Enhancing leaching efficiency of ion adsorption rare earths by ameliorating mass transfer effect of rare earth ions by applying an electric field

Improving the seepage of leaching solution in the ore body and strengthening the mass transfer process of rare earth ions during in-situ leaching are two critical methods to improve the leaching efficiency of rare earth.In this study,2 wt%MgSO_(4)solution was used for the indoor simulated column leaching experiment on rare earth samples and an electric field was applied at both ends of the samples.Then the effects of different intensities,initial application time and duration of the electric field on the rare earth leaching system and its mechanism were investigated.The results show that compared with the single MgSO_(4)solution leaching,applying an electric field with a strength of 6 V/cm can save the leaching time of 30 min and increase the flow velocity of the rare earth leachate by 26.98%.Under the optimal conditions of applying an electric field with a strength of 6 V/cm for 20 min to the leaching system after10 min of the rare earth leachate flowing out,the leaching efficiency of sample increases from 81.20% to 86.05% with the increase of 4.85%.The mechanism analysis shows that when a direct current electric field is applied to the rare earth leaching system,rare earth ions rapidly change from disorderly movement with the seepage into faster and directional movement.In addition,the seepage of the leaching solution is also improved due to the increase of the cross-sectional area of the seepage channel,the polarized water molecules migrate directionally by force from the negative pole,and the movement of the hydrogen is generated by the electrolytic water.More impo rtantly,based on the principle of in-situ leaching process,the layout of injection holes and deflector holes in this process provides a natural site for the electrode layout of the electric field.With the simple equipme nt and the ope ration,the rare earth leaching process with the applied electric field has high feasibility in industrial application.

Mass transfer in heap leaching of weathered crust elution deposited rare earth ore with Al_(2)(SO_(4))_(3) solution

In order to increase efficiency and avoid NH^(4+)-N pollution in the leaching process of weathered crust elution-deposited rare earth ores,the mass transfer in heap leaching with Al_(2)(SO_(4))_(3) solution was simulated with column elution and experimentally optimized.The results indicate that the leaching yield is also up to 99%for leaching with aluminum sulfate instead of ammonium sulfate.The optimal flow rate is 60 mL/h,the height equivalent to a theoretical plate(HETP)is 1.29 mm correspondingly.The peak value position of RE^(3+)is 60 mL/h,Fe^(3+)is 100 mL/h,however,Al^(3+)is 150 mL/h,and the heap leaching process has kinetic separation effect.

Effect of Polyvinylidene Fluoride Hollow Fiber Membranes on Mass Transfer of Samarium

The influence of swelling and stripping acidity on the mass transfer coefficient based on water phase and the inner diameters of membranes were studied with P507-HCl-Sm as working system in the two different kinds of hollow fiber membranes. Effects of extractant concentration, H+ concentration in aqueous phase and Sm3+ concentration on extraction rate were discussed and the corresponding reaction series were obtained. According to the investigations on the interfacial kinetics, the reaction kinetics equation and reaction rate constant were obtained.

Effect of surfactant addition on leaching process of weathered crust elution-deposited rare earth ores with magnesium sulfate

Surfactants were proposed to be added into magnesium sulfate solution to improve the leaching process of weathered crust elution-deposited rare earth ores(WREOs).Effects of surfactants and their concentration on the seepage of leaching solutions and the leaching efficiency of rare earth(RE)and aluminum(Al)were investigated,and the leaching kinetics,the mass transfer process,the adhesion work and the adhesion work reduction factor were analyzed to reveal its strengthening leaching mechanism.The results show that cetyltrimethylammonium bromide(CTAB)has a better strengthening effect on the leaching process than dodecyl trimethyl ammonium bromide(DTAB),sodium dodecyl sulfate(SDS),sodium oleate and oleic acid.In the presence of 0.04%CTAB in 0.2 mol/L solution,the permeability coefficient of WREOs increases from 0.945×10^(-5)to 1.640×10^(-5)cm·s^(-1),and the leaching efficiency of RE increases from 80%to 90%,confirming the promotion of surfactants on the leaching process of WREOs.Kinetic analysis shows that the leaching process conforms to the inner diffusion control model,and the leaching kinetics equations of RE and Al related to CTAB content are obtained.Mass transfer discussion shows a smaller height equivalent to theoretical plate(HETP)of RE and Al at CTAB content of 0.04%,suggesting the higher mass transfer efficiency here.According to the interfacial properties of leaching solutions,the calculated adhesion work and the adhesion work reduction factor further demonstrate the strengthening leaching effect of CTAB on the leaching process of WREOs.

Extraction of Neodymium by Emulsion-Liquid-Membrane within Hollow-Fiber-contactor and Its Mass Transfer Properties

A non-dispersive extraction technique, using an emulsion liquid membrane within a hollow-fiber-contactor for the extraction and enrichment of Nd^3＋ from the dilute feed aqueous, was applied. The emulsion system is consisted of span80 [ sorbitian monooleate], paraffin oil, D2EHPA [ 2-（ 2-ethylhexyl- phosphonic acid）], kerosene as well as HCl solution. The extraction under various conditions such as the span80 concentrations, the flow rate of aqueous, the extraction time and HCl concentrations in receiving phase were studied. Results show that the lower the flow rates of aqueous are, the higher the extraction percentage and enrichment-fold are, and the extraction percentage increases with the increasing of HCl concentrations. When the initial Nd^3＋ concentration in feed is maintained at 1000 mg· L^-1 and the emulsion is recycled with 70 times by a counter-flow,

三重四极杆电感耦合等离子体质谱(ICP-MS)法测定氧化铕中13种稀土杂质元素

稀土杂质元素直接影响高纯单金属稀土材料的整体性能,是高科技领域许多材料的重要组成部分。通过考察消解酸量、温度、时间,氧气反应气流量,稀释气流量,建立了基于三重四极杆电感耦合等离子体质谱(ICP-MS/MS)法直接测定氧化铕中13种稀土杂质元素的分析方法。采用0.1%基体直接进样,可以很大程度提高前处理分析效率。利用碰撞模式测定氧化铕稀土中的Y、La、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Yb、Lu元素,氧气质量转移模式测定氧化铕中的Tm,两种模式结合可以有效去除多原子干扰,实现氧化铕的稳定测试。通过对氧化铕标准物质(GBW02902)直接测定,结果表明,在碰撞和氧气质量转移模式下,各元素线性相关系数(r)均大于0.9999,方法检出限为0.001~0.023 mg/kg,测试精密度优于2.0%,13种元素的测定值都在认定值的不确定度范围之内。方法操作简单、测定稳定、效率高,为实验室进行氧化铕材料中REE杂质的准确测定提供思路和借鉴。

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.

Leaching and mass transfer characteristics of elements from ion-adsorption type rare earth ore

The differences in the leaching and mass transfer characteristics of ion-adsorption type rare earth ore between rare earth and non-rare earth impurities were investigated. It is determined that the leaching kinetics of rare earths （REs）, Mg and Ca could be described by the shrinking-core model. The leaching rate is controlled by inner diffusion and is in the order of Mg 〉 Ca 〉 RE. The apparent activation energy is 8.48, 6.79 and 6.32 kJ·mol^-1, respectively. In leaching system of Al, the leaching efficiency decreases with the increase in temperature because of hydrolysis reactions. The leaching efficiency of aluminum increases firstly and then decreases with the passage of time when the temperature is higher than 35 ℃. Besides, there is a good consistency in leaching characteristics and mass transfer, and the order of the time-to- peak is Mg 〈 Ca 〈 RE 〈 Al. Therefore, rare earth and non-rare earth may be partly separated by expanding the separation coefficient. The research could provide a theoretic basis for the separation of rare earth and non-rare earth impurities. Furthermore, compound leaching with magnesium salt and calcium salt is innovatively proposed to solve the problem of calcium and magnesium nutrient loss in the soil as well as eliminate ammonia-nitrogen emissions from the source.

Application of surfactant for improving leaching process of weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores(WREOs)in China are the main source of medium and heavy rare earths in the world.In order to improve the seepage and the mass transfer of traditional ammonium salt leaching process of WREOs,surfactants were added in the ammonium sulfate leaching solution and the ammonium chloride leaching solution.The leaching kinetics,the mass transfer process,and the adhesion work reduction factor calculated from the interfacial properties were studied to reveal the strengthening mechanism of surfactant.In the presence of the tested five surfactants,cetyl trimethyl ammonium bromide(CTAB),dodecyl trimethyl ammonium bromide(DTAB),sodium dodecyl sulfate(SDS),sodium oleate and oleic acid,the permeability of WREOs is improved,the rare earth(RE)leaching efficiency increase and the impurity aluminum(Al)leaching efficiency decrease,indicating its promotional effect on the leaching process of WREOs.Furthermore,CTAB shows a better leaching enhancement,and the optimal addition dosage is 0.4 g/L for the two ammonium salt leaching agent systems.The kinetics analysis shows the internal diffusion controls model of RE and Al leaching process,and the leaching kinetics equations of RE and Al related to CTAB concentration were obtained for the two ammonium salt leaching systems.According to the chromatographic plate theory,the mass transfer efficiency of RE increases with the CTAB concentration increasing until 0.4 g/L,which confirms that the optimal CTAB addition is 0.4 g/L.Smaller adhesion work and adhesion work reduction factor indicate more favorable permeation as well as the leaching process.

气相抽提去除红壤中挥发性有机污染物的去污机理探讨

通过探讨土壤气相抽提去除红壤中挥发性有机污染物的去污机理,建立了一维稳态条件下污染物在土壤多孔介质中传质的总微分方程,分别求出了平衡模型和动力学模型的解析解和数值解,并用实验结果对平衡模型和动力学模型进行了模拟和验证.实验结果和模型模拟结果表明理论模型与实验结果吻合良好,平衡模型和动力学模型在描述污染物在土柱通风过程中的传质时,分别适用于不同的阶段.在通风初期平衡模型能够很好地描述实验结果,而随着时间的推移,平衡模型的预测曲线逐渐偏离数据点,到了通风中后期,只有动力学模型才能够较好地描述和预测实验结果.

乳状液-中空纤维膜萃取钕及其传质性能研究

采用非分散的萃取方式,将乳状液膜体系Span80/皂化D2EHPA/煤油/液体石蜡/盐酸通过中空纤维膜对钕进行了逆流萃取,研究了乳化剂浓度、乳状液与水相流量比、内相盐酸浓度、萃取时间等因素对萃取率的影响。结果表明,乳状液和水相流量越小、乳状液内相盐酸浓度越大,萃取率越高,内相富集倍数越大。将乳液循环萃取70次后,内相富集倍数达50.2,表明乳状液在中空纤维膜萃取器中对稀土有很好的萃取和富集效果。与乳状液膜的分散萃取方式相比,非分散萃取方式的萃取速率更快,而且萃余水相澄清,液膜稳定性好,泄漏少,膜溶胀小。同时还计算了非分散萃取过程基于水相的总传质系数实验值和理论值,当调节参数Kf(络合反应传质系数)的取值为3.5×10-9m.s-1,水相流量大于10×10-6m3.s-1时,实验值与理论预测值相吻合。

稀土分离中离心萃取器传质性能的研究

用φ２０ｍｍ微型离心萃取器对０．２２ｍｏｌ·Ｌ（－１）ＨＮＯ３－１．９７ｍｏｌ·Ｌ（－１）ＲＥ／１ｍｏｌ·Ｌ（－１）Ｐ（５０７）－煤油、３．８ｍｏｌ·Ｌ（－１）ＨＣｌ／１ｍｏｌ·Ｌ（－１）Ｐ（５０７）－煤油－０．０９ｍｏｌ·Ｌ（－１）Ｙ等四个体系进行了稀土的萃取和反萃取实验，结果表明：在两相液体混合接触时间为１０ｓ左右的条件下，除了Ｙ的反萃级效率仅～３０％外，其它实验的级效率都达到９０％左右。在采用了两相液体混合接触时间达６０ｓ左右的长接触时间离心萃取器后，Ｙ的反萃效率也达到９０％左右。这些实验结果从传质性能方面证明了离心萃取器应用于稀土萃取流程是可行的。

南方稀土矿浸出传质的研究

本文从传质的角度，研究了淋侵速度、浸出剂浓度、矿石粘度、原矿稀土品位对南方某稀土矿浸出效果的影响；用色层塔板理论和vanDeemter方程进行分析，找出了然浸速度与浸出效果之间的规律，为高效、低耗、合理地开采南方稀土矿提供了理论依据．

乳状液膜提取稀土的传质模型研究(Ⅱ)

针对研究（Ⅰ）提出的传质模型,本文通过实验验证了普遍情况下稀土离子的传质模型方程。实验证实该传质模型在整个传质过程中模型计算值均能与实验值很好地吻合。结果表明本研究建立的乳状液膜提取稀土的传质模型不仅较好地描述了液膜体系中稀土的传质行为,而且模型数学关系式简单,计算方便,实用性强。

聚偏氟乙烯中空纤维膜器对钐传质性能的影响

以P50 7 煤油 HCl Sm为实验体系 ,在两种聚偏氟乙烯中空纤维膜器中研究了溶胀性能、反萃酸度对基于水相的总传质系数及中空纤维膜孔径的影响 ,考察了料液酸度、萃取剂浓度、钐离子浓度与萃取速率的关系 ,获得了相应的反应级数。根据界面反应动力学 ,得到了速率常数值和动力学方程。

LaNi_(4.7)Al_(0.3)D_x去氘化热、质传输二维模型研究

建立了LaNi4 .7Al0 .3Dx 去氘化过程中热、质传输的二维数学模型 ,该模型考虑了气相和固相之间存在的温差以及氘化物密度和比热的变化。计算了金属氘化物在去氘化过程中气 固相温差、组分和密度的分布 ,以及热导率和加热流体温度对气 固相温差的影响 ,并考察了模型的适用性。计算结果表明 :热导率及加热流体温度对气 固相温差影响显著 ,最大温差随热导率的增加而减小 ,随加热流体温度的升高而增大 ;金属氘化物中组分和密度的分布与气 固相温差有关 ;根据数学模型获得的反应分数与实验值具有很好的一致性。

用在线流动注射法研究膜基萃取过程中的铵离子传质规律

采用 氨气敏电 极结合流 动注射 分析法， 对中 空纤 维膜 器中 氨化 二（２ ，４ ，４三 甲基 戊基） 膦酸（ Ｈ Ｂ Ｔ Ｍ Ｐ Ｐ）庚 烷体系萃 取镱、铒 过程的铵 离子进 行在线 分析 ． 结 果表 明， 当 Ｎａ Ｏ Ｈ 浓 度为 ００２ｍ ｏｌ／ Ｌ，响应 保留时 间为 ９０ ｓ 时，铵 离子 标准 曲线 在２０ ×１０ － ５ ～１ ０ ×１０ － １ ｍ ｏｌ／ Ｌ 铵 离子 浓 度范围内 ，具有良 好的线性 关系． 样 品溶液 的用量由 普通电极 法的３０ ｍ Ｌ 降至０５ ｍ Ｌ；样品测 定频率可达１５ 次／ ｈ ． 当 Ｈ Ｂ Ｔ Ｍ Ｐ Ｐ 被氨化后 ，在高 ｐ Ｈ 范围 内，氢离子 的传 质仍 优先 于铵 离子 ，ｐ Ｈ 值 下降很快； 然后是 Ｈ＋ 、 Ｎ Ｈ＋４ 的 混合交换 ，料液相 形成缓冲 体系，ｐ Ｈ 值 基本不变 ． 同级 萃取反萃 中，也有基本相 同的传

乳状液膜分离稀土的传质模型的发展现状

本文对近些年出现的乳状液膜法迁移稀土离子的传质模型作了较为详细的总结和比较。由于在液膜体系中，影响迁移的因素比较多，推导出的数学模型都比较复杂。经过简化和近似处理后得到的解析式，都可以和实验值取得较好的一致性，但又有一定的局限性，另外，新的液膜体系不断出现，因此对数学模型的研究仍需深入。

复合镁盐浸取风化壳淋积型稀土矿过程强化研究

风化壳淋积型稀土矿是世界中重稀土的主要来源,其中稀土以水合或羟基水合离子吸附在黏土矿物上,可采用离子交换的方式浸出稀土矿。为提高以复合镁盐为浸取剂时稀土的浸出效果,采用柱浸的方式模拟原地浸出过程,研究了复合镁盐浸取风化壳淋积型稀土矿稀土及铝的浸出传质过程,并结合色谱塔板理论进行了分析。结果表明,采用氯化镁和硝酸镁摩尔比为4∶6的复合镁盐浸取剂浸出稀土的效果最佳;在一定范围内较高的镁离子浓度可以通过提供驱动力来克服扩散阻力,从而加强稀土(RE)和铝(Al)的传质过程;pH在4~8范围内几乎不影响稀土和铝的传质效率,强酸性环境(pH=2)下浸出稀土矿会显著加强铝的浸出,不利于后续处理;高温有助于稀土及铝的浸出;采用复合镁盐柱浸回收稀土的最佳工艺条件为:MgCl2和Mg(NO3)2摩尔比为4∶6,镁离子浓度为0.2 moL/dm3,pH为溶液初始值,夏季作业有利于提高浸出传质效率。

地球物质的人为转移与地球物理环境

通过分析航天活动向外层空间迁移物质形成的地球转动惯量改变,重叠1998年以来,从高纬度向赤道方向上,巨大物质发生再分布构成的地球转动惯量改变,和它们致使地球自转速率的变慢,重合地球自转运动的规律性变慢,以叠加的效果影响地球物理环境;以及与地壳差速旋转的巨大地核,及覆盖地表的水,包裹地球的大气层,在地壳转速变化时,完成其相互间角动量交换存在的时间滞后性,将会在一些瞬时段突出物质转移对地球物理环境的作用影响.讨论航天发射从地球迁移到外层空间的物质,正将形成一定规模的物质群而改变地球系统的空间结构,且现时,太空武器化竞争已剑拔弩张,其一旦加剧了航天活动构成外层空间新物质体系圈层的发展,其过程对地球物理环境的影响,合并地球自身多重因素的作用,可能会增大突破维持稳定自然环境的某些临界条件的几率和增大突发事件发生频率.