Synthesis of Calcium Aluminates from Non-Saline Aluminum Dross

The present work examines the synthesis of tricalcium aluminate (for use as a synthetic slag) from the non-saline dross produced in the manufacture of metallic aluminum in holding furnaces. Three types of input drosses were used with Al2O3 contents ranging from 58 to 82 wt %. Calcium aluminates were formed via the mechanical activation (reactive milling) of different mixtures of dross and calcium carbonate, sintering at 1300 degrees C. The variables affecting the process, especially the milling time and the Al2O3/CaO molar ratio, were studied. The final products were examined via X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The reactive milling time used was 5 h in a ball mill, for a ball/dross mass ratio of 6.5. For a molar relationship of 1:3 (Al2O3/CaO), sintered products with calcium aluminate contents of over 90% were obtained, in which tricalcium aluminate (C(3)A) was the majority compound (87%), followed by C(12)A(7) (5%).