Sphalerite Surface Research Articles

Surface chemistry investigation of froth flotation products of lead-zinc sulfide ore using ToF-SIMS and multivariate analysis

In complex flotation circuits of lead-zinc sulfide ore, selective adsorption of flotation reagents (e.g., collectors, depressants, and regulators) and solution components onto different mineral surfaces are involved. This work aimed to study the surface chemistry differences between minerals in lead concentrate and those in tailings by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and multivariate analysis to understand the flotation behavior of minerals. Specifically, multivariate curve resolution-alternating least squares (MCR-ALS) and principal component analysis (PCA) were used to process ToF-SIMS image datasets of flotation products to enhance mineral identification. The results show that MCR-ALS was more successful than PCA in identifying minerals of ToF-SIMS images from flotation products. Further PCA of the spectra obtained from the specific mineral surfaces in the lead concentrate and tailings revealed surface chemistry reasons for the poor mineral separation. The main finding of this study was that the adsorption of lead ions onto the surfaces of sphalerite, pyrite, calcite, and quartz was an important reason for the failed separation of these minerals from galena in high-alkaline lime systems. The surface chemical evidence provided by this study helps to better understand the selective separation mechanism of lead-zinc sulfide ores.

Sorption of aqueous amino acid species on sulphidic mineral surfaces—DFT study and insights on biosourced‐reagent mineral flotation

AbstractThe interaction between the 20 natural amino acids and the surfaces of sphalerite, pyrite, and chalcopyrite was examined in the light of density functional theory (DFT) simulations. The electronic properties of the active functional groups and the equilibrium geometries of the sorbed amino acid species were characterized as a function the 65 species resulting from their (de)protonations. Covalent bonds are predicted between the surface metallic atoms and the carboxyl groups and, though to a lesser extent, with the side and main amino groups. Chemisorption as a determining factor in the uptake of amino acid species was assessed in terms of sorption affinities for the mineral surfaces. The largest affinities result from the carboxyl groups of the deprotonated species at intermediate pH, whereas the fully protonated amino acids in acidic media predict the lowest affinities. Affinity of amino acids towards the mineral surfaces followed the trend: pyrite >> chalcopyrite > sphalerite with speciation‐dependent decreasing sequence: ∼2.5 < pH < ∼9.5; pH > ∼9.5; pH < ∼2.5. By targeting the most suitable amino acid building blocks in bio‐sourced collectors, either high collecting powers or superior selectivities can be aimed at depending on pH for improved separation of sulphidic minerals in flotation processes.

Adding cationic guar gum after collector: A novel investigation in flotation separation of galena from sphalerite

In this study, the effect of cationic guar gum in the flotation separation of galena from sphalerite when diethyldithiocarbamate acted as galena collector was investigated, mainly through flotation tests and ToF-SIMS analysis. The flotation results showed that the cationic guar gum could selectively depress the sphalerite flotation and enhance the preferential flotation of galena only when it was added after collector diethyldithiocarbamate. The ToF-SIMS analysis found that addition of cationic guar gum after diethyldithiocarbamate exhibited no effect on the collector adsorption on galena surface but could selectively inhibit the collector coverage on sphalerite surface, and further result in the floatability difference.

Cu2+-catalyzed mechanism in oxygen-pressure acid leaching of artificial sphalerite

The potential autoclave was used to study the catalytic mechanism of Cu2+ during the oxygen pressure leaching process of artificial sphalerite. By studying the potential change of the system at different temperatures and the SEM-EDS difference of the leaching residues, it was found that in the temperature range of 363–423 K, the internal Cu2+ formed a CuS deposit on the surface of sphalerite, which hindered the leaching reaction, resulting in a zinc leaching rate of only 51.04%. When the temperature exceeds 463 K, the system potential increases steadily. The increase in temperature leads to the dissolution of the CuS, which is beneficial to the circulation catalysis of Cu2+. At this time, the leaching rate of Zn exceeds 95%. In addition, the leaching kinetics equations at 363–423 and 423–483 K were established. The activation energy of zinc leaching at 363–423 and 423–483 K is 38.66 and 36.25 kJ/mol, respectively, and the leaching process is controlled by surface chemical reactions.

Effect of surface oxidation on the depression of sphalerite by locust bean gum

To study the role of surface oxides in the adsorption of polysaccharide depressant on sulfides, the depression behavior of locust bean gum on sphalerite flotation in the presence of H2O2 was studied. The flotation results indicated that locust bean gum has depression effect on sphalerite but the reagent dosage needed is large. The addition of H2O2 can strength the depression effect of locust bean gum as H2O2 can increase the adsorption amount of locust bean gum on sphalerite greatly. The XPS analysis results illustrated that the locust bean gum adsorbed on sphalerite surface through chemical interaction with the oxides that formed on sphalerite surface. More oxides formed on sphalerite surface after the addition of H2O2 and this is the main reason why oxidizer can increase the depression effect of locust bean gum.

Activation mechanism of lead ions in the flotation of sphalerite depressed with zinc sulfate

Sphalerite is commonly associated with other metal-sulfide minerals, and is usually depressed with zinc sulfate (ZnSO4) prior to the preferential flotation of other sulfide minerals with excellent floatability. In subsequent processing, ZnSO4-depressed sphalerite activation is necessary for the maximum recovery of zinc resources. In this work, lead nitrate (Pb(NO3)2) was used to activate the depressed sphalerite surface by zinc sulfate (ZnSO4). The lead-ion activation mechanism was studied in the flotation of ZnSO4-depressed sphalerite through microflotation tests, zeta-potential experiments, local electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Floatability of ZnSO4-depressed sphalerite after treatment with Pb(NO3)2 improved significantly and the maximum recovery reached 96.4%. The zeta potential, local electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy outcome displayed lead species could adsorb on the Zn-depressed sphalerite surface as Pb2+ and Pb(OH)+ and form –Zn–O–Pb complexes, which enhanced the active sites at mineral surfaces significantly, promoted xanthate species attachment to the depressed minerals surface, and enhanced mineral-particle hydrophobicity. The adsorption layer of activated products on the ZnSO4-depressed samples surface was represented by ToF-SIMS, which illuminated its activation mechanism further.

Effect of a Small Amount of Iron Impurity in Sphalerite on Xanthate Adsorption and Flotation Behavior

Through industrial testing at the Huize lead-zinc mine, it was found that the floatability of sphalerite varied greatly with the iron impurity content. Three kinds of Huize sphalerites with iron contents of 2.30 wt.%, 3.20 wt.% and 4.66 wt.%, were used to study the influence of small amounts of iron impurity in the sphalerite on xanthate adsorption and flotation behavior. The flotation experiments showed that the flotation recovery increased with the increase in iron impurity content. Fourier Transform infrared spectroscopy (FTIR) and Ultraviolet–visible (UV-VIS) spectra showed that the adsorbed products of xanthate on the surface of three kinds of sphalerite were metal xanthate. The adsorption capacity measurements showed that the saturation absorption of xanthate on sphalerite increased with the increase in iron impurity content. The cyclic voltammetry curve and Tafel curve showed that with the increase in iron impurity content, sphalerite was more easily oxidized and the adsorption rate of xanthate on the surface of sphalerite increased obviously. To summarize, a small amount of iron impurity was beneficial to the recovery of sphalerite.

Surface chemistry of Pb-activated sphalerite

Activation of sphalerite flotation by lead ions (Pb) is an important aspect of selective separation of sphalerite and galena, but its molecular mechanism remains poorly understood. In this paper, the surface chemistry of sphalerite in the Pb activation process at pHs 4 and 9 was investigated using inductively coupled plasma-atomic mission spectrometry (ICP-AES), time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). ICP results showed that the ion exchange ratio of Pb:Zn is not 1:1 during the activation at both acidic and alkaline pHs, indicating multiple adsorption mechanisms. ToF-SIMS results showed that three kinds of Pb secondary ion fragments, i.e., Pb+, PbOH+ and PbS+ were determined on the Pb-activated sphalerite surface, which provided direct evidence for the possible mixed activation mechanisms. In addition, ToF-SIMS depth profile results exposed that the Pb species not only distribute on the outermost sphalerite surface but also diffuse into the crystal structure of the mineral. XPS studies revealed the formation of PbS and PbSO3 at pH 4 and PbS, PbO with Pb(OH)2 at pH 9. It was also revealed that Pb uptake was higher at pH 9 than pH 4. Furthermore, XPS depth profile results showed the formation of PbSO3, Pb(OH)2 and PbO have not exceeded 2 nm depth, representing chemical bonding on the mineral surface, while PbS diffusion took place down to around 10 nm depth through ion exchange mechanism. All these details have established that the activation of sphalerite by Pb involves a mixed activation mechanism of ion exchange and Pb-oxide as activating sites. The PbS species formed by the ion exchange not only distribute on the outermost layer of sphalerite surface but also penetrate the surface and diffuse into the bulkphase of sphalerite.

Investigation of the interfacial adsorption mechanisms of 2-hydroxyethyl dibutyldithiocarbamate surfactant on galena and sphalerite

To enhance the selective separation of galena and sphalerite from their mixture minerals, 2-hydroxyethyl dibutyldithiocarbamate (HEBTC) surfactant was synthesized and its first applications on the flotation of galena and sphalerite were studied. The interfacial adsorption mechanisms of HEBTC on galena and sphalerite surfaces were also investigated by wettability measurements, FTIR measurements, XPS analyses and adsorption experiments. Compared with the two common collectors, sodium isobutyl xanthate (SIBX) and O-isopropyl-N-ethyl thionocarbamate (IPETC), HEBTC exhibited better selectivity for galena against sphalerite. The separation of galena from sphalerite can be achieved by using 4 × 10−4 mol·L−1 HEBTC as flotation collector. The results of the adsorption mechanisms demonstrated that HEBTC could improve the hydrophobicity of galena surface by chemisorption, but had weak effect on the hydrophobicity of sphalerite with no obvious chemical reaction. Adsorption kinetics and adsorption isotherm experiments revealed that the adsorption of HEBTC on galena surface could be well described by the Pseudo-second-order model and Langmuir model, respectively. The adsorption of HEBTC on galena surface was an endothermic and spontaneous process.

Flotation separation behavior of chalcopyrite and sphalerite in the presence of locust bean gum

Locust bean gum was tested as a potential selective depressant in the flotation separation of chalcopyrite and sphalerite using potassium butyl xanthate (PBX) as collector. In single mineral flotation, locust bean gum depressed sphalerite, while chalcopyrite was floatable. This illustrated that locust bean gum could be used to separate chalcopyrite from sphalerite. Adsorption tests and zeta potential measurements indicated that locust bean gum can adsorb on the surfaces of both chalcopyrite and sphalerite, but the adsorption amount on sphalerite was higher than that on chalcopyrite. XPS analysis showed that locust bean gum adsorbed on the sphalerite surface through chemical interaction between ZnOH or ZnO on the sphalerite surface and hydroxyl groups of locust bean gum. Locust bean gum adsorbed more easily on the sphalerite surface, perhaps due to sphalerite being easier to oxidize than chalcopyrite.

Study on the Interaction between Galena and Sphalerite During Grinding Based on the Migration of Surface Components.

In Pb–Zn ore flotation, unintentional activation of sphalerite often leads to difficult separation of Pb and Zn minerals, during which grinding plays a key role in unintentional activation. Therefore, the aim of this study was to evaluate the surface component changes of two different mineral particles and to propose the interaction between galena and sphalerite during mixed grinding using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show that after mixed grinding of the galena and sphalerite, the Pb content on the sphalerite surface increased with the decrease of Zn and Fe contents on the sphalerite surface. The lead ions from galena were obviously absorbed onto the sphalerite surface, while the zinc and iron ions from sphalerite were not obviously migrated to the galena surface. Principal component analysis (PCA) of a dataset composed of 206 positive ion peaks of galena and sphalerite indicates that the surface components of galena and sphalerite migrated from either side to different degrees. This study successfully identified an important factor for unintentional activation of lead and zinc minerals during flotation: homogenization of surface components of different minerals during grinding.

Homogenization phenomena of surface components of chalcopyrite and sphalerite during grinding processing

The selective flotation separation of chalcopyrite and sphalerite has been a general industrial challenge. In this study, we studied the occurrence of surface homogenization of chalcopyrite and sphalerite during grinding by using time of flight secondary ion mass spectrometry analysis (ToF-SIMS), principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The results showed that the surface compositions of chalcopyrite and sphalerite became more similar after simultaneous grinding. The copper ions that released from the chalcopyrite were more easily adsorbed on to the sphalerite surface than iron ions, conversely, the zinc ions that dissolved from the sphalerite were poorly adsorbed by the chalcopyrite surface. PCA and OPLS-DA were used to confirm the differences in surface compositions of chalcopyrite and sphalerite, and the results showed that after simultaneous grinding, the sphalerite surface compositions were converted to chalcopyrite, and the surface compositions of chalcopyrite also changed.

Effect of copper ions on surface properties of ZnSO4-depressed sphalerite and its response to flotation

The activation mechanism of copper sulfate (CuSO4) for sphalerite surfaces depressed with zinc sulfate (ZnSO4) and their interactions were investigated through microflotation experiments, zeta-potential determination, X-ray photoelectron spectroscopy (XPS), xanthate adsorption experiments, time-of-flight secondary-ion mass spectrometry (TOF-SIMS) and local electrochemical impedance spectroscopy (LEIS). The microflotation experimental results indicated that addition of ZnSO4 decreased sphalerite recovery and that CuSO4 can activate sphalerite depressed with ZnSO4 during flotation. The highest negativity of the zeta potential was achieved after adding xanthate + ZnSO4 + CuSO4, indicating that the addition of copper ions can improve adsorption of the collector on depressed sphalerite surfaces. XPS was used to identify the mechanisms of the interactions of ZnSO4 and CuSO4 with the sphalerite surface. Xanthate adsorption experiments showed that the xanthate adsorption capacity increased greatly after treatment of depressed sphalerite with copper ions. TOF-SIMS indicated that copper ions were adsorbed on the surface of the depressed sphalerite. LEIS analysis showed that, copper ion can replaces zinc ion on mineral surface. These results show a sphalerite surface depressed with ZnSO4 can be activated by copper ions, thereby increasing its hydrophobicity and floatability.

Synthesis, flotation performance and adsorption mechanism of 3-(ethylamino)-N-phenyl-3-thioxopropanamide onto galena/sphalerite surfaces

In this paper, a novel β-Oxo thioamide surfactant 3-(ethylamino)-N-phenyl-3-thioxopropanamide (EAPhTXPA) was synthesized and first used as flotation collector for galena and sphalerite. The results of micro-flotation tests showed that EAPhTXPA possessed not only stronger collecting ability but also better selectivity to galena against sphalerite than traditional sulfide collector sodium isobutyl xanthate (SIBX). Adsorption tests indicated that EAPhTXPA could adsorb onto galena surfaces more easily than SIBX, while the adsorption affinity of EAPhTXPA to sphalerite was weaker than that of SIBX. The results of FTIR and XPS spectra demonstrated that there was no chemical bond or new chemical state appeared on sphalerite surfaces after treatment by EAPhTXPA, while Pb-EAPhTXPA complexes were formed on galena surfaces by reaction of EAPhTXPA’s C(S), C(O) and NH groups with surface Pb atoms to build PbS, PbO and PbN bonds. DFT calculations further gave an evidence that the dominated interaction between sphalerite and EAPhTXPA was probably van der Walls forces, and EAPhTXPA reacted with galena by the formation of PbS, PbO and PbN bonds.

DFT study the adsorption of ethyl xanthate on the S-site of Cu-activated sphalerite (1 1 0) surface in the presence of water molecule

Abstract The research investigates whether the copper activation of sphalerite can result in the adsorption of xanthate on the S-site of sphalerite surface at the atomic level. The adsorption of ethyl xanthate (EX) molecule on the un-activated and Cu-activated sphalerite (1 1 0) surface in the presence of water molecule was conducted by using the density functional theory (DFT). The DFT results showed that there was little chemical interaction between EX and S atom of the un-activated sphalerite (1 1 0) surface. However, the copper activation of sphalerite changed the properties of S atom by inducing a strong covalent interaction between EX and the S atom. The EX molecule did not only adsorbed on the metal atom, but also adsorbed on the S-site.

Mechanism Study of Xanthate Adsorption on Sphalerite/Marmatite Surfaces by ToF-SIMS Analysis and Flotation

In this work, the active sites and species involved in xanthate adsorption on sphalerite/marmatite surfaces were studied using adsorption capacity measurements, single mineral flotation, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis. The effects of Fe concentration on the xanthate adsorption capacity, Cu activation, and the flotation response of sphalerite/marmatite were determined. A discovery was that xanthate can interact with Fe atoms in the crystal of sphalerite/marmatite, as well as with Zn and Cu on the surface. We detected C2S2− fragment ions from dixanthogen, and dixanthogen may have been adsorbed on the surface of marmatite. The amounts of Cu and copper xanthate adsorbed on the marmatite surface were lower than those on the sphalerite surface, because Fe occupies Cu and Zn exchange sites. These results help to address the long-standing controversy regarding the products and mechanisms of xanthate adsorption on Fe-bearing sphalerite surfaces.

Influence of ZnS wurtzite–sphalerite junctions on ZnOCore-ZnSShell-1D photocatalysts for H2 production

The ZnOcore-ZnSshell like nanoparticles have been prepared in ethanol by the hydrothermal method using different sulfur loading. These kind of nanomaterials were characterized by X-ray diffraction, Scanning and Transmission Electron Microscopy, Photoluminescence, and the surface area was determined by BET method. Photocatalytic H2 production from ethanol in aqueous solution has been studied at ambient temperature under UV irradiation and molecular simulation was also included. The optimum ZnS contents for H2 production, from ethanol aqueous solution, on the ZnOcore-ZnSshell like nanoparticles were 50 mol% of S loading on ZnO-1D. The H2 yield was about 1200–1500 μmol/hg obtained under prolonged time irradiation. Experimental results showed that the photocatalytic H2 production could be enhanced remarkably by depositing a suitable amount of ZnS on ZnO-1D surface. Based on our simulation results, we suggest that the water and ethanol were adsorbed preferentially on the surface of sphalerite than on the wurtzite structure and H2 is released from the sphalerite structure.

Sphalerite bioleaching comparison in shake flasks and percolators

Bioleaching experiments with a mixed Acidithiobacillus-culture were carried out in shake flasks as well as in column percolators with crushed and sieved sphalerite-rich ore from a former mine in the German Harz Mountains. Efficient sphalerite dissolution in the bioleaching assays was observed in contrast to the chemical leaching experiments. The redox potential was higher in the bioleaching than in the chemical control assays. Total cell counting and most-probable-number cultivation congruently exhibited high cell numbers at the end of the bioleaching experiments of about one month. The kinetics of sphalerite bioleaching showed a linear increase of the zinc concentration in solution with time and exhibited similar sphalerite surface related reaction rates for percolators and shake flasks indicating that the overall sphalerite dissolution rate was mainly controlled by the total mineral surface. Maximal zinc bioleaching efficiency with up to 10 g/L zinc in the pregnant leach solution was achieved at a low starting pH 1.8 and addition of 2 g/L ferrous iron. Besides zinc, up to 1 mg/L gallium as trace element was extracted. Electrochemical analysis of leaching residues was performed as well to analyze potential surface related limitations for metal sulfide dissolution.

Correlation between the hydrogen peroxide formed during grinding and the oxidized species present on the surface of sphalerite

Flotation separation of sphalerite from chalcopyrite is significantly affected by the oxidation of metal species on the surface of sphalerite, partially contributed by production of the reactive oxygen species hydrogen peroxide (H2O2) and hydroxyl radicals (OH) if any during wet grinding of a complex sulphide ore. This research experimentally measures the production of H2O2 during grinding of a Cu/Zn ore from Mine Matagami (Canada) with different grinding time and in different grinding environments. Results reveal that H2O2 was formed spontaneously when the ore was ground in the ball mill. The amount of H2O2 generated increases with an increased pyrite load to the ball mill. Grinding with mild steel shows a lower measurable concentration of H2O2 in slurry relative to grinding with stainless steel balls. This appears to be in conflict with other researchers. It is found that Fe ions released from mild steel balls benefits the conversion from H2O2 to (OH), but in the current H2O2 detection program hydroxyl radicals (OH) could not be measured. Surface analysis of mineral grains from the mill discharge samples has identified an obvious correlation between H2O2 detected in the pulp and sphalerite surface oxidation. Lower pulp H2O2 concentrations possibly correspond to the conversion of H2O2 to OH which may be linked to a more pronounced sphalerite surface oxidation.

Density functional theory study of cyanide adsorption on the sphalerite (1 1 0) surface

Cyanidation tailings in gold plants often contain lots of sphalerites that are difficult to recycle by flotation because of the strongly depressive effect of the residual cyanide. To reveal the depression mechanism of cyanide on sphalerite, the adsorption of isolated cyanide molecule (CN) at different coverages on the sphalerite (1 1 0) surface were studied by means of density functional theory. The calculated results show that the adsorption energy of per CN molecule drops as the increase of adsorbed CN molecule coverage, indicating that the adsorption structure becomes more thermodynamically stable. Cyanide molecule adsorption on sphalrite (1 1 0) surface prior occurs on the atop site of surface Zn atom, in which the Zn 3d orbital donates electrons to the 2p orbital of C forming a d-p back donating bond, leading to the production of hydrophilic zinc cyanide complexes that serve as strong obstacles to the flotation recovery of sphalerite in cyanidation tailings. Electron transfer from mineral surface to the adsorbed CN molecules takes place during the process of CN adsorption, and the surface atoms lose more electrons when the coverage of adsorbed CN molecules is high, weakening the reactive activity of Zn and S atoms on the sphalerite (1 1 0) surface.