Hydrometallurgy最新文献

The low bio-production of Fe³⁺ as a leaching agent is one of the main limitations to implementing industrial bio-processes at feasibility conditions. The main limitation of the bio-oxidation process of Fe²⁺ is the low oxygen transfer to the aqueous phase because of the low oxygen solubility. This study assesses the effectiveness of the venturi jet as an innovative and intensive aeration device for overcoming the oxygen limitation in a continuous ferrous oxidation process in a fixed-bed reactor with immobilized acidithiobacillus ferrooxidans, in contrast to the conventional diffuser aeration device. Firstly, the influence of the airflow and the influence of the medium concentration were determined for the following parameters for both aeration devices; Volumetric mass transfer coefficient (k_La), Standard Oxygen Transfer Rate (SOTR), Standard Aeration Efficiency (SAE), and Standard Oxygen Transfer Efficiency (SOTE). Then, both aeration devices were compared in a continuous bio-oxidation process in an up-flow packed bio-reactor (UFPB). The system performance was assessed by monitoring temperature, pH, oxidation-reduction potential, and dissolved oxygen concentration for 69 days. Findings displayed that when aerating with the diffuser, the ferrous oxidation rate was restricted by the low dissolved oxygen availability, being about 1 ppm (1 mg L⁻¹). Under these oxygen-limiting conditions, the maximum ferrous (Fe²⁺) oxidation rate was 9.09 g L⁻¹ h⁻¹. However, when aerating with the venturi jet, the dissolved oxygen concentration increased up to 2.70 mg L⁻¹, achieving a maximum of 29.11 g L⁻¹ h⁻¹. So, this study has demonstrated that the change in the aeration device has resulted in an improvement in the process, achieving a 3.5-fold increase in the oxidation rate. Furthermore, the venturi jet offered additional advantages over the diffuser, such as requiring less power to deliver the same amount of air, being unaffected by jarosite precipitates, and not requiring a supply of compressed air.

The phosphoric acid produced by the nitric acid method cannot be used as an industrial-grade product as a result of the high calcium nitrate content. It can only be used for fertilizer production due to difficulty of complete removal of calcium nitrate. Herein, an efficient approach for the removal of calcium nitrate from the phosphoric acid produced by the nitric acid process was studied. The proposed process is based on solvent extraction with N, N, N′, N′-tetracyclohexyl-3-oxyglutaramide (TCHDGA). The effects of time, diluent, temperature, impurity ions, and the concentrations of extractant and nitric acid on the extraction of Ca²⁺ were considered. A series of characterization tests involving FT-IR spectroscopy, XPS analysis, slope analysis and X-ray single crystal diffracted analysis revealed that the stoichiometry of the complex is (Ca(NO₃)₂)(TCHDGA)₃. The concentration of Ca²⁺ in phosphoric acid drops below 5 mg/L a three-stage cross-current extraction process. The stripping efficiency of calcium nitrate in the organic phase by water is above 99.9%. The extraction efficiency of Ca²⁺ by TCHDGA remained above 96.8% after ten extraction-stripping cycles, realizing the efficient removal of calcium nitrate in the phosphoric acid produced by nitric acid process without changing the traditional production conditions.

Hydration of In³⁺ is the main factor limiting its extraction efficiency from an aqueous solution during a liquid-liquid extraction process. In this study, KCl was introduced into the aqueous solution to facilitate the formation of InCl₄⁻ of low charge density, which is expected to possess much weaker hydration compared with In³⁺, promoting the solvent extraction of indium. The crown ethers (CEs) with varied cavity sizes, benzo-18-crown-6 (B18C6), benzo-15-crown-5 (B15C5), and benzo-12-crown-4 (B12C4), were synthesized. The extraction performance of the CEs toward indium in the presence of sufficient KCl in the aqueous solution was investigated. The liquid-liquid extraction process was analyzed theoretically based on density functional theory (DFT) from the aspects of thermodynamics, geometric structure optimization, electrostatic potential (ESP), and independent gradient model (IGM). The theoretical evaluations agreed well with the experimental results that the hydration of indium could be significantly weakened through the formation of InCl₄⁻ and the complexation ability of the CEs toward indium is in the order of B18C6 > B15C5 > B12C4. The complexation mechanism between the CEs and indium during the extraction process was further explored with the assistance of ¹H NMR spectrum and SEM-EDS. The results indicate that crown ether coordinates with K⁺ to form [CE-K]⁺ at the two-phase interface, which further associates with InCl₄⁻ to create the complex of CE-KInCl₄, realizing the efficient indium extraction. Moreover, B18C6 showed excellent selectivity toward In³⁺ over the competing ions such as Fe³⁺, Al³⁺, Zn²⁺, Sn²⁺ and Ca²⁺ in a complex system. Indium could be efficiently recovered from the loaded organic phase by using 1 M HCl as the stripping agent with a stripping efficiency of 98.1%.

With a decline in high-grade molybdenum reserves, the development of other types of molybdenum resources have received increasing attention. Vanadium shale is a multi-metal shale and fine-grained sedimentary rock comprising small grains and various minerals. After leaching and extracting vanadium, the solution often contains a low concentration of molybdenum. However, because of the low molybdenum concentration, many processing plants treat it as an acidic wastewater, which wastes molybdenum resources and carries the risk of environmental pollution. The leaching process of vanadium shale mostly involves high-temperature and high-pressure operations, which greatly increase the content of impurity ions such as aluminium and phosphorus in the pregnant leach solution. These impurity ions increase the difficulty in separating and recovering molybdenum. In this study, the adsorption and separation of molybdenum at leach liquor of low molybdenum concentration were investigated. The effects of different factors such as: (i) pH of feed solution, (ii) adsorption time, and (iii) presence of impurity ions, aluminium and phosphorus, on the adsorption and separation of molybdenum using five different anion-exchange resins, D201, D296, D301, D314, and D301R, were investigated. The static adsorption and desorption test results showed a molybdenum adsorption capacity of 222 mg/g at pH = 1.5 by the D301 resin. The desorption efficiency using 20% NH₄OH was 96.1%. The adsorption efficiencies of aluminium and phosphorus were 1.31% and 3.10%, respectively. This is a better choice for separating molybdenum from complex solutions. The experimental results from spectra and theoretical calculations showed that the -NH group of D301 resin was combined with the O atoms of MoO₃·3H₂O, Al(SO₄)₂⁻, and H₂PO₄⁻ by electrostatic attraction. The binding energies of these three species were − 311 kJ/mol, −231 kJ/mol, and − 62.0 kJ/mol respectively, indicating that D301 resin preferentially adsorbed MoO₃·3H₂O. Based on the above results, the D301 resin can adsorb molybdenum(VI) in complex solutions under low pH conditions, and this study is expected to promote the comprehensive recovery of valuable metals from vanadium shale.

Hydrometallurgical processes for managing industrial waste have attracted significant attention due to tightening global standards on toxic emissions. Among these processes, the use of non-volatile hydrophobic deep eutectic solvents (HDESs) has emerged as a promising approach to optimising extraction processes. In this study, HDESs incorporating tributyl phosphate (TBP) and di(2-ethylhexyl)phosphoric acid (D2EHPA) were investigated in the context of the extraction and separation of elements found in lithium‑iron phosphate batteries, including lithium, aluminium, iron and copper. The physical properties of the HDESs, such as density, viscosity and refractive index, were characterized and the interactions between their components were analysed using infrared spectroscopy. Considering the different classes of extractants represented by D2EHPA and TBP, extraction efficiency for target metals was evaluated across a range of hydrochloric acid concentrations (1–10 mol/L). Optimal conditions for re-extraction (stripping) were identified for extractant regeneration and the production of individual metal ion solutions. Results demonstrated that Fe³⁺ ions could be extracted with an efficiency exceeding 99% across the majority of acidity levels, while Al³⁺ ions exhibited similar efficiency from a pH of 1.4. In contrast, Cu²⁺ ions showed limited extraction (<5%) at lower pH values but the level of extraction increased to 50% at pH 1.9 and above. Leveraging these findings, a sequential extraction scheme is proposed for Al³⁺, Cu²⁺, Fe³⁺ and Li⁺ from their mixture, based on a gradual reduction in solution acidity.

Glycine has been intensively investigated as a “green” lixiviant for precious and base metals. Alkaline glycine solutions to extract Ni from sulfide resources has shown promising results. However, a considerable amount of Ni will be lost in the wash solutions when leaching residues are washed during solid-liquid separation of the leachates from their respective leach residues. In this context, this study explored Ni recovery from alkaline glycine-based wash solutions using a polyamide nanofiltration membrane. In the tests using synthetic single and multi-metal solutions, the membrane achieved >95% rejection of Ni in the selected ranges of glycine/Ni molar ratio (up to 5), pressure (15–30 bar), initial nickel concentration (0.5–1.5 g/L), sodium sulfate background concentration (∼30 g/L) and under the use of different pH modifiers (aqueous ammonia and caustic soda). When using a real solution, the concentrations of Ni and other major elements (Cu, S, Co, Mg, Zn) in the final retentate increased by about 5 times at 80 wt% permeate recovery, leaving <3 mg/L major elements in permeate. The permeate stream could be recycled in the washing stage, and the retentate stream could be combined with the pregnant leach solution (PLS) for metals recovery. The investigation demonstrates some of the technical optionality for nickel recovery from filter wash solutions utilising nanofiltration within the context of alkaline glycine-based leach technology and preliminarily demonstrates where it can be used in the structure of flowsheets to recover valuable base metals and reagents for recycle. However, the increased membrane resistance causing a low permeate flux should be concerned due to the considerable dissolved salts, precipitation of gypsum and the increasing feed concentration over time.

In heap leach operations, metal recovery is fundamentally controlled by the ore's particle size distribution (PSD), which determines mineral exposure characteristics, the rate of leaching reactions, and fluid flow phenomena. A fluent circulation of solution through the heap is important for successful leach plant operation. The pore networks inside 6-in. diameter leach columns from the Rochester mine were scanned by X-ray Computed Tomography (XCT) at a voxel size of 100 μm, to estimate the permeability by Lattice Boltzmann Method (LBM). The bottom sections of 6-in. columns had much less porosity and corresponding permeability than the top sections. PSD of the bottom and top sections showed no migration of fines, and gravity compression reduced the bottom sections' permeability. The pore networks inside 4-in. diameter leach columns with controlled PSD were scanned by XCT at a higher resolution with a voxel size of 68 μm. In addition to the large particles (rocks) and pore network, another phase of agglomerated fines from local fluid movement was identified. This phase of agglomerated fines can overwhelm the volume of the pore network inside leach columns and thus reduce the permeability, leading to possible ponding issues in the heap.

The harmful effects of sulfur and organic substances pose constraints on the green and sustainable development of the Bayer process for alumina production. This research aims to develop a method that utilizes H₂O₂ to remove sulfur and organic substances during the digestion stage of bauxite, based on the mineralogical investigation of sulfur and organic substance. The extent of removal of S²⁻ and total organic carbon reached 95.6% and 68.0%, respectively, under most suitable conditions of 12% H₂O₂ dosage, temperature of 533 K, and duration of 80 min. Based on thermodynamic calculations, it is suggested that S²⁻ is oxidized to SO₄²⁻. Additionally, the free radical reaction mechanism of organic substances in H₂O₂ wet oxidation of Bayer liquor is proposed. The results confirm that this method does not introduce any impurities and does not have any impact on the digestion efficiency of alumina and the Bayer process.

A green chemistry process has been developed to recycle cathode material from end-of-life lithium ion batteries. NCM111 (LiNi_1/3Co_1/3Mn_1/3O₂) was completely leached with 13 M formic acid to produce two groups of salts with different solubilities: sparingly soluble cobalt, manganese, and nickel (CMN) formates and highly soluble lithium formate. During leaching, CMN formate salts exceeded their solubility limit in the pregnant leach solution (PLS) and crystallized. Mixed CMN formate salts were recovered by filtering the PLS. Lithium was completely recovered by evaporating the filtered PLS then thermally decomposing the lithium formate obtained in air to lithium carbonate. The purity of the lithium carbonate was 98.1 wt%.

The leaching process was optimized through response surface methodology experiments. The minimum time required to completely leach NCM111 with 13 M formic acid was 30.8 h. Optimum leaching conditions were L/S = 2.81 mL/g (equivalent to S/L = 356 g/L) and T = 95 °C. During leaching, 98% of CMN formate salts exceeded their solubility limit and crystallized from the PLS.

The recycling process is simple and generates no liquid or solid waste products. The only reagent is 13 M formic acid. The only by-products are water vapour, which can be condensed and reused, and carbon dioxide gas.

In the intensive cyanidation of gravity gold concentrates, sodium m-nitrobenzene sulfonate (NBS) is often used to supplement dissolved oxygen as the oxidant in the process. A previous paper presented the results of a largely electrochemical study of the behaviour of NBS during cyanidation of gold. The results confirmed that NBS acts as an oxidant in the cyanidation of gold and that the mixed potential model can be applied to describe the mechanism of its action. This paper explores the corresponding oxidation of sulfide minerals, that inevitably are contained in gold concentrates, by either dissolved oxygen or NBS. Using electrochemical techniques it was found that dissolved oxygen is effective in the oxidation of several sulfide minerals at pH values between 9 and 11. The effect of cyanide on both the anodic and cathodic processes has been studied. NBS has been found to be ineffective as an oxidant for all minerals tested except galena, even in the presence of cyanide.