Study On The Adsorption And Desorption Behavior Of Ammonium In The Mining Process Of Ion-absorbd Rare-Earth Mineral

Rare earth has a great strategic meaning,which was widely used in many aspects, such as military, metallurgy and agriculture.The ion-absorbed rare earth mineral was widely presented in the south of China.The most used mining technology was in-situ mineral-leaching method, which requires high concentration ammonium sulfate to replace the rare earth, resulting in a serious ammonium contamination..Ammonium adsorption mechanism and occurrence characteristics in soil were the key factors to solve the ammonium contamination.In this paper, lab experiments were conducted to study the ammonium adsorption and desorption mechanisms in rare earth mineral.In batch experiments, rare earth mineral was selected as a absorbent to simulate the real adsorption process, and the desorption experiments was carried out using saturation rare earth mineral to study the different forms of ammonium that existed in rare earth. In column study, the leaching solution was optimized by using different KCl concentrations to leach the rare earth mineral based on the real production conditions. The main conclusion are as follows:1)The adsorption kinetics can be better described by Elovich equation, particle diffusion model and Pseudo-second order kinetic.Chemical adsorption was the control step in rare earth adsorption process, the equilibrium time and the maximum adsorbing capacity were 3 hours and 970 mg/kg(which obtained from the Langmuir–Freundlich model), respectively.2) 33% ammonium can be desorbed from the saturated rare earth by deionized water, on the contrary, about 60% ammonium was desorbed by using 1M KCl.The residual ammonium amount in rare earth was accounted for about 6%.3)Compare with water, low concentration KCl was better in extracting the adsorbed ammonium, and has little adverse effect in production process.4) In column experiments, after the rare earth saturation, the proportion of soluble ammonium increased to 53%, while the exchangeable ammonium proportion decreased to 47%, the fixed ammonium accouted for a minor proportion in rare earth.