Surface modification of basic copper carbonate by mechanochemical processing with sulfur and ammonium sulfate

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 CO₃^2- 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.

Removal of Cu(II) from wastewater by using mechanochemically activated carbonate-based tailings through chemical precipitation

This work explored the feasibility of utilizing the copper tailings (CT) for removing copper from the waste mine water based on the mechanochemical activation. Batch experiments were performed to evaluate the influences of various experimental parameters like the dosage of CT, reaction time, initial concentration of Cu, and anion species. By cogriding copper solution with CT in the stirred mill (mechanochemical activation), over 99.5% of copper was removed and the residual copper concentration in the solution was less than 0.5 mg/L, reaching the discharge limit. This reaction was a chemical precipitation process. The calcite of CT played a major role in precipitating copper and had a better removal effect on copper in the copper sulfate solution than copper nitrate solution. For copper sulfate solution, the copper deposit was mainly posnjakite (Cu₄(SO₄)(OH)₆·H₂O). In the copper nitrate solution, the copper sediment might consist mainly of basic copper nitrate. The stability of the two reaction products was measured by leaching test. The result showed that the sediment obtained by this method was relatively stable and was not hazardous wastes.