从钕铁硼废料中提取稀土工艺研究

采用氧化焙烧-盐酸分解法,研究从钕铁硼废料中提取稀土的工艺条件,探讨了焙烧温度和时间对铁的氧化率的影响,在浸出过程中考察了盐酸浓度、反应时间、反应温度以及液固比对稀土浸出率的影响,并分析了pH值和陈化时间对浸出液除杂效果的影响.结果表明:在700℃焙烧1.5 h,铁的氧化率最高,铁基本完全氧化成三价铁,在最佳浸出条件下稀土浸出率高达到99.33%,浸出液中和除杂时,调节pH值为3.5,陈化时间大于2 h,料液中非稀土杂质含量低,特别是铁仅为0.0014 g/L,浸出液完全达到稀土萃取的要求.      

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.     

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 ...     

Selective extraction and recovery of rare earth metals from waste fluorescent powder using alkaline roasting-leaching process

Waste management of rare earth metals(REMs) containing materials and recycling of rare earth metals(REM) from waste materials are becoming more and more important due to high demand and resource exhaustion. However, extraction of REM from waste fluorescent powder materials is difficult because of their special aluminate structure. A novel "alkaline roasting-acid leaching" process was developed in this study. The alkaline roasting process mechanism was examined using differential thermal analysis(DTA)-thermogravimetric(TG) measurements, and the roasting product was characterized by XRD analysis. In this process, Al_2O_3 was converted into water soluble NaAlO_2 via alkaline roasting, and NaAlO_ 2 in the roasting product could be easily dissolved in water, while the rare earth oxide(REOs) remained as solid. After filtration, REOs cake was leached using hydrochloric acid to achieve 99.8% of REM recovery. It was concluded that the alkaline roasting-acid leaching process could effectively separate Al_2O_3 and REOs with high REM recovery.     

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。     

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。      

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。     

Catalytic oxidation of formaldehyde over CeO_2-Co_3O_4 catalysts

A series of CeO_2-Co_3O_4 mixed oxide catalysts with different Co/(Co+Ce) atomic ratios were synthesized by citric acid sol-gel method and used for catalytic oxidation of formaldehyde(HCHO). Many techniques such as Brumauer-Emmett-Teller(BET), X-ray diffraction(XRD), scanning electron microscopy(FE-SEM), temperature programmed reduction(H_2-TPR), temperature-programmed desorption(O_2-TPD) and X-ray photoelectron spectroscopy(XPS) were used to characterize catalysts. The results of catalytic performance tests showed that the catalyst CeO_2-Co_3O_4 with Co/(Co+Ce) ratio of 0.95 exhibited the best performance, and the temperature of complete oxidation of HCHO was 80 oC. The analytical results indicated that the addition of CeO_2 enhanced the specific surface area of Co_3O_4 and the fine dispersion of both of them. Moreover, the strong interaction between CeO_2 and Co_3O_4 resulted in the unique redox properties, which enhanced the available surface active oxygen and led to high valence state of cobalt oxide species. All those effects played crucial roles in the excellent performance of CeO_2-Co_3O_4 for the HCHO oxidation.     

Heavy metals in the environment. Part VI: Recovery of cobalt values from spent cobalt/manganese bromide oxidation catalysts

Cobalt is recovered from a series of spent cobalt/ manganese bromide oxidation catalysts containing 27–31% Co, 25–33% Mn, 0–14% Fe together with Cr, Cu and Ni. While ammoniacal leaching in the presence of reducing agents can be used to extract cobalt, the process has to be separately optimized for each sample. Leaching with 4 M HCl at 80°C for 4 hours, however, proved successful for all the catalysts. A method of successive neutralization is used for the separation of cobalt from the acid solutions. Addition of solid NaOH to pH 2 removes Fe and Cr as hydroxide, while addition of ammonia to pH 10 precipitates manganese oxide from an aerated solution leaving Co as a Co^III hexammine complex. Cobalt can be recovered from this solution by chemical or electrochemical processes. After crystallization the complex is converted to anhydrous cobalt chloride by heating it to 320°r to Co₂O₃ by roasting it in air at 500°C. Either of these materials may be readily converted into other cobalt chemicals. Alternatively, fluidized bed cell electrolysis of the Co^III. complex solution yields cobalt with purity > 99.5%.     

Effects of flaky rare earth oxide additives on the high temperature performance of nickel electrodes

Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the ...     

Iron recovery and rare earths enrichment from Bayan Obo tailings using Coal-Ca(O H)2-NaO H roasting followed by magnetic separation

The recovery of iron and enrichment of rare earths from Bayan Obo tailings were investigated using CoalCa(OH)_2-NaOH roasting followed by magnetic separation.The influences of roasting temperature,roasting time,coal content,milling time,Ca(OH)_2 dosage and NaOH dosage on the iron and rare earths recovery were explored.The results showed that the magnetic concentrate containing 70.01 wt.% Fe with the iron recovery of 94.34% and the tailings of magnetic separation containing 11.46 wt.%rare earth oxides(REO)with the REO recovery of 98.19% were obtained under the optimum conditions(i.e.,roasting temperature of 650°C,roasting time of 60 min,coal content of 2.0%,milling time of 5 min,and NaOH dosage of 2.0%).The Ca(OH)_2 dosage had no effect on the separation of iron and rare earths.According to the mineralogical and morphologic analysis,the iron and rare earths of Bayan Obo tailings could be utilized in subsequent ironmaking process and hydrometallurgy process.     

草酸盐湿式沉淀-煅烧分解法制备四氧化三钴及其表征

以氯化钴、草酸铵为原料,吐温80(Tween-80)为表面活性剂,通过湿式沉淀法合成氧化钴的前驱体,再通过热分解制备四氧化三钴。采用扫描电镜、X射线衍射仪、热分析仪分析了钴氧化物前驱体和钴氧化物的形貌、晶体结构和热分解等特征。结果表明:以草酸盐为沉淀剂制得的钴氧化物前驱体为CoC_2O_4·2H_2O,前驱体于600℃煅烧4 h后可得到较纯的四氧化三钴粉末,并且基本保持了前驱体原来的形貌,仍为针(棒)状,粒子边缘变得光滑。     

复杂稀有金属矿稀土回收新工艺

研究一种从不能用物理选矿法有效富集稀土的复杂稀有金属矿中回收稀土的工艺。原矿在酸矿质量比为1.2时于400℃酸化90min,然后在液固比5∶1、90℃浸出120min,稀土浸出率可以达到85.64%。浸出液经氧化、中和除杂后,按稀土理论用量1.2倍添加草酸。得到的草酸稀土沉淀在950℃煅烧60min,可获得REO含量92.4%的氧化稀土产品,全流程稀土总回收率为71.32%。     

复杂稀有金属矿综合利用新工艺

研究一种从复杂稀有金属矿中综合回收稀土、铌、钛的新工艺。按6∶5的酸矿质量比添加浓硫酸混匀后在400℃酸化,酸化渣浸出后,浸出液按1∶1的体积比加水在100℃水解60min得到水解沉淀,浸出渣采用强磁选分离得到磁性物及非磁性物。将水解沉淀与磁性物混匀在1 800℃还原熔炼,获得Nb2O5含量22.38%、铁品位52.32%的铌铁合金和TiO2含量35.12%的钛渣,铌、钛回收率分别为66.89%和50.38%。水解液在通入空气的条件下用氨水调节至pH=3进行固液分离,按理论量1.2倍添加草酸沉淀稀土,最后将该稀土沉淀在950℃煅烧60min,可得到REO含量92.4%的稀土氧化物,稀土总回收率71.32%。     

钇在钴基合金和硬质合金中的作用

对钴基合金和ＹＧ８Ｒ硬质合金进行了Ｘ射线衍射、ＳＥＭ、ＴＥＭ和ＥＤＳ的观察和分析。结果表明：稀土的加入对钴相的晶格参数没有影响，但使钴相的粒度显著变小，并使合金中ＷＣ相晶粒尺寸的不均匀和分布的不均匀得到明显改善；在Ｃｏ基（Ｃｏ－ＷＣ－Ｙ）合金中可形成的稀土相有稀土氧化物Ｙ２ＷＯ６和稀土金属经物Ｃｏ５Ｙ８和Ｃｏ２Ｙ。     

Rare earth oxide modified Cu-Mn compounds supported on TiO₂ catalysts for low temperature selective catalytic oxidation of ammonia and in lean oxygen

Selective catalytic oxidation(SCO) of ammonia was carried out over Cu-Mn compounds catalysts modified with trivalent rare earth oxide Ce2O3 and La2O3 respectively.TiO2 was used as support and different ratio of O2 were tested in order to find an appropriate O2 concentration(vol.%),and the results showed that 1%O2(vol.%) was propitious to SCO of ammonia.The effects of the two rare earth oxides modified catalysts Ce2O3-Cu-Mn/TiO2 and La2O3-Cu-Mn/TiO2 on the catalytic activity and selectivity of ammonia oxidation were investigated under the reaction condition of 500 ppm ammonia,1%O2(vol.%),at the temperature from 125 to 250 oC.The results revealed the beneficial role of Ce2O3 and La2O3 in catalytic activity at low temperature and lean oxygen concentration,while the modification with Ce2O3 and La2O3 led to the negative influence on N2 selectivity.For the catalysts modified with Ce showed lower NO and N2O selectivity than the catalysts modified with La,then the effects of different Ce loadings on catalytic activity and selectivity were also considered,in combination with catalysts preparation methods,which include incipient wet impregnation,sol-gel method and co-precipitation.Results revealed that the catalysts prepared by sol-gel method obtained preferable catalytic activity compared with the others,reaching 99% ammonia at 200 oC,whereas 96% NO was detected.It also indicated that different catalyst preparation method significantly determined production distribution.     

某低品位复杂稀土精矿中提取稀土的研究

对某低品位复杂稀土精矿采用传统的浓硫酸低温焙烧工艺,可以较好的浸出稀土和铍,浸出率分别达到95%和90%以上,但钽、铌浸出率只能达到40%左右;采用添加活化剂后,可使钽铌的浸出率提高到80%,同时稀土和铍的浸出率也分别达到97%和99%;将水浸液采用添加草酸沉淀稀土,经过煅烧后成稀土氧化物后稀土总量达到86%,将稀土氧化物采用盐酸溶解后,通过调整pH值,除去部分杂质,采用碳铵沉淀稀土,得到碳酸稀土,非稀土杂质小于2%.     

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。     

自然氧化预处理钕铁硼废料浸出过程

为降低钕铁硼废料预处理成本,探讨利用盐酸润湿-空气自然氧化法对钕铁硼废料进行预处理,并对经盐酸润湿-空气自然氧化处理的钕铁硼废料中稀土的浸出工艺和浸出动力学进行研究.结果表明:以4 mol/L HCl润湿原料,在空气中放置20 d后铁的氧化率达到92.37 %,可满足铁硼废料中稀土回收的前期处理工艺要求,降低生产成本;在浸出的过程中,当反应温度为363 K,盐酸浓度为2 mol/L、粒度为0.055~0.088 mm、液固比V_L/W_S=8:1、搅拌速率500 r/min下,反应时间为60 min后经盐酸润湿-空气自然氧化Nd-Fe-B废料中稀土的浸出率可达89.36 %;研究表明,钕铁硼废料中稀土浸出过程主要是受扩散控制,其表观化学反应活化能E=17.49 kJ/mol.