| Titanium dioxide acidolysis slag is a kind of acidic residue produced in the acidolysis of titanium pigment production by sulfuric acid process. The slag contains a certain amount of titanium, being acidic and corrosive moreover. Stockpiling without treatment will inevitably cause the waste of resource and contamination of environment in the long-term. In order to extract valuable titanium in acidolysis slag, improve resource utilization, reduce the amount of slag accumulation, and eliminate risk of environmental pollution, washing-mechanical activation process was chosen to separate titanium from the acidolysis slag in this study. The acidolysis slag was treated with the following process:washed with water, conventional acid leaching, mechanical activating with stirred mill after water scrubbing, mechanical activating with roller mill after water scrubbing, which was aim to get optimal conditions of leaching titanium from titanium dioxide acidolysis residue with a method of mechanical activation. The main results are as follows:(1) 36.3% of titanium contained in the original titanium dioxide acidolysis slag is water-soluble titanium, which can be leached from acidolysis slag by a method of water scrubbing. The major influence factors for the washing were stirring speed and reaction time. The optimum conditions of water scrubbing were as follows:stirring speed was 400 r/min; ratio of liquid to solid was 2; the reaction time was 60 minutes, and the temperature was 30 ℃.(2) In the process of conventional acid leaching, the main influence factors on titanium leaching were sulfuric acid concentration and reaction time. The superior conditions of conventional acid leaching were as follows:sulfuric acid concentration was 20%; stirring speed was 400 r/min; ratio of liquid to solid was 2; the reaction time was 60 minutes, and the temperature was 30 ℃. Under the above conditions, the leaching rate of conventional method after washing was 12%, and the total titanium recovery of washing and conventional acid leaching was 43.9%.(3) When the slag was water-washed, in the next process of mechanical activating with stirred mill, sulfuric acid concentration and rotate speed were the main influence factors on activation effect., with conditions as follows: sulfuric acid concentration was 87.5%, the ratio of liquid to solid was 3, rotate speed was 600 r/min, reaction time was 120 minutes, and the ratio of grinding media to material was 24. Under the above conditions, the leaching rate of titanium in titanium dioxide acidolysis slag was 81%. When combining the water-washing process, the leaching rate of titanium was 87.9%.(4) Being water-washed, the titanium dioxide acidolysis slag was treated with mechanical activating with roller mill. The optimum leaching conditions of roller mill were as follows:ratio of liquid to solid was 3, reaction time was 120 minutes, rotating speed was 120 r/min, the ratio of grinding media to material was 40, sulfuric acid concentration was 85% and the material filling rate was 60%. Leaching rate of roller mill activation was 15.5%, and total recovery of titanium was 46.1%, when combining the water-washing process. Although the leaching rule of roller mill was generally similar with stirred mill, the leaching effect of roller mill was not so good compared with stirred mill.(5) After mechanical activation, particle size of acidolysis residue reduced from 2.2 μm to 1.2 μm, and the specific surface area increased from 4.65 m/g to 9.89 m/g. The surface of acidolysis slag after mechanical activation changed a lot, which further validate the mechanism of mineral leaching strengthened by mechanical activation:minerals got energy through mechanical activation, which resulted lattice deformation and defects of slag, increase of energy reserves of the reactants, leading increasing trend of spontaneous thermodynamics leaching reaction. Since pathway of reaction changed by the above way, the leaching process was strengthened. |
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