Transformation of Hazardous Lead into Lead Ferrite Ceramics: Crystal Structures and Their Role in Lead Leaching

This study quantitatively determined the transformation of lead into lead ferrite ceramics and examined the influence of structural defects in lead ferrites (i.e. PbFeO, PbFeO and PbFeO) on lead leaching. Mechanisms of metal incorporation were examined from quantifying the phase compositions of lead ferrites in the products of sintering lead oxide with hematite. At low-temperature of 700°C, Pb was preferentially incorporated into the PbFeO crystals, and the incorporation efficiency ranged from 25.7 to 97.5% depending on different Pb/Fe molar ratios. By increasing temperatures to 750-850°C, PbFeO was subsequently reacted with hematite for the formation of PbFeO and PbFeO in Pb/Fe of 1/4 and 1/12 systems. PbFeO was found to be the high-temperature (1000°C) stable phase for incorporating lead, and the incorporation efficiency ranged from 28.6 to 92.1% by different Pb/Fe molar ratios. Leaching tests demonstrated that PbFeO was more resistant to acid attack than PbFeO and PbFeO. The crystal structural defects in PbFeO and PbFeO were determined to be the factors influencing their intrinsic phase durability. On the other hand, PbFeO was relatively free of structural defects and was found to be the preferred stabilization product to reduce the environmental hazard posed by lead.