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

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 CO2 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 (NH4)(2)SO4 followed by leaching with dilute H2SO4. 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 NH4Al(SO4)(2)center dot 12H(2)O with a purity of 99 wt% and titanium-rich material with TiO2 of 62.5 wt%. The CaSO4-rich leaching residue and MgSO4-rich leachate, after complete depletion of the Al and Ti, are separately carbonated with a mixed gas of CO2 and NH3 with total CO2 capacity up to 279.8 kg CO2 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. (c) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.