Glass-ceramics microstructure formation mechanism for simultaneous solidification of chromium and nickel from disassembled waste battery and chromium slag

Highlights: • CaNiSi₂O₆ crystal cannot stable immobilization Ni(II). • CaO / SiO₂ and heat treatment synergistically inhibit the formation of CaNiSi₂O₆. • Spinel glass-ceramics realized the simultaneous solidification of Cr and Ni. A new method to solidify Cr(VI), Cr(III), and Ni(II) simultaneously by using a glass-ceramics microstructure was used. For a crystallization temperature of 870 °C, base glass (air cooling) with a mass ratio of CaO / SiO₂ (R(C/S)) of 6/16, 10/16 precipitated a CaNiSi₂O₆ crystalline phase that could not solidify Ni(II) stably, and with an increase in R(C/S), the CaNiSi₂O₆ crystal precipitation tendency increased. When R(C/S) = 6/16, the crystallization temperature was 760 °C and spinel that was enriched in chromium and nickel formed preferentially during the inhibition of CaNiSi₂O₆ formation, indicating that lowering R(C/S) can inhibit the formation of CaNiSi₂O_6. Cr and Ni were mostly solidified in spinel, some of them enter augite (Ca (Mg, Fe, Al) (Si, Al)₂O₆) phases, a few of them were distributed in the glass matrix. The results of toxic leaching showed that the leached concentration of total Cr and Ni²⁺ in spinel glass-ceramics were 0 ppm and 0.07 ppm respectively, and the spinel glass-ceramics for simultaneous solidification of Cr(VI), Cr(III) and Ni(II) had excellent curing effect.