Synergistic extraction and separation of valuable elements from high-alumina fly ash with carbochlorination method

A novel process was proposed for synergistic extraction and separation of valuable elements from high-alumina fly ash. A thermodynamic analysis revealed that to achieve effective carbochlorination, it is crucial to conduct carbochlorination of the fly ash within the temperature range from 700 to 1000 °C. The experimental results demonstrated that under the optimal conditions, the carbochlorination efficiency for Al, Si, Ca, Ti, and Mg exceeded 81.18%, 67.62%, 58.87%, 82.15%, and 59.53%, respectively. The XRD patterns indicated that Al and Si in the mullite phase (Al 6 Si 2 O 13 ) were chlorinated during the carbochlorination process, resulting in the formation of mullite mesophases (Al 4.75 Si 1.25 O 9.63 and Al 1.83 Si 1.08 O 4.85 ). After the carbochlorination process, Al was accumulated as AlCl 3 in the condenser, while SiCl 4 and TiCl 4 were enriched in the exhaust gas, and CaCl 2 , MgCl 2 , and unreacted oxides remained in the residue for further recycling.