Study on the adsorption of lanthanum(Ⅲ) from aqueous solution by bamboo charcoal

The adsorption behaviors of La(Ⅲ) ion on bamboo charcoal were investigated with various chemical methods and IR spectrometry. Parameters studied include the effects of pH,average particle size,initial ion concentration,contact time and temperature by batch method. The results showed that bamboo charcoal could remove La(Ⅲ) ions effectively from aqueous solution. The loading of La(Ⅲ) ions was strongly dependent on pH of the medium and the optimal adsorption condition was in HNO3-TEA medium with pH value of 7.20. In the batch system,the modified bamboo charcoal exhibited the highest La(Ⅲ) ion uptake as 120 mg/g at 298 K,at an initial pH value of 7.20. The adsorption kinetics were tested with Lagergren-first-order model and pseudo-second-order model. The adsorption data were conformed to the Langmuir and Freundlich isotherms,and the correlation coefficients had been evaluated. Thermodynamic parameters such as free energy(ΔG) ,which were all negative,indicated that the adsorption of La(Ⅲ) ion onto bamboo charcoal was spontaneous and the positive value of enthalpy(ΔH) showed that the adsorption was endothermic in nature. Thomas model was applied to experimental column data to determine the characteristic parameters of column useful for process design. The characterization of both before and after adsorption of La(Ⅲ) ion on bamboo charcoal was undertaken using IR spectroscopic technique. The results revealed that bamboo charcoal was a good choice as a biosorbent for the recovery of lanthanum from aqueous solution.     

Development of Test Method for Measuring Sintering Temperature of Mould Fluxes

 Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the formation of cavities caused by melting of samples. For monitoring, the differential pressure of an inert gas flow was measured through a set volume of sample (mould flux A) held in a furnace tube. The apparent sintering temperature was defined in this test to determine sintering process. The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures. The experimental results indicated that the apparent sintering temperature (AST) was a useful parameter to assess the threat of problems related to sinter.     

Efficient extraction and stripping of Nd(Ⅲ),Eu(Ⅲ) and Er(Ⅲ) by membrane dispersion micro-extractors

The extraction of low concentration rare earth elements at high phase ratio was investigated. The traditional extraction set-up, such as mixer-settler, have drawbacks of easy emulsification, difficult separation and low efficiency if operated at the above condition. Membrane dispersion micro-extractor,owing to its well-dispersed, high surface-to-volume ratio and fast mass transfer rate, was employed in our work. Nd(Ⅲ),Eu(Ⅲ),Er(Ⅲ) were chosen to represent light, medium,heavy rare earth elements(REEs). The extraction process of REEs with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester(P507) was investigated by membrane dispersion micro-extractors. Firstly, the extraction equilibrium of these three elements was explored in the stirred conical flasks, and it is indicated that the extraction efficiencies can be 0.95, 0.97 and 0.98, respectively within 40 min at phase ratio of 100:1. Then the effects of operational conditions such as the residence time, organic and aqueous flow rates on extraction efficiency were also explored in micro-extractors. The results indicate that the efficiency decreases and then increases if increasing aqueous phase flow rate, residence time and droplets' diameter are the key factors of this process. Increasing the phase ratio reduces the extraction efficiency significantly. When the REEs solution has an initial pH of 4.00, the flow rates of continuous and dispersed phase are 40 and 1.6 mL/min,respectively, and 90 mg/L Nd(Ⅲ), Eu(Ⅲ) and Er(Ⅲ) is extracted by 1 mol/L P507 at the out-let length of8 m. The extraction efficiencies are 0.978,0.983 and 0.991, respectively. Finally the stripping process was also studied with the micro-extractor. The stripping efficiencies of Nd(Ⅲ), Eu(Ⅲ) and Er(Ⅲ) can reach0.99, 0.96 and 0.91, respectively when the out-let length is 8 m and the concentration of hydrochloric acid is 1 mol/L. The developed approach offers a novel and simple strategy on the fast extraction and enrichment of low concentration rare earth elements from waste water.     

Ion imprinted cryogel-based supermacroporous traps for selective separation of cerium(Ⅲ) in real samples

This study demonstrates the preparation and characterization of a novel ion imprinted cryogel which exhibits high affinity and selectivity towards Ce(Ⅲ) ions in aqueous solutions and bastnasite ore samples.2-Hydroxyethyl methacrylate(HEMA) and N-methacryloylamido antipyrine(MAAP) were used as functional monomers for the preparation of Ce(Ⅲ) imprinted cryogel. The effects of various factors such as initial Ce(Ⅲ) concentration, flow rate, pH, interaction time and ionic strength on the Ce(Ⅲ) binding to the prepared ion imprinted cryogels were also studied. The binding equilibrium for Ce(Ⅲ) is obtained in30 min at the flow rate of 0.5 mL/min. The maximum binding capacity of the prepared ion imprinted cryogel towards Ce(Ⅲ) is obtained as 36.58 mg/g at optimum conditions. The selectivity of the prepared ion imprinted cryogel towards Ce(Ⅲ) in the presence of other possible interfering lanthanide ions such as La(Ⅲ) and Nd(Ⅲ) were also performed. The obtained results showed that the prepared ion imprinted cryogel exhibits high selectivity and sensitivity towards Ce(Ⅲ) ions. The limit of detection(LOD) was found as 50 μg/L.     

Effects of neodymium and gadolinium on weathering resistance of ZnO-B2O3-SiO2 glass

The ZnO-B203-SiO2 glass doped with Nd2O3 and Gd2O3 was prepared by high temperature melt cooling method. The standard sample of the zinc borosilicate glass was placed in the constant temperature and humidity chamber in order to simulate the atmospheric corrosion process. The surface of the weathered glass was analyzed by scanning electron microscope and energy disper- sive spectrometry and the filtrate was analyzed by inductively coupled plasma-atomic emission spectrometry. The results showed that humidity was the most important factor influencing weathering; the morphology of glass surface of altered layer and the product on the surface was observed; the corroding degree of the zinc borosilicate glass doped with Nd or Gd was significantly lighter than that of the base glass. Adding rare earth Nd or Gd in the zinc borosilicate glass could suppress Na, Zn, Si ion release in weathering.     

Effect of MgO on Oxidation Process of Fe3 O4 in Pellets

Induration process of oxidized pellets involves the oxidation of Fe3 O4 and re-crystallization of Fe2 O3 .The oxidation process of Fe3 O4 is significant for pellets to obtain better ambient strength.Thus,the effect of MgO on oxidation process of Fe3 O4 was investigated.The unreacted core model was applied to analyze the oxidizing indura-tion process of pellets.The experimental results show that MgO plays a negative role in the oxidation process of Fe3 O4 .The oxidation rate of Fe3 O4 in MgO-fluxed pellets (95.0% Fe3 O4+5.0% MgO)is slower than that in standard acid pellets (100% Fe3 O4 ).The relation between oxidation ratio of Fe3 O4 and time was calculated based on the unreacted core model for both MgO-fluxed pellets and standard acid pellets.According to verification experi-ments,the values calculated by model coincide well with the experimental values.Therefore,the unreacted core model could be applied to describe the oxidizing induration process of pellets.     

Effects of mechanical activation on the kinetics of terbium leaching from waste phosphors using hydrochloric acid

The effect of mechanical activation(MA) on the kinetics of terbium(Tb) leaching from waste phosphors using hydrochloric acid was investigated. Leaching kinetics, such as apparent reaction rate, activation energy and reaction order, were determined using the shrinking-core model and the Arrhenius equation. Results obtained from experiments with different concentrations of HCl and under different leaching temperatures were used for the determinations. The impacts of factors such as rotational speed, HCl concentration and leaching temperature on the leaching rate of Tb were also discussed. The results showed that MA could dramatically increase the leaching rate of Tb from waste phosphors, and the apparent reaction rate(k_(ap)) of leaching was accelerated as well. For inactivated waste phosphors, the apparent activation energy(E_(ap)) was 52.82±3.95 kJ/mol, indicating that the rate-controlling step of the leaching process was the chemical reaction. The E_(ap) dropped to 25.96 ±3.90 kJ/mol and 10.96±2.79 kJ/mol when the waste phosphors were mechanically activated at rotational speeds of 400 and 600 r/min, respectively; the leaching process transformed to a hybrid(chemical-reaction and diffusion) control process, and even a reagent-diffusion(through the product layer) control process. The apparent reaction order for Tb leaching from 400 r/min-activated waste phosphors was 2.49±0.11, and it decreased to 1.16±0.17 when the rotational speed of 600 r/min was used. Kinetics results indicated that MA could make Tb leaching occur spontaneously, and the activation intensity of waste phosphors was strengthened with higher rotational speed.     

Grain Growth Behavior in Sintered Nd-Fe-B Magnets

The Nd2Fe14B grain growth behavior in sintered Nd-Fe-B magnets was quantitatively described.The effects of sintering temperature and time,and alloy powder size and its distribution on grain growth process were analyzed.Hence,possible grain growth mechanisms in these magnets were qualitatively discussed.The Nd2Fe14B grain growth proceeded at quite a high rate in the initial 0~1 h of sintering and from then onwards the grain growth rate decreased.A large average particle size or a wide particle size distribution of initial alloy powders was found to remarkably accelerate the grain growth process and even result in the occurrence of abnormal grain growth.On the basis of experimental results,two grain growth mechanisms were considered to operate during sintering of Nd-Fe-B magnets,that is,dissolution and re-precipitation of Nd2Fe14B particles,and Nd2Fe14B particle growth by coalescence.It was believed that Nd2Fe14B particle growth by coalescence not only produced a large average grain size and a wide grain size distribution,but also was the fundamental reason for the formation of abnormally large grains in the microstructure of sintered Nd-Fe-B magnets.     

Thermochemical Properties of the Complexes RE(HSal)3·2H2O (RE=La, Ce, Pr, Nd, Sm)

Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(Hsal)3·2H2O(RE=La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE3 ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, ΔcU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated.     

Extraction kinetics of neodymium from chloride medium using HEH/EHP saponified with magnesium bicarbonate solution

Magnesium bicarbonate solution is considered as an environmentally friendly extractant saponification agent for the solvent extraction of rare earth elements due to its advantage of minimum water pollution.In order to reveal the extraction regularity, optimize production-process and guide the use of this new extraction system, the extraction of Nd(Ⅲ) in chloride medium with HEH/EHP saponified by magnesium bicarbonate solution was investigated with the self-designed constant interfacial area cell. Besides, the effects of stirring rate, temperature, specific interfacial area and concentration of Mg-HEH/EHP on the extraction rate of Nd(Ⅲ) were systematically investigated. Results show that, the rate of extraction is governed by both diffusion and chemical reaction, and the extraction reaction takes place at the interface. The apparent activation energy of the extraction reaction is 16.88 kJ/mol. The corresponding rate equation is deduced. The mechanisms and rate-determining step are speculated based on interfacial reaction models, which is consistent with the experimental results.     

Nd(III)在NaF-KF熔盐钨电极上电化学行为

钕铁硼磁体中稀土元素钕占据较大比重,从钕铁硼废料回收稀土有重大意义。为进一步了解钕在高温下氟化物熔盐的行为,本文在1 063 K采用NaF-KF(摩尔比2:3)电解质体系,加入质量分数为1%的NdF₃,以Pt为参比电极,钨棒为对电极,用循环伏安法等电化学暂态测试研究了Nd(III)在惰性钨电极上的电化学过程,探究Nd(III)的还原机理。结果显示:Nd(III)于NaF-KF-NdF₃熔盐中在惰性钨电极上的电化学还原过程是受扩散控制的不可逆的一步反应:Nd(III)+3e-=Nd,1 063 K时循环伏安法得到Nd(III)的扩散系数为2.107×10-5 cm2/s,钕的成核机制为瞬时成核。      

Extraction equilibrium of beryllium and aluminum and recovery of beryllium from Egyptian beryl solution using CYANEX 921

Extraction of Be(II) and Al(III) from aqueous sulfate solution by CYANEX 921 (commercial trioctylphospine oxide) in kerosene was separately studied. The parameters affecting the extraction process, such as hydrogen ion, sulfate ion, and CYANEX 921 concentrations, and temperature were investigated. It was found that Be(II) was highly extracted by CYANEX 921 from an aqueous medium of 0.001 M sulfate and pH 9.0, while Al(III) was highly extracted from a similar solution at pH 5.0. Be(II) extraction was found to decrease with temperature (exothermic), while Al(III) extraction increased with temperature (endothermic). The different species that might be extracted are given and discussed. Extraction of Be(II) and Al(III) by purified TOPO under similar experimental conditions showed that purified TOPO gives relatively less extraction, especially for Al(III) in the pH range 4.0–6.0.Based on the obtained results, separation of beryllium from aluminum and recovery of pure beryllium from beryl mineral were studied. Removal of iron as the main interfering ion in the beryl solution was investigated. A flow chart for the Be/Al separation process was developed and applied to recover pure Be(II) from Egyptian beryl.     

Extraction equilibrium of beryllium and aluminum and recovery of beryllium from Egyptian beryl solution using CYANEX 921

Extraction of Be(II) and Al(III) from aqueous sulfate solution by CYANEX 921 (commercial trioctylphospine oxide) in kerosene was separately studied. The parameters affecting the extraction process, such as hydrogen ion, sulfate ion, and CYANEX 921 concentrations, and temperature were investigated. It was found that Be(II) was highly extracted by CYANEX 921 from an aqueous medium of 0.001 M sulfate and pH 9.0, while Al(III) was highly extracted from a similar solution at pH 5.0. Be(II) extraction was found to decrease with temperature (exothermic), while Al(III) extraction increased with temperature (endothermic). The different species that might be extracted are given and discussed. Extraction of Be(II) and Al(III) by purified TOPO under similar experimental conditions showed that purified TOPO gives relatively less extraction, especially for Al(III) in the pH range 4.0–6.0.Based on the obtained results, separation of beryllium from aluminum and recovery of pure beryllium from beryl mineral were studied. Removal of iron as the main interfering ion in the beryl solution was investigated. A flow chart for the Be/Al separation process was developed and applied to recover pure Be(II) from Egyptian beryl.     

Effect of Mo content on porous Ni3Al–Mo electrodes for hydrogen evolution reaction

Abstract

Porous Ni₃Al–Mo electrodes were obtained by reactive synthesis methods with Mo contents of 2, 5, 10, 15 and 20 wt-% respectively. The microstructure, surface morphology and composition of the prepared porous Ni₃Al–Mo electrodes were analysed by X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS) and scanning electron microscopy (SEM). Hydrogen evolution reaction (HER) on the porous Ni₃Al–Mo electrodes in 6 mol L^?1 KOH solution was investigated by polarisation measurements and electrochemical impedance spectroscopy (EIS) technique. It was shown that the hydrogen evolution activity of the porous Ni₃Al–Mo electrodes was related with the Mo content. The porous Ni₃Al–Mo electrode with optimum catalytic activity for the HER was found to contain the maximum Mo content of 10 wt-%.     

Thermodynamic Simulation of the A<Superscript>III</Superscript>–B<Superscript>V</Superscript> Semiconductor Melts

The equilibrium compositions and the thermodynamic characteristics of binary Ga–Sb, Al–Sb, and In–Sb melts are studied by a thermodynamic simulation using the TERRA software package over wide temperature and composition ranges. The temperature dependences of the partial pressures of the components of the gas phase forming above the III–V (III = Ga, In; V = Sb) semiconductor melts are investigated. The concentration dependences of the component activities and the partial and integral characteristics of melt mixing are obtained. All melts under study are shown to exhibit large negative deviations from Raoult’s law, which is caused by the presence of associates and indicates a strong interaction between the melt components. The temperature dependences of the logarithms and the partial pressures of the gas phase components are obtained. These dependences are shown to be linear for the components of the gas phase forming over the Ga–Sb, Al–Sb, and In–Sb melts.     

Electrode process of La(III) in molten LiCl-KCl

The electrode process of La(III) at Mo electrode in the molten LiCl-KCl for temperatures ranging from 683 K to 773 K was studied by cyclic voltammetry and chronopotentiometry, respectively. The results showed that in the molten LiCl-KCl, reduction of La(III) occurred in a step with a global exchange of three electrons. Cyclic voltammetry studies indicated that at a sweep rate lower than 0.2 V/s, the electroreduction of La(III) to lanthanum metal was reversible and controlled by diffusion of La(III). However, the process became under a mixed control of both diffusion and electron transfer when sweep rate exceeded 0.2 V/s. And an empirical temperature dependence of the diffusion coefficient of La(III) was proposed: lnD_La(III)=7.742–1.441×10⁴/T. And the relation between the formal potential of La(III)/La versus Ag/AgCl reference electrode and temperature was described in the following equation: E^θ'=–1.402–4.689×10²/T.     

Electrochemical behavior of cerium ion in molten LiCI-KCI

The electrode process of cerium(Ⅲ) on the Mo electrode in eutectic LiCl-KCl melt was investigated by electrochemical transient techniques in the temperature range of 673-783 K,respectively.These results unanimously indicated that the reduction process of cerium(Ⅲ) to cerium metal was a single step exchanging three electrons which was controlled by diffusion of cerium(Ⅲ).Diffusion coefficients(D Ce(Ⅲ)) in eutectic LiCl-KCl melt were determined by cyclic voltammetry,chronopotentiometry and square wave voltammetry.An empirical diffusion coefficient function depending on temperature was proposed:lnD Ce(Ⅲ) =-2.129-5704/T.The formal potentials(Eθ’ Ce(Ⅲ)/Ce(0) versus Ag/AgCl reference electrode) at different temperatures were obtained from chronopotentiometry,which were-2.10 V(673 K) and-2.07 V(733 K),respectively.     

Effect of Lu2O3 on Charge/discharge Performances of Spherical Nickel Hydroxide at High Temperature

Nickel-metal hydride （Ni/MH） batteries are one of promising batteries for electric vehicle applications, but at high temperature the charge efficiency of nickel electrode is very low. In order to improve the high-temperature-efficiency of nickel electrode, spherical nickel hydroxide mixed with various ratios of Lu2O3 was used as active material of pasted nickel electrodes. The results of charge/discharge experiments, cyclic voltammetric measurements and XRD characterizations have shown that after addition of Lu2O3, the oxygen evolution overpotcntial is elevated much, the charge efficiency of nickel electrode at high temperature is greatly improved and the content of β-NiOOH phase increases in charged electrodes. In addition, the mixed ratio of Lu2O3 has different effects on high temperature performances of nickel electrode at different charge/discharge currents, 3.5 % is the optimum mixed ratio, and the action of Lu2O3 on high temperature electrochemical behaviors is more apparent when nickel electrodes are charged at small current than large current.     

Electrodeposition of Mg-Li-Al-La Alloys on Inert Cathode in Molten LiCl-KCl Eutectic Salt

Electrochemical preparation of Mg-Li-Al-La alloys on inert electrodes was investigated in LiCl-KCl melt at 853 K (580 °C). Cyclic voltammograms (CVs) and square wave voltammograms (SWVs) show that the existence of AlCl₃ or AlF₃ could promote La deposition on an active Al substrate, which is predeposited on inert electrodes. All electrochemical tests show that the reduction of La³⁺ is a one-step reduction process with three electrons exchanged. The reduction of La(III)→La(0) occurred at –2.04 V, and the underpotential deposition (UPD) of La was detected at –1.55 V (vs Ag/AgCl). The same phenomena concerning La UPD were observed on two inert cathodes, W and Mo. In addition, Mg-Li-Al-La alloys were obtained by galvanostatic electrolysis on the W cathode from La₂O₃ in LiCl-KCl-MgCl₂-KF melts with aluminum as the anode. X-ray diffraction (XRD) measurements indicated that various phases like the Al₂La, Al₁₂Mg₁₇, and βLi phase (LiMg/Li₃Mg₇) existed in the Mg-Li-Al-La alloys. The distribution of Mg, Al, and La in Mg–Li–Al-La alloys from the analysis of a scan electron micrograph (SEM) and energy dispersive spectrometry (EDS) indicated that the elements Mg, Al, and La distributed homogeneously in the alloys.     

Cathodic reduction process of Al–Cu–Y alloy in fluoride-oxide eutectic system via molten salt electrolysis

Al-Cu-Y alloys were prepared by molten salt electrolysis in fluoride-oxide system composed of electrolyte(Na_3 AlF_6-AlF_3-LiF-MgF_2) and oxide(Al_2 O_3-CuO-Y_2 O_3). Cathodic reduction process of Al_2 O_3,CuO and Y_2 O_3 were analyzed by cyclic voltammetry and chronoamperometry. Components and phase composition of alloy samples prepared by potentiostatic electrolysis were characterized by scanning electron microscopy and energy dispersive spectroscopy. The results show that the Al-Cu-Y alloy can be prepared in the AIF_3-NaF-5 wt%LiF-5 wt%MgF2(NaF/AlF_3 = 2.2, molecular ratio) eutectic system with mixed oxide(Al_2 O_3-CuO-Y_2 O_3) through 2 h at the conditions of a temperature of 1208 K, cell voltage3.0 V, cathode current density 0.7 A/cm~2. Al(Ⅲ) and Cu(Ⅱ) ions can be reduced to zero valence Al(0) and Cu(0) directly on carbonaceous electrode surface by instantaneous nucleation, respectively, the reduction process is controlled by diffusion. The reduction potential of Y(Ⅲ) ions is close to the active ions of fluoride melts, but strengthened phase AI3 Y can be formed through electrochemical reduction and alloyed process with active Al(Ⅲ) and Cu(Ⅱ) ions, meanwhile, the Al_2 Cu and Al_3 Y phases are distributed at the grain boundary of Al matrix.