Beneficiation of the Nechalacho rare earth deposit: Flotation response using benzohydroxamic acid

Rare earth minerals (REM) may be beneficiated using a variety of separation techniques with froth flotation being the most commonly applied in operating REM separation plants. Many different collectors have been tested with traditional REM such as bastnäsite. The most successful are the hydroxamic acids. The Nechalacho deposit contains many REM for which there is minimal processing information in literature. Thus, experimental investigation into their flotation behaviour is required.This work focuses on understanding the effect of a benzohydroxamic acid collector on the flotation of a REM enriched pre-concentrate from the Nechalacho deposit (after lab-scale gravity and magnetic separation steps). The lab-scale flotation response of the REM is quantified using mass recoveries, water recoveries, QEMSCAN and chemical assay data and TOF-SIMS in order to study the recovery, entrainment and kinetics of different REM. Three different flotation schemes are investigated to determine the effect of a secondary addition of collector as well as the addition of lead ions, a known activator in hydroxamic acid flotation. It is important to note that the goal of this work is to determine fundamental flotation properties of the different REM in the Nechalacho deposit. As such, the process investigated here is not indicative in any way of the current process design for this deposit.     

A Tof-SIMS analysis of the effect of lead nitrate on rare earth flotation

The influence of lead nitrate on rare earth flotation in the presence of hydroxamates as collectors has been investigated by a combination of micro-flotation tests and time of flight secondary ion mass spectrometry (ToF-SIMS) surface chemical analysis. Micro-flotation tests identified a link between lead nitrate dose and an improved grade of REE minerals for concentrates. The testing also identified differences in the flotation behaviour of light rare earth (LREEs, La or Ce bearing minerals) and Y and Zr bearing minerals. TOF-SIMS analyses evaluated the variability in surface components on undifferentiated REE grains from the concentrates and tails samples in response to the varied lead nitrate dosing in micro-flotation tests. The surface analyses showed that both the REE grains and gangue phases reporting to the concentrate have higher relative surface proportions of both Pb and collectors as compared to those reporting to the tails. It is noted that the lead does not appear to be associated with an increase in collector adsorption, so the grade of REE can go up is not by selective adsorption of collectors. The significantly higher intensity of Pb species identified on the surface of the concentrate would suggest that lead addition can actually reverse the surface charge making it efficient for collectors to adsorb onto surfaces that they could not easily close to. It is also possible PbOH⁺ potentially acting as a point activator.     

某低品位稀土矿浮选工艺的改造实践

四川省某轻稀土矿山,原矿伴生萤石、重晶石及等多种有用矿物组分,原有选别原则流程分为稀土重选、稀土浮选、重晶石浮选和萤石浮选四个模块。该工艺方案稀土浮选与重晶石萤石浮选属于两套独立的生产系统,同时,又不可避免地存在着稀土浮选精矿品位与回收率受重晶石萤石浮选的回水相互影响等因素,导致了自投产以来稀土品位与回收率均未能达到设计指标。为此,选矿厂对流程开展了许多长期的考查与改进,对稀土浮选工艺进行其它方案可行性研究。最终确立新的工艺方案将独立的稀土浮选取消,形成了重晶石优先浮选,后稀土与萤石混合浮选,再通过湿式高梯度磁选作业回收浮选精矿中稀土的工艺。新的工艺最终达到了重选加浮选稀土综合回收率到72%以上,浮选精矿ROE品位65%以上的良好指标。     

柠檬酸对铌铁矿和石英浮选分离的影响

柠檬酸是氧化矿和脉石矿物浮选分离中非常有效的抑制剂。针对白云鄂博矿中铌矿物难以回收的现状,使用OHA作为捕收剂,六水氯化铁为石英活化剂,柠檬酸为抑制剂,研究抑制剂对铌铁矿和石英的浮游特性的影响。柠檬酸作为抑制剂对铌铁矿和石英人工混合矿的最佳浮选分离条件：OHA用量为0.05 mmol/L,六水氯化铁用量为20 mg/L,柠檬酸用量为0.1 mmol/L,pH=9,获得的铌铁矿精矿中Nb₂O₅回收率为76.03%、Nb₂O₅品位为58.38%,实现了铌铁矿和石英的高效浮选分离。采用Zeta电位、接触角测试、X射线光电子能谱分析(XPS)揭示了药剂在矿物表面的作用机理,为铌铁矿和石英的高效分离提供理论依据,并为将其应用到实际生产中提供技术支撑,同时丰富铌铁矿浮选抑制剂体系。     

The flotation separation of scheelite from calcite using a quaternary ammonium salt as collector

The flotability of scheelite and calcite was studied with Dioctyl dimethyl ammonium bromide (BDDA). The experiments were conducted on individual and mixed minerals as a function of pH with a micro-flotation cell. And oleic acid was tested for comparison. The flotation results revealed that the performance of BDDA is better than that of oleic acid and the best separation could be achieved with BDDA over the pH range 8-10. Through preliminary analysis, it is concluded that BDDA reacts with scheelite through electrostatic interaction.     

某富铁型稀土矿中稀土分离富集研究

国外某富铁型稀土矿中铁、稀土矿物嵌布关系复杂、连生包裹紧密,采用单一浮选工艺分离困难,本文通过优选铁矿物选择性抑制剂和稀土矿物捕收剂,形成适于该矿石分选的浮选降铁-磁选除杂的选矿工艺。研究结果表明,针对REO品位为2.95%, Fe₂O₃含量40.30的稀土矿样品,以RF-10为铁矿物抑制剂、RFS为稀土矿物捕收剂,经浮选降铁-磁选除杂工艺可以得到REO品位为36%的稀土精矿产品,铁矿物脱除率达95%,论文研究成果为含铁稀土矿的有效利用提供借鉴。     

柠檬酸在蛇纹石/镍黄铁矿浮选分离中的作用

通过浮选实验、沉降实验、吸附量实验、Zeta电位测试和DLVO理论计算,考察柠檬酸在蛇纹石/镍黄铁矿浮选分离中的作用,分析柠檬酸的作用机理。结果表明：在弱碱性pH条件下,蛇纹石的加入降低了镍黄铁矿的回收率,而柠檬酸处理后的蛇纹石不会影响镍黄铁矿的浮选。机理分析表明：蛇纹石与镍黄铁矿表面带有相反电荷,能通过静电作用罩盖在黄镍铁矿表面,影响其浮选;柠檬酸能够溶解蛇纹石表面荷正电的镁离子,使蛇纹石表面电位发生变化,此时,蛇纹石与镍黄铁矿之间存在较强的排斥作用,从而减弱蛇纹石在镍黄铁矿表面的附着,消除其对镍黄铁矿的抑制作用。     

Cu-S flotation separation via the combination of sodium humate and lime in a low pH medium

The flotation separation of chalcopyrite and pyrite was studied in the presence of sodium humate. The results of flotation tests indicated that pyrite can be selectively depressed by sodium humate, and the activity of sodium humate was strongly affected by the pH of the pulp. At high pH values, pyrite was strongly depressed by sodium humate; however, the content of chalcopyrite was not affected. Ore flotation tests were successfully conducted in the laboratory and at the Dexing Copper Mine by applying sodium humate as a pyrite depressant. By adding 40-60 g/t of sodium humate to the pulp and adjusting the pH to 10-10.5 with CaO, a concentrate with a Cu content of 24% was obtained without reducing the Cu recovery rate. In addition, the dosage of CaO was reduced, and the recovery of Au, Ag and Mo in the copper concentrate was enhanced due to the reduced pH of the pulp. The zeta potential, adsorption of xanthate and contact angle of the mineral surface were measured, and the results from surface measurements indicated that there was a strong hydrophilic interaction between sodium humate and the surface of pyrite. Moreover, the results revealed that the interaction between sodium humate and chalcopyrite was weak. Infrared (IR) spectra of pyrite and sodium humate were obtained, and the results indicated that sodium humate was chemically adsorbed on the surface of pyrite.     

Study on separation of heavy rare earth elements by solvent extraction with organophosphorus acids and amine reagents

The present work describes a study of the separation of rare earth elements (REE) from heavy REE concentrate through solvent extraction. Seven extractants were investigated: three organophosphorus acids (DEHPA, IONQUEST^®801 and CYANEX^®272), a mixture of DEHPA/TOPO (neutral ester) and three amines (ALAMINE^®336, ALIQUAT^®336 and PRIMENE^®JM-T). The organophosphorus extractants were investigated in hydrochloric and sulphuric media whereas the amines performance was assessed in a sulphuric medium. The variables investigated were: concentration of the extractant agent, aqueous phase acidity, aqueous/organic volumetric ratio, contact time, stripping agent concentration (hydrochloric acid solution) and the selective stripping step. In the extraction step, the best separation factors for the adjacent elements were obtained with DEHPA and IONQUEST 801. For 1.0 mol L⁻¹ DEHPA in an initial acidity of 0.3 mol L⁻¹ H⁺, the separation factor was 2.5 Tb/Dy, 2.1 Dy/Ho, 1.9 Ho/Er, 2.0 Ho/Y and 1.1 Y/Er; for 1 mol L⁻¹ IONQUEST 801 in 0.3 mol L⁻¹ of H⁺ it was 2.7 Tb/Dy, 2.4 Dy/Ho, 2.1 Ho/Er, 2.1 Ho/Y e 1.5 Y/Er. The study concluded that for the extractants investigated, IONQUEST 801 is the most indicated for the separation of heavy REE because it has lower affinity with the REE compared to the affinity of DEPHA/REE, which makes the strip of the REE from Ionquest 801 easier than from DEHPA. Moreover, the number of stages necessary for the stripping of the REE from IONQUEST 801 is much lower than that observed when DEPHA is employed.     

岩溶区某稀土分离厂地下水环境影响预测

稀土分离项目废水成分复杂,且污染物浓度高,废水一旦进入地下水,将造成难以修复的污染。本文针对岩溶区某稀土分离厂废水泄漏污染地下水问题,采用数值模拟方法,针对防渗膜完好、防渗膜破裂、岩溶塌陷三种情景预测了污染物氯离子在岩溶含水层中的时空分布情况。结果表明:防渗膜能有效防止地下水污染,一旦破裂,在30a的模拟期内,污染物将运移至厂区外,岩溶塌陷情景下,厂区周边地表水、地下水均将会被污染。研究结果可为岩溶区的地下水污染预测提供一定的借鉴。     

The dependency of the critical contact angle for flotation on particle size - Modelling the limits of fine particle flotation

The flotation behaviour of fine particles is studied in this work. Fine methylated quartz particles within the size range from 0.2 to 50 μm, and with varying contact angles, were floated in a mechanical flotation cell. Results indicate that particles of a given size need to possess a minimum critical contact angle, which increases in value as particle size decreases, for flotation to be initiated. As a consequence, a non-floating component exists within a given size fraction. This is interpreted as a fraction consisting of particles below the critical contact angle for flotation for that size. The critical contact angle for flotation is explained in terms of the existence of an energy barrier for bubble-particle attachment. The flotation results are interpreted by means of [Scheludko et al., 1976] and [Drelich and Miller, 1992] models for the floatability of fine particles. The experimental data compared very well with calculations using the Drelich and Miller equation, allowing extension to the prediction of the critical contact angle for flotation down to particle sizes well below the previous limits investigated, bridging the gap existing in the literature.     

The effect of flotation and parameters for bioleaching of printed circuit boards

Waste electrical and electronic equipment (WEEE) is currently one of the fastest growing waste streams in the world. Typical for WEEE is the high content of valuable and precious metals, as well as harmful contaminants like halogens, flame retardant chemicals and plastics. Currently, WEEE treatment and metal recovery methods are imperfect, polluting and energy intensive. In this paper, novel treatment possibilities are outlined for printed circuit boards (PCB) utilizing both the flotation separation technique and acid bioleaching. Flotation, conducted after crushing and sieving of PCB, produced two fractions: metal-rich concentrate, which is more suitable for pyrometallurgical treatment than untreated PCB, and metal-poor froth suitable for acid bioleaching. It was seen that especially low pH (1.6), high initial Fe²⁺ concentration (7.8 g/l) and low PCB froth concentration in the bioleaching solution (50 g/l) were beneficial for the rapid and selective dissolution of copper. With these parameters, 99% of copper was solubilized from PCB froth in bioreactor treatment, with Cu (6.8 g/l) and Fe (7.0 g/l) being the only major metallic elements in bioleaching solution.     

基于粒度对混合稀土纯矿物浮选过程影响分析

以包头白云鄂博混合稀土纯矿物为研究对象,通过对不同粒度混合稀土纯矿物浮选及其动力学行为探索,研究了矿物粒度对浮选过程的影响。结果表明:混合稀土精矿的动力学与一级动力学模型的匹配度最高,同时不同粒径的颗粒对矿物浮选行为产生较大的影响。在混合稀土纯矿物分批刮泡粗选中,-40+10μm颗粒的浮选速率常数及REO的最大回收率均大于-10μm和+40μm颗粒;而对于混合稀土纯矿物一次粗选、三次精选浮选流程来说,随着精选次数的增加,可浮性优的颗粒(-40+10μm粒级)在浮选精矿中的富集程度逐渐增大,并且在第3次精选精矿中其比例远高于可浮性差的颗粒(+40μm粒级和-10μm粒级)。因此,对于白云鄂博稀土纯矿物浮选来说,-40+10μm颗粒可浮选性优于+40μm和-10μm颗粒。通过对白云鄂博稀土混合矿粒度在浮选过程的研究,为其浮选工艺提供了有力的理论依据。     

草酸沉淀稀土废水的治理现状

阐述了稀土冶炼过程中的草酸沉淀稀土废水的来源、成分和处理现状,介绍并总结了现有的各种处理方法,提出了对草酸沉淀稀土废水治理的建议。     

稀土络合萃取体系的研究现状及其展望

溶剂萃取法是目前稀土生产的主要方法,具有操作简单、处理量大、生产效率高等优点。但在使用溶剂萃取法生产稀土的同时会产生大量的氨氮废水,对环境影响巨大。为了更加高效、绿色地生产稀土,络合萃取分离技术受到关注并被应用于稀土的生产和分离。络合萃取体系增加了稀土萃取时的纯化分离能力,减少了氨氮废水的产生。介绍了稀土络合萃取体系中常用的络合剂,以及通过不同络合剂建立的不同络合萃取体系的研究现状,分析了其优劣性。对目前稀土络合萃取体系研究和发展存在的问题进行了总结,并展望了稀土络合萃取体系的未来发展方向。 关键词：稀土;络合剂;络合萃取体系;绿色生产     

Estimation of platinum flotation grades from froth image data

Features extracted online from froth images on flotation plants are potentially useful to the development of advanced control for flotation systems, provided that these features can be related to the key indicator variables of the plant, such as valuable metal loadings and recovery. Although such relationships have been established in a number of base metal plants in industry, this is not the case in the platinum industry. In this paper, estimation of flotation grades and recoveries from froth image data is therefore considered based on laboratory and industrial plant data. It is shown that grades and recoveries can be reliably estimated from a number of different features by use of linear and nonlinear models. This includes simple colour information that on the industrial plant showed a strong correlation with grade measurement.     

On the detachment of hydrophobic particles from the froth phase

We conducted an experimental study to investigate the behaviour of hydrophobic particles in the froth phase of a laboratory column. A stable froth was formed by passing the air through a porous disk into the liquid containing frother. Individual bubbles were loaded with hydrophobic particles separately in a fluidised bed and allowed to rise into the froth layer. Particles dislodged from the froth were collected and measured. The effect of collector concentration and superficial gas velocity on the detachment of particles from the froth was studied. The results showed that fraction of particles detaching from the froth decreases exponentially with increase in the collector concentration and increases slightly with superficial gas velocity. In general, low froth dropback values were obtained for the conditions studied in the present system which are considerably lower than the previously reported values.     

The effect of using different comminution procedures on the flotation of Platinum-Group Minerals

The use of High Pressure Grinding Rollers (HPGR) has been widely reported to have major benefits in the treatment of minerals such as iron ore and diamonds. To date there have been few investigations into its use in the treatment of ores containing Platinum-Group Minerals (PGMs). HPGRs are known to reduce energy consumption and wear costs and improve the throughput in the circuit. In the present investigation the effect of the comparative use of HPGR and conventional crushing in combination with either dry or wet rod milling on the flotation of PGMs was studied using batch flotation. Previous studies of a base metal sulphide had shown that either HPGR or conventional crushing followed by dry milling produced the highest grades and recoveries (Palm et al., 2010). However in the present study it was observed that a similar treatment of Platinum-Group Minerals produced the poorest results and the highest grades and recoveries were obtained for the case of conventional crushing in combination with wet milling. The HPGR showed no advantages in terms of flotation performance and dry milling produced particularly poor flotation results.The results were investigated further using various surface characterization techniques in order to determine the reason for the decrease in grades and recoveries of platinum when using dry milling and HPGR as opposed to the case for base metal sulphides. The feed and product samples were analysed using ToF-SIMS, XPS and MLA. The paper will propose reasons to explain the different flotation behaviour of the two ore types following the various comminution processes focusing on the surface characteristics of the ores, the particle size distribution and the pulp chemistry.     

The role of a flash flotation circuit in an industrial refractory gold concentrator

In order to determine the contribution of the flash flotation circuit to the overall plant performance of the Kanowna Belle concentrator, two survey campaigns both with and without the flash circuit in operation have been conducted on two distinctly different ore types: a very high grade ore, and a very low grade ore of higher hardness. Using two different ores with the same target valuable mineral species (gold and pyrite) through the same treatment route allows any trends in performance to be more easily identified. As both survey campaigns involved running the plant with and without the flash flotation circuit in operation, the significant contribution of the flash flotation cell to overall plant recovery and final concentrate grade is highlighted. The flash circuit on this plant may be considered as the primary rougher, contributing in excess of 42% of the valuable material that is recovered to the final concentrate stream, at a grade of approximately 35% sulphur; and in-so-doing reducing the overall plant footprint that would otherwise be required to achieve the same recoveries at the target concentrate grade.Mineralogical analysis of survey samples shows that the feed to the flash flotation cell (cyclone underflow) is of a much higher grade and contains a higher proportion of well liberated valuable material as compared to the conventional flotation circuit feed (cyclone overflow). Maximising the recovery of this material before it re-enters the milling circuit should be of paramount importance to optimising overall plant performance.When the flash flotation circuit is taken off-line the recovery of sulphur (and hence pyrite) is observed to decrease dramatically, and whilst the recovery of gold also decreases, it is to a much lesser extent. The difference in the recoveries of gold and pyrite that is observed without the flash flotation circuit in operation is most likely attributable to a change in the way the gold is being liberated as a function of the change in grinding circuit operation that is required when the flash circuit is taken off-line. The distribution of valuable material in the cyclone overflow stream (conventional flotation feed) undergoes a step change when the flash circuit is taken off-line with an increase in the amount of valuable fines being generated, which is further reflected in the flotation tails with a higher proportion of both pyrite and gold being present in the intermediate and fine size classes. This increase in the amount of pyrite fines in particular may have contributed to the loss in recovery that was observed when the flash flotation circuit was taken off-line.Pulp chemistry data from various points around the flotation circuit highlight the different processing conditions in the flash cell, compared to the conventional circuit, which will impact on the type of minerals able to be recovered by flotation, as well as reagent selection for this type of processing application.     

The effect of frother blends on the flotation performance of selected PGM bearing ores

Concentrators processing PGM bearing ores make use of polysaccharide depressants to reduce the recovery of the undesired naturally floatable gangue minerals, mainly silicates, present in the ore. Recent work has shown that high depressant dosages can completely depress naturally floatable gangue and thus prevent it from reporting to the concentrate. These high depressant dosages can, however, have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the effects of depressant addition, frothers are added. It is, however, preferable to maintain independent control over bubble size and froth stability which is difficult to achieve with only one frother. An alternative strategy is to use a blend of frothers, e.g. a weaker frother in combination with a stronger frother. Such a system allows an additional degree of freedom: changing the ratio of the two frothers provides more independent control of bubble size and froth stability. This study demonstrates through the use of batch flotation tests how blending low molecular weight alcohols with commercially available frothers impacts the solids and water recovery, as well as the valuable mineral recovery and concentrate grade in different PGM ores. Higher water and solids recoveries together with higher valuable mineral recoveries (>90% copper and >70% nickel) were obtained from tests using frother blends.