A preliminary rheological classification of phyllosilicate group minerals

With the increased exposure to progressively complex ores, there is growing concern over the effects of phyllosilicate gangue minerals. These minerals present challenges during ore beneficiation, with issues such as reduced flotation performance and complex tailings treatment arising. Often broadly classified as ‘clays’, the understanding of the distinct behaviour of phyllosilicates remains poor. This work focusses on talc, illite and kaolinite, and forms part of an ongoing study which aims at investigating the entire phyllosilicate group, categorised as serpentine, micas; talc/pyrophillite, kaolinites, illites, smectites and vermiculite. Using pure minerals belonging to each phyllosilicate type, a comprehensive surface charge and rheological analysis was conducted, incorporating their charge anisotropy and non-spherical morphology. The mineralogy was discussed, based on pre-existing knowledge of the minerals. Talc, kaolinite and illite suspensions are characterised by high yield stresses and low viscosities, with differences in their behaviour attributed to variations in charge anisotropy, aspect ratio and surface morphology. A comparison with other phyllosilicates showed that muscovite (mica) results in the least rheologically complex suspensions, while the fibrous nature of chrysotile (serpentine) leads to suspensions with the highest yield stresses and viscosities. The other minerals demonstrate intermediate rheological behaviour. Such a classification may be foundational to geometallurgical advances which can enable process performance predictions based on mineralogy.     

Adsorption of copper sulphate on PGM-bearing ores and its influence on froth stability and flotation kinetics

Copper sulphate is used as an activator in the flotation of base metal sulphides as it promotes the interaction of collector molecules with mineral surfaces. It has been used as an activator in certain platinum group mineral (PGM) flotation operations in South Africa although the mechanisms by which improvements in flotation performance are achieved are not well understood. Some investigations have suggested these changes in flotation performance are due to changes in the froth phase rather than activation of minerals by true flotation in the pulp zone. In the present study, the effect of copper sulphate on froth stability was investigated on two PGM containing ores, namely Merensky and UG2 (Upper Group 2) ores from the Bushveld Complex of South Africa. Froth stability tests were conducted using a non-overflowing froth stability column. Zeta potential tests and ethylenediaminetetraacetic acid (EDTA) tests were used to confirm the adsorption of reagents onto pure minerals commonly found in the two ores. The results of full-scale UG2 concentrator on/off copper sulphate tests are also presented. The UG2 ore showed a substantial decrease in froth stability in the order of reagent addition: no reagents > copper > xanthate > copper + xanthate, while Merensky ore showed a slight decrease. It was shown through zeta potential measurements that copper species were to be found on plagioclase, chromite, talc and pyrrhotite surfaces and through EDTA extraction that this copper was in the form of almost equal amounts of Cu(OH)₂ and chemically reacted copper ions on the Merensky and UG2 ore surfaces. In certain cases, the presence of copper sulphate and xanthate substantially increased the recovery, and therefore the implied hydrophobicity, of pure minerals in a frothless microflotation device. It was, therefore, proposed that increases in hydrophobicity beyond an optimum contact angle for froth stability, were the cause of instabilities in the froth phase and these were found to impact grade and recovery in a full-scale concentrator. Differences in the extent of froth phase effects between the different ores can be attributed to differences in mineralogy.     

Understanding the influence of HPGR on PGM flotation behavior using mineralogy

Due to the very fine grained nature and complexity of the platinum bearing ores from the Bushveld Complex in South Africa, numerous processing operations have investigated alternate comminution devices that can be used to liberate the platinum group minerals of the Merensky and UG2 ores at a coarser grind, at reduced energy consumption and increased throughput. In this study, the mineralogy and flotation performance of product from the high pressure grinding rolls (HPGR) was evaluated and compared to a conventional ball mill product with the aim of determining whether the HPGR product could be used for flotation without any further grinding. Results show that for both the Merensky and UG2 platinum ores, the HPGR product showed more fines and less coarse content compared to the ball mill product. No conclusive evidence of preferential liberation was observed for samples prepared by particle bed breakage. The best flotation results were obtained from the ball mill product. The results from this study have shown the definite need for an integrated approach for the interpretation of the results that extends beyond just measurements of valuable mineral liberation.     

Rheological behaviour of lateritic smectite ore slurries

The characterisation and rheology of several nickel laterite smectite ores and pure minerals are compared to assess the effect of mineralogy and particle size on the viscosity of high pulp density slurries. A vane viscometer was used to determine the “optimum pulp density” (OPD) that gave a yield stress of 100 Pa which is considered to be optimal for pumping slurries into autoclaves in the HPAL process. In general, slurries containing finer particles were more viscous and smectite slurries exhibited poor rheological behaviour as compared to slurries of goethite < kaolin < talc < hematite < maghemite < magnesite. Blending the smectite ores with a fraction of the pure minerals improved the rheological behaviour of the pulp and can increase the optimum pulp density of the smectite blend by over 5% w/w.When the physical properties of the smectite ore and slurry were examined, a very good linear correlation was obtained between the optimum pulp density and the settling density which provides a simple measure of predicting rheological behaviour of slurries. The variation in the viscosity of the nickel laterite ores depends largely on their mineralogy and particle size distribution. The mean particle size and P₈₀ values of various smectite ores containing the same mineral phases were also found to have a reasonably good linear correlation with OPD in saline water, but the correlation of ore surface area with OPD was a poorer fit.     

Optical analysis of particle size and chromite liberation from pulp samples of a UG2 ore regrinding circuit

Since the early seventies high chromite and low base metal sulphide (BMS) contents of the UG2 reef imposes technological challenges to mineral processors and extractive metallurgists. Forty years later, particle size distribution and size by size mineralogy are considered as key factors to the continuous improvement of the UG-2 ore metallurgy. With the successful development of ultra fine grinding technologies, a compromise has to be found between fine grinding to achieve platinum group minerals liberation and to avoid the overgrinding of gangue minerals, especially chromite gangue which is detrimental in smelting process. Indeed, fine chromite grains, despite of being naturally hydrophobic mineral, can be recovered in flotation concentrate by entrainment. In addition, overgrinding also increase liberation of naturally floatable gangue (talc) which contaminate the concentrate and need to be controlled during flotation.In this paper, innovative techniques of single particle image analysis from both dry and wet samples have been tentatively used to assess the chromite particle size distribution and the chromite grade of samples taken from a secondary milling circuit. Preliminary results demonstrate excellent potential for online particle imaging making use of both the particle geometry (size, shape) and the optical properties (translucency).     

矿物浮选过程中的交互影响

复杂矿石体系中矿物间难以分离的主要原因是有用矿物的嵌布粒度太细,有用矿物与脉石矿物的共生关系复杂,要实现矿物之间的单体解离,首先必须对矿石进行细磨,从而造成矿石泥化现象以及矿物之间的相互罩盖,进而对矿物的可浮性产生交互影响,导致矿物分离困难。矿物浮选的交互影响是指复杂矿石浮选体系中两种以上矿物间相互吸附、表面转化等对浮选分离产生的影响。因此,要实现复杂矿物体系中有用矿物的选择性分离,首先必须摸清不同复杂矿石体系中矿物之间的交互影响规律,进而找到利用或消除矿物间交互影响的方法,最终达到提高分离选择性的目的。系统阐述了近年来在复杂铁矿石、菱镁矿矿石和钨矿石体系中不同矿物间的浮选交互影响规律的研究成果,以及浮选过程中不同类型复杂矿石中各矿物交互影响的晶体化学和表面物理化学机制,并提出了削弱或促进矿物之间交互影响和适于不同类型复杂矿石浮选分离的方法,建立了复杂铁矿石、菱镁矿矿石和白钨矿矿石中矿物浮选交互影响的理论体系。      

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.     

滑石的晶体化学研究及其在有色金属硫化矿选矿中的浮选现状和实践

滑石是有色金属硫化矿选矿中常见的脉石矿物之一。从研究滑石的晶体结构出发,分析了滑石具有良好的天然可浮性的原因,及对有色金属硫化矿的浮选的影响。目前多采取利用有效捕收剂对滑石进行优先浮选的方法,来减少滑石对后续流程中金属矿物回收的影响。对某滑石含量为13%的铜锌矿进行了滑石优先浮选的应用实践,滑石优先浮选基本脱除了矿石中的易浮脉石,滑石精矿中的铜、锌品位分别为0.17%、0.81%,铜、锌在滑石精矿中的损失率分别为2.11%、2.63%。     

Influence of mineralogy and ore texture on pentlandite flotation at the Nkomati nickel mine,South Africa

The influence of ore mineralogy and ore texture on flotation response was studied for 29 samples from the main mineralised zone at Pit 3 of the Nkomati Ni mine, through laboratory scale flotation testing, laboratory assay, and mineral liberation analyser examination of the ore and the concentrates. The individual sample flotation responses vary widely in terms of Ni grade, and cumulative Ni recovery. It is demonstrated that this is a complex function of ore mineralogy and ore texture. Chalcopyrite is the first sulphide to float, followed by pentlandite and finally pyrrhotite, in ore samples with dominant chalcopyrite, or where pentlandite, pyrrhotite and chalcopyrite occur in equal abundance. However in samples with a high ratio of pyrrhotite to pentlandite and chalcopyrite, pyrrhotite floats earlier than expected, reports to concentrate over the entire flotation period, and depress and extend the flotation of pentlandite over the flotation interval with no clear peak of Ni recovery during flotation. Primary silicates (e.g. olivine and pyroxene) and alteration-related minerals (talc, tremolite and chlorite) are naturally floating, and hence affect the flotation of pentlandite in a similar manner to that of pyrrhotite. The most problematic ore at Nkomati in terms of Ni recovery is characterised by fine disseminated and fine bleb- or net-texture sulphides, contain abundant olivine, pyroxene, amphibole, talc and tremolite, and include abundant metamorphism-related country rock xenoliths (with calc-silicate minerals such as diopside and tremolite).     

Effect of microwave pre-treatment on ultramafic nickel ore slurry rheology

Low-grade ultramafic nickel ores, while representing a large potential nickel resource, are difficult to process due to their high serpentine content. Serpentine is anisotropic and the mineral particles tend to be non-spherical, resulting in challenging slurry rheology. In general, suspensions of serpentine minerals have high viscosity and yield stress, which can be detrimental in comminution and flotation operations. It is proposed that ultramafic nickel ores be treated with microwave radiation prior to grinding in order to reduce slurry viscosity and yield stress. The rheology of two different ultramafic nickel ores, before and after microwave pre-treatment, was characterized in this work. Serpentine minerals were found to dominate the rheology of the untreated ultramafic nickel ores, with the ore containing minor chrysotile exhibiting higher viscosity and yield stress than the ore containing strictly lizardite serpentine. Microwave pre-treatment was found to greatly reduce the shear viscosity (average 80% reduction at 200 s⁻¹) and direct yield stress (peak yield stress reduced by 92–93%) of ultramafic nickel ore slurries. The reduction in slurry viscosity and yield stress of the ore slurries as a result of microwave pre-treatment was attributed to the conversion of serpentine to olivine.     

铜镍硫化矿浮选预脱泥的试验研究

喀拉通克铜镍硫化矿中的滑石及蛇纹石化橄榄石等易浮脉石矿物的存在，严重干扰了铜镍矿物的浮选，不仅增加了药剂消耗，而且影响了浮选指标。通过工艺矿物学和脱泥试验研究，采用新型MB起泡剂浮选预脱泥，减轻了矿泥对锡镍选别的影响，显降低了药剂成本。     

滑石对铜硫矿选矿的影响与典型选矿工艺研究

影响选矿指标和工艺的因素很多,包括矿床类型、矿石性质、矿物组成等矿石本身固有因素,即基因属性,还包括选别过程的磨矿细度、药剂制度、浮选时间等操作因素.针对有色金属矿石中常见的伴生脉石矿物——滑石对铜硫矿选矿的影响进行了探讨和分析,同时针对含滑石铜硫矿的典型选矿工艺进行了梳理和总结.     

从含铜多金属矿中综合回收滑石的试验研究

某含铜多金属矿中,含有大量的易浮滑石,采用先浮细泥滑石,再选铜除杂的工艺流程综合回收滑石产品,既综合利用了矿产资源,又减少细泥滑石对金属矿物选别影响。     

某复杂铜铅锌银多金属硫化矿的综合回收试验研究

某复杂铜铅锌银多金属矿富含多种有价金属元素,但有用矿物嵌布粒度细且不均匀,嵌布关系十分复杂。工艺矿物学研究表明铜矿物主要为黝铜矿,且大部分的银以类质同象赋存在该矿物中,在国内实属罕见。本试验采用优先浮选流程再结合中南大学新型铜捕收剂MT-20及铅捕收剂BITCM,获得了铜精矿品位为18.18%、回收率为81.03%,铅精矿品位为55.56%、回收率为72.63%的工艺指标。全流程闭路试验结果表明该工艺操作方便,指标稳定,各有价金属回收率高,达到了综合回收目的。     

氧化锌矿物的表面性质与浮选关系研究综述

氧化锌矿石结构和共伴生关系复杂,表面性质相似,浮选分离难度较大。氧化锌矿中有用矿物异极矿或菱锌矿在浮选过程中难以与含钙脉石矿物方解石和白云石有效分离。因此,对异极矿、菱锌矿及其含钙脉石矿物的表面性质以及其与浮选行为之间的关系进行深入分析可为其高效浮选分离提供理论基础。系统介绍了异极矿和菱锌矿及其含钙脉石矿物表面性质的研究现状,主要包括矿物的表面断裂键、表面润湿性、表面能、表面电性、表面溶解性等,并评述了矿物表面性质与浮选之间的关系。其中,表面断裂键决定矿物暴露面的活性位点;表面润湿性决定矿物天然疏水性;表面能与矿物吸附药剂能力有关,吸附能越负,药剂与矿物表面的相互作用越剧烈;在浮选过程中,带与矿物表面相反的电荷的捕收剂容易通过物理吸附导致浮选;有用矿物表面溶解的金属离子会活化脉石矿物,导致浮选分离困难。最后,对氧化锌矿物表面性质的未来研究方向进行了展望。     

冬瓜山铜矿深部矿石工艺矿物学研究

冬瓜山铜矿属于复杂难选矿石,具有铜磁黄铁矿、层状滑石、蛇纹石类型矿石占比高的特点,该性质对铜的选别过程具有不利影响,影响铜精矿品位和铜回收率。因此,开展该矿石的矿物学特性研究,对指导选矿生产具有重要的现实意义。研究的主要内容包括:矿石化学成分分析、矿物组成及含量、主要矿物的粒度及嵌布特征分析、不同磨矿细度下重要矿物的解离度分析,并对影响选别指标的工艺矿物学因素进行总结。工艺矿物学研究表明,冬瓜山深部矿石中铜矿物绝大部分为黄铜矿,墨铜矿占8.46%,且含有24.26%的滑石、蛇纹石易浮层状脉石矿物;黄铜矿、墨铜矿、磁黄铁矿、磁铁矿和黄铁矿的嵌布粒度不均匀,尤其是20μm以下部分占11.04%,在磨矿细度-0.074 mm粒级含量占75%时,仍有26.06%与脉石连生。以上性质都是铜选矿的重要影响因素,对指导选矿厂生产具有重要的意义。     

刚果（金）SODIMIKA表层氧化铜钴矿的工艺矿物学研究

为合理开发刚果（金）SODIMIKA表层氧化铜钴矿提供依据,对矿石开展了详细的工艺矿物学研究。结果表明∶① 矿石中主要可回收元素为Cu、Co,含量分别为2.15%、0.19%;铜主要以硅孔雀石中铜、自由氧化铜的形式存在,钴主要以氧化钴、硫化钴的形式存在。② 矿石中主要金属矿物为硅孔雀石、孔雀石、水钴矿、黑铜矿、磷铜矿、锰铜钴水合氧化物及赤（褐）铁矿等;脉石矿物主要为石英、白云母、绿泥石、滑石等。③ 矿石的结构类型主要为半自形—他形粒状结构、自形纤维状结构、鳞片状结构及胶状结构等;构造类型主要为块状构造,其次为角砾状构造及皮壳状构造等。④ 矿石中孔雀石、水钴矿均具不均匀中细粒嵌布的特征,而黑铜矿、磷铜矿、硅孔雀石及锰铜钴水合氧化物则属细粒嵌布。⑤ 铜矿物的产出形式主要为孔雀石、硅孔雀石、黑铜矿、磷铜矿、锰铜钴水合氧化物等,结合氧化铜矿物含量较高,且与褐铁矿共生现象严重;钴的独立矿物为水钴矿,且嵌布粒度微细,独立不规则粒状分布,与孔雀石复杂连生。推荐采用浮—磁联合工艺,浮选回收部分粗粒单体的自由氧化铜矿物,磁选回收比磁化系数较高的、与氧化铁锰紧密结合的铜钴。     

梅山铁矿硫浮选原矿和硫精矿的工艺矿物学研究

针对梅山铁矿硫浮选所得硫精矿品位不高和硫回收率较低的问题,运用矿物解离分析仪（MLA）测试与化学分析、XRD分析等相结合的手段,详细研究了浮选原矿和硫精矿中硫矿物的工艺矿物学特征,重点分析了浮选回收主要矿物黄铁矿的嵌布特征、粒度及解离特性等,查明了浮选原矿粒度较粗、黄铁矿单体解离不充分是其浮选选别指标较差及浮选铁尾矿中硫含量较高的主要原因,提出了浮选粗精矿再磨再选的建议,为梅山铁矿浮硫工艺流程优化提供了理论依据。      

The influence of phyllosilicate mineralogy on the rheology of mineral slurries

Phyllosilicate minerals have been shown to present some rheological challenges during ore beneficiation, with difficulties such as reduced flotation rates and complex tailings treatment arising. This study focuses on two phyllosilicate minerals which commonly exist as major gangue components in many industrial ores: muscovite with its thin platy structure and vermiculite which exhibits concertina-like swelling behaviour.The surface charge distribution of the minerals is evaluated using electrokinetic zeta potential measurements and potentiometric titrations. Rheology tests give the plastic viscosities and Bingham yield stresses of the suspensions. The results show that muscovite and vermiculite particles have an apparent negative charge due to the high aspect ratio of the negatively charged tetrahedral faces to the edges within a tetrahedral-octahedral-tetrahedral (T-O-T) layer configuration. The charge separation between the edges and faces results in the non-typical stacking behaviour of muscovite and vermiculite particles, forming suspensions with higher Bingham yield stresses than quartz, a non-phyllosilicate isotropic mineral with a regular non-platy morphology. However, upon yielding, these structures are destroyed and the resultant suspensions are characterised by low Bingham viscosities similar to isotropic minerals.This study provides a preliminary understanding of the flow behaviour of muscovite and vermiculite.     

The effect of ore blends on the mineral processing of platinum ores

This paper investigates whether blends of platinum ores display linear grinding and flotation characteristics or whether non-linear effects occur, i.e. synergistic/antagonistic effects. Ores from four different shafts are used in the study, i.e. Salene, Waterval UG2, Paardekraal and Townlands. Laboratory grinding and flotation tests are conducted on blends of the four ores using a statistical simplex lattice mixture design. Grinding results show no evidence that blends of ores display non-linear grinding characteristics. Flotation results show significant antagonistic effects in binary blends of the Salene ore with the other ore types. On the other hand, ternary/quaternary blends of ores result in synergistic effects. The study concludes that blends of platinum ores display non-linear (non-additive) characteristics when there are large differences in metallurgical properties between the ore types. The study demonstrates that appropriately designed mixtures experiments are an effective way to study the performance of ore blends in the laboratory.