Dynamic Foam Stability Research Articles

Synergistic Effect of Frequently Found Ions in the Flotation of Pb-Zn Sulfide Ores on Air/Water Interface

The aqueous ions influence the properties of air bubbles and, therefore, the recovery of flotation. This study aims to reveal the synergistic effect of frequently found ions in the flotation of Pb-Zn sulfide ores. In this context, dynamic surface tension measurements, bubble coalescence time, Sauter mean diameter (SMD), bubble size distribution (BSD), and dynamic foam stability (DFS) measurements were carried out using artificial process waters (APWs). APW with the minimum ion concentration is expressed as “APW1” with the ionic strength (I) of 0.03 mol/dm3. The concentration of the ions in APW1 was increased by 3, 5, and 10 times, and thus APW3 (I = 0.08 mol/dm3), APW5 (I = 0.13 mol/dm3), and APW10 (I = 0.26 mol/dm3) were prepared, respectively. The results of this study indicated that the surface tension increased slightly in the presence of APW related to the ion concentration. Potassium ethyl xanthate (KEX) at high concentrations was effective in the reduction of surface tension. As the APW concentration increased, finer bubbles were obtained with a narrower size range. The stability of the foam increased with butyl glycol (BG) and APW concentration. There was no need to use a frother (BG) for the flotation experiments in the presence of APW1 or APWs with higher ionic strength.

Study on the Strengthening Mechanism of a MIBC-PEG Mixed Surfactant on Foam Stability.

In the flotation process, the frother, which is typically a surfactant, can be added to the pulp to reduce the surface tension and create stable foam. Currently, the nonionic mixed surfactant is widely employed as the frother for fine coal flotation. In this study, we focused on examining the foam properties of a mixed surfactant comprising short-chain methyl isobutyl carbinol (MIBC) and long-chain polyethylene glycol-1000 (PEG). Analytical techniques such as surface tension measurement, dynamic foam stability measurement, bubble morphology observation, and foam film drainage measurement were used to investigate the foam properties in single and mixed surfactant solution from a macroscopic scale to a microscopic scale. The surface tension results indicated that PEG exhibited higher surface activity than MIBC, and the addition of PEG to MIBC resulted in a significant reduction in solution surface tension. The dynamic foam stability analysis revealed that the incorporation of a small amount of PEG into MIBC solution notably improved foam stability. Furthermore, the addition of PEG to the MIBC solution led to a shift in the bubble size distribution curve from a "double peak" to a "single peak" shape. This shift indicated a substantial reduction in bubble size, indicating an enhanced inhibition of bubble coalescence. Additionally, the liquid film drainage rate was significantly slowed down, and the stability of the liquid film was improved upon the addition of PEG to MIBC. This improvement can be attributed to the synergistic effect of MIBC and PEG molecules adsorbed at the gas-liquid interface. The synergistic effect of mixed MIBC-PEG was due to the additional surface tension gradient created by the difference in surface activity between PEG and MIBC. This surface tension gradient enhances the Marangoni flow of surfactant molecules, thereby improving the self-healing ability of the liquid film and increasing its stability.

Selective Separation of Fluorite from Calcite Using Saponified Tridecanoic Acid as a Novel Collector

ABSTRACT Fluorite, as a vital calcium-containing mineral, usually coexists with calcite. When using the traditional collector sodium oleate (NaOL), froth flotation could not separate fluorite and calcite well on account of their similar surface properties. Meanwhile, a large amount of sodium silicate (SS) needs to be added to depress calcite, resulting in difficulties in tailings settlement and wastewater treatment. Therefore, a nontoxic and inexpensive surfactant saponified tricarboxylic acid (TA) was developed as a new collector. The flotation test results showed that TA had a higher selectivity for fluorite than NaOL, leading to the selective separation of both minerals. Zeta potential measurements indicated that TA was negatively charged and was strongly adsorbed on fluorite due to electrostatic interactions at pH 9.0. FTIR, XPS, DFT, and crystal chemistry calculations revealed TA had a stronger chemical interaction with fluorite due to its higher surface Ca activity and density, forming a TA-Ca complex through the bidentate coordination. In contrast, the interaction of TA with calcite could be ignored. In addition, the results of the surface tension and dynamic foam stability tests revealed that TA possessed the excellent foam performance. Therefore, these properties give TA excessive potential for industrial application and environmental protection in fluorite flotation.

Improvement of dynamic foam stability with low-frequency acoustic sound

Exposing the froth phase of a flotation system to low-frequency acoustic sound was reported to improve the process efficiency, which was thought to be due to the improvement in the froth stability. However, no direct evidence of the stabilization effect of sound on froths or foams is available to date. The present work aims to resolve this issue by experimentally studying the effect of low-frequency acoustic sound on the stability of a foam, the two-phase counterpart of flotation froth, across a wide range of experimental conditions. Three different setups consisting of a flotation column or a bottom-driven mechanical flotation cell, with the foam being exposed to sound from above or below, were tested. The equilibrium height of the foam with a given flow rate of air supply was measured at steady state using the Bikerman’s method. The equilibrium foam height was found to increase within certain ranges of sound frequencies and amplitudes, and at various surfactant concentrations (3–50 ppm) and superficial gas velocities (0.3–2.0 cm·s−1). An increase in sound amplitude or superficial gas velocities was also found to broaden the range of sound frequency that led to the stabilization effect. These findings were largely common for the three different setups tested, suggesting that this is a versatile method for improving the stability of foams. A strong correlation was also found between the stabilization of foam demonstrated in the present work and the stabilization of froth reported in a previous study, implying that the stabilization mechanisms could be similar.

Considering Specific Ion Effects on Froth Stability in Sulfidic Cu-Ni-PGM Ore Flotation

The mining and mineral processing of Cu-Ni-PGM sulfide ores in South Africa occurs in semi-arid regions. The scarcity of water resources in these regions has become one of the biggest challenges faced by mineral concentrators. As a result, concentrators are forced to find ways through which they can manage and control their water usage. The recycling and re-use of process water in mineral concentration plants has therefore become a common practice. This practice is beneficial in that it reduces reliance on municipal water and harnesses compliance to stringent environmental regulations on freshwater usage. This approach also offers a better response to the Sustainable Development Goals (SDGs) for the mining industry, as water and its preservation form part of the SDGs. This practice could, however, be somewhat concerning to a process operator because recirculated water often has higher concentrations of ions compared to fresh or potable water. This is because an unintended change in the process water quality may affect critical aspects of flotation such as the stability of the froth. This issue has led to the need for both the mining industry and researchers in the field to find the ions in process water that have the greatest impact on froth stability. Thus, the authors of this study investigated the effects of various ions common in the process water of a typical Cu-Ni-PGM ore on froth stability using a 3 L bench scale flotation cell. Solids and water recoveries were used as proxies for froth stability. These were further complemented by bubble size, water recoveries, foam height, and dynamic foam stability from two-phase flotation systems. A two-phase foam study resulted in observations that supported findings from a three-phase study. Generally, single salt solutions containing Ca2+ and Mg2+ ions resulted in higher water recoveries both in the two-phase foam and three-phase froth studies, increases in foam heights and dynamic foam stability, and a decrease in bubble size compared to the solutions that contained Na+. SO42− also resulted in increased foam stability compared to Cl− and NO3−. These results showed that the divalent inorganic electrolytes—Ca2+, Mg2+, and SO42−—were more froth- and foam-stabilizing than the monovalent inorganic electrolytes—Cl−, NO3−, and Na+. This finding was in agreement with previous research. The findings of this study are deemed crucial in the development of a process water management protocol in sulfidic Cu-Ni-PGM ore concentrators. However, more comparative three-phase froth stability tests are needed as subjects of future investigative work to further ascertain specific ion effects on froth stability in sulfide ores.

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.

Influence of critical parameters on nanoparticles-surfactant stabilized CO2 foam stability at sub-critical and supercritical conditions

The stability of CO2-foam stabilized via the synergy of nanoparticles and surfactants at downhole conditions is strongly affected by different process parameters such as temperature, CO2 state, nanoparticles concentration, as well as resident brine and oil in the reservoir. Influence of critical parameters on static and dynamic stability of nanoparticles-surfactant stabilized CO2-foam at sub-critical and super-critical conditions was investigated in this study. Firstly, extensive static and dynamic foam stability experiments were conducted at 80 °C and presence of 30 vol% hexadecane oil using formulation turbiscan, to screen different surfactants and nanoparticles. The best performing nanoparticles and surfactant were then selected at the screening stage for further foam stability tests to compare the performance of CO2 foam at sub-critical and super-critical conditions. The foam stabilized by SiO2 and sodium dodecyl sulfate (SDS) demonstrated consistent static and dynamic stability, with least spreading coefficient (-5.28 mN/m) and favourable Lamellae number (0.71). Increasing nanoparticles concentration increased the stability of sub-critical CO2 foam whereas an optimum nanoparticles concentration for maximum stability of the supercritical CO2 foam was obtained as 0.5 wt% SiO2. The static stability of sub-critical and supercritical CO2 foam increased with increased sodium chloride (NaCl) concentrations until 2 wt%. However, the super-critical CO2 foam demonstrated increasing pressure drop and lowest reduction in mobility with increasing NaCl concentration until 10 wt%. Highly durable foams were generated when oil with high viscosity, high density and high molecular weight oil was added into the foaming dispersions. Mechanistic investigation of foam stabilization revealed that thickness of pseudo-emulsion films, as well as particles adsorption and orientation at gas–liquid and liquid–liquid interface, are key controlling parameters of foam static and dynamic stability in presence of oil, brine and at high temperature.

Foam stability of flotation frothers under dynamic and static conditions

The objective of this paper is to provide a detailed understanding of the relationship between frother type and foam stability under dynamic and static conditions. The dynamic foam stability for eighteen non-ionic frothers from different frother families was assessed using foaminess, which quantified the ratio of foam height to the gas superficial velocity. For all tested frothers, the foaminess increased as the concentration was increased. The static foam stability was assessed by measuring the half-life and the decay rate of the foams at different superficial gas velocities and concentrations. The foam stability results showed that for aliphatic alcohols, the greater the number of hydrocarbon groups, the more stable the foam was under dynamic and static conditions. For polypropylene glycols, increasing the number of propylene oxide groups increased foaminess and half-life, however, a further increase in the number of propylene oxide groups (m > 7) led to a decrease in foaminess. There was not a clear relationship between the number of propylene oxide groups and the maximum foam half-life. Interestingly, the foam decay rate coefficient increased by increasing the number of propylene oxide groups. For propylene glycol methyl ethers, foaminess, foam half-life and decay rate coefficient increased with an increase in the number of propylene oxide groups.

Stabilization mechanism of CO2 foam reinforced by regenerated cellulose

CO2 foam was widely applied to enhance sweep efficiency through controlling gas breakthrough and channeling during the process of CO2 flooding. However, the poor stability of conventional foam system under the harsh reservoir conditions restricted the enhanced oil recovery (EOR) performance of CO2 foam. Therefore, the CO2 foam reinforced by anionic-nonionic surfactant SS163 and the regenerated cellulose (RC) was developed; also its stability was compared with other foams (e.g. stabilized with SiO2, Al2O3, HPAM and stabilizer-free foam). The static and dynamic foam stability were evaluated by the modified Ross-Miles method, Warning Blender method, oscillation-shear-oscillation rheology. Furthermore, the foam aging rules were investigated via the multiple light scattering method and double-layer glass model. Upon that, the stabilization mechanism by RC was proposed and elucidated by the viscosity, storage and loss modulus, morphological inspection, SEM images and their correlation with foam stability. The results demonstrated that 1% SS163 + 1% RC CO2 foam has the highest foam stability and regeneration capacity compared with other foams. The dynamic variations in the film thickness and diameter of the foam characterized four stages of RC reinforced CO2 foam. The prolonged liquid drainage was attributed to the following four RC stabilization mechanisms: increased viscosity, the stabilization mechanism of RC aggregates, the liquid film ‘skeleton’ formed by RC, and the liquid storage effect of RC. In this work, we introduce the regenerated cellulose in the application of EOR and present the unique stabilization mechanism of RC on CO2 foam. The interface stabilizing capacity, viscoelasticity, thickened behavior and sustainability of regenerated cellulose highlights the application potential in EOR.

Structure–Behavior–Property Relationship Study of Surfactants as Foam Stabilizers Explored by Experimental and Molecular Simulation Approaches

A multiscale stability study of foams stabilized by sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and sodium polyoxyethylene alkylether sulfate (AES) was conducted, to investigate the relationship of surfactant molecular behavior and interfacial monolayer configuration of foam film to the foam film properties. Molecular dynamic (MD) simulations using a full-atom model was utilized to explore the microscopic features of the air/liquid interface layer. Several parameters such as the distribution of surfactant head groups and the order degree of surfactant hydrophobic tails were used to describe the molecular adsorption behavior. The effect of molecular structure on the nature of the foam film and the impact on the dynamic stability of wet foam is discussed. In the experimental evaluation, the SDBS foam films manifest strong stiffness and low viscoelasticity as shown by the interfacial shear rheology determination as well as texture analyzer (TA) measurement results, which agree very well with the array behavior of SDBS molecules at the air/water interface as described by the simulation results and is identified to be the reason for the poor dynamic stability. Comparing the molecular structure of SDS, SDBS, and AES, the special contributions of the linking groups such as the O atom, the phenyl group, and the EO (oxyethyl) chain to the interfacial array behavior of surfactants were characterized. It is concluded that microhardness of the foam film enhanced by rigid linking groups favors static foam stability but decreases the dynamic foam stability, while viscoelasticity of the foam film enhanced by soft linking groups increases the dynamic foam stability.

Effect of humidity on dynamic foam stability

Abstract It is experimentally shown that the stability of non-overflowing pneumatic foams, such as those used in the Bikerman foam stability test, is strongly dependent upon the gradient of humidity within the freeboard of the column. Growing foams can be prevented from exhibiting collapse, even at surfactant concentrations significantly lower than the critical micelle concentration, by saturating the air above the foam surface thereby preventing liquid evaporation. These observations have important implications for the performance of flotation devices, as well as instruments designed to measure the stability of aqueous foams. Meteorological data for two mining sites in Australia throughout a single year shows the variability of humidity, and therefore stability, of flotation froths.

Comparing the static and dynamic foam properties of a fluorinated and an alpha olefin sulfonate surfactant

To improve the understanding of the influence of oil type and of oil saturation on foam stability and foam generation, core flooding experiments have been performed using three different North Sea oils. The experiments were performed using two surfactants – an alpha olefin sulfonate (AOS) and a fluorinated surfactant (FS-500) – both with and without oil. The dynamic foam stability has been compared with results from static foam tests. Foam was generated by both surfactants in all core flooding experiments both with and without oil. The experiments showed that the surfactants generated foam with similar strengths and stability in both dynamic foam experiments and static foam tests without oil. In the core flooding experiments with residual oil saturation, the AOS surfactant generated weaker foam than that of the FS-500 surfactant. Foam generation with the FS-500 surfactant in core flood experiments seemed independent of the presence of residual oil saturation with respect to foam strength. Foam propagation was significantly delayed, however, in the presence of oil. AOS generated foam with differing foam strengths for the different crude oils in the core flooding experiments. Interestingly, the AOS surfactant showed more rapid foam propagation with, than without residual oil present in the core. The correlation between the static and dynamic foam experiments was poor for the AOS surfactant.

Effect of esterically bonded agents on the monolayer structure and foamability of nano-silica

The use of nanoparticles as foam stabilisers has gained increasing attention in recent years, for applications in a number of process industries, such as food colloids, metal and ceramics production and mineral flotation. Here we consider the foaming behaviour of 270 nm silica particle suspensions, hydrophobised to varying extents via esterification with butanol, octanol and dodecanol. The foaming behaviour was related to the compressed two-dimensional monolayer behaviour from Langmuir–Blodgett trough and SEM studies. The octanol esterified species performed best as both dynamic and static foaming agents, indicating particles of moderate hydrophobicity may work best as stabilisers. Dynamic foam stability results were linked to the balancing of interfilm drainage and steric stabilisation mechanisms. No firm conclusions could be drawn on the total effect of hydrophobicity on static foams, as particles esterified in dodecanol shear-flocculated under the stresses of foam production. Foam stability correlated well to compressed monolayer behaviour, with two-dimensional stability being influenced by the competing effects of a more disordered network structure and higher interfacial strength, as particle hydrophobicity was increased. It is noted that even with the best performing particles, less than 10% of a given dispersion interacted under shaking to form bulk foam.

Bubble coalescence and its effect on dynamic foam stability

AbstractThe size of bubbles generated using a single‐hole sparger, a multi‐hole sparger and a flotation cell were measured. While the size of bubbles generated from the single‐hole sparger does not depend on frother concentration, the bubble size strongly depends on frother concentration when the multi‐hole sparges, or flotation cell, are utilized. The bubbles size ceases to depend on frother at the concentrations exceeding the value characteristic for each frother and referred to as the critical coalescence (CCC). All the bubble size vs. frother concentration curves converge on a single curve. Aqueous solutions of the frothers that are characterized by low CCC values from foams quite stable under dynamic conditions. Since bubble coalescence can be inhibited by frother concentrations exceeding the CCC, sparing systems can be studied and compared only at frother concentrations that exceed CCC.

A relation between dynamic foam stability and surface elasticity

In our previous papers, we described a method for measuring the retention time which is a measure of the foam stability. In addition, the dependence of this retention time on surface elasticity was considered. On the basis of these results a simple mathematical formula for this dependence has now been derived and is tested by a fitting procedure. The formula is not very exact, however, but it can be used to explain the main influence of the adsorption properties on the stability of a wet foam.

High-Temperature Rheological Study of Foam Fracturing Fluids

Summary. Two significant observations were made during measurement of N2 foam properties at temperatures up to 300 degrees F [149 degrees C] in a high-temperature, high-pressure recirculating loop viscometer:foam fluids did not thin as rapidly as gel fluids under similar conditions, so foams offer inherent advantages for high-temperature stimulation work, andhigh gelling-agent concentrations do not improve dynamic foam stability; instead, high-temperature dynamic stability depends on surfactant type and concentration. Mathematical equations have been developed from experimental data to describe foam rheological behavior from 75 to 300 degrees F [24 to 149 degrees C], 0 to 80 quality, containing 0 to 80 lbm hydroxypropyl guar (HPG)/1,000 gal [0 to 9586 g HPG/m3] in the aqueous phase. Basic physical properties previously outlined determined foam rheological physical properties previously outlined determined foam rheological behavior at 75 degrees F [24 degrees C]. Foams were classified as yield-pseudoplastic-type fluids. This paper extends the previous work from 75 to 300 degrees F [24 to 149 degrees C] and covers a broader range of external liquid-phase compositions applicable to foam stimulation work. Introduction Reidenbach et al. recently outlined the basic physical properties that determine foam rheological behavior at properties that determine foam rheological behavior at 75 degrees F [24 degrees C]. Important laminar flow parameters included texture (bubble-size distribution), parameters included texture (bubble-size distribution), quality, liquid-phase properties (n and K), and yield point. Foam fluids were classified as yield-pseudoplastic point. Foam fluids were classified as yield-pseudoplastic or Herschel-Bulkley type. Because foams used for stimulation are normally used with bottomhole temperatures above 75 degrees F [24 degrees C], N2 foam properties were measured at temperatures up to 300 degrees F [149 degrees C]. Foam fluids did not thin as rapidly as base gel fluids under similar conditions. We had anticipated using n and K values for base gel fluids at elevated temperatures in the room-temperature foam equations to predict foam properties at elevated temperatures. Such calculated viscosities generally were lower than experimental viscosities at elevated temperatures. To include temperature effects properly, therefore, the original equations had to be modified. Theory The basic laminar flow equation for pressure loss of foam fluids in a pipe has been given asThe yield point, sigma yp, is a function of quality, gamma, only. Gamma is the ratio of gas volume to gas plus liquid volume at a specific temperature and pressure. For gamma less than 0.6,and for gamma greater than 0.6,The consistency index of the foam, Kf, depends on the consistency index of the liquid gel phase, KL, its quality, and a tabulated empirical constant, C1, according toIn actual use, C1 varies with liquid-phase gelling-agent concentration. The flow-behavior index, n, was assumed to be the same for both gel phase and foam. From the initial high-temperature experiments using 70-quality N2 foam and various gelling-agent concentrations, we did not know the functional relationship, if any, between yield point, consistency index, and flow-behavior index vs. temperature. It was apparent that the fluid-behavior index remained nearly constant with increasing temperature, but the consistency index decreased with increasing temperature. The effect of temperature on yield point with various gel concentrations was uncertain. Data are presented that examine the effect of these parameters on foam viscosity. Experimental Procedure The recirculating flow-loop viscometer was based on 0.305-in. [7.75-mm]-ID stainless-steel tubing. Valves in the flowline were the full-opening ball type. Fig. 1 is an outline of the flow pattern. The aqueous phase of the fluid to be tested was pumped from a 5-L pressure vessel to the loop by a metering pump. The loop was filled with liquid to a pressure of pump. The loop was filled with liquid to a pressure of 1,000 psi [6.9 MPa], as regulated by a backpressure regulator. During the filling process, fluid flowed through a mass flowmeter. Specific gravity was read to three decimal places with computer averaging. The specific gravity reading allowed foam quality to be adjusted on-line. A glass inspection gauge allowed visual inspection of the fluid. JPT p. 613

Measurement of dynamic foam stability

On propose des verifications experimentales de l'hypothese de Watkins, dans lesquelles la mousse est produite dans des conditions identiques dans des recipients cylindriques et coniques. Mise en evidence de l'influence de la forme du recipient sur les proprietes rheologiques des mousses