Removal and kinetics of residual ammonia nitrogen in ionic rare earth tailings by leaching

Calcium lignosulfonate, rhamnose-lipids, magnesium sulfate and potassium magnesium sulfate were used for cup leaching and column leaching of residual ammonia nitrogen in ionic rare earth tailings. The effects of concentration (0~20 g/L), temperature (5~50 ℃), solid-liquid ratio (1∶2.5~1∶15) and time (0~24 h) on the removal efficiency of ammonia nitrogen were investigated. Column leaching experiments were conducted to compare the leaching effects of different agents and to carry out kinetic fitting. The results show that the removal ratio of ammonia nitrogen by column leaching of calcium lignosulfonate is 85.88%, which is 4.02 times higher than that by water leaching. The leaching process of magnesium sulfate and potassium magnesium sulfate conforms to the quasi-first-order kinetic equation, while the leaching process of calcium lignosulphonate fits the double constant equation better. Combined with the physical and chemical properties analysis of soil after leaching, calcium lignosulfonate as a leaching agent can not only effectively remove ammonia nitrogen, but also adjust soil pH, which has good engineering application potential.