离子型稀土尾矿硫酸镁高效淋洗脱除氨氮技术研究

Technological Study on High-efficiency Leaching and Removal of Ammonia Nitrogen with Magnesium Sulfate from Ionic Rare Earth Tailings

针对赣南地区离子型稀土尾矿残存氨氮带来的长期拖尾问题,通过室内柱浸模拟矿区环境,采用淋洗药剂集中淋洗的方法脱铵,开展了淋洗药剂筛选、淋洗工艺优化、淋洗效果验证及尾矿残留淋洗药剂的脱除等方面的研究。结果表明,硫酸镁是适合赣南地区离子型稀土尾矿氨氮淋洗的药剂;当硫酸镁溶液的浓度为2.5%(质量分数)、pH值为5、注液强度为0.3 mL/min时,淋洗效果较好,淋洗液固比为2.9时,尾矿氨氮淋出率为96.97%。将硫酸镁淋洗尾矿在pH值为5.7的雨水中浸泡60天后,浸泡液氨氮浓度低于15 mg/L的直接排放标准。集中淋洗后的尾矿加注顶水可将尾矿中残留的镁离子淋洗下来循环利用,不会对离子型稀土尾矿矿区造成二次污染。

In view of the long-term tailing problem caused by residual ammonia nitrogen in ionic rare earth tailings in southern Jiangxi,indoor column leaching was carried out to simulate the environment of mining area,and then ammonium was removed by centralized leaching with leaching agents.Researches on lea-ching agent screening,leaching process optimization,leaching effect verification and residual leaching agent removal from tailings were carried out.The results show that magnesium sulfate is a suitable agent for the leaching of ammonia nitrogen from the ionic rare earth tailings in southern Jiangxi.When the concentration of magnesium sulfate solution reaches 2.5%(mass fraction),pH value is 5,and the injection strength is 0.3 mL/min,the leaching effect is relatively better,and the leaching rate of ammonia nitrogen from the tailings reaches 96.97%with the leaching liquid-solid ratio of 2.9.After the tailings leached by magnesium sulfate are immersed in the rainwater with pH value of 5.7 for 60 days,the concentration of ammonia nitrogen in the leachate is lower than the direct emission standard of 15 mg/L.Adding top water to the tai-lings after centralized leaching can leach down the residual magnesium ions in the tailings for recycling,which will not cause secondary pollution to the mining area of ionic rare earth tailings.