Indirect mineral carbonation of chlorinated tailing derived from Ti‐bearing blast‐furnace slag coupled with simultaneous dechlorination and recovery of multiple value‐added products

Abstract The chlorinated tailing (CT) generated during titanium extraction from Ti‐bearing blast‐furnace slag contains 3–5 wt% chlorides, which are hazardous to the environment. In this paper, a process for simultaneous CO 2 mineralization, dechlorination, and recovery of multiple value‐added products was proposed to fully utilize the CT. In this process, Ti, Al, Mg, and Ca are extracted in the form of their sulfates via roasting with recyclable (NH 4 ) 2 SO 4 followed by leaching with dilute H 2 SO 4 . Their extraction ratios are 83.1%, 87.4%, 89.4%, and 92.1%, respectively. The chlorides are simultaneously removed from the CT as gaseous HCl with a dechlorination ratio of 98.5%. Subsequently, 89.5% of the Al and 97.5% of the Ti in the leaching liquor are successively recovered as NH 4 Al(SO 4 ) 2 ·12H 2 O with a purity of 99 wt% and titanium‐rich material with TiO 2 of 62.5 wt%. The CaSO 4 ‐rich leaching residue and MgSO 4 ‐rich leachate, after complete depletion of the Al and Ti, are separately carbonated with a mixed gas of CO 2 and NH 3 with total CO 2 capacity up to 279.8 kg CO 2 per tonne CT. The preliminary economic evaluation shows that income from selling products after the deduction of the cost of primary raw materials reaches 200 $/tonne CT. The proposed route therefore provides a cost‐efficient alternative for comprehensive utilization of the polluting CT. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.