稀土原地浸矿残留氨氮的淋洗去除

Leaching Effect of Residue Ammonia Nitrogen in the In-situ Leaching of Ionic Type Rare Earth Mine

江西省赣南地区离子型稀土资源丰富,素有“稀土王国”之称,其经原地浸矿的模式开采后,导致矿体中残留大量氨氮,易造成地表水和地下水氨氮超标。以实验室柱淋洗模拟原位淋洗,探究去除赣南地区离子型稀土矿山原地浸矿后残留氨氮的可行性:以木质素磺酸钙(C_(20)H_(24)CaO_(10)S_(2))、硫酸镁(MgSO_(4))和清水为淋洗剂,考察氨氮淋洗效果;通过设置不同淋洗剂浓度和淋洗速度优化淋洗条件;筛选淋洗方式并分析其对土壤不同结合态氨氮、pH值、有机质等性质的影响。结果表明:C_(20)H_(24)CaO_(10)S_(2)和MgSO_(4)最佳淋洗浓度均为8 g/L;在1 mL/min的淋洗速度下,其对实际土壤中氨氮的淋出率分别为78.33%和92.16%,分别在第10个孔隙体积和第8个孔隙体积时低于15 mg/L的稀土尾水直接排放标准(DB 361016—2018);相较于清水淋洗,C_(20)H_(24)CaO_(10)S_(2)和MgSO_(4)主要淋洗脱除土壤中占比重较高的交换态氨氮;而C_(20)H_(24)CaO_(10)S_(2)淋洗后,土壤pH和有机质含量提升;经不同淋洗方式筛选,C_(20)H_(24)CaO_(10)S_(2)和MgSO_(4)浓度比为1∶1的复合淋洗剂能高效处理土壤氨氮、有效调节土壤pH值和土壤有机质,有利于离子型稀土矿原地浸矿土壤的氨氮治理以及矿山生态修复。

Gannan area in Jiangxi province,is famous as the“Rare Erath Kingdom”because of the high reserves of ionic type rare earth.However,the in-situ leaching of rare earth resulted in the amounts of ammonia nitrogen remained in the mine,and then caused the excessive of ammonia nitrogen in surface water or ground water.In order to explore the feasibility of leaching and remediation of residual ammonia nitrogen in the in-situ leaching of ionic rare earth mines in southern Jiangxi,column experiments were used to simulate the in-situ leaching of soil.The shear resistance of soil after leaching with calcium lignosulfonate(C_(20)H_(24)CaO_(10)S_(2)),magnesium sulfate(MgSO_(4))and water was analyzed.The influence of different concentrations of eluent and different leaching speeds on the leaching effect of ammonia nitrogen were investigated.To screen the elution effect of different elution methods on the residual ammonia nitrogen of rare earth tailings and their effects on the properties of different bound ammonia nitrogen,pH and organic matter in soil.The results showed that the optimal elution concentrations of C_(20)H_(24)CaO_(10)S_(2) and MgSO_(4) were 8 g/L;at the leaching rate of 1 mL/min,the leaching efficiency of ammonia nitrogen from tailing soil was 78.33%and 92.16%,respectively.Eluent reached the direct discharge standard of rare earth tail water at the 10th pore volume and the 8th pore volume for C_(20)H_(24)CaO_(10)S_(2) and MgSO_(4),respectively.Compared with the direct water leaching,C_(20)H_(24)CaO_(10)S_(2) and MgSO_(4) mainly eluted exchangeable ammonia nitrogen from soil.The pH and organic matter of soil after C_(20)H_(24)CaO_(10)S_(2) leaching were more conducive to the subsequent ecological restoration of soil.After screening by different leaching methods,the compound leaching with a concentration ratio of C_(20)H_(24)CaO_(10)S_(2) and MgSO_(4) of 1∶1 had significant effects on soil ecological restoration and in-situ leaching ammonia nitrogen elution.The research result showed that the leaching and remediation of residual ammonia nitrogen in the in-situ leaching of ionic rare earth mines in southern Jiangxi can utilize the combined leaching of C_(20)H_(24)CaO_(10)S_(2) and MgSO_(4),which can also increase the shear resistance of soil and reduce the risk of mine soil collapse.