄ solution, affected the solubility of ferrous ion, the balance of ferrous ion precipitation and viscosity of the TiOSO₄ solution, and they also had synergistic effects, ultimately affected the purity of TiO₂. The response surface methodology had a good fitting result in the prediction model with correlation coefficient of 0.9999. The effects of the freezing conditions could be calculated from a second-order polynomial equation. The verification experiments confirmed that the Fe content could be achieved at the value of 9.56 g/L under the optimal conditions of freezing temperature 4.1 °C, freezing time 9.7 h, concentration of TiO₂ 172 g/L and the regression model was reliable. The purity of the prepared TiO₂ after iron removal and purification was higher than 99.9%.

Keywords: Ferrous ion removal; Titanyl sulfate; Freezing; High purity TiO2

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-023-02773-9

Chemical Papers 77 (8) 4235–4244 (2023)