Flotation Response Research Articles

Modelling of coal flotation responses based on operational conditions by random forest

Coal consumption is one of the critical factors in the economy of China. Flotation separation of coal from its inorganic part (ash) can reduce environmental problems of coal consumption and improve its combustion. This investigation used random forest (RF) as an advanced machine learning method to rank flotation operations by variable importance measurement and predict flotation responses based on operational parameters. Fifty flotation experiments were designed, and performed based on various flotation conditions and by different variables (collector dosage, frother dosage, air flowrate, pulp density, and impeller speed). Statistical assessments indicated that there is a significant negative correlation between yield and ash content. Experiments indicated that in the optimum conditions, yield and ash content would be 80 and 9%, respectively. Variable importance measurement by RF showed that frother has the highest effectiveness on yield. Outcomes of modelling released that RF can accurately be used for ranking flotation parameters, and generating models within complex systems in mineral processing. [Received: May 20, 2020; Accepted: July 19, 2020]

Modelling of coal flotation responses based on operational conditions by random forest

Coal consumption is one of the critical factors in the economy of China. Flotation separation of coal from its inorganic part (ash) can reduce environmental problems of coal consumption and improve its combustion. This investigation used random forest (RF) as an advanced machine learning method to rank flotation operations by variable importance measurement and predict flotation responses based on operational parameters. Fifty flotation experiments were designed, and performed based on various flotation conditions and by different variables (collector dosage, frother dosage, air flowrate, pulp density, and impeller speed). Statistical assessments indicated that there is a significant negative correlation between yield and ash content. Experiments indicated that in the optimum conditions, yield and ash content would be 80 and 9%, respectively. Variable importance measurement by RF showed that frother has the highest effectiveness on yield. Outcomes of modelling released that RF can accurately be used for ranking flotation parameters, and generating models within complex systems in mineral processing. [Received: May 20, 2020; Accepted: July 19, 2020]

The Characteristics of Iron Ore Slimes and Their Influence on The Flotation Process

The flotation has been successfully applied to process the iron ore for the particle size (Ps) from 10 µm up to 150 µm. The presence of the slimes (Ps < 10 µm) is harmful on the reverse flotation of quartz, so they are usually prior removed by hydrocyclones. The main effects of the presence of slimes on the flotation are related to the increase on reagents consumption, the froth stability, and decrease on the selectivity. The lower floatability of coarse quartz particles (+74 µm) combined with the presence of slimes, even in small quantities, drastically affect the flotation response. This paper shows a study of characterization of a typical iron ore slime, aiming to create a better understanding of its role on the concentration by flotation. The main characteristics of typical slimes from the Iron Ore Quadrangle in Brazil are the presence of almost 70% of hematite, 25% of quartz, and 5% of kaolinite, as the main silicates gangue minerals. Furthermore, the particle size distribution revealed that 80% of the hematite and the kaolinite are below 20 µm. The affinity between the ultrafine kaolinite of the slimes with the corn starch is harmful to the reverse flotation of quartz, as the starch has an important depressing action over the hematite. The presence of 20% of hematite −20 µm decreased the recovery to the froth of quartz + 74 µm from 97% to 62%, where the slimes coating seems to be the main responsible.

A novel activation for ilmenite using potassium permanganate and its effect on flotation response

This study proposed a novel activation method for ilmenite by using potassium permanganate as an oxidant and a surface modifier. The valence state of iron atoms on the ilmenite surface was transformed under weak-acid conditions; therefore, the interaction between Fe sites on the ilmenite surface and sodium oleate was enhanced. The flotation of ilmenite was improved with a high recovery close to 90 %. The activation mechanism was studied via batch flotation, zeta-potential measurements, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The results showed that under weak-acid conditions, potassium permanganate promoted the interaction between sodium oleate and ilmenite. The addition of potassium permanganate resulted in new characteristic absorption peaks in the infrared spectra of the ilmenite, and the chemical shifts at 1559.78 cm−1 and 1444.94 cm−1 were greater than those of the unactivated ilmenite. The positive shift of the binding energy of Fe 2p promoted the electron supply of Fe(II) to the permanganate ions. The Fe(III) content on the ilmenite surface greatly increased, making the interaction with sodium oleate easier. Thus, potassium permanganate promoted the valence transition of Fe(II) to Fe(III) and enhanced the adsorption between minerals and collectors, which ultimately improved the flotation recovery of ilmenite.

Comparison of flotation performances of low-rank coal with lower ash content using air and oily bubbles

The attachment interaction in a flotation process is critical because it controls the recovery of mineral particles and is dominated by the interaction energy barrier between bubbles and solid particles. In this investigation, the surface properties of coal particles and oily bubbles were evaluated via the X-ray photoelectron spectroscopy (XPS) analysis, zeta potential measurement and induction time tests. The results proved that the classical Derjagin–Landau–Verwey–Overbeek (DLVO) theory did not adequately predict the flotation performances of oily bubble flotation. The attractive interaction or hydrophobic force induced by the hydrophobic force should be considered in the extended DLVO (EDLVO) theory. Throughout this paper, therefore, it is significant to consider the attractive interaction or hydrophobic force between low-rank coal particles and oily bubbles when comparing the advantages of the flotation response using air and oily bubbles.

Selective depression of talc in chalcopyrite flotation by xanthan gum: Flotation response and adsorption mechanism

Being a common gangue mineral in many sulfide deposits, naturally hydrophobic talc needs to be depressed by adding depressants. In this paper, xanthan gum was introduced as a selective depressant for talc. The effect of xanthan gum on the flotation separation of chalcopyrite from talc has been studied, and the interaction mechanism between xanthan gum and talc has been investigated. Micro-flotation results show that xanthan gum severely depresses talc flotation but barely affects chalcopyrite flotation at pH 8. In artificially mixed minerals flotation, a concentrate containing 31.87% Cu can be obtained at 90.03% Cu recovery from a feed of 16.94% Cu, indicating xanthan gum as a selective depressant. The effect of xanthan gum was also verified by the real ore flotation tests. The zeta potential measurements and adsorption measurements indicate that xanthan gum selectively adsorbs on talc surface. The results of XPS measurements and adsorption measurements illustrate that the adsorption of xanthan gum on talc surface occurs through physical interaction and hydrophobic interaction is considered as the main driving force. AFM images show that xanthan gum adsorbs on talc surface in a network structure with a layer thickness of 5.4 nm and coverage of 53.57%.

Bastnaesite, Barite, and Calcite Flotation Behaviors with Salicylhydroxamic Acid as the Collector

The flotation of bastnaesite, as a major mineral source of rare earth elements, attracting much attention in the mineral processing field, is challenging owing to the natural flotability of calcium-bearing minerals. To promote the application of flotation, we systematically investigated the flotation behavior of bastnaesite, barite, and calcite, with salicylhydroxamic acid (SHA) as the collector through micro-flotation experiments, zeta-potential measurements, Fourier transform infrared (FT-IR) analyses, X-ray photoelectron spectroscopy (XPS) analyses, and solution chemistry analyses. Micro-flotation experiments confirm that the flotability of bastnaesite is high at pH 6.5–8.5, while calcite floats at pH 8.0–9.5, and barite has little flotation response. The results of FT-IR, XPS, and zeta-potential measurements indicate that there is chemical adsorption of SHA on the bastnaesite surface, and physical adsorption also occurs. However, as for barite and calcite, there is only physical adsorption of SHA on the surfaces. The solution chemistry results show that SHA anions can interact with RE3+, REOH2+, and RE(OH)2+ on bastnaesite surfaces in aqueous suspensions, resulting in bastnaesite flotation.

The influence of lime and sodium hydroxide conditioning on sulfide sulfur behaviour in pyrite flotation

The influence of two alkaline pH modifiers, namely sodium hydroxide and calcium hydroxide was investigated to evaluate and compare their effectiveness in pyrite rougher flotation of a refractory gold ore with a high sulfide sulfur grade (13% S2-), using potassium amyl xanthate as the collector and Nascol 422 as the frother. The focussing question for this study was to determine if there was a promising premise for substituting lime with sodium hydroxide as a pH regulator in the rougher flotation of Lihir and possibly other ores, where there is excess sulfur to be treated in the downstream oxidation processes relative to the amount of gold present in the rougher concentrate. If this replacement is possible, then the sulfide sulfur levels of the rougher concentrates could be optimised for a direct autoclave feed. The potential of sodium hydroxide to modify the flotation response of gold-rich pyrite versus low-gold pyrite could be established. The sulfide sulfur results from the flotation tests show that, for identical rougher flotation conditions, the use of sodium hydroxide compared to lime conditioning increased the gold to sulfur ratio (Au:S) of the rougher concentrates and enhanced the gold recovery rates.

Thermochemical modification for the surface of smithsonite with sulfur and its flotation response

Thermochemical modification for the surface of smithsonite with sulfur and its flotation response were investigated by micro-flotation tests, X-ray powder diffractometer (XRD) combining with thermodynamic calculations, X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA). Micro-flotation tests results showed that the addition of the sulfur at a small S/ZnCO3 mole ratio (0.05) during the thermochemical modification process facilitated flotation of the smithsonite and improved the flotation recovery by approximately 65%. The results of XRD analyses and thermodynamic calculations verified that the smithsonite was decomposed into zincite and then interacted with sulfur, forming sphalerite at the surface, after the thermochemical modification in the presence of sulfur. XPS analyses results revealed that both ZnS and ZnS2 were formed at the surface of the obtained zincite. EPMA analyses confirmed that the sulfides were unevenly distributed at the out layer of the zincite. The average concentration of S at the surface of the obtained zincite increased with the increase in the sulfur dosage. This study gave a deep insight into the interaction between the smithsonite and sulfur at high temperatures and further enriched the surface sulfidation mechanism of the smithsonite.

Designing coal preparation circuit for cleaning high ash and high sulfur Punjab (Pakistan) coal to meet end-user requirements

ABSTRACT Modern coal preparation plants are designed to achieve maximum overall clean coal yield with an acceptable amount of impurities to meet end-user requirements. LIMN is commonly used to design and simulate coal processing circuits based on size and density distribution data of coal. In this study, particle distribution data for size, density, and floatability were established for Punjab coal after crushing it to 38 mm. Punjab coal contains high amounts of ash (34.70%) and sulfur (8.34%). Float-sink tests conducted on several size fractions disclosed that 16% target ash could be achieved at an overall yield of 63% with ash and sulfur rejection values in the range of 72.63–94.18% and 73.01–88.45%, respectively. However, the sulfur limit of 1.0% would be difficult to meet. Dell release analysis performed on – 0.25 mm fraction revealed poor flotation response of Punjab coal. Several process flowsheets were designed and simulated using LIMN to generate data for yield, ash and sulfur. End-User Beneficiation Number (EBN) was introduced and utilized for determining the best processing option that can provide maximum yield while meeting the quality requirements of the end-user. Economic analysis involving CAPEX, OPEX, and payback period validated the merit of EBN.

Improved Flotation Recovery and Selectivity of an Ultra-Fine Brazilian Phosphate Ore Using Eriez’ Column Flotation Technology

Eriez Flotation Division recently completed column flotation testing of two igneous phosphate ore samples from the Tres Estradas deposit as part of Aguia Resources’ bankable feasibility study for the greenfield project. Due to fine dissemination of the phosphate and associated grinding requirements, column flotation was selected for the metallurgical test program to address the inherent limitations of fine particle flotation using conventional mechanical flotation cells. Eriez’ column flotation cells with Cavitation-Tube spargers are a commercially-mature and efficient technology for flotation of fine particles that may otherwise not be feasible using conventional flotation machines. Accordingly, continuous column flotation pilot tests were conducted by Eriez on two ultra-fine (212x0 µm) samples of Tres Estradas carbonatite ore (fresh and oxidized) to determine flotation responses and develop an industrial circuit design. Using Eriez’ automated multi-stage column flotation circuit, the fresh carbonatite ore was upgraded from 3.6-4.1% P2O5 to 30-32% P2O5 at a P2O5 recovery of 71-80% using a rougher-scavenger-cleaner-cleaner circuit configuration. Similarly, the oxidized (saprolite) carbonatite ore was upgraded from 10.0-11.5% P2O5 to 32-33% P2O5 at a P2O5 recovery of 85-90% using a rougher-cleaner column circuit configuration. The benefits of Eriez’ column flotation technology realized from this test work include a higher degree of selectivity, increased recovery, and reduced collector dosage as compared to bench-scale mechanical flotation. Specifically, the recovery of fresh carbonatite and oxidized (saprolite) carbonatite ore by column floatation increased 2-3% and 5% respectively, while collector dosage was reduced by 20-40% and the required number of cleaning stages to achieve the target concentrate grade was reduced.

Optimization of chlorite and talc flotation using experimental design methodology: Case study of the MCG plant, Morocco

SYNOPSIS Response surface methodology (RSM), central composite design (CCD), and desirability functions were used for modelling and optimization of the operating factors in chlorite and talc (collectively termed 'mica') flotation. The influence of pulp pH, cyanide (NaCN) consumption, and particle size was studied with the aim of optimizing ssilicate flotation while minimizing recoveries of galena, chalcopyrite, and sphalerite. Flotation tests were carried out on a representative sample of a complex sulphide ore from Draa Sfar mine (Morocco). The model predictions for the flotation of each of the minerals concerned were found to be in good agreement with experimental values, with R2 values of 0.91, 0.98, 0.99, and 0.90 for mica, galena, chalcopyrite, and sphalerite recoveries, respectively. RSM combined with desirability functions and CCD was successfully applied for the modelling of mica flotation, considering simultaneously the four flotation responses to achieve the maximum recovery of mica and minimal loss of Pb, Cu, and Zn to the flotation concentrate. Keywords: chlorite, talc, flotation, response surface methodology, central composite design, optimization.

Surface features and flotation behaviors of spodumene as influenced by acid and alkali treatments

Surface dissolution was proved as a fundamental phenomenon in the flotation of spodumene. This study presents an improved understanding of surface dissolution behavior and the corresponding surface states involving consideration of topography, chemical species distribution, as well as oleate adsorption at spodumene surface treated by sodium hydroxide (NaOH) and hydrochloric acid (HCl). Micro-flotation results showed that spodumene flotation was activated with NaOH treatment but was depressed with HCl treatment when sodium oleate was used as a collector. AFM imaging revealed variations in surface topography, indicative of different dissolution behaviors. Water rinsing treatment increased flotation response of NaOH-treated spodumene but had no effect in the case of HCl treatment. Colloidal substances precipitated at surface conditioned in NaOH solution as evidenced from in-situ AFM, and appeared to be unfavorable for oleate adsorption. Chemical states of elements at surface were influenced by treatments, and larger relative contents of Al and unsaturated Al at surface with NaOH treatment were revealed by XPS as compared with that treated by HCl. Density functional theory calculations indicated that unsaturated Al was favorable for oleate adsorption. It seems the relative content of unsaturated Al at surface influenced by acid and alkali treatments dominates the extent of oleate adsorption.

Flotation of Calcium Minerals with Combination of Reagents of Different Molecular Structure

The influence of non-ionic compounds in combination with sodium oleate on the contrast behavior of flotation response of calcium minerals is investigated theoretically and experimentally. The flotation and adsorption analyses are carried out with monomineral fractions of calcite and scheelite, while the flotation process analysis is conducted with an ore material screened into size grades of -44 and -15 urn. The process conditions of the highest difference in adsorption of oleate and contrast in extraction of scheelite and calcite are found. The conditions of the maximum depression of calcite in the rougher flotation circuit are determined.

The effect of carbon dioxide and nitrogen on pyrite surface properties and flotation response

In 1997 Newmont USA Ltd. introduced the N2TEC process for the flotation recovery of auriferous pyrite and other sulfide minerals in Carlin type ores, using nitrogen as the flotation gas, and low pH to prevent oxidation and hydrolysis of the pyrite surface. However, increased amounts of carbonate gangue minerals in certain Carlin type ores adversely affect the flotation recovery due to difficulties with pH control in the presence of carbonate minerals, i.e. calcite, dolomite, etc. Subsequently, it was discovered that by using CO2 for flotation, the pH of the system can be more effectively controlled, and consequently the recovery and rate of pyrite flotation can be improved significantly.In our current laboratory research on pyrite flotation chemistry these results were confirmed, as both fresh and oxidized pyrite particles exhibited an increased flotation response in CO2 saturated solution. It was found that the water contact angle at the pyrite surface increased in CO2 and N2 saturated solutions, while surface oxidation and bubble attachment time decreased. In addition to decreased surface oxidation and the influence of pH on surface hydrolysis, the significance of bubble attachment phenomena in these CO2 flotation systems helps to explain the improved flotation response.

Investigation into the flotation of malachite, calcite and quartz with three phosphate surfactants

The flotation response of malachite, calcite and quartz to bis (2-ethylhexyl) phosphate (DEHPA), dibutyl phosphate (DBP) and tributyl phosphate (TBP) was evaluated by micro-flotation experiments. The results showed that DEHPA exhibited an impressive flotation selectivity for malachite against calcite/quartz in the pH range of 6.0–9.0 and achieved superior malachite flotation recovery over DBP and TBP. The flotation mechanism of DEHPA to malachite was farther investigated through adsorption, contact angle, zeta potential, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The findings inferred that DEHPA reacted with the surface copper atom of malachite via its O atoms of POH and PO to form the hydrophobic surface complexes of Cu(II)-DEHPA. The double active center of the P(O)OH group might be contributed to the stronger affinity of DEHPA and DBP to malachite than that of TBP with the single active center of the PO group. TBP returned the lowest malachite recovery among the three phosphate surfactants, even it has more hydrophobic-carbon atoms than those of DBP.

The link between particle size and froth stability - Implications for reprocessing of flotation tailings

Abstract Historic tailings dams can often be considered as valuable mineral reserves due to the declining head grades of primary deposits. The reprocessing of such material is of great interest to the minerals processing industry, not only from an economic point of view, but also from an environmental one. However, tailings material is generally comprised of fine particles, which poses a challenge for its reprocessing using froth flotation due to reduced recoveries of these particle sizes. In addition, there is some debate as to the effect that these fine particles have on the froth stability, which in turn is linked to mineral recovery. In this work, air recovery was used as a measure of froth stability to determine the flotation response of a copper tailings ore to changes in particle size distribution and superficial gas velocity. The system exhibited a maximum in air recovery, which correlates well with the local peak in dynamic froth stability presented in previous work. This maximum in froth stability is also shown to correspond to an improvement in flotation performance, thus highlighting the importance of considering the link between particle size, air rate and froth stability when determining the flotation strategy for tailings reprocessing. The results are discussed in terms of the implications for the reprocessing plant from where the ore samples were obtained and, more generally, for the efficient flotation reprocessing of tailings.

The relationship between the flotation behaviour of a mineral and its surface energy properties using calorimetry

Surface energy defines the wettability of a mineral surface, which is of great importance in separation by flotation. Surface energies can be calculated and separated into their polar and non-polar components by measuring the enthalpy of immersion of a finely divided mineral powder in a number of probe liquids. In this study, the enthalpies of immersion of different isolated pure minerals in water, formamide and n-hexane were determined using a precision solution calorimeter. The van Oss-Good-Chaudhury (VGC) model was applied to systematically characterise the surface energy components of the minerals. A microflotation system was also employed to determine the flotation responses of the different minerals.The enthalpy of immersion technique was capable of differentiating the surface energies of isolated pure minerals. The relative strength of the surface energies and their components was dependent on the mineral type. The work of adhesion of water and the interfacial energy of interaction between particles and bubbles immersed in water correlated well with the enthalpy of immersion in water and were both inversely related to the flotation response of the minerals. The results are intended to provide a firm foundation for the investigation of the wettability of mineral mixtures, composite particles and simple ores using the enthalpy of immersion technique.

Adsorption behavior of mixed dodecane/n-valeric acid collectors on low-rank coal surface: Experimental and molecular dynamics simulation study

In this investigation, a mixed collector (MC) of dodecane and n-valeric acid was used to improve low rank coal flotation. Fourier transformation infrared spectroscopy (FTIR) measurements and contact angle measurements were conducted to explain flotation responses. Furthermore, using a molecular dynamics (MD) simulation, the changes of water/collector (dodecane or MC)/coal systems were studied before and after adsorption to indicate the absorption behavior and mechanism. The results showed that a better flotation performance of low-rank coal was obtained using the MC compared to a conventional collector of dodecane. The hydroxyl (OH) or carbonyl (CO) or carboxyl (COOH) migration of the coal with the MC was stronger than that with dodecane as a solo collector, and the MC can enhance the hydrophobicity and lipophilicity of the coal surface. MD simulation results revealed the adsorption behavior of the MC on low-rank coal surfaces. Dodecane was mainly adsorbed on the hydrophobic surface of coal, and n-valeric acid was more inclined to act on the oxygen-containing functional group of coal, i.e., a hydrophilic surface. The mobility of = dodecane molecules on the coal surface was reduced owing to the presence of n-valeric acid, which increased the lipophilicity and hydrophobicity of the low-rank coal surface, thus attracting dodecane molecules of the MC and restricting their movement, and accelerating the departure of water molecules from the low-rank coal surfaces. There was also a higher interaction energy between the MC and low-rank coal. The simulation results are in good agreement with the measured results; this effectively explains the flotation results.

Correlation of surface oxidation with xanthate adsorption and pyrite flotation

Various studies have emphasized the importance of surface oxidation of sulfide minerals with regard to xanthate adsorption and their flotation response. However, the correlation between pyrite surface oxidation, xanthate adsorption and its flotation response has not been clearly established. The complexity lies in various intermediate sulfur oxidation products in different solution conditions. Thus, investigation of sulfur oxidation behavior is the key to understand pyrite oxidation. Ion chromatography (IC) and high performance liquid chromatography (HPLC) results showed an increase in the total amounts of occurring sulfur species with increasing slurry pH. Meanwhile, the ratio of S0/sulfur oxyanions was to become lower; X-ray Photoelectron Spectroscopy (XPS) identified the oxidized pyrite surface was rich in SO42− and FeOOH. Both the contact angle results and single mineral flotation data indicated that the more pyrite surface oxidized, the lower hydrophobicity and floatability were. Time-of-flight secondary ion mass spectroscopy (Tof-SIMS) was adopted to analyse xanthate adsorption on the surface of pyrite under conditions of either sufficient oxidation or on freshly polished surface which is assumed little oxidation. A significantly lower intensities of C4H9O and C4H9OCSS was found on the intensely oxidized pyrite surface, indicating xanthate adsorption had strong selectivity on FeS2 rather than FeOOH. The experimental results were further confirmed by theoretical calculation. The self-consistent charge density functional tight binding (SCC-DFTB) calculations indicated that the distances between the xanthate S atoms and surface Fe atoms of FeOOH were larger than the atomic radius of SFe. Essentially, the different electron configurations of their Fe atoms led to the selective adsorption of xanthate on FeOOH and FeS2 surfaces in terms of the coordination chemistry theory. This work provides valuable implications for understanding the correlation of surface oxidation, xanthate adsorption and its floatation behavior to mediate pyrite flotation.