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  • The effects of SeO2 additive on Mn electrodeposition on Al substrate in MnSO4-(NH4)2SO4-H2O solution
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-25
    Fan Yang; Liangxing Jiang; Xiaoying Yu; Yanqing Lai; Jie Li
    更新日期:2020-01-26
  • Co-volatilizing-water leaching process for efficient utilization of rhenium-bearing molybdenite concentrate
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-23
    Hu Sun; Junjie Yu; Guanghui Li; Dapeng Shi; Jun Luo; Mingjun Rao; Zhiwei Peng; Tao Jiang

    Rhenium-bearing molybdenite concentrate is a typical mineral resource to recover molybdenum and rhenium, but has long been poorly utilized via oxidative roasting-leaching route. In this work, a novel flowsheet consisting of chloride leaching, co-volatilization, selective condensation, and water leaching has been proposed and verified on the basis of both experimental and thermodynamic studies. Purification treatment was first performed using a solution of HCl and CaCl2, which increased the grades of Mo and Re from 43.6 wt% and 321 mg/kg to 51.3 wt% and 374 mg/kg, respectively, after leaching at 95 °C for 30 min. The purified concentrate was then roasted with air supply after being pelletized with the addition of SiO2 and Al2O3, which served as skeleton materials to prevent pellets from being broken. The results showed that over 99.9% of rhenium and 90.4% of Mo could be co-volatilized within 30 min when temperature was 1050 °C. The volatile material condensed above 500 °C was assayed to be highly pure MoO3 (99.9%) with almost no rhenium, while the volatile material collected at lower temperature was concentrated with high-content Re2O7. Furthermore, through water leaching at 25 °C for 30 min with liquid to solid ratio of 5 mL/g, 98.6% of Re was easily leached out from volatiles.

    更新日期:2020-01-23
  • Bioleaching of gold from waste printed circuit boards by alkali-tolerant Pseudomonas fluorescens
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-23
    Jingying Li; Jiangxian Wen; Yang Guo; Ni An; Changjin Liang; Zhongying Ge

    This paper evaluated the ability of Pseudomonas fluorescens to leach gold from waste printed circuit boards (WPCBs). Gold was recovered as gold-cyanide complex and cyanide was produced by Pseudomonas fluorescens. In this paper, the effect of pH on gold leaching efficiency was studied, the P.fluorescens was domesticated to grow at higher pH (pH 8 and 9), and the concentration of cyanide ions (CN−) available for bioleaching was increased in alkaline pH. The results showed that at 0.67% w/v pulp density of pretreated waste printed circuit boards powder, mutated bacteria attained gold biorecovery of 27% at pH 9, while the unadapted bacteria only 23% of bioleaching efficiency was achieved. Results revealed that bioleaching efficiency of gold from waste printed circuit boards decreased with the increase of pulp density, and 0.33% w/v pulp density had the maxnium influence to bioleaching efficiency of gold, which could reach 42%. In the two-step bioleaching process, the initial amounts of bacteria had a certain impact on the leaching efficiency, and 3.33% v/v of the initial bacterial liquid was a suitable addition. The type of substrate also affected the leaching bioleaching efficiency. The leaching efficiency in the later stage of gold leaching will be greatly improved to 54%, when glycine and methionine were added to the medium for cyanide production. This may be due to positive effect by the methionine, which could regulate the glycine pool of the cells.

    更新日期:2020-01-23
  • Analysis of iron and copper speciation and activities in chloride leaching solutions of high ionic strength
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-22
    Mohsen Hashemzadeh; Wenying Liu

    In light of the recent increased use of seawater for copper heap leaching, we analyzed the speciation and activities of iron and copper in chloride media, with a focus on chalcocite leaching. Compared with other published work, the present study carried out such analysis at high solution ionic strength up to 3 M. For this purpose, the SIT (Specific ion Interaction Theory) activity model was used in the thermodynamic calculations performed by the STABCAL software. The speciation results obtained from the software were validated by the experimental measurements of solution potential, which were performed in a sealed jacketed reactor under an ultra-high purity nitrogen environment. The speciation results showed that FeCl2+ and hydrated Fe2+ were the dominant Fe(III) and Fe(II) species in the chloride concentration range 0.5 M – 3 M. In the case of copper speciation, hydrated Cu2+ and CuCl2− dominated at chloride concentrations <0.5 M. In the chloride concentration range 0.5 M – 3 M, CuCl+ and CuCl32− were the dominant copper species. Based on the speciation and activities results, we determined the actual cathodic and anodic half reactions responsible for copper leaching from chalcocite in chloride media. The proposed cathodic half reactions pinpoint ways of manipulating solution potentials, which is vital for determining the kinetics of the second stage of chalcocite leaching.

    更新日期:2020-01-22
  • Electrochemical leaching of rare-earth elements from spent NdFeB magnets
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-22
    Irina Makarova; Ekaterina Soboleva; Maria Osipenko; Irina Kurilo; Markku Laatikainen; Eveliina Repo
    更新日期:2020-01-22
  • Removal of Fe(III) from Ni-Co-Fe chloride solutions using solvent extraction with TBP
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-22
    Xintao Yi; Guangsheng Huo; Wei Tang

    The extraction of Fe(III), Ni(II) and Co(II) from a Ni(II)-Co(II) solution containing Fe(III) was analyzed in a chloride medium using a mixed extractant consisting of 50% (v/v) tributyl phosphate (TBP), 20% (v/v) 2-octanol and 30% (v/v) kerosene. The extraction of 0.5 mol/L Fe(III) in 4 mol/L hydrochloric acid reached 97%, and the consumption of chloride ions was investigated. Nickel(II) ions were not detectably extracted by TBP, with an inclusion of <1.1%. Compared with Fe(III), TBP extracted only a small amount of Co(II). The iron complexes formed by TBP and 2-octanol were [H2FeCl4 · 2TBP] and [H2FeCl4 · 5(2-octanol)], and the possible compositions of Co-containing extracts were [H2CoCl4 · 2TBP] and [H2CoCl4] · n[2-octanol]. An industrial process consisting of two-step extraction was designed to achieve the separation of Co(II) and Fe(III), resulting in a decrease in the Fe/Co mass ratio from 0.46 to <3.5 × 10−4 in the raffinate.

    更新日期:2020-01-22
  • Microwave digestion of gibbsite and bauxite in sodium hydroxide
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-21
    Ben Dillinger; Andrew Batchelor; Juliano Katrib; Chris Dodds; Carlos Suchicital; Sam Kingman; David Clark

    It was hypothesized that bauxite digestion may be improved by using microwave heating as it has been shown in literature that some material processes have improved efficiency. To test this hypothesis, a set of digestion experiments were conducted using gibbsite, one of the major minerals in bauxite. Gibbsite was digested at various temperatures (50, 75, and 95 °C) in either 1 M or 6 M sodium hydroxide solutions for 30 min using either a convection oven or a 2.45 GHz microwave applicator. Results show that microwave heating provided an increase of 5–7% in the digestion after 30 min and required around 1/10th the time to heat the solutions compared to conventional heating. Electromagnetic simulations show that preferential heating occurs at the solution surface creating a temperature gradient within the solution. Although vigorous stirring of the solution was used to minimize the temperature gradient, it could still be responsible for the observed difference in digestion. Digestion of bauxite itself yielded similar results to the gibbsite.

    更新日期:2020-01-22
  • Improving the washing and desorption of tungsten-adsorbed weak base resin
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-20
    Xintao Yi; Guangsheng Huo; Haipeng Pu; Zhaoxi Zhang; Ping Chen; Jiaxun Liu

    The adsorption of tungsten by a macroporous weak base resin had been widely studied. However, due to the problem of the crystallization of ammonium paratungstate (APT) during the desorption process, there have been few detailed reports on subsequent steps after resin adsorption. The authors found that APT could be dissolved in ammonia in a closed container at 60 °C while achieving a high resin desorption rate, thus solving practical production problems. On this basis, the washing and desorption behavior of the high capacity ion exchange resin D314 was investigated. The lower sodium ion concentration after aeration washing indicated that the aeration washing could obtain a better washing result than the ordinary shaker shaking washing. The longer the washing time and the greater the number of washing times, the better the washing effect. Under the condition of a liquid-solid volume ratio of 1.25:1 and ammonia eluent of 150 g/L, the single desorption rate of saturated resin for 6 h could reach approximately 90% at 60 °C. A desorption rate of >99% could be achieved by multiple desorption. The industrial processes were designed to achieve the normal operation of resin desorption and the washing solution circulation. Backscattering SEM and EDS were applied to study the distributions of sodium and tungsten before and after the saturated resin treatment.

    更新日期:2020-01-21
  • Study of the leaching and pore evolution in large particles of a sulfide ore
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-18
    Rahul Ram; Luis Beiza; Megan Becker; Mark I. Pownceby; Miao Chen; Yi Yang; Sam Yang; Jochen Petersen
    更新日期:2020-01-21
  • Integration of resource recycling with de-alkalization for bauxite residue treatment
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-18
    Xuekai Zhang; Kanggen Zhou; Qingyuan Lei; Yan Xing; Changhong Peng; Wei Chen
    更新日期:2020-01-21
  • Recovery of vanadium from leach solutions of vanadium slag using solvent extraction with N235
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-16
    Zhifeng Qin; Guoquan Zhang; Yingjie Xiong; Dongmei Luo; Chun Li; Siyang Tang; Hairong Yue; Bin Liang

    Leach solutions of vanadium (V) slag was generated from (NH4)2SO4 (AS) roasting and water leaching process. After separating titanium (Ti) from the solutions, the remaining liquor contains a large amount of V and iron (Fe). In this study, a system composed of trioctyl tertiary amine (N235) and sulfonated kerosene was used to separate V; moreover, the feasibility, mechanism, and energy evaluation of this system were also investigated. The results indicated that the single-stage V extraction rate was 86.35% using 40% N235 (v/v) and 60% sulfonated kerosene, an initial pH of 1.23, an organic/aqueous phase ratio (O/A) of 1.5:1, a temperature of 298.15 K, and an extraction time of 1 min. Based on McCabe-Thiele analysis, over 99% of the V was extracted by three-stage countercurrent extraction. Using the slope method and Fourier transform infrared (FT-IR) spectroscopy, the V extracted by N235 was proposed to exist as [(R3NH)4·H2V10O28]. Using 1.4 mol/L ammonia water, over 90% of the V could be stripped. The effects of the impurities Si, Ca, Al, Mg, and Mn on V recovery were negligible. A preliminary material and energy calculation (MEC) indicated that 113.64 kg V2O5 could be recovered from 1000 kg raw V slag using 5.57 × 106 kJ of heat and 974.45 kWh of electricity.

    更新日期:2020-01-17
  • Morphology-control techniques for preparing aluminum hydroxide via wet chemical synthesis
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-16
    Weidong Fan; Wangxing Li

    Flake aluminum hydroxide was prepared via neutralization with ammonia and aluminum nitrate solutions containing alumina at a concentration of 10 g/L. Meanwhile 0.5 g/L acetic acid was added to the solution as a shaping additive. The morphology control of neutralization allowed for the production of columnar and flake submicron aluminum hydroxide via precipitation in the Bayer process, which is widely used in alumina refineries. Finally, three morphology-control techniques were developed as followed: (1) during the growing of the crystal seed, the reaction solution should be maximally stabilized. Increased stable condition duration resulted in improved aluminum hydroxide morphology; (2) aluminum hydroxide morphology changed when different anions and additives were used in the reaction solution; and (3) separation of the nucleation stage and growing-up stage afforded aluminum hydroxide with perfect morphology.

    更新日期:2020-01-17
  • Observation of sodium titanate and sodium aluminate silicate hydrate layers on diaspore particles in high-temperature Bayer digestion
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-16
    Yi-lin Wang; Xiao-bin Li; Qiu-sheng Zhou; Biao Wang; Tian-gui Qi; Gui-hua Liu; Zhi-hong Peng; Ke-chao Zhou

    During the high-temperature Bayer process, the inhibitory effect of titanium-containing minerals on diaspore digestion is believed to be resulted from the formation of a dense sodium titanate layer covering the diaspore particles, however, there is a lack of direct observational evidence to date. This work adopted X-ray photoelectron spectroscopy (XPS), cross-section SEM and in-situ analysis to clarify the inhibitory mechanism by investigating the interactions between Al-/Ti-/Si-bearing minerals in the simulated high-temperature Bayer digestion process. The observation of a sodium titanate layer provided direct evidence for the solid layer theory. XPS result further indicates that the Ti-O-Al bond is a significant factor in promoting the covering of sodium titanate on alumina-bearing mineral particles. Cross-section SEM and in-situ analyses illustrate that the dissolution of diaspore is carried out not only on the surface of diaspore particles but also on the inner surface such as pores and gaps of particles. Meanwhile, as similar to Ti-bearing minerals, the Si-bearing minerals also inhibit the diaspore digestion by forming a sodium aluminate silicate hydrate layer at an elevated temperature.

    更新日期:2020-01-17
  • Extraction of lithium from brines with high Mg/Li ratio by the crystallization-precipitation method
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-15
    Xianrong Lai; Pan Xiong; Hui Zhong

    A new crystallization-precipitation method is proposed to extract lithium from salt-lake brine with high Mg Li mass ratio (Mg Li > 40). A closed loop path for carnallite crystallization is established and a high magnesium removal efficiency is achieved via MgHPO4(S) precipitation through thermodynamic analysis and experiments. In the first stage, KCl is added into the brine to remove about 50% of magnesium by forming carnallite. When the amount of KCl is 55.9% of stoichiometric requirement and further evaporation at 17.6%, the removal efficiency of total magnesium is 53.1% and the loss of lithium is 5.4%. In the second stage, residual magnesium in the brine is further removed by forming MgHPO4(s). With the amount of Na2HPO4 at stoichiometric requirement, reaction temperature 40 °C, reaction time 30 mins and aging time 3 h, the removal efficiency of residual magnesium is 99.2% and the recovery of residual lithium is 98.5%. To sum up, the total removal efficiency of magnesium is 99.6% and the recovery of lithium is 93.2%. In addition, KCl and Na2HPO4 used in this method can be recycled, which will significantly reduce the cost.

    更新日期:2020-01-15
  • Enriching lithium and separating lithium to magnesium from sulfate type salt lake brine
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-10
    Xuheng Liu; Maoli Zhong; Xingyu Chen; Jiangtao Li; Lihua He; Zhongwei Zhao
    更新日期:2020-01-11
  • The response of sulfur chemical state to different leaching conditions in chloride leaching of chalcocite
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-09
    Mohsen Hashemzadeh; Wenying Liu

    Heap chloride leaching of low-grade copper sulfides with the use of seawater has been proposed as a feasible alternative to address challenges associated with water scarcity and depletion of oxides. Our previous study of leaching kinetics showed that the leaching reaction slowed down in the second stage and the maximum copper extraction achieved at ambient temperature was around 70–80%. To uncover the reasons for the slowed-down leaching, we investigated the evolution of solid surface properties during leaching, particularly morphology and sulfur chemical state, and the responses of mineral surface properties to different leaching conditions using SEM-EDX and XPS techniques. The results showed that sulfur sequentially transformed from monosulfide S2− to disulfide S22−, and then to polysulfide Sn2− and elemental sulfur S0. Less elemental sulfur was present on the solid particle surfaces at high solution potentials, the removal of which by CS2 washing did not improve copper extraction. In contrast, at low solution potentials, a slight increase in copper extraction was associated with sulfur removal from the solid surfaces. These results led to the conclusion that the slow decomposition of polysulfide formed during leaching was responsible for the slow reaction at high solution potentials, whereas at low solution potentials, a combination of polysulfide decomposition and diffusion barrier by elemental sulfur layer was the reason for the slow dissolution. The effect of chloride was concluded to be important only at low solution potentials where the level of elemental sulfur crystallinity was lower.

    更新日期:2020-01-09
  • Solvent extraction of An(III) and Ln(III) using TODGA in aromatic diluents to suppress third phase formation
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-08
    Patrik Weßling; Udo Müllich; Elise Guerinoni; Andreas Geist; Petra J. Panak

    The extraction of nitric acid, trivalent actinides and lanthanides with N,N,N′,N′-tetra-n-octyl-3-oxapentanediamide (TODGA) dissolved in the aromatic diluents 1,4-diisopropylbenezene and tert-butylbenzene was studied. Nitric acid extraction proceeds along the formation of 1:1 and 2:1 HNO3-TODGA adducts. An(III) and Ln(III) distribution ratios were determined as a function of nitric acid, TODGA and Ln(III) concentrations. Distribution ratios are approximately an order of magnitude lower in aromatic diluents compared to aliphatic diluents. No third phase formation was observed when contacting the solvent with an aqueous phase containing 1.5 mol/L Er(NO3)3 in 2–4.3 mol/L HNO3. Slope analysis indicates the formation of 1:3 and 1:4 M(III):TODGA complexes. Using TRLFS, the formation of a previously unknown 1:2 complex in organic phases loaded with Ln(III) was observed for the first time.

    更新日期:2020-01-09
  • Extraction of lithium from a montebrasite concentrate: Applied mineralogy, pyro- and hydrometallurgy
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-08
    Paulo F.A. Braga; Silvia C.A. França; Caroline C. Gonçalves; Paulo F.V. Ferraz; Reiner Neumann
    更新日期:2020-01-08
  • Effects of Ag+ in diaphragm electrolysis on oxygen evolution and corrosion behaviors of Pb and PbAg anodes
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-08
    Wenjun Wang; Ruidi Li; Tiechui Yuan; Xianyun Zhu; Haihua Li; Wenjun Lin; Lanbo Li

    In this study, the effects of Ag+ (140 mg/L) in an electrolyte on the oxygen evolution and corrosion behaviors of Pb and PbAg (0.6 wt%) anodes in diaphragm electrolysis were investigated by utilizing a variety of tests and analyses, including galvanostatic polarization, mass increment, ion concentration, anodic polarization curve, phase analysis, and scanning electron microscopy of the oxide layer and substrate. The results show that an ion exchange membrane can effectively prevent Ag+ and Pb2+ from penetrating into the cathode chamber and depositing on the cathode. The addition of Ag+ in diaphragm electrolysis significantly lowers the overpotential of oxygen evolution reaction and improves the corrosion resistance of Pb and PbAg (0.6 wt%) anodes. This is mainly attributed to the formation of Ag2O2 on the surface of the anode, which provides good catalytic activity for the oxygen evolution reaction (Ag2O2 can form Ag2O2 hydrate in sulfuric acid solution, Ag2O2 hydrate loses electrons and H+ during electrification, and then Ag2O2 is formed again after electron rearrangement).

    更新日期:2020-01-08
  • Potassium recovery from a Brazilian glauconitic siltstone via reaction with sulfuric acid in hydrothermal conditions
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-07
    R.S. Schimicoscki; K.D. Oliveira; C.N. Ávila Neto

    This work presents a study on the dissolution kinetics of a Brazilian glauconitic siltstone, known as Verdete, in the presence of sulfuric acid and in hydrothermal conditions. The objective was to verify the efficiency of the hydrothermal methodology in breaking up the structures of muscovite, glauconite and K-feldspar at low liquid/solid ratio to recover potassium. The water-soluble and insoluble products were analysed by flame photometry, XRD and SEM-EDS. The reaction rate of K extraction showed to be high, and K recovery was directly proportional to the acid concentration. K release occurred due to rupture of micas, and the reaction mechanism occurred through replacement of interlayer K+ with H+, and a partially extraction of Al3+, Fe3+, Fe2+ and Mg2+ from the 2:1 layer. With the breakup of silicate structures, the remaining solid product was amorphous silica. K-feldspar began to be dismantled at higher temperatures (> 473 K).

    更新日期:2020-01-07
  • Rare earths recovery by fractional precipitation from a sulfuric leach liquor obtained after phosphogypsum processing
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-07
    Amani Masmoudi-Soussi; Ines Hammas-Nasri; Karima Horchani-Naifer; Mokhtar Férid

    The present work describes a process to recover rare earth elements (REEs) by selective precipitation with ammonia from phosphogypsum (PG) waste, a by-product of the phosphate industry. A pretreatment step was carried out with a solution of sodium chloride and sodium carbonate (60 g/L) in order to assure, respectively, a better solubilization of impurities and a conversion of PG to a calcite matrix easily attacked in an acid medium. Enriching a sulfuric acid solution (15%) with REEs was performed by double contacting the same acid solution with appropriate amounts of the pretreated PG by maintaining the operating conditions (L/S = 3, 100 °C and 2 h) each time. The leaching method produced a sulfuric leach liquor rich with rare earths with a final concentration of 4308 mg/L as well as two anhydrite solids. The latter, having the same level of purity, could be used safely in many industrial applications. Afterward, the progressive addition of ammonia (10%) to the REEs-rich liquor led to form three precipitates at different pH values: 1.1; 2.3 and 6. The ICP/MS analysis of the precipitation liquors showed that the optimum pH for the precipitation of REEs is 1.1 allowing their recovery with an efficiency of 98.5%; while precipitations at higher pH of 2.3 and 6 had a lower recovery yield of respectively 42.4% and 39.3%. The X-ray diffraction analysis of the precipitate obtained at pH 1.1 showed that it corresponds to an ammonium sulfate compound. Analyzes with photoluminescence technique showed the characteristic luminescence bands of Ce3+, Gd3+, Dy3+, Pr3+ and Sm3+(after excitations at λExc = 260 nm and λExc = 440 nm) confirming the presence of REEs in the precipitate.

    更新日期:2020-01-07
  • Influence of chemical and phase composition in the hydrometallurgical processing of FeTi oxide phases
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-07
    Thomas Schirmer; Marcela Achimovičová; Daniel Goldmann

    The production of pure TiO2 gains a lot of interest because of its use in white pigment, ink and cosmetics as well as precursor for Ti metal generation. Although titanium oxide is commonly distributed in accessory minerals in hard rocks and sediments (rutile, anatase and brookite), ores with high amounts of TiO2-phases are not common. Important minable Ti ore often contains FeTi oxides like ilmenite or pseudorutile. A current processing route to produce high purity TiO2 out of these phases involves a hydrometallurgical step with high concentrated sulfuric acid that is applied at high temperatures to leach preconcentrated iron containing Ti-ore. To overcome this energy intense current technology a novel method, called TiMAG-process has been developed at IFAD over the last few years. This process uses nascent hydrogen generated by the reaction of a base metal like Al with diluted H2SO4 at moderate temperatures together with ilmenite concentrate in a specific milling and leaching process aiming a reduction of Ti4+ to Ti3+. Recent investigations reveal, that mineralogical and chemical properties of FeTi oxide concentrates can distinctively influence their leaching, changing the transfer rate of Ti into the liquid phase under identical process conditions between 50 and 80%. Two major facts have been identified and will be discussed in this paper based on tests with FeTi oxide samples from India and Mozambique revealing some different physico-chemical properties.

    更新日期:2020-01-07
  • A comparative study of the kinetics of the oxidation of iron(II) by oxygen in acidic media - mechanistic and practical implications
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-07
    Michael J. Nicol

    The results of this comparative study have shown that in 1 M acid solutions, the differences in reactivity of iron(II) for reduction of oxygen are within about an order of magnitude of each other for the systems studied at 40 °C. This applies to both the uncatalysed and copper(II) catalysed systems. The exception is the chloride system in which the rate can be significantly increased by increasing the chloride concentration. The other main conclusion is that although catalysis by copper(II) ions can be significant there exist conditions (iron(II) and (III) concentrations) for which the effect is not that important. Rate equations for both the uncatalysed and catalysed reactions have been derived that apply equally to all the systems studied. Values for the various rate constants have been obtained by analysis of extensive kinetic data in 1 M acid solutions at 40 °C. A limited electrochemical study has been used to derive values for the equilibrium constant for the reaction involving the iron(III)/iron(II) and copper(II)/copper(I) couples. An attempt has been made to compare relevant constants with previously published data and to derive a mechanism that is consistent with the kinetic results. This study has shown that the use of methanesulfonic acid as an oxidative leaching medium does not offer any advantages and is the least reactive of the systems studied.

    更新日期:2020-01-07
  • The influence of micro-cracks on copper extraction by bioleaching
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-27
    Jinghe Chen; Ding Tang; Shuiping Zhong; Wen Zhong; Baozhu Li

    Micro-cracks produced in the crushing stage could improve the permeability and diffusion of leaching solution within the ore particles, which would favor for the leaching process. However, its influence on the extraction of copper by bioleaching has rarely been studied. In this work, we reported the enhancement effect of micro-cracks on the bioleaching of low-grade copper sulphide ore. Jaw crusher and high-pressure grinding rolls were adopted to prepare ore samples of the same size fraction but with different number of micro-cracks in the ore particles. Statistical data, scanning electron microscope (SEM) and stereomicroscopy (SM) images clearly showed that high-pressure grinding rolls could generate more and larger micro-cracks than the same produced by jaw crusher. Subsamples from the −0.9 mm and 3–6 mm size fractions were utilized for shake flask and column bioleaching experiments, respectively. The earlier change in pH and higher oxidation-reduction potential (Eh) indicated that more micro-cracks were beneficial for the growth of bacteria, which then enhanced the bioleaching efficiency of copper. In the shake flask experiments, the copper extraction efficiency was increased from 87.4% to 94.3% on the 30th day at 40 °C and 150 rpm. Similarly, in the column experiment with the ore sample prepared by high-pressure grinding rolls, an approximately 12.2% improvement of bioleaching efficiency was observed as compared to the system with the ore sample prepared by jaw crusher. These results demonstrated that creating micro-cracks could be crucial for heap bioleaching of low-grade copper sulphide ores.

    更新日期:2019-12-27
  • Synergistic solvent extraction of heavy rare earths from chloride media using mixture of HEHHAP and Cyanex272
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-24
    Haiqin Wei; Yanling Li; Zhifeng Zhang; Wuping Liao

    The synergistic extraction of heavy rare earths from chloride medium was investigated using the mixture of heptylaminomethylphosphonic acid mono-(2-ethyl-hexyl) ester (HEHHAP, HA) and bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272, HB) in heptane. The extraction efficiency of heavy rare earths and the separation factors between adjacent lanthanides with the HEHHAP-Cyanex272 mixture are both better than those for the sole HEHHAP or Cyanex272 system. The separation factors between adjacent heavy rare earths are also higher than those for other synergistic systems. The rare earth extraction is a cation exchange process deduced by both slope analysis method and constant molar method. The extracted complexes are determined to be LnH2Cl2A2B (Ln = Yb, Lu). The loaded metal ions can be easily stripped by HCl or H2SO4. The stripping efficiency is over 90% when the concentration of HCl was more than 1 mol/L.The synergistic extraction of heavy rare earths with the mixed HEHHAP-Cyanex272 system is an endothermic reaction.The negative values of ΔG indicates that the extraction reaction of Ln(III) is spontaneous and favorable.

    更新日期:2019-12-25
  • Recovery of lithium from salt-lake brines using solvent extraction with TBP as extractant and FeCl3 as co-extraction agent
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-24
    Zhiyong Zhou; Jiahui Fan; Xueting Liu; Yafei Hu; Xiaoyu Wei; Yulei Hu; Wei Wang; Zhongqi Ren

    A novel extraction process to recover lithium ions from simulated salt lake brines with high Mg/Li ratio was developed. Tributyl phosphate (TBP), FeCl3 and diethyl succinate were used as extractant, co-extraction agent and diluent, respectively. Effects of extraction conditions containing the volume concentration of TBP, Fe/Li molar ratio and O/A phase ratio on extraction performances were studied. The highest one-stage extraction efficiency of lithium ions and separation factor were about 65% and 350, respectively. In addition, the third phase did not appear over all the volume concentrations of TBP. HCl + MgCl2 and HCl + NaCl were used as washing and stripping agents, respectively. Effects of washing and stripping conditions on washing and stripping performances were investigated too. Mg(OH)2 and MgCO3 were used as regeneration agents to regenerate the organic phase. The extraction efficiency of lithium ions remained at about 53% during reusing the organic phase ten times, demonstrating that the proposed extraction system had good stability and reusability.

    更新日期:2019-12-25
  • A simple process for the recovery of palladium from wastes of printed circuit boards
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-24
    Damien Bourgeois; Valentin Lacanau; Régis Mastretta; Christiane Contino-Pépin; Daniel Meyer

    An efficient process for the recovery of palladium from waste printed circuits boards (PCBs) is detailed. Palladium is employed as an electrode material in multi-layer ceramic capacitors (MLCCs). These components can be easily removed from PCBs by de-soldering. As palladium is alloyed with silver, its dissolution is readily achieved using dilute nitric acid. As a result, a solution containing palladium along with base metals, mostly copper and iron, is obtained. This solution is then processed through solvent extraction (SX) with a solvent based on N,N′-dimethyl,N,N′-dibutyltetradecylmalonamide (BDMA), a robust extracting molecule previously developed in the frame of the reprocessing of waste nuclear fuel. The volume of effluents generated during the SX sequence is limited: iron scrubbing is operated with a very low aqueous to organic phase volume ratio, no specific metal chelator is required for palladium stripping, and no shift from acidic to basic media is required. Finally, a ca 1 g/L Pd(II) aqueous solution with 99,4% purity is obtained, from which palladium is directly isolated as dichlorodiammine palladium(II) salt (Pd(NH3)2Cl2) after precipitation with ammonia. Overall, palladium is quantitatively recovered from the leaching solution, and no palladium was detected in the remaining solid residue. Purity is high, as no contaminating metal could be detected in the final palladium salt. The proposed approach is simple and complementary to existing hydrometallurgical processes dedicated to gold and copper recovery.

    更新日期:2019-12-25
  • A fundamental study of gold leaching in a thiosulfate‑oxygen‑copper system in the presence of activated carbon
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-21
    O. Sitando; X. Dai; G. Senanayake; A.N. Nikoloski; P. Breuer

    Activated carbon has been found to significantly enhance the dissolution of gold in a thiosulfate‑oxygen‑copper system. Leaching tests using gold powder showed that the gold dissolution in a thiosulfate‑oxygen‑copper system in the absence of activated carbon was very slow, with only 2% gold dissolved over 24 h. In contrast, in the presence of activated carbon as an additive the gold leach recovery was dramatically improved to over 95% in the same period. Leaching and electrochemical studies using a gold rotating disc electrode have identified two impacts of activated carbon on the dissolution of gold: 1) enhancing the oxygen reduction half reaction via galvanic interaction and; 2) enhancing the gold oxidation half reaction via removal of the surface passivation. A combination of the two effects can potentially increase the gold leach rate to the same order of magnitude as a typical cyanidation rate (10−5 mol m−2 s−1). It has also been found that the presence of copper and the use of an elevated temperature are beneficial for the gold leaching; whilst the use of oxygen instead of air and change in pH between pH 7 and pH 10 have little impact.

    更新日期:2019-12-21
  • The anion effect on sodium aluminosilicates formed under Bayer process digestion conditions
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-20
    John Vogrin; Talitha Santini; Hong Peng; James Vaughan

    The removal of inorganic impurities Cl−, CO32– and SO42− from Bayer liquor largely relies on their incorporation into sodium aluminosilicates (ideal formulae Na8(AlSiO4)6 × 2yH2O; X = Cl−, OH−, ½ CO32−, ½ SO42−, Al(OH)4−, y = 0–4), a waste by-product formed from the precipitation of solution silicates. This paper aims to examine the effect of anion incorporation on the structural properties of sodium aluminosilicates precipitated from synthetic Bayer liquors containing 5.0 M NaOH, 2.0 M NaAl(OH)4, with 0–0.4 M NaCl or Na2CO3 or Na2SO4 under typical Bayer digestion conditions (150 °C/1 h, 250 °C/30 min). Added anions promoted desilication by up to 80% (as solution SiO2) compared to conditions without added impurities. Al(OH)4− and CO32– were found to be ubiquitous in Bayer sodium aluminosilicate regardless of synthesis conditions, and may occupy up to 75% and 85% of cages respectively; the maximum incorporations of Cl− and SO42− saw a similar extent. The incorporation of each inorganic anion increased with higher reaction temperature. Divalent anions CO32– and SO42− promoted the phase transformation from sodalite to cancrinite to a greater extent than the monovalent anions Cl−, OH−, Al(OH)4−, which did not exhibit a phase change. The amorphous content in precipitates decreased significantly in the presence of inorganic anions. The modelling of a unique Bayer hydroxy-cancrinite phase was necessary to match the aluminosilicate XRD patterns, and atomic positions and occupancies were determined through Rietveld refinement.

    更新日期:2019-12-21
  • Sulfuric acid leaching and recovery of vanadium from a spinel concentrate beneficiated from stone coal ore
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-20
    Xuexin Chen; Hui Wang; Baijun Yan

    In order to recover vanadium from vanadium-bearing black shale efficiently, a hydrometallurgical process is developed in this paper to treat the concentrate beneficiated from stone coal ore, in which the vanadium mainly occurs in the form of Fe3-xVxO4 spinel. At the first step, the leaching behaviors of Fe and V from the concentrate by using sulfuric acid solution are investigated in detail. The extraction rates of vanadium and iron could reach 92.5% and 98.5% respectively under the optimum leaching conditions of leaching temperature of 90 °C, sulfuric acid concentration of 25 wt%, leaching time of 90 min, L/S mass ratio of 30 and stirring speed of 600 rpm. Secondly, the iron impurity in the pregnant solution is removed efficiently by the precipitation method with Fe2O3 as nucleating agent. The effect of pH value, the amount of Fe2O3 nucleating agent and the precipitating time on the removal of iron and losing of vanadium are systematically investigated, and thereby >99.7% iron impurity can be removed with the loss rate of vanadium not higher than 2.5%. Finally, vanadium is precipitated from the purified leach solution as ammonium poly-vanadate by adding ammonium sulfate, and then the product of V2O5 is obtained by calcining the ammonium poly-vanadate. The purity of V2O5 powder can reach 92.0% approximately.

    更新日期:2019-12-21
  • Selective precipitation study for the separation of Fe and Ti from ilmenite
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-20
    Walter Purcell; Manish Kumar Sinha; Amanda Qinisile Vilakazi; Motlalepula Nete

    Ilmenite is major source of titanium dioxide production and contains high concentration of iron. It is crucial to selectively remove iron impurities during the titanium production process. The present study investigated the acid and flux fusion digestion techniques for complete dissolution of ilmenite and subsequent separation of iron and titanium by precipitation process. Analytical results indicated that the Na2HPO4/NaH2PO4·H2O, Na2B4O7 and LiBO2 flux fusion procedures were the most effective for complete dissolution of ilmenite mineral. The separation of Fe(II) and Ti(IV) from the phosphate fused solution by selective precipitation was studied using phenanthroline (phen), sodium tetraphenylborate (NaTPB) and 2-mercaptopyridine N-oxide sodium salt (NaPT) as precipitants. The combination of phen and NaTPB showed poor selectivity for the precipitation of either Ti(IV) or Fe(II) and both metals collectively precipitated under the investigated experimental conditions. Negligible selectivity was observed when only sodium tetraphenylborate was used. The selective separation of Fe(II) and Ti(IV) from fused solution using NaPT as precipitant was extremely successful with 100(1)% Fe(II) recovered in the precipitate (no titanium observed in precipitate) while 99.6(1)% Ti(IV) remained in the filtrate (no iron observed in the filtrate).

    更新日期:2019-12-21
  • 更新日期:2019-12-20
  • Removal of selenium from caustic solution by adsorption with CaAl layered double hydroxides
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-19
    Dong Li; Wen Yan; Xueyi Guo; Qinghua Tian; Zhipeng Xu; Liu Zhu

    Removal of selenium from caustic solution by adsorption with CaAl Layered Double Hydroxides (CaAl LDHs) was proposed. CaAl LDHs with a hexagonal platelet structure were successfully synthetized by co-precipitation. 94% of Se(VI) was removed at 30 °C for 30 min with NaOH concentration of 1 mol·L−1 and adsorbent dosage of 40 g·L−1. Temperature played an important role in Se(VI) removal. At low temperature (30 °C–70 °C), CaAl LDHs underwent an anion exchange with Se(VI) to form Ca4Al2O6SeO4(H2O)10, with the d-spacing expanding from 7.95 Å to 10.15 Å. When increasing temperature above 80 °C, Ca4Al2O6SeO4(H2O)10 began to decomposed to Ca3Al2O6(H2O)6 and Ca(OH)2, resulting in SeO42− into the liquor. Kinetic data were well fitted to pseudo-second-order model, indicating Se(VI) removal process was controlled by the chemisorption. The adsorption isotherms were in good agreement with Langmuir isotherm model, suggesting Se(VI) removal was a monolayer adsorption. The maximum adsorption capacity was calculated to be 138.76 mg·g−1 at 30 °C. Desorption and regeneration results indicated that CaAl LDHs can be reused at least three times without significantly reducing its absorption capacity for Se(VI).

    更新日期:2019-12-19
  • Process development for the recovery of high grade calcium tungstate from alkaline leach liquor of spent WMo catalyst
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-19
    B. Ghadai; P.C. Rout; D. Mohapatra; B. Padh; B. Ramachandra Reddy

    Molybdenum is often associated with tungsten based spent catalyst and must be removed from tungstate solution to obtain commercially acceptable tungsten products. In order to address this problem, a different approach has been proposed in the present work. A two step process based on selective thionization of Mo using Na2S at alkaline condition followed by W precipitation as calcium tungstate (CT) using lime (Ca(OH)2) was studied. Various operating parameters were tested and optimum conditions for Mo thionization and W precipitation were developed. The CT produced by the conventional process was used as a reference to check the improvement in the proposed process with respect to Mo impurity. Under the optimum conditions, 92.7% Mo was rejected to the CT filtrate and 99.7% W converted to CT. The CT obtained from the proposed process contained 0.53% Mo, which was much less as compared to the CT obtained from the conventional process having 2.5% Mo using the same leach solution. High-grade ammonium paratungstate (APT) containing <100 ppm Mo was obtained by treating the CT, which can be used for the tools industry and other applications.

    更新日期:2019-12-19
  • Extraction of lithium, rubidium and cesium from lithium porcelain stone
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-19
    Jinliang Wang; Kaiqi Wu; Huazhou Hu

    The anticipated increase in demand for Li, Rb, and Cs raises growing concern due to the expected shortage in alkali metals available for extraction from ores. In this study, two kinds of additives (Na2SO4 and CaCl2) were used to selectively extract alkali metals from lithium porcelain stone. HSC modelling was used to simulate the process of roasting the ore in the presence of these additives, and to predict the temperature effect in addition to the ore/Na2SO4/CaCl2 mass ratio. Under the optimized conditions, the Li, Na, K, Rb, and Cs extraction efficiencies were 98.70, 49.80, 37.90, 97.27, and 98.40%, respectively. The optimal roasting conditions were found to be an ore/Na2SO4/CaCl2 mass ratio of 1/0.2/0.2 with heating at 850 °C for 60 min, while the optimal water leaching conditions were a liquid/solid ratio of 1/1 and a stirring speed of 300 rpm at room temperature for 60 min. Upon analysis of the calcined and leaching residues, the extraction mechanism was demonstrated to involve a highly chemoselective ion-exchange process between the alkali metals present in the ore, the Na+ in Na2SO4, and the Ca2+ in CaCl2. After this process, the concentrations of the alkali metals in lixivium were approximately 3.43 g/L Li, 25.50 g/L Na, 11.00 g/L K, 1.35 g/L Rb, and 0.56 g/L Cs, thereby indicating the feasibility of this process.

    更新日期:2019-12-19
  • Modifying the dewatering behaviour of iron solids from ferric sulphate solutions during lime treatment
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-19
    Cledwyn Tawanda Mangunda; Jochen Petersen; Alison Emslie Lewis
    更新日期:2019-12-19
  • Recovery of gallium from waste LEDs by oxidation and subsequent leaching
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-18
    M. Maarefvand; S. Sheibani; F. Rashchi

    In this paper, gallium recycling from waste light emitting diode (LED) by oxidation and subsequent leaching was studied. Gallium is present in the LED chip as gallium nitride. Disassembling and crushing of the LEDs were carried out after burning the polymeric parts, and then the chip is separated from the LED. Leaching of the gallium from the chips was performed after oxidation step at optimum temperature of 1100 °C. The oxidation heat treatment was carried out at 1000, 1100 and 1200 °C and the oxidation mechanism was studied in detail. Oxidation causes depletion of nitrogen gas and absorption of oxygen atoms by the gallium nitride structure, which results in the formation of a porous oxide structure. The minimum transformation temperature of gallium nitride to gallium oxide, was 1100 °C. In the final oxide phase, comparison of the structure and morphology of the chip surface after oxidation at 1200 °C and 1100 °C shows that at higher oxidation temperature the surface area decreases and the grain size increases. Changing the solubility of the phase containing the gallium by oxidation at different temperatures considering has been investigated. Leaching experiments were designed using design of experiment (DOE) method. At optimum leaching conditions of 4 M hydrochloric acid, 93 °C and 120 min, the gallium leaching recovery was 91.4%. Based on the results, leaching temperature is the most effective parameter in this process.

    更新日期:2019-12-19
  • A green method for decomposition of scheelite under normal atmospheric pressure by sodium phytate
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-18
    Xinrui Zhu; Xuheng Liu; Zhongwei Zhao; Xingyu Chen; Jiangtao Li; Lihua He
    更新日期:2019-12-19
  • Bioleaching of dewatered electroplating sludge for the extraction of base metals using an adapted microbial consortium: Process optimization and kinetics
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-17
    Lijuan Zhang; Wenbo Zhou; Yongdi Liu; Honghua Jia; Jun Zhou; Ping Wei; Hongbo Zhou

    The main objective of this study was to optimize bioleaching process parameters for high co-extraction of base metals (Cu, Ni, Zn, and Cr) from hazardous electroplating sludge using an adapted microbial consortium and to explore the relevant bioleaching mechanisms. Microbial cultivation and sludge bioleaching were separated. The effect of the relevant process parameters (i.e., bulk pH, pulp density, and Fe2+ concentration) on the extraction of four selected metals through bioleaching by an adapted microbial consortium was investigated in a 1 L stirred tank reactor. Results indicated that maximum metal solubilization (>95.6% for each of Cu, Zn, and Ni, and 90.3% of Cr) was achieved at a bulk pH of 2.0, Fe2+ of 9.0 g/L, and pulp density of 15% (w/v). Bioleaching kinetics of the selected metals was described by a modified shrinking core model. This indicated that the interfacial transfer and diffusion across the solid film layer was the rate controlling step and controlled the dissolution kinetics. Data from bioleaching and chemical leaching systems showed that bioleaching had some advantages over simple chemical leaching. The mechanisms of improved Cu, Ni, Zn, and Cr extraction by bioleaching were demonstrated. Bioleaching improved metal release, especially from the residual fraction, as indicated by Community Bureau of Reference (BCR) three-stage sequential extraction analysis. Most of the Cu, Ni, and Zn extraction was attributed to H+ attack, as these metals were primarily distributed in the water/acid soluble and exchangeable fractions, along with Fe and Mn oxyhydroxides (>72.3%). For the extraction of Cr, besides H+, microorganisms and Fe3+ were also responsible. They improved Cr extraction, especially from the residual fraction. These findings indicate that bioleaching with an adapted microbial consortium appears promising for recycling and reutilizing valuable heavy metals from hazardous electroplating waste.

    更新日期:2019-12-18
  • Stabilization of arsenic sulfide sludge by hydrothermal treatment
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-17
    Hui Xu; Xiaobo Min; Yunyan Wang; Yong Ke; Liwei Yao; Degang Liu; Liyuan Chai

    Arsenic sulfide sludge (ASS) generated during the treatment of strongly acidic wastewater with sulfide precipitation method has long been a problem for the nonferrous smelting enterprises. In this study, stabilization of ASS from a lead and zinc smelter by hydrothermal treatment was investigated. The ASS was characterized with high contents of arsenic (46.9%) and sulfur (32.6%), and leaching concentration of arsenic was determined to be 702.0 mg/L. The parameters of the hydrothermal treatment were studied in detail. It was found that the leaching concentrations of As, Pb and Cd, dehydration ratio, density and morphology of ASS changed dramatically during the hydrothermal treatment. Comprehensive consideration of these changes, the optimal conditions were determined to be temperature of 200 °C, reaction time of 4 h, liquid-to-solid (L/S) ratio of 1:1 and the initial pH of 2. Under the optimal conditions, the leaching concentration of As for the treated ASS decreased to <5 mg/L. The yellow muddy ASS changed into a big bulk with metallic luster. The density of the ASS increased from 1.20 g/cm3 to 2.29 g/cm3, the moisture content decreased from 62.59% to 6.50%, and the volume reduction ratio reached 91.67%. After the hydrothermal treatment, the speciation transformation of As, Pb and Cd occurred. Some of the As, Pb and Cd in ASS transformed into a more stable speciation after the hydrothermal treatment. As a result, the stabilization of As, Pb and Cd attributed to both of the microstructure transformation of ASS and the speciation transformation of As, Pb and Cd.

    更新日期:2019-12-18
  • Effect of stratified stacks on extraction and surface morphology of copper sulfides
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-06
    Leiming Wang, Shenghua Yin, Aixiang Wu, Xun Chen
    更新日期:2019-12-06
  • Extracting heavy metals from electroplating sludge by acid and bioelectrical leaching using Acidithiobacillus ferrooxidans
    Hydrometallurgy (IF 3.465) Pub Date : 2019-12-03
    Ping Wu, Li-juan Zhang, Chao-ba Lina, Xin-xin Xiea, Xiao-yu Yonga, Xia-yuan Wua, Jun Zhou, Hong-hua Jia, Ping Wei

    Electroplating sludge (EPS) is a potential secondary resource; the heavy metals it contains show microbial toxicity in the bioleaching process and can be recycled as well. The aim of this work was to utilize optimized acid leaching to reduce the toxicity of heavy metals in EPS. Bioelectrical reactors (BERs), which can directly supply electron donors and acceptors for Acidithiobacillus ferrooxidans (A. ferrooxidans), were combined with acid leaching to achieve the progressive attack by bacteria on heavy metals in EPS. The results showed solution pH in acid leaching and voltage in BERs bioleaching played important roles in heavy metals extraction. Under the optimized acid leaching condition of processing pH 2.2, 75.8% of the copper (Cu), 84.4% of the zinc (Zn), 80.9% of the chromium (Cr), and 65.8% of the nickel (Ni) were leached in 9 h. An additional extraction of 11.7% Cu, 4.6% Zn, 6.0% Cr, and 11.7% Ni from acid-leached EPS residuum was produced in 0.2 V BERs compared with shaken bioleaching in 60 h. Various characterization methods such as transmission electron micrographs and cyclic voltammograms confirmed the Fe2+ oxidation ability of A. ferrooxidans was improved in the 0.2 V BERs, and the response of rus operon was downregulated by 2.3–3.5 times as determined by quantitative real-time polymerase chain reaction. These findings have great significance in constructing a model of heavy metals extraction and Fe2+ oxidation by A. ferrooxidans in BERs. The results of the leaching process are also significant for understanding how to implement these processes on an industrial scale.

    更新日期:2019-12-03
  • Recovery of strontium (Sr2+) from seawater using a hierarchically structured MnO2/C/Fe3O4 magnetic nanocomposite
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-30
    Jungho Ryu, Jeongsik Hong, In-Su Park, Taegong Ryu, Hye-Jin Hong
    更新日期:2019-11-30
  • Membrane electrolysis for separation of cobalt from terephthalic acid industrial wastewater
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-30
    Rui Gao, Xochitl Dominguez Benetton, Jeet Varia, Bernd Mees, Gijs Dulaing, Korneel Rabaey

    Recovery of valuable metals from wastewaters containing both metals and organics is challenging with current technologies, in part due to their interactions. Typical approaches are chemical intensive. Here, we developed a membrane electrolysis system coupled to an acidic and alkaline crystallizer to enable separate precipitation of the organics and metals without additional chemicals. The target industrial wastewater contained mainly purified terephthalic acid (PTA), benzoic acid (BA), p-Toluic acid (PA), cobalt (Co), and manganese (Mn). We examined the removal and recovery efficiency of PTA and cobalt from two types of synthetic stream and the real process stream using several configurations. The acidic crystallizer reached a removal efficiency of PTA of 98.7 ± 0.2% (Coulombic efficiency 99.71 ± 0.2%, pH 3.03 ± 0.18) in batch tests of the simple synthetic stream. The alkaline crystallizer achieved a cobalt recovery efficiency of 94.51 ± 0.21% (Coulombic efficiency 87.67 ± 0.31%, pH 11.37 ± 0.21) in batch tests of the simple synthetic stream (TPA and Co). Then, the system was operated continuously with complex synthetic stream (TPA, BA, PA, Co and Mn). The alkaline crystallizer achieved a cobalt recovery efficiency of 97.78 ± 0.02% (Coulombic efficiency 90.45 ± 0.17%)at pH 11.68 ± 0.02. The acidic crystallizer obtained a PTA removal efficiency of 61.2 ± 0.1% (Coulombic efficiency 62.3 ± 0.2%) over 144 h (pH 3.71 ± 0.03). A real stream was tested over 5 h runs in batch showing 31.1 ± 1.0% PTA (Coulombic efficiency 26.5 ± 0.2%) and 82.92 ± 0.22% cobalt removal (Coulombic efficiency 75.27 ± 0.31%) at pH 2.71 ± 0.12 and 8.07 ± 0.02, respectively. However, micron-scale precipitates were generated from real stream tests. To conclude, the membrane electrolysis cell coupled with acidic and alkaline crystallizers enabled simultaneous separation of PTA and cobalt as solid precipitates from a complex stream with no chemical addition. The efficiencies were lower with the real stream than the synthetic streams, showing the impact of matrix effects and the need to optimize the performance of the crystallizers.

    更新日期:2019-11-30
  • Biochemical treatment of leachates from hydrometallurgical recycling of spent alkaline batteries
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-30
    Zhendong Yang, Witold Uhrynowski, Grazyna Jakusz, Jacek Retka, Joanna Karczewska-Golec, Klaudia Debiec-Andrzejewska, Zbigniew Rogulski, Lukasz Drewniak

    Recycling of waste electrical and electronic equipment including spent batteries focuses on maximizing the material recovery efficiency (of metals, polymers, or solvents) and decreasing the negative environmental impact of leachates that remain after the treatment (i.e. the secondary wastes). The major aim of this study was to develop a novel, low-cost biochemical treatment technology for the management of effluents generated during sulfuric acid–based hydrometallurgical recycling of spent alkaline batteries. We explored the use of various chemical reagents (40% NaOH, 20% Na2CO3, and 1% NH3(aq)) and biogenic ammonia produced by urea-degrading bacteria to increase the pH of the effluents (from pH 0.5 to pH 5.0) and prepare them for further treatment by sulfate-reducing bacteria. Comparisons of the pretreatment efficiency and metal and sulfate removal yields, as well as the characterization of the neutralization products (sediments and effluents) showed that the most promising results were obtained when the raw leachates were treated with 40% NaOH (to reach pH 3.5), followed by the addition of biogenic ammonia (to reach pH 5.0). Sulfate-reducing bacteria (SRB) activity led to a further pH increase (up to ~7.3), almost complete (99%) sulfate removal and metal sulfide (ZnS, MnS) precipitation, as up to ~99% of Zn and Mn were removed in SRB cultures to which appropriately diluted pretreated leachates had been added. The presented study indicated that the pretreatment and neutralization of hydrometallurgical effluents based on the use of urea-degrading and sulfate-reducing bacteria could be an attractive alternative to conventional chemical treatment.

    更新日期:2019-11-30
  • Comparison and optimization of the bio-cyanidation potentials of B. megaterium and P. aeruginosa for extracting gold from an oxidized copper-gold ore in the presence of residual glycine
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-29
    Marzieh Gorji, Mohammad Raouf Hosseini, Ali Ahmadi

    Considering the environmental issues of cyanide ion, cyanogenic bacteria which are capable of cyanide genesis may be regarded as a potential alternative to conventional cyanidation. The capacities of two cyanogenic bacterial strains namely Pseudomonas aeruginosa and Bacillus megaterium for the cyanide production and gold bioleaching from the pure gold particles and an oxidized gold-bearing ore (6.2 g/ton) were compared. Also, in order to maximize the cyanide bio-production and subsequently the gold recovery, the influences of the initial pH, glycine, FeSO4, NaH2PO4, and MgSO4 concentrations in the growth media were studied and optimized. In the optimal culture condition, P. aeruginosa and B. megaterium produced 66.35 and 67.05 mg/l cyanide, respectively, and 2.5 g/l glycine remained unconsumed. Therefore, bioleaching experiments were performed under the synergistic effect of the cyanide-glycine mixture through the active and passive approaches that the latter averagely improved the Au dissolution by 8%. The concentration of Au in the leachate of B. megaterium was higher in comparison with the other bacterium, and reached 205 and 32.2 μg/l for the pure gold and the original ore, respectively. Moreover, performing a pretreatment stage to remove metal contents before cyanidation, increased the final Au concentration to 44.4 μg/l. Finally, raising the bioleaching pH to 10 increased the Au concentration to 56.8 μg/l which represents >80% gold recovery. Although the Au extraction efficiencies of both strains were low, the observed improvements due to the ferrous and magnesium addition, copper removal, and pH increase are promising for the future works.

    更新日期:2019-11-30
  • Selective recovery of Sb and Te from the sodium sulfide leach solution of Te-bearing alkaline skimming slag by drop-wise H2O2 addition followed by Na2S–Na2SO3 precipitation
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-29
    Zhipeng Xu, Xueyi Guo, Dong Li, Qinghua Tian, Liu Zhu

    Sb and Te in Te-bearing alkaline skimming slag were extracted into a leach solution using a two-stage sodium sulfide leaching process. In this study, a possible method for selective recovery of Sb and Te from the sodium sulfide leach solution by drop-wise H2O2 addition followed by Na2S–Na2SO3 precipitation was developed. 99% of Sb was precipitated selectively at 50 °C for 100 min with addition of 90 mL H2O2 while Te precipitation was near-zero. Te in the oxidized solution was converted to the form of TeS42− with Na2S, and recovered by Na2SO3 reduction. The results indicated that 95% of Te was precipitated under the optimum conditions: 1.0 of Na2S excess coefficient, 1.75 of Na2SO3 excess coefficient, 50 °C of temperature and 30 min of time. XRD pattern and chemical analysis indicated that the H2O2 oxidation precipitate was NaSb(OH)6 with Sb content of 46.92% and the Na2S–Na2SO3 precipitate was elemental Te with a purity of 98.61%.

    更新日期:2019-11-29
  • Recovery of Pd(II) from leach solutions of automotive catalysts by solvent extraction with new thiophosphate extractants
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-28
    Manabu Yamada, Muniyappan Rajiv Gandhi, Uma Maheswara Rao Kunda, Tomoki Mori, Kazutoshi Haga, Atsushi Shibayama
    更新日期:2019-11-29
  • Treatment of aluminum and fluoride during hydrochloric acid leaching of lepidolite
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-28
    Jinlian Liu, Zhoulan Yin, Wei Liu, Xinhai Li, Qiyang Hu

    A two stage hydrochloric acid leaching process is proposed for the treatment of lepidolite and recovery of alkali metals. The separation characteristics of aluminum and fluoride in the leachate were also determined. The transformation of lepidolite into silica-like residue was tentatively identified through X-ray diffraction measurements. The leach liquor was heated and concentrated and by evaporation to drive off to remove some of the hydrogen chloride and hydrogen fluoride from the acidic leachate, followed by cooling to deposit crystals. This yielded an overall hydrogen chloride and hydrogen fluoride removal of 25.4% and 2.52%, respectively. The main components of the crystals were aluminum and potassium chlorides, with small amounts of fluoroaluminate, polyaluminum chloride, and aluminum hydroxyfluoride. The crystals were calcined at 350 °C, with a further 43.9% of hydrogen chloride and 4.33% of hydrogen fluoride being driven off and captured by adsorption equipment, which was beneficial for the subsequent separation of impurities. Investigation of the major mineral phases revealed that lower temperature calcination of the crystals tended to produce less-soluble polyaluminum chloride, aluminum hydroxyfluoride, fluoaluminate, and alumina. Water leaching of crystals after calcination at 350 °C gave a leach liquor with 7.74 g/L of lithium, 0.15 g/L of aluminum and 0.25 g/L of fluoride. The fluoaluminate in the leach liquor led to the production of secondary precipitates after neutralization. The [AlFn]3-n species were partially dissociated to F− and Al(OH)4− at a strongly basic pH. The residual aluminum and fluoride concentrations were 0.01 g/L and 0.05 g/L, respectively, at the pH of 9. Since alkali chlorides such as lithium chloride are very soluble, there was less lithium loss during neutralization than in the corresponding sulfate system.

    更新日期:2019-11-29
  • Removal of aluminum from rare-earth leaching solutions via a complexation-precipitation process
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-28
    Yudong Wang, Jinhui Li, Yan Gao, Yang Yang, Yang Gao, Zhifeng Xu

    Due to the fact that the presence of aluminum in the leaching solutions of the ionic rare-earth ore adversely affects the subsequent extraction and separation of the REES (rare-earth elements), the aluminum must be reduced as soon as possible. Previously, organic substances with functional groups of carboxyl, hydroxyl, and amino, which can form stable and insoluble water complexes with aluminum ions in aqueous solutions under certain conditions, have been studied. This study used 8-hydroxyquinoline as the selective complexing precipitant for the purpose of complexing and precipitating aluminum in a rare-earth leaching solution. The results revealed that, when the amount of 8-hydroxyquinoline was 1.25 times that of the theoretical reaction amount; the reaction time was ten minutes; reaction temperature was 60 °C; and final pH of the solution was 4.5, then the Al3+ removal reached 94.39%, and the RE3+ loss was only 8.21%. Additionally, the obtained 8-hydroxyquinoline aluminum was found to have the advantages of a rapid precipitation rate, large crystal particles, and small entrainment losses, and filtration had been easily completed. In addition, the characteristics of the obtained 8-hydroxyquinoline aluminum would allow it to be used as photoelectric material with a high market value.

    更新日期:2019-11-29
  • Interaction mechanism between marmatite and chalcocite in acidic (microbial) environments
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-28
    Yisheng Zhang, Hongbo Zhao, Yanjun Zhang, Hongwei Liu, Huaqun Yin, Jiushuai Deng, Guanzhou Qiu
    更新日期:2019-11-29
  • A kinetic and mechanism study of silver-thiosulfate complex photolysis by UV-C irradiation
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-26
    Chao Han, Guangxin Wang, Chu Cheng, Chaoyang Shi, Yichao Yang, Mingjin Zou

    The feasibility of UV-C irradiation (24 W, mercury lamp, 254 nm) to photolyze the soluble silver–thiosulfate complex was examined in this work. The photolysis parameters including initial silver concentration, initial thiosulfate concentration, initial pH, temperature which may potentially influence photolysis kinetic of complex solution were optimized to achieve silver recovery of 80.46% after 4 h. The characterization including X-ray diffraction (XRD), particle size distribution, SEM-EDS and X-ray photoelectron spectroscopy (XPS) were applied to confirm the composition of photoproducts as Ag2S, S, Ag, and elaborate mechanism of the photolysis reaction. The kinetic study revealed that it follows the first-order reaction kinetics, and the apparent rate constant (kobs) of photochemical reaction was calculated at different conditions. The rate constant equation of step reactions was solved at fix conditions, and the rate determination step is determined.

    更新日期:2019-11-27
  • Electrochemical separation of magnesium from solutions of magnesium and lithium chloride
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-20
    Xi-Juan Pan, Zhi-He Dou, De-Liang Meng, Xiu-Xiu Han, Ting-An Zhang

    In the process of extracting lithium from salt lake brines with high Mg/Li mass ratio, a large amount of crude carbonate products of magnesium will be treated by the method of land stockpiling, which not only occupies much land and affects the environment, but also causes a waste of magnesium resources. In this work, the multi-stage membrane electrolysis process was proposed for the extraction of magnesium and the separation of lithium from brines, and magnesium hydroxide with high purity was directly prepared, which can be used as a flame retardant. According to the experimental results, the concentrations of Mg2+ and Li+ in the anolyte were reduced to 0.026 g/L and 0.15 g/L, respectively, and the Mg/Li mass ratio decreased from 98 to 0.17. Meanwhile, the extraction rate of magnesium (98.86% > 89.97%), current efficiency (86.69% > 80.75%) and product purity of Mg(OH)2 (99.93% > 99.46%) in multi-stage electrolysis process were higher than those in one-stage electrolysis, while the transfer proportion of lithium (42.31% < 50.00%), magnesium residual concentration (0.03 < 0.16 g/L) and Mg/Li ratio (0.17 < 1.23) in multi-stage electrolysis process were lower than those in one-stage electrolysis. Additionally, the higher separation efficiency and extraction rate of magnesium can be obtained in the two-stage electrolysis with the electrolysis of 8 h.

    更新日期:2019-11-21
  • Ammonium thiosulfate extraction of gold from printed circuit boards (PCBs) of end-of-life mobile phones and its recovery from pregnant leach solution by cementation
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-18
    Sanghee Jeon, Carlito Baltazar Tabelin, Ilhwan Park, Yoshito Nagata, Mayumi Ito, Naoki Hiroyoshi

    In this study, the ammonium thiosulfate leaching of gold (Au) from printed circuit boards (PCBs) of end-of-life mobile phones and the subsequent recovery of dissolved metals from pregnant leach solution via cementation were elucidated under various conditions. Over 99% of Au was extracted from crushed PCBs (D50 = 85 μm) under the following conditions: 1 M of Na2S2O3, 10 mM of CuSO4, 1 M of ammonia/ammonium concentration, 0.1 g/10 ml of solid-to-liquid ratio, and a 24 h of leaching time in the presence of oxygen. In contrast, the recovery of Au ions via cementation was more favorable in the absence of oxygen. Among the various cementation agents evaluated, copper (Cu) was the most selective and recovered around 95% of extracted Au from the pregnant leach solution even in the presence of various coexisting metal ions. The cementation of Au exhibited two distinct kinetic regions: (1) an initially rapid rate, and (2) a more gradual and constant rate. Finally, the use of Cu plates to recover Au ions from ammonium thiosulfate pregnant solution of crushed PCBs is proposed, which could selectively recover about 80% of dissolved Au and is easier to handle and reuse compared with Cu powder.

    更新日期:2019-11-18
  • Pre feasibility study in hydrometallurgical treatment of low-grade chalcopyrite ores from Sarcheshmeh copper mine
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-18
    Mohammad Mokmeli

    Chalcopyrite heap leaching is not yet a commercial reality, not just because of its lower recovery or slower kinetics, but rather, because of the economic impacts lower recovery and slower kinetics impose to the operating cost of the process. Considering the importance of the financial analysis on the economics of the operation, in this research, the economics of hydrometallurgical treatment of low-grade chalcopyrite deposit at Sarcheshmeh mine as a function of ore grade and extraction recovery were investigated. First, a brief history and theory of chalcopyrite ore leaching has been reviewed, showing that bio heap leaching at a possibly higher temperature with forced aeration is the only viable technique in treatment of low-grade chalcopyrite ores. In the economic feasibility study section, an operating cost estimate, capital cost estimate and economic analysis for a plant with 7000 tons per year copper cathode production capacity as a function of ore grades, acid consumption and heap leaching recoveries were investigated. Preliminary capital cost and operating cost estimates were made within two scenarios for a plant utilizing bio heap leaching, solvent extraction and electrowinning of low-grade chalcopyrite ore. The operating cost, for instance, was shown to be between US$5.99/kg to US$4.29/kg of copper cathode for extraction recoveries of 30% to 50% in a scenario where the construction of new SX and EW plants are required (Scenario 1). The operating cost was shown to reduce to US$5.36/kg to US$3.66/kg, for a similar recovery range, if the current SX and EW facility can absorb the bio heap leaching solution (Scenario 2). Using the operating cost data and the current copper selling price, the ore cut-off grade as a function of copper extraction efficiency was identified. The economic analysis showed that for an ore containing 0.28% copper, 7000 tons per year of copper cathode production requires a total investment of 38 million US dollar. The internal rate of return for such a plant was shown to vary between −2% to 27% for copper extraction efficiencies between 30% to 50% (Scenario 1). The sensitivity analysis of the similar plant showed that a copper selling price of US$5/kg, for instance, can even make the 50% copper extraction efficiency economically unacceptable for scenario 1.

    更新日期:2019-11-18
  • Alkali baking and solvometallurgical leaching of NdFeB magnets
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-18
    Mehmet Ali Recai Önal, Sofía Riaño, Koen Binnemans

    End-of-life NdFeB magnets are an important secondary source of rare-earth elements (REEs) and cobalt. Recycling of these magnets can also mitigate the supply problems of its constituent critical REEs (mainly neodymium and dysprosium). The recycling of bonded NdFeB magnets has received much less attention than that of sintered NdFeB magnets. In this study, a novel flow sheet is presented for recycling of bonded NdFeB magnets that is applicable to sintered magnets as well. Demagnetized magnet powder was mixed with 25 or 40 wt./vol% NaOH solution and baked at 150 to 200 °C for 30 to 540 min. In this way, REE metals were transformed into their corresponding hydroxides, whereas iron metal formed NaFeO2. By washing the reaction mixture with water, 96.5% of Na was recovered as NaOH and Na2CO3, whereas 90.3% of B was recovered as borax. The calcine containing REE hydroxides and iron oxide was then leached at 60 or 90 °C with 20 vol% Versatic Acid 10 diluted in an aliphatic diluent. >95% of the REEs were dissolved, with <1% co-dissolution of iron and <10% co-dissolution of cobalt. Precipitation stripping with an oxalic acid solution quantitatively regenerated the organic solvent with virtually the same composition of fresh solvent. After calcination of the oxalate precipitate, a mixed rare-earth oxide with 98.4 wt% purity was produced. The waste oxalic acid solution (pH ≤1) containing co-dissolved sodium and minor amounts of iron and cobalt could be used as a leaching agent for Co in the maghemite-dominated residue.

    更新日期:2019-11-18
  • Precipitation of zinc from cyanide leach solutions using Trimercapto-s-triazine (TMT)
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-14
    E.Y. Yazici, F. Ahlatci, E. Yilmaz, O. Celep, H. Deveci

    Cyanide leach solutions produced from gold/silver ores can be contaminated with zinc due to the gold/silver cementation in Merrill-Crowe process and/or the dissolution of zinc minerals present in the ore. Zinc levels in cyanide solutions should be controlled to avoid potential problems in leaching and downstream processes associated with the accumulation of zinc. In this study, the application of a novel method was demonstrated for the precipitation of zinc from synthetic/real cyanide solutions using Trimercapto-s-triazine (TMT), a non-toxic organic reagent. Experimental studies have shown that precipitation of zinc with TMT is a fast process occurring in a short period of time i.e., ≤15 min. Increasing the concentration of TMT (33–90 mM) and pH (10–12.5) was found to improve the precipitation of zinc, which was unaffected by increasing the temperature (20–60 °C). Response surface methodology was adopted for detailed investigation of the effect of [TMT]/[Zn] ratio (2.70–16.25), [CN−]/[Zn] ratio (3.00–8.00) and initial concentration of Zn (50–950 mg/L) on the precipitation of zinc. High recoveries (≤95.4%) were obtained under suitable conditions. Precipitation tests were also performed using synthetic multi-metal and real leach solutions. The complete recovery/dissolution of zinc from the precipitates was also demonstrated using different acids (HCl and H2SO4). The findings have shown that TMT can be effectively used as an environmentally friendly reagent for removal of zinc from cyanide leach solutions.

    更新日期:2019-11-14
  • A method for the removal of trace iodine from wet-process phosphoric acid
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-14
    Siqi He, Qianlin Chen, Xianquan Ao, Cuiqin Li, Ming Yu, Yonghui Zuo

    Abstract An effective method for extracting trace iodine from wet-process phosphoric acid (WPA) was designed. The iodine content in WPA was determined using an iodide-selective electrode. In addition, in this method, the sample solution, which contained approximately 2 ppm iodide, was phosphoric acid (PA) from WPA. The optimal extraction conditions were as follows: the PA/H2O2 volume ratio was 1:24, the PA/simethicone volume ratio was 1:3, the reaction time was 1 h, the reaction temperature was 45 °C, and no stirring was needed. The extraction yield of iodine reached 95%. A kinetic model was established based on bubbles with different rising velocities, and the characteristic viscosities of the gases as well as the heat flow rates of the bubbles were determined to simulate bubble movement. Then, the extraction principle was discussed, and the effect of bubble movement on extractability was analysed. The extractant (simethicone) can be recycled. Therefore, the proposed method can be considered a rapid, simple, and environmentally friendly method of extracting trace iodine from WPA.

    更新日期:2019-11-14
  • Uranium recovery from sandstone-type uranium deposit by acid in-situ leaching - an example from the Kujieertai
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-13
    Yipeng Zhou, Guangrong Li, Lingling Xu, Jinhui Liu, Zhanxue Sun, Weijun Shi

    The factors influencing uranium recovery in water-rock systems during acid in-situ leaching (ISL) were studied at the Kujieertai uranium deposit in Xinjiang. Using an ISL unit, a field leach trial (FLT) had been carried out to test the sequential effects of a leaching solution without oxidant (H2SO4 solution 4–8 g/L) and a leaching solution with oxidant (H2SO4 3–7 g/L, and Fe (III) 2–6 g/L). The observation of the leaching process revealed clearly defined stages of uranium release from the solid mineral to solution. Uranium mobilization from solid mineral into solution can be described in four stages. At the beginning of the acid ISL process, there was no oxidant to be added to the leaching solution and the desorption of hexavalent uranyl ions in the open pores, as well as dissolution of hexavalent uranium minerals, led to a short-term peak in the pregnant solution, which happened while pH decreased from about 5.3 to 2.62. Following the depletion of the adsorbed hexavalent uranium and a decline in uranium dissolution intensity, the addition of Fe(III) facilitated the oxidation of tetravalent uranium, which enabled intensive uranium mobilization again. During this process, the dissolution of uranium had a strong positive correlation with the reduction of Fe(III) and Eh in the leach solution. Beside hydrochemical factors, the deportment of uranium was also an important factor affecting uranium recovery. Uranium located in the open pores can be completely exposed to the solution and the mobilization intensity was significantly affected by hydrogeochemical conditions; but the uranium present in microfissures and in the ore matrix could not be fully exposed to the solution, so, their dissolution intensity was primarily controlled by corrosion and permeability of the ore. In general, the hydrogeochemical conditions and the deportment of uranium were the external and internal factors that significantly affected the dissolution and recovery of uranium in the early and middle stages of the FLT. However, in the latest stages, due to uranium depletion, enhancing the chemical potential of the leaching solution, specifically acidity and/or the amount of oxidant, had little improvement on uranium recovery.

    更新日期:2019-11-13
  • A cleaner electrolysis process to recover alumina from synthetic sulfuric acid leachate of coal fly ash
    Hydrometallurgy (IF 3.465) Pub Date : 2019-11-13
    Yuan Shi, Kai-xi Jiang, Ting-an Zhang

    The realization of clean extraction of aluminum hydroxide from high-alumina coal fly ash would be beneficial to achieve better overall coal utilization, and renders environmental and economic benefits. The current study mainly aimed to develop a nonhazardous approach to conduct electrolysis for alumina extraction from sulfuric acid leachate of high-alumina coal fly ash. The XRD, SEM, LPSA, FT-IR and ICP-AES results revealed that aluminum hydroxide was a main electrolysis product, with current efficiency of 83.25% under the optimized conditions as t = 1 h, J = 600 A/m2. The median particles of aluminum hydroxide after 1-h and 6-h electrolysis were 35.3 and 40.1 μm, respectively. The electrolysis mechanism was analyzed by cyclic voltammetry, which showed that the H2O gained electrons on the cathode to form OH– and H2. The OH– reacted with Al3+ to form Al(OH)3. In addition, the effluent of electrolysis was sulfuric acid and can be reused as a leaching reagent to promote zero pollution discharge. Hence, the electrolysis process provided an environment-friendly and efficient approach for alumina extraction from high-alumina coal fly ash.

    更新日期:2019-11-13
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