Fluorine Fixation Mechanisms of CaF ₂ and Ca ₄ Si ₂ O ₇ F ₂ during Spent Potlining Incineration with CaSiO ₃ for Zero‐Waste Utilization of Steel Waste Heat

Spent potlining (SPL), the hazardous solid waste with a high content of fluorine (Na 3 AlF 6 and NaF), has yet to achieve zero waste disposal. CaSiO 3 can detoxify SPL during incineration. This study investigates the fluorine fixation mechanisms of CaF 2 and Ca 4 Si 2 O 7 F 2 with CaSiO 3 addition during the SPL incineration by X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, inductively coupled plasma, and 19 F nuclear magnetic resonance. When SPL and CaSiO 3 are mixed in a 1:1 ratio and heated to 800 °C, solid phase precipitates are CaF 2 and NaAlSiO 4 . During the water leaching, the boundaries of CaF 2 and NaAlSiO 4 reacted with H 2 O by a surface chemical reaction, causing more F, Na, and Al elements to dissolve. Increasing the CaSiO 3 content (1:2 ratio) led to crystalline and amorphous Ca 4 Si 2 O 7 F 2 formation (<800 °C). During water leaching, surface hydration converts Ca 4 Si 2 O 7 F 2 into Ca 4 Si 2 O 7 (F,OH) 2 , creating a protective hydrated layer. Kinetic modeling yields chemical‐control rate constants k cvm = 32.5 × 10 5 h −1 (amorphous) and 1.92 × 10 5 h −1 (crystalline). These findings clarify the superior fluorine‐fixation mechanism of Ca 4 Si 2 O 7 F 2 over CaF 2 and NaAlSiO 4 . The proposed SPL–CaSiO 3 process enables high‐value reuse of SPL as mold flux supports zero‐waste goals.