The influence of pyrite content on the flotation of chalcopyrite/pyrite mixtures

In the flotation of copper ores, several processing plants report that copper recovery is affected by the proportion and reactivity of pyrite in the ore, with the effect becoming more intense when the feed particles are finer as a result of regrinding. In this work, a mixed model mineral system consisting of chalcopyrite (CuFeS₂) and pyrite (FeS₂) with varying pyrite content (20–80 wt.%) was used to investigate the effect of pyrite on the pulp chemistry and chalcopyrite recovery. Flotation tests showed that chalcopyrite flotation rate, recovery and grade, as well as the pulp oxidation potential, decreased with increasing pyrite content whilst pyrite recovery increased. Surface analysis (XPS, ToF-SIMS and EDTA) indicated that copper activation of pyrite increased with increasing pyrite content, facilitating pyrite recovery. The decrease in chalcopyrite recovery can be attributed to increased surface oxidation.     

The separation of chalcopyrite and chalcocite from pyrite in cleaner flotation after regrinding

In this study, the differences between the separation of chalcopyrite and chalcocite from pyrite in cleaner flotation after regrinding were investigated. In the rougher flotation prior to regrinding, high chalcopyrite and chalcocite recovery were obtained in conjunction with high pyrite flotation recovery due to the activation of pyrite by copper ions during primary grinding. The rougher flotation concentrate was reground in a rod mill before cleaner flotation. It was found that chalcopyrite and chalcocite exhibited different flotation behavior and also affected pyrite flotation differently in cleaner flotation. The mechanism underpinning these phenomena was investigated by a range of techniques including the polarization of mineral electrodes, X-ray photoelectron spectroscopy (XPS) analyses and ethylene diamine tetraacetic acid (EDTA) extraction. It was found that the flotation behavior of both copper minerals and their effect on pyrite flotation after regrinding were governed by their electrochemical activities and galvanic coupling with pyrite.     

The effect of regrind mills on the separation of chalcopyrite from pyrite in cleaner flotation

Stirred mills have been widely used for regrinding and are more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms and redox environments during grinding. In this study, the effect of regrinding with these two types of mills on the separation of chalcopyrite from pyrite in the cleaner stage was studied. A laboratory rod mill and a laboratory stirred mill were used to regrind rougher flotation concentrates. It was found that chalcopyrite and pyrite exhibited different flotation behavior after regrinding with the rod mill and the stirred mill, resulting in different separability of chalcopyrite from pyrite. The mechanism underpinning this phenomenon was investigated by a range of techniques including dissolved oxygen demand measurements, X-ray photoelectron spectroscopy (XPS) and Time of flight secondary ion mass spectrometry (ToF-SIMS). It was found that the two mills produced different surface oxidation and pyrite activation by copper ions which determined the separation of chalcopyrite from pyrite. This study demonstrates that the selection of a regrind mill should not only depend on its energy efficiency but also the property of surfaces produced for subsequent flotation.     

Acidic sulphate leaching of chalcopyrite concentrates in presence of pyrite

Copper concentrates with mineralogy dominated by chalcopyrite have slow leaching kinetics at atmospheric pressure in sulphate media because of the formation of passivation layer on its surface during the leaching. To enhance the leaching rate of the copper concentrate, pyrite was added to act as a catalyst. Pyrite and copper sulphide minerals then form a galvanic cell which increases both the copper leaching rate and yield. Effect of parameters such as solution redox potential, temperature, initial acid concentration, solids content, total initial iron concentration and pyrite to copper sulphide minerals mass ratio were investigated. Mineralogical analyses by XRD were performed on selected leach residues and the feed materials. A copper recovery higher than 80% in 24 h was achieved at a redox potential of 410 mV vs Ag, AgCl, a temperature of 85 °C, 15 g/L of initial acid concentration, a solid content of 7.8% (w/v), a total initial iron concentration 5 g/L and pyrite to copper sulphide minerals mass ratio 2:1. XRD patterns on leach residues showed that candidates for surface passivation, i.e. jarosite and elemental sulphur, were formed at high total initial iron concentrations.     

Selective flotation of chalcopyrite and molybdenite with plasma pre-treatment

For pretreatment of selective flotation, plasma treatment of chalcopyrite and molybdenite was applied then the minerals were washed by solution at pH 9 with oxygen bubbling. Surface characteristics of these minerals were investigated with AFM, XPS, zeta potential and contact angle measurements. Contact angle of chalcopyrite and molybdenite decreased a lot by plasma treatment. When they were washed with pH 9 solution with oxygen bubbling, contact angle of molybdenite increased whereas chalcopyrite one kept low. Adhesion force measurements indicated similar behavior. Result of flotation experiments indicated low recovery of both chalcopyrite and molybdenite after plasma treatment and only molybdenite recovery became higher after washing. Selective flotation of chalcopyrite and molybdenite could be achieved with this process. However, flotation of mixture of chalcopyrite and molybdenite after these treatments indicated both chalcopyrite and molybdenite were depressed. Addition of emulsified kerosene changed the flotation results where molybdenite was floated and chalcopyrite was depressed. Possible mechanism of selective flotation was proposed from the results of XPS, AFM, etc.     

铜钼浮选分离中黄铜矿抑制剂的研究进展及展望

铜、钼是我国重要的战略资源,二者主要来源于斑岩型铜钼矿。浮选处理该类矿石资源时,通常采用混合浮选-铜钼分离工艺获得铜精矿和钼精矿。然而,由于黄铜矿和辉钼矿可浮性接近,为了较好的将二者有效分离,常需加入一定量抑制剂以调控二者表面湿润性,进而实现高效铜钼分离。因此,抑制剂一直是铜钼分离的核心所在。本文综述了近年来黄铜矿无机抑制剂、有机抑制剂和组合抑制剂三个方面的研究进展,分析并展望了未来铜钼浮选分离的重点研究方向,旨在为实现绿色高效铜钼分离提供技术及理论支撑。     

The effect of temperature on the pulp and froth phases in the flotation of pyrite

The effect of temperature on the flotation of pyrite has been investigated. At temperatures below ambient an increase in temperature results in an increase in the rate of flotation of fast-floating particles but has a minimal effect on that for slow-floating particles. At temperatures greater than ambient the dominant effect of increasing temperature is to decrease the viscosity of the water thus increasing the rate of elutriation of the gangue back to the pulp. In general an increase in temperature resulted in an increase in the rate of pyrite recovery and the sulphur grades and a decrease in the water recovery and size of the bubbles in the pulp.     

铜离子对闪锌矿、黄铁矿浮选的选择性活化机理研究

本文对铜离子活化闪锌矿(ZnS)和黄铁矿(FeS2)的表面化学、溶液化学以及两种矿物的浮选分离进行了综合评述,分析讨论了铜离子浓度、活化时间、pH值、表面电荷、表面氧化程度、矿浆电位等主要因素对闪锌矿和黄铁矿活化浮选的影响.为生产实践中闪锌矿、黄铁矿的绿色、高效浮选分离提供一定的理论及技术支撑.     

Investigations on different starches as depressants for iron ore flotation

Four different starches, namely soluble starch, corn starch, potato starch and rice starch with different characteristics have been studied as depressants for hematite in cationic flotation using dodecylamine as the collector. Surface charge measurement and Fourier transform infrared spectroscopy (FTIR) have been used to understand the starch–hematite interaction. The lowering of surface charge and change of peaks at 750–1500 cm⁻¹ region indicate the presence of hydrogen bonding and chemical interaction between hematite and starches. The results of flotation studies with pure minerals of hematite and quartz and a low grade iron ore at different conditions suggest that all the starches are good depressants for hematite. Maximum adsorption for all the four starches with hematite occurs at the pH value 5–9. However soluble starch is found to be the better depressant at slightly alkaline pH. The flotation of natural occurring banded iron ore using different starches has indicated that it is possible to achieve an iron grade of 63–65% Fe with 85–88% recovery.     

石英与蛇纹石异相凝聚及其对黄铁矿浮选的影响

通过单矿物和人工混合矿的浮选试验、Zeta电位测试、吸附量测试,研究了蛇纹石和石英异相凝聚的机理,以及对黄铁矿浮选的影响,以进一步探索多种矿物的体系中,蛇纹石对硫化矿物浮选影响的主要原因。结果表明:通过添加石英,可以恢复黄铁矿对捕收剂的吸附量,减弱蛇纹石的不良影响,不同粒级的石英与蛇纹石的异相凝聚作用强弱不同,粒级越细的石英,与蛇纹石的异相凝聚作用越强。     

Selective depression of pyrite with chitosan in Pb–Fe sulfide flotation

Chitosan was used in the flotation of pyrite–galena mixtures. The results indicated that chitosan preferentially adsorbed on pyrite and galena was floated from the pyrite–galena mixtures. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) analyses were performed to study the interaction mechanism of chitosan on the pyrite and galena minerals at pH 4 and 6. ToF-SIMS showed that chitosan adsorbed heavily on pyrite but barely on galena when a mixture of pyrite and galena was treated by chitosan. The high resolution XPS spectra indicated that both the amine and the hydroxyl groups from chitosan reacted with pyrite surface, whereas no significant binding energy shifts were observed on galena. Combined with the authors’ previous studies of chitosan in other sulfide flotation systems, it was observed that chitosan could depress pyrite, galena, sphalerite and chalcopyrite to different extent when the minerals were floated alone. However, in the flotation of mineral mixtures, chitosan selectively adsorbed on one mineral which depressed its flotation, allowing the other mineral to be floated from the mixture. The competitive adsorption was attributed to the differences in the electron affinity value of the lattice metal ions. Chitosan strongly binds with metal ions with a high electron affinity.     

Electrochemical characteristics and collectorless flotation behavior of galena: With and without the presence of pyrite

The electrochemical characteristics, surface properties and collectorless flotation behavior of galena with and without the presence of pyrite have been studied. Electrochemical tests confirmed previous reports in the literature that galena is electrochemically more active than pyrite and serves as the anode in galvanic combinations with pyrite. Cyclic voltammograms and polarization curves tests indicated that the addition of pyrite did not change the oxidative and reductive products of galena, but increased the current density during oxidation process. Zeta potential of galena showed a significant difference when coupled with pyrite, due to the influence on the oxidation of the mineral surface. Flotation results showed that the presence of pyrite leading to an influence on the collectorless floatability of galena and the influence correlation with the composition proportion of each mineral.     

Formation of hydrogen peroxide by pyrite and its influence on flotation

Formation of hydrogen peroxide (H₂O₂), an oxidising agent stronger than oxygen, by pyrite (FeS₂), the most abundant metal sulphide on Earth, during grinding was investigated. It was found that pyrite generated H₂O₂ in pulp liquid during wet grinding and also the solids when placed in water immediately after dry grinding. Type of grinding medium on formation of hydrogen peroxide revealed that the mild steel produced more H₂O₂ than stainless steel grinding medium, where Fe²⁺ and/or Fe³⁺ ions played a key role in producing higher amounts of H₂O₂. The effect of grinding atmosphere of air and N₂ gas showed that nitrogen environment free from oxygen generated more H₂O₂ than air atmosphere suggesting that the oxygen in hydrogen peroxide is derived from water molecules. In addition, the solids after dry grinding producing more H₂O₂ than wet grinding indicate the role of pyrite surface or its catalytic activity in producing H₂O₂ from water. This study highlights the necessity of relooking into the electrochemical and/or galvanic interaction mechanisms between the grinding medium and pyrite in terms of its flotation behaviour.     

The depression of pyrite in selective flotation by different reagent systems – A Literature review

Pyrite is a gangue mineral widely associated with valuable minerals. It is problematic to deal with in differential flotation because it easily reports to flotation concentrates. Pyrite may float due to natural or self-induced hydrophobicity or collector-induced hydrophobicity. Its flotation can also be enhanced by the activation of copper or lead ions emanating from other minerals. Depressants are generally required to selectively depress pyrite. In this article, a comprehensive review of the fundamental studies of depression mechanisms and effectiveness of commonly used reagent systems to depress pyrite is presented. It includes inorganic reagents (hydroxyl ions, oxygen conditioning, cyanide, sulfoxyl reagents, etc.), organic reagents such as polysaccharides (starch, dextrin, carboxymethyl cellulose etc.), polyacrylamides, wood-extracted biopolymers, diethylenetriamine and a combination of these methods. Overall, the action of pyrite depressants is either to desorb the collector or activator from pyrite surface, deactivate the activating ions, prevent collector adsorption on pyrite, or make the pyrite surface hydrophilic. The mechanisms of some non-xanthate collectors such as dithiophosphate, dithiophosphinate and thionocarbamate in rejecting pyrite were also briefly reviewed.     

The mechanism of pyrite depression at acidic pH by lignosulfonate-based biopolymers with different molecular compositions

Electrochemical studies, adsorption isotherms and contact angle measurements were conducted to compare the effect of three lignosulfonate-based biopolymers (DP-1775, DP-1777 and DP-1778) as pyrite depressants in flotation at acidic pH. The adsorption isotherms showed that DP-1775 and DP-1778 had a higher adsorption capacity than DP-1777. The contact angle of pyrite particles was reduced by the three biopolymers in the order of DP-1778 > DP-1777 > DP-1775 at a similar adsorbed amount. These results are in accordance with biopolymers’ ability to inhibit collector adsorption in electrochemical studies. The depressing effect of these biopolymers was related to the biopolymer composition. It was found that the biopolymer molecular weight determined its adsorption capability and surface coverage. The content of functional groups was responsible for the change in contact angle. While a higher molecular weight led to greater pyrite depression, calcium ion as a counterion in the biopolymer structure also played a role.     

Effects of free cyanide and cuprous cyanide on the flotation of gold and silver bearing pyrite

At gold and silver mineral processing plants, cyanide species are always present in the process water recycled to flotation circuits, despite the cyanide destruction process. The effect of cyanide, in particular, cuprous cyanide on gold and silver flotation has not been well understood. In the present study, free cyanide and cuprous cyanide species were isolated and their effects on the flotation of a pyritic ore were evaluated. It was found that free cyanide depressed gold and silver flotation through their carrier, pyrite. Cuprous cyanide mainly in the form of Cu(CN)₃²⁻ depressed pyrite flotation similarly as free cyanide. Electrochemical studies including open circuit potential (OCP), cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques were carried out to understand the underpinning depression mechanism of cyanide species on pyrite flotation using xanthate as collector. It was found that all surface electrochemical reactions were inhibited by either free cyanide or cuprous cyanide. The surface layer as a result of xanthate adsorption on pyrite was completely removed in the presence of these cyanide species, which was suggested to contribute to the hydrophilic pyrite surface.     

The flotation separation of scheelite from calcite using acidified sodium silicate as depressant

The flotation separation of scheelite from calcite using sodium oleate as collector and acidified sodium silicate as depressant has been studied. The results show that sodium oleate has collecting ability to both scheelite and calcite and the flotation separation of scheelite from calcite cannot be realized if collector is used only. The depressant acidified sodium silicate has selective depression effect on calcite and the optimum ratio of sodium silicate to oxalic is 3:1. The use of acidified sodium silicate as depressant can achieve the flotation separation of scheelite from calcite. Infrared studies and zeta potential measurements showed that the pre-adsorption of acidified sodium silicate interferes with the adsorption of sodium oleate on calcite surface while does not interfere with its adsorption on scheelite surface.     

Effect of powerful nanosecond electromagnetic impulses on surface and flotation properties of carbonate-bearing pyrite and arsenopyrite

The effect of powerful nanosecond electromagnetic impulses (PEMI) on the surface and flotation properties of arsenopyrite and carbonate gold-bearing pyrite from the Darasunsk deposit has been studied. X-ray-phase diffractometry, X-ray photoelectronic and IR Fourier-spectroscopy, and raster electronic microscopy were employed in investigations. It was established that the alteration of the phase composition of surface depends non-linearly on terms of treatment (dry or wet) and the number of electromagnetic impulses used and has appreciable influence on oxidation and hydrophobicity of minerals, thus allowing the selective separation of pyrite from arsenopyrite by flotation in the neutral medium. __________ Translated from Fiziko-Tekhnicheskie ProblemyRazrabotki Poleznykh Iskopaemykh, No. 5, pp. 105–118, September–October, 2008.     

硫酸渣加碱焙烧过程中富铁效果研究

硫酸渣中有价元素铁含量较高,具有综合回收利用价值。硫酸渣中铁主要以赤铁矿形式存在,脉石主要为石英,赤铁矿呈蓝白色,形状不规则,表面空洞均被细小脉石填充。试验证明,采用焙烧法从硫酸渣中富集铁,在焙烧时间为650℃,焙烧时间为0.5 h,氢氧化钠的添加量为1 g(占10%)工艺条件下,获得硫酸渣中铁的含量为61.5%,达到炼铁原料的要求,实现了二次资源的综合回收利用。