Carbonation of argon oxygen decarburization stainless steel slag and its effect on chromium leachability. (20th May 2020) - Wang, Ya-Jun
Abstract: This study focuses on evaluating the carbonation potential of argon oxygen decarburization (AOD) slag and analyzing influence mechanism of carbonation on chromium leachability. Static thin-film accelerated carbonation and sequential leaching tests were carried out. Results show that the liquid to solid (L/S) ratio was the most influencing factor for AOD slag's carbonation, and the maximum carbonation ratio of AOD slag was 50–52% (L/S = 0.4 mL/g, PCO2 = 7.5 bar, and t > 6 h). Dicalcium silicate's carbonation resulted in the generation of amorphous calcium carbonate, crystalline calcite and silica gel. AOD slag's smooth surface could be eroded by these products gradually with carbonation furthered. The mineral phase evolution clearly influenced the mineral phase hydrolysis and physical encapsulation, and thus affected the hydrolysis behavior of the primary phase and the generation behavior of the secondary phase in the carbonated slags. Chromium leachability (20 days) declined to its lowest value (1.7 mg/kg) as the carbonation ratio growing to 23% and then increased to its highest value (7.9 mg/kg) with the carbonation ratio increasing to 52%. Chromium leachability varies with the carbonation ratio. The optimal carbonation ratio that resulting in minimum chromium leaching risk must be taken full in mind before using AOD slag in carbonation-related production activities. Graphical abstract: Image 1 Highlights: Static thin-film carbonation tests conducted on AOD Stainless Steel Slag. Maximum carbonation ratio is 50–52% (L/S of 0.4 mL/g, PCO2 of 7.5 bar and time>6 h) 23% carbonated AOD slag holds minimum Cr leachability. 52% carbonated AOD slag holds a higher Cr leachability than original AOD slag. Carbonation affects Cr leachability mainly by mineral phase hydrolysis and physical encapsulation.