Agitation leaching of rare earth elements from phosphogypsum by weak sulfuric solutions

It has been shown that the processes of the recovering rare earth elements from phosphogypsum using agitation leaching by solutions that contain 2–10 wt % H₂SO₄ have poor economic prospects.     

铜尾矿浮选明矾石精矿中有价元素直接碱浸动力学及过程强化

作为一种多元素矿物,紫金山铜尾矿浮选明矾石精矿有望成为铝、钾和镓等元素的替代资源。相对于传统工艺,KOH溶液直接浸出明矾石精矿可以避免高能耗的热分解过程,同时降低杂质离子的干扰。本工作研究了铜尾矿浮选明矾石精矿在KOH溶液中的直接浸出行为特性,重点研究了不同碱浓度和温度下精矿中多元素浸出率随时间的变化规律,并结合动力学分析阐明了精矿直接碱浸反应的控制步骤;在此基础上,引入机械活化促进精矿中有价元素的高效浸出。结果表明,在实验条件下精矿直接碱浸过程中仅发生明矾石相的分解;提高KOH浓度和浸出温度可使元素浸出速率快速增加;根据经典的液-固反应收缩核模型的动力学理论,分析发现浸出反应符合化学反应步骤控制。机械活化使精矿粒径降低、比表面积增加、非晶化程度提高,从而使精矿的反应活性增强,使铝、钾和镓的浸出速率提高。     

硼精矿钠化焙烧-水浸制取硼砂

以硼精矿为原料、Na₂CO₃为钠化剂,在TG-DTA热分析基础上,研究了硼精矿钠化焙烧-水浸制取硼砂过程中Na₂CO₃用量、焙烧温度、焙烧时间、成型压力对B₂O₃浸出率的影响,采用X射线衍射和扫描电镜对硼精矿钠化焙烧产物和硼砂制品的相组成和显微形貌进行了表征分析。结果表明：在5倍Na₂CO₃理论用量、样品成型压力5 MPa、温度850℃、保温3 h最优条件下,硼精矿中主要含硼矿物硼镁石[MgBO₂（OH）]转变为可溶性硼酸钠盐Na₃BO₃和Na₂B₄O₇,实现了硼矿物活化和碱解过程同步完成。焙烧产物经常压水浸,B₂O₃浸出率达91.05%。水浸滤液经除杂、蒸发、浓缩后获得了结晶良好的硼砂制品。     

磷精矿中P2O5浸出工艺研究

针对贵州某磷矿浮选的磷精矿,研究了磷酸质量分数、硫酸化学计量比、温度、液固比对磷精矿中P2O5浸出率的影响,得出合理的浸出工艺为;磷酸质量分数23%,硫酸化学计量比1.1,温度80℃,液固比4∶1.在此条件下P2O5浸出率为86.84%.     

Selective copper–iron dissolution from a molybdenite concentrate using bacterial leaching

The present research reports on the selective dissolution of copper and iron from a Chilean molybdenite concentrate using mesophilic, moderate and extreme thermophilic culture bacteria. From the results obtained it is deduced that molybdenite is not attacked by any of the above mentioned microorganisms, whereas the attack of the copper–iron species is dependent on various experimental conditions: pH, potential, pulp density, or addition of silver as catalyst. Optimal copper–iron dissolution is obtained using extreme thermophilic microorganisms and low pulp density (2% w/v). Total selective dissolution of chalcopyrite is achieved which leads to a pure molybdenite concentrate being obtained. © 2001 Society of Chemical Industry     

Rare earth silicate environmental barrier coatings: Present status and prospective

Due to drastic decreasing in mechanical properties at relative high temperature, traditional nickel based super alloys are replaced by Si-based non-oxide ceramics in the application of high temperature aero-engines. In order to reduce the spallation and deformation of aero-engine blades in the environment containing high temperature water vapor and oxygen, protection coatings on the surface of the ceramics are required. Owing to high temperature stability, superior oxidation resistance and corrosion resistance properties, rare earth (RE) silicates are promising as candidates and play an important role in improving the high-temperature mechanical/thermal properties of Si-based non-oxide ceramics. In this review, recent progress in the research and development of environmental barrier coatings (EBCs) are summarized. Development of EBCs is presented, and the multi-scale structures and properties of each part are introduced. In addition, the merits and demerits of each preparation technique are discussed. As a promising candidate for the application in high temperature aero-engines, Si/mullite/Lu₂Si₂O₇–Lu₂SiO₅ EBCs are highlighted.     

Preparation of high-purity graphite from a fine microcrystalline graphite concentrate: Effect of alkali roasting pre-treatment and acid leaching process

Removal of silicate minerals from microcrystalline graphite ores is important to achieve high-purity graphite product. Alkali roasting pre-treatment and acid leaching process was used to prepare high-purity graphite from a fine microcrystalline graphite concentrate. The results showed that the alkali roasting pre-treatment and acid leaching process could enhance the fixed carbon of microcrystalline graphite to a higher level. Under the optimum conditions selected, a graphite product with fixed carbon content of 99.0% was obtained from microcrystalline graphite concentrate with carbon content of 90.2%. According to XRD and SEM-EDS analysis, impurities mainly composed of Fe, Si, and Al were decomposed to water soluble or acid soluble components during alkali-roasting pre-treatment and acid leaching process. The crystal structure and surface topography of microcrystalline graphite showed no change.     

混合铵盐用于风化壳淋积型稀土矿浸取稀土的动力学研究

采用柱浸工艺对风化壳淋积型稀土矿浸取稀土的动力学进行了研究.通过对淋洗剂的配比的优化,证明采用氯化铵和硫酸铵比例为7:3的混合铵盐作为淋洗剂浸取稀土的效果最佳.考察了淋洗剂质量分数、淋洗液固比、淋洗速度及矿石粒度对浸取率的影响.并进行了浸取动力学分析.结果表明.其浸取过程可定性地用Fick定律描述.且较好地符合收缩未反应芯模型;当淋洗荆质量分数低于2.5%时.动力学控制步骤为混合控制;当淋洗剂质量分效达到2.5%后,其浸取动力学属内扩散控制.动力学方程为1-2/3η-(1-η)2/3=e6.105R0.21189t.     

Rare earth (RE) doped phosphors and their emerging applications: A review

The evolution of luminescent materials has witnessed rapid advancement in research and development. Solid inorganic light-emitting materials or phosphors are the optoelectronic material of the 21st century because of their power-efficient potential over various illumination sources, eco-friendliness and resourceful display perspectives. The inorganic phosphors have been extensively explored to meet the demand of low voltage stimulated lighting sources owing to increased global energy consumption. Due to environmental friendliness, advantages long lifetime, lower energy consumption, reliability and high luminous efficiency, modern white light-emitting diodes (WLEDs) have replaced less effective incandescent and mercury-enclosing conventional fluorescent lighting sources. This review highlights the developments in preparation, luminescence and potential perceptions of rare-earth activated phosphors for solid-state lighting technologies. The role of RE ions as an activator as well as a sensitizer in doped materials and possible transitions within their energy levels are reviewed in detail. The paper reviews the substantial influence of host lattices such as aluminate, oxide, phosphate, silicate, sulfide, etc on the optical transitions of doped RE ions. Studies on the advancement into the design of novel phosphors are very crucial as they will provide an opportunity to boom prospects in the course of promising applications. The sustainable energy facilities include clean technologies providing a cheaper lighting source which can produce significant indirect economic benefits via limiting the deforestation and use of scrubbing technology to mitigate air pollution.     

The separation of europium from a middle rare earth concentrate by combined chemical reduction,precipitation and solvent-extraction methods

The chemical reduction of pure europium(III) chloride solutions was investigated using reagents comprising reactive metals (Zn and Mg), metal amalgams (Zn-Hg, Na-Hg and Eu-Hg), metal hydride (NaBH₄) and nitrogenous reductants (N₂H₄ and NH₂OH). Using 100% excess of reducing agent and of ammonium sulphate, efficient precipitation of europium(II) sulphate was obtained with the metal amalgams (99·7–99·9%) and with zinc metal (99·8%), whereas only partial precipitation was obtained with magnesium metal (69%), and no precipitation was observed with the other reagents. Application of the method to synthetic rare earth chloride solutions containing europium 7·5, neodymium 5, samarium 35 and gadolinium 20 g dm⁻³ gave efficient precipitation of europium(II) sulphate with zinc and europium amalgams, but no selective precipitation with sodium amalgam. Reduction of an authentic middle rare earth chloride solution with zinc amalgam gave 97·5% recovery of europium(II) sulphate containing (as a percentage of the total rare earths) europium 92, samarium 3·5, neodymium 2, cerium 1, praseodymium 0·6 and gadolinium 0·5%. Conversion of the europium(II) sulphate to europium(II) chloride, followed by re-precipitation of the sulphate increased the europium content only to 96·5%, whereas replacement of the re-precipitation by solvent extraction of the trivalent rare earth impurities into solutions of commercial organophosphorus or carboxylic acids in xylene increased the europium content to > 99·98%. The zinc ions introduced into the middle rare earth mother liquor during the reduction procedure can be removed by solvent extraction into a commercial phosphine oxide (Cyanex 925), without loss of rare earth values.     

Laboratory study of soil acidification and leaching of nutrients from a soil amended with various surface-incorporated acidifying agents

Granular S, finely-ground S, iron sulphate and aluminium sulphate were added at two rates to the surface (0–6 cm) of a soil and acidification and leaching of nutrients were measured over 12 months in a laboratory study. Iron and aluminium sulphate both rapidly lowered soil pH in the top 0–6 cm of the soil. There was little difference in soil pH after 3 and 12 months reaction of these two amendments. In contrast, for granular S and finely-ground S there were clear decreases in soil pH between 3 and 12 months reaction with the soil. Finely-ground S was oxidized in the soil faster than granular S and therefore had a more acidifying effect. The top 0–6 cm of the soil was acidified by all the agents used but the deeper soil was less affected. The only treatments which lowered the pH of the 12–18 cm layer below pH 6 were the high rates of iron and aluminium sulphate. Soil acidification resulted in a decrease in exchangeable Ca, Mg and K, an increase in exchangeable Al and a decrease in effective CEC in the acidified soil layers.At both levels of addition, total ionic strength of percolates from the soil followed the order: aluminium sulphate = iron sulphate > finely gound S > granular S > control and was higher at the higher rate of addition. The pH values of percolates followed the order: control > granular S > finely ground S > iron sulphate = aluminium sulphate and were lower at the higher rate of addition. For the amended soils there was a very close relationship between the pattern and total amounts of SO ₄ ^2- and Ca²⁺ leached.It was concluded that granular S is not an effective acidifying agent since it is oxidized very slowly in the soil and that acidfying agents should be incorporated to the depth that acidification is required.     

粉煤灰中有价金属元素铝、镓、锂活化浸出提取研究进展

分析总结了粉煤灰焙烧活化、浸出及提取研究技术进展。焙烧主要有钠化焙烧、钙化焙烧和铵法烧结,混合助剂焙烧亦有所研究;浸出包括盐酸、硫酸酸浸和碳酸钠、氢氧化钠碱浸等方法;采用沉淀法、吸附法、萃取法、结晶法等对浸出液中铝、镓、锂进行提取回收;铝提取方法较成熟且已工业化生产,镓提取工艺尚不成熟仅停留在实验室阶段,锂提取研究相对较少且效果较差,有待进一步研究。鉴于提取单一元素成本较高、工艺重复等问题,建议从粉煤灰中提取有价金属时可多种元素综合提取,缩短工艺流程、减少污染、降低成本进而有利于工业化生产。     

粉煤灰中有价金属元素铝、镓、锂活化浸出提取研究进展

分析总结了粉煤灰焙烧活化、浸出及提取研究技术进展。焙烧主要有钠化焙烧、钙化焙烧和铵法烧结,混合助剂焙烧亦有所研究;浸出包括盐酸、硫酸酸浸和碳酸钠、氢氧化钠碱浸等方法;采用沉淀法、吸附法、萃取法、结晶法等对浸出液中铝、镓、锂进行提取回收;铝提取方法较成熟且已工业化生产,镓提取工艺尚不成熟仅停留在实验室阶段,锂提取研究相对较少且效果较差,有待进一步研究。鉴于提取单一元素成本较高、工艺重复等问题,建议从粉煤灰中提取有价金属时可多种元素综合提取,缩短工艺流程、减少污染、降低成本进而有利于工业化生产。     

Rare earth compounds modified carbon black filled powdered natural rubber: Preparation,morphology and properties

Ten types of rare earth (RE) compounds modified carbon black (HAF‐RE) were prepared using chemical‐deposit method, then HAF‐RE were mixed with natural rubber latex to prepare HAF‐RE filled powdered natural rubber [P(NR/HAF‐RE)] by a carbon black/rubber latex coagulation method. It is found that most of the P(NR/HAF‐RE) vulcanizates showed better mechanical properties, especially higher tensile modulus, and tensile strength, compared with none‐rare earth modified carbon black filled powdered natural rubber [P(NR/HAF)]. Dysprosium (Dy) modified carbon black (HAF‐Dy) filled powdered natural rubber [P(NR/HAF‐Dy)] was chosen for intensive investigation because of its better comprehensive mechanical properties. It is found that the adding of Dy compounds could help to get smaller particles with narrower particle size distribution, and results from the SEM analysis show that carbon black has been dispersed in rubber matrix uniformly with diameter of 50–150 nm. The TEM analysis showed that Dy compounds could obviously reduce the aggregation of primary particles of carbon black, and promote the dispersion of carbon black in P(NR/HAF‐Dy) particles. © 2008 Wiley Periodicals, Inc. JAppl Polym Sci 2008     

Blackheaded fireworm: Laboratory and field studies of its sex pheromone

Electroantennogram (EAG) responses of maleRhopobota naevana (Hübner), the blackheaded fireworm, to all of the monoene straightchain 12- and 14-carbon alcohols and acetates implicated (Z)-11-tetradecenl-1-ol (Z11–14OH) and its acetate (Z11–14Ac) as sex pheromone components.Z11–14Ac produced the strongest EAG response of all compounds tested. Gas chromatography-mass spectrometry (GC-MS) analysis of extract of female sex pheromone glands (SPG) confirmed the presence ofZ11–14OH (125 pg/female) andZ11–14Ac (600 pg/female) (all other monoenes had different retention times). In field tests, traps baited withZ11–14OH alone captured males, but traps baited withZ11–14Ac alone did not. Traps baited with a combination ofZ11–14OH andZ11–14Ac in various ratios did not produce better trap catches thanZ11–14OH alone. (Z)-9-Dodecen-1-ol acetate (Z9–12Ac), reported by others to be a field attractant, did not produce trap catch in our tests, but in combination withZ11–14 OH (982 in septa corresponding to 95:5 in vapor,Z11–14OH toZ9–12AC) produced a sevenfold increase in catch overZ11–14OH alone. IfZ9–12AC had been present in extract of SPG at 2–5% ofZ11–14OH, it would not have been detected in our GC-MS experiment. Rhopobota naevana (Hübner) Lepidoptera: Tortricidae: Olethreutinae.     

Non hygroscopic superphosphate fertilizer from apatite and hydrochloric acid

A method is described for the production of a nonhygroscopic fertilizer from apatite by treatment with hydrochloric acid.Apatite is acidulated with HCl to the stoichiometric level needed for generating dicalcium phosphate. The reaction product when mixed with ammonium sulphate sufficient to doubledecompose calcium chloride and dicalcium phosphate yields a nonhygroscopic product containing almost all phosphorus in the water-soluble form. Results of laboratory experiments conducted to determine the optimum conditions for the process, chemical properties of the material and its agronomic effectiveness are described. The studies were carried out with the intention of utilizing the reserve of apatite at Eppawala in Sri Lanka using indegenous raw materials.     

锌镀层稀土钝化处理及其在氯化钠溶液中的溶解

研究了锌镀层经铈盐、镧盐和镨盐溶液钝化处理,及其在中型０．５ｍｏｌ／Ｌ、ＮａＣｌ溶液中的电化学行为,并与重铬酸盐、钼酸盐钝化进行比较。铈盐钝化处理效果接近重铬酸盐钝化、镧盐、镨盐纯化优于钼酸盐钝化,锌镀层稀土钝化的机理在于生成稀土氯化物、氢氧化物沉淀、帽此降低镀层中锌的溶解速率,提高了镀层耐蚀性能。     

Kinetic studies of graphon and coal-char reaction with NO and O2: direct non-linear regression from TG curves

The reactions of carbonaceous materials (graphon and coal-char) with NO, O₂ and NO+O₂ were investigated by a thermogravimetric analysis (TGA). A method of direct non-linear regression of the kinetic equation was applied for a simultaneous calculation of the apparent activation energy, frequency factor and reaction order from a single TG curve of carbon gasification in various atmospheres. It was proven that the proposed calculation method is applicable for the calculation of kinetic parameters from overlapping processes. Calculations from TG curves of the above reactions demonstrate that NO-carbon and (NO+O₂)-carbon reactions contain two processes, while O₂-carbon is a single process. The reaction order of O₂-carbon is approximate 0.5, while the reaction orders of NO-carbon or (NO+O₂)-carbon reaction are dependent on the process and type of carbon. Graphon shows higher apparent activation energy than coal-char due to the pore structure and uncatalysed effects.