<Original Papers>Up-grading of Titanium Slag by Acid Leaching Process

Acid leaching process was investigated for titanium slag to obtain the up-graded material which is available as substitute material for rutile. Dilute sulfuric acid solution of about 1 per cent was successfully used at 70 to 90℃ to eliminate sulfur as hydrogen sulfide. Considerable parts of iron, silicon and manganese were also extracted, and as the results, grade of titanium oxide increased by 3 to 5 per cent to reach more than 95 per cent. Slight oxidation of slag particles were found to retard the dissolution reaction of impurities considerably. Under the optimum condition, the acid treated slag contained less than 0.02 per cent sulfur, which may be enough available as the constituent of welding flux. The micro structure of slag was investigated with electron probe micro analyzer, and the composition of the following constituents was established : i) titanium oxide phase ; ii) metallic iron phase ; iii) sulfide phase composed of MnS and FeS ; and iv) silico-manganese titanate. In the acid leaching process, sulfide and metallic iron phases seemed to be dissolved easily. Based upon the available phase diagram, the behavior of sulfide and silicate during cooling process of molten slag was discussed. The applicability of magnetic separation process was also discussed based upon the experimental results