Leaching Behavior of Complex Copper Sulphide Concentrate with Ferric Chloride by Microwave Irradiation

Microwave assisted leaching of complex copper sulphide concentrate with ferric chloride was investigated, and its mechanism was analyzed. The results show that the leaching rate by microwave irradiation heating is much faster than that by conventional heating.

Comparative study on the passivation layers of copper sulphide minerals during bioleaching

The bioleaching of copper sulphide minerals was investigated by using A. ferrooxidans ATF6. The result shows the preferential order of the minerals bioleaching as djurleite〉bomite〉pyritic chalcopyrite〉covellite〉porphyry chalcopyfite. The residues were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. It is indicated that jarosite may not be responsible for hindered disso- lution. The elemental sulfur layer on the surface of pyritic chalcopyrite residues is cracked. The compact surface layer of porphyry chalcopy- rite may strongly hinder copper extraction. X-ray photoelectron spectroscopy （XPS） further confirms that the passivation layers of covellite, pyritic chalcopyrite, and porphyry chalcopyrite are copper-depleted sulphide Cu4S11, S8, and copper-rich iron-deficient polysulphide CtuFe2S9, resoectivelv. The ability of these oassivation layers was found as Cu4Fe2S9〉Cu4S11〉S8〉iarosite.

Interaction effects of flotation reagents for SAG mill reject of copper sulphide ore using response surface methodology

Flotation reagents have a complex behaviour in the beneficiation of base minerals in clayey ores.Interaction effects of reagents on the efficiency of copper flotation for a highly clayey low-grade sulphide ore were investigated using a central composite design.Preliminary results showed that sodium-isopropyl-xanthate(SIPX)and O-isopropyl-N-ethyl-thionocarbamate(IPETC)were found to be the most efficient collectors in the presence of lime as the pH regulator.The effects of dosage of collectors(SIPX and IPETC)and the dosage of methyl-isobutyl-carbonyl(MIBC)as frother on the separation efficiency were evaluated at different pH levels.Based on the analysis of variance(ANOVA),the interaction effects of the collector−pH and collector−frother were significant for the separation efficiency.At the low level of collector dosage,increasing pH from 9 to 11 enhanced copper separation efficiency from 81%to 86%for IPETC and from 77%to 86%for SIPX.Results of ANOVA showed that the maximum copper separation efficiency(88.7%)was obtained at the dosages of 8.6 g/t SIPX,7 g/t IPETC and 20 g/t MIBC at pH 11.Finally,it was concluded that a mixture of SIPX and IPETC collectors was more suitable to treat highly clayey sulphide ores.

Mathematical model for coupled reactive flow and solute transport during heap bioleaching of copper sulfide

Based on the momentum and mass conservation equations, a comprehensive model of heap bioleaching process is developed to investigate the interaction between chemical reactions, solution flow, gas flow, and solute transport within the leaching system. The governing equations are solved numerically using the COMSOL Multiphysics software for the coupled reactive flow and solute transport at micro-scale, meso-scale and macro-scale levels. At or near the surface of ore particle, the acid concentration is relatively higher than that in the central area, while the concentration gradient decreases after 72 d of leaching. The flow simulation between ore particles by combining X-ray CT technology shows that the highest velocity in narrow pore reaches 0.375 m/s. The air velocity within the dump shows that the velocity near the top and side surface is relatively high, which leads to the high oxygen concentration in that area. The coupled heat transfer and liquid flow process shows that the solution can act as an effective remover from the heap, dropping the highest temperature from 60 to 38 ℃. The reagent transfer coupled with solution flow is also analyzed. The results obtained allow us to obtain a better understanding of the fundamental physical phenomenon of the bioleaching process.

Optimization of reagent dosages for copper flotation using statistical technique

The effects of Z11 and AP407 collectors as well as AF65 and AF70 frothers were evaluated in the rougher flotation circuit of the Sungun copper concentrator plant using 2 4 full factorial design.Response functions were produced for both Cu grade and recovery and optimized within the experimental range.The optimum reagent dosages were found to be 12.01 g/t Z11,11 g/t AP407,3 g/t AF65 and 5 g/t AF70 to attain the maximum Cu grade(8.17%).The reagent dosages of 12 g/t Z11,11 g/t AP407,3 g/t AF65 and 15 g/t AF70 produced the maximum Cu recovery(86.44%).The collector distribution demonstrated that the distribution pattern of(32%,32%,20%,16%)can produce the best recovery(87.75%)in comparison to other examined distribution patterns.

Effects of forced aeration on community dynamics of free and attached bacteria in copper sulphide ore bioleaching

Bacterial community dynamics and copper leaching with applied forced aeration were investigated during low-grade copper sulphide bioleaching to obtain better bioleaching efficiency.Results illustrated that appropriate aeration improved bacterial concentrations and leaching efficiencies.The highest bacterial concentration and Cu^(2+)concentration after 14-d leaching were 7.61×10^(7) cells·mL^(−1) and 704.9 mg·L^(−1),respectively,at aeration duration of 4 h·d^(−1).The attached bacteria played a significant role during bioleaching from 1 to 7 d.However,free bacteria dominated the bioleaching processes from 8 to 14 d.This phenomenon was mainly caused by the formation of passivation layer through Fe3+hydrolysis along with bioleaching,which inhibited the contact between the attached bacteria and ore.Meanwhile,16S rDNA analysis verified the effect of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans on the bioleaching process.The results demonstrate the importance of free and attached bacteria in bioleaching.

Mechanochemical sulfidization of a mixed oxide-sulphide copper ore by co-grinding with sulfur and its effect on the flotation efficiency

Mechanochemical sulfidization of a mixed sulfide/oxide copper ore by co-grinding with sulfur and additives including Mg(NO3)2 and Fe(NO3)3 salts and iron,aluminum and magnesium powders was investigated for the first time.Also,the influence of sulfidization during the wet-milling process was examined on the separation efficiency and recovery of copper in detail.The results demonstrated that co-grinding with sulfur solely had the best flotation performance at the value of 0.5 wt.%and it was attributed to the possible existence of S\\O bonding on copper oxides surfaces.In addition,adding magnesium nitrate salt,magnesium powder,iron nitrate salt and aluminum powder as additive associated with 0.5 wt%sulfur into ball milling caused the flotation improvement at the amounts of 0.2 wt%,0.2 wt%,0.5 wt%and 0.5 wt%,respectively.Also,the effect of grinding time and sulfidization pH with 0.5 wt%sulfur solely was determined and pH s of 7.5 to 8.5 gave the best results.The highest recovery(75.76%)and separation efficiency(63.44%)were achieved at pH of 7.5 and 8.5,respectively.

Bioleaching of a kind of alkaline mixed copper oxide and sulphide mineral

We conducted two-stage acidification-bioleaching experiments to probe the feasibility of bioleaching for a kind of mixed alkaline copper oxide and sulphide mineral. We used the uniform design method for data analysis and experimental optimization, with initial pH value, pulp density, inoculation of bacteria and ferrous iron concentration selected as the influential factors. Polynomial regression shows that the four factors sequentially influence the copper recovery by 14.430%, 8.555%, 1.982% and 3.895%. Acid equilibrium in the bioleaching system is mainly influenced by alkaline gangue content, chemical reactions and bacterial activity. A maximal portion of refractory copper extracted reaches 71.08%. The dynamic analysis of copper recovery indicates that bioleaching goes through a lag leaching phase, prime leaching phase and leaching stationary phase corresponding to the growth phases of bacteria. Compared with the predicted value of 80.87%, the confirmatory experiment observes a 78.21% copper recovery under the optimal conditions of pH of 1.5, pulp density of 5%, bacteria inoculation of 30% and initial ferrous iron concentration of 9 g L-1. Results suggest that bioleaching is technically feasible to improving total copper recovery.

Kinetics of the Chlorination of Copper （I） Sulphide by Calcium Chloride in the Presence of Oxygen

The chemism of the chlorination of copper （I） sulphide by calcium chloride in the presence of oxygen has been determined based on the thermodynamic analysis in the Cu2S-CaCl2-O2 system as well as characterization of used raw materials and obtained products. The influence of temperature （from 473 to 773 K）, time （from 2 to 120 min）, oxygen flow （from 20 to 100 L/h） and calcium chloride quantity （from 5 to 40%） on the chlorination degree has been investigated. Kinetic analysis and the activation energy values of 20.89 kJ/mol showed that the chlorination of copper （I） sulphide by calcium chloride in the presence of oxygen is diffusion controlled.

X-Ray Photoelectron Spectroscopic Study on the Synthesis of Copper Sulphide in LB Films( Ⅱ )

The present paper covers the formation process of copper sulphide in copper stearate Langmuir-Blodgett films studied carefully by XPS. The further identification of sulfur species and the examination of its change in the reaction have been made. Also the formation mechanism of sulfur species in the special microenvironment-LB films is discussed.

Directional construction of Cu2S branch arrays for advanced oxygen evolution reaction

Metal sulphide electrocatalyst is considered as one of the most promising low-cost candidates for oxygen evolution reaction(OER).In this work,we report a novel free-standing Cu2S branch array via a facile TiO2-induced electrodeposition-sulfurization method.Interestingly,cross-linked Cu2S nanoflake branch is strongly anchored on the TiO2 backbone forming high-quality Cu2S/TiO2/Cu2S core-branch arrays.The branch formation mechanism is also proposed.As compared to the pure Cu2S nanowire arrays,the asprepared Cu2S/TiO2/Cu2S core-branch arrays show much better alkaline OER performance with lower overpotential(284 mV at 10 mA cm^-2)and smaller Tafel slope(72 dec-1)as well as enhanced longterm durability mainly due to larger exposed area and more active electrocatalytic sites.Our work provides a new way for construction of advanced metal sulphide electrocatalysts for electrochemical energy conversion.

Simulation of solute transportation within porous particles during the bioleaching process

A mathematical model, accounting for the sulfuric acid and ferric ions diffusion and the copper sulfide mineral leaching process, was developed for an ore particle by considering its porous structure. It was simulated with the simulation tool COMSOL Multiphysics. The simulation results show that the highest acid and ferric concentrations near the particle surface are apparent, while the concentrations in the central particle increase slightly as the less-porous ore core with low permeability prevents the oxidation from penetrating. The extraction of the mineral near the particle surface is the maximum, mainly because of ample sulfuric acid, ferric ions, bacteria, and oxygen available for the leaching process. Because of low oxidation concentration in the central part of the particle, the reaction rate and copper sulphide conversion are small. The simulation shows good agreement with the experimental results.

Structural and thermoelectric properties of copper sulphide powders

Over the past few years, Cu-based materials have been intensively studied focusing on their structural and thermoelectric properties. In this work, copper sulphide powders were synthesized by the sol-gel method. The chemical composition and the morphological properties of the obtained samples were analyzed by X-ray diffraction, differential thermal analysis, and scanning electron microscopy. It is shown that the decomposition from one phase to another can be obtained by annealing. The electrical resistivity and the crystallite size were found to be strongly affected by the phase transition. Thermoelectric analyses showed that the digenite phase exhibits the highest power factor at room temperature. The Seebeck coefficient of the compound Cu1.8S shows a pronounced peak at the γ-β transition temperature. This behavior was statistically explained in terms of a dramatic increase in the disorder in the atoms-carriers ensemble.