Shuming Wen

Adsorption and activation of copper ions on chalcopyrite surfaces: A new viewpoint of self-activation

The adsorption behaviors of copper ions on chalcopyrite surfaces were investigated based on zeta potential measurements, X-ray photoelectron spectroscopy, copper ion adsorption experiments, first-principles calculations, and Hallimond tube cell flotation experiments. The results show that copper ions activate the chalcopyrite as a result of the interactions between copper ions and sulfur on the chalcopyrite surface. This adsorption increases the flotation rate under certain conditions, and this is beneficial for the flotation of chalcopyrite. The copper ions in the flotation pulp are mainly derived from surface oxidation dissolution and the release of fluid inclusions, and these effects enable chalcopyrite to be activated.

A novel method for improving cerussite sulfidization

Evaluation of flotation behavior, solution measurements, and surface analyses were performed to investigate the effects of chloride ion addition on the sulfidization of cerussite in this study. Micro-flotation tests indicate that the addition of chloride ions prior to sulfidization can significantly increase the flotation recovery of cerussite, which is attributed to the formation of more lead sulfide species on the mineral surface. Solution measurement results suggest that the addition of chloride ions prior to sulfidization induces the transformation of more sulfide ions from pulp solution onto the mineral surface by the formation of more lead sulfide species. X-ray diffraction and energy-dispersive spectroscopy indicate that more lead sulfide species form on the mineral surface when chloride ions are added prior to sulfidization. These results demonstrate that the addition of chloride ions prior to sulfidization can significantly improve the sulfidization of cerussite, thereby enhancing the flotation performance.

Extracting copper from copper oxide ore by a zwitterionic reagent and dissolution kinetics

Sulfamic acid (SA), which possesses a zwitterionic structure, was applied as a leaching reagent for the first time for extracting copper from copper oxide ore. The effects of reaction time, temperature, particle size, reagent concentration, and stirring speed on this leaching were studied. The dissolution kinetics of malachite was illustrated with a three-dimensional diffusion model. A novel leaching effect of SA on malachite was eventually demonstrated. The leaching rate increased with decreasing particle size and increasing concentration, reaction temperature and stirring speed. The activation energy for SA leaching malachite was 33.23 kJ/mol. Furthermore, the effectiveness of SA as a new reagent for extracting copper from copper oxide ore was confirmed by experiment. This approach may provide a solution suitable for subsequent electrowinning. In addition, results reported herein may provide basic data that enable the leaching of other carbonate minerals of copper, zinc, cobalt and so on in an SA system.

Dynamic Simulation of the Thermal Decomposition of Pyrite Under Vacuum

The ultrasoft pseudopotential plane wave method is applied to dynamic simulation of the thermal decomposition mechanism of FeS2 under vacuum. The FeS2 (100), (111), and (210) surface relaxation and the geometric and electronic structure of the reactants and products are calculated. The results indicate that FeS2 (100) is the most preferred surface to dissociate and also the most common cleavage surface. The thermal decomposition mechanism of FeS2 is explained by dynamic simulation on a micro stratum: in general, the S-Fe bond gradually elongated until it fractured, the S-S bond strengthened gradually, the S-Fe bond was cleaved to form S, the force is relatively weaker between different layers, and thermal decomposition occurred easily between the layers. Simultaneously, the intermediate products, such as FexSy, were formed. Evidence of Fe pyrolysis into Fe metal was not found, and the intermediate products decomposed further. The contributions of the p and d orbitals of Fe increased, whereas that of the s orbital decreased. The contributions of the s and p orbitals of S decreased. The results obtained from FeS2 thermal decomposition experiments under vacuum and differential thermal analysis—thermogravimetry are consistent with the results of calculation and simulation.

Leaching kinetics of cerussite using a new complexation reaction reagent

In this paper, an attractive organic complexation reaction reagent with lead ions was developed for lead extraction from cerussite. The leaching kinetics of cerussite was investigated using 5-sulfosalicylic acid solution as a lixiviant. The effects of several experimental parameters on the leaching of cerussite were investigated, and a kinetic model was developed to represent the relationship. The leaching process was controlled by a mixed kinetic model. The results showed that the leaching rate of cerussite increased with an increase in the stirring speed, temperature, and concentration, as well as a decrease in the particle size. The activation energy was found to be 37.07 kJ mol−1. The rate of reaction based on the mixed kinetic model-controlled process could be expressed as [1 − (1 − x)1/3]2 = [k0(SS)6.852(r0)−1.943(C)2.042 exp(−37.07/RT)]t. X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses indicated that a new solid reaction product may be formed.

New influence factor inducing difficulty in selective flotation separation of Cu-Zn mixed sulfide minerals

Selective flotation separation of Cu-Zn mixed sulfides has been proven to be difficult. Thus far, researchers have found no satisfactory way to separate Cu-Zn mixed sulfides by selective flotation, mainly because of the complex surface and interface interaction mechanisms in the flotation solution. Undesired activation occurs between copper ions and the sphalerite surfaces. In addition to recycled water and mineral dissolution, ancient fluids in the minerals are observed to be a new source of metal ions. In this study, significant amounts of ancient fluids were found to exist in Cu-Zn sulfide and gangue minerals, mostly as gas-liquid fluid inclusions. The concentration of copper ions released from the ancient fluids reached 1.02 × 10−6 mol/L, whereas, in the cases of sphalerite and quartz, this concentration was 0.62 × 10−6 mol/L and 0.44 × 10−6 mol/L, respectively. As a result, the ancient fluid is a significant source of copper ions compared to mineral dissolution under the same experimental conditions, which promotes the unwanted activation of sphalerite. Therefore, the ancient fluid is considered to be a new factor that affects the selective flotation separation of Cu-Zn mixed sulfide ores.

Theory analysis and vestigial information of surface relaxation of natural chalcopyrite mineral crystal

Abstract X-ray diffraction was used to measure the unit cell parameters of chalcopyrite crystal. The results showed that the chalcopyrite crystal is perfect, and the arrangement of its atoms is regular. A qualitative analysis of molecular mechanics showed that surface relaxation causes the chalcopyrite surface to be sulfur enriched. Atomic force microscope (AFM) was used to obtain both a microscopic three-dimensional topological map of chalcopyrite surface and a two-dimensional topological map of its electron cloud. The AFM results revealed that the horizontal and longitudinal arrangements of atoms on the chalcopyrite surface change dramatically compared with those in the interior of the crystal. Longitudinal shifts occur among the copper, iron and sulfur atoms relative to their original positions, namely, surface relaxation occurs, causing sulfur atoms to appear on the outermost surface. Horizontally, AFM spectrum showed that the interatomic distance is irregular and that a reconstruction occurs on the surface. One result of this reconstruction is that two or more atoms can be positioned sufficiently close so as to form atomic aggregates. The lattice properties of these models were calculated based on DFT theory and compared with the experimental results and those of previous theoretical works. On analyzing the results, the atomic arrangement on the (001) surface of chalcopyrite is observed to become irregular, S atoms move outward along the Z-axis, and the lengths of Cu—S and Fe—S bonds are enlarged after geometry optimization because of the surface relaxation and reconstruction. The sulfur-rich surface and irregular atomic aggregates caused by the surface relaxation and reconstruction greatly influence the bulk flotation properties of chalcopyrite.

Dissolution regularities of smithsonite in methane sulfonic acid

Methane sulfonic acid (MSA) was proposed as a clean and efficient leaching agent to extract zinc from smithsonite. Experimental variables such as acid concentration, reaction temperature, particle size, and stirring speed were considered. Results indicated that zinc leaching fraction increased with increased MSA concentration, reaction temperature, stirring speed, and decreasing particle size. The dissolution kinetics of smithsonite in MSA solutions was investigated with respect to the corresponding experimental data and kinetics was analyzed using a new variant of the shrinking core model, in which both interfacial transfer and diffusion across the product layer affected the dissolution rate. The apparent activation energy of this process was determined to be 32.66 kJ/mol, and a semi-empirical rate equation was obtained to describe the process.

Investigation of dissolution kinetics of zinc from smithsonite in 5-sulphosalicylic acid solution

Abstract The dissolution kinetics of smithsonite was investigated using 5-sulphosalicylic acid solution as leaching agent. The effects of several experimental parameters on the dissolution of smithsonite were investigated and a kinetic model was developed to represent these relationships. The dissolution rate increased with increasing solution temperature, concentration and stirring speed as well as with decreasing particle size. The dissolution was controlled by the shrinking core model for the surface chemical reaction. The activation energy of the dissolution process was determined to be 44·42 kJ mol−1. The rate of the reaction based on shrinking core model can be expressed by a semi-empirical equation as: 1–(1–x)1/3 = [k0(C)0·692(r0)−0·946(SS)1·250exp(–44·42/RT)]t. 5-Sulphosalicylic acid solution can therefore be used as an effective leaching agent for zinc extraction from smithsonite.

Process Optimization and Reaction Mechanism of Removing Copper From an Fe-Rich Pyrite Cinder Using Chlorination Roasting

The aim is to remove copper from a pyrite cinder by optimzing the chlorination roasting process using response surface methodology (RSM) and the reaction mechanism of chlorination roasting based on thermodynamic calculation was discussed. A quadratic model was suggested by RSM to correlate the key parameters, namely, dosage of chlorinating agent, roasting temperature and roasting time to the copper volatilization ratio. The results indicate that the model is well consistent with the experimental data at a correlation coefficient (R2) of 0.95, and the dosage of chlorinating agent and roasting temperature both have significant effects on the copper volatilization ratio. However, a roasting temperature exceeding 1170 °C decreases the volatilization ratio. The optimum condtions for removing copper from the cinder were identified as chlorinating agent dosage at 5%, roasting temperature at 1155.10 °C and roasting time of 10 min; under such a condition, a copper volatilization ratio of 95.16% was achieved from the cinder. Thermodynamic calculation shows that SiO2 in the pellet plays a key role in the chlorine release from calcium chloride, and the chlorine release reactions cannot occur without it.