Kinetics of continuous hydrogen reduction of copper from a sulfate solution

The objective of this experimental investigation was to obtain information on the reaction kinetics for the hydrogen reduction of copper from copper sulfate solutions in a continuous, countercurrent tubular reactor. Aqueous copper sulfate solution was introduced at the top of the reactor while hydrogen was sparged into the bottom. Separations of the bottom (liquid-solid) and overflow (gas-liquid) products were accomplished in individual high pressure separators. The rate of reaction increases with temperature up to about 180 to 220 °C depending on the residence time and thereafter levels off or decreases slightly. Feed solutions having a pH greater than 1.8 yielded a product which was contaminated with cuprus oxide. Over the range of this study, the operating pressure, and consequently the solubility of hydrogen in the aqueous reactant demonstrated negligible effect on the depletions. Likewise, very little change in depletions was observed beyond residence times of 10 minutes. Acid addition to the feed retarded the rate of reaction, whereas addition of sulfate ion increased the rate; these two observations agree with the results of previous investigators.     

Kinetics of hydrochloric acid leaching of smithsonite

The dissolution kinetics of smithsonite ore in hydrochloric acid solution has been investigated. As such, the effects of particle size (−180 + 150, −250 + 180, −320 + 250, −450 + 320 μm), reaction temperature (25, 30, 35, 40, and 45°C), solid to liquid ratio (25, 50, 100, and 150 g/L) and hydrochloric acid concentration (0.25, 0.5, 1, and 1.5 M) on the dissolution rate of zinc were determined. The experimental data conformed well to the shrinking core model, and the dissolution rate was found to be controlled by surface chemical reaction. From the leaching kinetics analysis it can be demonstrated that hydrochloric acid can easily and readily dissolve zinc present in the smithsonite ore, without any filtration problems. The activation energy of the process was calculated as 59.58 kJ/mol. The order of the reaction with respect to HCl concentration, solid to liquid ratio, and particle size were found to be 0.70, −0.76 and −0.95, respectively. The optimum leaching conditions determined for the smithsonite concentrate in this work were found to be 1.5 M HCl, 45°C, −180 + 150 μm, and 25 g/L solid to liquid (S/L) ratio at 500 rpm, which correspond to more than 95% zinc extraction. The rate of the reaction based on shrinking core model can be expressed by a semi-empirical equation as:

电位滴定法测定Ruthner法盐酸再生工艺流程酸洗液中游离盐酸浓度

采用Ruthner法盐酸再生工艺对酸洗液进行再生处理时,需要及时测定其游离盐酸浓度。当采用通过电位滴定法测定酸洗液中游离H+浓度得到游离盐酸浓度的方法时,酸洗液中Fe²⁺和Fe³⁺的存在会干扰测定。实验利用Ca-CaY(0.1mol/L EDTA-0.150mol/L CaCl₂溶液)作为掩蔽剂消除了酸洗液中大量Fe²⁺和少量Fe³⁺的干扰,实现了电位滴定法对Ruthner法盐酸再生工艺流程酸洗液中游离盐酸浓度的测定。试验结果表明,Ca-CaY掩蔽剂的加入不仅对游离酸的测定无影响,且可使pH值的突跃范围变窄;在采用电位滴定法时,设定终点判断阈值为10、终点判断范围pH=7～10、终点识别为最大,可避免pH=6附近的突跃对终点的影响从而获得准确的滴定终点。优化后确定Ca-CaY掩蔽剂用量为10mL。从Ruthner法盐酸再生工艺不同流程中各取1个酸洗液样品,按实验方法测定游离盐酸浓度,并采用间接法进行方法对比。结果表明,采用t检验验证,t为0.51～1.18,小于t(0.05,9...     

Kinetics of tungsten teioxide reduction by dey and humidified hydrogen

Conclusions An investigation into the kinetics of reduction of tungsten trioxide by dry and humid hydrogen has shown that water concentrations of up to 3 vol.% in the hydrogen have no effect on the kinetic characteristics of the process. At a temperature of 500°C slightly higher reaction rates are obtained at water contents of 1.5–3 vol.%. In the presence of palladium additions initial reaction rates grow. It has been established that, when the water content of the hydrogen does not exceed 3 vol.%, the reaction in the low-temperature reduction phase passes through a stage of/gb- W phase formation. Under these conditions the degree of dispersion of the end metallic product is practically independent of the degree of humidity of the hydrogen in the temperature range 450–600°C.Translated from Poroshkovaya Metallurgiya, No. 9(213), pp. 1–5, September, 1980.     

Leaching chalcopyrite with sodium chlorate in hydrochloric acid solution

Abstract

Sodium chlorate was used as an oxidant for the chalcopyrite leaching in a hydrochloric acid solution. The hydrochloric acid concentration has an important effect on the dissolution of chalcopyrite. The results indicate that stirring speed has a negligible effect on copper dissolution, suggesting that the reaction is not controlled by liquid phase diffusion. Chalcopyrite leaching is also affected by temperature. X-ray diffraction studies show that sulphide is oxidised to sulphate at temperatures less than or equal to 65°C, and at 85°C, it is oxidised to elemental sulphur during the leaching process. Studies of the effect of temperature on dissolution indicate that the leaching process is highly dependent on temperature for the range of 25–65°C. This result is consistent with the values for the activation energy at 25–45°C (60·0 kJ mol^?1) and 45–65°C (57·7 kJ mol^?1). Within these temperature ranges, the leaching process is controlled by a chemical reaction. However, at temperatures of 65–85°C, the activation energy in (0–180 min) is 28·17 kJ mol^?1, which suggests that the reaction is diffusion and chemically controlled during this stage. During the last stage (180–300 min) of the process at 65–85°C, the activation energy is only 0·55 kJ mol^?1. At this point, it appears that diffusion predominates. Scanning electron microscopy and energy dispersive X-ray spectroscopy results are consistent with the abovementioned kinetic data.

On a utilisé du chlorate de sodium comme oxydant pour le lessivage de la chalcopyrite dans une solution d’acide chlorhydrique. La concentration de l’acide chlorhydrique a un effet important sur la dissolution de la chalcopyrite. Les résultats indiquent que la vitesse d’agitation a un effet négligeable sur la dissolution du cuivre, suggérant que la réaction ne serait pas contrôlée par la diffusion en phase liquide. Le lessivage de la chalcopyrite est également affecté par la température. Des études de diffraction des rayons X ont montré que le sulfure était oxydé en sulfate à des températures égales à ou à moins de 65°C, et à 85°C, il était oxydé en soufre élémentaire lors du procédé de lessivage. Les études de l’effet de la température sur la dissolution indiquent que le procédé de lessivage est hautement dépendant de la température dans la gamme de 25 à 65°C. Ce résultat est compatible avec les valeurs de l’énergie d’activation à 25–45°C (60·0 kJ mol^?1) et à 45–65°C (57·7 kJ mol^?1). Dans ces gammes de température, le procédé de lessivage est contrôlé par une réaction chimique. Cependant, à des températures de 65 à 85°C l’énergie d’activation au début (0–180 min) est de 28·17 kJ mol^?1, ce qui suggère que la réaction est contrôlée par diffusion et chimiquement lors de cette étape. Lors de la dernière étape (180–300 min) du procédé à 65–85°C, l’énergie d’activation est seulement de 0·55 kJ mol^?1. À ce point, il semble que la diffusion domine. Les résultats de microscopie électronique à balayage et de spectroscopie à dispersion d’énergie sont compatibles avec les données cinétiques mentionnées ci-haut.     

Kinetics of leaching of zinc ferrite in aqueous hydrochloric acid solutions

The dissolution of synthetic samples of zinc ferrite in aqueous hydrochloric acid is stoichiometric. The rate appears to be controlled by a chemical reaction on the solid surface, and dependence of the dissolution rate on hydrochloric acid activity is of the first order. Activation energy of 83 kJ mol^-1 was found. Zinc ferrite leaching is a slow solubilization process in the hydrochloric acid treatment of dead-roasted Iberian pyrite ashes. The most favorable conditions are 0.5-1 M HC1 at 90 to 100 ‡C, when preferential solubilization of the spinel phases takes place on the hematitic matrix. Extensive extraction of zinc (~90 pct of total zinc) in one to two hours and low solubilization of iron (~8 pet of total iron) results under these conditions.     

氢还原重量法测定纯铑粉和铱粉的灼烧损失量

纯铑粉、铱粉产品中灼烧损失量的准确测定,是生产物料金属平衡考察和公正交易中的重要指标,以往常采用热重法对其灼烧损失量(挥发性物质含量)进行测定,但是该法分析成本较高、周期较长。根据挥发物于高温氢还原易除去的原理,实验提出了采用氢还原重量法测定纯铑、铱粉产品中灼烧损失量的方法。确定的实验条件如下:样品量为1.0~2.0g;采用分段升温方式进行氢还原,其程序为先从室温升温至200℃,恒温30min后升温至400℃,接着恒温30min后升温至600℃,再接着恒温30min后升温至800℃,最后再恒温120min;将盛有氢还原后铑粉、铱粉的石英舟置于干燥器中冷却30min,恒重1次。进一步试验表明:在氢气或氮气存在下冷却对分析结果的影响可忽略不计;样品中可能含有的炭含量对测定的影响可忽略不计;铑粉、铱粉样品中的挥发物主要由氧、氮构成。实验方法适用于纯铑粉、铱粉产品中不挥发杂质金属元素总质量分数不大于0.010%灼烧损失量的测定。将实验方法用于铑粉和铱粉管理样品、以及铑粉和铱粉实际样品中0.0042%~0.45%的灼烧损失量的测定,测定值与参考值或热重法测得值基本一致,相对标准偏差(n=11)不大于5.6%。     

Kinetics of reduction of nickel chloride with hydrogen

The kinetics of reduction of nickel chloride with hydrogen were investigated in the temperature range of 533 (260 °) to 788 K (515 °). Most experiments were done with porous NiCl2 granules having ?8+10 mesh (Tyler) size. The effects of temperature, sample size, granule size and hydrogen partial pressure on the reduction kinetics were investigated. In the temperature range 533 (260 °) to 651 K (378 °) the reduction is dominated by chemical kinetic factors. At higher temperatures diffusional effects appear to become quite significant. The temperature-dependence of the chemical kinetic rate constantK is given by $$\log K = 6.744 - \frac{{22,240}}{{2.303RT}};K\,\,is\,\,in\,\,\min ^{ - 1} $$ The activation energy for the reduction was found to be 22,240 cal /mol (or 93,050 J/mol) in the chemical kinetic regime.     

Separation of tungsten and molybdenum in dilute hydrochloric acid solution by extraction with sulfoxides

By using di-n-butylsulfoxide and petroleum sulfoxide as extractants, the extraction behavior of tungsten and molybdenum in hydrochloric acid solutions was studied under different acidities. When acidity is low, molybdenum is preferentially extracted, the selectivity can be very high, and the separation of these two metals is considered favorable. The separation was confirmed by dissolving in dilute hydrochloric acid the combined oxides of both metals, which were obtained from the acid leaching liquor of scheelite. From the experimental curves the molecular ratios of the complexing reaction were analyzed and the neutral molecular complex mechanism was discussed.     

Kinetics and mechanism of the reduction of molten nickel sulfide by hydrogen

The kinetics and mechanism of the reduction of M₃S₂ by hydrogen have been investigated between 1133° and 1300°C. When high flow rates of hydrogen and argon or helium bubbling through the melt are maintained the rate-determining step is a chemical process which can be expressed by a rate law of the form $$\begin{gathered} r_{H_2 S} = k_{expt} (N_S - \alpha )^2 p_{H_2 }^{1/2} \hfill \\ p_{H_2 } \geqslant 0.88atm \hfill \\ \end{gathered} $$ where k_expt = 85.1 atm^-1/2 min^-1, α = 0.17 at 1250°C. The experimental activation energy for this process is 20.1 ±3.0 kcal per mole. These results are discussed in terms of possible catalysis by nickel.     

多孔TiAI金属间化合物的抗热盐酸腐蚀性能

以Ti、Al元素粉末为原料，用粉末冶金法制备朋含量为35纵质量分数）的多孔TiAI金属间化合物．通过腐蚀动力学曲线、孔结构参数与表面形貌变化来研究在90℃恒温条件下，多孔TiAl在pH为2和3的盐酸溶液中的耐腐蚀性能，并对多孔TiAI与多孔钛、多孔镍以及多孔不锈钢在pH=2时的耐腐蚀性能进行比较。结果表明，当pH值由3减小到2时，多孔TiAI的耐腐蚀性能略有下降，但仍明显优于其他3种多孔材料。分析认为，多孔TiAI的优良耐蚀性能主要归因于钛铝金属间化合物特殊的键合特征以及Ti、AI元素的强钝化能力。     

多孔TiAl金属间化合物的抗热盐酸腐蚀性能

以Ti、Al元素粉末为原料,用粉末冶金法制备Al含量为35%(质量分数)的多孔TiAl金属间化合物.通过腐蚀动力学曲线、孔结构参数与表面形貌变化来研究在90 ℃恒温条件下,多孔TiAl在pH为2和3的盐酸溶液中的耐腐蚀性能,并对多孔TiAl与多孔钛、多孔镍以及多孔不锈钢在pH=2时的耐腐蚀性能进行比较.结果表明,当pH值由3减小到2时,多孔TiAl的耐腐蚀性能略有下降,但仍明显优于其他3种多孔材料.分析认为,多孔TiAl的优良耐蚀性能主要归因于钛铝金属间化合物特殊的键合特征以及Ti、Al元素的强钝化能力.     

Kinetics of the low-temperature hydrogen reduction of single-crystal magnetite

The hydrogen reduction of plates made from synthetic magnetite single crystals is studied in the temperature range 400–570°C. A mathematical model is developed and applied to describe the kinetics of gaseous reduction of plane finite objects. The following time contributions of individual process stages are distinguished with the least squares method and numerical integration: the nucleation of an iron phase, a chemical interaction of magnetite with hydrogen, and external and internal mass transfer. The diffusion and kinetic reduction parameters are calculated. The activation energy of the chemical stage (87.5 kJ/mol) is determined. An equation for the rate constant of the interaction of magnetite with hydrogen is proposed for temperatures below 570°C. A significant effect of the processes of consolidation and sintering of reduced iron on the internal diffusion parameters is detected in the low-temperature range.     

Kinetics of the low-temperature hydrogen reduction of magnetite concentrates

The hydrogen reduction of natural magnetite concentrates is studied by thermogravimetry in the temperature range 300–570°C. An improved equation of additive retardation time contributions is used to analyze experimental data on the gas reduction rate of powder oxides. A software package is developed to calculate the time contributions of the stages of gas reduction of concentrates and their fractions. The calculated data adequately describe the experimental kinetic curves of the hydrogen reduction of magnetite powders and pellets. It is shown that the derived equations and the developed software package can be used to study the low-temperature hydrogen reduction kinetics of oxides and natural magnetites and to estimate the corresponding technological schemes without using experimental investigations. Calculated curves are presented for the hydrogen reduction of nanosize magnetites.     

Kinetics of silver leaching from manganese-silver associated ores in sulfuric acid solution in the presence of hydrogen peroxide

Kinetics of silver leaching from a manganese-silver associated ore in sulfuric acid solution in the presence of H₂O₂ has been investigated in this article. It is found that sulfuric acid and hydrogen peroxide have significant effects on the leaching rate of silver. The reaction orders of H₂SO₄ and H₂O₂ were determined as 0.80 and 0.68, respectively. It is found that the effects of temperature on the leaching rate are not marked, the apparent activation energy is attained to be 8.05 kJ/mol within the temperature range of 30 °C to 60 °C in the presence of H₂O₂. Silver leaching is found to be diffusion-controlled and follows the kinetic model: 1−2x/3−(1−x)^2/3=Kt. It is also found that particle size presents a clear effect on silver leaching rate, and the rate constant (k) is proportional to d ₋₂ ⁰ .     

Extraction of gold(III) in hydrochloric acid solution using monoamide compounds

The extraction and separation properties of Au(III) using two monoamide compounds, N,N-di-n-octylacetamide (DOAA) and N,N-di-n-octyllauramide (DOLA), which have different side chain lengths attached to the carbonyl carbon (CH₃ for DOAA and n-C₁₁H₂₃ for DOLA), were investigated. The solvent extraction of some precious and base metals (Au(III), Pd(II), Pt(IV), Rh(III), Fe(III), Cu(II), Ni(II) and Zn(II)) in HCl solutions was carried out using DOAA and DOLA diluted with n-dodecane and 2-ethylhexanol. A good selectivity for Au(III) extraction with 0.5 M extractant is obtained at lower HCl concentrations (< 3.0 M) in both systems. The extractability of Au(III) with DOAA is greater than that with DOLA. In the 0.5 M DOAA–3.0 M HCl system, a third phase is formed when the Au(III) concentration in the initial aqueous phase is over 39 g/L. In contrast, third phase formation is not found in the 0.5 M DOLA–3.0 M HCl system, and its loading capacity of Au(III) is about 79 g/L. The Au(III) extracted in the organic phase is effectively back-extracted by 1.0 M thiourea in 1.0 M HCl solution in both systems, while some thiourea is precipitated using the organic phase containing 20 g/L of Au(III). The back extraction of Au(III) using water is poor in the DOAA system, but possible in the DOLA system.     

A contribution to the technology of vanadium recovery from solution by hydrogen reduction

Abstract

The hydrogen reduction of 5-valent Vanadium compounds from aqueous solutions investigated; The reduction precipitates a complex vanadium oxide with the composition mV₂O₃·nV₂O₅·pNa₂O·qH₂O.

The coefficients of components constituting the complex oxide may vary to some extent, but at a reduction temperature below 180°C and with an alkali concentration in the feed solution of less than 50 g/l, constitution of the oxide is V₂O₃·V₂O₅·1.5Na₂O·2H₂O.

The precipitated complex oxide acts as a catalyst in the reaction and the specific activity of the catalyst was 2.1·10^?4 g V/1/h/atm^1/2/m². Equations for the chemical reaction and the reaction rate are given and a basic flowsheet for a recommended process for vanadium recovery from solution by hydrogen reduction using the complex oxide as catalyst is discussed.

Résumé

La réduction en solution aqueuse de composés de vanadium V par l'hydrogéne a été étudiée. Il en résulte la precipitation d'un complexe d'oxyde de vanadium de composition mV₂O₃·nV₂O₅·pNa₂O·qH₂O.

La valeur des coefficients des composants du complexe peut varier dans une certaine mesure, mais quand la réduction a lieu à températures inférieures à 180°C, et pour des concentrations alcalines dans la solution mère infèrieures à 50 g/l, la composition de l'oxyde est de V₂O₃·V₂O₅·1.5Na₂O·2H₂O.

L'acide complexe précipité agit comme catalyseur de la réaction, et l'activité specifique du catalyseur était de 2.1·10^?4 g V/1/h/atm^1/2/m².

Les équations pour la réaction chimique et la vitesse de réaction sont donnees. On discute du diagramme de fonctionnement d'un procédé recommandé pour récupérer le vanadium de la solution par la reduction d'hydrogène et en employant l'oxyde complexe comme catalyseur.