Reactions of uranium oxysulfide with some nonmetals and metals

Conclusions A study was made, using the optical microscopy and x-ray diffraction techniques, of the reactions of uranium oxysulfide with boron, silicon, lanthanum, and yttrium in the temperature range 1000–1700°C. Boron and silicon cannot be employed as reducing agents in the synthesis of uranium monosulfide from uranium oxysulfide. It was established that in the operation of a reactor UOS present in sulfide fuel is a harmful impurity because it reacts with lanthanides forming in the course of fission.Translated from Poroshkovaya Metallurgiya, No. 10(166), pp. 97–100, October, 1976.The author wishes to thank Professor D. Kolar for helpful discussion. He is also most grateful to the Boris Kidri Fund for financing the work.     

Carbothermic reduction of zinc sulfide in the presence of calcium carbonate

Carbothermic reduction of zinc sulfide in the presence of calcium carbonate was investigated by employing an X-ray diffractometer (XRD), a carbon and sulfur determinator, a scanning electron microscope (SEM), an energy-dispersive X-ray analysis (EDX), and a surface area analyzer. Experimental results revealed that calcium carbonate was completely decomposed to CaO in the initial stage and CaO was then involved in the carbothermic reduction of zinc sulfide to scavenge sulfur content as CaS remained in the solid. Only carbothermic reduction of zinc sulfide occurred after the initial stage. Most β-ZnS transformed to α-ZnS in the initial stage. Sintering became severe after long reaction time or at high reaction temperature. The surface area of a sample decreased drastically in the initial stage and then increased with the reaction time; the pore volume of the solid sample was also reduced more quickly initially and then kept constant; the average pore diameter, however, reduced slightly in the initial stage and then leveled off. The effect of temperature on the changes of pore surface area, pore volume, and average pore diameter was found to be similar to that of time, except in the initial stage. A reaction mechanism and a reaction model were proposed to interpret the overall reaction.     

高铟高铁闪锌矿电炉熔炼回收金属锌和铟的生产实践

介绍了高铟高铁闪锌矿电炉炼锌回收金属锌和铟的工艺流程及生产实践。实践表明,电炉炼锌有利于高铁闪锌矿资源的综合利用,可提高金属的回收率和综合利用率。     

Electrochemical oxidation of nickel sulfide metallic alloys

The sequence of the electrochemical oxidation of phase components of the converter matte is confirmed and variations in the composition of its surface during the anode oxidation are revealed. It is shown that regularities of this process that are characteristic of its phase components, namely, nickel and its sulfides, are inherent to the converter matte. The oxidation of nickel sulfides in sulfide-metallic alloys starts at lower potentials (1.1–1.2 V) than that of synthesized nickel sulfide (1.2–1.3 V). During the oxidation of the converter matte, metal nickel initially oxidizes and, only as this stage finishes, the oxidation of sulfides accompanied by the isolation of elemental sulfur is developed. Copper impurities weakly affect the oxidation of the converter matte, although the shift of potentials takes place as the Cu/Ni ratio increases.     

Oxidation of dense iron sulfide

Oxidation of stoichiometric iron sulfide was investigated. Rectangular plates of dense FeS were oxidized in an Ar-O₂ gas mixture at 1023 to 1123 K. Oxygen partial pressure was varied between 1.01 × 10³ and 2.03 × 10⁴ Pa. During the initial five minutes of oxidation, a magnetite layer of about 10 μm in thickness was formed on the surface without the evolution of SO₂ gas. Diffusion of iron from the interior of the sulfide to the sulfide/magnetite interface controlled the oxidation rate. Mass transfer through the gaseous boundary layer at the sample surface also affects the oxidation rate at lower oxygen partial pressures. Following this rapid formation of magnetite, the magnetite layer continued to grow for several hours in accordance with the parabolic rate law. Diffusion of iron through the magnetite layer controlled the oxidation rate during this stage. A thin layer of hematite was also formed on the outer surface of magnetite. When the composition of the inner sulfide core reached Fe_0.9S, the oxidation proceeded irregularly into the interior of the remaining sulfide. Porous oxide was formed and SO₂ gas was evolved. Former Graduate Student     

Thermodynamic and experimental study of high-temperature roasting of blast furnace gas ash for recovery of metallic zinc and iron

A high-temperature reduction roasting method was used to achieve metallic iron and zinc recovery from blast furnace gas ash(BFA).The reduction processes for Zn-containing and Fe-containing oxides were analyzed in detail by using ther-modynamic equilibrium calculation and the principle of minimum free energy.The results showed that the main reaction in the system is the reduction of ZnFe2O4 and iron oxides.Over the full temperature range,iron oxides were more easily reduced than zinc oxides.Regardless of the amount of CO contained in the system,the reduction of ZnO to Zn was difficult to proceed below the boiling point(906 ℃)of Zn.When the reduction temperature is below 906 ℃,the reduction process of zinc ferrate was ZnFe2O4 → ZnO;when the reduction temperature is above 906 ℃,its reduction process becomed ZnFe2O4 → ZnO → Zn(g).The metallization and dezincification rates of the BFA gradually increased with increasing reaction temperature.As the C/O ratio increased,the metallization and dezincification rates first increased and then decreased.The effect of reduction time on BFA reduction was similar to that of reaction temperature.     

Reduction roasting of high iron bearing zinc calcine for recovery of zinc and iron

High iron bearing zinc sulphide ore is an important resource for zinc, and the reserve is very great in the world. It is very difficult to effectively obtain zinc and iron from the source by traditional technology. In this study, a novel method was proposed for recovery of zinc and iron from high iron bearing zinc calcine, and the key procedure, reduction roasting, was investigated. The effects of CO concentration, CO₂ concentration, temperature and time on reduction roasting were studied respectively. The experimental results show that the content of soluble zinc and magnetic susceptibility reached 91·15% and 4·1×10^?4 m³ kg^?1 under the optimum conditions respectively. About 90%Zn and 9·5%Fe were dissolved from the reduction roasted zinc calcine by low acid leaching, and simultaneously, 84·3%Fe was recycled to the iron concentrate containing iron of 53·2% from zinc leaching residue by low intensity magnetic separation.

Le minerai de sulfure de zinc à haute teneur en fer est une ressource importante du zinc et il en existe une grande quantité dans le monde. Il est très difficile d’obtenir efficacement le zinc et le fer de cette source par la technologie traditionnelle. Dans cette étude, on propose une nouvelle méthode pour la récupération du zinc et du fer à partir de produit calciné de zinc à haute teneur en fer, et on examine la procédure clef, le grillage réducteur. On a étudié respectivement les effets de la concentration de CO, de la concentration de CO₂, de la température et de la durée sur le grillage réducteur. Les résultats expérimentaux montrent que la teneur en zinc soluble et la susceptibilité magnétique atteignaient respectivement 91·15% et 4·1×10^?4 m³ kg^?1 en conditions optimales. Environ 90% du Zn et 9·5% du Fe étaient dissous à partir du produit calciné de zinc de grillage réducteur par lessivage à acide faible, et simultanément, 84·3% du Fe était recyclé en concentré de fer contenant 53·2% de fer à partir du résidu de lessivage du zinc par séparation magnétique à faible intensité.     

Activity-composition relations at 1100°C in the system calcium oxide-iron oxide-manganese oxide in contact with metallic iron

The extent of the solid miscibility gap in the system CaO−“FeO”−MnO at 1100°C has been determined termined by electron microprobe, point-counting, and X-ray diffraction analysis of coexisting phases within the miscibility gap. Activities of FeO in ternary solid solutions have been determined at 1100°C by equilibrating the solid solutions with metallic iron and a gas phase of known oxygen pressures. Activity-composition curves for CaO and MnO in the ternary system are calculated from a Gibbs-Duhem integration, and the data are extrapolated to the binary system CaO−MnO, which is shown to display a considerable positive deviation from ideality at 1100°C. NILS TIBERG, formerly Graduate Assistant, Department of metallurgy, The Pennsylvania State Univeristy, University Park, Pa.     

Effect of source of iron on duodenal absorption of iron, calcium, phosphorous, magnesium, copper and zinc in rats with ferropoenic anaemia

The purpose of this study was to undertake a critical review of the potential role of magnetic resonance imaging (MRI) in the evaluation of low back pain (LBP) and to determine if there were differences in the MRI appearances between various occupational groups. The study group, 149 working men (78 aged 20-30 years and 71 aged 31-58 years) from five different occupations (car production workers, ambulance men, office staff, hospital porters and brewery draymen), underwent MRI of the lumbar spine. Thirty-four percent of the subjects had never experienced LBP. Twelve months later, the examination was repeated on 89 men. Age-related differences were seen in the MRI appearances of the lumbar spine. Disc degeneration was most common at L5/S1 and was significantly more prevalent (P < 0.01) in the older age group (52%) than in the younger age group (27%). Although LBP was more prevalent in the older subjects there was no relationship between LBP and disc degeneration. No differences in the MRI appearance of the lumbar spine were observed between the five occupational groups. Overall, 45% had 'abnormal' lumbar spines (evidence of disc degeneration, disc bulging or protrusion, facet hypertrophy, or nerve root compression). There was not a clear relationship between the MRI appearance of the lumbar spine and LBP. Thirty-two percent of asymptomatic subjects had 'abnormal' lumbar spines and 47% of all the subjects who had experienced LBP had 'normal' lumbar spines. During the 12-month follow-up period, 13 subjects experienced LBP for the first time. However, there was no change in the MRI appearances of their lumbar spines that could account for the onset of LBP. Although MRI is an excellent technique for evaluating the lumbar spine, this study shows that it does not provide a suitable pre-employment screening technique capable of identifying those at risk of LBP.     

Dephosphorization of silico-manganese alloys under reducing atmosphere with metallic calcium

Dephosphorization of silico-manganese ferroalloy with metallic Calcium was investigated under sealed and open conditions. Effects of the initial Si content in silico-manganese melts, the adding amount of Ca chips and flux CaF₂, the time of dephosphorization and the initial C content in silico-manganese melts upon dephosphorization efficiency were ascertained by experiment. The dephosphorization product was identified as Ca₃P₂ upon stoichiometric composition. Experimental results show that dephosphorization efficiency, rather high, from 95 % to 99 % could be obtained by adding Ca under sealed conditions and a high Ca utilization ratio was obtained.     

Oxidation of zinc sulfide in a fluidized bed

Kinetics of oxidation of ZnS particles in a batch-type fluidized bed were studied at temperatures between 800 and 910°C. A two-phase model was employed for the fluidized bed, and the partial pressure of oxygen and the gas-film mass transfer coefficient on the particle surface were separately evaluated in gas bubbles and in the emulsion phase. The calculated fractional reaction coincided well with the experimental results. The difference in O₂ partial pressure between gas bubbles and emulsion phase was found to be fairly large especially under the vigorous fluidizing condition. Furthermore, it was shown from the mathematical model that the reaction of ZnS particles in the gas bubbles is negligible because of the extremely low solid concentration and that the overall rate of reaction in the emulsion phase is virtually controlled by the rate of gas-film mass transfer at higher temperature. The resistance of interfacial reaction within the particle also becomes significant when the temperature is lowered. Y. Fukunaka and T. Monta are both former Graduate Students, Kyoto University, Kyoto, Japan.     

Leaching of a limonitic laterite in ammoniacal solutions with metallic iron

The leaching of a limonitic laterite (containing approximately 1% Ni, 0.1% Co and 50% Fe) was studied in ammoniacal solution. The laterite was leached in the presence of metallic iron which acted as a reductant. The kinetic parameters studied included the effect of temperature, metallic iron concentration, total ammonia concentration and ammonium sulphate to ammonium hydroxide ratios. Tests were performed in a batch cell with temperature ranging from 50 to 80 °C at atmospheric pressure. The kinetic behavior for nickel and cobalt extraction was observed to be different. Cobalt extraction was initially faster than nickel and it showed good extractions at lower temperatures, however, after reaching a maximum value of approximately 80%, extraction decayed by as much as 50%. This was likely due to cobalt co-precipitation and/or adsorption into iron and/or manganese oxides and hydroxides which could form during the process. Cobalt losses tended to increase with temperature, total ammonia concentration, ammonium hydroxide to ammonium sulphate ratio and metallic iron concentration. Nickel extraction was increased by higher temperature, total ammonia concentration and metallic iron concentration up to a maximum of roughly 70% after 48 h at 80 °C.Through feed and solid residue analysis, by X-ray diffraction and SEM, it was possible to characterize and understand how the feed mineral reduction occurred. The main phases present in the feed and residue were goethite and magnetite, respectively. Results suggest that the reduction occurs through two main reactions. First, the reaction between goethite and metallic iron produced Fe(II) ammines. The Fe(II) ammines are capable of reducing goethite and producing magnetite. The Fe(II) ammines play an important role because they accelerate the reduction and favor the extraction kinetics of nickel. The main advantage of using metallic iron as a reducing agent is the possibility of generating an autocatalytic system.     

Interaction of zinc with a synthetic calcium phosphate mineral

As zinc has been included in several oral health products as an anticalculus and antiplaque agent, the interaction of zinc with a synthetic phosphate was investigated. The synthetic calcium phosphate used in this study was beta-tricalcium phosphate, or whitlockite, which is a major constituent of mature calculus. The aim of this work was to study the mechanism of uptake of zinc to this mineral. Zinc was readily taken up by the calcium phosphate to a maximum level of 13.9 mumol/m2. The interaction was reversible and followed a Langmuir adsorption isotherm. There was no concomitant release of calcium with zinc uptake. Inclusion of calcium in the exposure solution did however marginally depress the acquisition of zinc (12% max), but fluoride had no significant effect on uptake.     

Kinetics of zinc oxide formation from zinc sulfide by reaction with lime in the presence of water vapor

A novel reaction scheme for transforming certain metal sulfides to the corresponding oxides has been developed. In this process, steam oxidizes the sulfide into the oxide, and the hydrogen sulfide produced reacts with lime to form calcium sulfide and regenerate steam. There is no net consumption or generation of gaseous species. Thus, the overall reaction can be carried out in a closed system as far as the gas phase is concerned. This eliminates the possibility of emitting hydrogen sulfide out of the reactor. Only certain metal sulfides are thermodynamically amenable to this treatment. In this paper, the reaction of ZnS to ZnO by this scheme is described, together with a detailed formulation of the rate equation for the overall reaction based on the kinetics of the component gas-solid reactions. Although the present work was done with CaO, other suitable oxides may be used in its place. A further potential application of this process is to the selective oxidation of certain sulfide(s) from complex sulfide ores as a treatment prior to the separation of minerals.     

浅谈硫化锌精矿备料设计

介绍了硫化锌精矿的特征、类别,备料过程中的关键环节及必须注意的问题.叙述了备料设计的基本要求以及设计中的经验体会.     

Effect of zinc addition to copper in improving its corrosion resistance in sulfide polluted synthetic seawater

In an endeavor to develop a cost effective substitute of Cu-10Ni alloy for seawater application (especially for sulfide polluted seawater) few Cu-Ni-Zn-Mn alloys were developed in our laboratory. The Cu-Ni-Zn-Mn alloy was found to have better corrosion resistance than Cu-10Ni both in clean and sulfide polluted synthetic seawater. Resistance to sulfide in Synthetic Seawater was attributed to the formation of ZnS. To ensure that the resistance to sulfide attack is due to Zn alone, a series of studies were carried out with binary alloys of Cu and Zn with increasing weight percentage of Zn (12% and 36%). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) was used for the purpose. Polarization studies gave the corrosion data and EIS was effective in depicting the nature of corrosion product (film). It was found that among the test alloys, Cu-36Zn is most corrosion resistant in sulfide polluted seawater due to formation of ZnS in the film. As it is a binary alloy, the corrosion resistance against sulfide is attributed to Zn alone.     

Agglomeration of particles during roasting of zinc sulfide concentrates

This study was undertaken in an attempt to explain the agglomeration of zinc concentrate particles that occurs during fluid bed roasting. In order to simulate extensive particle contact, pure ZnS, FeS, and (Zn, Fe)S particles were roasted in a fixed bed at temperatures between 1223 K and 1323 K using an argon-oxygen gas mixture withP _O2 = 0.21 atm. The results were compared to the reaction products and morphology of an agglomerated commercial concentrate. The reactants were contained in MgO crucibles suspended in a thermobalance and the weight change was recorded as the reaction proceeds. The resulting data were used to identify the specific reaction that takes place for each of the reactants. Products were identified by X-ray diffraction analysis. The morphology of the products was analyzed using SEM and confirmed that the formation of a liquid phase composed of a solution of Fe-S-O causes particles to stick to each other, thus causing agglomeration. This phenomenon was observed for both the FeS and (Zn, Fe)S samples but not for the ZnS. The morphology and the X-ray diffraction pattern of the reaction products of the synthetically prepared (Zn, Fe)S showed remarkable similarity to that of the roasted industrial concentrate.     

Leaching of zinc sulfide in alkaline solution via chemical conversion with lead carbonate

A novel hydrometallurgical process for recovering Zn from ZnS in alkaline solution via chemical conversion with PbCO₃ was developed in this work. The S originally present in ZnS can be converted into PbS, while the Zn can be converted into Na₂Zn(OH)₄ in the alkaline solution in the presence of PbCO₃. And then, the Pb in PbS deposited in the leach residues can be converted into PbCO₃ again in the Na₂CO₃ solution. It was found that over 90% of Zn can be extracted from ZnS when the leaching process is operated in 6 mol/L NaOH solution at 90 °C with PbCO₃ as additive, and over 95% of PbS in the leach residues can be converted into PbCO₃ by stirring the leach residues in Na₂CO₃ solution with air bubble at a temperature of 80 °C. The leaching solution can be used to produce metallic zinc powder by electrowinning after chemical separation of impurities.