Treatment of Cr(VI) in COPR Using Ferrous Sulfate–Sulfuric Acid or Cationic Polysulfides

Column tests were conducted to evaluate two treatment strategies for reducing and stabilizing hexavalent chromium, Cr(VI), in chromium ore processing residue (COPR): permeation with a FeSO4–H2SO4 solution and blending with a cationic polysulfide reagent (CaSX). Cr(VI) leached at concentrations exceeding 50?mg/L from untreated COPR permeated with synthetic groundwater for >20 pore volumes of flow (PVF), and concentrations of Cr(VI) in the solid phase remained high (6,600?mg/kg). Permeation with solutions containing FeSO4–H2SO4 eliminated Cr(VI) from the effluent after initial, elevated leaching of Cr(VI) (100–1,500?mg/kg); however, high solid-phase concentrations of Cr(VI) remained in the column residuals (>1,300?mg/kg). COPR treated with CaSX leached Cr at <0.33?mg/L for 23.5 PVF and had solid-phase concentrations of Cr(VI) <10?mg/kg, although mineralogical analyses of treated solids showed potential chromate-containing mineral phases. Mineralogical analyses showed that precipitation and cementation occurred in the pore space of the COPR permeated with FeSO4–H2SO4, initially lowering the hydraulic conductivity > two orders of magnitude. However, acid dissolution channels eventually formed, resulting in preferential flow. COPR permeated with FeSO4–H2SO4 contained less brownmillerite and Cr(VI)-bearing hydrocalumite and hydrogarnet relative to untreated COPR. For COPR treated with CaSx, S encapsulated the subparticles of COPR with some micropore penetration, suggesting permanence of excess reductant after leaching with 23.5 PVF of synthetic rainwater.     

Study of Complexes Formed by Adrenaline with Nd~(3+),Gd~(3+) and Tm~(3+)

The solution reaction mechanisms,composition,donor atoms,properties of coordinate link and stability ofthe complexes on the systems of adrenaline with Na~(3+),Gd~(3+)and Tm~(3+)have been studied by pH-potentiometrictitration and electronic spectroscopy.Adrenaline perturbs the f-f electronic transition of Nd~(3+)and Tm~(3+)sothat the absorption spectra of their complexes are shifted toward longer wavelengths.The absorption spectra ofthe complexes formed by the three f-block element ions with adrenaline are shifted toward shorter wavelengthswith the increase of PH in Δγ=350～650 nm     

Centrifugal Metallothermic SHS of Cast Co–Cr–Fe–Ni–Mn–(Х) Alloys

Russian Journal of Non-Ferrous Metals - A relatively new approach to obtaining metal materials containing several principal elements in equiatomic concentrations which look promising for replacing...     

Microstructural characterisation of Ti–Nb–(Fe–Cr) alloys obtained by powder metallurgy

Abstract

β alloys based on the Ti–Nb alloy system are of growing interest to the biomaterial community. The addition of small amounts of Fe and Cr further increases β-phase stability, improving the properties of Ti–Nb alloy. However, PM materials sintered from elemental powders are inhomogeneous due to restricted solid state diffusion and mechanical alloying provides a route to enhance mixing and elemental diffusion. The microstructural characteristics and bend strength of Ti–Nb–(Fe–Cr) alloys obtained from elemental powder mixture and mechanical alloyed powders are compared. Mechanical alloying gives more homogeneous compositions and particle morphology, characterised by rounded, significantly enlarged particles. In the sintered samples α and β phase are observed. The α phase appears at the grain boundaries and in lamellae growing inward from the edge, and is depleted in Nb. The β phase is enriched with Nb, Fe and Cr. The addition of Fe and Cr significantly increases the mechanical properties of Ti–Nb alloys, providing increased ductility.     

Studies of Disulfoxide Complexes of Lanthanide Ⅴ.Lanthanide Perchlorate Complexes with Meso-bis(phenylsulfinyl)ethane

Lanthanide perchlorate complexes with meso-bis(phenylsulfinyl)ethane(meso-BPhSE)of type[LnL_3-ClO_4](ClO_4)_2,where Ln=La～Nd,Sin,Gd～Ho,Tm～Lu,have been prepared and characterized by elementalanalysis,electrical conductance,infrared and electronic spectra,magnetic moment measurement and thermalanalysis.Meso-BPhSE acts as a neutral ligand which combines with lanthanide ion through oxygen atom ofdisulfoxide moieties.In all complexes,except that of Ho,meso-BPhSE does not behave as a complete bidentatechelate but does coordinate,at least partially,as a monodentate ligand.For the Ha complex all meso-BPhSEacts as bidentate ones.     

Electrochemical co-reduction of Y(III) and Al(III) in a fluoride molten salt system and electrolytic preparation of Y–Al intermediate alloys

In this study, a molten salt co-reduction method was proposed for preparing Y–Al intermediate alloys and the electrochemical co-reduction behaviors of Y(III) and Al(III) and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques. The results show that the reduction of Y(III) at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons, which is controlled by the mass transfer rate. The diffusion coefficient of Y(III) in the fluoride salt at a temperature of 1323 K is 5.0238 × 10^?3 cm²/s. Moreover, the thermodynamic properties associated with the formation of Y–Al intermetallic compounds were estimated using a steady-state electrochemical method. Y–Al intermediate alloy containing 92 wt% yttrium was prepared by constant current electrolysis at 1323 K in the LiF–YF₃–AlF₃–Y₂O₃ (6 wt%)–Al₂O₃ (1 wt%) system at a cathodic current density of 8 A/cm² for 2 h. The Y–Al intermediate alloy is mainly composed of α-Y₂Al and Y phases. The development and application of this innovative technology have solved major technical problems, such as a long production process, high energy consumption, and serious segregation of alloy elements at this stage.     

Diffusion coefficients of the uranium(III) and (IV) ions in the LiCl–KCl–CsCl eutectic melt

Diffusion coefficients of the uranium(III) and (IV) ions in the eutectic melt of the lithium, potassium, and cesium chlorides in the temperature range of 573–1073 K have been determined using two independent methods: cyclic voltammetry and chronopotentiometry.     

Luminescence Properties of Pyridine Carboxylic Acid-Europium (Ⅲ) Complexes

The luminescent properties of four pyridine carboxylic acid-europium complexes were investigated byinfrared absorption,fluorescence and time-resolved fluorescent spectroscopy.The influences of structure ofcomplex compounds,solvents and pH of the media on the emission intensity and the lifetime are discussed aswell.     

Determination of Formation Constants of Ce~(3 ) Complexes by Fluorescence

ＤｅｔｅｒｍｉｎａｔｉｏｎｏｆＦｏｒｍａｔｉｏｎＣｏｎｓｔａｎｔｓｏｆＣｅ３＋ＣｏｍｐｌｅｘｅｓｂｙＦｌｕｏｒｅｓｃｅｎｃｅＭｅｎｇＪｉａｎｘｉｎ（孟建新）（ＳｔａｔｅＫｅｙＬａｂｏｒａｔｏｒｙｏｆＵｌｔｒａＦａｓｔｓｔＬａｓｅｒＳｐｅｃｔｒｏｓ...     

Investigation into the Surface Layer Composition Formed on the Ml19 (Mg–Nd–Y–Zn–Zr) Magnesium Alloy during Melting under Protective Gas Atmospheres

Russian Journal of Non-Ferrous Metals - The most currently widespread method of flux-free melting of magnesium alloys is melting under a protective gas atmosphere consisting of inert carrier gas...     

Real–Time Speciation of Uranium during Active Bioremediation and U(IV) Reoxidation

The biological reduction of uranium from soluble U(VI) to insoluble U(IV) has shown potential to prevent uranium migration in groundwater. To gain insight into the extent of uranium reduction that can occur during biostimulation and to what degree U(IV) reoxidation will occur under field relevant conditions after biostimulation is terminated, X-ray absorption near edge structure (XANES) spectroscopy was used to monitor: (1) uranium speciation in situ in a flowing column while active reduction was occurring; and (2) in situ postbiostimulation uranium stability and speciation when exposed to incoming oxic water. Results show that after 70 days of bioreduction in a high (30?mM) bicarbonate solution, the majority (>90%) of the uranium in the column was immobilized as U(IV). After acetate addition was terminated and oxic water entered the column, in situ real-time XANES analysis showed that U(IV) reoxidation to U(VI) (and subsequent remobilization) occurred rapidly (on the order of minutes) within the reach of the oxygen front and the spatial and temporal XANES spectra captured during reoxidation allowed for real-time uranium reoxidation rates to be calculated.     

Electrochemical formation of Mg–La–Mn alloys by coreduction of Mg(II), La(III) and Mn(II) in LiCl+KCl molten salts

In the present work, cyclic voltammetry (CV), square wave voltammetry (SWV) and chronopotentiometry (CP) were used to investigate the electrochemical coreduction behaviors of La(III) and Mg(II) as well as La(III), Mg(II) and Mn(II) on Mo electrode in LiCl + KCl molten salts. CV and SWV results exhibit that the coreduction mechanism of La (III) and Mg(II) on Mo electrode is that La(III) is reduced and Mg–La intermetallic compound is formed, leading to the deposition potential of La(III) shifting to more positive one. The electrochemical signals pertaining to the formation of metallic La, Mg and Mn as well as Mg–La intermetallic compound are also observed by coreduction of La(III), Mg(II), and Mn(II) in LiCl + KCl molten salt on the inert Mo electrode. However, the electrochemical signals associated with the formation of La–Mn and Mg–Mn alloys are not observed, which means that the depolarization effect of La(III) and Mg(II) does not occur on pre-deposited Mn electrode. The Mg–La–Mn alloys were formed by co-deposition of La(III), Mg(II), and Mn(II) on Mo electrode at various concentration ratios of La(III) and Mg(II). The results of scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction displays that the Mg–La–Mn alloys are comprised of La–Mg compound Mg₁₇La₂, Mg and Mn phases. The concentration ratio of La(III) and Mn(II) has few effects on the alloy composition.     

Effect of chromium on the structure evolution in single-phase Ni–Cr alloys during high-pressure torsion

The evolution of the structure and the hardness of single-phase Ni–Cr alloys with 2–12.5 at % Cr is studied during high-pressure torsion. It is established that the hardness of the alloys, unlike pure nickel, continuously increases in the entire true strain range 0.2–12. Alloying with chromium is shown to substantially inhibit the formation of a submicrocrystalline structure and to enhance the refinement of microcrystallites.     

Luminescence of Eu(MBA)_2NO_3Phen Complexes

ＬｕｍｉｎｅｓｃｅｎｃｅｏｆＥｕ（ＭＢＡ）_２ＮＯ_３ＰｈｅｎＣｏｍｐｌｅｘｅｓＪｉｎＬｉｎ－ｐｅｉ（金林培）；ＴｏｎｇＪｉｎ－Ｑｉａｎｇ（童金强）；ＷａｎｇＭｉｎｇ－Ｚｈａｏ（王明昭）；（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＢｅｉｊｉｎｇＮｏ...     

Interaction of HfB2 with Nickel and Ni–20% Cr Alloy (Nichrome)

Powder Metallurgy and Metal Ceramics - Interaction in the Ni–HfB2 and NiCr–HfB2 systems is studied. No new reaction products are found to form in the system with pure nickel in...     

Synthesis of Ni(Cr)–hBN Nanocomposite by Mechanical Alloying and Its Thermodynamical Evaluation

Russian Journal of Non-Ferrous Metals - In the present study, the feasibility of fabricating an Ni(Cr)/hBN self-lubricating nanocomposite by mechanical alloying technique was studied. To achieve...     

Interaction of Titanium Diboride with Nickel and Ni–20% Cr Alloy (Nichrome)

Powder Metallurgy and Metal Ceramics - The interaction in the Ni–Ti–B and Ni–Ti–B–Cr systems along the Ni–TiB2 and (Ni–20% Cr)–TiB2 sections was...     

Triboluminescent Complexes of Rare Earth Ⅱ.Mixed-ligand Complexes of Eu~(3 ) with Thenoyltrifluoroacetone and Pyridine-N-Oxide or its Substitutive Derivatives

Five triboluminescent mixed-ligand complexes of Eu~(3 )with thenoyltrifluoroacetone(TTA)andpyridine-N-oxide or its substitutive derivatives have been prepared.They are all pale yellow crystalline com-pounds with the formula of Eu(TTA)_3·L(L=py NO.2-pie NO,3-pie NO,4-pic NO,bipy N_2O_2).Theirphysico-chemical properties have been studied with conductometry,UV and IR absorption and fluorescencespectroscopy.Once the complexes are touched or rubbed by a glass rod,they emit strong red triboluminescentlight which is similar to the characteristic fluorescence of Eu~(3 ).