| The ion-adsorbed rare earth tailings using ammonium sulfate as leaching agent has a large amount of water-soluble and exchangeable ammonium ions,which seriously threatens the water resources security of surrounding watersheds.In this paper,the sediment produced by rare earth mining was used as the eluent to elute the tailings,the mathematical model of ammonium ion desorption by sediment cation and the calculation model of sediment solution dosage was established,the relationship between the leaching efficiency and the amount of sediment solution was discussed,the promoting effect of rhamnolipid as leaching aid on ammonia nitrogen leaching of tailings was studied,the tail protection effect of lime water was analyzed.Based on the research results of this paper,It can greatly reduce the discharge of sediment and the leached ammonium ions can be used as leaching agent for the next nugget,and realized the recycling of leaching agent.During this process,the following conclusions were obtained:(1)It can be seen from the tailings ammonia nitrogen classification leaching test,the water-soluble and exchangeable ammonium ion concentrations of Pingnan(PN)tailings were0.356 mg/g and 0.548 mg/g,respectively.The water-soluble and exchangeable ammonium ion concentrations of Xunwu(XW)tailings were 0.257 mg/g and 0.958 mg/g,respectively.Through cup leaching test,Kerr model was used to quantify the desorption process of ammonium ions by sediment cations,the optimum leaching concentration of sediment solution for PN and XW tailings were 8.27 mmol/L and 12.64 mmol/L,respectively.(2)Based on the ion exchange equilibrium equation,the adsorption and desorption law of residual ammonium ions in tailings and sediment cations were described by ion exchange process and solute transport process,the calculation model of sediment solution dosage was established.If the leaching efficiency was set to 95.00%,the residual exchangeable ammonium ion concentration of PN and XW tailings were substituted into the calculation model,and the corresponding required sediment solutions of PN and XW tailings were 25.62 mmol and 46.98 mmol,according to the ore body pore ratio e = 1,the required sediment solutions for PN and XW were 2.5 and 3.0 times the pore volume,respectively.Similarly,when the sediment/rhamnolipid compound were used as the eluent,the required sediment solutions for PN and XW were 1.8 and 2.3 times the pore volume,respectively.(3)Rhamnolipid is a green and environmental friendly surfactant,which can reduce the surface tension of the solution,increase the permeability of ore body,strengthen ion exchange capacity and improve the leaching efficiency.When the concentration of rhamnolipid solution was 0.05 mmol/L,the surface tension of the solution decreased from 74.31 MN/m to 39.80MN/m,and the ore body permeability increased by 11.82% and 54.70%,respectively.The permeability coefficient of PN and XW tailings increased by 11.82% and 54.70%,respectively.The leaching concentration of ammonium ions in tailings reached the peak value of 9.86 mmol/L and 12.28 mmol/L,respectively.The leaching efficiency of residual ammonium ions in tailings column increased by more than 10.00%.Rhamnolipid is a good drenching aid.(4)After the injection of eluent,lime water was used to protect the tail,the adsorbed inorganic hydroxyl aluminum of PN and XW tailings accounted for 83.65% and 83.12%,respectively.Most of the aluminum ions were fixed,and a large amount of sulfate ions and calcium ions remain in the tailings column to form slightly soluble calcium sulfate,which avoids the influence of calcium ions on the surrounding watershed.This scheme can also be extended to the leaching of residual leaching agents with magnesium sulfate,aluminum sulfate and calcium chloride as leaching agents. |
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