Activating CaCO3 to enhance lead removal from lead-zinc solution to serve as green technology for the purification of mine tailings

Efficient lead removal from metal-containing wastewater, such as acid mine drainage (AMD), is an important step in environmental purification and secondary resources recovery. In this paper, a novel approach by mechanochemically activating CaCO3 through simply wet ball milling in metal-containing solution was developed, where selective Pb2+ precipitation in the form of PbCO3 was achieved based on its reaction with the CO from the activated CaCO3. By such milling operation, the removal efficiency of Pb2+ from aqueous solution could reach over 99%, while more than 99% Zn2+ (as well as Mn, Ni and Cd) was remaining in the solutions, demonstrating the feasibility and high effectiveness of precipitating Pb2+ and serving the purpose of recovering other metals without Pb impurity. The solubility differences between Pb carbonate and other carbonates of Zn, Mn, Ni or Cd were understood to be the main pathway and using CaCO3 would offer an easy operation and environmental friendly process to purify the metals-containing wastewater by precipitating Pb, compared with the difficulties when using alkaline neutralization to treat them. In addition, basic zinc carbonate (a zinc-containing ore waste) as an alternative precipitant to CaCO3 in the separation process was also confirmed to increase the zinc recovery in the solution while maintaining high Pb2+ removal efficiency. (C) 2020 Elsevier Ltd. All rights reserved.