稀土浸矿氨氮废水的吹脱试验研究

针对稀土浸矿产生的高氨氮废水,采用吹脱法对其进行处理,通过单因素试验和正交试验对影响因素进行了研究。结果表明,各主要因素对吹脱效果的影响大小为p H>吹脱温度>气液比;最佳操作条件:p H=11,温度为40℃,气液比为5 555.6∶1,吹脱时间为100 min。吹脱出的NH_3用H_2SO_4吸收,形成(NH_4)_2SO_4溶液,可作为浸取剂返回生产中使用或者用于生产(NH_4)_2SO_4肥料,实现资源回收利用。该试验工艺可作为脱氮除磷二级生物处理或一级强化处理的预处理。

稀土浸矿场地土壤异养硝化-好氧反硝化菌株K3的分离及脱氮研究

采用富集分离的方法,从江西赣州龙南县某风化壳淋积型稀土矿浸矿场地土壤中分离出1株土著异养硝化-好氧反硝化菌K3,通过形态学观察及16S rRNA基因序列分析,对菌株K3进行了鉴定,研究了其异养硝化及好氧反硝化脱氮特性,采用单因素实验研究了菌株K3脱氮的适宜条件,考察了菌株K3的耐盐特性和氨氮耐受性,探究了菌株K3对稀土浸矿场地残留铵盐模拟淋出液的脱氮工艺。结果表明,菌株K3为黄褐假单胞菌(Pseudomonas fulva),其异养硝化及好氧反硝化脱氮特性表现为:在分别以NH+4-N、NO-2-N和NO-3-N唯一氮源条件下,菌株K3生长良好,NH+4-N、NO-2-N和NO-3-N去除率分别为96.72%、91.40%和97.14%。在初始NH+4-N浓度为100 mg/L条件下,菌株K3的最佳碳源为柠檬酸钠,C/N为10,适宜初始pH、温度和转速分别为6~9、30℃~35℃、125 r/min~185 r/min。盐度低于30 g/L时,菌株K3生长良好,氨氮去除率在95%以上;初始氨氮浓度低于300 mg/L时,菌株K3生长良好,氨氮去除率在95%以上。利用菌株K3,以连续进水的方式对氨氮浓度分别为100 mg/L、200 mg/L及300 mg/L的酸性模拟淋出液进行处理,最终氨氮浓度均能低于15 mg/L,NO-3-N和NO-2-N的积累量较少。

Kinetics of rare earth leaching from roasted ore of bastnaesite with sulfuric acid

Sulfuric acid leaching process was applied to extracting rare earth（RE） from roasted ore of Dechang bastnaesite in Sichuan,China.The effect of particle size,stirring speed,sulfuric acid concentration and leaching temperature on RE extraction efficiency was investigated,and the leaching kinetics of RE was analyzed.Under selected leaching conditions,including particle size（0.074-0.100 mm）,sulfuric acid concentration 1.50 mol/L,mass ratio of liquid to solid 8 and stirring speed 500 r/min,the leaching kinetics analysis shows that the reaction rate of leaching process is controlled by diffusion through the product/ash layer which can be described by the shrinking-core model,and the calculated activation energy of 9.977 kJ/mol is characteristic for a diffusion-controlled process.

Remediation of in-situ Leach Mining Contaminated Soil by Amendment-plant Synergism

This study aimed to remediate in-situ leach mining contaminated soil by amendment-plant synergism. The results showed that plant species exhibited ex-tremely significant effects on the concentration of nitrate nitrogen; to be specific, the concentration of nitrate nitrogen in soil planted with wheat was reduced from 692.19 mg/kg to lower than 100 mg/kg; when the mass ratio of amendment to soil reached 3：50 and the amendment particle size was 1-2 mm, the concentration of nitrate ni-trogen in soil planted with wheat was reduced to 43 mg/kg. The amendment type exhibited extremely significant effects on the concentration of ammonium nitrogen; to be specific, when the mass ratio of amendment to soil reached 10：50, the concen-tration of ammonium nitrogen in soil added with 2-3 mm zeolite was reduced from 23 593.75 to 3 300 mg/kg on day 15. Amendments and plants mainly exhibited desorption performance for sulfate radical in soil, and the amendment type extreme-ly significantly affected the concentration of sulfate radical; to be specific, the con-centration of sulfate radical in soil added with limestone increased from 370 mg/kg to 900 mg/kg on day 7.

Study on the Acute Toxicity of Rare Earth Yttrium to Earthworms under the Stress of Leaching Agent Ammonium Sulfate

This study aimed to investigate the toxicity of rare earth ion yttrium under the stress of leaching agent ammonium sulfate （NH4）2SO4. [Method] By using earthworms as indicator organisms of environmental pol ution, acute toxic ef-fects of rare earth yttrium on earthworms under the stress of ammonium sulfate were investigated with filter paper contact method. [Result] Under single stress of rare earth yttrium, the semi-lethal concentration after 48 and 24 h was LC50=213.41 mg/L and LC50=322.63 mg/L, respectively. ② Under single stress of ammonium sul-fate, the semi-lethal concentration after 48 h and 24 h was LC50=13.89 g/L and LC50=15.05 g/L, respectively. ③ In combined treatment of low concentration （10 g/L） of ammonium sulfate and different doses of rare earth yttrium, the semi-lethal con-centration after 48 and 24 h was LC50=198.65 g/L and LC50=399.85 g/L, respective-ly; in combined treatment of middle concentration （14 g/L） of ammonium sulfate and different doses of rare earth yttrium, the semi-lethal concentration after 48 and 24 h was LC50=167.3 mg/L and LC50=256.73 mg/L, respectively; in combined treatment of high concentration （20 g/L） of ammonium sulfate and different doses of rare earth yttrium, the semi-lethal concentration after 48 h and 24 h was LC50=31.03 mg/L and LC50=127.65 mg/L, respectively. [Conclusion] Low concentration of ammonium sulfate could reduce the toxicity of rare earth yttrium to earthworms and produce certain antagonism against rare earth yttrium; middle concentration ammonium sulfate in-creased the toxicity of rare earth yttrium to earthworms and produced relatively sig-nificant synergistic effects; high concentration ammonium sulfate significantly in-creased the toxicity of rare earth yttrium to earthworms. Compared with ammonium sulfate, dead earthworms exposed to rare earth yttrium were more easily fractured, and living earthworms showed insensitive response to acupuncture.

Simulation of one-dimensional column leaching of weathered crust elution-deposited rare earth ore

The ion exchange model of the leaching process was determined via batch leaching experiments using the Kerr model, with the selectivity coefficient experimentally determined to be 12.59×10^-10 L^2/g^2. Solute transport laws of ammonium ions (NH4 +) and rare earth ions (RE^3+) in column leaching were described by the convection-dispersion equation (CDE). The source and sink in the CDE were determined by the Kerr model. The CDE with strong nonlinearity was solved using the sequential non-iterative method. Compared with the breakthrough curve of RE^3+, the correlation coefficient between the simulated and experimental curves reached 0.8724. Therefore, this method can simulate the one-dimensional column leaching of weathered crust elution-deposited rare earth ore. Moreover, the effects of different concentrations of ammonium sulfate ((NH4)2SO4) solution on the leaching rate of rare earth were analyzed. The optimal concentration of the (NH4)2SO4 solution had a linear relationship with the rare earth grade.

Leaching process of rare earths from weathered crust elution-deposited rare earth ore

In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynamic and mass transfer.The results show that the leaching hydrodynamics follows the Darcy law.The leaching kinetics can be described by the shrinking core model;the leaching process is controlled by diffusion of porous solid layer;and the mass transfer can be described with Van Deemter equation.This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.

Soil−water characteristics of weathered crust elution-deposited rare earth ores

The permeability of the weathered crust elution-deposited rare earth ores directly affects the efficiency of in-situ leaching.The soil−water characteristic curve(SWCC)is an important constitutive relation for calculating the permeability of ore body,which is related to many factors.Soil−water characteristic tests of rare earth ore samples considering different factors were carried out by using the pressure plate instrument.Effects of dry density,particle size and solution leaching on water holding behavior and the mechanism were investigated.The experimental observations indicate that with the decrease of dry density,the pore ratio increases gradually,and the saturated water content increases.Under the same matric suction,the water content decreases gradually with the increase of particle size,thus decreasing water holding capacity of ore accordingly.In the same water content,matric suction is inversely proportional to particle size.Under the same matric suction,the water content of ore samples after leaching is less than that of the ore samples before leaching,indicating that solution leaching can decrease water holding capacity of ore.