Froth Properties Research Articles

Reproducing high mechanical load during industrial processing of UHT milk: Effect on frothing capacity

In this study, possible reasons for an increased level of free fatty acids (FFAs) in Ultra-High Temperature (UHT) treated full fat (3.5% wt/wt) milk and its effect on the frothing properties of milk were investigated. Lipolysis of raw milk from 2 different breeds of cattle (Holstein and Jersey) was induced by mechanical stress and kinetics of lipolysis were compared. Frothing capacity and foam stability of shelf stable milk with different concentrations of FFAs were determined, with a good to medium initial foam volume for up to 4 mEquiv FFA · (100 g fat)-1 fat and poor foam stability with >2 mEquiv FFA · (100 g fat)-1. A combination of mechanical stress and initial condition of fresh raw milk was found to trigger lipolysis and potential sources of mechanical stress during milk processing were identified.

A case study of enhanced flotation of coal gasification fine slag by multiple compound collectors

ABSTRACT The flotation mechanism of multiple compound collectors called ZKC-I for coal gasification fine slag (CGFS) was revealed from the flotation kinetics, adsorption properties, bubble–particle interaction, and froth properties. The results were compared to dodecane, which represents the conventional nonpolar hydrocarbon oil collector. The flotation concentrates yield and rate constant of CGFS treated by ZKC-I were 2–3 times than those of CGFS treated by dodecane. Fourier transform infrared spectroscopy and wrap angle results showed that ZKC-I improved the hydrophobicity of residual carbon because of the synergistic adsorption of fatty acids, esters, and aromatic hydrocarbons in the ZKC-I on the heterogeneous surface of residual carbon particles, which enhanced the adhesion between residual carbon particles and bubble. Due to the strong carrying capacity of the bubble to residual carbon particles, the number of residual carbon particles in the froth treated by ZKC-I was more than that of the CGFS froth treated by dodecane. The high content of carbon particles in the froth resulted in great stability of the flotation froth, and the maximum height and half-life of the froth were higher than that of CGFS treated by dodecane. This study has practical and theoretical significance for the separation of coal-based solid waste.

Nanoparticle depressants in froth flotation – The effect of colloidal silica with different size and surface modifications on the selective separation of semi-soluble salt type minerals

Colloidal silica has been presented as a selective depressant in froth flotation separation of scheelite and calcite by our group in 2020. Here we analyze the effects of colloidal silica dosage, specific surface area (i.e. size), and modification with microflotation on pure scheelite, calcite, fluorite, and apatite minerals. In a reagents scale-up procedure batch flotation experiments were conducted on a low-grade scheelite ore using statistical experimental design methodology. Microflotation experiments showed colloidal silica selectively depressing calcite flotation with increasing intensity with reduced size of colloidal silica. The nanoparticulate depressant did not affect the recoveries of scheelite, apatite, and fluorite – typical ore minerals that occur associated with calcite. Batch flotation of a low-grade scheelite ore confirmed the observations made at the microscale: colloidal silica significantly improves the scheelite-calcite selectivity index. Here, we observe a series of relations between colloidal silica specific surface area and modification on different process indicators such as scheelite-calcite selectivity index, recoveries, and froth properties. These relations are assumed to be due to the different aggregation mechanisms of the colloidal silica dispersions. The aluminate-modified colloidal silica, which tends to form a coherent gel network in the presence of Ca2+, shows the strongest effect on reducing calcite recovery accompanied by a significant reduction in scheelite recovery compared to the non-functionalised and silane-modified colloidal silica.

Flotation performance and adsorption mechanism of 2-triethylenetetramine methylene-4-nonylphenol to pyrochlore

The flotation performance and adsorption mechanism of 2-triethylenetetramine methylene-4-nonylphenol (TMNP) on pyrochlore were investigated through micro-flotation experiments, zeta-potential tests, contact angle and XPS measurements. Additionally, the frothing properties of TMNP were studied using froth volume and surface tension tests compared with DDA. The flotation results showed that TMNP exhibited strong collecting ability for pyrochlore, but showed no selectivity towards quartz or feldspar. Separation experiments showed sodium aluminium silicate was an effective depressant for the separation of pyrochlore, feldspar, quartz, and calcite. The frothing properties of both TMNP and DDA were correlated with their respective surface tensions. Contact angle experiments demonstrated contact angle increased with increasing concentrations of TMNP and DDA. Zeta potential indicated that TMNP might adsorb onto pyrochlore surfaces through electrostatic attraction and chemical adsorption while DDA only exhibited physical adsorption. XPS data provided further evidence for the chemical adsorption of TMNP onto pyrochlore surfaces.

Effect of clay crystal structure on froth rheology in flotation

It has been well acknowledged that clay minerals could impose deleterious effects on flotation performance by affecting pulp rheology. To date, it is still not clear regarding the role of clay minerals in influencing froth rheology which has been increasingly recognized as an important froth property in determining flotation performance. Hence, this work selected three typical clay minerals with different characteristics to study their impacts on froth rheology: montmorillonite, kaolinite and talc. The results showed that the clay minerals showed different froth rheological behaviors with increasing the solids concentration in the feed from 1 wt% to 9 wt%. For montmorillonite, the froth viscosity decreased first and then increased, reaching a lowest viscosity at 5 wt%. The froth viscosity continuously decreased for kaolinite while it kept increasing for talc over the solids concentration in the feed. In addition, talc generated much more viscous froths than the other two clays. The different varying behaviors of froth viscosity among the three clays were related to clay crystal structure and surface hydrophobicity which ultimately determined froth properties. It is believed that the outcomes of this study could facilitate the flotation optimization of complex ores with the presence of clay minerals.

Effects of carrier particles on flotation removal of unburned carbon particles from fly ash

Fly ash, a major by-product of coal-fired power plants, contains unburned carbon which poses challenges to its effective utilization. The flotation separation efficiency of unburned carbon from fly ash is limited due to the ultrafine size and poor hydrophobicity of the unburned carbon. This study introduces carrier flotation as an efficient method for removing unburned carbon from fly ash. Experimental results indicated that the use of carrier particles (low ash content coal particles) significantly enhanced the flotation removal efficiency of unburned carbon from fly ash compared to conventional methods. The enhancement mechanism was evaluated by examining the differences in flotation froth properties, particle aggregation behaviors, and extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) interaction energy in the presence and absence of hydrophobic carrier particles. Hydrophobic carrier particles were found to increase the stability of the flotation froth layer, facilitate the water recovery, and aid in the removal of fine unburned carbon particles. Focused beam reflectance measurement (FBRM) confirmed that the presence of hydrophobic carriers promoted the aggregation of fine unburned carbon particles, thereby increasing bubble-particle collision probability. Furthermore, EDVLO theory calculations revealed that the attractive interaction energy between carrier particles and unburned carbon particles was stronger than that between carrier particles and ash particles. Therefore, carrier flotation shows promise as a highly efficient method for removing unburned carbon from fly ash.

Effects of Sec-Octanol and Terpineol on Froth Properties and Flotation Selectivity Index for Microcrystalline Graphite

Microcrystalline graphite is a valuable non-metallic mineral that can be separated by flotation, a physico-chemical processing method that uses air bubbles to capture mineral particles. The size and stability of the bubbles, which depend on the type and amount of frother added, affect the flotation performance and the recovery of water from the froth layer. However, the effects of different types of frother on the froth properties and water recovery of microcrystalline graphite flotation are not well understood. In this study, two common frothers, sec-octanol and terpineol, were compared in terms of their effects on the bubble size, froth layer height, water recovery, and flotation selectivity index (SI) of microcrystalline graphite flotation. It was found that sec-octanol produced smaller bubbles than terpineol, but also a slightly lower froth layer height. The water recovery was higher with sec-octanol than with terpineol. The SI values were similar for both frothers, indicating comparable flotation performance. This study revealed the differences between sec-octanol and terpineol in terms of their effects on the froth properties and water recovery of microcrystalline graphite flotation. These findings can help optimize the choice and dosage of frother for this important mineral processing method.

Toxic heavy metal ions removal from wastewater by ion flotation using a nano collector

Industrial wastewater treatment containing heavy metal ions has been a challenge in the ion flotation process development in recent years due to the high collector consumption required to achieve maximum ion removal. To address this issue, a nano collector consisting of functionalized graphene oxide (FGO) was synthesized and applied to increase the removal of heavy metal ions (lead, copper, nickel, cadmium, and zinc) from wastewater. This study evaluated the effect of various critical operating conditions including pH, collector/frother type and concentration, gas type, gas flowrate, and energy input on ion flotation performance to improve the efficiency of the process in this investigation. It was found that using FGO not only increased the ion removal percentage but also decreased collector consumption and water recovery, all of which improved the ion flotation process performance. Under the optimum chemical and hydrodynamic conditions using FGO with much lower concentration than stoichiometry concentration resulted in the maximum removal of lead, copper, nickel, cadmium, and zinc ions with percentages of 97.07, 99.02, 98.38, 95.20, and 98.94, respectively. In optimum condition, water recovery was 8 %. The use of FGO in the ion flotation process for wastewater treatment offered significant benefits, including high adsorption efficiency, low collector consumption, recyclability, and the absence of critical micelle concentration (CMC) and frothing properties.

Regulation role of calcium lignosulfonate on the entrainment behavior of serpentine during brucite recycling: A new perspective

The entrainment behavior of fine serpentine seriously deteriorates the recycling efficiency of brucite. In this paper, the effect of calcium lignosulfonate (CLS) on the flotation separation of brucite and serpentine was creatively investigated using a self-made Hallimond apparatus. The experiments revealed that the entrainment rate of fine-grained serpentine decreased from 1.15 to 0.41 with increasing CLS dosage. The pulp viscosity as well as the surface tension analysis, combined with the froth properties investigated using a Foamscan analyzer, confirmed that after CLS addition, the foam generation time increased, while the average bubble diameter gradually decreased, resulting in a decrease in the fluid content of the foam layer as well as the serpentine entrainment rate. Besides, the results were analyzed mechanistically based on Plateau foam structure equilibrium theory. This paper innovatively provides a feasible approach to minimize the content of fine-grained serpentine in brucite concentrate from the perspective of foam entrainment behavior.

Froth stabilities and iron ore flotation of collectors 3-dodecyloxypropanamine and 3-tetradecyloxypropylamine: An experimental and molecular dynamics study

In the mineral processing industry, froth properties are essential. To separate iron minerals and gangue minerals in a flotation mill, froths that are both too stable and fragile are useless for obtaining qualified concentrate in the mining industry. We tried to develop two collectors to adjust the froth stability during flotation. In this study, we first researched the froth stabilities of collectors 3-dodecyloxypropanamine (DOPA) and 3-tetradecyloxypropylamine (TOPA). Contact angle measurements and surface tension measurements were used to research the hydrophobicity of DOPA and TOPA and to predict its flotation performance. Froth stability measurements and molecular dynamics (MD) were conducted to investigate the froth properties of DOPA, TOPA, and dodecyl amine (DDA), and to reveal the froth mechanism of flotation. The film interface models were built using software Materials Studio 2017 software, and MD was used to simulate the flotation system. The interaction formation energy (IFE) was calculated to compare the froth film strength of the three collectors. Surface tension measurements indicated that DOPA and TOPA were more robust collectors in decreasing water surface tension than DDA. The froth stability measurements showed that the DDA froth was the most stable of the froths with the three collectors, consistent with the MD simulations of the foam models. Furthermore, the adsorption configuration of the interface of DOPA or TOPA and solution was drawn, and the numbers and the average length of different kinds of hydrogen bonds of the three configurations were counted and calculated. We can infer that the hydrogen bonds between the O atom of water and the —NH2 of DOPA or TOPA are not the main force of their IFE, and the main force is van der Waals force. Finally, the micro-flotation of the artificial mixed mineral was conducted to verify the previous prediction of DOPA and TOPA. This paper provided a new case to adjust the flotation performance by developing a collector and predicting its froth stability.

Impact of Sodium Hexametaphosphate on the Flotation of Ultrafine Magnesite from Dolomite-Rich Desliming Tailings

The depletion of ore deposits, the increasing demand for raw materials, the need to process low-grade, complex and finely disseminated ores, and the reprocessing of tailings are challenges especially for froth flotation separation technologies. Even though they are capable of handling relatively fine grain sizes, the flotation separation of very fine and ultrafine particles faces many problems still. Further, the flotation of low-contrast semi-soluble salt-type minerals with very similar surface properties, many complex interactions between minerals, reagents and dissolved species often result in poor selectivity. This study investigates the flotation beneficiation of ultrafine magnesite rich in dolomite from desliming, currently reported to the tailings. The paper especially focuses on the impact of the depressant sodium hexametaphosphate (SHMP) on the following: (i) the froth properties using dynamic froth analysis (DFA), (ii) the separation between magnesite and dolomite/calcite, and (iii) its effect on the entrainment. As a depressant/dispersant, SHMP has a beneficial impact on the flotation separation between magnesite and dolomite. However, there is a trade-off between grade and recovery, and as well as the dewatering process which needs to be considered. When the SHMP increases from 200 g/t to 700 g/t, the magnesite grade increases from 67% to 77%, while recovery decreases massively, from 80% to 40%. The open circuit with four cleaning stages obtained a concentrate assaying 77.5% magnesite at a recovery of 45.5%. The dolomite content in the concentrate is about 20%, where 80% of dolomite was removed and importantly 98% of the quartz was removed, with only 0.3% of the quartz in the final concentrate. Furthermore, the application of 1-hydroxyethylene-1,1-diphosphonic acid (HEDP) as a more environmentally friendly and low-cost alternative to SHMP is presented and discussed. Using only 350 g/t of HEDP can achieve a similar grade (76.3%), like 700 g/t of SHMP (76.9%), while obtaining a 17% higher magnesite recovery as compared to 700 g/t of SHMP. Interestingly, the proportion of hydrophilic quartz minerals ending up in the concentrate is lower for HEDP, with only 1.9% quartz at a recovery of 21.5% compared to the 2.7% of quartz at a recovery of 24.9% when using SHMP. The paper contributes in general to understanding the complexity of the depressant responses in froth flotation.

Correction of froth gray value in the prediction of clean coal ash content in coal flotation

ABSTRACT The correlation between froth properties and the quality of the froth product is the key to predict flotation performance and improve the automatic control of flotation. It is known that froth gray value increases with the clean coal ash content and is often used in the prediction of coal flotation performance. But the accuracy of ash content prediction is usually unsatisfactory because the froth gray value can be easily interfered by the circumstance. In this study, the average gray value of the black experimental table was selected as the reference block to correct the froth gray value. The inaccurate froth gray value was corrected by the initial gray value and the gray value fluctuation of the reference block. The R2 of the linear fitting between froth gray value and clean coal ash content increased from 0.64 to 0.93 after the correction. This work showed that the correction method can significantly improve the accuracy of flotation performance prediction by gray value.

Differences in Etheramines Froth Properties and the Effects on Iron Ore Flotation. Part II: Three-Phase Systems

ABSTRACT Part I of this investigation, addressing two-phase systems, showed that etherdiamine produces more stable and dryer foams, whereas smaller bubbles are formed with faster kinetics by ethermonoamine. These remarkable differences in foam stability, attributed to the distinct chain length and consequent hydrophilic–lipophilic balance, influence froth properties, and may affect the selectivity of reverse cationic flotation of iron ores. The investigations conducted in this paper evaluated the effect of froth properties on the selective flotation recovery of a Brazilian iron ore from the Iron Quadrangle. The results showed that etherdiamine presented faster kinetics of froth formation but the recovery of water and solids in the froth was lower than that achieved with ethermonoamine. The water recovery was closely related to nonselective transport of solid particles in the froth by entrainment. The etherdiamine ability to form more stable and dryer froth reduced the entrainment of fine iron-bearing particles in the froth (tailings), improving the metal recovery in the concentrate (bulk), as the iron loss was directly proportional to the water recovery in the froth and the reagent presented lower entrainment factor than the ethermonoamine. In addition, the drier froth from etherdiamine is responsible for greater quartz true flotation, rendering this collector a more selective effect on flotation in spite the more powerful effect of ethermonoamine.

The effects of partially replacing amine collectors by a commercial frother in a reverse cationic hematite flotation

Iron ore froth flotation has recently been used to obtain pure minerals due to the depletion of high-grade deposits. Amine collectors have often been used in cationic reverse iron ore flotation to achieve the separation with quartz impurities. The main problem associated with these collectors is related to the control of frothing properties and the high cost of amine reagents. In this paper, we report the benefits of partial replacement of amine collectors with a frother in reverse cationic flotation of hematite. Surface tension and batch flotation experimental results indicated for the first time that replacing Flotigam EDA, an etheramine collector by more than 10% improved the flotation performance in both grade and recovery of hematite. It was also noted mild hematite entrainments for lower frother dosages whilst reagents cost estimation indicated profitability per ton of iron recovered. At higher frother dosage however, higher quartz recoveries were observed as a result of entrainment which led to satisfactory results in terms of iron grade in the sink, but results showed higher costs of reagents than when collector was used alone. From observed results, it was concluded that partially replacing amine collector by a frother does improve the performance of the flotation globally regardless of pronounced entrainment that was mainly due the mineralogy of the ore with notable amounts of locked particles in the lower sizes. Finally, it would be useful to investigate these findings with alternative reagents and on minerals with different mineralogical properties.

Differences in Etheramines Froth Properties and the Effects on Iron Ore Flotation. Part I: Two-Phase Systems

ABSTRACT Etheramines are quartz collectors and also play a role as frothers in cationic reverse flotation of iron ores. While the adsorption of this surfactant on quartz surface has been widely investigated, the impact of its foam/froth properties on the selectivity in iron ore flotation has not yet been addressed in detail. The structural differences between ethermonoamine and etherdiamine result in distinct adsorption and frothing properties, offering versatility in the concentration of hematite. This study addressed the effect of the etheramine type on flotation selectivity, focused on the analysis of frothing properties. The characterization of the surfactants in the pure state and in two-phase systems (liquid/air) was conducted to investigate the behavior of etheramines concerning foam forming and stabilization. The surface tension measurements showed greater activity of etherdiamine at the liquid–air interface in comparison with ethermonoamine, which was more effective to prevent bubble coalescence and produce smaller bubbles, despite the reagent’s higher critical coalescence concentration. Ethermonoamine presented faster foamability for concentrations greater than the observed critical coalescence concentration values as well as greater water recovery in foam, whereas the double CH2 group and higher molecular weight imparted strong lipophilic character to etherdiamines, producing drier, voluminous, and more stable foams, with longer lifetime. These results are fundamental for the evaluation of three-phase systems, which will be presented in a subsequent paper.

Effect of air dissolved in water on simultaneous ultrasonic-assisted coal flotation

ABSTRACT The effect of air dissolved in natural water on simultaneous ultrasonic-assisted coal flotation was investigated combined with flotation tests, froth properties and flotation kinetics models analysis. Compared with degassed water, the better flotation performance was obtained in natural water when ultrasound was not used or ultrasonic power was lower than 200 W. For the low ultrasonic power (< 200 W), the air dissolved in natural water promoted the precipitation of bubbles to obtain the small bubble and thick froth layer, which was beneficial to improve the coal flotation. However, the froth properties in natural water were almost the same as those in degassed water if the ultrasonic power was reached to 200 W, indicating that the performance of ultrasonic flotation in degassed water was almost the same as that in natural water. In addition, the processes of ultrasonic-assisted coal flotation in natural and degassed water could be described by the second-order model with rectangular distribution of floatability. The ultrasonic flotation rate of natural water was twice than that of degassed water. Hence, these above results made a contribution to improve the performance of ultrasonic-assisted coal flotation in natural water.

Effects of froth properties on dewatering of flotation products– A critical review

The presence of tenacious froth in flotation products has a detrimental effect on the downstream dewatering process, which is a challenge in processing plants of a range of commodities, such as coal, talc, molybdenum, bitumen, potash, zinc, copper and gold. The generation of tenacious froth is not only related to the properties of mineral particles but can also be affected by water salinity and the presence of clay minerals. In this article, the effects of stable froth on the dewatering of flotation products were presented. Froth properties including froth structure, froth stability and froth rheology were presented first and then recent studies on the influence of froth on dewatering process were reviewed. Finally, future directions of research to increase the dewatering efficiency of flotation products are recommended.

Application of compound reagent H511 in the flotation removal of unburned carbon from fly ash

This article aims to study the effect of flotation reagent H511 on the removal of unburned carbon (UC) from fly ash. The gas chromatography/mass spectrometry revealed that the main components in H511 were cyclohexanol, d-limonene, longifolene, and 2-cyclohexylidene-cyclohexanone. It is found that the H511 could reacted with the UC surface through zeta potential tests. The induction time indicated that the H511 had a greater positive effect on the adhesion between UC particles and the bubble than diesel. The froth property test indicated that the flotation pulp treated by the H511 had great froth stability due to the effect of cyclohexanol in H511. The flotation showed that the carbon removal rate of H511 was approximately 60 % higher than that of the diesel/sec-octyl alcohol. Fly ash particles with loss on ignition less than 8% can be obtained by H511. This study have great influence for removing UC from raw fly ash and obtaining high-quality, low loss on ignition (LOI) fly ash resources.

Effect of ultrafine kaolinite particles on the flotation behavior of coking coal

Kaolinite, as a mineral in fine coal, has an important influence on the flotation of coal particles. In this study, the effects of ultrafine kaolinite particles on the flotation recovery of coal particles were investigated. Flotation tests were carried out using a mixture of coal particles and different amounts of ultrafine kaolinite particles. Combined with the Stefan–Reynold theory, the effect of liquid film drainage rate between coal bubbles in a kaolinite suspension was calculated. The yield of flotation clean coal increases quickly with the increasing content of ultrafine kaolinite particles. The ultrafine kaolinite particles can reduce the surface tension of the suspension, weaken the bubble coalescence, and stabilize the structure of the froth layer. In addition, the ultrafine kaolinite particles increase the apparent viscosity of the flotation pulp slightly. It is concluded that the role of ultrafine kaolinite particles on the positive effect of froth properties conceals the negative effect on the liquid film drainage rate between coal particles and bubbles caused by the kaolinite particles, which ultimately leads to an increasing yield of clean coal with an increasing content of kaolinite particles. This study is important for understanding the influence of ultrafine kaolinite on coal particle flotation.

Improving the flotation performance of an oxidized bituminous coal source

Numerous studies have been conducted describing the challenges with oxidized coal flotation. Common industrial collectors such as fuel oil are typically ineffective under natural conditions for the flotation of oxidized coal sources such as the Coalburg seam from the Central Appalachia coalfields of the U.S. Low plant flotation recovery values of less than 30% were realized in part due to the weak surface hydrophobicity and the clay coating that results from a reduced isoelectric point of the coal and low slurry pH values. Elevated pH values and the use of a model collector containing carboxylic groups improved flotation recovery values by nearly 45 absolute percentage points. Operating at pH values around 7.5 to disperse the clay slimes and provide more surface active dimer complexes produced from a carboxyl collector resulted in excellent flotation recovery values for a hard-to-float coal. Due to the frothing properties of the carboxyl collector, column flotation with froth washing was needed to provide product ash values as low as 7.5%.