Lead recovery from PbZrO3 using wet ball-mill technique and hydrothermal synthesis of α-zirconium phosphate from wastewater for resource recovery

Lead recovery from lead zirconate (PbZrO3) ceramics was investigated using a wet ball-mill treatment in H2SO4 aqueous solution. Subsequently crystalline α-zirconium phosphate (α-Zr(HPO4)2·H2O) was synthesized using a hydrothermal technique in order for the resource recovery of zirconium in the wastewater after the wet ball-mill treatment. A wet ball-mill treatment in 4.5 M H2SO4 aqueous solution for 24 h was capable of converting more than 99.9% of the Pb initially included in the PbZrO3 to solid state PbSO4 with a purity of 98%. On the other hand, the Zr in the PbZrO3 was dissolved into the acidic solution during the treatment. The Pb and Zr metal elements coexisting in PbZrO3 were successfully separated by the wet ball-mill technique. Then, resource recovery of zirconium in the wastewater was examined. Crystalline α-Zr(HPO4)2·H2O was synthesized by hydrothermal treatments in 3.1-12.5 M H3PO4 aqueous solutions at temperatures of 120-240 °C for a duration of 70 h. The hydrothermally prepared powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and then they were also evaluated in terms of cation exchange capacity (CEC) measurement and thermogravimetric (TG) analysis.