Super-stable mineralization of multiple heavy metal ions from wastewater for utilization in photocatalytic CO2 reduction and trace precious metal recovery

•The atomic economical synthesis of CaCr-LDH and the rapid purification of wastewater containing high concentration of Cr3+ are realized by super-stable mineralization.•Through multistage super-stable mineralization, using CaCr-LDH to treat multiple divalent heavy metal ions can reduce costs by about 50% and sludge by about 10%.•The product showed excellent performance in photocatalytic CO2 reduction and precious metal (Au) recovery from printed circuit board leaching wastewater.