Abstract
The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.
Highlights
Titanium dioxide is an irreplaceable high-grade functional white pigment and widely used in coatings [1], rubber [2], papermaking [3], printing [4] and other chemical industries [5,6,7,8,9,10], due to its characteristics, stable chemical properties, good color covering capability, high tinting strength and dispersion, nontoxicity, and electronic properties
About 62.7% of global titanium dioxide is produced by chlorination process, and the other is produced by sulfuric acid process [15]
The titanium in vanadium titanomagnetite concentrate is enriched in Ti-bearing electric furnace slag (TEFS) containing high SiO2, Al2O3, CaO, and MgO, which cannot be the feedstock of chlorination process and sulfuric acid process
Summary
Titanium dioxide is an irreplaceable high-grade functional white pigment and widely used in coatings [1], rubber [2], papermaking [3], printing [4] and other chemical industries [5,6,7,8,9,10], due to its characteristics, stable chemical properties, good color covering capability, high tinting strength and dispersion, nontoxicity, and electronic properties. The titanium in vanadium titanomagnetite concentrate is enriched in Ti-bearing electric furnace slag (TEFS) containing high SiO2, Al2O3, CaO, and MgO, which cannot be the feedstock of chlorination process and sulfuric acid process. It is necessary to study the fluoride leaching mechanism and kinetics of titanium from TEFS under a normal pressure system, in order to reveal the key factors affecting the Ti leaching rate. It has important practical significance for increasing the leaching speed and realizing the industrialization. The findings will provide a Metals 2021, 11, 1176 technical basis for the preparation of titanium dioxide by fluorination method with TEFS and is of great significance for improving the utilization of titanium resources in the Panxi region of China
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