The influence of particle shape properties and associated surface chemistry on the flotation kinetics of chalcopyrite

The role of particle shape properties in determining flotation kinetics was investigated in this study. −150/+75 μm chalcopyrite was floated in a microflotation cell, and shape properties of the timed concentrates were quantified using a mineral liberation analyser - a mineralogical characterisation system based on automated scanning electron microscopy. It was found that, when floated in the absence of collector, particles with angular shape features reported to the concentrate faster than round particles. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) showed that angular particles also exhibited surface chemistry characteristics favourable for flotation. When particle floatabilities were high (i.e. when floated in the presence of potassium amyl xanthate), shape properties were not found to contribute significantly to the rates at which particles floated.     

Influence of the propagation of three phase contact line on flotation recovery

Froth flotation is considered the most effective process of beneficiating low grade ores and is widely used in the base metals industry. For effective flotation, the attachment of mineral particles to air bubbles is important and has been studied by many researchers by measuring quantities such as attachment time, film-thinning time and induction time. This paper identifies an important step in the bubble–particle attachment process, namely, the expansion mechanism of the three phase contact (TPC) line between liquid, solid and air. It has been shown that the TPC expansion time is determined by the drainage of the surrounding fluid. It is influenced by factors such as pulp chemistry surrounding the particle, variations in surface forces and pressure inside the bubble. It has been observed experimentally that the TPC expansion time bears square root relationship to attachment efficiency. In this work, it has been argued that the attachment efficiency is related to the TPC circle radius propagation.     

Predicting the surface chemistry contribution to the flotation recovery of chalcopyrite by ToF-SIMS

In flotation, the surface chemistry of the minerals plays a crucial role in the selectivity and recovery of valuable minerals. Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) surface analysis is used in this study to investigate the impact of surface chemistry on the flotation of chalcopyrite with dithiophosphate collector. The ToF-SIMS data corresponding to concentrate and tail particles were statistically analysed employing a combination of multivariate statistical techniques - principal components analysis and discriminant analysis - to identify the surface species that are differential in the flotation of chalcopyrite. Two models were developed to predict the concentrate and tail deportment of particles, one targeting fine and intermediate particle sizes and the other for the coarse particle size. These models were tested using cross-validation and the results showed good prediction accuracy, 88% for fine and intermediate particles and 77% for coarse particles. The models were further tested on feed samples and the results show the developed models can be used as a predictive tool that estimates the maximum recovery expected based on the surface chemistry of particles, as evidenced by ToF-SIMS, under given hydrodynamic conditions.     

A CFD-kinetic model for the flotation rate constant,Part II: Model validation

A Computational Fluid Dynamics (CFD) model was validated against published experimental data for the prediction of the flotation rate constant. An Eulerian–Eulerian framework was applied for modelling the multiphase flow inside a standard laboratory scale Rushton turbine flotation tank. The dispersed k–ε turbulence model simulated the turbulent effects inside the tank, while the collision, attachment and stability efficiencies were calculated using the local values of hydrodynamic parameters. Volume-weighted average flotation rate constants were simulated for chalcopyrite and galena and compared against published experimental data for the same physical setup. The results showed that both qualitatively and quantitatively the developed CFD-kinetic model can predict the flotation rate constants with an acceptable level of accuracy. Moreover, the validations of rate constants for the flotation of chalcopyrite and galena under various contact angles, agitation rates and gas flow rates confirmed the predictive capability of this numerical approach for further flotation modelling.     

Effect of amine and starch dosages on the reverse cationic flotation of an iron ore

In iron ore concentration, reverse cationic flotation of quartz has been successfully employed for particles below 150 μm previously deslimed. Amine and starch are used, respectively, as quartz collector and iron oxides depressant. Understanding the mechanisms of reagents interaction is relevant to improve the separation selectivity, especially for high amine dosages. The term clathrate was used to explain this interaction, meaning a molecular compound in which molecules of one species occupy the empty spaces in the lattice of the other species, resulting in the depression of hydrophobic minerals. Laboratory scale experiments were carried out with itabirite iron ore in three different size ranges. The clathrate formation between molecules of amine and starch may explain the increase of SiO₂ content in the concentrates of the coarse size range (−150 + 45 μm) due to an increase in amine dosage.     

A computational fluid dynamics model for the flotation rate constant,Part I: Model development

A Computational Fluid Dynamics (CFD) model for the prediction of the flotation rate constant in a standard Rushton turbine flotation tank was developed. The premise for the model development was the assumption that separation by flotation is a first order rate kinetic process. An Eulerian–Eulerian framework in conjunction with the dispersed k–ε turbulence model was supplemented with user defined functions to implement the local values of the turbulent flow into a kinetic model. Simulations were performed for quartz at different operational conditions. The numerical predictions were validated against experimental data and analytical computations using the fundamental flotation model of Pyke et al. (2003). The results showed that the CFD-based model not only captured the trend of experiments for a range of particle sizes but also that the CFD yielded improvements in the predictions of flotation rate constant compared with the theoretical calculations. It was found that the CFD model is able to predict the flotation rate constants of the quartz particles floating under different ranges of hydrophobicity, agitation speed and gas flow rates with lower root mean square deviation compared with the theoretical computations.     

A comparison of the predictability of batch flotation kinetic models

Batch flotation test data of a mixture of pyrite and calcite were used to compare regression parameters of four kinetic model structures. The work included the use of unoxidized or a mixture of partially oxidized pyrite (by microwave irradiation). The objective of floating oxidized pyrite was to have mineral particles with different floatability, closer to a real situation. The models considered include: single rate constant, distributed rate constants (i.e. rectangular and gamma distributions), and a recently introduced approach based on fractional calculus. Such models were selected due to their good tradeoff between simplicity and accuracy. The regressions were performed (1) taking all the data points and comparing the mean square error (MSE) and adjusted correlation factor $\left(R_{\mathit{Adj}}^2\right)$ as indicators of the goodness of fit; and (2) taking the first data points while neglecting the last ones (from 1 to 3) and observing the variability of the model parameters and the prediction of maximum recovery (R_∞). For the latter regression scheme, besides MSE and $R_{\mathit{Adj}}^2$, a predictive factor, E, was defined by subtracting the final measured recovery from the calculation obtained by the model. This allowed to measure the ability of each model to extrapolate the omitted points on the recovery vs. time curve.Results from this study showed that the single constant model had a satisfactory performance with the advantage of having the least parameters compared to the other structures. The gamma model was effective and robust. The rectangular model gave an acceptable goodness of fit but overestimated the maximum and final recovery. Finally, the fractional calculus approach gave the best goodness of fit, overall, but failed in predicting the maximum recovery, which occurred when the derivative order was greater than 1.     

新型环保抑制剂在某铜铅精矿浮选分离中的应用

对某铜铅混合精矿进行了浮选分离实验研究。采用硫酸作调整剂,环保药剂ZJ201作铅的抑制剂,不仅将铜铅混合精矿进行了有效的分离回收,而且避免了重铬酸盐等传统有毒抑制剂的使用。将该药剂应用于工业生产,获得了铜品位为27.74%,铅含量为3.48%,铜回收率为93.33%的铜精矿和铅品位为67.11%,铜含量为0.23%,铅回收率为99.41%的铅精矿,试验指标良好,经济效益显著。     

A strategy for the identification of optimal flotation circuits

This article presents a strategy for the identification of optimal flotation circuits based on experimental data and the assumption that the flotation circuit structure are not very sensitive to stage recovery. The main objective is to find a set of optimal flotation circuit configurations, including the best metallurgical conditions for the process and cell design. The optimization process maximizes the Net Present Value (NPV). This methodology consists of two steps. The first step of the methodology entails obtaining data from the laboratory. Different metallurgical conditions are tested for different flotation stages. Each metallurgical condition is evaluated to determine its kinetics. The second step of the methodology is the optimization process. The optimization process achieves the best solution by optimizing cell design, flotation circuit structure and metallurgical conditions. The optimization process has three phases. The first phase assumes that every flotation stage has the same residence time and calculates feasible flotation circuits, metallurgical conditions and cell volumes. This process is performed for several residence times and, therefore, a set of feasible solutions is generated. The second phase takes the previous set of feasible solutions and calculates the residence time at each flotation stage. Then, for each phase two solution, the optimal flotation circuit, metallurgical conditions and cell design are calculated. The final product is a set of optimal solutions than can be considered for further study. The procedure is illustrated by the design of a zinc flotation plant, considering seven flotation stages and five species.     

A review of the effect of water quality on flotation

As water resources become scarcer and society’s demands to reduce freshwater extraction have increased, mine sites have been increasing water reuse and accessing multiple water sources for mineral processing to save freshwater, particularly in froth flotation. Implementation of either strategy may lead to water quality variation that may impact flotation efficiency. A large number of studies have been carried out to enhance the understanding of water quality variation in flotation. However, these studies tend to be performed on a case by case basis. There is a lack of a framework to put together these existing studies, which makes it difficult to understand the topic comprehensively and therefore difficult to identify gaps and directions for future research. This would eventually hinder the ongoing implementation of water conservation practices and thus lead to more pressure being placed on freshwater. In this paper, a review of the existing studies on water quality variation in flotation is given in three aspects: causes of water quality variation, consequences of water quality variation and solutions for problems caused by water quality variation. Based on the three aspects, a framework was developed, with which these studies were categorized and structured. Organizing literature in this way makes it possible to identify gaps in current research and future research directions.     

Effects of oils and lubricants on the flotation of copper sulphide minerals

The effects of the addition of oils and lubricants commonly encountered in mining and processing copper sulphide ores on the subsequent flotation of copper minerals was investigated by laboratory scale testing. The project arose as a result of intermittent uncontrollable frothing and a drop in selectivity observed at an Australian copper-gold concentrator. The addition of distillate to the grinding stage actually increased selectivity in the subsequent copper mineral flotation but other oils and lubricants used at the plant had detrimental effects on selectivity and frothing behaviour. A degreaser used in maintenance operations dramatically lowered copper grade and generated a very stable and sticky froth even at low concentrations. Similar detrimental effects on gold metallurgy were also observed. Mineralogical examination of flotation products verified that the decrease in grade of the concentrates was due to the flotation of free gangue minerals and not due to any liberation problems. Possible mechanisms for these effects aer discussed. Anecdotal evidence for these effects abound in discussions held with plant metallurgists, but little published data on these effects have been located.     

Electrokinetic and flotation behaviors of hemimorphite in the presence of sodium oleate

The electrokinetic and flotation behaviors of hemimorphite in sodium oleate solution were studied. The results of micro-flotation experiments indicate that hemimorphite shows good floatability at pH 4.0–9.0 and pH 11.0. The point of zero charge (PZC) of hemimorphite is pH 5.1. Zeta-potential and FTIR measurements indicate that the mechanism of sodium oleate adsorption on hemimorphite involves both chemical and physical interactions. Sodium oleate mainly reacts with the Zn on the hemimorphite surface. In acid/base pH range, the aggregation among hemimorphite particles which is more likely caused by hydrophobic interaction than electrostatic interaction improves hemimorphite’s floatability.     

A new method for flotation rate characterization using top-of-froth grades and the froth discharge velocity

A new methodology is proposed for flotation characterization in industrial operations. The approach considers the mineral recovery to be proportional to both the top-of-froth (TOF) grade and the froth discharge velocity down a bank of cells. The procedure allows for the identification of the fractional recovery profile from the discharge velocities and the TOF grades. In addition, if the total recovery of the bank is available, the cell recoveries can be estimated by scaling the fractional recoveries. For this purpose, a single parameter was used to scale the recoveries for each sampling survey in order to obtain the kinetic response along the flotation banks. Industrial tests were performed in two rougher banks; one bank consisted of six 250 m³ self-aerated cells in a 1-1-1-1-1-1 arrangement, and the other bank consisted of nine 130 m³ self-aerated cells in a 1-2-2-2-2 arrangement. The results showed good agreement with the recovery profiles obtained from the cell-by-cell mass balances along two industrial flotation banks.     

On the mechanism of the flotation of oxides and silicates

The mechanism of flotation of oxide and silicate minerals was established long ago as being due to the electrostatic attraction between the charged surface and the charge of the collector. What is less well established is the mechanism of the charging of the mineral surface. Most researchers have postulated that the adsorption of H⁺ is the cause. However, the adsorption model and its derivatives (such as the amphoteric and multisite-adsorption models), do not successfully describe the data for the zeta potential as a function of pH. In particular, these adsorption models have the following features that are not observed: (i) they are symmetrical about the point of zero charge, whereas the data is asymmetrical, (ii) they have an inflection at the pK_a values, leading to an asymptotic approach to the point of zero charge, whereas such an inflection is not observed, and (iii) they only fit the data in its extremes, that is, when the pK_a values differ by orders of magnitude, or are very close to one another. An alternative mechanism of charging is proposed here that is based on the dissolution of ions from and deposition of ions onto the mineral surface. It is shown that this model (a) fits the data, (b) is consistent with the thermodynamic model for reversible interfaces, (c) is consistent with the thermodynamics of the overall reaction and its solubility, (d) indicates reasons for the ageing of surfaces and (e) displays the observed features of zeta potential measurements as a function of pH, that is, it is pseudo-Nernstian and asymmetrical in nature. Application of the proposed theory is discussed for the flotation of quartz and corundum.     

The relationship between the stability of emulsified diesel and flotation of graphite

The emulsified diesel is a good collector of non-metallic minerals, such as coal and graphite, but it suffers from easily stratification which may lead to the change of graphite flotation. This paper reports research on the relationship between the stability of emulsified diesel and graphite flotation. The results shows that the proper Hydrophile Lipophilic Balance (HLB) value (13–14) and co-emulsifier (hexyl alcohol) can improve the stability of emulsified diesel and increase the recovery of graphite. Better dispersion state of diesel in water and smaller oil droplets could be formed when the stability of emulsified increases, which leads to enhancement of graphite recovery. Besides, the tests of the real ore proved that emulsified diesel is better collector than common diesel.     

Creation of the efficient flotation agents on the basis of new raw materials and chemical industry waste

It is reported on creation, implementation, and mechanism of action of flotation agents that are developed by the Russian scientists and are brought into industrial use for mineral dressing. The data are cited about the new collecting agents and the subsidiary agents that improve the existing technological schemes. The new efficient flotation agents, which are created on the basis of chemical and petrochemical industrial waste, are presented. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 75–88, July–August, 2006.     

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.     

Froth flotation of sphalerite: Collector concentration,gas dispersion and particle size effects

This experimental work on sphalerite flotation investigated the effect on flotation performance of three particle size fractions, namely, coarse (d₈₀ = 100 μm), medium (d₈₀ = 39 μm) and fine (d₈₀ = 15 μm), bubble size distribution, superficial air velocity, and collector dosage. Bubble size distributions were characterized with the image analysis technique. The two-phase (liquid–gas) centrifugal pump and frother addition (MIBC, 5–30 ppm) allowed generating bubble diameters between 150 and 1050 μm, and air holdup ranging from 0.2% and 1.3%. Main results showed that each particle-size distribution required an optimal bubble-size profile, and that sphalerite recovery proceeded from mechanisms involving true flotation (when J_g = 0.04 cm/s and 1.9 × 10⁻⁴ M SIPX). However, cluster-flotation occurs at high collector dosage (when J_g = 0.04 cm/s and d₃₂ between 285 and 1030 μm), and requiring further investigation.     

Decoupling rehology and slime coatings effect on the natural flotability of chalcopyrite in a clay-rich flotation pulp

Clay minerals are a commonly occurring gangue in mineral beneficiation operations and occur in a variety of ore deposits, including porphyry copper ores. The presence of clays in mineral beneficiation circuits can cause a wide range of different problems, including that of slime coatings on valuable minerals and elevated viscosities of flotation pulps. The aim of this work was to decouple and estimate the relative magnitudes of the slime coatings and pulp rheology effects on the natural floatability of chalcopyrite in a model mineral system. It was found that the two phenomena can be partially isolated and that they both have a detrimental effect on flotation performance. It was also found that the level to which these two phenomena affect chalcopyrite recovery is of a similar order of magnitude.