Lee YH  Kang HR  Jang YH  Lee SJ  Kim SS

Vol. 25,  No. 4, pp. 311-315, Dec.  2019
10.7464/ksct.2019.25.4.309

Slag S/L ratio pH-swing Selectivity

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The cation extraction and impurity separation were studied in order to investigate the recyclability of a slag produced from the steel refinery industry. Two types of slag (Slag-A, B) were collected and characterized in this study. The initial characterization by X-ray diffraction (XRD) and X-ray fluorescence (XRF) confirmed the existence of various kinds of ions in the slag such as Ca2+ (30 ~ 40%), Fe3+ (20 ~ 30%), Si4+ (15%), Al3+ (10%), Mn2+ (7%), and Mg2+ (3 ~ 5%). Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis on the extracted slag using 2 M HCl as a solvent indicated that a higher concentration of Ca2+ was extracted as the S/L ratio was increased. The Ca2+ extraction concentration were found to be 8,940 mg L-1 (Slag-A) and 10,690 (Slag-B) mg L-1 when the S/L ratio for Ca2+ extraction was 0.1. However, the extract was strongly acidic ( < pH 1) at 0.1 S/L. Also the other ions (impurities) were extracted simultaneously in addition to Ca2+. To increase the purity of Ca2+ in order to transform the slag to a high value resource, a pH-swing was conducted. The impurities tended to precipitate at higher rate as the pH was increased. Notably, the Ca2+ rapidly precipitated above a certain pH and at a pH of 10.5, while the selectivity of Ca2+ was over 99%. It is expected that the aqueous solution in which high contents of Ca2+ was selectively dissolved in this study would be suitable for the carbonation process for reducing CO2 and for the production of calcium carbonate.