Study On The Effect Of Type Of Leaching Agent On Lead Leaching In Ionic Rare Earth Ore Mining

Ionic rare earth is a strategic resource in China,but its mining process also brings serious pollution problems of ammonia nitrogen and heavy metals.In view of the problem of ammonia nitrogen pollution,the current research is devoted to the development of new ammonium-free leaching agents.However,the research on the effect of new leaching agents on the release of heavy metals in ionic rare earth ores has not been reported,so the impact on the environment is also unknown.In this study,new types of leaching agents such as magnesium sulfate,calcium-magnesium ammonium compound leaching agent and aluminum sulfate were used as the research objects,and the in-situ leaching process was simulated by combining batch experiments and column experiments to study the new leaching process.The leaching behavior and morphological distribution of lead and cations with different valences change to lead.The research provides a theoretical basis for the prevention and control of heavy metal pollution in ionic rare earth mining areas using a new type of leaching agent,as well as a theoretical basis for further improvement of the in-situ leaching process and the development of environmentally friendly leaching agents.（1）The amount of lead that was leached followed the order of compound agent CLA（60% CaCl₂+25%NH₄Cl+15%MgSO₄）>ammonium sulfate>magnesium sulfate.The lead leaching process includes acceleration and deceleration steps that follow a first-order kinetic model.The presence of Cl^-in the leaching agent makes the compound leaching agent the largest amount of Pb.This is mainly because Cl^-can complex with Pb²⁺,which can increase the solubility of Pb.（2）The soil heavy metal morphology tests showed that the three leaching agents primarily leached acid extractable lead,and the compound leaching agent leached the greatest amount of acid extractable Pb,which mainly due to the presence of NH₄Cl.The reducible fraction was enriched in the direction of migration of the leachate,which was due to the presence of SO₄^2-.（3）The ability of some typical mineral leaching agents to exchange rare earth ions and Pb is:aluminum sulfate>ammonium sulfate>magnesium sulfate.And the leaching of acid-soluble lead is controlled by cations,while the leaching of reducible lead is controlled by the system pH.（4）The ability of ammonium sulfate and magnesium sulfate to leach acid-soluble lead is stronger than aluminum sulfate,because the hydrated ion radius of NH₄⁺and Mg²⁺is smaller than Al³⁺;Aluminum sulfate also leach more reducible lead.The reason is that aluminum ions have a strong ability to maintain acidic pH.