Submerged-arc welding slags: Characterization and leaching strategies for the removal of aluminum and titanium

In the present study, submerged-arc welding slags were characterized by applying a variety of methods, including X-ray fluorescence, X-ray diffraction, particle size, Raman spectroscopy, and scanning electron microscope with energy dispersive X-ray analysis. The content of Al proved to be quite similar within neutral and acid slags (10-14%), while that of Ti proved to be much higher in acid slags (approximately 10%) than in neutral slags (<1%). The presence of spinel structures associated with Al species could also be identified in the analyzed samples. This characterization study was accompanied by leaching tests performed under changing operating conditions in an attempt to evaluate to what extent the Al and Ti bearing components could be removed from the slags. The leaching work involved three distinct strategies: (i) NaOH leaching followed by H2SO4 leaching, (ii) acid leaching (HCl and H2SO4) using oxidizing/reducing agents, and (iii) slag calcination followed by H2SO4 leaching. In the best result, 80% of Al was extracted in one single leaching stage after calcination of the acid slag with NaCl + C at 900 degrees C. By contrast, the removal of Ti proved to be unsatisfactory. (C) 2012 Elsevier B.V. All rights reserved.