Sequential alkaline-organic acid leaching process to enhance the recovery of rare earth elements from Indonesian coal fly ash

In this decade,coal fly ash(CFA)is considered a potential secondary source of rare earth elements(REEs).However,most REEs in coal fly ash are encapsulated in aluminosilicate glass,making it challenging to recover them through acid leaching.In this study,a sequential alkaline-organic acid leaching was developed for the recovery of REEs from CFA.The effect of alkaline leaching using NaOH solution on the destructive ability of aluminosilicate glass,as well as the mineralogy and morphology changes of the resulting coal fly ash,was first studied.Furthermore,the effectiveness of alkaline leaching on the recovery ability of REEs through organic acid leaching was evaluated.The results show that the maximum leaching efficiency for Si and Al,which was obtained at the optimum alkaline leaching conditions,namely NaOH concentration of 10 mol/L,reaction temperature of 65℃,liquid/solid(L/S)ratio of 10 mL/g,and reaction time of 90 min,is 28%and 32%,respectively.The digestion reaction with NaOH lixiviants also causes coal fly ash to become more porous,making it advantageous in the organic acid-leaching process at the REEs recovery stage.The utilization of the desilicated residue produced from the digestion process in acid leaching effectively increases the overall REEs recovery from 32.2%to 77.6%.

Leaching recovery of rare earth elements from the calcination product of a coal coarse refuse using organic acids

Due to the increasing criticality of rare earth elements(REEs),it has become essential to recover REEs from alternative resources.In this study,systematic REEs leaching tests were performed on the calcination product of a coal coarse refuse using hydrochloric acid and different types of organic acid as lixiviants.Experimental results show that the recovery of REEs,especially heavy REEs(HREEs)and scandium(Sc),is improved by using selected organic acids.Citric acid and DL-malic acid afford the best leaching performances;whereas,malonic acid,oxalic acid,and DL-tartaric acid are inferior to hydrochloric acid.Results of zeta potential measurements and solution chemical equilibrium calculations show that malonic acid is more likely adsorbed on the surface of the calcined material compared with citric acid and DL-malic acid.The adsorption may reduce the effective concentration of malonic species in solution and/or increase the amount of REEs adsorbed on the surface,thereby impairing the leaching recovery.Compared with light REEs(LREEs),a stronger adsorption of the HREEs on the surface is observed from electro-kinetic test results.This finding explains why organic acids impose a more positive impact on the leaching recovery of HREEs,By complexing with the HREEs,organic acids can keep the metal ions in solution and improve the leaching recovery.The adsorption of Sc^(3+)on the surface is the lowest compared with other REEs.Therefore,rather than complexing,the organic anionic species likely play a function of solubilizing Sc from the solid,which is similar to that of hydrogen ions.

Evaluating organic acids as alternative leaching reagents for rare earth elements recovery from NdFeB magnets

This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dismantled in order to recover NdFeB magnets,which were then thermally demagnetized at 350℃during 30 min before crushing in a ball mill under inert atmosphere.Scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd_(2)Fe_(14)B and the REEsrich phase containing Nd and Pr oxides.Additionally,X-ray diffraction(XRD)and Mossbauer spectroscopy(MS)analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its oxidation.Chemical analysis shows that the composition of the ground sample is Nd:22.8 wt%,Pr:3.3 wt%,Dy:1.2 wt%,Fe:62.6 wt%,Co:1.5 wt%,B:0.9 wt%,Ni:0.6 wt%.Diagrams of speciation and equilibrium phases(E_(h) vs.pH)were calculated to determine the predominance of the formed species in the REEs-organic acids systems.The influence of the organic acid type(acetic acid,formic acid,citric acid and tartaric acid),the acid concentration(10 vol%,up to saturation),and the solid/liquid(S/L)ratio(0.5%-10%)on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software JMP.Acetic acid(CH_(3)COOH)shows the highest leaching performance of REEs,allowing leaching yields over 90%for Nd,Dy and Pr in the acid concentration range of 1.6-10 mol/L and the S/L ratio range of 0.5%-5%at a temperature of 60℃.The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.

Organic Material and Trace Elements of Bituminous Rocks in the Ozank(?)y Field,Ankara,Turkey

Bituminous rocks in the Ozankoey （Ankara） field are different from those of the Paleocene- Eocene Mengen and Giineytepe （Bolu） regions in metal enrichment levels. Organic carbon （Corg） content of organic material-rich rocks in the Ozankoey （Ankara） field is 3.66-40.72% wt averaging 14.34%. The dominant organic materials are algae/amorphous accompanied by minor amount of herbaceous material （The dominant kerogen type is Type-I with a limited amount of Type-Ⅱ kerogen.）. The bituminous rocks in the Ozankoey field are enriched in heavy metals such as Ni, Mn, As and Cr. In comparison with the average enrichment values of dements, Ni, Mn, As and Cr in bituminous shales of the Ozankoey field are as about 4.38, 14.93, 10.90 and 5.58 times as average values. The average concentrations of these heavy metals are also as high as 215× 10^-6, 828 × 10^-6, 58.54 × 10^-6, and 148 × 10^-6 respectively. In addition, sorption properties of day and organic materials are also important for metal enrichments in the bituminous shales.

Organic Metallogeny of Weathering Crust RE Deposit

A series of experimental geochemical studies have been done to confirm the organic metallogenic mechanism of weathering crust RE deposits. It has been concluded that: (1) Rich REbearing weathering crusts contain abundant organisms such as monoacids, diacids and nonacid compounds. Varieties and quantities of the organisms decrease from the upper to the lower of the profile. Humic acids are mainly fulvic acids, which are characterized by containing conjugated π system, carboxylic group, hydroxyl group and only a few nitrogenous groups. No obvious benzene ring has been found. (2) The upper part of the weathering crust contains a great deal of microorganisms, of which the varieties and quantities decrease from the upper to the lower of the profile. No microorganism has been found in the deep part of the profile. The microorganisms and their metabolites such as aminoacids, shortchain acids and organic compounds with small molecular weights can form water soluble RE complexes, which accelerate the RE transportation from original rocks and precipitation states to watersoluble states and thus provide prerequisites for retransportation and reaccumulation of RE. (3) Medium and longchain acids can form REnAm(OH)x(H2O)y type mixedligand polynuclear RE complexes, which devoted to the RE accumulation, whereas shortchain acids and aminoacids can form not only mixedligand complexes with RE, but also water soluble complex ions, which also devoted to the transport and accumulation of RE. (4) The fulvic acids are very soluble in water. They are apt to be mobile in the weathering crust and are able to form soluble complex ions and insoluble mixedligand polynuclear complexes with RE at normal temperature and atmospheric pressure and pH4～6. The composition of these complexes varies with different conditions of the weathering crust. (5) All the organic acids, fulvic acids and microorgaisms have contributed to keeping constant pH condition of the weathering crust. (6) Complexes consisting of clays, RE(Al, Fe……) and fulvic acids have been found in the weathering crust and a bonding pattern has been preliminarily studied. As a conclusion, the dissolution, transport and accumulaiton of REE during weathering is a organic and inorganic interacted process.

Origin and diagenetic evolution of dolomites in Paleogene Shahejie Formation lacustrine organic shale of Jiyang Depression,Bohai Bay Basin,East China

The origin of dolomite in Shahejie Formation shale of Jiyang Depression in eastern China were studied by means of petrologic identification, compositional analysis by X-ray diffraction, stable carbon and oxygen isotopic composition, and trace element and rare earth element analyses. The results show that the development of dolomite is limited in the lacustrine organic rich shale of Shahejie Formation in the study area. Three kinds of dolomite minerals can be identified: primary dolomite(D1), penecontemporaneous dolomite(D2), and ankerite(Ak). D1 has the structure of primary spherical dolomite, high magnesium and high calcium, with order degree of 0.3-0.5, and is characterized by the intracrystalline corrosion and coexistence of secondary enlargement along the outer edge. D2 has the characteristics of secondary enlargement, order degree of 0.5-0.7, high magnesium, high calcium and containing a little iron and manganese elements. Ak is characterized by high order degree of 0.7-0.9, rhombic crystal, high magnesium, high calcium and high iron. The micritic calcite belongs to primary origin on the basis of the carbon and oxygen isotopic compositions and the fractionation characteristics of rare earth elements. According to the oxygen isotopic fractionation equation between paragenetic dolomite and calcite, it is calculated that the formation temperature of dolomite in the shale is between 36.76-45.83 ℃, belonging to lacustrine low-temperature dolomite. Based on the maturation and growth mechanism of primary and penecontemporaneous dolomite crystals, a dolomite diagenetic sequence and the dolomitization process are proposed, which is corresponding to the diagenetic environment of Shahejie Formation shale in the study area.

不同功能稀土微量元素螯合有机肥的研制及其对水稻发育、产量、品质的影响

针对长期不合理施用大量元素化肥、未经腐熟的农业废弃物等,造成土壤板结、盐渍化、重金属含量超标,导致农产品品质和产量下降等问题,研发了提质增效型、土壤改良型和重金属污染土壤修复型稀土微量元素螯合有机肥,并介绍了有机肥的生产工艺。以水稻为试验对象,连续2 a的田间试验示范结果表明:3种类型的有机肥对提高水稻产量、改善品质、节本增效具有明显的效果,增产幅度为4.1%~11.6%;水稻产品中对人体有益的铁、锰含量增幅为2.81%~87.44%,重金属含量下降4.46%~61.76%;3种类型的有机肥在提高耕地质量、修复土壤障碍因子等方面具有一定的作用。

试论有机质在华南花岗岩风化壳REE溶出、迁移和富集中的作用

通过实验研究，论证了花岗岩风化壳中存在有机质，含有丰富的一元脂肪酸和二元脂肪酸，腐殖酸及多糖化合物。ＲＥＥ能以ＲＥ（Ｈ２Ｏ）配位离子从原岩溶出，一些有机介质和无机介质有助于ＲＥＥ从原岩溶出、迁移，其中以脂肪酸溶出量最高。溶出过程配位反应与水解反应同时出现，溶出和在风化壳中保留同时进行，反应受ｐＨ控制。风化壳中ＲＥＥ存在有机结合形态，可能与长链酸或腐殖酸关系比较密切。活性态ＲＥＥ除了与粘土矿物关系密切外，可能与多羟基化合物或多糖有关。

微波消解-电感耦合等离子体质谱测定大气颗粒物中痕量稀土元素

研究了电感耦合等离子体质谱(ICP-MS)测定大气颗粒物中痕量稀土元素(REEs)的分析方法.在微波条件下,采用HNO3+H2O2(3+1)混合介质能快速而有效地分解颗粒物样品.详细讨论了测定稀土元素的质谱干扰.通过分析不同粒径颗粒物中稀土元素的含量,初步探讨了大气颗粒物中稀土元素的分布规律.结果表明:颗粒物试样的粒径越小, 稀土元素的含量越高.分析方法的检出限为0.7～2.8 pg/mL,用于大气颗粒物国际标样(SRM 1648)中稀土元素分析,结果与推荐值有良好的一致性.

表生地质体的Ce异常及其影响因素综述

综述了表生地质体的Ce异常及其影响因素。指出除了氧化还原条件等因素之外,微生物和有机质也是引起表生地质体Ce异常的重要因素。Ce异常在研究全球变化、古环境演化、流体来源、环境污染和地下核废料演变过程等方面的示踪作用是重要的研究动向。

绵阳-长宁拉张槽北段麦地坪组烃源岩特征——以绵竹清平剖面为例

以四川盆地绵阳-长宁拉张槽北段中央的绵竹县清平剖面为例,基于系统的薄片鉴定、有机地球化学分析、主元素、痕量元素及稀土元素的综合分析,研究绵阳-长宁拉张槽北段下寒武统麦地坪组烃源岩地质特征及元素地球化学特征。清平剖面麦地坪组主要岩性为碳质页岩含火山灰夹层、泥/微晶白云岩、碳/硅质页岩、白云岩屑粉砂岩与泥岩互层、白云岩屑磷块岩、白云岩/磷质岩屑粉砂岩夹泥岩。麦地坪组烃源岩则主要由其中碳/硅质页岩构成,主要特征是:(1)厚度达146.2m;(2)TOC质量分数为0.70%~42.68%,平均为12.95%;(3)干酪根类型指数在98~100,为Ⅰ型腐泥型干酪根;(4)沥青质反射率(Rob)为1.56%~2.83%(平均为2.31%),tmax为414~612℃(平均为577℃),表明烃源岩处在高成熟-过成熟阶段;(5)痕量元素V/(V+Ni)、U/Th、Ni/Co的比值及稀土元素δU、Ceanom、Ce/La比值,指示麦地坪组烃源岩形成于缺氧的强还原型水体环境。川西地区(绵阳-长宁拉张槽北段)麦地坪组为一套形成于缺氧环境下的有机质含量高、干酪根类型好、高成熟—过成熟阶段的优质烃源岩。

巢湖悬浮物中稀土元素(REE)的物源精确示踪作用

采用化学连续提取和等离子质谱仪(ICP-MS)测定法,对安徽巢湖悬浮颗粒物中稀土元素的含量、赋存形态和配分模式进行了研究．结果表明:巢湖悬浮物中稀土总量在19．20-174．82mg／kg之间,东西两个湖区含量差异明显,东半湖区高于西半湖区．巢湖东西湖区悬浮物残渣态稀土元素具有截然不同的页岩标准化配分模式,东半湖区为轻稀土富集型,西半湖区为重稀土富集型,说明巢湖东西湖区具有明显不同的物质来源．巢湖东半湖区和西半湖区悬浮物稀土元素赋存形态比例也不同,东半湖区为残渣态>铁锰氧化物结合态>>有机结合态、AEC态;西半湖区为铁锰氧化物结合态>残渣态>>有机结合态、AEC态,这是由于巢湖水体从西到东受到的污染强度减轻造成的,稀土元素赋存形态可以作为判别湖泊污染程度的新依据．

云南野生黑虎掌菌元素分析和风味研究

采用气相色谱质谱分析、氨基酸分析、电感耦合等离子体质谱分析方法,研究了云南野生食用黑虎掌菌独特的风味成分。研究结果首次发现,室温下黑虎掌菌中含挥发性芳香物质42种,主要为脂肪烃醇类、烯烃类和芳香性杂环类,非挥发性的滋味活性物质氨基酸17种,矿物质微量元素10种以及稀土元素9种。表明了黑虎掌菌具有较高的营养价值和药用价值。

风化壳稀土矿有机成矿机理研究

为论证风化壳稀土矿有机成矿机理进行了一系列实验地球化学研究，得出如下几点认识：（１）富含ＲＥＥ风化壳含丰富有机物，包含一元酸、二元酸和非酸有机物，剖面自上而下有机物种类和数量减少；腐植酸以富里酸为主，其特点是含共轭大π键及羧基、羟基，极少量含氮基团，未见明显苯核结构。（２）风化壳上层有大量微生物，剖面自上而下微生物种类和数量减少，下层未发现微生物。微生物及其代谢产物———氨基酸、短链酸和小分子量有机物作为配体与ＲＥＥ形成水溶性配合物，加速了ＲＥＥ从原岩及沉淀态向水溶态转移，为再迁移、再富集提供条件。（３）中长链酸可与ＲＥＥ形成ＲＥｎＡｍ（ＯＨ）ｘ（Ｈ２Ｏ）ｙ型多核混配配合物，起富集作用；而短链酸、氨基酸等与ＲＥＥ既可形成混配配合物又可形成水溶性配合离子，对迁移和富集均起作用。（４）富里酸有良好的水溶性，适于在风化壳迁移并在常温常压、ｐＨ４～６条件下与ＲＥ形成水溶性配合离子及不溶性多元混配配合物。其配合物形式随风化壳条件微小变异而不同。（５）有机酸、富里酸、微生物都为维持风化壳一定ｐＨ条件作出贡献。（６）发现风化壳中存在粘土ＲＥＥ（Ａｌ、Ｆｅ……）富里酸配合物，初步确定了其中一种结合模式。综上，提出在风化?

贵州遵义牛蹄塘组黑色岩系有机质的稀土元素地球化学研究

以贵州遵义寒武纪初牛蹄塘组黑色岩系的有机质为分析对象，对22个样品的稀土元素（REE）组成进行了研究，结果表明：①有机质的ΣREE占全岩ΣREE的10%左右，且其REE标准化配分曲线不同于全岩的。由于有机质主要来自海洋上层水体中的微生物，因而可以认为其REE特征代表的是古海洋上层水体的稀土元素组成特征；②有机质的REE总量变化于11.6×10＆-6-548×10＆-6之间，Ce异常系数变化于0.40-0.92之间，Eu异常系数变化于0.59-1.14之间。有机质的Ce异常系数和LaN/CeN值在剖面上显示明显的变化，指示研究区经历了大陆斜坡到大洋盆地再到大陆边缘的环境，指示在寒武纪初存在一次海侵。

有机配体对稀土元素在小麦体内积累和分异的影响

采用营养液培养和添加外源混合稀土等方法,研究了有机配体柠檬酸、EDTA和DTPA对稀土元素在小麦的根和叶中积累与分异的影响。结果表明,低浓度有机配体对小麦根和叶中的稀土元素,尤其是轻稀土元素的积累有轻微的促进作用,随浓度的升高则表现出显著的降低作用。有机配体对重稀土的作用比轻稀土强,使根和叶中稀土元素的分布曲线向重稀土相对亏缺的方向发展。3种配体对轻、重稀土分异的作用强度为:EDTA>DTPA>柠檬酸。通过VM INTEQ计算表明,在EDTA和DTPA作用下小麦叶中稀土元素的积累与轻、重稀土的分异主要由溶液中呈自由离子态稀土元素的含量和组成控制;柠檬酸作用下小麦叶中稀土元素的变化与自由离子态稀土的含量和组成关系较弱,推测REE-柠檬酸络合物可被小麦直接吸收并运转到小麦的叶中。

轻稀土元素在大鼠组织器官中的分布特征

研究La,Ce,Pr,Nd,Sm,Eu,Gd在大鼠组织器官中的分布规律。以雄性SD大鼠为试验对象,适应性喂养一周后剃去大鼠被毛,随机分为对照组和柠檬酸稀土低、中、高剂量组,每组10只共4组,剂量分别为0,50,500,5000 mg.kg-1(体重)。灌胃4周后,采集大鼠被毛、肝脏、脾脏等脏器。用等离子体质谱(ICP-MS)法测定大鼠被毛、肝脏、脾脏、全血中La,Ce,Pr,Nd,Sm,Eu,Gd轻稀土元素含量。轻稀土元素在大鼠全血、毛发及脏器中的分布特征分别为:肝、脾脏中的分布与摄入量完全对应;全血中分布趋于自然分布特征;股骨中对照及低剂量组的分布与摄入量倒置;而毛发中则呈现与受试物一致的特征,在一定程度上反映机体的稀土环境暴露水平。

胶州湾海水中悬浮颗粒对溶解态微量元素的影响

运用离子色谱离线螯合结合ICP-MS的方法,对胶州湾海水中的微量元素(V,Co,Ni,Cu,Mo,Cd,Pb,U,REEs)进行了精确的定量分析。在测试前对在同一站位不同层位采集的平行海水样品进行了两种不同的酸化处理:一份采取先过滤后酸化的方式,以获得海水中溶解态微量元素的含量;另一份采取直接酸化后分析的方式,以评估悬浮颗粒中的可交换态微量元素对溶解态微量元素测定结果可能造成的影响。通过对比研究发现,不同处理方法得到的V、Ni、Cu、Co、Pb以及稀土元素(REEs)的质量浓度存在很大差异,说明悬浮颗粒物质可能对海水中相应元素的测定产生较大的影响。各种微量元素之间的差异和相应离子或离子团的电荷性质、在海水中的配位作用以及悬浮颗粒物质的表面电荷性质有关。初步研究结果表明,在类似于胶州湾这样的近海海域,悬浮颗粒物质是控制微量元素分布特征的一个重要因素。

海洋生物体中稀土元素的微波消解电感耦合等离子体质谱测定研究

建立了微波消解样品处理、电感耦合等离子体质谱法测定海洋生物体中稀土元素的方法。用人发标准参考物质（GBW09101）、植物标准参考物质（GBW07603）以及实际样品标准加入回收的方法对文中所述的分析流程进行确认。实验结果表明，所建立方法的测定结果与标准参考物质的标准值或推荐值一致；样品标准加入实验的回收率在97％～104％之间。方法的定量下限为0．01～0．31ng·g^-1（10σ，n=10，干样）。