Indoor Simulation of the In-situ Ammonium Sulphate Leaching and Rainwater Leaching Processes in the Ion-adsorption Rare Earth Mining Area
A large amount of ammonium sulfate leaching agent has remained in ion-adsorption rare earth tailings,which could leach into the ambient environment with rainwater and subsequently pollute surrounding soils and water bodies seriously.Using the soils collected from the rare earth mining area,we have conducted one-dimensional indoor soil column experiments to simulate in-situ ammonium sulfate leaching as well as rain water leaching processes.Hydrus-1 D model was then established to evaluate its performance in simulating both processes in the rare earth mining area.In the Hydrus-1 D model,dispersivity was calibrated to be 0.5 cm,whereas the Kd of ammonium sulphate leaching and rainwater leaching processes was 0.07 cm3/g and 1.21 cm3/g,respectively.In simulating the ammonium sulphate leaching progress R2 and root mean square error(ERMS)ranged from 0.95 to 0.99 and from 1.3 to 6.8 mmol/L respectively at the four observation holes.In rainwater leaching processes,R2 and ERMS respectively ranged from 0.93 to 0.98 and 0.2 1.6 mmol/L.This indicated that Hydrus-1 D is capable of satisfactorily simulating the migration behavior of ammonium ions during both ammonium sulphate leaching and rainwater leaching processes.In the tracer experiment,the Penetration time of Cl-was 30 90 min,and in the leaching experiment,the absorption saturation time of the four observation holes was 60 150 min.In rain leaching experiment,it takes 360 540 min for the concentration of ammonium ions in four observation holes to be below the detection limit.Soil adsorption has a significant influence on the transport process of ammonium ions in leaching and rain leaching.
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