Enhanced carbon dioxide sequestration and Cr detoxification: Direct carbonation of AOD slag with additives under ambient conditions

Abstract

This study focused on AOD stainless steel slag (AOD slag), utilizing a direct wet carbonation process at ambient temperature and pressure to effectively capture CO2. We first evaluated the impact of four distinct additives such as NaCl (Simulated seawater concentration, 2.43 mol/L), NaOH (Simulated cold rolling wastewater, 0.01 mol/L), NH4Cl (0.5 mol/L) and CH3COONH4 (0.5 mol/L) on the carbonation of AOD slag, ultimately selecting CH3COONH4 for its superior performance. Within the “AOD slag + CH3COONH4” system, we conducted a comprehensive examination of carbonation parameters, including additive concentration, particle size, solid-liquid ratio, temperature and time, with a focus on optimizing carbonation efficiency (ηc) and carbonation capacity (Cc). Additionally, we provided an in-depth exploration of the simultaneous efficient carbonation and detoxification mechanisms pertaining to the stainless steel slag. Under standard conditions (293 K, 1 atm), the system achieved an impressive ηc of 80.02%, and Cc of 386.62 kg CO2/ton slag, higher than those previously reported. Furthermore, after five experimental cycles, the system maintained a 70% original efficiency, with Cr leaching concentrations significantly below the national standard requirement of 1.5 mg/L.