Gangue Recovery Research Articles

Amorphous silica effects on copper flotation: A kinetic and selectivity investigation

Amorphous silica has been recently recognized for its adverse effects on copper flotation, but its impact remains poorly understood. This study investigates the effects of varying amorphous silica content on the kinetics and selectivity of copper flotation. Results show a significant reduction in chalcopyrite from approximately 99 % to 86 % with increasing amorphous silica content, attributed to increased pulp viscosity and slowed flotation kinetics. The classical first-order kinetic model provided the best fit for the flotation kinetics data, revealing that higher amorphous silica content prolongs the time required to achieve ultimate recovery. Results also show that amorphous silica deteriorated flotation selectivity and increased gangue recovery via entrainment, with complex variations depending on amorphous silica content. A small amount of amorphous silica was identified to significantly impair flotation kinetics and selectivity, leading to a deterioration in overall flotation performance.

Revisiting the enhanced selectivity in low-rank coal flotation by composite collector comprising kerosene and sorbitan mono oleate

In this study, the impact of KS collectors (blends of kerosene and span80) on flotation selectivity and the underlying mechanism were investigated to comprehensively understand the non-ionic composite collectors in low-rank coal flotation. Results demonstrate that Gaudin's selectivity indices are in the range 3.19–3.61 for kerosene at dosages in the range 2–10 kg/t, but 6.58–10.81 for KS collectors at dosages in the range 2–6 kg/t. This improved flotation selectivity was because the increase of gangue recovery was overshadowed by that of combustible recovery with the KS collectors. Results also revealed that, owing to span80, coal surface hydrophobicity was enhanced, thereby improving the true flotation recovery. Meanwhile, as a result of strengthened froth stability by span80, both water recovery and the degree of entrainment increased, resulting in the increased gangue recovery. In addition, proper usage of span80 for low-rank coal flotation was also highlighted in this study.

Effect of platy gangue minerals in sulfide flotation: Part I-transport rates

Observations from operating flotation plants suggest that the presence of the platy gangue mineral mica leads to significantly reduced concentrate grades. The combined effects of gangue particle shape (platy vs globular) and particle size on flotation has not been systematically investigated. Flotation tests were conducted on ground ore mixed with different amounts of sized mica (platy) or silica (globular) minerals. This essentially allowed us to alter the already present non-sulfide gangue (NSG) composition in a controlled manner and to investigate gangue size and shape effects on flotation recovery. The use of purposefully added mineral particles with narrow size distributions improved our ability to determine the different pathways by which hydrophilic particles of various sizes and shapes are transported through the froth. Cumulative mineral and water recovery data for each composition was used to calculate the degree of NSG entrainment for each ore plus adulterant (mica or silica). Analysis of the degree of entrainment vs adulterant particle size and shape showed that the addition of mica typically results in higher gangue recovery compared to when silica is added at comparable concentrations. The data for recovery when mica was added followed a trend associated with typical entrainment behavior, i.e., there was a decrease in the degree of entrainment with increasing mica particle size up to about 100μ. However, for greater mica size fractions, an increase in the degree of entrainment was observed. The reason for this behavior is discussed in the part II companion to this paper (Bhambhani, T., Farinato, R., Somasundaran, P., Nagaraj, D., 2022. Effect of play gangue minerals in sulfide flotation: Part 2: Mechanisms, Submitted to Minerals Engineering). The entrainment effects of mica were also evidenced to be concentration dependent. For coarser fractions of mica added to the ore pulp, where the degree of entrainment now increases with mica size, an increase in concentration of mica in that pulp resulted in a steeper increase in the degree of entrainment with mica particle size. This suggested second-order effects arising from particle-particle interactions. Similar results were seen with silica; however, deviations in the degree of entrainment vs particle size plots were less pronounced or required greater concentrations to be seen.

Beneficiation of Nickel from Ultramafic Ores: Using Sodium Citrate as a Green Processing Reagent

The processing of ultramafic ores requires fine grinding, which can result in slime-coating of the nickel-bearing mineral, pentlandite, by the phyllosilicate gangue mineral, serpentine. This lowers nickel recovery and concentrate grade during froth flotation operations. The presence of divalent cations in process water exacerbates the detrimental effects of phyllosilicates on nickel recovery by enhancing the positive surface charge of serpentine and causing charge reversal of pentlandite. To mitigate these issues, an environmentally benign, nontoxic, and biodegradable reagent, sodium citrate, was used in this study to chelate divalent cations on the pentlandite surface and desorb them from the mineral surface. The metal-citrate complexes adsorb onto the positively charged serpentine surface, reversing its charge. Sodium citrate was able to restore the surface charge and hydrophobicity of pentlandite, reverse the charge of serpentine, desorb the divalent cations from the mineral surface, and prevent MgO gangue recovery to the froth phase. Microflotation studies demonstrated that upon the addition of sodium citrate, nickel recovery increased from 74 to 96% and nickel grade was improved from 11 to 15.1% . The hydrophobicity of pentlandite was restored upon conditioning with citrate as evident by increase in water static contact angle from 50° to 70° , DLVO interactions showed that addition of citrate prevents slime coating of pentlandite by serpentine. The results demonstrated the depressive and dispersive action of sodium citrate.

Performance evaluation of processing clay-containing ore in Knelson concentrator

Performance of some mineral processing operations is known to be impeded due to the presence of even a small amount of clays. The study was conducted to evaluate the influence of commonly encountered clay types, bentonite and kaolin, on the performance of Knelson concentrator. Artificially mixed slurries of magnetite, quartz and clay were used for the experiments. The results indicated that the influence of both clay types on the operation of Knelson concentrator was insignificant; the reason is probably that clay particles are transported to the tailing without entering the concentrated bed inside the concentrate bowl of Knelson concentrator. Both magnetite and gangue recovery were analysed by plotting performance curves using size distribution.

The Behavior of Gangue During the Flotation of a Sulfidic PGM-Bearing Ore in Response to Various Monovalent and Divalent Ions in Process Water.

Mineral concentrators are becoming increasingly aware of the importance of the quality of the water that they feed into their milling and flotation circuits. It is speculated that different inorganic constituents of process water may yield different flotation results owing to the electrolyte–reagent–mineral interactions occurring in the pulp phase. These interactions are said to be specific to ion type, reagent type, and mineral or ore type. It therefore stands to reason that there is a need to develop an understanding of the specific ion effects on both the pulp phase and the froth phase phenomena, such that the chemistry and the quality of process water can be monitored and controlled in a manner that does not negatively affect the flotation performance. Previous research has shown that inorganic electrolytes may impact the hydrophobicity and the floatability of mineral particles and could in turn affect froth stability, entrainment, and thus mineral grades and recoveries. In this study, the floatability of a Cu-Ni-PGM-bearing Merensky ore is tested on a bench-scale flotation system in various single salt solutions, viz., CaCl2, CaSO4, Ca(NO3)2, MgCl2, Mg(NO3)2, MgSO4, NaCl, NaNO3, and Na2SO4, in order to examine specific ion effects on gangue recovery. Coagulation and zeta potential tests are conducted in order to establish the nature of the impact that specific ions have on the behavior of gangue in flotation. The findings of this work have shown that single salt solutions containing ions resulted in a strong depression of gangue compared to those solutions containing Cl− and SO42− ions. It was also shown that the divalent Ca2+ and Mg2+ showed a stronger depression of gangue compared to the monovalent Na+. Ca2+, in comparison to Na+, resulted in an increase in the coagulation of the ore as well as an increase in the zeta potential of talc. Overall, the findings of this paper suggest that the presence of Ca2+ and Mg2+ in process water would most likely create conditions that promote gangue depression.

Entrainment in froth flotation: The degree of entrainment and its contributing factors

In froth flotation, the degree of entrainment affects the concentrate grade and it is often assumed to be only a function of particle size in models. Literature suggests that other variables might also have a significant impact on the degree of entrainment. In this study, a factorial batch flotation experiment using a mixture of liberated chalcopyrite and two liberated gangue minerals, quartz and hematite, was performed to investigate the effects of these other variables (including impeller speed, gas flow rate, froth height and the specific gravity of gangue mineral) on the degree of entrainment. Results show that the degree of entrainment varied significantly as the flotation test conditions changed. Particle density and the interaction between gas flow rate and froth height had a statistically significant effect on the average degree of entrainment measured for the entire test. The degree of entrainment also significantly changed with flotation time throughout each experiment. It is hypothesised that these effects are a consequence of the degree of entrainment being affected by the weight of particles (not just their size) because of its effect on particle settling as well as the froth structure which provides varying resistance to particle drainage. It is concluded that models for the degree of entrainment that incorporate only particle size are not sufficient to predict gangue recovery and concentrate grade in an industrial application.

Evaluation of mineral processing by assessment of liberation and upgrading

A model is presented to evaluate mineral processing on basis of gangue recovery and valuables recovery. It combines mineralogical limiting curves with upgrading curves in the Fuerstenau diagram. These curves are used to assess mineral liberation and mineral beneficiation compared with the ideal result. Two new parameters (ratio of separation and ratio of liberation) are calculated based on a comparison of areas enclosed by the mineralogical limiting curve, the upgrading curve, the curve representing a total liberation of valuables, and the curve representing a perfect mixture of valuables and gangue.An assessment of the success of mineral processing is possible using these parameters. The assessment shows whether the quality of a separation product is influenced by the separation process itself or by the achieved liberation of the feed.A series of experiments on the magnetic separation of a greisen-type ore proves the applicability of this model to mineral processing. SEM-based image analysis and ICP-OES measurements have been used to obtain the necessary data.

Research of New Filling and Mining Technology Using Waste Rocks in Steep Coal Seams

During the extraction of steeply inclined coal seams, the coal recovery ratio is low be-cause of the coal pillar loss and the production of waste rock is high due to lots of rock roadways which causes serious environmental pollution. This status is conflicted with the strategy of Clean Coal Mining and Green Coal Mining in China, so it is necessary to develop new coal mining method. In this paper, Downward Stratified Gangue Self-filling Method on the Flexible Shield (DSGSMFS) is put forward first. It means that the coal face is lain horizontally and advances along the dip; the flexible shield is used to separate the gob area; the waste rocks are self-filled downward to the top the shield; the coal is broken by drilling and blasting method under the shield, and the broken coal is transported by the electrical winch and the scraping mucker; the flexible shield moves downward automatically by the weight of itself and waste rocks. Field test shows that the strata displacement is effectively controlled by using DSGSMFS, so some coal pillars are recovered; as a result the problem of large quantity gangue and low coal recovery ratio in steep coal seam is solved. DSGSMFS is proved to be a new hopeful and effective coal green mining method.

Statistical evaluation of flotation and entrainment behavior of an artificial ore

The role of several parameters on gangue recovery in froth was investigated. Effects of frother type and collector dosage on flotation performance were tested at pH 10. The results were evaluated statistically by two-way analysis of variance without replicates, sample range and sample standard deviation. Hydrophilic mineral was recovered mainly by entrainment through hydrophobization of Ca+2-activated quartz from tap-water in the presence of Na-oleate as collector; entrapment and slime coating were also proposed as recovery mechanisms in minority. Degree of gangue-entrainment in froth product increases by reduction in liberation size. The experimental results state that selectivity would be improved by increasing collector concentration and reducing the flotation time.

Identification of hazards in the workplaces of Artisanal mining in Katanga

While artisanal mining takes place in casual framework and with total ignorance of good practices, few studies have focused on the origin of hazards specific to each workplace constitutive of this exploitation facility. Nevertheless, this study is a condition of an efficient occupational health and safety control in this sector. We took the effort to identify different workplaces, as well as hazards specific to each of them, through the observation and analysis of the tasks, tools and the processes related to their use applied in the Ruashi artisanal mine. The investigated exploitation facility consists of five workplaces: diggers (60%--in charge of mineralized gangue recovery); crushers; washers; hand-made furnace workers (in charge of various treatment processes); and loaders (in charge of packing the obtained material). Beside the risks common to these various workplaces and ensuing notably from the lack of hygiene and working in bad positions, operating in underground galleries, in particular, exposes diggers to the risks connected with collapsing parts of the mine, suffocation, dehydration or fine particles in the breathed air. Crushers are especially exposed to traumatism risks, notably ocular, and loaders are exposed to risks related to handling heavy loads. These risks are connected with the mining processes because, in spite of the similarity of tools, they appear less often in other forms of artisanal exploitation described in literature. It is notable in the case of crushing in sawed gas bottles where ocular trauma risk is decreased. It was also shown that humidification of work surface reduces dust particles emission into the air. Hazards identification, through a tools and processes description, has the advantage of providing information on reducing the occurrence of these risks. It shows that this reduction is not necessarily a consequence of the activity mechanization degree.

The effect of ionic strength of plant water on valuable mineral and gangue recovery in a platinum bearing ore from the Merensky reef

As the restrictions on water usage become more prevalent throughout the world, mining operations are required to understand the impact that water recycling will have on them. Not only owing to operational needs, but also from an environmental stand point. As would be expected recycling is likely to lead to increased dissolved ions, increasing the ionic strength, which may impact plant performance. By conducting flotation tests under varying degrees of ionic strength of synthetic plant water it is possible to better understand the effect that water recycling could have on the recovery of a mining operation. The effect of such an increase in ionic strength is discussed.

Particle entrainment model for industrial flotation cells

A simple empirical dimensionless model to calculate the mineral gangue recovered per size class ( R G, i ) by entrainment, in terms of the water recovery ( R W), in an industrial flotation cell is presented. For modeling purposes, a dimensionless entrainment factor EF i , corresponding to the ratio ( R G, i / R W), was defined for each particle size class. From experimental data measured in an industrial 130 m 3 flotation cell, it was found that EF i was well correlated with the dimensionless ratio ( d P, i / δ) by E F i = exp ( − 0.693 ( d P , i δ ) Φ ) where d P, i is the particle size class “ i”, and δ parameter corresponds to the mean particle size for EF i = 0.5, Φ is a drainage parameter, which depends on the mineral characteristics and cell operating conditions (i.e. cell design and water recovery). The gangue recovery model was evaluated in a large industrial flotation cell, where the entrainment factor was calculated by direct measurement of the bubble load grade for non-selective froths (high water recovery), and by measuring the top of froth grade for selective froths (low water recovery). The model was also successfully tested using two different sets of industrial flotation data, taken from literature (Engelbrecht and Woodburn, 1975; Zheng et al., 2006). The particle entrainment model is a powerful tool for flotation process modeling and simulation, to explore the impact the water recovery has on the final concentrate grade.

Convective–dispersive gangue transport in flotation froth

The transport of gangue through flotation froth has been described by solving the convection–diffusion equation. Gangue recovery is predicted to be proportional to liquid recovery, which is consistent with experimental observation. In addition, it is seen that the dependency of gangue recovery upon particle size is due to processes within the pulp phase rather than the froth, insofar as the transport of particles in a given froth is approximately independent of size. The importance of maintenance of positive bias in column flotation, previously stressed by other workers, is reinforced. This model utilises a simplified representation of the froth and, as a consequence, it does not necessarily give accurate gangue recovery estimates for practical flotation processes. However, the convective–diffusive model does illuminate the physical processes behind gangue recovery in the concentrate which will aid the development of automatic control strategies.

Simulating realistic froth surfaces

Image analysis as a tool for monitoring and controlling flotation froths has become quite widely used in the minerals industry. One of the challenges is to be able to use the image analysis data to predict the performance of a flotation cell. One of the key parameters to be predicted is the water recovery from the froth, since this is intimately related to the gangue recovery and thus the grade. Recent theoretical developments have allowed for the calculation of this water recovery based on the air rate, froth stability and the bubble size distribution. The problem is that all that can be seen of a froth is the bubble films at the top surface. This paper uses physics based simulations of the froth structure to show that the relationship between the size distribution of the films seen at the top surface and the underlying bubble size distribution is a complex one. The paper presents some preliminary results on the statistical relationship between these distributions.

The use of FrothSim to optimise the water addition to a column flotation cell

This paper examines the use of the FrothSim flotation simulator to improve the performance of an industrial column flotation cell. The performance of an industrial retreat column cell is simulated, and, from the discrepancies between the simulated and experimental results, a problem with the wash water distribution is postulated. The scientific reason for the reduced performance with uneven wash water addition is described in detail. Further simulations indicated the potential for improvement with an even wash water distribution, resulting in both improved performance and reduced wash water usage. The simulated uneven wash water distribution was confirmed industrially, and the headers were redesigned and installed. A sampling campaign to compare the performance before and after the modifications showed that the flotation performance was improved dramatically, with a statistically significant decrease in gangue recovery, without a commensurate reduction in valuable mineral recovery.

A statistical model for gangue entrainment into froths in flotation of sulphide ores

In this study, the significant operating parameters affecting to the gangue recovery such as froth thickness, pulp density, aeration rate etc. were considered in order to establish a statistical model for the mechanical entrainment, which is one of the significant mechanisms of gangue transportation into froths. To produce the experimental data, laboratory bulk flotation tests were conducted on a copper—iron sulphide ore at the predetermined flotation conditions. Evaluation of the data obtained from the tests showed that the amount of gangue entrained in the froth is a proportion of the water recovered in the concentrate. In addition, some of the water recovery values that have approximately the same magnitudes were obtained from the tests conducted under different flotation conditions. But the gangue recovery values that have different magnitudes were obtained from these tests. In the light of these findings, establishment of a multivariable non-linear estimation model was seen to be a rational approach for description of the relationship between the gangue recovery and other parameters that closely related with the water recovery. It was determined that there is a good agreement between observed results and calculated results from the model developed.

A conceptual model for gold flotation

This paper is aimed at producing a conceptual model for gold flotation based on the discussion of a number of experimental results where the behaviour of free and refractory gold has been studied under different chemical and physical conditions. A review of the literature suggests that there have been numerous studies on the flotation of free gold particles and refractory sulphides, but these investigations have typically focused on the individual flotation behaviour of each gold bearing species in synthetic mixtures and not when they are present together in “real” ores in the same pulp. The model discussed here shows that the flotation of refractory gold follows a similar trend to the recovery of refractory pyrite and pyrrhotite and is mainly affected by chemical conditions in the pulp such as redox potential, aeration conditions, copper activation, reagent synergism and galvanic interaction. Refractory gold is usually recovered by true flotation that is hydrophobic particle-bubble attachment, unless under certain conditions the physical transport of water and gangue provides a washing effect and detaches some of the sulphide material from the air bubbles. The flotation recovery of free gold is largely affected by physical constraints like the shape and size of the particles, the degree of water and gangue transport to the froth, the stability of the froth, and the extent of bubble loading of sulphide particles which can provide a barrier towards the hydrophobic bubble attachment of free gold. In each individual study the results suggest that the recovery of free gold follows a proportional trend with regard to water and gangue recovery. However, there is an inverse relationship between the true flotation of free and refractory gold due to the fact that free gold particles cannot attach to air bubbles properly in the presence of physical barriers.

Review and analysis of factors controlling the mechanical flotation of gangue minerals

Mechanical flotation of gangue minerals is reviewed. First, mechanisms that contribute to gangue transportation are considered. The effect of water recovery and other essential factors on gangue recovery is described, and mathematical models for classification and entrainment of gangue are presented. The importance of froth characteristics is also discussed. An analysis method to evaluate the entrainment of gangue in flotation circuits is presented. Measures to restrain the mechanical flotation of gangue are also considered.

Effect of pulp cleaning zone on gangue control in column flotation

A physical modelling technique has been used to evaluate the role of the zone between the feed inlet and the pulp froth interface (pulp cleaning zone) to control gangue recovery in column flotation. The behavior of gangue was simulated using Ottawa sand having d 80 of 150 ,um and 250 pm. The column used had an internal diameter of 0.06 m and the dispersion height was maintained at 0.84 m. By varying the feed position, the average solid concentration in the pulp cleaning zone was estimated. The results obtained indicate that a 0.20 m separation between the feed inlet and the interface was sufficient to effect the rejection of coarse gangue particles. Under similar operating conditions, the finer material exhibited negligible changes in the solid hold-up in this zone, thus indicating that the transport mechanisms for fine and coarse particles in flotation columns are different. The implications of these findings in column flotation are discussed.