Technical model of “Source-Flow-Sink” integration for pollution control of residual ammonia nitrogen after in-situ leaching of ion-type rare earth ore

Based on the characteristics of site point source pollution and watershed non-point source pollution of residual leaching agents in ion-type rare earth mining areas, this study proposed an integrated technology model of source reduction, process interception and terminal treatment of “Source-Flow-Sink”. The results show that the source leaching technology with lignosulfonate as the main leaching agent can reduce the residual ammonia nitrogen by more than 90% and improve soil stability. The high concentration of ammonia nitrogen in the leaching solution is absorbed and used for ecological restoration. At the initial stage of the sand barrier - Surface Permeable reaction wall, the highest reduction ratio of ammonia nitrogen and the highest increase of pH are 87.65% and 1.24, respectively. After 6 months of operation, the wall can still intercept silt by 90.38%, effectively playing the role of regulating water storage, intercepting suspended matter and sediment, reducing ammonia nitrogen and increasing pH. The filtration coupled biological treatment system runs continuously and stably for 9 months, and the effluent ammonia nitrogen concentration is less than 1 mg/L, which meets the requirements of Class Ⅲ water quality standards of surface water. The integrated technology model of “Source-Flow-Sink” proposed in this study not only provides technical support for the environmental treatment of ion-type rare earth mining areas but also provides important support for the green and sustainable development of ion-type rare earth resources.