The influence of pyrite pre-oxidation on gold recovery by cyanidation

The influence of pyrite pre-oxidation in alkaline solutions on gold recovery by cyanidation from Twin Creek refractory gold ore in which pyrite was identified as the major sulfide mineral has been investigated with the aid of electrochemical measurements, leaching experiments, and direct analysis of reaction products for selected residues. It was found that gold recovery by cyanidation in bottle roll experiments mainly depended on the extent of pyrite pre-oxidation. The rate of pyrite oxidation in alkaline solutions measured by electrochemical measurements, including chronoamperometry and linear sweep voltammetry, increased with an increase in pH, potential, and temperature. All alkaline reagents used for the electrochemical measurements, NaOH, NH₄OH, Na₂CO₃ and Ca(OH)₂, showed a similar effect on pyrite oxidation kinetics. However, the results of alkaline pre-oxidation for pyrite of the Twin Creek refractory gold ore suggested that NaOH and Na₂CO₃/Ca(OH)₂ were superior to Ca(OH)₂. Without pre-oxidation, cyanide leachable gold was found to be only 20% which could be increased to 70% under appropriate pre-oxidation conditions. At the same time, cyanide consumption decreased from 2.5 kg/t ore to 1.5 kg/t ore.Selected residues after pre-oxidation and cyanidation were examined by X-ray diffraction. Backscattered electron images of pyrite particles in these residues were taken. The reaction products at the surface of pyrite particles were found to be iron-, silicon-, and calcium-bearing compounds with variable amounts of sulfur as determined by X-ray energy dispersion analysis. Additionally, some mineral fines, such as aluminum and/or potassium-bearing minerals, were found to be present at the partially oxidized pyrite surface.     

Gold losses from cyanide solutions part II: The influence of the carbonaceous materials present in the shale material

Gold was found to be mainly adsorbed onto the carbonaceous particles in the Beatrix shale material with possible minor loss of gold due to co-precipitation of gold with Mg(OH)₂ and Fe(OH)₃.Two types of carbonaceous material were present in low concentrations in the Beatrix shale and resembled kerogen. The one type can be described as filamentous particles and the other as roundish particles. Rank measurements done on the carbonaceous particles in the shales showed that they fall in the anthracite range. Adsorption of gold on carbonaceous material of similar rank showed that anthracite has the highest propensity to adsorb gold. This suggests that the carbonaceous particles would have similar gold adsorption properties as anthracite. The lack of an obvious correlation between the propensity of a shale to adsorb gold and its carbon content is probably due to the fact that not all the carbonaceous particles are liberated during milling so that they can be brought into contact with' the gold cyanide solution.     

Improving gold flotation selectivity by using new collecting agents

As a result of the present research into the effect of xanthogenate and new collecting agents on flotation properties of gold, the authors defined selective characteristics of a nitrogen-containing agent (MTKh) and phosphorus-containing agent (DIPh) relative to gold. The article describes testing the new collecting agents on gravity tailings of the quartz-sulfide-gold ore.     

Interaction of sodium diisobutyl dithiophosphinate and platinum in aqueous solutions and on sulphide surface

For the noble metal flotation reagents, the authors propose a new test method of selective adsorption on surface of minerals covered with noble metal grains, by using a scanning electron microscope equipped with an X-ray energy-dispersive microanalyzer. Sorption of DTPINa was recorded by SEM and thin layer chromatography on surface of platinum metal grains in the form of a compound identical to the synthesized compound Pt[(iso-C₄H₉)2PS₂]₂. It has been found that interaction of DTPI and platinum ions can run in unheated aqueous solutions at a rate sufficient for flotation. In pH 4–9 range, the rate of platinum DTPI formation is maximal. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 75–84, March–April, 2009.     

Experimental-analytical methods of the investigating the effect of complexing reagents on platinum flotation

The paper considers the studies into the hydrophobic properties of platinum and platinum arsenide, sperrylite, in the solution with added complexing reagents by using the method of measuring the force of the air bubble abstraction from the mineral surface. The effect of these complexing reagents on the chemical properties of sperrylite and pyrrhotine is analyzed. A new-developed procedure for treatment of pyrrhotine by chloroplatinic acid is presented, and the comparative flotation of natural pyrrhotine and platinum-pretreated pyrrhotine with the complexing reagents is described. The collecting properties of diisobutyl dithiophosphinate for platinum are determined, and the use of this reagent as an additional collector for platinum-group metals is confirmed in the course of the experimental flotation of platinum-bearing copper-nickel ore samples. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 68–75, May–June, 2008.     

Finely Dispersed Micro- and Nano-Gold Recovery Using Thermomorphic Polymer with Diphenylphosphine

The article reports test data on adsorption and flotation characteristics of thermomorphic polymer joined with diphenylphosphine—TMPD. The test materials are natural pyrite and arsenopyrite, and models of gold-bearing sulfide minerals. Electron microscopy and X-ray structure analysis prove that reductive adsorption of gold at the surface of sulfide minerals from HAuCl₄ solution allows modeling natural aggregates of sulfides and finely dispersed gold. UV spectrophotometry proves selective adsorption of TMPD at gold. Laser scanning microscopy shows connection of TMPD with micro- and nano-size gold on polished sections of pyrite and arsenopyrite. During monomineral flotation, joint use of TMPD and butyl xanthate at a ratio of 1:1 doubles the yield of gold-bearing sulfides and enables maximum recovery of gold minerals at the total consumption of reagents reduced by 30–50%. It is found that TMPD is selective relative to gold-bearing minerals and its combination with xanthate ensures a considerable increment in gold-bearing mineral recovery by flotation.     

江西金尾矿资源的性质与矿物学特征研究

黄金矿山选矿中95%以上为尾矿,实现金尾矿综合利用的前提是充分查明其性质与特征。针对江西某金尾矿,采用化学分析、ICP和γ能谱仪,查明了金尾矿的化学成分和放射性核素限量,利用岩矿鉴定、EMPA和EDS分析等手段,研究了该物料的资源性质与矿物学特征,分析了其综合利用前景。结果表明：该金尾矿中含金0.495 g/t,含银1.70 g/t,且金以铁等氧化矿物中包裹金存在,占比58.18%,显微镜下未发现残余的金颗粒。金尾矿中SiO₂、Al₂O₃分别为62.21%和13.54%,残余的矿物主要为石英、绢云母和方解石,其中绢云母具有较好的回收前景。放射性核素限量合格,若制备建材制品产销与使用不受限制。该试样筛析-0.074 mm占41.58%,残余含金矿物的单体解离度不高,含金矿物多赋存在比重较高的重矿物或金属矿物中,仍有部分提金潜力。绢云母多为细粒级产出,片径为0.01～0.2 mm,提取时需加强分级和细粒易泥化物的分散,防止影响其品质。     

浮选药剂与矿物作用机理研究方法探讨

浮选过程中药剂与矿物的作用机理十分复杂,明确浮选药剂与矿物的作用机理可以为浮选药剂的分子设计提供理论指导。近年来通过试验研究及分析测试技术对浮选药剂与矿物表面作用的研究,取得了很多成果。总结了浮选药剂与矿物作用机理的研究方法,并介绍了几种主要研究方法的应用实例。单矿物试验、动电位、接触角、吸附量等方法可明确药剂与矿物的作用强度及矿物可浮性;通过IR、UV、XPS、SIMS、AES等手段可分析浮选药剂与矿物的作用方式;利用分子模拟技术可以从微观层面模拟药剂与矿物的作用过程,得出作用规律。借助各种研究测试方法为研究矿物表面的结构,理解矿物与浮选药剂之间作用过程,探讨作用机理提供了有力的工具。指出分子模拟技术必将广泛地应用于浮选药剂作用机理的研究中,在提高研究效率及新型浮选药剂的开发中起到重要作用。     

Fundamental electrochemical and Raman spectroscopic investigations of the flotation behaviour of PtAs2

Platinum arsenide minerals are important platinum carriers in altered platinum reserves such as the Great Dyke of Zimbabwe and the Platreef (in the Bushveld Complex of South Africa). Industrial mineralogical investigations suggest these minerals to be poorly recovered during froth flotation and are believed to be slow floating. In this work, electrochemical investigations, electrochemical contact angle measurements and Raman spectroscopy have been employed to investigate the interaction of ethyl xanthate with synthetic PtAs₂. The electrochemical investigations suggest a strong interaction of the xanthate with the mineral at potentials higher than the reversible potential of the xanthate–dixanthogen couple. Raman spectroscopy has confirmed the presence of dixanthogen on the mineral surface when the surfaces are anodically polarized. Contact angle investigations indicated the surface to be hydrophobic; possible mechanisms of the slow floating behaviour are discussed.     

The interaction of sodium mercaptobenzothiazole with gold electrode and nanorod surfaces

Attenuated total reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy have been applied to characterise and investigate the interaction of sodium mercaptobenzothiazole (MBT) with gold surfaces and gold nanorods. Gold nanorods (Au NRs) with average aspect ratio of 4.04 ± 0.08 were synthesised and reacted with MBT. Gold(I) mercaptobenzothiazole and the dithiolate, 2,2′-dithiobisbenzothiazole ((MBT)₂) were synthesised and characterised to provide a basis for compound identification. It was concluded that MBT could link two Au NRs by adsorption through the exocyclic S atom on one NR and the endocyclic S atom on the other NR, thereby leading to the formation of Au nanochains in the suspension. The MBT flotation of 100 μm gold particles was also investigated utilising controlled potential techniques. The gold metal particles floated in the cell when the potential reached 0.5 V. At that potential, (MBT)₂ was observed on the gold particles, and their floatability was attributed to the adsorption of that dithiolate species.     

Effects of frother type and froth height on the flotation behaviour of chromite in UG2 ore

About 70% of the UG2 reef consists of the gangue mineral chromite (FeO · Cr₂O₃). In the processing of UG2 ore by flotation for the recovery of platinum group elements (PGEs) the presence of chromite in the concentrates can cause serious downstream processing problems and a grade of less than 3% Cr₂O₃ is sought. This constrains operating procedures and compromises optimum recovery of the PGEs.In this study, the influence of the froth phase on the recovery of chromite was investigated by changing both frother type and dosage and froth height in batch scale flotation tests. The results obtained showed that it was possible to obtain concentrates with less than 3% Cr₂O₃ content by increasing the froth height, allowing for better drainage of both entrained gangue particles and coarse particles with low hydrophobicity. At a 3 cm froth height, very low water and mass recovery were obtained and thus low entrainment. Nevertheless a small amount of chromite particles coarser than 45 μm was persistently recovered which may be attributed to the true flotation of these particles.The mechanism of chromite recovery was discussed on the basis of the difference in the appearance of the froth structure and water recovery.     

方解石与共伴生矿物浮选交互影响研究进展北大核心

方解石与共伴生矿物常通过浮选方法分离,其分选效果取决于浮选药剂性能和矿物表面性质差异。然而,混合矿体系中矿物颗粒间存在交互作用,如异相凝聚或溶解组分吸附、迁移、反应等,影响高效浮选药剂选择性吸附和矿物间表面性质差异,是高效浮选药剂在实际矿石分选体系中失去选择性的一个重要原因,也是复杂矿石难以分选的一个重要因素。归纳综述了氧化物矿物、碳酸盐矿物和含钙盐类矿物与方解石浮选分离过程中的交互影响机制及调控方法,分析了含有方解石体系的矿物交互影响研究现状与发展趋势,为方解石与共伴生矿物高效浮选分离研究提供借鉴。     

Flocculation and flotation response of Rhodococcus erythropolis to pure minerals in hematite ores

Rhodococcus erythropolis as a flotation collector for hematite was evaluated in the study. The surface morphology and cell wall composition of R. erythropolis was analyzed. Zeta potentials for four pure minerals from hematite ores were measured before and after adsorption by R. erythropolis. Pure mineral flotation tests and mixed mineral separation tests were performed to describe adsorption characteristics and mechanisms. A rod-shaped bacterium was detected with CH₂, CH₃ and COO groups on its cell wall that imparted hydrophobicity and negative charges. The ability of R. erythropolis to collect hematite was stronger than its ability to collect quartz, kaolinite and apatite. For a pulp pH of 6 and a cell concentration of 75 mg/L, recovery rate of hematite was 89.67%. The recovery differences between hematite and quartz, kaolinite and apatite were 66.43%, 60.36% and 54.30%, respectively. These data indicated that electrical properties of hematite surface were more suitable for adsorption of R. erythropolis than other three minerals. The adsorbed hematite particles appeared as large agglomerates after interaction with R. erythropolis. The quartz, kaolinite and apatite particles, however, were in the form of dispersed particles or small agglomerates. The chemical adsorption of hematite on bacterial cell wall resulted in agglomeration. The effects of flocculation and flotation of R. erythropolis on micro-fine hematite particles were characterized for the first time. The results showed that R. erythropolis can act as a flotation collector for hematite from hematite ores.     

Use of X-ray computed tomography to investigate crack distribution and mineral dissemination in sphalerite ore particles

As the trends in mineral processing move towards the beneficiation of finer grained and more complex ore bodies, so too do the methods needed to understand and model these processes. During the heap leaching of low-grade ore bodies, the crack distribution and mineral dissemination in ore particles are important characteristics that determine the performance of sub-processes, such as the diffusion of reagents in and out of particle pores. Recent developments in X-ray computed tomography (CT) as an advanced diagnostic and nondestructive technique have indicated the potential for the technology to become a tool for the acquisition of 3-D mineralogical and structural data. The spatial distribution of cracks and mineral dissemination in particles derived from a sphalerite ore in the Northern Cape, South Africa, was characterized using a high-resolution industrial X-ray CT system.This paper describes the use of image analysis techniques including image segmentation, which uses a combination of thresholding and other methods to characterize and quantify crack and mineral dissemination in the sphalerite particles. The results are validated with those obtained using traditional techniques such as physical gas (with N₂) adsorption, mercury intrusion porosimetry, SEM and QEMSCAN. A comparison of the effect of different comminution devices (HPGR and Cone crusher) on crack generation is also given.     

某石英脉型金矿选矿技术研究及工业实践

河南某岩金矿床属于国内典型的石英脉型金矿,其矿石性质兼具了国内石英脉型矿床的共性。研究结合了其矿石性质的特性,在总结了我国传统的石英脉型金矿选矿工艺流程优缺点的基础上,针对其现场生产存在的磨矿能耗高、重金属离子污染、选矿指标不高的现状,有针对性的选用高效、环保、节能的处理工艺及选矿药剂,并成功应用于该矿山生产,取得了显著的经济效益和社会效益。     

酸性化学溶液作用下花岗岩损伤时效特征与机理

以花岗岩为试验与研究对象,借助扫描电镜与电子能谱技术观测分析了酸性化学溶液对花岗岩的宏观形貌、缺陷形态、孔隙结构、矿物元素及孔隙率的改造作用;在不同浸泡时间节点对不同水化学溶液环境下花岗岩试件的质量、弹性纵波波速及溶液的pH值等进行测定,并对浸泡后溶液化学组分与浓度进行离子色谱检测,分析了花岗岩与酸性化学溶液相互作用的损伤时效特征;根据花岗岩矿物组分X射线衍射及化学元素与化合物X射线荧光光谱分析结果,结合化学动力学原理,探讨了花岗岩与酸性化学溶液之间的化学反应过程,以及“水岩相互作用”的岩石化学损伤机理：岩石受水化学溶液侵蚀的损伤机制取决于水化学溶液的性质与成分、岩石中的矿物组分及颗粒、孔隙、裂纹等结构之间的耦合作用,并最终改变了岩石的微观成分和细观结构。     

Investigation of the potential for mineral carbonation of PGM tailings in South Africa

Increasing atmospheric CO₂ concentration is currently of considerable concern in terms of global warming. A possible technology that can contribute to the reduction of CO₂ emissions is its sequestration by mineral carbonation. In this study, tailings from several different platinum mines in South Africa will be mineralogically characterised and their potential for mineral carbonation reviewed. Mg and Ca-rich minerals (plagioclase, olivine, orthopyroxene, clinopyroxene) present in the tailings are good candidates for mineral carbonation, which mimics natural weathering processes in which these minerals react with gaseous CO₂ to form Ca or Mg carbonates. Since the reaction is influenced by particle surface area, the ultra fine grained nature of the PGM tailings provides another reason for the promise of PGM tailings for mineral carbonation. A preliminary ranking of the tailings samples and their efficacy for mineral carbonation has been developed according to whether the samples showed harzburgtic (e.g. Northam Platinum mine), pyroxenetic (e.g. BRPM) or noritic mineral assemblages. This information and understanding will assist in identifying opportunities and guiding the development of engineered facilities for the sequestration of CO₂ by means of mineral carbonation.     

Application of image processing and radial basis neural network techniques for ore sorting and ore classification

Ore sorting is a useful tool to remove gangue material from the ore of bigger size ranges. The radical development in the area of artificial intelligence allows speedy processing the full color digital images for the preferred investigations. In this paper a novel approach to classify the ores for ferromanganese metallurgical plant feed has been proposed based on the visual texture of the ore particles (Mn, Fe, and Al₂O₃ rich) and radial basis neural network. The visual texture of ore particles vary with the mineral contents. This information can be quantified by using image processing technique in RGB color space and, first and second-order statistical analysis. Commonly used Hartlic’s textural features was calculated and presented as neural network inputs along with red, green and blue color values for 5 × 5 pixel size windowpanes extracted from three separate images. Results obtained show encouraging accuracy to apply the approach to develop an expert system for on line ore quality monitoring to control the ore blending in the feed ore circuits as well as separating gangue minerals present in the feed ores. Matlab^® 7.0 was used for visual textural analysis and neural network classification.     

A new industrial mineral: Huntite and its recovery

Huntite is a new industrial mineral. The industrial utilization of huntite is not well known. Huntite formations include different types of minerals such as hydromagnesite, magnesite, clay minerals, aragonite and dolomite. Separation properties of these ores have not exactly been determined yet.In this study, characterization of huntite ores was made and separation conditions for huntite from the associated mineral, magnesite were investigated. The effect of modifying reagents like sodium silicate and carboxymethyl cellulose on surface properties of huntite were also examined. Electrokinetic measurements showed that the surface charge of huntite becomes positive in the presence of MgCl₂ and CaCl₂. On the other hand, carboxymethyl cellulose was found to be a strong depressing agent for huntite in the alkaline region. The result of flotation tests performed with run of mine ore sample, huntite concentrates were produced with 97–98% huntite contents and 76–86% recoveries.