Effect of biochar and attapulgite on soil improvement of ionic rare earth leaching wasteland

Soil acidification, residual leaching agent pollution, poor fertilizer conservation ability, and harsh vegetation site conditions are the main obstacles to the ecological restoration of abandoned land in ionic rare earth mining areas. In this study, rice husk biochar and attapulgite were considered as remediation materials to investigate the soil improvement and the source control of residual leaching agents in abandoned leaching land through remediation experiments. The results show that rice hull biochar and attapulgite significantly improve soil pH and cation exchange capacity, and biochar significantly increases soil organic matter. The best remediation effect is achieved by applying rice husk biochar and concave-convex rod at a ratio of 5% of soil mass in a 1∶1 ratio. Compared with the control group, the soil pH value increases from 4.51 to 7.45, and the organic matter and CEC contents increases by 77.5% and 25.4%, respectively. The alfalfa germination rate and fresh weight increase by 17.1% and 167.5%, and the ryegrass germination rate and fresh weight increase by 7.8% and 293%, respectively. In comparison, the leaching rate of soil ammonia nitrogen decreases by 20%. In-situ remediation experiments show that the remediation materials can not only improve the soil properties of abandoned land, but also control the migration and diffusion of residual leaching agent at the source, which provides a soil remediation material for ionized rare earth leaching abandoned land with environmentally friendly and sustainable restoration effect, and also provides ideas for the source control of ammonia nitrogen pollution of residual leaching agent in ionized rare earth mining area.