离子型稀土土壤吸附铵态氮规律研究

发布时间：2018-03-20 09:21

本文选题：稀土　切入点：铵态氮　出处：《江西理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：江西赣南地区有着十分丰富的的风化壳淋积型稀土矿,近年来普及应用的原地浸矿工艺中硫酸铵溶液的大量使用对环境造成了严重的污染。因此,探究铵态氮在土壤中的迁移规律及其形态变化具有非常重要的意义。本实验选取了龙南足洞稀土矿土壤,该原矿土壤中的稀土60%-90%为水合或羧基水合离子状态吸附于高岭石及云母中,是风化壳淋积型稀土矿的原地浸矿的化学浸取基础。文章采用静态、动态与土柱实验结合的方式,先探究土壤吸附铵态氮的性能,然后在间歇式淋滤作用下探究铵在土壤中的形态与迁移特征,控制不同理化性质如pH、浸矿剂浓度、滴浸速度探究土壤中铵态氮的迁移规律。结果表明:(1)离子型稀土土壤吸附铵态氮满足Langmuir模型,动力学满足准二级动力学方程,说明土壤吸附铵态氮是单分子层吸附,以及以化学吸附过程控制为主。(2)离子型稀土铵态氮形态主要以交换态铵为主,水溶态铵与固定态铵的含量较少且达到吸附饱和的时间较短,土壤中硝态氮含量极少,土壤柱中发生硝化反应可以忽略,土壤中主要以吸附铵态氮交换稀土为主。(3)浓度不同改变了土壤中铵态氮吸附平衡的时间与稀土回收率,在实际的浸液过程中可以考虑“先淡后浓”的注液方法,不仅可以防止在达到注入低浓度前的解吸过程,且节约浸矿剂,提高稀土回收率。(4)速度不同几乎不改变土壤中的铵态氮达到饱和的时间,但是对稀土回收率有较大影响,因此在实际的浸液过程中可以考虑先慢后快的注液方式。(5)pH值没有改变铵态氮在土壤中的迁移特征,但是对稀土回收率有一定的影响,由于硫酸铵溶液本身的pH值在5.5-6之间,因此在实际的注液过程中,可以适当降低溶液pH值或者不调节就能提高稀土回收率。利用SPSS软件可以较好的拟合铵态氮随深度随时间的变化。(6)铵态氮的迁移可以分为5个带,与稀土浸出机理一致。
[Abstract]:There are abundant weathered crust leaching rare earth ores in south Jiangxi province. The extensive use of ammonium sulfate solution in the in-situ leaching process, which has been widely used in recent years, has caused serious pollution to the environment. It is of great significance to study the migration and speciation of ammonium nitrogen in soil. 60-90% of the rare earth in the soil of the ore is adsorbed in kaolinite and mica by hydration or carboxyl hydration ion state, which is the basis of chemical leaching of weathered crust leaching rare earth ore. The static, dynamic and soil column experiments are adopted in this paper. In order to control different physical and chemical properties, such as pH, concentration of leaching agent, the properties of ammonium adsorption in soil were investigated firstly, then the characteristics of ammonium morphology and migration in soil were studied under intermittent leaching. The migration of ammonium nitrogen in soil was investigated by drip leaching rate. The results showed that the adsorbed ammonium nitrogen in the ion type of rare earth soil met the Langmuir model, and the kinetics satisfied the quasi second-order kinetic equation, which indicated that the adsorbed ammonium nitrogen in the soil was monolayer adsorbed. The ion type of rare earth ammonium nitrogen was mainly exchangeable ammonium, the content of water-soluble ammonium and fixed ammonium was less and the time to reach adsorption saturation was shorter, and the nitrate nitrogen content in soil was very little. The nitrification reaction in soil column can be neglected. The concentration of adsorbed ammonium nitrogen exchange rare earth in soil changed the time of adsorption equilibrium of ammonium nitrogen and the recovery rate of rare earth. In the actual leaching process, the liquid injection method of "light first and then concentrated" can not only prevent the desorption process before the injection of low concentration, but also save the leaching agent. The rate of increasing the recovery rate of rare earth elements almost does not change the time of saturation of ammonium nitrogen in soil, but it has great influence on the recovery rate of rare earth elements. Therefore, in the actual leaching process, the pH value of slow injection and then quick injection can not change the migration characteristics of ammonium nitrogen in soil, but it has a certain effect on the recovery of rare earth, because the pH value of ammonium sulfate solution itself is between 5.5-6. Therefore, in the actual liquid injection process, the pH value of the solution can be reduced properly or the recovery rate of rare earth can be improved if the solution pH value is not adjusted. The transfer of ammonium nitrogen can be divided into 5 bands by using SPSS software to fit the change of ammonium nitrogen with depth with time. It is consistent with the mechanism of rare earth leaching.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X753;X53;O647.3

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