Insight into leaching of rare earth and aluminum from ion adsorption type rare earth ore: Adsorption and desorption

Clay minerals are inferred to be the primary host materials for ion-exchangeable rare earth in ion adsorption type rare earth ore(IAREO).During the rare earth leaching process,the adsorption and desorption reactions of the cations controlling the leaching process continue to occur at the clay minerals-leaching agent solution interface.In order to understand the leaching mechanism and behavior of rare earth and co-leached aluminum,adsorption,competitive adsorption,and desorption experiments were ...     

Enhanced Leachability of a Lean Weathered Crust Elution-Deposited Rare-Earth Ore: Effects of Sesbania Gum Filter-Aid Reagent

The enhanced leachability of rare-earth ore from the lean weathered crust elution-deposited rare-earth ores with ammonium sulfate solution as lixiviant and sesbania gum as a filter-aid reagent was elucidated and optimized with chromatographic plate theory. The effects of the flow rate, the concentration of lixiviant, the sesbania gum filter-aid reagent, and the lixiviant consumption on the leaching process were examined with column elution. The results show that the sesbania gum has a positive effect on the leaching process; the relationship between the height equivalent to a theoretical plate (HETP) and the leaching flow rate can be described by the van Deemter equation. There is an optimum flow rate in the leaching process. The optimum concentration of the sesbania gum in lixiviant was discovered. Moreover, sesbania gum added in lixiviant also reduces lixiviant consumption and promotes the optimum leaching flow rate. It provides a new approach to leaching the lean weathered crust elution-deposited rare-earth ores with high efficiency and low reagent consumption. The approach also can reduce the NH₄ ⁺-N pollution.     

A partial equilibrium model to characterize the precipitation of ferric ion during the leaching of chalcopyrite with ferric sulfate

A partial equilibrium model has been developed and used to characterize the conditions under which precipitation of ferric ion occurs during the dump leaching of chalcopyrite ores. The precipitates which have been considered include amorphous Fe(OH)₃, α-FeOOH (goethite), and Na⁺, K⁺, Ag⁺, Pb²⁺, and H₃O⁺ jarosites. Solution of the model equations makes possible the determination of the concentrations of the solution species during leaching of the mineral. The concentration product for Fe(OH)₃ (am) and α-FeOOH was calculated for changing solution concentrations and compared with the solubility product constants to determine when precipitation would be expected thermodynamically. The K⁺, Na⁺, Ag⁺, and Pb²⁺ concentrations that would be necessary to satisfy the solubility product constants for the corresponding jarosites were calculated for various initial concentrations and varying amounts of O₂ consumption. Formerly Graduate Assistant, Ames Laboratory USDOE and Department of Chemical Engineering, Iowa State University, Ames, IA 50011     

Dissolution behaviour of a beryl ore for optimal industrial beryllium compound production

This study involves the leaching of the beryl ore with sulphuric acid (H₂SO₄) solution for predicting optimal beryllium extraction conditions with the aim of assessing the importance of leachant concentration, reaction temperature and particle size on the extent of dissolution. A kinetic model to represent the effects of these variables on the leaching rate was developed. It was observed that the dissolution of beryl ore increases with increasing H₂SO₄ concentration, temperature, decreasing particle size and solid to liquid ratio. At optimal leaching conditions, 89.3% of the ore was reacted by 1.25?mol/L at 75°C temperature and 120 minutes with moderate stirring, where 1612.0?mg/L Be²⁺, 786.7?mg/L Al³⁺, 98.1?mg/L Fe³⁺ and 63.4?mg/L Ag⁺ were found as major species in the leach liquor. The unleached products constituting about 10.7% were examined by X-ray diffraction (XRD) and found to contain primarily, siliceous compounds such as Xonotlite, Antigorite, Chrysolite and Kaolinite.     

硫酸铵-碘化钾-十二烷基三甲基氯化铵微晶吸附体系浮选分离镉(Ⅱ)

研究了硫酸铵-碘化钾-十二烷基三甲基氯化铵微晶吸附体系浮选分离镉(Ⅱ)的行为及其与常见离子定量分离的条件。结果表明,在0.5 g (NH₄)₂SO₄的存在下,当体系中Cd²⁺、KI、DTMAC同时存在时,体系中形成的三元缔合物(DTMAC)₂(CdI₄) 沉淀被定量吸附在DTMAC ⁺·I^-微晶物质表面而被浮选至盐水相上,Cd²⁺被定量浮选,Co²⁺、Ni²⁺、Zn²⁺、Mn²⁺、Fe³⁺、Al³⁺等离子留在水相中而不被浮选,实现了Cd²⁺与这些离子的定量分离,据此建立了一种微晶吸附体系浮选分离Cd²⁺的新方法。通过扫描电镜图片确证了DTMAC ⁺·I^-微晶物质的产生,探讨了Cd²⁺的浮选分离机理。方法成功用于合成水样中Cd²⁺的定量浮选分离,浮选率为95.4%～105.3%。     

The corrosion of lead anodes in copper electrowinning

The steady-state corrosion rate of 0.4 pct As-10 pct Sb-Pb anodes in H₂SO₄ copper electro-winning electrolytes was studied. The corrosion rate increases markedly with increasing acid strength and current density, although the corrosion per pound of copper electrowon is affected only slightly by current density. Several ions such as Cu⁺², Mg⁺², Al⁺³, SiO₃ ^-2 and Na+ have no effect on the corrosion while Fe+S and Ni+2 ions have moderate inhibiting effects. Strong corrosion inhibition is brought about by introducing small amounts of Co*2 into the solution or by substituting a Ca-Pb alloy for the conventional antimonial lead anodes.     

The electrical conductivity of some liquids in the system CaF2+CaO+Al2O3

The conductivity of slags in the binary systems CaF₂+Al₂O₃, CaF₂+CaO and the ternary system CaF₂+CaO+Al₂O₃ has been measured, using a four-lead electrode technique at a frequency of 1 kHz. The cell design used ensured that only molybdenum metal was in contact with the slag at high temperature and that the slag was wholly contained in molybdenum. No frequency dispersion could be detected at frequencies between 0.8 to 10 kHz. It is suggested that the formation of complex ions (e.g. AlO₂F₂ ³⁻ and AlOF ₂ ⁻ ) might account for the observed effects in CaF₂+Al₂O₃, CaF₂+CaO+Al₂O₃ liquids as has been previously suggested. an oxide ion clustering mechanism may explain the conductivities found in CaF₂+CaO.     

Dissolution kinetics of malachite in ammonia/ammonium carbonate leaching

The leaching of oxide copper ore containing malachite, which is the unique copper mineral in the ore, by aqueous ammonia solution has been studied. The effect of leaching time, ammonium hydroxide, and ammonium carbonate concentration, pH, [NH₃]/[NH₄⁺] ratio, stirring speed, solid/liquid ratio, particle size, and temperature were investigated. The main important parameters in ammonia leaching of malachite ore are determined as leaching time, ammonia/ammonium concentration ratio, pH, solid/liquid ratio, leaching temperature, and particle size. Optimum leaching conditions from malachite ore by ammonia/ammonium carbonate solution are found as ammonia/ammonium carbonate concentrations: 5 M NH₄OH+0.3 M (NH₄)₂CO₃; solid/liquid ratio: 1:10 g/mL; leaching times: 120 min; stirring speed: 300 rpm; leaching temperature: 25 °C; particle size finer than 450 μm. More than 98% of copper was effectively recovered. During the leaching, copper dissolves as in the form of Cu(NH₃)₄⁺² complex ion, whereas gangue minerals do not react with ammonia. It was determined that interface transfer and diffusion across the product layer control the leaching process. The activation energy for dissolution was found to be 15 kJ mol⁻¹.     

Separation of cobalt from nickel in ammonia-ammonium carbonate solutions using pressurized ion exchange

High resolution pressurized ion exchange has been used successfully to study and separate the various cobalt and nickel complexes present in commercial ammonia-ammonium carbonate solutions produced by the Caron process. Using chromatographic elution from Dowex 50W-X8 (15–25 micron) resin with ammonium carbonate solutions, three cobalt species, identified as the purple carbonato tetrammine complex, [Co(NH₃)₄CO₃]⁺, the red carbonato pentammine complex, [Co(NH₃)₅CO₃]⁺, and the yellow hexammine complex [Co(NH₃)₆]³⁺, were separated from a single nickel species. Nickel sorption was found to be a strong function of pH, whereas sorption of the cobalt complexes was essentially independent of pH over a rather wide range, extending from ～pH 7.8 to 10. Distribution ratios for all species increased significantly with decreasing ammonium carbonate concentration. With ammonium carbonate solution at pH 9.5, the complexes were eluted in the following order: [Co(NH₃)₄CO₃]⁺, [Co(NH₃)₅CO₃]⁺, [Ni(NH₃)_6-x(H₂O)_x]²⁺, and [Co(NH₃)₆]³⁺. From 4 M (NH₄)₂CO₃, distribution ratios were 5.0, 7.5, 18, and 75 for the respective complexes identified in the order above. This study points out some of the difficulties and opportunities in developing a viable ion exchange process for the recovery and separation of these metal ions.     

硫氰酸铵-十四烷基三甲基溴化铵微晶吸附体系浮选分离铜

建立了硫氰酸铵-十四烷基三甲基溴化铵微晶吸附体系浮选分离铜的新方法。探讨了硫氰酸铵溶液用量、十四烷基三甲基溴化铵（TTMAB）溶液用量和酸度等因素对Cu²⁺浮选率的影响,讨论了Cu²⁺的浮选分离机理。结果表明,在最佳条件下,由Cu²⁺,SCN^-和十四烷基三甲基溴化铵阳离子(TTMAB⁺)形成的不溶于水的三元缔合物(TTMAB)₂ ［Cu(SCN)₄］被定量吸附在TTMAB⁺与SCN^-作用产生的微晶物质TTMAB⁺·SCN^-表面,且被浮选至水相上形成界面清晰的液-固两相,而Fe³⁺、Co²⁺、Ni²⁺、Cd²⁺、Mn²⁺、Al³⁺等离子仍然留在水相中,实现了Cu²⁺与这些离子的定量分离。据此建立了硫氰酸铵-十四烷基三甲基溴化铵微晶吸附体系浮选分离铜的新方法,进行了合成水样中Cu²⁺的定量浮选分离,浮选率为93.4%～103.6%。     

酶催化分光荧光法测定环境水中痕量铬(Ⅵ)

铬（Ⅳ）对血红蛋白模拟酶催化荧光体系具有强烈的猝灭作用, 据此建立了一种酶催化分光荧光法测定铬（Ⅳ）的新方法。研究了溶液酸度、L-酪氨酸浓度、血红蛋白浓度、H₂O₂浓度及反应时间等因素对体系的影响。在pH10.4的NH₃·H₂O-NH₄Cl缓冲溶液中, 当L-酪氨酸、血红蛋白和H₂O₂的浓度分别为1.4×10^-4mol/L、1.0×10^-6mol/L和3.5×10^-5mol/L时, 测定铬（Ⅳ）的线性范围为2.0×10^-6～1.0×10^-4mol/L, 检出限为1.1×10^-8mol/L。1000倍NO₃^-、SO₄^2-、Na⁺、K⁺、Cl^-、Br^-, 300倍PO₄^3-、Al³⁺、NH₄⁺, 50倍Mn²⁺、Mg²⁺、Fe²⁺、Cu²⁺, 1倍Fe³⁺对铬（Ⅳ）的测定没有干扰。干扰较大的Fe³⁺, 可加入过量的柠檬酸掩蔽。对浓度为4.8×10^-5mol/L的铬（Ⅳ）进行11次平行测定, 其相对标准偏差为2.8%。该法已成功地应用于环境水样中铬（Ⅳ）含量的测定。     

Improving luminescence and thermometric performance of Ba2CaWO6:Er3+ by tri-doping with Yb3+ and Na+

The Er³⁺doped double perovskite Ba₂ CaWO₆ crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio(FIR) of transitions from ² H_11/2 and ⁴ S_3/2to the lowered ⁴ I_15/2 level.However,the Ca²⁺vacancy defect caused by the charge difference between rare-earth ions and the substituted alkaline-earth ions gives rise to the non-radiative probability and limits the t...     

Role of monovalent co-dopants on the PL emission properties of YAI3（BO3）4：Ce3＋ phosphor

The cerium （Ce3＋） doped yttrium aluminium borate （YAB） phosphor was synthesized by modified solid state reaction. The phosphor＇s phase purity and its emission properties were studied using powder X-ray diffraction pattern and photoluminescence spectroscopy. The synthesized YAB had rhomobohedral crystal structure. The phosphor had two different excitation and emission spectra. By 325 nm excitation, the phosphor had emission at 373 nm and with 363 nm excitation; the phosphor gave violet-blue emission at 418 nm. The UV emission of the phosphor originated due to Ce3＋ ions at the yttrium site and violet-blue emission owing to Ce3＋ ions at non-regular sites viz., A13＋ and interstitial sites. The emission intensity of the phosphor was enhanced when monovalent ions （K＋, Na＋, and F） were added as co-dopants. The crucial role of ionic radii of monovalent co-dopants on the emission enhancement of the YAB：Ce3＋ phosphor was reported. Thermogravimetric study showed that the YAB possessed high thermal stability at up to 900 ℃.     

Tunable luminescence in co-doped Zn3Al2Ge2O10:Cr3+ by controlling crystal field splitting and nephelauxetic effect

Ce³⁺/Dy³⁺/Tb³⁺/Eu³⁺/Mn²⁺ and Cr³⁺ ions co-doped Zn₃Al₂Ge₂O₁₀ phosphor were prepared by a high-temperature solid-state method. X-ray diffraction patterns prove the cubic phase structure of prepared Zn₃Al₂Ge₂O₁₀ phosphor. Emission, excitation spectra and decay curves confirm the tunable luminescence. Different degrees of the decrease of emission FWHM in Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,RE (RE = Ce³⁺, Dy³⁺, Tb³⁺, Eu³⁺) and Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Mn²⁺ are observed. The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect, and the nephelauxetic effect is dominant. Therefore, the emission FWHM decreases with the increasing concentration of Mn²⁺/Tb³⁺/Eu³⁺ in Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺, and for Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Ce³⁺ and Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Dy³⁺, it is a constant. The variation of Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Tb³⁺ is more obvious than that of Zn₃Al₂Ge₂O₁₀:0.02Cr³⁺,Eu³⁺, because Tb³⁺ ion has smaller electronegativity. Thus, the tunable luminescence of Cr³⁺ can be realized by co-doping different ions. And these phosphors have potential applications in light-emitting diodes for plant growth.     

Doping effect of rare-earth (lanthanum,neodymium and gadolinium) ions on structural,optical, dielectric and magnetic properties of copper nanoferrites

Copper and rare earth-doped (RE = La, Gd, Nd) CuFe_1.85RE_0.15O₄ nanoferrites were prepared using the sonochemical method. The effective doping of rare-earth (La³⁺, Nd³⁺, Gd³⁺) ions with copper nanoferrites was confirmed by X-ray diffraction. The tetrahedral and octahedral sites of the nanoferrites were identified through the Fourier transform infrared spectra. The doping of rare-earth elements enhances the optical bandgap energy of the nanoferrites that are observed through Ultraviolet–DRS spectra. The oxidation state of the elements Cu 2p, La 3d, Nd 3d, Gd 3d, Fe 2p and O 1s was analyzed. Scanning electron microscopy images indicate a spherical morphology with agglomeration to some elongate. The values of dielectric constant and conductivity decrease considerably due to doping rare-earth ions in copper nanoferrites. Low saturation magnetization and high coercivity values of rare earth-doped copper nanoferrites are observed from the typical hysteresis curves.     

Effect of y/x ratio on luminescence properties of xSrO·yAl2O3：Eu2＋,Dy3＋ luminous fiber

Rare earth strontium aluminate luminous fiber is a novel functional fiber. In order to investigate the influence of Al/Sr ratio on luminescence properties of xSrO·yAl2O3：Eu2＋,Dy3＋ luminous fibers, several kinds of rare earth strontium aluminate luminous fibers were prepared by using rare-earth strontium aluminate as the rare-earth luminescent material and fiber-forming polymers such as polymer polyethylene terephthalate（PET） as a matrix and combining them with functional additives. X-ray diffraction（XRD）, fluorescence spectrophotometer, and afterglow brightness tester as well as microcomputer thermo-luminescence dosimeters were used to characterize the resulting samples. Results from XRD demonstrated that the phase of xSrO·yAl2O3：Eu2＋,Dy3＋ luminous fibers were different from one another as the Al/Sr ratio changed. Emission spectra of the samples with different Al/Sr ratios showed that emission intensity increased with the decrease of A1/Sr ratio at first then increased when it was over 2/1. From afterglow decay results, it could be found that Sr-rich sample showed lower luminance and shorter persistent time.     

Catalytic ozonation of NH4+-N in wastewater over composite metal oxide catalyst

Large amounts of water containing-ammonium nitrogen(NH₄⁺-N)have attracted increasing attention.Catalytic ozonation technology,involving the generation of hydroxyl radical(OH)with strong oxidation ability,was originally utilized to degrade organic-containing wastewater.In this paper,Ce/MnOx composite metal oxide catalysts prepared with different preparation conditions were used to degrade wastewater containing inorganic pollutant(NH₄⁺-N).The as-prepared catalyst features were characterized using X-ray diffraction(XRD),Brunauer-Emmett-Teller method(BET),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and H₂-temperature programmed reduction(H₂-TPR)techniques.The results show that the catalyst,prepared by conditions with precipitant Na₂CO₃ and Ce/Mn molar ratio 1:2 calcined at 400℃for 3 h in pH 11.0,displays the optimal performance,with the removal rate of NH₄⁺-N and selectivity to gaseous nitrogen,88.14 wt%and 53.67 wt%,respectively.The effects of several operating factors including solution pH,initial NH₄⁺-N concentrations and scavengers were evaluated.In addition,XRD patterns of catalyst with the best performance and the comparative study on decontamination of NH₄⁺-N by various processes(O₃,catalyst and catalyst/O₃)show that the primary metal oxides are CeO₂ and MnO₂ in Ce/MnOx composite metal oxide catalysts,which have a synergistic effect on the catalytic ozonation of NH₄⁺-N,and the new phase MnO₂ plays a great role.After 5 consecutive use cycles,the degradation efficiency is declined slightly,and can still achieve better than 70 wt%over 1 h reaction.Additionally,the application of catalytic ozonation for actual wastewater on the removal rate of NH₄⁺-N was investigated.Possible mechanism and degradation pathway of NH₄⁺-N were also proposed.In a word,the application of CeO₂-MnO₂ composite metal oxide catalysts in catalytic ozonation can be regarded as an effective,feasible and promising method for the treatment of NH₄⁺-N.     

Ammonia,oxidation leaching of chalcopyrite —reaction kinetics

The reaction for the ammonia, oxidation leaching of chalcopyrite, CuFeS₂ + 4NH₃ + 17/4 O₂ + 2 OH^- ⇌ Cu(NH₃)⁺² ₄2 + l/2Fe₂O₃ + 2 SO₄ + H₂O was studied using monosize particles in an intensely stirred reactor under moderate pressures to determine the important chemical factors which govern the kinetic response of the system. The reaction kinetics were studied at dilute solid phase concentration so that oxygen transport at the gas/liquid interface would not limit the rate. A catalytic electrochemical surface reaction was shown to control the reaction kinetics with the reaction rate determined by the following equation derived from electrochemical considerations: dα/dl=127 f/do (OH_- ^1/2 (k₁PO₁/1+k₂PO₁ (k₁+k₂(Cu⁺²)_o+k’₂α)(1-α)^2/3 (K P 1/2 Excellent agreement between theory and experiment was obtained both with regard to apparent reaction orders for oxygen, cupric, and hydroxyl, and with regard to geometric factors that influence the reaction rate. Further support for the reaction mechanism included an activation energy of approximately 10 kcal/mole obtained under a variety of experimental conditions and the fact that the initial reaction rate constant was several orders of magnitude less than predicted mass transfer coefficients. Formerly Metallurgy Graduate Student, University of Utah     

Factors affecting afterglow properties of red-emitting phosphor MgSiO3：Mn^2＋,Nd^3＋ for luminescent fiber

With stable physical properties,the rare-earth silicate phosphor of MgSiO3:Mn2+,Nd3+ is one of the suitable luminescent materials used in preparing functional fibers.In order to promote the afterglow properties of red-emitting phosphors,we prepared it by means of solid-state reaction,and the effect of manufacturing elements including H3BO3 and environmental factor of calcining temperature,type of flux on its luminescence property were investigated through evaluating their afterglow properties.The results showed that with the concentration of Nd 3+ increasing,the amounts of H3BO3 doping and calcining temperature,the afterglow time and initial brightness of the rare-earth silicate phosphor increased and then decreased gradually.The afterglow properties of different flux concentration were different from one to another as:H3BO3 >Na+>K+>No flux.     

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%.