Pyrite depression in marmatite flotation by sodium glycerine-xanthate

The depression of pyrite in marmatite flotation by sodium glycerine-xanthate （SGX） was investigated through microflotation, zeta potential and adsorption measurements. The flotation tests of mineral show that in the presence of SGX, marmatite can be activated by Cu^2＋ and shows good flotability, while pyrite cannot be activated and therefore shows poor flotability. At the pH value range from 4 to 11, the flotation selectivity between marmatite and pyrite is obvious when the SGX concentration is below 50 mg/L. The depression mechanism of SGX on sulfide minerals is discussed based on zeta potential and adsorption isotherm. Zeta potential measurement demonstrates that in the presence of Cu^2＋, SGX can strongly adsorb on the surface of pyrite, while it cannot adsorb on the surface of marmatite. The results of adsorption isotherms show that the adsorption density of SGX on pyrite is greater.

Mineral cleavage nature and surface energy: Anisotropic surface broken bonds consideration

The population of surface broken bonds of some typical sulfide, oxide and salt-type minerals which may belong to cubic, tetragonal, hexagonal, or orthorhombic system, were calculated. In terms of the calculation results, the cleavage natures of these minerals were analyzed, and the relationship between surface broken bonds density and surface energy was also established. The results show that the surface broken bonds properties could be used to predict the cleavage nature of most of minerals, and the predicted cleavage planes agree well with those reported in previous literature. Moreover, this work explored a rule that, surface broken bonds density is directly related to surface energy with determination coefficient（R2） of over 0.8, indicating that the former is a dominant factor to determine the latter. Therefore, anisotropic surface broken bonds density can be used to predict the stability of mineral surface and the reactivity of surface atoms.

组合抑制剂在铜锌浮选分离中的试验研究

云南某复杂多金属硫化矿可供回收的金属有铜、锌、锡、硫等,各矿物间嵌布粒度极细。试验研究结果表明,在不改变磨矿条件及生产所用捕收剂的基础上,用ZnSO4+Na2SO3+Na2S为组合抑制剂,经一次粗选、三次精选和一次扫选的开路试验获得铜精矿品位为16.5%、铜回收率为60.29%,铜精矿含锌6.2%,解决了长期以来铜回收率较低且铜精矿中含锌较高的实际问题。

Floc flotation of marmatite fines in aqueous suspensions induced by butyl xanthate and ammonium dibutyl dithiophosphate

The hydrophobic flocculation of marmatite fines in aqueous suspensions induced by butyl xanthate （KBX） and ammonium dibutyl dithiophosphate （ADD） was investigated using laser particle size analysis, microscopy analysis, electrophoretic light scattering, contact angle measurement and infrared spectroscopy. The studies were performed on single minerals with size 〈20 μm by varying several parameters, including pH, collector concentration and kerosene addition. The results show that the floc fotation closely correlated with the size of flocs and the particle hydrophobicity, but was not lowered with increasing the particle surface charges due to collector adsorption. Under good operating conditions, the floc flotation of marmatite fines as a function of KBX and ADD can all reach floatability over 90%, in comparison with conventional flotation obtaining floatability of about 60%. It also has been found that a small addition of kerosene greatly improved the floc flotation because of the formation of oil films on marmatite particles. The results of FTIR spectra indicate that adsorption of the two collectors onto marmatite were chemical adsorption.

Bioleaching and electrochemical property of marmatite by Sulfobacillus thermosulfidooxidans

Bioleaching and electrochemical experiments were conducted to evaluate marmatite dissolution in the presence of pure S.thermosulfidooxidans.The effects of particle size,p H controlling and external addition of Fe^3＋ ions on the zinc extraction were investigated.The results show that in the bioleaching process the best particle size range is 0.043-0.074 mm and adjusting p H regularly to the initial value has a profound effect on obtaining high leaching rate.External addition of Fe^3＋ ions could accelerate the bioleaching,while the concentration of additional Fe^3＋ over 2.5 g/L weakens the positive effect,and even hinders the dissolution of marmatite.SEM and XRD analyses of the leaching residues reveal that a product layer composed of elemental sulfur and jarosite is formed on the mineral surface,which results in a low leaching speed at later phase.The results of electrochemical measurements illustrate that additional Fe^3＋ ions could increase the corrosion current density,which is favorable to zinc extraction.The EIS spectra show that rate-limiting step does not change when Fe^3＋ ions are added.

Bioleaching and electrochemical property of marmatite by Leptospirillum ferrooxidans

The effects of several variables on the bioleaching of marmatite with pure L. ferrooxidans were investigated. The results show that zinc extraction increases with the decrease of pulp density. Adjusting pH tol.6 during the bioleaching process has a positive effect to the dissolution of marmatite. External addition of Fe^3＋ ions accelerates the bioleaching, while the concentration of additional Fe^3＋ over 2.5 g/L weakens the acceleration effect due to the inhibition effect on bacteria growth and the promotion of jarosite production. The electrochemical measurements were used to make further understanding on the dissolution of marmatite with and without additional Fe^3＋ in the presence of L. ferrooxidans. The experimental data illustrate that additional Fe^3＋ ions could increase the corrosion current density, which is favorable to zinc extraction. The EIS spectra show that rate-limiting step does not change when Fe^3＋ is added.

Determination of Fe and Zn contents and distributions in natural sphalerite/marmatite by various analysis methods

The contents of Fe and Zn in natural sphalerite samples were determined by chemical titration and spectroscopic techniques(portable X-ray fluorescence(P-XRF) spectrometry, electron probe microanalysis with energy dispersive spectroscopy(EPMA-EDS), electron probe microanalysis with wavelength dispersive spectroscopy(EPMA-WDS), and time-of-flight secondary ion mass spectrometry(To F-SIMS)). Besides, the distribution of Fe and Zn in sphalerite samples was analyzed by imaging EPMA-WDS and imaging To F-SIMS. The results show that Fe and Zn contents determined by each spectroscopic technique have good linearity with those determined by chemical titration(R^2>0.77), and the R^2 values of Fe are generally greater than those of Zn. The imaging analysis results revealed that Fe and Zn are not uniformly distributed in the sphalerite.

Molecular structures and activity of organic depressants for marmatite,jamesonite and pyrite flotation

Ten kinds of organic depressants were used to investigate the depressing performance on marmatite and pyrite.Flotation results show that the organic compounds only with single group of hydroxyl(-OH),carboxyl(-COOH) or amino(-NH2) in molecule are ineffective in depressing marmatite,jamesonite and pyrite.The combinations of these functional groups still cannot enhance the depressing ability of organic depressant.The thioglycollic acid containing reductive functional group(-SH) has a good depressing performance for marmatite and pyrite.The presence of benzene ring in molecule can enhance the depressing performance.The functional group electronegativity,hydrophilic-hydrophobic indexes and frontier orbital of organic depressants were calculated,and the criterion for the depressing effect of organic depressants to sulphide minerals was proposed.

Synthesis of glycerine-xanthate and its depressing mechanism in separation of marmatite from arsenopyrite

A small molecular organic depressor glycerine-xanthate was synthesized. The effect of glycerine-xanthate on the flotation of sulfide minerals was investigated based on a function of pH value and concentration of glycerine-xanthate through flotation experiments in the presence and absence of Cu^2＋. The results show that glycerinee-xanthate has a strong dressing effect on marmatite at pH〉6 and on arsenopyrite in weak acid and base conditions with butyl-xanthate as collector. In the presence of glycerine -xanthate, marmatite is activated by addition of Cu^2＋, but arsenopyrite cannot be activated and remains unfloatable. So the selective separation can be achieved for two minerals. The depression of glycerine-xanthate on sulfide minerals was discussed based on the radical electronegative calculation and the theory of HSAB. Infrared spectrum shows that there are some -OH and-CSS-in glycedne-xanthate molecule, which competes with butyl-xanthate on the mineral surface. As a result of many hydrophilic groups in glycerine-xanthate, the surfaces of marmatite and arsenopyrite become hydrophilic, thus the flotation of marmatite and arsenopyrite is depressed. The collector is adsorbed preferentially on the surface of marmatite and it shows a better floatability in the presence of Cu^2＋, whereas, the surface of arsenopyrite absorbs glycerine-xanthate and the flotation of arsenopyrite is depressed by glycerine-xanthate.

Bioleaching of sphalerite sample from Kooshk lead-zinc tailing dam

The zinc extraction from Kooshk lead-zinc tailing dam’s sample was investigated by bioleaching method. The Kooshk lead-zinc deposit/mine is located in Yazd province, Iran, and its tailing dam contains about 3.64%zinc, 0.97%lead and 24.18%iron. Experiments were designed and carried out by a mixed culture of mesophile bacteria as well as a mixed culture of moderate thermophile strain in the shake flasks. The results indicated that, more than 90% of sphalerite was dissolved during 14 d, while without bacteria, 44% of Zn was merely extracted. In addition, some experiments were performed in the absence of the bacterial medium （9K）. The results of these experiments indicated significant difference in Zn extraction with and without 9K until the 10th day of bioleaching, but after that the Zn extraction was improved and the same extraction was achieved at the end of bioleaching tests. This improvement can be attributed to the increase of the number of bacteria or Fe3＋concentration at the last days of leaching. Zn extraction kinetics of moderate thermophile bacteria was significantly higher than that of the mesophile, therefore sphalerite was successfully dissolved in preference to the pyrite using moderate thermophile bacteria in a lower redox potential.

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.

Bioleaching of sphalerite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans cultured in 9K medium modified with pyrrhotite

Elective culture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans in 9K medium modified with pyrrhotite was studied.Bioleaching of flotation concentrate of sphalerite by the selected bacteria was carried out.The results show that the microorganisms cultured by pyrrhotite are a mixture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans,of which the capability to oxidize ferrous to ferric irons is enhanced by the high mass ratio of Fe to S in pyrrhotite.Three pyrrhotite samples were separated into various parts with corresponding S/Fe ratios by magnetic separation and were used to culture the elective bacteria as the substrate.The association of the cultures could provide a more rapid and complete oxidation of sphalerite than that of bacteria cultivated by conventional methods.

Bioleaching of complex polymetallic sulfide ores by mixed culture

Bacterial leaching of single sulfide minerals and polymetallic sulfide ores was operated in shake flasks and small-scaled columns.The results show that bioleaching of jamesonite is not accessible,the iron extraction rate of pyrrhotite bioleaching reaches 98.2% after 26 d,and the zinc extraction rate of marmatite bioleaching reaches 92.3%,while the corresponding iron extraction reaches only 13.6% after 29 d.Pulp density has a significant effect on metal extraction of pyrrhotite and marmatite bioleaching.The corresponding metal extraction rate decreases with the increase of pulp density.For the polymetallic sulfide ores,zinc extraction of 97.1% is achieved after bioleaching in shake flasks for 10 d,while only 7.8% is obtained after bioleaching in small-scaled column.Analytical results of scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDX) reveal that large amount of calcium sulfate is formed on the mineral surface.

Effects of copper ions on dissolution mechanism of marmatite

The dissolution mechanism of marmatite in the presence of Cu^(2+)was intensively studied by experiments and density functional theory(DFT) calculations. Leaching experiments showed that Cu^(2+)accelerated marmatite dissolution at high temperatures(above 55 ℃), but the trend was reversed at low temperatures(below 45 ℃), which may be because the reaction mechanism between Cu^(2+)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.

Zircon U–Pb dating of Pubei granite and strontium isotope from sphalerite of the Xinhua Pb–Zn–(Ag) deposit,Yunkai Area of Guangxi Province,South China

The Yunkai Area is located at the southern South China Block and is part of the Qinzhou Bay-Hangzhou Bay Metallogenic Belt, which is a famous polymetallic mineralization belt. The Xinhua Pb–Zn–(Ag)deposit is located in the western part of Yunkai Area, with an abundance of Pubei batholiths. Zircon U–Pb geochronology of Pubei batholiths shows that crystallization age ranges from 251.9 ± 2.2 to 244.3 ± 1.8 Ma, thus belonging to Indosinian orogeny. Geochemistry and Sr isotopic compositions of the Pubei batholiths show that it is derived from the partial melting of large scale crustal melting during the stage of exhumation and uplifting of the lower-middle crust. In addition, strontium isotope of sphalerite from the Xinhua Pb–Zn–(Ag) deposit, has limited ranges in ^(87)Rb/^(86)Sr and ^(87)Sr/^(86)Sr, ranging from 0.4077 to 1.0449, and 0.718720 to 0.725245, respectively. The initial ^(87)Sr/^(86)Sr ratios of sphalerite ranges between 0.718720 and 0.725245, which is higher than that of upper continental crust and lower than that of the Pubei batholiths, illustrating the fluid might be derived from the mixing of Pubei pluton and upper continental crust.

Kinetics of carbothermic reduction of marmatite in presence of lime

The direct carbothermic reduction of marmatite in the presence of lime was studied by thermogravimetric method to determine the technical feasibility to produce Zn(g)without polluting with SO2(g).X-ray diffraction analysis of partially reacted samples indicated that the reduction occurred through the formation of ZnCaOS and Ca2Fe2O5 as intermediate products to yield Zn(g),and solid Fe and Ca S as the final products.Temperature had the major effect on the rate of reduction.Complete conversion of marmatite was obtained at 1100℃in about 10 min using 300 mg samples with molar ratio of(Zn,Fe)S:CaO:C equal to 1:1:1.The kinetics of the overall reduction reaction was analyzed by the model ln(1-X)=-kt,which represented the data well up to a fractional conversion of 0.95 in the temperature range of 1000-1150℃.The determined activation energy in this temperature range was 257 k J/mol.The results demonstrated the technical feasibility to produce Zn(g)by this method without producing noxious SO2(g)emissions.

Sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by thermophile Sulfolobus metallicus at 65 °C

Sulfur speciation transformation during bioleaching of pyrite-containing sphalerite concentrate by thermophile Sulfolobus metallicus （S. metallicus） at 65 ℃ was investigated by X-ray diffraction （XRD）, diffuse reflectance Fourier transform infrared spectroscopy （FT-IR） and sulfur K-edge X-ray absorption near edge structure spectroscopy （XANES）. The results show that the presence of S. metallicus effectively enhances the dissolution of the mineral. The yield of zinc increases from 0.5 g/L in sterile control to 2.7 g/L in bioleaching. The pyrite in the concentrate facilitates zinc dissolution in the early stage, but has hindrance role in the late stage for the formation of jarosite. Sulfur speciation analyses show that jarosite and elemental sulfur are main products in bioleaching process, and the accumulation ofjarosite is mainly responsible for the decline of leaching efficiency.

Bioleaching of marmatite using moderately thermophilic bacteria

The process of bioleaching marmatite using moderately thermophilic bacteria was studied by comparing marmatite leaching performance of mesophiles and moderate thermophiles and valuating the effect of venting capacity as well as pulp density on marmatite leaching performance of moderate thermophiles. The results show that moderate thermophiles have more advantages over mesophilies in bioleaching marmatite at 45 ℃ and the pulp density of 50 g/L, and the zinc extraction efficiency reaches 93.1% in 20 d. Aeration agitation can improve the transfer of O2 and CO2 in solution and promote the growth of bacteria and therefore, enhance the leaching efficiency. Under the venting levels of 50, 200 and 800 mL/min, the zinc extraction efficiencies by moderate thermophiles are 57.8%, 92.5% and 96.0%, respectively. With the increase of pulp density, the total leaching amount of valuable metals increases, however, the extraction efficiency decreases due to many reasons, such as increasing shear force leading to poorly growth condition for bacteria, etc. The zinc extraction decreases remarkably to 58.9% while the pulp density mounts up 20%.