Study on solubility of Nb2O5 in KOH solution and alkali leaching of niobite

Solubility of Nb₂O₅ and leaching behaviors of Nb and Ta from niobite in KOH solution have been investigated in order to develop an alkali hydrothermal leaching process of Nb and Ta. The solubility of Nb₂O₅ was measured in the range of 40 °C to 200 °C at various molar ratios of K₂O to Nb₂O₅(n(K₂O)/n(Nb₂O₅)). It has been found that Nb₂O₅ shows the maximum solubility at the solution composition of n(K₂O)/n(Nb₂O₅)=4/3 at a given temperature; the rise of temperature increases the solubility of Nb₂O₅ below 120 °C, but decreases it above 120 °C. The leaching behaviors of Nb and Ta were studied in the range of 150 °C to 250 °C and 0.1 MPa to 5 MPa. With the rise of temperature, the leaching degree increases when the leaching temperature is below 200 °C, but it decreases when the leaching temperature is above 200 °C. The maximum leaching degree is about 90% at 200 °C. It was proved that the alkali hydrothermal leaching process is effective for the recovery of Nb and Ta from niobite concentrate. Foundation item: The Key Project of Science and Technology Agency of Japan, 1994 Biography of the first author: ZHOU Kang-gen, doctor of engineering, professor, born in 1963, majoring in extractive metallurgy of rare metals and application of membrane separation technology.     

New technique of comprehensive utilization of spent Al2O3 -based catalyst

A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roasting temperature of 750 ℃ and roasting time of 30 min, molar ratio of Na2O to Al2O3 of 1.2, the leaching rates of alumina, vanadium and molybdenum in the spent catalyst are 97.2%, 95.8% and 98.9%, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by precipitators A and B, and the precipitation rates of vanadium and molybdenum are 94. 8% and 92. 6%. Al（OH）3 was prepared from sodium aluminate solution in the carbonation decomposition process, and the purity of Al2O3 is 99. 9% after calcination, the recovery of alumina reaches 90. 6% in the whole process; the Ni-Co concentrate was leached by sulfuric acid, a nickel recovery of 98. 2% and cobalt recovery over 98.5% can be obtained under the experimental condition of 30% H2SO4, 80 ℃, reaction time 4 h, mass ratio of liquid to solid 8, stirring rate 800 r/min.     

STUDY ON TREATMENT OF AMMONIA LEACHING SLAG IN THE METALLURGICAL PROCESS OF TUNGSTEN

ＳＴＵＤＹＯＮＴＲＥＡＴＭＥＮＴＯＦＡＭＭＯＮＩＡＬＥＡＣＨＩＮＧＳＬＡＧＩＮＴＨＥＭＥＴＡＬＬＵＲＧＩＣＡＬＰＲＯＣＥＳＳＯＦＴＵＮＧＳＴＥＮＳｕｎＰｅｉｍｅｎ；ＬｉＨｏｎｇｇｕｉ；ＬｉＹｕｎｊｉａｏ；ＬｉｕＭａｏｓｈｅｎｇ；ＳｕＰｅｎｇｔｕａｎ（...     

Simultaneous electrogenerative leaching of chaicopyrite concentrate and MnO2

In order to enhance the electrogenerative leaching rate of chalcopyrite concentrate reasonably, the principle of generative process was applied to simultaneous leaching of chalcopyrite concentrate and MnO2. The results show that Cu^2＋ and Mn^2＋ in addition to electrical energy could be acquired in the simultaneous electrogenerative leaching process. The leaching cell has the open circuit potential of about 1.0 V and gains quantity of electricity of about 700 C. The optimum leaching rates of Cu^2＋ and Mn^2＋ are 23.10% and 22.1%, respectively after electrogenera- tive leaching for about 10 h under the present conditions.     

Free alkali recovery from NaOH leaching liquor of tungsten ore by electrolysis with ion-exchange membrane

Ｔｈｅｃａｕｓｔｉｃｓｏｄａｌｅａｃｈｉｎｇｌｉｑｕｏｒｏｆｔｕｎｇｓｔｅｎｏｒｅ（ｗｏｌｆｒａｍｉｔｅｏｒｓｃｈｅｅｌｉｔｅ）ａｌｗａｙｓｃｏｎｔａｉｎｓａｇｒｅａｔｄｅａｌｏｆｆｒｅｅａｌｋａｌｉｆｏｒｔｈｅｒｍｏｄｙｎａｍｉｃａｎｄｋｉ－ｎｅｔ...     

Advanced sludge reduction and phosphorous removal process

An advanced sludge reduction process, i.e. sludge reduction and phosphorous removal process, was developed. The results show that excellent sludge reduction and biological phosphorous removal can be achieved perfectly in this system. When chemical oxygen demand ρ（COD） is 332 - 420 mg/L, concentration of ammonia p（NH3-N） is 30 - 40 mg/L and concentration of total phosphorous p（TP） is 6.0 -9.0 mg/L in influent, the system still ensures ρ（COD）〈23 mg/L, ρ（NH3-N）〈3.2 mg/L and ρ（TP）〈0. 72 mg/L in effluent. Besides, when the concentration of dissolved oxygen ρ（DO） is around 1.0 mg/L, sludge production is less than 0. 140 g with the consumption of 1 g COD, and the phosphorous removal exceeds 91 %. Also, 48.4% of total nitrogen is removed by simultaneous nitrification and denitrification.     

Electrochemical behaviors of gold and its associated elements in various complex agent solutions

1　INTRODUCTIONGoldisquitestableanddifficulttodissolveinacommonmineralacid .However ,becausethereisadelectroniclayerunfilledingoldatomicstructure ,goldcanbecombinedwithmanychemicalagentstoformstablecomplexions,causingthepotentialofgoldinasolutiontodecreaseandgoldtodissolveinthesolutioneasily .Basedonthisprinciple ,cyanideisanefficientlixiviatingagentofgold ,andhasbeenwidelyusedtoextractgoldfrom primaryandsecondaryresources .However ,itisthemosttoxicandnotbeneficialtoen vironmentprotection…     

Carburization of ferrochromium metals in chromium ore fines containing coal during voluminal reduction by microwave heating

Chromium ore fines containing coal (COFCC) can be rapidly heated by microwave to conduct the voluminal reduction, which lays a foundation of getting sponge ferrochromium powders with a lower content of C. Under the conditions of COFCC with n(O):n(C) (molar ratio) as 1.00:0.84 and n(SiO₂):n(CaO) as 1.00:0.39, the samples were heated by 10 kW microwave power to reach the given temperatures and held for different times respectively. The results show that the low-C-Cr ferrochromium metal phase in the reduced materials forms before the high-C-Cr ferrochromium metal phase does. With increasing temperature the C content of ferrochromium metals is in a positive correlation with the content of Cr. The C content of ferrochromium metal in reduced materials is 0–10.07% with an average value of 4.68%. With the increase of holding time the Cr content in ferrochromium metals is in a negative correlation with the content of C, while the content of Fe changes in the contrary way. In the microwave field the kinetic conditions of carburization are closely related with the temperature of microwave heating, holding time and carbon fitting ratio. Foundation item: Project(50474083) supported by the National Natural Science Foundation of China; Project supported by the Baoshan Iron & Steel Co. Ltd. of China     

The mechanism of ground granulated blastfurnace slag preventing alkali aggregate reaction

Three different methods were applied to study the alkali content of gelpores in cement. In the closed system, the concentration of K⁺, Na⁺ and OH⁻ have not reduced with the increase of age. In the open system, the diffusion and transferring of K⁺ and Na⁺ towards free space leads to the decrease of total alkali content. In the micro-analysis system, the contents of K⁺ and Na⁺ in the first hydrated layer of ground granulated blastfurnace slag (GBFS) are very low, while the contents of calcium and magnesium are relatively high. This phenomenon shows that the mechanism of GBFS preventing alkali aggregate reaction (AAR) is: when GBFS is dissolved by alkali medium, SiO₂ and Al₂O₃ are dissolved into the cement matrix, then around GBFS particles form reaction rings rich in Ca²⁺ and Mg²⁺, and the C-S-H gel of positive charges formed in the area repulses K⁺ and Na⁺, which are forced to transfer to the mortar’s matrix, pore or mortar sample surface. The transferred K⁺ and Na⁺ form alkali gel products with other dissolved ions, then become evenly distributed in the mortar sample and react with Ca(OH)₂ in pore solutions to form (Na,K) _x−2z ·zCa·(SiO₂)_y·(OH)_x gel products; and thus changes the AAR gel products’ structure. The gel products will not expand, and so they can delay expansion destruction.     

Existence of positive solutions in a delay logistic difference equation

The author studied the existence of positive solutions of the delay logistic difference equationΔyn=pnyn(1-yτ(n)), n=0,1,2,....where {pn} is a sequence of positive real numbers, {τ(n)} is a nondecreasing sequence of integers, τ(n)＜n and limn→∞τ(n)=∞. A sufficient condition for the existence of positive solutions of the equation was given.     

Ways of constructing optimal magic cube of order n when ( n , 2·3·5·7)=1

An optimal magic cube of order n is a magic cube whose row sums, column sums and oblique sums of 9n layers are n(n ³ + 1)/2. The author proved that optimal magic cubes of order n may be constructed as long as n and 2, 3, 5, 7 are relatively prime, and a formula for making optimal magic cubes by using optimal Latin squares and optimal magic squares was given. Foundation item: Supported by the Arts and Science Foundation of Central South University (No.2000007) Biography of author: CHEN Xiao-song, associate professor, born in 1956, majoring in algebra and number theory.     

One-pot synthesis and structural characterization of urea-isobutyraldehyde-formaldehyde resin

Urea-isobutyraldehyde-formaldehyde (UIF) resin was synthesized from urea, isobutyraldehyde, and formaldehyde using sulfuric acid as a catalyst by one pot method. The effects of molar ratios of isobutyraldehyde to formaldehyde (n(I)/n(F)) and aldehyde to urea (n(A)/n(U)) on the yield, hydroxyl value (vs KOH) and softening point of the resin were investigated. The structure of the resin was characterized by FT-IR, ¹H-NMR and ¹³C-NMR. The results show that when the molar ratio of urea to isobutyraldehyde to formaldehyde (n(U)/n(I)/n(F)) is 1.0/3.0/3.0, the yield UIF resin is 67.1%, and the softening point and hydroxyl value are 88 °C and 37 mg/g, respectively. The FT-IR, ¹H-NMR and ¹³C-NMR results show that the lactam is formed by aminomethylation from urea, isobutyraldehyde, and formaldehyde. Foundation item: Project(2006A10902001) supported by the Science and Technology Plan of Guangdong Province, China; Project(2007Z3-D0351) supported by the Science and Technology Plan of Guangzhou City, China     

Thermodynamics calculation on the oxidation and sulfur removal abilities of slag in EAF dust pellet reduction process

ＥＡＦｄｕｓｔｈａｓｂｅｅｎｃｌａｓｓｉｆｉｅｄａｓｈａｚａｒｄｏｕｓｗａｓｔｅ ,ａｎｄｉｔｉｓｈａｒｍｆｕｌｉｎｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｌａｎｄ ｆａｌｌｄｕｅｔｏｃｏｎｔａｉｎｉｎｇｈｅａｖｙｍｅｔａｌｓ[1] .Ｍｏｓｔｒｅｃｙ ｃｌｉｎｇｍｅｔｈｏｄｓ[2 8] ｄｅｖｅｌｏｐｅｄｆｏｒｔｈｅｄｕｓｔｓａｒｅｏｎｌｙｆｏｒｔｈｅｒｅｃｏｖｅｒｙｏｆｌｅａｄ ,ｚｉｎｃａｎｄｃａｄｍｉｕｍ .ＴｈｅＥＡＦｄｕｓｔｆｒｏｍｓｔａｉｎｌｅｓｓｓｔｅｅｌｍａｋｉｎｇｍａｉｎｌｙｃｏｎ ｔａｉｎｓｎｉｃｋｅ…     

Soda decomposition of low-grade tungsten ore through mechanical activation

Leaching of low-grade refractory tungsten ore was carried out through mechanical activation. The effect of temperature, amount of Na₂CO₃, addition of NaOH, ratio of liquid to solid and leaching time on the recovery of WO₃ was studied. The WO₃ recovery upto 96%–99% has been achieved when the tungsten ore was digested by soda not more than three times stiochiometric amount at 185–195 °C for 1.0–2.0 h. The WO₃ recovery can increase 10%–15% compared to that of conventional soda autoclave process. Project supported by the Key Program of the 8th Five-year Plan of China Synopsis of the first author Zhao Zhongwei, born in 1966, received Ph D degree in 1995. Major research field: hydrometallurgy, seperation science and mechanochemistry.     

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69μm, holding at 80℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2：1, and the ratio （g/mL） of solid to liquid being 1：10.     

Preparation of λ-MnO2 by Column Method and Its Ion-Sieve Property

λ-MnO₂ was prepared by column method from normal spinel LiMn₂O₄ with purity of 99.38%. The influence of LiMn₂O₄ grain size and acidity of leaching solution on the lithium leaching process was studied. The results show that the appropriate range of LiMn₂O₄ grain size was 60–160 meshes and the concentration of leaching solution HCl was 0.1 mol·L⁻¹. The adsorption capacity Q of λ-MnO₂ for lithium increased with the increase of pH and changed markedly at pH 6.0–10.0. It was 3.80mmol/g at pH 12.0 The distribution coefficients K_d of Li⁺ and Na⁺ were 3.406×10⁴ and 2.300 respectively, and the separation coefficient a _Na ^Li was 1.481 ×10⁴ at pH 6.5. As a result, λ-MnO₂ is a high performance ion-sieve material for lithium ion. LEI Jia-heng: Born in 1957. Funded by the National Natural Science Foundation of China (No. 59972027) and the Natural Science Foundation of Hubei Province (No. 2002AB074)).     

Microstructures and properties of WC-2OCo-1Y2O3 cemented carbide by hot-press and liquid phase sintering

Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake (uneven-ly distributed binder phase), and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2 O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.     

Effect of doped Mn on piezoelectric properties of （Na0.5Bi0.5 ）0.92 Ba0.08 TiO3 lead-free ceramics

Piezoelectric ceramics (Na0.5Bi0.5)0.92Ba0.05TiO3 x%MnCO3(BNBT-Mn, x=0-1.6,mass fraction)were synthesized by conventional solid state reaction. The results show that when the addition of MnCO3 is 0-1.4%, BNBT-Mn ceramics exhibit a single-phase perovskite structure. With the increase of content of MnCO3, piezoelectric constant and electromechanical coupling factor increase rapidly when x is lower than 0.3. Then they both decrease when x is in the range of 0.3 and 1.6. When x=0.3, piezoelectric constant and electromechanical coupling factor reach the maximum value of 160 pC/N and 58.5% respectively, which can improve the temperature stability of BNBT-Mn.     

The petrochemistry and geochemistry of rich-alkali granite porphyry in Western Yunnan

The characteristics of the chemical composition of the rich-alkali granite porphyries are poor in SiO₂, with mean content of 69.19%, but rich in alkali and high in potash. The mean content of (K₂O+Na₂O) is 9.85%. K₂O is much greater than Na₂O, mean value of K₂O/Na₂O is 2.10. As shown by the REE analysis, REE contents is lower. Compared with the granite of south China, the rich-alkali granite porphyry hase higher LREE, and no anomaly of europium (δEu=0.87). Its genetic type belongs to A type graritoid. Project supported by the Key Program of 8th Five-Year Plan of China Synopsis of the first author Hu Xiangzhao, associated professor. born in Dec. 1949. majoring in Petrology and Geochemistry.     

Effects of drying method on preparation of nanometer α-Al2O3

Ammonium aluminum carbonate hydroxide （AACH） precursor was synthesized by the precipitation reaction of aluminum sulfate and ammonium carbonate. Then the precursor was dealt with five drying methods including ordinary drying, alcohol exchange, vacuum freeze-drying, glycol distillation, n-butanol azeotropic distillation respectively and calcined at 1 200℃ for 2 h to get α-Al2O3. The effects of drying methods on preparation of nanometer α-Al2O3 were discussed, and the optimal drying method was confirmed. The structural properties of powders were characterized by XRD, SEM and BET measurements. The results show that vacuum freeze-drying, glycol distillation and n-butanol azeotropic distillation can prevent the powders from aggregating, and among them the n-butanol azeotropic distillation is the best method. The nanometer α-Al2O3 powder with non-aggregation can be manufactured using n-butanol azeotropic distillation and the average particle size is about 40 nm.