Investigations on processing low-grade molybdenum concentrate by the nitric-acid method

Investigations on processing the low-grade molybdenite concentrate of the Bugdainskoe deposit by the nitric-acid method are carried out. The leaching modes (S: L ratio, reagent concentration, process duration, and temperature) are optimized. In optimal modes, the recovery of molybdenum from the starting concentrate into the solution exceeds 95%. The penetrating recovery from the ore into the commercial product is at a level of 85–86%. Investigating the process kinetics showed that the decomposition of the concentrate by nitric acid proceeds in the initial point in time in the kinetic mode. The addition of sulfuric acid into the nitric acid solution accelerates the process.     

Single-stage production of the nickel concentrate with processing of the rhenium-containing refractory alloy

The results of electrochemical processing of the ZhS32-VI refractory alloy in nitric acid solutions are discussed. The main production idea involves the performance of an electrochemical process under the controlled value of the anodic potential. This procedure provides the preferential transfer of nickel, which is the alloy base, into the solution and the formation of the cathodic product or metallic nickel with a purity no lower than 95%. Experiments on the electrochemical dissolution of the mentioned alloy at various values of the anodic potential are performed. It is determined that the cathodic product contains at E _a = 1.05 V, %: Ni 94.9, Re 0.2, Co 4.7, and Cr 0.1. It is established that the incorporation of the chloride ion (20 g/L) into the nitric acid electrolyte exerts no substantial effect on process characteristics; notably, the amount of nickel in the anodic slime decreases from 2.4 to 1.6%, and no considerable increase in the nickel content in the cathodic product takes place. The exclusion is a considerable increase in the transfer rate of rhenium into the electrolyte; notably, the rhenium concentration in the nitric acid electrolyte after the 10-h production process is 1.26 g/L, and that in the nitric acid electrolyte with the addition of the chloride ion is 8.90 g/L. It is shown that the process performance of the electrochemical dissolution of Re-containing nickel-based refractory alloys under the controlled anodic potential E _a = 1.05 V in nitric acid electrolytes provides the formation of a nickel concentrate with a purity no lower than 95% in one stage and makes it possible to concentrate rhenium in the anodic slime.     

Extraction of selenium from copper anode slimes in a sealed leaching system

A new method was proposed for extracting selenium from copper anode slimes with a low concentration of nitric acid in a sealed sulfuric acid leaching system. It is performed under an atmosphere of oxygen which allowed for a cyclic utilization of nitric acid. The effects of main parameters on selenium leaching were studied. The mineralogical characterizations of the typical samples were investigated by XRD and SEM. The results showed that the optimal conditions of the process are considered to be total gas pressure of 0.1 MPa, leaching temperature of 388 K, solid-liquid ratio of 0.20 g mL^–1, H₂SO₄ concentration of 2 mol L^–1, HNO₃ concentration of 0.07 mol L^–1 and leaching time of 2 h. The high selenium leaching efficiency of 99.23% was obtained under these conditions. According to the results of XRD and SEM-EDS, Cu–Ag selenide in the raw anode slimes is difficult to be leached with sulfuric acid alone; copper can be leached more easily from Cu-Ag selenide than silver; selenide is oxidized into the solution, undergoing the intermediate product of elemental selenium.     

Kinetics of galena dissolution in nitric acid solutions with hydrogen peroxide

The extraction of lead from a galena concentrate in nitric acid solutions with additional hydrogen peroxide was studied taking stirring speed, temperature, hydrogen peroxide and nitric acid concentrations, and particle size as dissolution parameters. The dissolution curves followed the surface chemical reaction controlled shrinking core model over the whole range of parameters, except at high nitric acid concentrations where the reaction was diffusion-controlled. The activation energy of 42 kJ mol^− 1 and a linear relationship between rate and inverse particle size support the reaction controlled dissolution mechanism. Hydrogen peroxide addition accelerated the reaction compared with nitric acid alone. It was concluded that the dissolution process is favourable, since the acid consumed for oxidation of galena can easily be regenerated in the same reactor by means of hydrogen peroxide.     

Extraction of fission palladium by Aliquat 336 and electrochemical studies on direct recovery from ionic liquid phase

The wide electrochemical window and ion exchange properties of a room-temperature ionic liquid (RTIL) have been exploited for the extraction of palladium from nitric acid medium into ionic liquid phase — followed by direct electrodeposition of the metal from the organic phase. Extraction of palladium by commercial Aliquat 336 ionic liquids, tri-n-octylmethylammonium chloride (TOMAC) and tri-n-octylmethylammonium nitrate (TOMAN), was studied as a function of [HNO₃], [NO₃⁻] and [TOMAN]. The distribution ratio (D_Pd(II)) of palladium in TOMAN increased with an increase in the concentration of nitric acid and passed through a maximum at 1.0 M nitric acid. In contrast, the D_Pd(II) value of palladium in TOMAC decreased continuously with an increase in the concentration of nitric acid. Substantial amounts of water and nitric acid were also co-extracted into the organic phase with palladium.     

Adsorption of Ce（ Ⅳ ） Anionic Nitrato Complexes onto Anion Exchangers and Its Application for Ce （Ⅳ） Separation from Rare Earths （ Ⅲ ）

Ceriumis one of the cheapest[1]and most abun-dant rare earths (RE) .However ,high purityis usual-ly required for its utilization in industry , where it isusedfor sulfur control insteels ,pyrophoric alloys ,ce-ramic ,catalyst support ,polishing powders ,etc .In its minerals ,as well as in the spent nuclearfuel ,ceriumis accompanied by other RE.They basi-cally exist in solution as stable RE(Ⅲ) species ,which makes their mutual separation rather difficult .In contrast to other RE, Ce(Ⅲ) can…     

Variants of processing molybdenite concentrates involving the use of preliminary mechanical activation

A review of possible ways to process molybdenite concentrates of various grades by both pyrometallurgical and hydrometallurgical methods is given and the most rational are noted. Prospects for processing low-grade molybdenum raw materials by nitric acid autoclave-less leaching with the complete transfer of molybdenum into the solution in the composition of sulfate complexes is shown. The variant that intensifies the nitric acid leaching of low-grade (6–17% Mo) concentrates obtained by the flotation of ores of the Bugdainskoe deposit via their preliminary dry mechanical activation is suggested.     

电感耦合等离子体原子发射光谱法测定Ti80钛合金中铝铌锆钼铁的酸体系溶解条件探讨

为实现Ti80钛合金样品的快速有效溶解,并制得适用于电感耦合等离子体原子发射光谱法(ICP-AES)测定Ti80钛合金中铝、铌、锆、钼、铁含量的样品溶液,对硫酸-硝酸、硝酸-氢氟酸、硫酸-氢氟酸-硝酸及盐酸-氢氟酸-硝酸4种酸体系对应的溶解条件进行了探讨。对4种溶解体系分别进行不同条件试验,根据溶解现象及样品溶解的完全程度初步确定了每种酸体系的溶解条件。硫酸-硝酸溶解体系的溶解条件为:10.0 mL硫酸(1+1),290~310 ℃下加热溶解,溶解完全后逐滴加入硝酸至溶液褪色;硝酸-氢氟酸溶解体系的溶解条件为:预先在样品中加入10.0 mL水,然后相继加入2.0 mL硝酸和2.0 mL氢氟酸,直至样品溶解完全;硫酸-氢氟酸-硝酸溶解体系的溶解条件为:预先在样品中加入10.0 mL硫酸(1+3),然后加入2.0 mL氢氟酸使样品溶解完全,加入2.0 mL硝酸至溶液褪色,再加热至冒烟;盐酸-氢氟酸-硝酸溶解体系的溶解条件为:预先在样品中加入15.0 mL盐酸(1+1),然后加入1.0 mL氢氟酸使样品溶解完全,加入2.0 mL硝酸使溶液褪色。在初步确定的溶解条件下,分别采用4种溶解体系对Ti80钛合金样品进行溶解,制得样品溶液;对样品溶液中铝、铌、锆、钼和铁的稳定性进行了考察并对其含量进行了测定,结果表明4种酸体系对应的溶解条件下制得的样品溶液均适用于电感耦合等离子体原子发射光谱法(ICP-AES)测定Ti80钛合金中铝、铌、锆、钼和铁含量,确定的4种酸体系对应溶解条件合理。     

Production of nickel–cobalt concentrate in rhenium-containing refractory alloy processing

The results of electrochemical processing of the ZhS32-VI refractory alloy implemented in a galvanostatic mode in the nitric acid electrolyte are described. Experiments on the electrochemical dissolution of the same alloy in the galvanostatic mode using a nitric acid solution with a concentration of 100 g/L at various current densities are carried out. It is shown that its constituent components separate quantitatively: refractory metals such as niobium, tantalum, molybdenum, and tungsten concentrate in the anodic slime, while partially cobalt and rhenium, as well as most of the aluminum, chromium, and nickel, transfer into the electrolyte. The functional process diagram for processing of the ZhS32-VI alloy is proposed, in which the formation and separation of the main mass of nickel and cobalt are performed at the first stage with the formation of the metallic Ni–Co-containing sediment.     

The extraction mechanism of thulium in di(2-ethyl hexyl) phosphoric acid-nitric acid system

Distribution ratios (D) and interfacial mass transfer coefficients in the case of extraction of thulium(III) with di(2-ethyl hexyl) phosphoric acid (HDEHP) in cyclohexane have been measured at different concentrations of nitric acid and HDEHP as well as at various stirring speeds of the two phases in a constant interface cell. From a study of the effect of stirring on the mass transfer coefficients it is observed that the overall extraction process is controlled by interfacial chemical reaction as well as by diffusion of interfacial chemical species across the interface. The latter is dependent on the rate of stirring. At stirring rates up to ～75 min^?1 the diffusional process is the rate determining step. On the other hand, when the stirring rate is ～400 min^?1, the diffusional step becomes very fast. At such high stirring speeds, the system belongs to a true kinetic regime, which was evaluated through computer simulation.     

Influence of Thermal Treatment on Copper Extraction from Electronic Wastes

The results of studying the influence of the preliminary thermal treatment of crushed electronic waste (EW) at a temperature of 450°C on the copper extraction degree during the subsequent leaching of materials by solutions of nitric acid are presented. The waste of the electronic industry, in particular, automobile microcircuits and computer printed circuit boards, is chosen as a research object. It is experimentally determined that the percentage of the organic phase in the composition of the research object varies within the range of 20–25% of the mass of the crushed raw material. The results of thermogravimetric analysis (TGA) and X-ray fluorescence analysis (XRF) show that the maximum degree of organic removal and formation of oxide forms of metals are observed in the temperature range 400–450oC. A mathematical model of the copper leaching process from EW with nitric acid solutions is obtained. The optimum parameters for the process are found: the temperature in the system is 75°C, the duration of leaching is 150 min, and the concentration of acid is 4 M with the maximum copper extraction to the solution being 98%. A comparative analysis of leaching processes of two types of materials (after thermal treatment and without thermal treatment) was carried out. It is experimentally confirmed that, for materials after preliminary thermal treatment, more completed copper leaching from EW with nitric acid solutions of lower concentration is provided when compared to the leaching of raw materials without thermal treatment. It is proved that, due to the preliminary thermal treatment of the materials, phase changes occur in the composition of the research object, namely, the transition of metals to their oxide forms, which positively affects the degree of copper extraction from EW at the subsequent nitric acid leaching.     

Carrier-mediated transport of uranium from phosphoric acid medium across TOPO/n-dodecane-supported liquid membrane

Present studies deals with the application of supported liquid membrane (SLM) technique for the separation of uranium (VI) from phosphoric acid medium. Tri-n-octyl phosphine oxide (TOPO)/n-dodecane is used as a carrier and ammonium carbonate as a receiving phase for the separation of uranium (VI) from the phosphoric acid medium. Throughout the study PTFE membranes are used as a support. The studies involve the investigation of process controlling parameters like feed acidity of phosphoric acid, carrier concentration and stripping agents. The effect of nitric acid and sodium nitrate in feed is also studied. It is found that there is negligible transport of uranium (VI) from pure phosphoric acid medium but it increases to very significant amount if 2 M nitric acid is added to feed phase. More than 90% uranium (VI) is recovered in 360 min using 0.5 M TOPO/n-dodecane as carrier and 1.89 M ammonium carbonate as stripping phase from the mixture of 0.001 M H₃PO₄ and 2 M of HNO₃ as a feed. The flux and permeability coefficient are found to be 9.21 × 10^− 6 mol/m² s and 18.26 × 10^− 5 m/s, respectively. Lower concentration of phosphoric acid with 2 M HNO₃ and higher concentration of carrier is found to be the most suitable condition for maximum transport of uranium (VI) from its low-level sources like commercial phosphoric acid.     

Electrochemical and surface studies on zircaloy-4 exposed to concentrated nitric acid medium

Zircaloy-4 has been considered as a candidate material for dissolver and evaporators in nuclear fuel reprocessing plants involving nitric acid of high concentrations at high temperatures. The present work deals with the electrochemical studies and surface analysis of passive films on zircaloy-4 and its welds in 11.5 M nitric acid medium. Potentiodynamic polarization technique was employed to study the corrosion behaviour of the alloy in both base and welded (Manual TIG and electron beam (EB) welding) conditions. The polarization curves for zircaloy-4 and its welds exhibited a distinct breakdown of passivity at 1.5 V (SCE) and repassivation, after showing a region of stable passivation. The characterization of passive films by SEM, XRD and LRS, grown at different potentials in 11.5 M nitric acid are presented. The surface morphology and phase analysis of passive films grown at higher potentials showed the presence of monoclinic ZrO₂. The phases present in the passive film grown electrochemically in 11.5 M nitric acid at 2.0 V and by autoclaving are found to be similar. The presence of characteristic 1040 cm⁻¹ Raman peak from the sample passivated at 1.2 V indicate that the oxide present consist of nanometer size grains of monoclinic zirconia.     

Production of high purity cobalt oxalate from spent ammonia cracker catalyst

A process was developed to produce > 99.9% pure cobalt oxalate from spent ammonia cracker catalyst pellets containing ∼ 20% Co generated at heavy water plants. A pilot plant for producing kilograms of cobalt oxalate of required purity has been set up. The process consists of leaching, oxidation, solvent extraction, ion exchange and oxalate precipitation. The major impurities present in the leach liquor after nitric acid oxidation were Fe³⁺, Al³⁺ and Ni²⁺. Fe³⁺ and Al³⁺ were separated from the leach liquor by using a solvent extraction (SX) process employing a mixed extractant system consisting of D2EHPA and TBP. Ni²⁺ was separated by ion exchange (IX) employing Dowex M4195 resin.     

Resistance of materials based on silicon nitride to corrosion by solutions of some acids and alkalis

Conclusions Hot-pressed silicon nitride parts of 1.5–4% porosity containing a 10 wt. % activating addition of MgO are resistant to corrosion by nitric acid at room temperature and by 1% NaOH solution at 100°C under steady-state conditions. The presence of 1–20 wt. % CaF₂ added with the aim of improving antifriction properties results in corrosion in nitric acid, obeying the law m²=K, where K 5.5·10^–5· C³ %²/h). The corrosion is due to attack on specimens by hydrofluoric acid forming during the reaction between the CaF₂ and HNO₃.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 70–72, January, 1980.     

Acid dissolution of cupric oxide

The rates of dissolution of synthetic cupric oxide in solutions containing perchloric, sulfuric, nitric or hydrochloric acid were studied using sintered disks. In each case, the dissolution rate increased with elapsed retention time until an essentially constant value was reached. This phenomenon can be attributed to an increase in the disk’s effective surface area. The dissolution rate is of the first order with respect to a_H ⁺ for perchloric, nitric, and hydrochloric acids, while it is of a half order for sulfuric acid. High activation energies, ranging from 12.4 to 20.5 kcal/mol, and the independence of agitation speed on cupric oxide dissolution reaction rate suggest that chemical reactions are the major determinants of dissolution rates. The addition of electrolytes having anions common with the acids resulted in an acceleration of the dissolution rate due to increases in a_H ⁺ values. However, the addition of electrolytes of noncommon anions revealed a quite different effect on dissolution rate. This suggests that the adsorption and/ or complexing of anions on the cupric oxide surface may have had a significant role in the determination of the dissolution rates. The type of acid used determined the identity of the adsorbed anion.     

Recovery of yttrium from deep-sea mud

Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H~+concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4:1 and room temperature 25 ℃(only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 ℃). Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204,15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y~(3+) and 42.60% Fe~(3+) are extracted from sulfuric acid leaching liquor(adjusted to pH = 2.0) after seven-stage counter current extraction with O/A ratio of 1:1 at room temperature, while other metals ions such as Al~(3+), Ca~(2+), Mg~(2+)and Mn~(2+) are almost not extracted. The Y~(3+) in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with O/A ratio of 10:1 at room temperature, while only 2.26% co-extracted Fe~(3+) is stripped. The Y~(3+) of loaded strip liquor can be precipitated by oxalic acid to further separate Y~(3+) and Fe~(3+). The precipitation efficiency of Y~(3+) in loaded strip liquor can be 98.56% while Fe~(3+) is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 ℃ for 3 h to obtain the oxide of Y in which the purity of Y_2 O_3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%.Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting,the yttrium yield is 82.04%.     

Uranium and Rare Earth Recovery from Phosphate Fertilizer Industry by Solvent Extraction

Abstract

The paper presents a comprehensive review of the fundamental and applied aspects of the recovery of uranium and rare earths from phosphoric acid used for fertiliser production, by solvent extraction, with emphasis on the data from the pilot plant operated in Romania. The occurrence of uranium and rare earths in various phosphatic deposits is described and variations discussed. The radioactivity of the phosphatic rock is shown to be a cause for concern for control over pollution. History of the commercial recovery operations is decribed and the role of economic factor highlighted. The acidulation of phosphate rock, behavior of uranium and rare earths, influence of iron and effect of humic matter in the sulphuric acid process and the nitric acid process is discussed- Uranium extraction from the phosphoric acid by acidic organophosphorus esters is discussed in detail. The industrial flowsheets are described. Details are presented for the single cycle extraction process developed in Romania. Cost estimates are given which show the superiority of the single cycle process and its capability to produce uranium at a competitive price, while also producing rare earths as a by-product. Process flowsheet with stream data is also given for treatment of the solution obtained by nitric acid attack of the phosphate rock. Analysis of the uranium green cake (UF₄) and the rare earth concentrate is given.     

金精矿超声波强化硝酸预氧化工艺研究

对含硫较高的金精矿采用超声波强化硝酸氧化预处理工艺,处理后的氧化渣采用氰化浸出,金的浸出率同硝酸直接氧化后氰化浸出相比,有显著提高。该方法氧化时间短,对设备要求低。具有一定的生产应用价值。     

试剂级硝酸镍的制备及其改进措施

对试剂级硝酸镍制备原理进行了分析;在产品研制过程中,对硝酸的浓度对电解镍溶解时间、硝酸的利用率及pH值对产品质量影响进行了研究;通过试验,确定了试剂级硝酸镍的制备工艺和关键技术参数：硝酸的浓度控制在13-14mol／L范围内,有利于电解镍溶解;当硝酸的浓度为13．5mol／L时,硝酸有效利用率达到95％;当溶液的pH值达到3．5后,可得到满足Q／YLB-2005-09标准要求的产品。找出了试剂级硝酸镍生产中存在的主要问题,并提出了有效改进措施：通过改进加酸方式、综合利用反应热、提高硝酸的利用率,从而达到降低生产成本和改善操作环境的目的。