Selective leaching of vanadium from V-Ti magnetite concentrates by pellet calcification roasting-H_2SO_4 leaching process

A novel method of pellet calcification roasting-H_2 SO_4 leaching was proposed to efficiently separate and extract vanadium(V) from vanadium-titanium(V-Ti) magnetite concentrates.The leaching rate of V is as high as 88.98%,while the leaching rate of impurity iron is only 1.79%.Moreover,the leached pellets can be used as raw materials for blast furnace ironmaking after secondary roasting.X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy with energy dispersive X-ray spectrometry(SEMEDS) analyses showed that V~(3+) was oxidized to V~(5+) after roasting at 1200℃,and V~(5+) was then leached by H_2 SO_4.X-ray diffraction(XRD) analyses and single factor experiment revealed a minimal amount of dissolved Fe_2 O_3 during H_2 SO_4 leaching.Therefore,a high separation degree of V and iron(Fe) from V-Ti magnetite concentrate was achieved through H_2 SO_4 leaching.Compared with the traditional roastingleaching process,this process can achieve a high selectivity of V and Fe,and has excellent prospects for industrial production.     

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.     

Dissolution rate determination of alumina in molten cryolite-based aluminum electrolyte

Determination of dissolution rate of alumina is one of the classical problems in aluminum electrolysis. A novel method which can measure the dissolution rate of alumina was presented. Effect of factors on dissolution rate of alumina was studied intuitively and roundly using transparent quartz electrobath and image analysis techniques. Images about dissolution process of alumina were taken at an interval of fixed time from transparent quartz electrobath of double rooms. Gabor wavelet transforms were used for extracting and describing the texture features of each image. After subsampling several times, the dissolution rate of alumina was computed using these texture features in local neighborhood of samples. Regression equation of the dissolution rate of alumina was obtained using these dissolution rates. Experiments show that the regression equation of the dissolution rate of alumina is y=−0.000 5x ³+0.024 0x ²−0.287 3x+ 1.276 7 for Na₃AlF₆-AlF₃-Al₂O₃-CaF₂-LiF-MgF₂ system at 920 °C.     

Study on the method of recovering and separating indium from residue containing indium

A method of recovering indium from complex smelting residue containing indium was investigated. Indium was extracted by technique of low acid leaching and solvent extraction. The conditions of separating iron and indium were studied and the optimal conditions were determined. When the residue is twoclass-countercurrent leached with 2 mol/L H2SO4 and 30-40 g/L NaC1 at 100 ℃, the leaching rate of indium is 80%. The extraction rate of indium is over 98% and that of iron is less than 5% after it is third-class-countercurrent extracted by P204, and when sulfonated kerosene is used as solvent, acidity in aqueous phase remains the same as that of leaching liquid, and phase is for 1 : 3. Using 2 mol/L HC1 as back-extraction agent, with phase ratio being 5 : 1, by third-class-countercurrent back-extraction, the back-extraction rate of indium is over 99%, but that of iron is very low, which can meet the need of separating indium and iron.     

Greenhouse gas emissions and reduction potential of primary aluminum production in China

A cradle-to-gate life cycle assessment was conducted in this paper to calculate the greenhouse gas (GHG) emissions, such as CO₂, CH₄, CF₄ and C₂F₆ emissions, based on statistic data of Chinese aluminum industry of the year 2003. The results showed that the GHG emissions for 1 t primary aluminum production was 21.6 t CO₂ equivalent which is 70% higher than that of worldwide average level of the year 2000. The main contributors of emission were the alumina refining and aluminum smelting process accounting for 72% and 22% in accumulative emission, respectively. According to the development and application of new process technologies for primary aluminum production and the ‘target of energy-saving and emissions-reducing’ of Chinese government, the reduction potential of the GHG emissions for alumina and aluminum production were estimated. The results indicated that China aluminum industry would achieve the target of reducing about 25% GHG emissions by the end of 2010. Supported by the National Natural Science Foundation of China (Grant No. 50525413), National Basic Research Program of China (973 Program) (Grant No. 2007CB613706), and Beijing Natural Science Foundation (Grant No. 2081001)     

A kind of double-sided porous anodic alumina membrane fabricated with the three-step anodic oxidation method

The porous anodic alumina membranes (PAAMs) have been successfully used as templates for the fabrication of functional nano-materials due to their outstanding regularity and physicochemical properties. In this paper, a transparent double-sided anodic alumina membrane with ultra-thin aluminum substrate was fabricated with the three-step anodic oxidation method in the oxalic acid electrolyte. The characters such as the top-surface morphology, membrane thickness, and depth of nanopores of this three-layer (Al₂O₃-Al-Al₂O₃) sandwiched nano-structure were controllable through regulating the main anodic oxidation conditions, e.g., anodic oxidation time of various steps, coating remove process. The experiments data revealed that the aluminum substrate is exponential declined with the oxidation time when it was approximately reduced by a few micrometers. This new double-sided anodic alumina membrane can be used as the high-quality functional field emission materials and templates.     

Mechanisms of composite agglomeration of fluoric iron concentrate

The effect of composite agglomeration process (CAP) on fluoric iron concentrates sintering was investigated. The yield and quality of the sinter are greatly improved when using CAP assisted with heat airflow and enhancing magnesium oxide (MgO) contents. For conventional sintering of fluoric iron concentrate, due to lower viscosity of binding phase and higher fluidity of liquid phase, the sinter is formed with large thin-walled holes and the strength of the sinter is deteriorated consequently. The novel process forms composite agglomerate in which acid pellets are embedded in basic sinter. The pellets are solid with interconnecting crystals of hematite (Fe₂O₃) and magnetic (Fe₃O₄). For basic sintering, after adding MgO, the viscosity of the melting phase increases and the fluidity decreases; and calcium and aluminum silico-ferrites and magnesium ferrite are formed with perfect crystals and good sintering microstructure.     

Influence of deposition pressure on properties of ZnO: Al films fabricated by RF magnetron sputtering

Transparent conductive aluminum doped zinc oxide(ZnO:Al,AZO) films were prepared on glass substrates by rf(radio frequency) magnetron sputtering from ZnO: 3wt% Al_2O_3 ceramic target. The effect of argon gas pressure(PAr) was investigated with small variations to understand the influence on the electrical, optical and structural properties of the films. Structural examinations using X-ray diffraction(XRD) and scanning electron microscopy(SEM) showed that the ZnO:Al thin films were(002) oriented. The resistivity values were measured by four-point probe with the lowest resistivity of 5.76×10~(-4) Ω?cm(sheet resistance=9.6 Ω/sq. for a thickness=600 nm) obtained at the PAr of 0.3 Pa. The transmittance was achieved from ultravioletvisible(UV-VIS) spectrophotometer, 84% higher than that in the visible region for all AZO thin films. The properties of deposited thin films showed a significant dependence on the PAr.     

Synthesis Mechanism and Material Characterization of C<Subscript>4</Subscript>AF Obtained by the Self-propagating Combustion Reaction Method

To investigate the influence of preparation process on the properties of synthesized C₄AF, the powder was prepared via the self-propagating combustion reaction (SPCR) method using urea as fuel and metal nitrates as cation precursors. Synthesis mechanism of the SPCR method, calculation and adjusting principles of urea dosage were detailedly introduced. Material characterization of synthesized C₄AF was performed with the aid of X-ray diffractometry, Fourier transform infrared spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, ²⁷Al nuclear magnetic resonance and isothermal microcalorimetric technique. Remaining content of transition phase of calcium carbonate in synthesized C₄AF was determined by quantitative analysis of X-ray diffractometry. It was found that there was no difference in the hydration behavior of C₄AF synthesized by the SPCR method and the traditional solid-state reaction (SSR) method. C3AH6 and amorphous iron (III) hydroxide (Fe(OH)₃) would be formed during the hydration of C4AF while CH not. Crystallite size of synthesized C₄AF was 16.1 Å and the apparent activation energy was 36.2 kJ/mol. Coordinated condition of Al in C₄AF can be detected by ²⁷Al NMR technique, but the peaks were broadened and the intensities were relatively low, supporting the use of ²⁷Al NMR for the quantitative analysis of C₃A in Portland cements.     

Thermodynamic calculation on the smelting slag of direct recycling of electric arc furnace stainless steelmaking dust

1　ＩＮＴＲＯＤＵＣＴＩＯＮＥｌｅｃｔｒｉｃａｒｃｆｕｒｎａｃｅ (ＥＡＦ)ｄｕｓｔｈａｓｂｅｅｎｃｌａｓｓｉｆｉｅｄａｓａｈａｚａｒｄｏｕｓｗａｓｔｅｄｕｅｔｏｉｔｓｈｉｇｈｃｏｎｔｅｎｔｏｆｓｏｍｅｈｅａｖｙｍｅｔａｌｓｌｅａｃｈａｂｉｌｉｔｉｅｓｓｕｃｈａｓｚｉｎｃ ,ｌｅａｄ ,ｃａｄｍｉｕｍａｎｄｃｈｒｏｍｉｕｍ ,ｓｏｉｔｈａｓｂｅｅｎｂａｎｎｅｄｆｒｏｍｌａｎｄｆｉｌｌｓｉｎｍａｎｙｃｏｕｎ ｔｒｉｅｓ .Ａｎｅｓｔｉｍａｔｅｄ 1 % 2 %ｍａｓｓｆｒａｃｔｉｏｎｏｆｔｈｅｓｃｒａｐｃｈａｒｇｅｄ…     

Influence of crucible material on the microstructure and properties of iron rich glass-ceramics

Slag glass melting is usually performed on a laboratory scale in crucibles, which are economically viable tools for the production of slag glass-ceramics. In this work, quaternary CaO-Al₂O₃-MgOSiO₂ (CAMS) glass-ceramics were prepared by melting the tailing of Bayan Obo mine tailing, blast furnace slag, and fly ash in alumina and graphite crucibles. The effect of the crucible material on the microstructure and properties of the glass-ceramics was investigated using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectroscopy. Results indicated that the contents of Al₂O₃ and Fe₂O₃ in the initial glass were significantly changed by the corrosion of the alumina crucibles during the glass melting process and by the reducing action of the graphite crucibles. The main crystal phases of glass-ceramics melted in alumina crucibles and graphite crucibles were Ca (Mg, Fe, Al) (Si, Al)₂O₆, coesite and Ca (Mg, Al) (Si, Al)₂O₆, respectively. According to these findings, we conclude that the microstructure and properties of the glass-ceramics are affected by the crucibles.     

The Microstructure and Properties of Diffusion Layer of Spray Aluminum

After diffusion processing of thermal spraying , aluminum on 20^# steel is discussed in this article. Variations of microstructure, composition as well as mierohardness and corrosion resistatwe of diffusion layer of spray aluminum were explored by means of X-ray diffraction, scanning electron microscopy （SEM） and electron probe microanlysis （ EPMA ） . The result shows that the diffusion layer of spray aluminum consists of η phase （ Fe2Al5 ）, ξ phuse （ FeAl2 ）, β2 phase （ FeA1 ）,β1 plmse （ Fe3Al ） and α pluse from surface to substrate. There are balanced transitions between phases. The layer has extra high hardness and corrosion resistance.     

Extraction of nickel from molybdenum leaching residue of metalliferous black shale by segregation roasting and acid leaching

The recovery of nickel from molybdenum leach residue by the process of segregation roasting-sulfuric acid leaching-solvent extraction was investigated. The residue was characterized by microscopic investigations, using X-ray fluorescence spectrometry (XRF) and X-ray diffractometry (XRD) techniques and the residue after segregation roasting was characterized by chemical phase analysis method. A series of experiments were conducted to examine the mass ratio of activated carbon (AC) to the residue, segregation roasting time and temperature, sulfuric acid concentration, liquid-to-solid ratio, leaching time, leaching temperature, addition amount of 30% H₂O₂, stirring speed (a constant) on the leaching efficiency of nickel. A maximum nickel leaching efficiency of 90.5% is achieved with the mass ratio of AC to the residue of 1:2.5, segregation roasting time of 2 h, segregation roasting temperature of 850 °C, sulfuric acid concentration of 4.5 mol/L, liquid-to-solid ratio of 6:1, leaching time of 5 h, leaching temperature of 80 °C, addition of 30% H₂O₂ of 0.6 mL for 1 g dry residue. Under these optimized conditions, the average leaching efficiency of nickel is 89.3%. The nickel extraction efficiency in the examined conditions is about 99.6%, and the nickel stripping efficiency in the examined conditions is about 99.2%.     

Effect of Mg/Al ratios on hydration mechanism of tabular alumina carbon composites reinforced by Al<Subscript>4</Subscript>C<Subscript>3</Subscript> in situ reaction

Hydration mechanism of tabular alumina carbon composites reinforced by Al₄C₃ in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 °C to 85 °C. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 °C-84 °C in H₂O(g). The hydration was controlled by diffusion from 24.7 °C to 33 °C. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al₄C₃ crystals at high temperature. Besides, the matrix changes into the Al₄C₃ with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al₄C₃ in situ reaction was immersed in the wax at suitable temperature or storing them below 33 °C in a dry place or storing them with paraffin-coating.     

Influence of Polyepoxysuccinic Acid on Solid Phase Products in Portland Cement Pastes

The influence of polyepoxysuccinic acid(PESA) on the solid phase products in hydrated Portland cement pastes was investigated by isothermal calorimetry, X-ray diffraction(XRD), ²⁹Si and ²⁷Al nuclear magnetic resonance(NMR). The results indicated that PESA bonds Ca²⁺ ions in pore solution to prevent portlandite formation, and also combines with Ca²⁺ ions on the surface of silicate minerals to prolong the control time of phase boundary reaction process, leading to the retardation of silicate mineral hydration. Meanwhile, the interlayer Ca²⁺ ions in Jennite-like structure bridging PESA and C-S-H gels prevent silicate tetrahedron and aluminum tetrahedron from occupying the sites of bridging silicate tetrahedron, which causes the main existence of dimer in C-S-H structure, deceases the degree of Al³⁺ substituting for Si⁴⁺ and promotes the transformation from 4-coordination aluminum to 6-coordination aluminum. Furthermore, the -Ca⁺ chelating group from reacting PESA with Ca²⁺ ions combines easily with SO₄^2- ions, resulting in transformation from ettringite, AFm to TAH(Third aluminum hydrate). However, with the higher addition of PESA, it will bridge the excess PESA by Ca²⁺ ions to form a new chelate with ladder-shaped double chains structure, which not only reduces the amount of PESA bonding Ca²⁺ ions, but also decreases its solidifying capability for SO₄^2- ions, leading to the transformation from TAH to AFm or ettringite. Meanwhile, at later hydration, the inhibition effect of PESA on cement hydration is weakened, and the transformation degree from TAH to AFm is higher than that to AFt with the addition of PESA.     

Double-layer modification of water-based aluminum with SiO<Subscript>2</Subscript> and polyacrylic acid by sol-gel process and in situ polymerization

A double-layer aluminum consisting of an aluminum core and a shell of SiO₂ and polyacrylic acid was synthesized. This modified aluminum was used to improve the corrosion resistance and dispersive property of aluminum in waterborne media. TEM, FTIR, XPS, and EDX determination showed that PAA and SiO₂ were coated on the surface of aluminum. Evolved hydrogen detection showed that the corrosion resistance of composite particle had been markedly improved. Maximum corrosion inhibition efficiency of SiO₂ coated aluminum (SiO₂@Al) was 95.1% while that of double-layer coated aluminum (PAA/SiO₂@Al) was 98.8%. Meanwhile, polyacrylic acid layer improved the agglomeration of aluminum significantly. According to the dispersibility test, the particle size of 50% volume fraction [d(0.5)] of aluminum, SiO₂@Al and PAA/SiO₂@Al were 42, 53, and 34 μm, respectively.     

Production of Reduced Iron Powder Using Ultra-Fine Iron Concentrate

1　IntroductionWiththedevelopmentofthepowdermetallurgytech nologyinChina ,theresearchofpowdermetallurgyproductaimsathighdensity ,highintensity ,highprecisionandcomplicateshape .Withironpowdersasthemainrawma terialofpowdermetallurgyproduct,thequalityofironpowderhasanimportantinfluenceonthepropertiesofpowdermetallurgyproduct.Soitisimportanttoexploitre ducedironpowder.Andthenecessarypresuppositionistogethigh gradepureiron .Atabroad ,reducedironpowderisproduceddirectlyfromironoreinmostfactories ,…     

Synthesis of M (M=Co<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>/Ni<Superscript>2+</Superscript>)-doped FeS<Subscript>2</Subscript> Nanospheres with Enhanced Visible-light-induced Photocatalytic Activity

Nano-spherical Co²⁺-doped FeS₂ was synthesized through a simple solvothermal method. The products were investigated using XRD, FE-SEM, BET, ICP, EDS, TEM, HRTEM, XPS, and UV-vis spectroscopy. The results indicated that Co²⁺ ion could change the particle nucleation process and inhibited the particle growth of FeS₂. In addition, when the content of doped Co²⁺ was 15%, the degradation efficiency of methylene blue (MB) achieved 60.72% after 210 min irradiation, which increased by 52.01% than that of the undoped FeS₂. Moreover, comparison experiments also demonstrated that the M (M=Co²⁺, Co²⁺/Ni²⁺)-doped FeS₂ photocatalytic activity efficiency sequence was Co²⁺ > Ni²⁺>Co²⁺/Ni²⁺. This is ascribed to the fact that the Co²⁺ doping could induce the absorption edge shifting into the visible-light region and increased the surface area of the samples. The effect mechanisms of M-doping on the band gap and the photocatalytic activity of FeS₂ were also discussed.     

Separation of red (Y2O3: Eu3+), blue (Sr, Ca, Ba)10(PO4)6Cl2: Eu2+ and green (LaPO4: Tb3+, Ce3+) rare earth phosphors by liquid/liquid extraction

A novel process for separation of red (Y₂O₃: Eu³⁺), blue (Sr, Ca, Ba)₁₀(PO₄)₆Cl₂: Eu²⁺ and green (LaPO₄: Tb³⁺, Ce³⁺) fine tricolor phosphor powders was established. First, the green phosphor was extracted and separated from three phosphor mixtures in heptane/DMF(N, N-Dimethylformamide) system using stearylamine or laurylamine (DDA) as the cationic surfactant. Then, after being treated with 99.5% ethanol, the blue and red phosphors could be separated in Heptane/DMF system in presence of 1-octanesulfonic acid sodium salt as the anionic surfactant. Satisfactory separation results have been achieved through two steps extractions with their artificial mixtures. The grades and recovery of separated products reached respectively as follows: red product was 95.3% and 90.9%, blue product was 90.0% and 95.2%, and green product was 92.2% and 91.8%. Funded by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (ROCS, SEM [2005] No. 383)     

Preparation and properties of alkali activated foam cement reinforced with polypropylene fibers

A new form of foam cement was produced by mixing alkali-activated slag,clay,a small amount of polypropylene fibers with prepared foam during stirring.The preparation of the material is quite different from the normal one,which is produced just at room temperature and without baking.The fabrication of this energy-saving and low-price material can be favorable for lowering carbon emission by using recycled industrial wastes.Thermal conductivity of 0.116 W/(m·k),compressive strength of 3.30 MPa,flexural strength of 0.8 MPa and density of 453 kg/m3 can be achieved after 28 days aging.The hydration product is C-S-H with less Ca(OH)2,calcium aluminum and zeolite,which was characterized by X-ray diffraction(XRD) measurement.This prospective foam cement may be expected to be an excellent economical energy-saving building material.