Critical Coalescence Concentration Research Articles

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.

A study of bubble size evolution in Jameson flotation cell

The Sauter mean diameter (d32) of bubbles was characterized for a gas–liquid system in a laboratory Jameson-type flotation cell with focus on the size variation in the uprising path of the bubbles in the riser of the flotation cell. Methyl isobutyl carbinol (MIBC) was used as frother for bubble stability. The effect of MIBC concentration, sampling height in the riser, gas flow rate (Jg) and liquid flow rate (Jl) in the downcomer on d32 was investigated. The d32 significantly decreased with increasing MIBC concentration until the Critical Coalescence Concentration (CCC), above which the d32 was almost constant at 0.645mm. CCC95, CCC90 and CCC85 were calculated to be 0.059, 0.046 and 0.038mmol/L, respectively for a Jg of 1.32cm/s and Jl of 11cm/s. Four frother concentrations covering these three values were selected for detailed studies. The size variation of bubbles was related to the Reynolds number (Re) in the downcomer, where the Re was influenced by Jl and Jg. Bubble size increased with the sampling height in the riser at MIBC concentrations below CCC95. This bubble size decreased with the Re and, for all the MIBC concentrations used in this investigation, it reached a critical value, even at MIBC concentrations below the CCC85.

Frother structure-property relationship: Effect of polyethylene glycols on bubble rise velocity

This paper is part of our study of the frother structure-property relationship using bubble rise velocity as the property. Single bubble rise velocity profiles were determined for surfactants of the polyethylene glycol (PEG) family in a 350-cm column, and the concentration to reach minimum velocity (CMV) measured at 300 cm is determined. The lower the CMV indicates a structure more effective in slowing bubble rise. The CMV is shown to decrease as both alkyl chain length (n, number of carbons) and number of ethylene oxide groups (l) increases. Linear correlations log CMV vs. n and l were observed; and taking literature data for critical coalescence concentration (CCC), a linear log CMV vs. log CCC correlation was found. Mechanisms controlling bubble rise velocity based on structure effects on surface tension gradients and surface viscosity are discussed. A comparison with previous findings on polypropylene glycols is included.

Concentration at the Minimum Bubble Velocity (CMV) for Various Types of Flotation Frothers

This paper presents the determination of a concentration at the minimum bubble velocity (CMV) for different types of frothers, such as straight and branched alkyl chain aliphatic alcohols, 1,ω-diols, poly(propylene glycol) and poly(ethylene glycol) alkyl ethers, n-alkyltrimethylammonium bromides, commercial frothers and others. The values of terminal rise bubble velocity were reviewed from the experimental data published in the literature for two different types of columns, i.e., a short PAS (used in Polish Academy of Sciences) of height (35 cm) and a long McGill of height (350 cm). The obtained empirical equation is universal and allows one to rapidly and accurately determine the CMV for all surfactants. The proposed empirical model can also be used to predict the terminal bubble velocity–frother concentration curve by knowing the maximum and minimum terminal velocities, as well as the values of CMV. Assessment and usefulness of frother characterization parameters (i.e., concentration at the minimum bubble velocity (CMV), dynamic frothability index (DFI) and critical coalescence concentration (CCC)) were shown in the flotation of coal.

A high-order moment-conserving method of classes (HMMC) based population balance model for mechanical flotation cells

In this paper, a high-order moment-conserving method of classes (HMMC) model is developed to predict bubble size distribution, number mean and Sauter mean diameters (SMD) in mechanical flotation cells. The population balance model (PBM) uses vessel averaged turbulence kinetic energy dissipation rate and gas hold-up as model inputs along with initial bubble size distribution. Experimental measurements are made in a 0.8m3 pilot scale XCELLTM mechanical flotation cell at different aeration rates and impeller tip speeds. All the experimental measurements using MIBC frother are performed at frother dosage value over critical coalescence concentration (CCC), therefore, coalescence process is not considered in the PBM. Nonlinear least squares function (lsqnonlin) and constrained nonlinear multivariable minimization function (fmincon) available in the MATLAB optimization toolbox are used. Three breakage models, namely, Coulaloglou and Tavlarides (1977), Chen et al. (1998), and Alopaeus et al. (2002), each requiring estimation of adjustable parameters from the experimental data are selected. Also, 95% confidence intervals for estimated breakage parameters are calculated using a bootstrap based re-sampling technique. The developed model is capable of providing acceptable predictions of bubble size distribution, number mean diameter, and SMD for a reasonably wide range of operating conditions and has the potential to be developed further for three phase air-water-solid systems.

Foamability of fatty acid solutions and surfactant transfer between foam and solution phases

The foaming properties of aqueous solutions of fatty acids with different hydrocarbon chain lengths - hexanoate, laurate, and oleate - were assessed through measurements of foam volume and growth rate under continuous aeration. Simultaneous measurements of the partition of each surfactant between the bulk solution and foam phases were also carried out. Although bubble size measurements in bulk solution pointed towards quite similar gas dispersing abilities of the tested surfactants, their foamabilities under the same conditions were remarkably enhanced with increasing chain length of the hydrocarbon tail. Shorter chain surfactants - hexanoate and laurate - generated wet foams and the accumulation of these surfactants in the foam phase was very low, indicative of a low adsorption density of the reagents at the gas-liquid interface. In contrast, sodium oleate produced stable dry foams, and the amount of oleate transferred to the foam was much higher. The formation of these different types of foam was attributed to the higher adsorption of oleate at the gas-liquid interface compared to the lower adsorption of hexanoate or laurate, and to different mechanisms of foam stabilization. Regardless of the interfacial mechanism of the foaming action of the tested surfactants, it was generally found that strong foaming was possible only from surfactant solutions whose bulk concentration was higher than the critical coalescence concentration of a given surfactant. It was concluded that bubbles entering the foam phase from the bulk solution phase must already be stable against coalescence to induce foam formation and impart stability to the entire foam column. Foaming was observed only in true solutions of the tested surfactants, while precipitation of colloidal acid species completely depressed foam formation.

Flotation of copper-bearing carbonaceous shale in the presence of amine type frothers

<p>Hexylamine, chloro-derivative of propylamine, and ammonium chloride were used for flotation of Permian carbonaceous copper bearing shale from the Legnica-Glogow Copper Basin region in SW Poland. It was confirmed that naturally hydrophobic shale, known as Kupferschiefer, can be made floatable by application of short chain amines as frothers. It was also established that the short chain amine chloro-derivatives as well as salmiac, the first member of the amine family, can be used as a frother for flotation of the investigated shale sample. It results from the paper that the investigated amine frothers work similarly if the comparison of the flotation results is made using their concentration expressed in relative form taking into account the critical coalescence concentration of the frother.</p>

Indirect measurement of frother concentration based on l-CCC curves

The local critical coalescence concentration l-CCC presents a relationship between frother concentration and the gas flow rate Qg′ at which coalescence starts to occur at a capillary tube. Such a relationship is used in this work to determine frother concentration. The solution with unknown frother concentration is tested to determine Qg′ and the concentration is determined from a reference l-CCC curve that has been previously determined for the frother to be tested. The technique is simple, and easy to implement. The determination of the reference l-CCC curve takes 1h or less, after which the measurements are very quick, taking no more than 5min per sample. The technique was validated against the total organic carbon (TOC) method for a series of samples of unknown frother concentration, for three different frothers, with a correlation coefficient R2 equal to 0.997. The measurements are not affected by the presence of xanthate in the system, when using MIBC as a frother, which suggests the possibility of using it, combined with TOC analysis to determine both frother and xanthate concentration by mass balancing.

Impact of inorganic salts on behaviour of air bubbles in aqueous solutions

This paper comprises an analysis of solutions of such salts as: sodium chloride NaCl, potassium chloride KCl, sodium sulphate Na2 SO4 , ammonium chloride NH4 Cl, and hexylamine hydrochloride C6 H15 N·HCl. The objective of the paper was to determine the Critical Coalescence Concentration (CCC) of four inorganic and one organic salts. The obtained CCC values were similar to those already existing in literature. Also, in this paper the CCC values of investigated inorganic salts were compared in terms of their ionic strength. The results showed that, except KCl, there was a relationship between CCC and ionic strength.

Effect of foamability index of short chain alkyl amines on flotation of quartz

Amines can be used for flotation of various minerals, especially quartz. The flotation efficiency of quartz depends on the amine type and dose. It was proved that the shorter alkyl amine, higher amine concentration has to be used to recover quartz at the same level. In flotation amines play a role of both collectors and frothers. The ability of a amine to collect particles can be expressed in the form of contact angle, while the foaming properties by different parameters including dynamic foamability index (DFI) and critical coalescence concentration (CCC). Determination of DFI and CCC requires advanced techniques and methods. Therefore, in this paper a rapid and facile method for determination of foaming properties of amines and also other surfactants was used. It was based on measuring the initial foam and froth heights in a conventional flotation machine at different concentrations of surfactants. The foam height-concentration curve was described by utilizing an empirical equation which was based on one-adjustable parameter called the foamability index (FI ). In this work the foamability index was determined for butylamine (ButNH2 ), hexylamine (HexNH2 ) and octylamine (OctNH2 ) as examples of short chain alkyl amines. The determined foamability indices were 92, 12 and 4 mg/dm3 for ButNH2 , HexNH2 and OctNH2 , respectively. It was shown that when the flotation results of quartz were presented in the form of recovery versus normalized amine concentration in relation to the foamability index (c/FI ), all the experimental data points converged to one curve. It indicates that amines act similarly but at different concentrations expressed as FI . The foamability index seems to be a useful parameter for characterizing any flotation frother.

Effect of frothers and dodecylamine on bubble size and gas holdup in a downflow column

Bubble size and gas holdup were characterized in a two phase gas–water system in a laboratory downflow column. The effect of the cationic surfactant dodecyl amine (MW 185, HLB 10.7) and the frothers MIBC (MW 102, HLB 6.05) and polyglycol F507 (MW 425, HLB 8.63) on the bubble size and gas holdup were investigated. In addition, the effect of blends of MIBC-dodecyl amine (DDA) and F507-DDA on these parameters was assessed. The bubble Critical Coalescence Concentration (CCC) followed the order MIBC>DDA>F507. When blending the frothers with DDA at a concentration below its CCC, the frother CCC decreased and bubbles of finer size were obtained below and above the frother CCC. Static surface tension measurements of aqueous solutions with frothers and DDA as well as with frothers-DDA blends show coadsorption of DDA at the air/aqueous solution interface. The surface tension of aqueous solutions prepared with the blends decreased with the addition of DDA and varied linearly with the frother concentration within the concentration range studied. The gas holdup in the downflow column was determined by the bubble size and decreased with the bubble size. It is shown that frother-DDA blends gave the lowest gas holdup in the downflow column. This work is relevant for the reverse flotation of quartz from iron ores using amine collectors in cells with downflow systems.

Effect of ionic strength on bubble coalescence in inorganic salt and seawater solutions

Bubble size is of fundamental importance in the flotation process, as it provides the surface area for particle collection. Typically, weak surfactants (frothers) are added to process water to reduce bubble coalescence. Certain inorganic electrolytes, which occur naturally in some flotation process water, have been shown to mimic the role of frothers. The concentration at which bubble coalescence is inhibited, the critical coalescence concentration, was determined in a 5.5‐L mechanical flotation cell for a series of coalescence inhibiting inorganic salts. To mimic some industrial flotation process water, a synthetic sea salt solution was also tested. It was found that when the multicomponent sea salt solution was broken down into its constituent parts, the addition of the ionic strength of each ion correlated well with the overall ionic strength curve of all the salts tested. The critical coalescence ionic strength ranged from 0.22 to 0.35, with sea salt being 0.26. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2489–2496, 2015

Behaviour of bubble clusters in a turbulent flotation cell

The rate of capture of particles decreases as the particle size increases in froth flotation. It has been postulated that the upper size range of particles that can be recovered in conventional machines could be extended by the use of bubble clusters [1].This study is concerned with the behaviour of bubble clusters in turbulent flotation cell. The breakup and re-formation of clusters and the effect of bubble size and impeller speed on the behaviour of clusters have been investigated. The apparatus used was essentially a laboratory flotation cell, agitated by a Rushton turbine. The cell was modified to allow pre-formed clusters to rise out of a fluidized bed and into the path of the rotating impeller. The events were captured using a digital camera, and the images were analysed to give the sizes of the bubbles and clusters.In the first part of the investigation, a collector was used but no frother. Under these conditions, the bubble diameter was effectively controlled by the collector concentration, and it varied considerably. It was found that the sizes of clusters decrease with increasing shear rate at low impeller speeds, and at higher speeds the clusters are broken up into bubbles and particles.In the second part, frother was used at a concentration above the critical coalescence concentration, to control the bubble size, which remained essentially constant at this concentration. The bubbles were too small to be broken by the action of the impeller, so they always remained at the same size. In this case it was found that when the impeller speed was increased, two stages of formation were observed, the fragmentation and equilibrium stages. In the fragmentation stage, at low impeller speeds, the clusters were loose and filamentous, and as the energy input increases, they rupture and re-form. In the second stage, above a critical impeller speed, dense clusters formed whose size was relatively insensitive to the energy input.

Frother function–structure relationship: Dependence of CCC95 on HLB and the H-ratio

Although the number and diversity of commercial frothers has steadily increased to meet flotation industry demands, frother selection is still mainly empirical. As part of a general structure–property study, the paper presents a correlation between the critical coalescence concentration (CCC95) and H-ratio for surfactants used as flotation frothers. The CCC95 were determined in 0.8m3 mechanical flotation cell. The H-ratio was a substitution of hydrophile-lipophile balance (HLB) and determined through high resolution proton nuclear magnetic resonance (1H NMR) spectrometry. A large data set, consisting of 45 surfactants from four frother families, was used to develop the correlation. It is shown that the H-ratio can substitute for HLB. The potential of NMR both to identify the frother family and to derive the H-ratio in predicting CCC95 for commercial frothers is discussed.

Comparative study of the main flotation frothers using a new HYDROMESS adapted technique

Stability of bubble size in the pulp zone and froth control is an important parameter for a successful flotation process. The present study compares the action of the main frothers in terms of: mean bubble size in the pulp zone, froth stability, surface-tension-lowering ability and reagent participation in flotation of a naturally hydrophobic mineral. Bubble size was determined using a new technique adapted from HYDROMESS, a device designed to measure drop size. The remaining indicators were obtained by determining surface tension and conducting flotation tests with the addition of hydrophobic (graphite) and hydrophilic (calcite) particles. The results indicate that methyl isobutyl carbinol (MIBC) is the most efficient frother in controlling coalescence, with critical coalescence concentration (CCC) reached at 20 ppm. Moreover, this frother has greater potential for selective action, since it increased calcite entrainment by only 2.3% at a concentration of 30 ppm. In flotation tests with a sample of graphite, MIBC produced higher recoveries.

Critical coalescence concentration of inorganic salt solutions

Critical coalescence concentration (CCC) was determined in a laboratory-scale mechanical flotation cell for a series of coalescence inhibiting inorganic salts (KCl, NaCl, Na2SO4, CaCl2 and MgSO4) compared to two commercial frothers (methyl isobutyl carbinol, Dowfroth 250C). The salt CCC values ranged from 0.07M (MgSO4) to 0.31M (KCl and NaCl) and correlated with ionic strength. The CCC values are compared to transition concentrations in the literature. The effect of salts on gas dispersion in flotation systems is discussed.

Validity of critical coalescence concentration in dynamic conditions

The aim of the study was to confirm that the concept of the critical coalescence concentration (Cho and Laskowski, 2002) is only applicable to static conditions.A new experimental setup was developed. The experimental idea was to sample the same batch of bubbles at their formation point and later, during the bubble rise in static and dynamic conditions. The difference in the measured bubble size in the two sampling areas gives indication on the effect of frothers on bubble coalescence and breakup that takes place after the bubble creation due to the dynamic conditions.Three commercial frothers, DF200, NF240 and DF250, were tested in the experiments.In static conditions, the size of the forming and rising bubbles became equal at the frother concentration equal to the critical coalescence concentration (CCC) observed previously in mechanical flotation cell. On the other hand, in dynamic conditions, the size of rising bubbles was significantly larger than the size of freshly formed bubbles not only below the CCC as expected based on the literature. This finding confirms the hypothesis that the CCC is only applicable in static conditions, or in conditions where hydrodynamic forces do not contribute to bubble coalescence or breakup. The results showed that the frothers have a major effect on bubble size already at the early stage of bubble formation.

CRITICAL COALESCENCE CONCETRATION (CCC) AS A PARAMETER FOR EVALUATION OF SELECTED QUATERNARY AMMONIUM COMPOUNDS

The objective of this paper was to determine the Critical Coalescence Concentration (CCC) of surfactants such as N(dodecyloxycarboxymethyl) N,N,N-(trimethylammonium) bromide (DMGM12), N-[2-(dodecyoxycarboxy)ethyl] N,N,N-(trimethylammonium) bromide (DMALM-12) and N-[3(dodecanoyloxycarboxy)prophyl] N,N,N-(trimethylammonium) bromide (DMPM-11). The surfactants used represent quaternary ammonium compounds containing a hydrophobic moiety with an ester group (commonly known as “esterquats”). The CCC value was determined by analysis of the relationship between concentration of surfactant and average air bubble diameter. The values of the critical coalescence concentration (CCC) were estimated using a graphical method.

Determination of Critical Coalescence Concentration and Bubble Size for Surfactants Used as Flotation Frothers

The paper presents a correlation between the critical coalescence concentration and hydrophilic–lipophilic balance/molecular weight ratio for surfactants used as flotation frothers. The correlation...