Electrochemistry and DFT study of galvanic interaction on the surface of monoclinic pyrrhotite(001)and galena(100)

The electrochemical interaction between galena and monoclinic pyrrhotite was investigated to examine its impact on the physical and chemical properties of the mineral micro-surface.This investigation employed techniques such as electrochemistry,metal ion stripping,X-ray photoelectron spectroscopy,and quantum chemistry.The electrochemical test results demonstrate that the galena surface in the electro-couple system exhibits a lower electrostatic potential and higher electrochemical activity compared to the monoclinic pyrrhotite surface,rendering it more susceptible to oxidation dissolution.Monoclinic pyrrhotite significantly amplifies the corrosion rate of the galena surface.Mulliken charge population calculations indicate that electrons are consistently transferred from galena to monoclinic pyrrhotite,with the number of electron transfers on the mineral surface increasing as the interaction distance decreases.The analysis of state density revealed a shift in the surface state density of galena towards lower energy levels,resulting in decreased reactivity and increased difficulty for the reagent to adsorb onto the mineral surface.Conversely,monoclinic pyrrhotite exhibited an opposite trend.The X-ray photoelectron spectroscopy(XPS)test results indicate that galvanic interaction leads to the formation of hydrophilic substances,PbS_(x)O_(y) and Pb(OH)_(2),on the surface of galena.Additionally,the surface of monoclinic pyrrhotite not only adsorbs Pb^(2+)but also undergoes S^(0) formation,thereby augmenting its hydrophobic nature.

Ferric ion-triggered surface oxidation of galena for efficient chalcopyrite-galena separation

The efficient separation of chalcopyrite(CuFeS2)and galena(PbS)is essential for optimal resource utilization.However,find-ing a selective depressant that is environmentally friendly and cost effective remains a challenge.Through various techniques,such as mi-croflotation tests,Fourier transform infrared spectroscopy,scanning electron microscopy(SEM)observation,X-ray photoelectron spec-troscopy(XPS),and Raman spectroscopy measurements,this study explored the use of ferric ions(Fe^(3+))as a selective depressant for ga-lena.The results of flotation tests revealed the impressive selective inhibition capabilities of Fe^(3+)when used alone.Surface analysis showed that Fe^(3+)significantly reduced the adsorption of isopropyl ethyl thionocarbamate(IPETC)on the galena surface while having a minimal impact on chalcopyrite.Further analysis using SEM,XPS,and Raman spectra revealed that Fe^(3+)can oxidize lead sulfide to form compact lead sulfate nanoparticles on the galena surface,effectively depressing IPETC adsorption and increasing surface hydrophilicity.These findings provide a promising solution for the efficient and environmentally responsible separation of chalcopyrite and galena.

Flotation separation of chalcopyrite from galena by sodium humate and ammonium persulfate

The flotabilities of chalcopyrite and galena with sodium humate（HA） and ammonium persulfate（APS） as the depressant were studied by flotation test, adsorption measurement and infrared spectroscopic analysis. Single mineral flotation test shows that the slurry oxidation environment and the proper oxidation of galena surface are prerequisites for the depression of galena by sodium humate. The closed-circuit flotation test of copper/lead bulk concentrate shows that the grade and recovery of Cu reach 30.47% and 89.16% respectively and those of Pb reach 2.06% and1.58% respectively in copper concentrate, and the grade and recovery of Pb reach 50.34% and 98.42% and those of Cu reach 1.45% and 10.84% respectively in lead concentrate with HA and APS. The selective depression effect of HA and APS is more obvious than that of potassium dichromate. The results of FTIR analysis and adsorption measurements indicate that the adsorption of sodium humate on the fresh surface of galena is negligible, while after oxidation, sodium humate can be chemically adsorbed on the surface of galena. According to the theory of solubility product, the sodium humate can display the oxidation product PbSO_4, after then, adsorb on the surface of lead chemically to produce inhibitory effect. Thus, it can be seen that the combination of HA and APS is an efficient non-toxic reagent to achieve cleaning separation copper/lead bulk concentrate by flotation. The combination of HA and APS is an efficient non-toxic reagent to achieve cleaning for copper/lead bulk concentrate by flotation.

Microthermokinetic study of xanthate adsorption on impurity-doped galena

Six kinds of galena with different impurities were synthesized and the effects of impurities on the floatability of galena were investigated. The thermodynamic and kinetic parameters on the galena surface were measured using microcalorimetry, and the adsorption configuration and energy of butyl xanthate on the surfaces of galena with different impurities were simulated by density functional theory. Flotation experiments showed that Ag and Bi significantly promoted the recovery of galena, while Zn, Sb, Mn, and Cu reduced the recovery of the flotation. Microthermokinetic results indicated that the absolute value of xanthate adsorption heat was directly proportional to the flotation recovery of galena. Adsorption heat and reaction rate coefficients of xanthate on galena containing Ag or Bi were larger than those on pure galena, but smaller on galena containing Cu or Sb. Additionally, the relationship between the heat of unsaturated adsorption of xanthate and the adsorption energy of impurity atom on galena surface was investigated.

Selective depression of galena and chalcopyrite by O,O-bis(2,3-dihydroxypropyl) dithiophosphate

A novel synthesized reagent, O,O-bis（2,3-dihydroxypropyl） dithiophosphate （DHDTP）, was investigated as depressant on the depression of chalcopyrite and galena, when ammonium dibutyl dithiophosphate （DDTP） was used as the collector in flotation tests. Zeta potential and adsorption measurement were performed to study the interaction between depressant and minerals. The flotation tests of two minerals show that DHDTP has slight depression on chalcopyrite in the whole pH range and strong depression on galena in the pH range of 6-10. When DHDTP dosage is increased, the recovery of galena decreases rapidly, while that of the chalcopyrite decreases slightly. The satisfied separation results of artificially mixed samples are that the copper grade and recovery rates of concentrate are 24.08% and 81%, respectively, when the pH is 6 with 278 mg/L DHDTP. Zeta potential and adsorption measurements show that DHDTP has more strongly adsorotion capacity to galena than chalcoovrite.

Effects of galvanic interaction between galena and pyrite on their flotation in the presence of butyl xanthate

The effects of galvanic interaction between galena and pyrite on their flotation and electrochemical characters were studied by electrochemical,adsorption,flotation and FTIR techniques,respectively.Electrochemical tests indicate that galena is electrochemically more active than pyrite and serves as an anode in galvanic combination with pyrite.The galvanic current density from a mixture of galena and pyrite is 4 times as high as the self corrosion current density of galena,which indicates that the corrosion rate of galena is accelerated.Adsorption tests show that the adsorption of butyl xanthate on galena surface is enhanced,and affected by a combination of pyrite-galena mixtures and conditioning time.Compared with individual mineral particles,galvanic interaction reduces the floatability difference between galena and pyrite.The flotation recovery of galena decreases while that of pyrite increases when two minerals are mixed together due to the influence of galvanic interaction on the formation of hydrophilic/hydrophobic product.The FTIR results show that the formation of dixanthogen on pyrite surface is depressed due to the galvanic interaction.

Influence of sodium 2,3-dihydroxypropyl dithiocarbonate on floatability of chalcopyrite and galena

Sodium 2,3-dihydroxypropyl dithiocarbonate（SGX）, which contains —OH and —CSS— in the molecule, was used to explore selective depression of galena from chalcopyrite in the flotation tests with ammonium dibutyl dithiophosphate（DDTP）, and zeta potential and adsorption measurements were performed to study the interaction between SGX and minerals. The flotation tests of single minerals show that SGX has slight activation on chalcopyrite and strong depression on galena in the whole p H range. With SGX dosage increasing, the recovery of galena decreases rapidly, while that of chalcopyrite increases slightly. At p H=6, the copper grade and recovery of concentrate are 29.52% and 82.15% respectively when mixture of two minerals is tested. Zeta potential and adsorption measurements indicate that SGX has strong adsorption on galena and slight adsorption on chalcopyrite.

Electrochemical behavior of galena and jamesonite flotation in high alkaline pulp

In order to effectively separate galena and jamesonite and improve the recovery during the mixing flotation, the interaction mechanisms between the minerals and the collector of diethyl dithiocarbamate （DDTC） were investigated. Single mineral flotation test was organized to research the effect of pulp pH value on the flotation behavior of galena and jamesonite. Electrochemistry property of the interaction of these two minerals with DDTC was investigated by cyclic voltammetry and Tafel tests. Flotation test shows that the recovery of jamesonite in high alkaline pulp is strongly depressed by lime （Ca（OH）2）. The cyclic voltammetry and Tafel tests results show that the interaction between galena and DDTC is an electrochemical process. High pH value has little influence on the interaction between galena and DDTC, while it has great effect on jamesonite due to self-oxidation and specific adsorption of OH^- and CaOH^＋ on jamesonite surface. Non-electroactive hydroxyl compound and low-electroconductive calcium compounds cover the surface of jamesonite, which impedes electron transfer and DDTC adsorption, thus leads to very low floatability of jamesonite.

Seaweed glue as a novel polymer depressant for the selective separation of chalcopyrite and galena

The use of seaweed glue(SEG)as a novel polymer depressant for the separation of chalcopyrite from galena with butyl xanthate(BX)as a collector was studied through microflotation experiments.Contact angle,adsorption,dynamic potential,and infrared spectral analyses were conducted to clarify the mechanism underlying the action of SEG on minerals.The results of microflotation experiments indicated that chalcopyrite could be selectively separated from galena by using a SEG depressant concentration of 15 mg·L^-1,BX concentration of 10 mg·L^-1,and methyl isobutyl carbinol concentration of 8.5 mg·L^-1 at pH 8.0.A Cu concentrate with a grading of 23.68wt% was obtained at a recovery rate of 81.52% from mixed minerals with 8.29wt% Cu content.Contact angle analysis showed that the effect of SEG on the wettability of galena was stronger than that on the wettability of chalcopyrite.Adsorption,zeta potential,and FT-IR spectral analyses revealed that SEG and BX were coadsorbed on the surfaces of galena.SEG depressed galena by covering xanthate ions in the functional groups of-COO and mainly underwent weak physisorption on chalcopyrite.These mechanisms account for the ability of SEG to depress galena effectively while enabling chalcopyrite flotation.

Theoretical study of 2-mercaptobenzimidazole derivatives as chelating collectors in flotation separation of galena and pyrite

Three 2-mercaptobenzimidazole derivatives,1-ethyl-2-mercapto-benzimidazole(EMBI),1-propyl-2-mercapto-benzimidazole(PMBI)and 1-benze-2-mercapto-benzimidazole(BMBI),were designed and synthesized in the paper,and their collecting behavior in flotation separation process of galena over pyrite was investigated by flotation tests on lab scale.Apart from this,density functional theory(DFT)calculation and molecular dynamics(MD)simulation were also used to elucidate their collecting mechanism.Results of flotation tests indicate that separation of galena over pyrite is feasible at pH 10,and BMBI has the best floatability among three collectors.DFT calculations show that BMBI has the highest occupied molecular orbital(HOMO)energy and strongest collecting effciency.The adsorption mode of three collectors on mineral surface by MD method indicates that the combination processes of collectors with mineral are exothermic,and the higher the binding energy,the frmer the collector adsorbs on the mineral surface and the higher collecting capacity.The calculation results demonstrate that the floatability of three collectors follows the order:BMBI>PMBI>EMBI,which is highly consistent with the flotation tests.

Electrochemical mechanism and flotation of chalcopyrite and galena in the presence of sodium silicate and sodium sulfite

The electrochemical mechanism involved in the selective separation of chalcopyrite from galena was investigated by flotation and electrochemical methods in the presence of sodium sulfite and sodium silicate,respectively,as a single depressant and their mixture as a combined depressant.Flotation tests revealed that the floatability of chalcopyrite was unaffected by depressants and its recovery remained constant(>80%)within the studied dosage range.Galena flotation was severely depressed with descending depressing order as follows:combined depressant﹥sodium silicate﹥sodium sulfite.Electrochemical analysis confirmed the high affinity of depressants on the galena surface,resulting in the formation of hydrophilic species,such as lead sulfite,lead sulfate,and lead orthosilicate.The oxidation of chalcopyrite surface and depressants did not exhibit any signals;conversely,the self-oxidation of chalcopyrite was depressed.The results of cyclic voltammograms well agreed with flotation results,demonstrating that chalcopyrite primarily reacted with the collector O-isopropyl-N-ethyl thionocarbamate and that galena mostly reacted with depressants.

Selective depression mechanism of ferric chromium lignin sulfonate for chalcopyrite–galena flotation separation

Selective recovery of chalcopyrite–galena ore by flotation remains a challenging issue.The development of highly efficient,low-cost,and environmentally friendly depressants for this flotation is necessary because most of available reagents(e.g.,K_2Cr_2O_4)are expensive and adversely affect the environment.In this study,ferric chromium lignin sulfonate(FCLS),which is a waste-product from the paper and pulp industry,was introduced as a selective depressant for galena with butyl xanthate(BX)as a collector.Results show that the residue recovery of Pb in Cu concentrate was substantially reduced to 4.73%using FCLS compared with 10.71%using the common depressant K_2Cr_2O_4.The underlying mechanisms were revealed using zeta-potential measurements and X-ray photoelectron spectroscopy(XPS).Zeta-potential measurements revealed that FCLS was more efficiently absorbed onto galena than onto chalcopyrite.XPS measurements further suggested that FCLS enhanced the surface oxidation of galena but prevented that of chalcopyrite.Thus,FCLS could be a potential candidate as a depressant for chalcopyrite–galena flotation because of its low cost and its lack of detrimental effects on the environment.

Comparative analysis of the dissolution kinetics of galena in binary solutions of HCl/FeCl_3 and HCl/H_2O_2

A comparative study of the dissolution kinetics of galena ore in binary solutions of FeCl3/HCl and H2O2/HCl has been undertaken.The dissolution kinetics of the galena was found to depend on leachant concentration,reaction temperature,stirring speed,solid-to-liquid ratio,and particle diameter.The dissolution rate of galena ore increases with the increase of leachant concentration,reaction temperature,and stirring speed,while it decreases with the increase of solid-to-liquid ratio and particle diameter.The activation energy （Ea） of 26.5 kJ/mol was obtained for galena ore dissolution in 0.3 M FeCl3 /8.06 M HCl,and it suggests the surface diffusion model for the leaching reaction,while the Ea value of 40.6 kJ/mol was obtained for its dissolution in 8.06 M H2O2 /8.06 M HCl,which suggests the surface chemical reaction model for the leaching reaction.Furthermore,the linear relationship between rate constants and the reciprocal of particle radius supports the fact that dissolution is controlled by the surface reaction in the two cases.Finally,the rate of reaction based on the reaction-controlled process has been described by a semiempirical mathematical model.The Arrhenius and reaction constants of 11.023 s^-1,1.25×10^-4 and 3.65×10^2 s^-1,8.02×10^ 6 were calculated for the 0.3 M FeCl3/8.06 M HCl and 8.06 M H2O2/8.06 M HCl binary solutions,respectively.

Thermodynamics and density functional theory study of potassium dichromate interaction with galena

The adsorption heat and reaction rate constant of potassium dichromate on the surface of galena were studied. The results indicate that potassium dichromate tends to adsorption on the galena surface. The reaction order is only 0.08385, suggesting that the concentration of potassium dichromate has little influence on its adsorption on the galena surface. In addition, the simulation of CrO2 4- adsorption on the PbS （100） surface in the absence and presence of O2 was carried out by density functional theory （DFT）. The calculated results show that CrO2 4- species adsorb energetically at the Pb-S bond site, and the presence of O2 can enhance this adsorption.

Flotation behaviors and mechanisms of chalcopyrite and galena after cyanide treatment

Adsorbing tests between CN? and chalcopyrite or galena were conducted firstly, and then flotation tests of the twocyaniding minerals were investigated in butyl xanthate (BX) system. Results showed that the interaction between CN? and the twomineral surfaces were both chemical adsorption and can be described by the Langmuir adsorption isotherm model. In the optimumcondition of pH 6.5 and 4.0 mg/L BX, the recovery of cyaniding chalcopyrite and galena reached 82.1% and 63.9%, respectively. BXimproved the hydrophobicity of the surfaces of the two minerals, although CN? reduced the contact angle on the surface of minerals.The inhibitory effect of CN? on chalcopyrite far outweighed galena. Electrostatic adsorption exists in the interaction between BX andthe surface of galena after cyanide treatment in the pH range of 4.2?8.4, while the interactions between BX and the surface ofchalcopyrite after cyanide treatment is chemical adsorption.

Depression behaviors of N-thiourea-maleamic acid and its adsorption mechanism on galena in Mo-Pb flotation separation

In present study,a novel organic depressant N-thiourea-maleamic acid(TMA)was synthesized and applied as a galena depressant in the flotation separation of Mo-Pb ores.The depression behaviors of TMA were tested through flotation experiments.A wider separation window for single minerals over 90.0%was obtained at 30.0 mg/L TMA,confirming that TMA could depress galena significantly,while effected molybdenite floatability slightly.An effective separation was obtained for artificially mixed minerals and actual Mo-Pb ores.The adsorption mechanism on galena was revealed by UV-Vis spectra,zeta potential tests,Fourier transform infrared spectroscopy(FT-IR)analysis,contact angle tests and X-ray photoelectron spectroscopy(XPS)analysis.The zeta potentials of galena became more negative and the contact angle of galena dropped from initial 74.36°to 57.8°with 30.0 mg/L TMA depressant,inferring that TMA had adsorbed on galena surface.The analysis results of UV-Vis spectra,FT-IR and XPS gave further evidence that TMA might chemisorb on galena surface via Pb sites on galena surface and the thiourea group in TMA molecular structure,while the carboxyl group played a role of hydrophilicity.

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.

Flotation and surface modification characteristics of galena,sphalerite and pyrite in collecting-depressing-reactivating system

The flotation tests and XPS analyses on galena,sphalerite and pyrite have been carried out in a collecting-depressing-reactivating system(hereafter referred as the CDR system).In this system,sulfide minerals were first collected and activated by the collector,and then depressed strongly by Ca(OH)2 in the strong alkaline solution,and finally reactivated by H2SO4.The flotation tests of pure minerals show that in this system the flotation behaviors of sphalerite and pyrite present irreversible characteristics along with the change of pulp potential.Furthermore,through the CDR system,considerable differences in the flotabilities between galena and sphalerite/pyrite are also observed.The XPS analysis results for galena,sphalerite and pyrite in a CDR system show that in the strong alkaline solution,some of the collectors,that have been already adsorbed on the mineral surface in the collecting process,are desorbed by Ca(OH)2.The XPS analysis results also show that in H2SO4 reactivating process,the surface hydroxides of galena are desorbed again by H2SO4 and replaced by diethyl dithiocarbamate,but those of sphalerite and pyrite are not desorbed.This flotation system may be applied to the bulk-differential flotation process of sulfur-bearing low-grade lead-zinc ores.

Deciphering anomalous Ag enrichment recorded by galena in Dayingezhuang Au(-Ag)deposit,Jiaodong Peninsula,Eastern China

Texture,geochemistry,and in-situ Pb isotope of galena were investigated to probe the origin of anomalous Ag enrichment in the Dayingezhuang Au(-Ag)deposit.Silver enrichment postdates the main Au mineralization and occurs in the south of the Dayingezhuang deposit.It is primarily associated with galena and the exsolution of Ag-rich sulfosalts(e.g.,matildite)in distal vein-ores related to steeply dipping brittle fractures.Silver-rich galena is characterized by the least radiogenic Pb isotope signature(^(206)Pb/^(204)Pb 17.195–17.258 and ^(208)Pb/^(204)Pb 37.706–37.793),possibly indicating a metasomatized lithospheric mantle or modified lower crustal source for Pb and Ag.Both of these mafic and ultramafic source regions have been previously suggested as Au reservoirs for other Jiaodong Au deposits,implying that the metal reservoir has only a weak control on the uneven Ag-enrichment.Since the Ag-enrichment areas are located in the footwalls of both the Dayingezhuang and Zhaoping faults,the enrichment was most likely dominated by local rotational stress during coeval movements of the two faults in a NE–SW compression and NW−SE extension regime.This work highlights the shallow-crust structural deformation responsible for controlling the flow of late ore-forming fluid resulting in local anomalous metal enrichment.

Kinetics of the electrochemical process of galena electrodes in the diethyldithiocarbamate solution

The electrochemical process of galena in a pH 12.8 buffer solution was investigated using chronoamperometry and chronopotentiometry. To establish kinetic parameters on the surface of galena in the diethyldithiocarbamate solution, the exchange current density and the dependence of current density on reaction time were determined. Experimental results demonstrate that the exchange current density of galena is 1.585× 10^-2A/m2 in the diethyldithiocarbamate-free solution. In the diethyldithiocarbamate solution, the thickness of lead diethyldi- thiocarbamate adsorbed on the surface of galena is 3.28 molecular layers, the diffusion coefficient of diethyldithiocarbamate on the surface of galena electrodes is 1.13 × 10^-10 m2/s, and the exchange current density of galena is 0.45 A/m2. Lead diethyldithiocarbamate on the surface of galena is firmly adsorbed.