Migration behavior,separation and recycling of rare earth during thermal decomposition of Zhijin phosphorus ore

Zhijin phosphorus ore is a moderate and low-grade phosphorus rare-earth ore contained in mines. The separation and extraction of associated rare earth are important research topics. In this study,the migration behavior of rare earth during the thermal decomposition of Zhijin phosphorus ore and the separation and extraction of rare earth in phosphorus slag are discussed systematically. During the thermal decomposition process of phosphorus ore, almost all of the associated rare earth enters into the phosphorus slag phase but does not enter into the ferrophosphorus or gas phases. Amorphous calcium metasilicate and calcium fluosilicate are major components of phosphorus slag, and rare earth mainly exists as a calsil solid solution. Hydrochloric acid was used for acidolysis of the phosphorous slag.Under the following conditions, 96% of the rare earth in the phosphorous slag can be dissolved in the acidolysis solution: acid excess coefficient of 1.5, reaction time of 50 min and reaction temperature of 50℃. The rare earth in the acidolysis solution was separated and recycled using oxalic acid as a precipitator and NaOH as a pH modifier. At pH of 1.7, rare-earth-enriched matter with rare-earth content of 2.1 wt% was obtained, and the recovery of the rare earth was 88%.     

Recovery of rare earths from ion-absorbed rare earths ore with MgSO4-ascorbic acid compound leaching agent

The magnesium sulfate leaching technology for the ion-absorbed rare earths ore can solve the ammonia pollution problem existing in ammonium sulfate leaching process. However, the leaching capacity of magnesium sulfate is slightly weaker than that of ammonium sulfate, resulting in a bigger consumption of magnesium sulfate. In this paper, the MgSO_4-ascorbic acid compound leaching agent had been demonstrated to deal with the ion-absorbed rare earths ore. The ascorbic acid could form a stable coordination with rare earth ions, so that it can strengthen the leaching of ion-exchangeable phase.Moreover, ascorbic acid has a strong reductive property, it can leach the colloidal sediment phase rare earth as well. The present study investigates the effect of the initial pH and the composition of leaching agent on the rare earth leaching. It is determined that the rare earth leaching efficiency is 107.5% under the condition of pH 2.00,0.15 mol/L magnesium sulfate and 1.0 g/L ascorbic acid in leaching agent. In this case, the content of the ion-exchangeable phase and colloidal sediment phase rare earth in the leaching residues are both only 0.02‰. The leaching efficiency of colloid sediment phase rare earth can be 85.7%,so that the Ce partition in the leaching liquor increases to be 5.77%. The magnesium-ascorbic acid compound leaching agent is proposed to be a promising choice to deal with the ion-absorbed rare earths ore, which can realize the efficient leaching, low consumption of MgSO_4 and environmentally friendly leaching.     

重量法测定镧镍合金中稀土总量

准确测定镧镍合金中稀土总量,对于有效控制镧镍合金的生产技术和产品质量具有重要意义。因镧镍合金中镍含量在50%(质量分数,下同)以上,其他共存元素中钴约10%、锰约5%,故很难通过单一分离方式彻底分离共存元素。实验依次采用氟化分离、氨水分离、草酸沉淀方式分离共存元素,进而对镧镍合金中稀土总量的测定进行探讨。试样经盐酸和硝酸溶解,采用氢氟酸、氨水、草酸沉淀稀土,逐一分离去除干扰元素,在pH值为1.8~2.0条件下,稀土元素沉淀为草酸稀土,950℃灼烧草酸稀土生成稀土氧化物(不含氧化钍),再以镧对氧化镧换算成金属稀土总量。盐酸-硝酸能够完全平稳溶解试样,且测定结果(30.42%)与参考值(30.43%)相符;采用氟化分离、氨水分离、草酸沉淀的分离方式很好地去除了镍、钴、锰、铝、铜、铁等非稀土杂质;按照实验方法测定镧镍合金样品中稀土总量,结果的相对标准偏差(RSD,n=11)均小于0.50%;加标回收率为 99%~101%。按照实验方法选取两家实验室对镧镍合金中稀土总量进行测定数据比对,结果基本一致并与参考值相符。     

重量法测定镧镍合金中稀土总量

准确测定镧镍合金中稀土总量,对于有效控制镧镍合金的生产技术和产品质量具有重要意义。因镧镍合金中镍含量在50%(质量分数,下同)以上,其他共存元素中钴约10%、锰约5%,故很难通过单一分离方式彻底分离共存元素。实验依次采用氟化分离、氨水分离、草酸沉淀方式分离共存元素,进而对镧镍合金中稀土总量的测定进行探讨。试样经盐酸和硝酸溶解,采用氢氟酸、氨水、草酸沉淀稀土,逐一分离去除干扰元素,在pH值为1.8~2.0条件下,稀土元素沉淀为草酸稀土,950℃灼烧草酸稀土生成稀土氧化物(不含氧化钍),再以镧对氧化镧换算成金属稀土总量。盐酸-硝酸能够完全平稳溶解试样,且测定结果(30.42%)与参考值(30.43%)相符;采用氟化分离、氨水分离、草酸沉淀的分离方式很好地去除了镍、钴、锰、铝、铜、铁等非稀土杂质;按照实验方法测定镧镍合金样品中稀土总量,结果的相对标准偏差(RSD,n=11)均小于0.50%;加标回收率为 99%~101%。按照实验方法选取两家实验室对镧镍合金中稀土总量进行测定数据比对,结果基本一致并与参考值相符。     

EDTA滴定法测定稀土铝中间合金中稀土总量

准确测定稀土铝中间合金中稀土总量,对于有效控制稀土铝中间合金的生产技术和产品质量具有重要意义。用400g/L氢氧化钠溶液溶解试样,此时,稀土与氢氧化钠反应生成氢氧化稀土沉淀,而铝与氢氧化钠反应后以偏铝酸根的形式留在了试液中,过滤,实现了铝与稀土元素的分离;用盐酸溶解沉淀,加入氢氟酸,此时稀土和氢氟酸反应生成氟化稀土沉淀,而铁与氢氟酸反应形成络合物留在溶液中,过滤,实现了干扰元素铁与稀土元素的分离;加入盐酸和高氯酸溶解沉淀,用抗坏血酸还原残留铁(III),乙酰丙酮溶液掩蔽残留的少量干扰元素铝,控制pH 5.5,以二甲酚橙作指示剂,用EDTA标准溶液滴定至溶液由红紫色变为亮黄色即为终点,建立了EDTA滴定法测定稀土铝中间合金中稀土总量的方法。将实验方法用于稀土铝中间合金(镧铝、钐铝、铒铝、钇铝)试样中稀土总量的测定,并在试样中分别加入不同量的于950℃马弗炉中灼烧过的高纯氧化镧、高纯氧化钐、高纯氧化铒和高纯氧化钇试剂进行加标回收试验,结果的相对标准偏差(RSD,n=11)不大于0.30%,加标回收率为99.6%~100.4%。选取镧铝、钐铝试样,按照实验方法测定其中稀土总量,并采用国标GB/T 31966—2015中的草酸盐重量法进行方法比对试验,测定结果基本一致。     

Rare earth recovery from fluoride molten-salt electrolytic slag by sodium carbonate roasting-hydrochloric acid leaching

Fluorinated rare earth molten-salt electrolytic slag contains a considerable amount of rare earth elements,as well as a variety of heavy metals and fluorides that cause environmental pollution.Therefore,it is of great importance to fully utilise this resource.In this study,the transformation mechanism of fluorinated rare earth molten-salt electrolytic slag roasted with sodium carbonate,and the regulation mechanism of rare earth leaching under different roasting conditions were investigated with ...     

Extraction and separation of yttrium from other rare earths in chloride medium by phosphorylcarboxylic acids

Two phosphorylcarboxylic acids, 3-((bis(2-ethylhexyloxy))phosphoryl)propanoic acid (PPA) and 3-((bis(2-ethylhexyloxy))phosphoryl)-3-phenylpropanoic acid (PPPA), were synthesized for separating yttrium from other rare earths in the chloride feed of ion-adsorption type rare earth concentrate. The effect of the factors such as pH_1/2, temperature, saponification degree and phase modifiers was investigated. The separation efficiencies of PPA and PPPA are obviously better than the typical extractants such as sec-octylphenoxy acetic acid (CA-12) and naphthenic acid (NA). The extraction process of rare earths by PPA and PPPA is a cation exchanging reaction, which is similar to those of CA-12 and NA. The loaded rare earths in both PPA and PPPA systems can be effectively back-extracted by 0.5 mol/L HCl or higher concentration. A cascade extraction process for separating yttrium from other rare earths was developed using PPPA as the extractant. The yttrium product with the purity of 97.20 wt% was obtained by 35 stages of extraction and 12 stages of scrubbing.     

Oxidative Roasting–Selective Pressure Leaching Process for Rare Earth Recovery from NdFeB Magnet Scrap

To recover rare earths (RE) with low acid consumption and low environmental pollution, selective pressure leaching with hydrochloric acid from roasted NdFeB scrap was explored. The phase evolution of NdFeB scrap during roasting at 800 °C as a function of time was confirmed, and after complete oxidation, its phase components consisted of Fe2O3, NdFeO3, and NdBO3. In the selective pressure leaching procedure, the optimal leaching was achieved at 110 °C for 30 min, in which the leaching rate of rare earth was 96.27% along with 13.33% of Fe. Subsequently, the effects of the hydrochloric acid dosage, the hydrochloric acid concentration and the particle size of the roasted NdFeB powder on the leaching rate of rare earth were investigated. For leaching at 110 °C for 30 min, the leaching of 13.33% Fe2O3 was derived from the Fe2O3 and NdFeO3 phases in the fully oxidized NdFeB scrap. This phenomenon was verified by the leaching of Fe from Fe2O3 of analytical purity and synthetic NdFeO3. Moreover, the leaching of Nd and Fe from the NdFeO3 phase was found to occur simultaneously. The advantages of the selective pressure leaching process using hydrochloric acid for the oxidized NdFeB scrap were comprehensively evaluated.     

Extraction and back-extraction behaviors of 14 rare earth elements from sulfuric acid medium by TODGA

The unique physical and chemical properties of rare earth elements lay the foundation for their extensive application. N,N,N',N' Tetra-octyl-3-oxopentanediamide(TODGA) is excellent in its ability of extracting rare earth elements and it is favored for green initiative. In this paper, the extraction and back-extraction of14 rare earth elements by TODGA were studied. Experiments show that in conditions of 6 mol/L sulfuric acid, the extraction temperature of 25 ℃,the phase ratio of 1:1 and 0.04 mol/LTODGA(aviation kerosene as the diluent), the extraction rates of 14 rare earth elements including lanthanum, cerium, praseodymium,neodymium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium were 99.00%-99.73%. Mixed with hydrochloric acid and nitric acid(HCl 3.5 mol/L, HNO_30.5 mol/L), the recoveries of the 14 rare earth elements are 91.52%-99.91% when the extraction temperature is 25 ℃ and the ratio is 1:1. The following application is based on the optimum conditions above with practical samples(from the roasting production line of China North Rare Earth High-tech Company Limited) for extraction and back-extraction experiments. Experiments show that TODGA has excellent enrichment effect on 14 rare earth elements, the extraction rates are 91.36%-99.80%, the back-extraction rates are 87.29%-99.64% and the total recoveries are 81.19%-99.44%.     

Recovery of rare earth and cobalt from Co-based magnetic scraps

The reuse of RE and cobalt in Co-based magnetic scraps was studied.The optimized feat lixiviated condition was:200 mesh,sulfuric acid dosage was of 1.4 times theoretic dosage,temperature was 80 oC and leaching time 1 h.The optimum technology conditions was:Na2S2O8 dosage was of 8 times theoretic dosage,oxidation temperature 80 oC,oxidation time 2 h and pH=4.5.Rare earth was precipitated by saturated(NH4)2C2O4 solution,after roasting of rare earth oxalate,rare earth oxide was received.Cobalt-iron residue was soaked by hydrochloric acid,the Fe(OH)3 was preferential solution,pH was adjusted to 1.4 by hydrochloric acid,Co(OH)3 did not dissolve,cobalt and iron were separated,after roasting of Co(OH)3,cobalt oxide was received.The total recovery of cobalt was found to be 97% and rare earths was 96%.     

Recovery of yttrium from deep-sea mud

Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H~+concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4:1 and room temperature 25 ℃(only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 ℃). Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204,15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y~(3+) and 42.60% Fe~(3+) are extracted from sulfuric acid leaching liquor(adjusted to pH = 2.0) after seven-stage counter current extraction with O/A ratio of 1:1 at room temperature, while other metals ions such as Al~(3+), Ca~(2+), Mg~(2+)and Mn~(2+) are almost not extracted. The Y~(3+) in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with O/A ratio of 10:1 at room temperature, while only 2.26% co-extracted Fe~(3+) is stripped. The Y~(3+) of loaded strip liquor can be precipitated by oxalic acid to further separate Y~(3+) and Fe~(3+). The precipitation efficiency of Y~(3+) in loaded strip liquor can be 98.56% while Fe~(3+) is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 ℃ for 3 h to obtain the oxide of Y in which the purity of Y_2 O_3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%.Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting,the yttrium yield is 82.04%.     

间接碘量法测定稀土硫化物中硫

试验提出了一种用间接碘量法测定稀土硫化物中硫含量的方法:稀土硫化物易与盐酸反应生成硫化氢,而硫化氢气体易和碘反应,故用已知浓度和用量的碘标准溶液完全吸收硫化氢气体,再用已知浓度的硫代硫酸钠标准溶液滴定出未反应的碘标准溶液,从而间接计算出稀土硫化物中硫含量。通过溶剂的选择、碘标准溶液用量及反应摇动时间的研究,确定了适宜的反应条件。结果表明,在稀土硫化物中硫质量分数为10%～25%时的最佳反应条件是:用盐酸作为反应溶剂,0.1 mol/L碘标准溶液用量为35 mL,反应开始至滴定前的剧烈摇动时间为2 min。采用实验方法对稀土硫化物中具有代表性的Ce₂S₃、Sm₂S₃及La₂S₃这3种样品中的硫进行了测定,结果的相对标准偏差(RSD,n=11)小于1%。测定结果与高频红外吸收法及硫酸钡重量法的测定值基本相符。     

从废荧光粉中回收稀土的工艺研究

研究了从废荧光粉(REO^12.00%)中回收稀土元素的工艺。采用碳酸钠焙烧-酸浸出工艺回收废荧光粉中的稀土,研究了碳酸钠加入量、焙烧温度、焙烧时间以及浸出条件对稀土回收率的影响。研究结果表明,碳酸钠焙烧试验的最佳条件为碳酸钠与荧光粉焙烧比例1∶2,焙烧温度700℃,焙烧时间1 h;焙烧产物用盐酸浸出,浸出试验最佳条件:盐酸浓度、液固比、浸出温度、浸出时间分别为3 mol/L、10∶1、70℃、2 h,在上述焙烧及浸出最优条件下,稀土总回收率(REO)达97%以上。     

Electrolytic reduction of Eu(III) to Eu(II) in acidic chloride solutions with titanium cathode

The feasibility of a rare earth separation process by electrolytic reduction of Eu(III) with a titanium cathode was examined by cathodic polarization characteristics of Eu(III) on a titanium electrode and batch-type electrolytic reduction of Eu(III) using a bipolar electrolytic cell in acidic aqueous solutions of EuCl₃. The reduction of Eu(III) started at a cathode potential of about −0.6 Vvs standard hydrogen electrode (SHE). The plateau current for the reduction of Eu(III) was observed at around −1.2 Vvs SHE, but a further decrease in cathodic potential resulted in a decrease in the reduction current, which was caused by the hydrolysis of Eu(III). The plateau current is a diffusion-limiting current in the reduction of Eu(III). In the batch-type electrolytic reduction of Eu(III) using a bipolar electrolytic cell, complete reduction of aqueous 0.1 kmol m⁻³ EuCl₃ solution with a current efficiency of over 0.6 could be achieved by keeping the catholyte pH at 2, to avoid hydrolysis of Eu(III). The final percent Eu(III) reduction of the solution from an industrial europium purification process, which contained other rare earths, was lower than that of a synthetic EuCl₃ single electrolyte solution probably because of a more significant hydrolysis of rare earth ions. However, the final percent reduction increased with decreasing reduction current, the concentration of rare earths, and the viscosity of solution.     

Non-ammonia enrichment of rare earth by magnesium oxide from rare earth leaching liquor in magnesium salt system

In order to solve the problem of ammonia-nitrogen pollution in the enrichment process of the ionadsorption type rare earth ore,the technology of non-ammonia precipitation with magnesium oxide precipitant was carried out.It is determined that the rare earth precipitation efficiency is 99.6% and the purity of rare earth concentrates is only 85.89 wt%under the optimum precipitation conditions.And the contents of MgO,SO_3 and Al_2O_3 in the rare earth concentrates are 5.12 wt%,6.77 wt%and 1.78 wt%,respectively.Furthermore,the thermo-decomposition process of precipitates was investigated by TGDSC,XRD and FI-IR.The thermal decomposition process consists of two stages:the dehydration of rare earth hydroxide and alkaline rare earth sulfate within 900 ℃ and the thermal decomposition of RE_2O_2SO_4 at 900-1300 ℃.Therefore,a high-temperature calcinations method for removing SO_3 from precipitates is proposed.When the precipitates are calcined at 1300 ℃ for 2 h,the rare earth concentrates with a purity of 92.03 wt%can be acquired.Moreover,the content of SO_3 in the concentrate is only 0.46 wt%.In the MgO precipitation and high-temperature calcinations process,the raw material cost is low and the quality of rare earth concentrates is acceptable.It could have great significance for nonammonia enrichment of rare earth from the rare earth leaching liquor,and finally solve the problem of ammonia nitrogen in the extraction process of the ion-adsorption type rare earth ore within magnesium salt system.     

还原酸浸对废旧稀土荧光粉中稀土提取的影响

为解决废旧稀土荧光粉中高价态Ce、Tb氧化物浸出困难的难题, 在碱熔焙烧预处理的研究基础上, 采用还原酸浸的方法, 以抗坏血酸作为还原剂, 来提高废旧稀土荧光粉的稀土浸出率。实验表明:在HCl浓度为4 mol/L, HCl与水洗渣液固比(单位为:mL/g, 下同)为10:1、抗坏血酸用量为10%、温度为338 K、时间为120 min、搅拌转速为650 r/min的条件下, 稀土浸出率可以达到98%以上。      

Recovery Behavior of Rare Earth from Bayan Obo Complex Iron Ore

A novel process is presented for recovering rare earth from Bayan Obo complex iron ore. The iron ore was reduced and melting separated to produce iron nugget and rare-earth-rich slag. In order to investigate the influence of cooling rate on mineral components, especially the enrichment behavior of RE-containing mineral, the slag was remelted at 1673 K (1400 °C) and the liquid slags were cooled using three types of cooling conditions, water quenching, air cooling, and furnace cooling. Subsequently, the slags were leached by hydrochloric acid to evaluate the relations between leaching efficiency of rare earth and cooling conditions. The results indicated that the slags under different cooling conditions mainly contained fluorite, cefluosil, and cuspidine. The rare-earth mineral is more fully crystallized when the cooling rate of the liquid slag was decreased. The proportion of Ce (III) to Ce (IV) increases with the increase of heating time and decrease of cooling rate. It has been found that the influence of cooling rate on the leaching rate of the rare earth is slight. From water quenching to furnace cooling, the leaching rate of rare earth increases from 97.00 pct to 99.48 pct. After being filtered, filtrate can be used to produce rare-earth chloride. Leached residue, with CaF₂ of 64.45 pct and ThO₂ of 0.05 pct, can be used to recover CaF₂ and extract nuclear source material.     

Processing of xenotime concentrate

Xenotime is a rare earth phosphate mineral which is a rich source of yttrium and heavy rare earths. Earlier experimental studies have been carried out in this laboratory on the chemical processing of hand-sorted xenotime obtained from the Bihar region to rare earth oxide intermediates. In addition to the deposits of xenotime in the Bihar region there are large volumes of placer deposits of rare earths containing both monazite and xenotime in the Siri river basin of Madhya Pradesh. Atomic Minerals Division is operating a pilot plant for the beneficiation of rare earths from these Siri river deposits. A low grade (typically analysing 45% light rare earth oxide, 3.4% Y₂O₃ and 2.3% heavy rare earth oxide) and intermediate grade (analysing 18.5% light rare earth oxide, 19.3% Y₂O₃ and 8.7% heavy rare earth oxide) concentrate is routinely being produced. The paper reports experimental studies involving alkali leaching and alkali fusion studies to recover rare earth oxide intermediates from low and intermediate grade deposits from Madhya Pradesh. It has been shown possible to extract almost 95% of rare earths by these processes.     

三溴偶氮胂分光光度法测定镁合金中稀土总量

采用三溴偶氮胂分光光度法,以盐酸分解含单一或混合轻稀土镧、铈、镨、钕和中稀土钐、钆的镁基合金,25 mL溶液中0.6 g/L显色剂用量为3～8 mL,盐酸浓度为0.5～1.0 mol/L,在640 nm波长下测定了镁基合金中的稀土总量。基体镁对测定无干扰。轻、中稀土总量的质量浓度在0.2～0.8 μg/mL范围内与吸光度呈线性,相关系数R²在0.999以上,表观摩尔吸光系数ε_RE为(1.10～1.19)×10⁵ L·mol^-1·cm^-1。按照实验方法测定各类稀土镁合金样品中稀土总量,结果的相对标准偏差(RSD,n=6)不超过1.6%;并与电感耦合等离子体原子发射光谱法(ICP-AES)测定结果相一致。     

Process mineralogy of Weishan rare earth ore by MLA

Mineral liberation analyser (MLA) was applied to quantitatively analyze the rare earth ore from Weishan in Shandong. Mineralogy parameters, such as mineral composition, occurrence states of rare earth elements (REEs) and valuable elements, mineral embedded grain size distribution, mineral association and liberation, are obtained. Results show that the contents of REEs and other valuable elements mainly contained in the ore were La 1.02 wt%, Ce 4.29 wt%, Pr 0.34 wt%, Nd 0.84 wt%, Sr 3.4 wt% and Ba 26.53 wt%, respectively. The REEs mainly occur in bastnaesite and carbocernaite in the form of independent mineral and the contents of bastnaesite and carbocernaite in the ore were 5.96 wt% and 12.30 wt%, respectively. 67.34% of strontium occurs in carbocernaite and the rest occurs in celestobarite and strontianite mineral. 92.71% of barium occurs in barite. Liberation of main rare-earth minerals such as bastnaesite and carbocernaite is more than 80% when the grinding fineness is 78.42% passing 74 μm. The research results could be employed to provide detailed basic theoretical data for further improvement of the beneficiation process flow and the processing index of rare earth ore, the recycling of other valuable minerals and the comprehensive utilization of tailings.