Removal of lead minerals from copper industrial flotation concentrates by xanthate flotation in the presence of dextrin

Potato starch and dextrins resulting from thermolysis of potato starch in the absence of reagents and presence of -amino acids are promising depressants for separation of lead and copper minerals present in the Polish industrial copper concentrates. The polysaccharides were used for differential xanthate flotation of the final industrial concentrates produced by flotation with sulfhydryl collectors in the absence of depressants. The polysaccharides depressed galena and provided froth concentrate rich in chalcocite and other copper minerals as well as cell product containing lead minerals. The best results of separation were obtained in the presence of plain dextrin prepared by a thermal degradation of potato starch. The industrial concentrate containing 18.5% Cu and 5.5% Pb was divided into a froth product containing 38.1% Cu with 77% recovery of copper and a cell product assaying 7.3% Pb with 83% recovery of lead. It was accomplished using 2500 g/t of dextrin, 50g/t of potassium ethyl xanthate, and 50 g/t of frother (α-terpineol). The pH of flotation was 8.0–8.2.     

The effect of thermal treatment on the flotation of chrysocolla

Flotation studies using a Hallimond tube have been carried out on purified samples of chrysocolla. The results confirm that by heating the sample to 550°C, flotation of the sulphidized sample with amyl xanthate is considerably improved. Flotation with sodium dodecyl sulphate is also considerably higher. The recovery with cationic collectors is not modified by the thermal treatment.Electrophoretic mobility measurements and flotation studies using benzene instead of air for the collection of the particles suggest that the increase in flotation after thermal treatment is a consequence of (1) an increase in the solubility of copper ions and their adsorption on to the surface of the particles, and (2) an increase of the intrinsic hydrophobicity of the particles due to condensation of some of the free silanol groups on their surface.     

Studies on the flotation of sulphides. II. The effect of urea on the flotation of zinc sulphide

The effect of three hydrophilic non-electrolytes on the flotation of ZnS has been studied using a Fuerstenau microflotation cell. The rate of flotation increases with increasing concentrations of urea(OC(NH₂)₂), but is unaffected by thiourea and slightly decreased by sucrose. This effect of urea was observed with all samples of ZnS (synthetic and natural) studied, is unaffected by extensive purification of the urea and by the presence or absence of O₂, and is reversed by dilution. Urea also increases the rate of flotation (in a Partridge and Smith cell) in the absence of frother. Surface tension measurements showed the absence of detectable concentrations of surfactants in the urea. The presence of urea has no effect on the rate of sedimentation (i.e. on the degree of aggregation) of ZnS or on the volume of water carried over during flotation. It is suggested that the effect of urea is (at least in part) to increase the rate of bubble-particle attachment by modifying the structure of water.     

The effect of hydrodynamic conditions on true flotation and entrainment in flotation of a complex sulphide ore

The separation efficiency and selectivity of flotation are directly proportional to recoveries of the mineral species in the feed due to true flotation and entrainment. In this study, effects of the hydrodynamic conditions on true flotation and entrainment were investigated by using a fractional factorial experimental design. A method previously described in the literature was applied to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore. In order to apply the method, the kinetic flotation tests were conducted under various hydrodynamic conditions defined by some physical variables. Some of these tests were conducted in the presence and absence of a collector to evaluate the self-induced floatability. The selectivity index of the mineral species for entrainment was seen to be suitable evaluation of the non-selectivity and efficiency of the entrainment. Furthermore, the results of the size-by-size analysis of the froth products indicated that the presence of the self-induced hydrophobic particles in the feed is as important as the presence of very fine particles for accurate estimation of true flotation and entrainment in flotation of a complex sulphide ore. In addition, the estimated results for entrainment in flotation of the complex sulphide ore can be misleading. Therefore, a new approach would be necessary to determine the contributions of true flotation and entrainment in flotation of a complex sulphide ore.     

The effect of particle shape and hydrophobicity in flotation

The effect of particle shape on the flotation process has been investigated in laboratory experiments with monosized spherical ballotini and ground ballotini. The particles were treated by partial methylation with trimethylchlorosilane to achieve varying degrees of hydrophobicity. In flotation, the process of film thinning and liquid drainage is critical in the formation of stable bubble–particle attachments and this is affected by the particle shape and surface hydrophobicity. Flotation tests with different particle sizes were conducted in a modified batch Denver cell. Predictions from a computational fluid dynamic model of the flotation cell that incorporates fundamental aspects of bubble–particle attachment were compared with data from flotation tests. Contact angles of the particles were measured using a capillary rise technique to indicate surface hydrophobicity. Ground ballotini generally has higher flotation rates than spherical ballotini; the results are consistent with effects from faster film thinning and rupture at rough surfaces and are well correlated by the sphericity index.     

The effect of bubble size on the rate of flotation of fine particles

Flotation experiments have been carried out in a cell in which bubbles of known size could be generated independently of the turbulence levels, which could be controlled by varying the impeller speed. The mean bubble size ranged from 75 μm to 655 μm.Results are reported for the flotation rates of fine particles, less than 50 μm diameter. The materials floated were polystyrene latex particles, quartz and zircon. These were chosen to give a wide range of specific gravity.It was found that the flotation rate was very strongly affected by the bubble size, there being an increase of up to one hundred-fold when the bubble size was reduced from 655 μm to 75 μm. Effects of particle density and impeller speed are also reported.     

Studies on the flotation of sulphides. I. The effect of Cu(II) ions on the flotation of zinc sulphide

The effect of Cu(II) ions on the froth flotation of ZnS in the absence of any collector has been studied in a Fuerstenau microflotation cell. The flotation of pure synthetic ZnS, in both cubic and hexagonal modifications, can be greatly enhanced by the adsorption of traces of Cu(II) ions. In the case of cubic ZnS, the “activating” effect of Cu(II): (a) involves the stoichiometric replacement of one Zn(II) ion in the lattice by one Cu(II) ion from solution at a rate which is independent of pH (1–5); (b) is noticeable at coverages corresponding to as little as 0.1% of a monolayer, reaches a maximum at coverages of 2–100% of a monolayer, and decreases again at higher coverages; (c) is unaffected by the presence or absence of O₂, by variation of the pH of flotation (6–10), by heating in vacuum at 250°C for two hours or by storing in the dry state for over one year; and (d) does not appear to involve any significant change in surface area or in the state of aggregation of the particles.     

The joint effect of rank and grain size on the flotation of Australian bituminous coals

Laboratory batch flotation tests were carried out to determine the effect of grain size on the recovery of four Australian bituminous coals of high and low rank. The flotation concentrates, taken over successive time intervals, and the tailings, were sized and the recovery-size curves plotted. A method was developed for determining the proportions of liberated and composite grains in the various flotation products. Flotation tests were carried out in the presence of methylisobutylcarbinol (MIBC) and MIBC + kerosene. The shapes of the recovery-size curves depended on the rank of the coal and whether or not kerosene was present. The variation of the recovery with size was explained in terms of the joint effect of rank and size on the floatability of composite grains.     

云南某微细粒辉钼矿工艺矿物学与浮选回收技术研究

针对云南某单一的低品位硫化钼矿,辉钼矿嵌布粒度粗细极不均匀,微细粒含量高的特点,进行了工艺矿物学与浮选回收技术研究.采用原矿粗磨—钼粗精矿再磨的阶段磨浮选矿回收工艺,以水玻璃和硫化钠做脉石矿物的抑制剂,以煤油和2#油分别作辉钼矿的捕收剂和起泡剂,对原矿Mo品位0.22％,全流程浮选闭路试验获得了钼精矿含M050.12％,回收率92.73％的浮选指标,浮选回收工艺流程合理、药剂制度简单环保.     

硫化矿浮选粗精矿再磨工艺对矿物表面性质的影响

随着矿产资源开发利用程度的逐年加剧,目前大部分有色金属选厂处理的都是品位低、嵌布粒度细的复杂多金属矿,为提高有价金属的选矿回收率、降低磨矿成本,大部分选厂都采用"阶段磨矿、阶段选别"工艺,其中以浮选粗精矿的再磨最为常见.硫化矿浮选粗精矿的再磨可显著提高磨矿效率及目的 矿物解离度,但生产实践中大部分选厂仅关注目的 矿物的解离度,而忽视了硫化矿浮选粗精矿再磨过程中磨矿介质、磨矿方式、矿浆电化学环境等多种因素对矿物表面性质及浮选行为的影响.文章系统总结了硫化矿浮选粗精矿矿物组成特点及矿浆化学性质的基础上,综述了硫化矿浮选粗精矿再磨过程中磨机类型及磨矿方式、磨矿介质材质及形状、矿浆电化学环境、药剂浓度等多种因素对再磨后矿物表面性质及浮选行为的影响规律,指出通过精矿再磨工艺参数及矿浆电化学环境的合理优化调整,增强矿物表面间的亲水/疏水性差异,提高精选分离效果应是未来硫化矿浮选粗精矿再磨研究关注的重要方向.     

The effect of slime coatings of the serpentine minerals,chrysotile and lizardite,on pentlandite flotation

Serpentine minerals in the gangue often interfere with the concentration of nickel sulfide ores. The influence of slime coatings of the serpentine minerals chrysotile and lizardite on the flotation of unoxidized pentlandite has been studied. In addition to microflotation testing at pH 9 with potassium amyl xanthate collector, electrophoresis and scanning electron microscopy have been used. The formation of a slime coating was found to be directly related to the surface charges on the slime and the sulfide mineral. Chemical additives which modified the slime surface charge, such as carboxy methyl cellulose, dextrin, sodium pyrophosphate and sodium silicate, were shown to be effective in reducing the adverse influence of the slime on the flotation of pentlandite.     

The electrokinetic properties and flotation behaviour of apatite and calcite in the presence of dodecylamine chloride

Electrokinetic and flotation studies on apatites and calcite show that under certain conditions these minerals are floatable with dodecylamine chloride (DDACl) and the possible mode of DDACl adsorption is due to Coulombic and Van der Waals forces. The results indicate hemi-micelle formation of dodecylamine ions and suggest involvement of neutral molecular amine in the hemi-micelle structure, the critical hemi-micelle concentration being influenced by the nature of charge at the mineral surface.     

The surface chemistry and flotation of scheelite,II. Flotation “collectors”

The mechanism of flotation of calcium tungstate with non-complexing ionic surfactants has been examined. With fatty-acids, precipitation of the calcium soap sets in at very low concentrations. None of the conventional reagents alone provides sufficient selectivity to permit separation of scheelite from calcite.As an example of a possible chelating collector for tungstate minerals, 4-tertiary butyl catechol (4 TBC) was examined. Although such reagents are, indeed, adsorbed and induce floatability, they are useless as collectors, for several reasons. For example, 4TBC was found (unexpectedly) to be more strongly adsorbed by calcite than by scheelite; furthermore, soluble tungsten complexes were also formed.     

The effect of air flow rate on the kinetics of flotation. Part 3: Selectivity

The flotation rate from the slurry to the froth of a strongly hydrophobic galena and weakly conditioned chalcopyrite were determined in a batch experimental flotation cell, as a function of air flow rate (AFR). The selectivity of the transfer from the slurry to the froth was found to be highest at intermediate AFR, and lowest at very low or very high AFR. The flotation rate of a strongly conditioned magnetite-galena mixture was investigated in the same cell as a function of AFR and froth thickness (FT). The rate constant which characterizes the transfer rate from the froth over the cell lip was found to be identical for both minerals within experimental errors.     

Galvanic interaction between grinding media and arsenopyrite and its effect on flotation: Part II. Effect of grinding on flotation

Arsenopyrite floatability was correlated with the galvanic current, calculated from polarization curves measured during grinding, as well as the amount of oxidized iron, measured by EDTA extraction, in the mill discharge. The adverse influence of galvanic interaction during grinding on arsenopyrite floatability was quantified.     

Effect of surface oxide/hydroxide products on the collectorless flotation of copper-activated sphalerite

The change in collectorless flotation of sphalerite with pH and Cu(II) concentration was correlated with the type and proportion of species present on the sphalerite surface. The solution and surface species were determined using a combination of analytical techniques including zeta potential measurement and X-ray photoelectron spectroscopy. An optimum copper concentration for maximum sphalerite flotation was identified, beyond which flotation decreased. This decrease in flotation coincided with the precipitation of copper hydroxide in neutral to mildly alkaline pH conditions. The hydrophobic polysulfide and hydrophilic copper hydroxide species were the main surface species influencing sphalerite flotation.     

泥沙颗粒表面电荷特性及其对干容重影响试验研究

采用黄河及长江中的沙样在不同Ca2+浓度下分别进行电位滴定试验和干容重试验,得到以下结论:①随Ca2+浓度的增加,泥沙颗粒表面负电荷先不断减少然后趋于不变。②Ca2+对泥沙淤积干容重的影响可分为三个阶段:第一阶段干容重减小;第二阶段增加并达到最大值;第三阶段减小最后趋于不变。③在Ca2+浓度相同条件下,泥沙浓度对淤积干容重的影响根据所加Ca2+浓度不同也呈现不同的变化。④Ca2+浓度、泥沙浓度相同时,中值粒径越大干容重越大,且中值粒径大的泥沙干容重达到最大值所需Ca2+少。⑤在不同Ca2+浓度下泥沙颗粒由于表面电荷不同造成静电斥力不同,同时表面水膜作用力也不同,二者共同作用使得干容重体现不同的变化。     

The effect of surface slope on saltation threshold

A new wind tunnel has been constructed to study the mass transport properties of wind-blown sand. This report on the first set of experiments in the new wind tunnel concerns the effect of slope on threshold friction speed. The results of this series of static threshold experiments (and one dynamic threshold experiment) for a range of particle diameters and bed slope angles show that, provided the effects of Reynolds number variation and interparticle cohesive force are accounted for, the static friction angle α is independent of slope and close in value to the measured static angle of response.     

辉钼矿Re-Os同位素定年方法的改进与应用

公认的Re-Os同位素定年代表物辉钼矿,目前已在金属硫化物矿床年代学研究领域获得了广泛的应用。本研究采用浓HNO₃分解辉钼矿样品,大大地简化了Re和Os的化学制备过程,并根据辉钼矿中正常Os含量水平相对放射成因¹⁸⁷Os可以忽略的特点,以正常Os标准为稀释剂,实现了仪器测量过程中Os同位素质量分馏的在线校正,改善了分析数据的质量。该方法经辉钼矿国家标准物质进行验证,获得了满意的Re、Os含量及Re-Os年龄数据,并且在南岭地区与连阳复式岩体相关的姓坪夕卡岩型钼矿床成矿年龄研究中获得了成功应用。在实际应用中,为了获得有意义的能反映真实地质事件的年龄数据,辉钼矿样品不仅要有足够的取样量,而且还要保证粒度细、混合均匀。     

Metal island growth and dynamics on molybdenite surfaces

In order to understand the adsorption mechanism of metal atoms to semiconducting surfaces, we have studied, as a model system, the vapor phase adsorption of Ag, Au, and Cu on the (001) surface of molybdenite (MoS₂) and the subsequent surface diffusion of these adsorbates. Our scanning tunneling microscopy (STM) images show that, depending on the type of metal atom that is adsorbed, islands of a characteristic size (2 nm for Ag, 8 to 10 nm for Cu, two distinct sizes of 2 nm and 8 to 10 nm for Au), shape (well rounded in the lateral extension) and thickness (one monolayer for Ag, 1 to 1.5 nm for Cu) are formed during the initial stages of deposition. Whole islands are observed to surface diffuse without loss of size or shape. Despite the relatively large size of the copper islands on molybdenite, these islands surface diffuse extensively, suggesting that the Cu-S interaction is weak. Surface diffusion is only hindered once individual islands start to coalesce. As copper islands accumulate, the size and shape of the original islands can still be recognized, supporting the conclusion that these characteristics are constant and that monolayer growth occurs by the aggregation of islands across the surface.The strength and the nature of the Ag-S(MoS₂) bond were further investigated by using molecular orbital calculations, ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS). By applying quantum mechanical approaches using a two-dimensional periodic molybdenite slab and hexagonal MoS₂ clusters of different sizes with metal atoms adsorbed to them, it is possible to calculate the electron transfer between the mineral surface and the metal atom as well as the adsorption energy as a function of surface coverage. In addition, we used the results from the quantum mechanical runs to derive empirical potentials that model the characteristics of the forces within the crystal, within the adsorbed islands, and the metal and mineral surface. The combination of quantum mechanical calculations and empirical force field calculations explain the electronic structure and the highest stability of Ag islands that have seven atoms in diameter, which exactly agrees with the size of experimentally observed islands. UPS results also suggest that a specific new state is formed (approximately 4.5 eV into the valence band) which may describe the Ag-S bond because it does not occur in pure silver or molybdenite.This study shows how the combination of microscopic (STM), spectroscopic (STS, UPS), compositional (X-ray photoelectron spectroscopy, XPS) and molecular modeling (quantum mechanical and empirical) techniques is a useful approach to understand the nature of the metal to sulfide bond. Further insights may be gained concerning the natural association of certain metals with sulfides.