Critical Coalescence Concentration Research Articles

Correlation of Flotation Recoveries and Bubble–Particle Attachment Time for Dodecyl Ammonium Hydrochloride/Frother/Quartz Flotation System

Recent studies in the flotation of fine particles have necessitated new techniques and analyses for developing various strategies. Particularly, the improvements in flotation chemistry including the selection of the type of frother, collector, and other reagents have become very significant. In this study, the effect of different commercial polypropylene glycol frothers (PPG200, 400, and 600) in the presence of dodecylammonium hydrochloride (DAH) was investigated for their contribution to flotation recoveries and bubble–particle attachment time values of fine quartz minerals. Zeta potential measurements with DAH were also carried out as a function of pH and reagent concentration to justify the effect of collector usage alone on the charge of particles. A linear increase in flotation recoveries against collector concentration, e.g., 7.4% recovery at 1 × 10−5 mol/L DAH and 65.4% recovery at 1 × 10−3 mol/L DAH, was obtained. In this context, the contribution of frothers was particularly important in that a recovery of 15.91% in the absence of the frother and a modest increase to 19.70% was obtained upon the addition of PPG600 at its critical coalescence concentration (CCC) of 3 ppm. Finally, a strong correlation was found between the bubble–particle attachment time and flotation recovery as a function of collector concentration (lowest attachment time vs. highest flotation recovery). The latter correlation is very promising because bubble attachment time leads to various micro-mechanisms in flotation including bubble film thinning, bubble rupture, and induction time, and consequently, frother efficiency in the presence and absence of a collector. As a result, the experimental findings were gathered to achieve a consistent base for further fundamental studies on the application of the synergistic effect of frothers and collectors in the flotation of fine particles.

THE EFFECT OF NITROGEN AND PHOSPHORUS ON THE AGGREGATION OF SOIL COLLOIDAL PARTICLES IN THE THREE GORGES RESERVOIR AREA

Nitrogen (N) and phosphorus (P) concentrations in tributaries and bays of the Three Gorges Reservoir area increase significantly after impoundment. It will affect processes such as coalescence/dispersion of soil colloidal particles, which in turn will affect the ecological safety of the reservoir water bodies. We analyzed the aggregation process of purple soil colloidal particles, and found that aggregation was controlled by the interaction of N and P. With the increase of N and P concentration in the water body, purple soil colloidal particles transformed from slow aggregation (represented by linear growth) to fast aggregation (represented with a power function). We chose three forms of purple soil (acidic, calcareous, and alkaline) to check how interactions between nutrients and physical aggregation processes may vary across soil types. Average aggregation rate (TAA) of the three purple soils differed significantly, and the critical coalescence concentration (CCC) of neutral, alkaline, and acidic purple soils was 220.14, 117.49, and 47.20[Formula: see text]mmol[Formula: see text]L[Formula: see text] and 507.49, 437.15, 328.30[Formula: see text]mmol[Formula: see text]L[Formula: see text], respectively. Compared to phosphorus, the nitrogen system has higher TAA and lower CCC, indicating that nitrogen is more effective in triggering colloidal aggregation of purple soils. In the N and P systems, the surface potentials of neutral, alkaline and acidic purple soils decreased from −172.85[Formula: see text]mV to −70.28[Formula: see text]mV and −187.65[Formula: see text]mV to −81.98[Formula: see text]mV, respectively. With the increase of N and P concentrations, the surface charge density and the absolute surface potential values of the three purple soil colloids decreased, the surface potentials of the three purple soil colloids (absolute values) at the same concentration showed that P was greater than N. Meanwhile, the activation energy of interaction of all three purple soil colloids decreased continuously with the increase of N and P concentrations, and the activation energy of interaction in the N system was significantly lower than that in the P system under the same concentration conditions. Theoretical calculations showed that N and P changed the surface charge properties of the soil and increased the net gravitational force between colloidal particles, which made the net force behave as attraction and colloidal particles were more likely to agglomerate. When the N and P concentrations increased to 0.2, 0.1, 0.05[Formula: see text]mol[Formula: see text]L[Formula: see text], and 0.5, 0.4, 0.3[Formula: see text]mol[Formula: see text]L[Formula: see text], respectively, they were basically consistent with their CCC values. The net force between the three purple soil particles was negative and behaved as attraction. The surface potentials at the corresponding concentrations were all about −125[Formula: see text]mV. This study showed that N and P in the water body ultimately affected the aggregation process of soil colloids by changing the surface charge properties of particles, which in turn causes changes in the interaction forces and activation energy between colloidal particles.

The Role of Stereological Assumptions in Bubble Size Estimations and Their Implications for Assessing Critical Coalescence Concentrations

Accurate measurement of bubble size is critical for assessing flotation performance. However, the 3D nature of bubbles, in contrast to the 2D nature of photographs obtained using a bubble viewer apparatus, may lead to distortions related to stereological assumptions. This study aimed to quantify the impact of these stereological effects on bubble size measurements in frother characterisations. Our results showed that different assumptions regarding bubble shape and volume resulted in variations in bubble size calculations of up to 10%. Furthermore, these stereological effects were propagated to the calculation of the critical coalescence concentration, leading to uncertainties of up to 14% depending on the type of frother. These findings emphasise the importance of considering stereological effects and selecting an appropriate calculation method when measuring bubble size for flotation and reagent assessments.

Critical coalescence concentration (CCC) of various surfactants used as flotation reagents in mineral

Critical coalescence concentration (CCC) of various surfactants used as flotation reagents in mineral

Classification of flotation frothers – A statistical approach

This paper presents a statistical study to classify non-ionic frothers based on seven frother characteristics, molecular weight (MW), hydrophile–lipophile balance (HLB), critical coalescence concentration (CCC), the minimum sauter mean diameter (DL), dynamic foam stability index (DFI), static foam stability index (SFI), and decay rate index (DRI). A principal component analysis (PCA) was conducted to transform the seven frother characteristics into uncorrelated variables called principal components. The first principal component already explained 64.4% of the variance, and the addition of the second and third principal components explained 92.1% of the variance. A hierarchical cluster analysis (HCA) was conducted using the first three principal components. The Euclidean distance, which is the square distance between the standardised coordinates of two frothers in a generalised parameter space, was calculated for all frothers. At a Euclidean distance of 4, frothers were grouped into four groups, in which Group 1 consisted of the most powerful frothers that produced stable foams and Group 4 was composed of weakest frothers.

The effect of inorganic salt on multiphase flow characteristics in a microbubble column: A focus on the ionic strength

AbstractWith enormous interfacial area for particle collection, microbubbles exhibit great application prospect in the mineral flotation. Under certain ionic strength, microbubbles can be produced continuously in the microbubble column without extra reagent addition. In this work, multiphase flow characteristics (Sauter mean diameter, bubble size distribution, gas holdup & interfacial area) were studied systematically with variables including the salt type, salt concentration, and operating conditions. Based on mathematical model, critical coalescence concentration was determined for each investigated salt. According to experimental results, a mathematical correlation was established between the Sauter mean diameter and ionic strength. For the formation of microbubble system, the lowest ionic strength was approximately 0.5 mol/L. Multiphase flow characteristics in the microbubble column depended highly on the ionic strength. The interfacial area and gas holdup increased by 38 times and more than 3 times respectively, with the ionic strength of Al2(SO4)3 rising from 0 to 1.5 mol/L. The critical coalescence concentration ranged from 0.037 mol/L (Al2(SO4)3) to 0.517 mol/L (NaCl), which correlated with the ionic strength of each salt.

Flotation of Carbonaceous Matter from a Double Refractory Gold Ore: The Effect of MIBC on Flotation Performance and Kinetics

The use of alkaline pressure oxidation to pretreat refractory gold ore often results in insufficient gold recovery (<60%) in downstream thiosulfate leaching. To improve gold recovery, flotation was considered for the separation of carbonaceous matter (C-matter). In this study, the effect of MIBC on C-matter flotation was investigated to understand the role of the frother in bubble and froth formation and on flotation kinetics. MIBC dosages between 30 and 150 g/t were used in combination with 500 g/t of kerosene as a collector. The results showed that the recovery and selectivity of C-matter were improved with increasing MIBC dosages. Improved selectivity at higher MIBC dosages was attributed to faster C-matter recovery as bubble size decreased to the critical coalescence concentration (CCC) and to changes to the foam structure. Analysis of flotation kinetics showed that the flotation rate increased as the MIBC dosage increased due to the decreasing bubble size and the reduced induction time caused by the interaction between the collector and the frother. The results of this study explain the role of MIBC in C-matter flotation and can be used as a design basis for scavenger-cleaner flotation testing. Overall, the results show the potential for flotation as a means to improve gold recovery in thiosulfate leaching through the removal of C-matter.

Bubble Size in a Flotation Column with Oscillatory Air Supply in the Presence of Frothers

ABSTRACT Oscillatory air supply has demonstrated advantages over conventional steady air supply in froth flotation with diffused aeration, but the interaction between oscillatory air supply and frother in determining bubble size remained unclear. In the present work, we measured the size of air bubbles in a laboratory scale flotation column with common frothers such as MIBC, Dowfroth 250, and polypropylene glycol with an average molecular weight of 425 (PPG 425), with conventional steady air supply and with oscillatory air supply. The oscillatory air supply was converted from steady airflow using a fast-switching solenoid valve with the main operating parameters being switching frequency and on/off time ratio. In the absence of frother, the Sauter mean bubble diameter (d 32) remained the same with oscillatory air supply replacing steady air supply, but the d 32 decreased by 13–35% in the presence of frother. It was also found that the critical coalescence concentration (CCC) of each frother were reduced by 11–69% using oscillatory air supply to replace steady air supply. The degree of reduction in d 32 or the CCC appeared to be dependent on the oscillatory airflow condition (i.e., frequency and on/off time ratio) and frother type. The present work also confirms the recent findings by others that the CCC is not solely a material property of frothers.

On the frother’s strength and its performance

It is a common rule that the strength of the frother is assessed by either its dynamic foamability index (DFI) or its critical coalescence concentration (CCC). The smaller the value of CCC the stronger the frother is. This general rule (CCC rule) however is superficial although being well accepted. Yet, there are critical questions about the performance of the frothers on the bubbles:1. Are the Gibbs elasticities stemming from the different frothers equally efficient in inhibiting the bubble coalescence?2. How the Gibbs elasticity control the mean bubble diameter for every specific frother?3. How the CCC value of the frothers and the mean bubble diameter are related?This work raises these questions and suggests a rule based on the Gibbs elasticity performance (Gibbs elasticity rule). The performances of seven frothers (PPG 200, PPG 400, PPG 600, BDPG, BTPG, BTEG, and MIBC), whose surface tension isotherms, CCC values, bubble fraction coalescence, and Sauter mean bubble diameter vs. frother concentration were previously studied, were analyzed According to the CCC rule, these frothers follow the order of increasing strength: MIBC≈BTEG < BDPG < PPG 200 < BTPG < PPG 400 < PPG 600. The Gibbs elasticity rule questions what will be the bubble fraction coalescence at a certain fixed value of the Gibbs elasticity of a frother? The above mentioned frothers according to this rule follow the series of PPG 400 < BTPG ≈ BDPG < MIBC ≈ BTEG < PPG 200. Surprisingly, it was established that PPG 600 exhibits abnormal behavior, thus significantly inhibiting the bubble coalescence in a different way, not related to the Gibbs elasticity. For this reason, PPG 600 in the above series was not included. Moreover, correlations between the mean bubble diameter, the Gibbs elasticity, and the CCC value were established. Additionally, a new dimensionless parameter was developed. It estimates the strength of a frother – ζ = ln(Ks.lCH2/α0). A Surprising correlation between the CCC values of 21 frothers and their ζ values was developed. Moreover, it was established a correlation allowing us to calculate the bubble fraction coalescence vs. the frother concentration if the CCC value is known.

Improving aeration systems in saline water (part II): effect of different salts and diffuser type on oxygen transfer of fine-bubble aeration systems.

The objective of the present study is to investigate the different effects on the oxygen transfer of fine-bubble aeration systems in saline water. Compared to tap water, oxygen transfer increases due to the inhibition of bubble coalescence. In Part I of the present study, we investigated in laboratory-scale experiments the effect of design of diffuser membrane. The objective of Part II is the assessment of effects of different salts, diffuser type and diffuser density. We measured the concentration of various salts (MgCl2; CaCl2; Na2SO4; NaCl; KCl) above which coalescence is fully inhibited and oxygen transfer reaches its maximum (referred to as the critical coalescence concentration; CCC). For this purpose, we developed a new analytical approach, which enables investigation of the coalescence behaviour of any aeration system and (mixed) salt solution quickly and easily by evaluating the results of oxygen transfer tests. To investigate the transferability to large scale and the effect of diffuser type and density, we repeated lab-scale experiments in a 17,100 L pilot-scale test tank and carried out additional tests with tube and plate diffusers at different diffuser densities. The results show that despite the higher pressure drop, diffusers with dense slit density and smaller slits are to be recommended in order to improve efficiency of aeration systems in saline water.

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 frother addition mode on coal flotation in downflow flotation column

Using a downflow flotation column, we comparatively investigated the effects of two frother addition modes on clean coal production and bubble characteristics. These modes are traditional frother mode, which involves the direct addition of liquid Sec-Octyl alcohol (2-octanol) to slurry, and a novel addition mode, which injects 2-octanol vapor into the bubbles. Compared with the traditional mode, the vapor addition mode produced a higher concentrate yield, lower ash content, and higher combustible matter recovery. This result suggests that the vapor addition mode facilitates the larger product yield, producing a cleaner coal product. The consumption of 2-octanol under the liquid addition mode was reduced by 53.57% compared with that under the vapor mode to achieve 83% recovery of combustible matter. In the first 0.5 min and last 1.0 min of the 3 min flotation time, the vapor addition mode showed a slower flotation rate, whereas in the middle 1.5 min, the rate was faster. In addition, the vapor addition mode led to a smaller bubble size, critical coalescence concentration (CCC), and 23.21% reduction in 2-octanol consumption to achieve a constant bubble size. The higher capture probability of hydrophobic coal particles presented by the vapor addition mode is considered the fundamental cause for the enhanced clean coal yield and combustible matter recovery. With the increase in frother dosage, the particle–bubble collision probability was identified as the main factor determining the increase in the ash content of the concentrate at a concentration below the CCC. At a concentration above the CCC, the viscosity of bubble surfaces became the main factor.

Experimental Procedure for the Determination of the Critical Coalescence Concentration (CCC) of Simple Frothers

In this study, the critical coalescence concentrations (CCC) of selected commercial frother solutions, namely polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and as a reference, methyl isobutyl carbinol (MIBC), were determined using a bubble column based on light absorption. The results for all seven frothers showed that BTEG has the worst bubble inhibiting performance, and PPG 600 has the best bubble inhibiting performance. While critical coalescence concentration (CCC) was found as 3 ppm for PPG 600, it increased to 25 ppm for BTEG. In the case of MIBC, which was the reference point, the CCC value was found as 10 ppm, which was consistent with the literature. The surface tension isotherms of the frothers were determined and analyzed with one of the latest adsorption models. The results indicated that the polypropylene glycol frothers showed more surface activity compared to alcohol or other frothers investigated. This is due to the additional reorganization of the PPG molecules on the air/water interface, thus boosting its surface activity.

Correlations for Easy Calculation of the Critical Coalescence Concentration (CCC) of Simple Frothers

Can the critical coalescence concentration (CCC) of the flotation frothers be predictable? What is the relation between their molecular structure and their CCC values? A literature survey found specific correlations between the hydrophilic-lipophilic balances (HLB) and HLB/Mw (where Mw stands for the molecular mass) of homologue series of frothers and their CCC values, but the results are invalid when the molecule’s functional groups change. For this reason, 37 frothers with known values of CCC were analyzed. The CCC values of seven frothers were determined, and the rest were taken from the literature. The frothers were subdivided in homologue series with an increasing number of the carbon atoms with an account for the type and the location of the functional group, thus deriving three types of correlations lnCCC = f(HLB) applicable for: (i) alcohols; (ii) propylene glycols alkyl ethers and propylene glycols; (iii) ethylene glycols alkyl ethers. The average accuracy of these correlations between CCC and HLB is 93%.

Bubble size distribution in aerated stirred tanks: Quantifying the effect of impeller-stator design

Bubble size is an important variable in aerated stirred tanks as it determines the surface area available for reactions. In the bubble break-up process, impellers play a key role. Despite this importance, research into the effect of impeller design on bubble size is scarce. In this work we study the effect of two impellers, with and without a stator, as well as the effect of airflow rate, impeller speed and surfactant concentration on bubble size.Results show that there is a critical impeller speed above which bubble size is not further decreased, regardless of the airflow. Operating at this critical speed results in the smallest bubble size possible without additional turbulence. The reduction in bubble size caused by a stator was quantified for the first time and, interestingly, it was found that the stator also reduced the critical coalescence concentration. The implications of these findings for the design, evaluation and optimisation of impellers are discussed.

Bubble Size Distribution Characteristics of a Jet-Stirring Coupling Flotation Device

In this study, a new jet-stirring coupling flotation device that incorporates the advantages of three conventional flotation machines (specifically, Jameson cell, mechanical flotation cell, flotation column) was designed based on jet suction. The suction capacity of a double cosine self-aspirated nozzle utilized by the device was analyzed under different feeding pressures, and the effects of frother concentration, feeding pressure, suction capacity, and height of sampling location on the bubble size distribution (BSD) were investigated using a high-speed video system. It was found that a large amount of air was sucked into the flotation cell by the self-aspirated nozzle arranged in a non-submerged manner, which met the requirements of flotation in terms of the suction amount of air. The suction capacity showed a positive linear correlation with negative pressure inside the nozzle. When the Methyl isobutyl carbinol (MIBC) concentration reached the critical coalescence concentration (CCC), the bubble size stabilized at approximately 0.31 mm, which was smaller than the bubble size produced by the conventional flotation machine. This indicated that bubbles suitable for flotation were generated. D32 linearly decreased with increasing of feeding pressures and conversely increased with increasing suction capacities and sampling location heights, independent of the frother concentration.

Air Dispersion and Bubble Characteristics in a Downflow Flotation Column

ABSTRACTBubble Sauter mean diameter and aeration rate of a gas-liquid system in a laboratory downflow flotation column were explored. Both critical coalescence concentration and Sauter mean diameter decreased with increasing superficial liquid velocity, and also the Sauter mean diameter was found to obviously increase with the increase in the sampling height under low dodecylamine concentration. The aeration rate increased as the dodecylamine concentration increased at a constant valve opening degree and also linearly increased as superficial air velocity increased at a constant superficial liquid velocity of 11 cm/s. Compared to the superficial air velocity, the dodecylamine concentration was found to present a larger effect on the Sauter mean diameter but a smaller one on the aeration rate within the studied ranges of the dodecylamine concentration and superficial air velocity.

Frother critical coalescence concentration and dose in flotation of copper-bearing carbonaceous shale

The paper presents the yield of carbon-and-cooper-bearing shale from the Legnica and Glogow Copper Basin flotation also called Kupferschiefer in the presence of ethylene, diethylene and trithylene glycol butyl ethers (C4E1, C4E2, C4E3) frothers characterized by frother normalized concentration that is ratio of the frother concentration, and its critical coalescence concentration expressed in different units. It was found that the oucome of flotation is identical provided that the frother concentration is expressed in milimoles per Mg.

Treatment of produced water by induced air flotation: effect of both TWEEN 80 and ethanol concentrations on the recovery of PAHs

Abstract The present study investigates the application of induced air flotation (IAF) technique on PAHs (PAHs) removal performance from a real oilfield produced water of a separator cell. The quantification of total PAHs (PAHtot) was done using ultraviolet-visible spectrometry (UV-Vis) according to the naphthalene calibration curve. The UV-Vis spectra of naphthalene dissolved in a mixture of the binary solvent (water-ethanol) and the Tween 80 showed stability in the molecular orbital of C10H8. The use of small concentration of Tween 80 was revealed to be discrete in the quantification of PAHtot. The flotation process was improved at the critical micelle concentration of Tween 80 (CMC) of 2 % and the critical coalescence concentration of ethanol (CCC) of 0.5 mL/L for the PAHtot recovery of 49.76 % and the PAHtot content in the pulp of 50.24 %. At these concentrations, half of PAHtot was removed from produced water PW. Above the CMC and the CCC, the PAHtot recovery decreased and the PAHtot content in the pulp increased. It was found that there is a collector concentration at which the amount of water carrying from the pulp to the concentrate was increased and in parallel, the PAHtot recovery increased and the PAHtot content in the pulp decreased. Both of the CMC and the CCC have promoted the decrease on the conditioning time from 30 to 10 min and the flotation time from 20 to 6 min. Since the impeller speed and air flow rate were constant, the flotation of PAHs was limited. The flotation kinetics of PAHtot was described by the Higuchi model.

Critical Coalescence Concentration (CCC) for Surfactants in Aqueous Solutions

This paper presents results of tests performed to determine the minimum concentration of a surfactant used at which the probability of occurrence of coalescence of air bubbles during flotation is low. Tests of the coalescence phenomenon were carried out using selected flotation frothing agents such as poly(ethylene glycol) butyl ethers, which are the ingredients of industrial flotation frothers known under the brand name of CORFLOT. Studies were carried out for three successive butyl ethers in the homologous series: ethylene glycol butyl ether (C4E1), diethylene glycol butyl ether (C4E2), triethylene glycol butyl ether (C4E3). Critical coalescence concentration (CCC) surfactant values were determined using the linear regression method. The investigation proved the existence of a clear relationship between the number of ethylene glycol groups in the ether molecule CnH2n+2(OC2O5)nOH and the value of the CCC. The results obtained show a correlation between the CCC values and the molecular weights (MW) of the tested frothers. This article shows the relationship between CCC value and hydrophilic–lipophilic balance (HLB)/MW for the family of polyglycol ethers. Results show the correlation between the critical coalescence concentration and the value of HLB index, being the measure of hydrophilic–lipophilic balance of surfactants (such as flotation frothers), expressed by the weight ratio of hydrophilic portion of the surfactant molecule and its molecular weight. Histograms of air bubbles created a distribution curve similar to the Gauss distribution pattern. The average diameter of air bubbles tends to decrease along with increasing concentration of the tested surfactants. Two characteristic zones that may be distinguished on the graphs show the relationship between Sauter mean diameter and frother concentration. The tests carried out demonstrate that the critical coalescence concentration may be used to characterize the flotation process, as, knowing the CCC values of the frothers used, we are able to control the consumption of foaming agents during mineral processing.