Core-shell microstructure simultaneous solidification mechanism of Cr(III), Mn(IV), Ni(II) and Pb(II) in glass-ceramics

Abstract Glass-ceramics with crystal-coated glass phase microstructure were designed and prepared using the method of base-glass surface crystallization to simultaneously solidify multiple heavy metal ions (Cr3+, Ni2+, Mn4+ and Pb2+). Cr2O3 and PbO had opposite effects on the surface crystallization of the base glass, promoting and inhibiting it, respectively, when their concentrations were increased from 0.1 to 0.9 wt.%. This then affected their resistance to leaching of heavy metal. When the mass ratio of Na2O/SiO2 was increased from 0.08 to 0.20, the effect of PbO on inhibiting surface crystallization was weakened. The distribution of Cr3+, Ni2+, Mn4+ was inhomogeneous, and the concentrations of the ions were the highest at the glass phase-crystal interface and lowest in the wollastonite (CaSiO3) crystals. However, the concentration of Pb2+ at the interface decreased and the content of Pb2+ in the crystal gradually increased. The leaching test results showed that the leached concentrations of Cr3+, Mn4+, Ni2+, Pb2+ are all on the order of 10−2 mg/L.