Surface modification of ilmenite and its accompanied gangue minerals by thermal pretreatment: Application in flotation process

The effect of conventional thermal pretreatment on the surface properties of ilmenite and its accompanied gangue minerals was investigated using flotation experiments (microflotation and laboratory cell flotation), XRD, XPS and FT-IR analysis and zeta potential and contact angle measurements. After treatment at 600 °C for 25 min as optimal condition, the floatability of ilmenite is improved from 73.5% to 91% at a pH value of 6.3. As demonstrated by XRD and XPS analysis, under this pretreatment condition, the Fe³⁺ content increases by almost 16.5% without any phase decomposition and structural changes in ilmenite. FT-IR analysis and contact angle and zeta potential measurements give evidences that the improvement of ilmenite floatability can be related to the enhancement of collector adsorption and the formation of a more insoluble hydrophobic layer of ferric iron oleate. The ore flotation experiments show that the thermal pretreatment process without making a significant change in TiO₂ content of ilmenite concentrate enhances the TiO₂ recovery from 65.4% to 73.7%.     

Selective depression of copper-activated sphalerite by polyaspartic acid during chalcopyrite flotation

Environmentally friendly flotation reagent, polyaspartic acid (PAPA), was tested as a potential selective depressant in the flotation separation of chalcopyrite and Cu-activated sphalerite. The depression mechanism of PAPA was revealed by contact angle measurements, Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR) analysis and inductively coupled plasma (ICP) measurement. The micro-flotation tests with single minerals showed that PAPA selectively depressed Cu-activated sphalerite, while chalcopyrite remained floatable. Moreover, a concentrate containing 31.40% Cu with a recovery of 92.43% was obtained in flotation tests of artificially mixed minerals. Results of contact angle measurements, Zeta potential measurements and FT-IR spectrum revealed that PAPA exerted a much stronger adsorption on Cu-activated sphalerite surface than on chalcopyrite surface, preventing the further adsorption of sodium diethyl dithiocarbamate (DDTC) on its surface. ICP measurements indicated that PAPA had an excellent complexing ability with Cu²⁺ in flotation pulp, weakening the activation of Cu species on sphalerite surface and producing selective depression.     

The Role of Cu(I) in the Process of Forming Cu2–xS Coatings by a Chemical Route

The interaction of the Cu₂O adsorbed with Na₂S_n (n = 1–4), during formation of the Cu_2–xS coatings has been investigated by cyclic voltammetry.

The summarized reaction of this process has been shown to correspond to the equation:

Na₂S_n + Cu₂O_ad + H₂0 → Cu₂S_ad + (n–1)S^o + 2NaOH,

where S^o/Cu=(n–1)/2. Such a stoichiometry of reaction can be explained by the formation of an intermediate—the adsorbed polysulphide of Cu(I)—and by its subsequent decomposition into Cu₂S and S^o.

When a thicker coating is being formed, i.e., when the surface being coated is repeatedly immersed into an ammoniate solution of Cu(I) and S^o fully bounded:

S^o_ad + 2 Cu⁺ → CuS + Cu²⁺.

At the same time due to different solubility products (L=2.5·10^?48 and 6.3·10^?36 for Cu₂S and CuS respectively), an exchange

CuS_ad + 2(1–x)Cu⁺ → Cu_2–xS_ad+ (1–x)Cu²+ occurs.

After formation of Cu²⁺, parallel processes characteristic for the interaction of Cu(II) with Na₂S_n start to take place, during which S^o is also formed.     

Deep removal of copper from cobalt sulfate electrolyte by ion-exchange

SP-C was applied for the removal of Cu²⁺ from simulated cobalt sulfate electrolyte containing Co²⁺ 50 g/L and Cu²⁺ 0.5–2.0 g/L. Experimental conditions included pH of 2–4, temperature of 20–60 °C and contact time of 10–40 min. The investigation demonstrated that SP-C had recommendable efficiency in adsorbing Cu²⁺ from the electrolyte with 25- to 100-fold of Co²⁺. The optimal adsorption conditions of SP-C were pH of 4, contact time of 30 min and ambient temperature. The study also showed that the loaded resin could be effectively eluted with 2.0 mol/L H₂SO₄ solution at a contact time of 40 min; the peak concentration of Cu²⁺ in the eluate was about 35 g/L. The sorption characteristics of Cu²⁺ by SP-C could be described by Langmuir isotherm and the pseudo second-order kinetic equation. Infrared spectra showed that nitrogen atoms in the functional group coordinated with Cu²⁺ to form coordination bands.     

Carbon nanotube-chitosan composite electrodes for electrochemical removal of Cu(II) ions

Carbon nanotube-chitosan (CNT-CS) composite electrodes are prepared by firstly reacting oxidized CNT with thionyl chloride and then covalently grafting CS onto the surface of CNT. The electrochemical removal of Cu²⁺ ions by CNT-CS composite electrodes is investigated. The results show that CNT-CS Exhibits 85% Cu²⁺ removal ratio, 25% higher than that of pristine CNT, due to its lower zeta potential, higher surface area, more hydrophilic surface and more binding sites.     

Facile fabrication of spherical flower-like Mg(OH)2 and its fast and efficient removal for heavy metal ions

Spherical flower-like Mg(OH)₂ was fabricated from MgSO₄ effluent and its adsorption performance for heavy metal ions was evaluated. The appropriate fabrication conditions are as follows: Mg²⁺/NH₄OH molar ratio of 1:0.5, temperature of 120 °C and time of 1 h at Mg²⁺ concentration of 2 mol/L. Spherical flower-like Mg(OH)₂ composed of ultra-thin sheets exhibits an excellent adsorption ability for Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Fe³⁺ and Co²⁺, and the adsorption reaches the equilibrium in 6 min. The maximum adsorption capacities of the studied heavy metal ions onto Mg(OH)₂ at 20 °C are 58.55, 85.84, 44.94, 485.44, 625.00 and 27.86 mg/g, respectively. The adsorption is well fitted by the Langmuir model, indicating that the adsorption is monolayer. The adsorption kinetics follows the pseudo-second- order model. Chemisorption is the operative mechanism. Spherical flower-like Mg(OH)₂ is a qualified candidate for heavy metal ions removal.     

组合抑制剂石灰和腐植酸钠在锌砷混合精矿浮选分离中对毒砂的选择性抑制机理

采用石灰和腐植酸钠作为经硫酸铜活化和丁黄药捕收后毒砂的组合抑制剂.纯矿物浮选试验表明,组合抑制剂石灰和腐植酸钠能选择性地抑制毒砂.实验室小型闭路试验结果表明,石灰和腐植酸钠的协同抑制作用能较好地实现闪锌矿和毒砂的浮选分离,得到锌精矿中锌品位为51.21％、锌回收率为92.21％的良好指标.通过接触角测试、吸附量测试和X...     

Investigation of the Interaction Between Cu2-x S +So Coatings and Pd(II) Ions by Cyclic Voltammetry and X-ray Photoelectron Spectroscopy

The interaction between Pd²⁺ ions and Cu_2-xS coating formed by three cycles and containing ~30 at.% of elementary S has been investigated by the methods of cyclic voltammetry and photoelectron spectroscopy (one cycle of coating formation includes treatment of the surface with Cu(I)+Cu(II) ammoniate solution, hydrolysis of the adsorbed copper compounds and sulphidation of copper oxygen compounds in Na₂S_n solution). After exposure of such a coating to Pd²⁺ ions (1.7 mM PdCl_2’ pH-2), an exchange as well as a redox interaction between the coating components and Pd²⁺ ions has been shown to occur. Due to this the amount of copper in the coating decreases from 2 to 4 times and that of sulphur from 1.5 to 5 times. The coating modified in such a way has been found to contain up to 75 at.% of palladium, ~90% of it being in a metallic state.

It has been determined that at the beginning S^o is bound into a soluble compound:

2Pd²⁺ + S^o + 3H₂O → 2Pd^o + H₂SO₃ + 4H⁺.

The Cu₂S present in the coating is considered to interact with Pd²⁺, with the formation of Pd⁰ and CuPdS_2’, while CuS reacts most likely according to the reaction:

CuS + 3Pd²⁺ + 3H₂O → 3Pd^o; + H₂SO₃ + Cu²⁺ + 4H⁺.

The Cu_2-xS +S^o coating formed on a dielectric and modified with Pd²⁺, contrary to the initial Cu_2-xS +S^o coating, can be plated with copper from any electrolyte for copper deposition.     

Effects of copper ions on dissolution mechanism of marmatite

The dissolution mechanism of marmatite in the presence of Cu²⁺ was intensively studied by experiments and density functional theory (DFT) calculations. Leaching experiments showed that Cu²⁺ accelerated marmatite dissolution at high temperatures (above 55 °C), but the trend was reversed at low temperatures (below 45 °C), which may be because the reaction mechanism between Cu²⁺ and marmatite changed from surface adsorption to bulk substitution with increasing temperature. The substitution reaction caused more zinc atoms in the marmatite crystal lattice to be released and enhanced the electrochemical reactivity, while the adsorption of copper ions at low temperatures would passivate marmatite, thus inhibiting the reaction process. DFT calculations showed that the energy of the substitution reaction was more negative than that of the adsorption reaction at high temperatures, which further verified the proposed mechanism.     

A Study of the Interaction of Cu2-xS Coatings with S42- Ions by the Method of Cyclic Voltammetry

The interaction between Cu_2-xS (1<(2-x)<2) coatings without elemental sulphur and 0.01 M Na₂S₄ has been studied by cyclic voltammetry in 0.05 M H₂SO₄.

It has been shown that elemental sulphur forms in the Cu_2-xS coating exposed to Na₂S₄ solution. The highest S^o amount (2·10^?8 mol cm² during the first 30 s) has been found to be formed when the coating held in Na₂S₄ solution was Cut_1.25S. This is explained by the fact that during interaction of a Cu_2-xS coating with Na₂S₄ solution the unstable mixed polysulphides of Cu(I) and Cu(II) can be formed, e.g. in the case of Cu_1.25S (Cu₂S₄) the compound Cu₅S₇ can arise:

Cu^I₂Cu^II₃S₄ + Na₂S₄ → Cu^I₂Cu^II₃S₇ + Na₂S

which is again decomposed, initially into Cu₅S₄ and S^o:

Cu^I₂Cu^II₃S ₇ → Cu^I₂Cu^II₃S₄ + 3S^o

It is supposed that this process can recur and due to this four modifications of S^o arise as the time of treatment is increased. Stoichiometric sulphide Cu_l.99S does not interact and CuS interacts insignificantly with Na₂S₄ (after 30 s 0.4·10⁸ mol cm² of S is formed).

In a real process the contribution from the coating is supposed not to exceed several per cent.     

pH-dependent leaching mechanism of carbonatitic chalcopyrite in ferric sulfate solution

The dissolution of a carbonatitic chalcopyrite (CuFeS₂) was studied in H₂SO₄−Fe₂(SO₄)₃−FeSO₄−H₂O at varying pH values (0.5−2.5) and 25 °C for 12 h. Experiments were conducted with a size fraction of 53−75 µm. Low Cu recoveries, below 15%, were observed in all pH regimes. The results from the XRD, SEM−EDS, and optical microscopic (OM) analyses of the residues indicated that the dissolution proceeded through the formation of transient phases. Cu_3.39Fe_0.61S₄ and Cu₂S were the intermediate phases at pH 0.5 and 1.0, respectively, whereas Cu₅FeS₄ was the major mineral at pH 1.5 and 1.8. The thermodynamic modelling predicted the sequential formation of CuFeS₂→ Cu₅FeS₄→Cu₂S→CuS. The soluble intermediates were Cu₅FeS₄ and Cu₂S, whilst, CuS and Cu_3.39Fe_0.61S₄ were the refractory phases, supporting their cumulating behaviour throughout the dissolution. The obtained results suggest that the formation of CuS and Cu_3.39Fe_0.61S₄ could contribute to the passive film formed during CuFeS₂ leaching.     

Effects of annealing on elemental composition and quality of CZTSSe thin films obtained by spray pyrolysis

The spray pyrolysis was used for the deposition of Cu₂ZnSn(S, Se)₄ (CZTSSe) kesterite thin films. The basic spray pyrolysis solution was prepared from two precursor solutions containing thiourea and cooled to a temperature near 1°C, which leads to minimizing the number of insoluble hydrates of copper chloride. The optimal substrate temperature was 350°C and the distance from the sprayer nozzle 30 cm. The as-deposited Cu₂ZnSnS₄ layers were annealed in S₂ atmosphere for the compensation of the sulfur deficiency and with the addition of Sn in order to avoid tin loss. Cu₂ZnSn(S, Se)₄ thin films were obtained after the annealing of as-deposited films in the (S₂ + Se₂) atmosphere. The surface morphology and composition of obtained thin films were investigated using the energy dispersive X-ray (EDX) microanalysis and Raman spectroscopy measurements. The structural characterization by the grazing incidence X-ray diffraction (GIXRD) showed the presence of Cu_2–x S phases in all of the annealed thin films. For the Se/(S + Se) ratio of the thin films annealed in the (S + Se) atmosphere was established from EDX measurements and analysis of GIXRD data, the results are in satisfactory agreement.     

Ni（OH）2 particles synthesized by high energy ball milling

1 Introduction Ni(OH)2/NiOOH has been used as positive materials in alkaline secondary batteries for more than 100 years[1- 3]. The performance improvement of Ni(OH)2/NiOOH electrode is crucial for the application of these batteries as they are all positi…     

Sustainable copper extraction from mixed chalcopyrite–chalcocite using biomass

This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium at 33.3 °C and ferric leaching process were attempted. Bioleaching experiments were settled with a fraction size of −75+53 µm. Bacteria were used as the catalyst. A copper yield of 65.50% was obtained. On the other hand, in ferric leaching process, with a fraction size of −53+38 µm, when the temperature was increased to 70 °C, the copper leaching rate increased to 78.52%. Thus, comparatively, the mesophilic bioleaching process showed a more obvious advantage in copper extraction than leaching process with a high temperature. However, it has been resolved from the characterization performed using SEM−EDS, FTIR and XRD observations coupled with different thermodynamic approaches that, the indirect mechanism is the main leaching mechanism, with three transitory mechanisms (polysulphide, thiosulphate and elemental sulphur mechanisms) for the mixed chalcopyrite−chalcocite ore. Meanwhile, the speciation turns into Cu₂S−CuS−Cu₅FeS₄−Cu₂S before turning into CuSO₄. While ferrous oxidation and the formation of ferric sulphate occur, and there is a formation of strong acid as bacteria digest sulphide minerals into copper sulphate at low temperature, which is why this copper production scenario requires a redox potential more than 550 mV at room temperature for high copper leaching rate.     

Enhancement of galena-potassium ethyl xanthate flotation system by low power ultrasound

The objective of this study is to investigate the improvement possibilities of the floatability of galena with ultrasonic application in the presence of potassium ethyl xanthate (KEX). For this purpose, micro-flotation experiments were carried out in addition to surface chemistry studies including zeta potential, contact angle, and bubble-particle attachment time measurements at various ultrasonic power levels and conditioning time. The results showed that, the maximum micro-flotation recovery of 77.5% was obtained with 30 W ultrasound power and 2 min conditioning time. In addition, more negative zeta potential values were obtained with ultrasound as well as higher contact angle and lower bubble-particle attachment time, which indicated the increased hydrophobicity of galena with ultrasound.     

Separation and recovery of Cu and As from copper electrolyte through electrowinning and SO2 reduction

Cu and As were separated and recovered from copper electrolyte by multiple stage electrowinning, reduction with SO₂ and evaporative crystallization. Experimental results showed that when the current density was 200 A/m², the electrolyte temperature was 55 °C, the electrolyte circulation rate was about 10 mL/min and the final Cu concentration was higher than 25.88 g/L, the pure copper cathode was recovered. By adjusting the current density to 100 A/m² and the electrolyte temperature to 65 °C, the removal rate of As was 18.25% when the Cu concentration decreased from 24.69 g/L to 0.42 g/L. After As(V) in Cu-depleted electrolyte was fully reduced to As(III) by SO₂, the resultant solution was subjected to evaporative crystallization, then As₂O₃ was produced, and the recovery rate of As was 59.76%. The cathodic polarization curves demonstrated that both Cu²⁺ concentration and As(V) affect the limiting current of Cu²⁺ deposition.     

Co‐effect of bis(cyclohexanone) oxalyldihydrazone and copper(II) ion on the corrosion of cold rolled steel in 0.5 M hydrochloric acid solution

Effects of bis(cyclohexanone) oxalyldihydrazone (BCO) and copper(II) ion (Cu²⁺) on the corrosion of cold rolled steel (CRS) in 0.5 M hydrochloric acid (HCl) solution were investigated using Tafel polarization curve and electrochemical impedance spectroscopy (EIS) at 20 °C. Results elucidate that the inhibition efficiency increases with increase in BCO concentration, and the addition of 10^?5 M Cu²⁺ significantly enhances the inhibition efficiency of BCO. Polarization curve results elucidate that the single BCO acts as a mixed‐type inhibitor while the combination of Cu²⁺ and BCO acts as cathodic inhibitor. Ultraviolet and visible spectrophotometer (UV–Vis) results show that BCO molecules do not interact with Cu²⁺ and Fe²⁺ in 0.5 M HCl solution. Atomic force microscope (AFM) result indicates that a protective layer forms on CRS surface after immersion in 0.5 M HCl containing BCO in the absence and presence of Cu²⁺. The adsorption of BCO is found to follow the Langmuir adsorption isotherm in the presence and absence of Cu²⁺. The mechanism of typically chemical adsorption is proposed via the value of free energy of adsorption (ΔG) in the presence of BCO and Cu²⁺.     

Adsorption of copper ions on porous ceramsite prepared by diatomite and tungsten residue

In order to realize resource utilization of industrial tungsten residue and treatment of heavy metal wastewater in mining and metallurgical area of south China, a novel ceramsite was prepared with the main raw materials of diatomite and tungsten residue. The adsorption behavior of copper ions in solution on the ceramsite was investigated. Results indicated that the surface of the newly-developed ceramsite was rough and porous. There were lots of pores across the ceramsite from inner to outside. MnFe₂O₄ was one of the main components of the ceramsite. The Cu²⁺ adsorption capacity by the ceramsite reached 9.421 mg/g with copper removal efficiency of 94.21% at 303 K, initial Cu²⁺ concentration of 100 mg/L and dosage of 0.5 g after 300 min adsorption. With increase of ceramsite dosage, the total adsorption amount of Cu²⁺ increased, but the adsorption capacity decreased. The adsorption capacity increased with the increase of solution pH. The isothermal adsorption of Cu²⁺ by the ceramsite fitted the Freundlich model better. The adsorption mainly occurred on a heterogeneous surface, and was a favorable process. The adsorption process closely followed the pseudo-second kinetic equation. In initial stage of wastewater treatment, the adsorption process should be controlled mainly by diffusion, and the removal of Cu²⁺ can be improved by enhancing agitation.     

羧甲基纤维素对层状镁硅酸盐矿物浮选的抑制与分散作用

通过浮选实验、润湿接触角测量和Zeta电位测试,考察滑石、绿泥石和蛇纹石3种层状镁硅酸盐矿物的可浮性及其对金川镍矿中的硫化矿物-黄铁矿浮选的影响,并研究羧甲基纤维素(CMC)对3种层状镁硅酸盐矿物浮选的抑制与分散作用.结果表明;3种镁硅酸盐矿物表面性质与可浮性不同,对硫化矿浮选的影响方式与机理也存在区别:蛇纹石天然可浮性较差,但由于静电作用易与黄铁矿发生异相凝聚,降低黄铁矿的可浮性进而影响其回收率,CMC可通过调整矿物表面电性而起到分散作用;滑石与绿泥石并不影响黄铁矿的可浮性,但由于其天然可浮性相对较好,易进入精矿增加MgO杂质含量,CMC能调整矿物表面润湿性而抑制其浮选.     

Simultaneous determination of trace Cu2+, Cd2+, Ni2+ and Co2+ in zinc electrolytes by oscillopolarographic second derivative waves

Simultaneous determination of impurity metal ions in high concentration zinc solution is very important for zinc hydrometallurgy, and the purpose is to establish a method for determining the trace Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ in zinc electrolytes at the same time using the second derivative waves of single sweep oscillopolarography. Factors affecting the derivative waves of the ions were researched in a medium of dimethylglyoxime (DMG)-sodium citrate-sodium tetraborate. The results indicated that the interferences of a high concentration of Zn²⁺ and most other coexisting ions on the determination can be eliminated; when the Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ are in the ranges of 1×10^?7-3×10^?4, 6×10^?7-2×10^?4, 2×10^?8-1×10^?5 and 1×10^?8-3×10^?5 mol/L, respectively, the relationships between the peak currents of the second derivative waves and the concentrations are linear; the detection limits to determine the Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ are 8×10^?8, 2×10^?7, 6×10^?9 and 4×10^?9 mol/L, respectively. Without any sample pretreatment, the method was used to directly determine the trace Cu²⁺, Cd²⁺, Ni²⁺ and Co²⁺ in actual zinc electrolytes with satisfactory results. The method is simple, sensitive and rapid.