Frother Concentration Research Articles

Frother distribution in an industrial coal flotation circuit

ABSTRACT In reuse of process water in flotation plants, the inability to measure residual frother concentrations in both flotation and plant water circuits in real time has created challenges for flotation process control. We previously developed a simple and fast method to measure frother concentration based on the guest–host interactions between frother molecules and specially formulated liquid comprising cyclodextrin and pyrene. In the present study, the formulation and analysis procedure were upgraded to further improve the measurement sensitivity. The potential of the present method was demonstrated through methyl isobutyl carbinol (MIBC) concentration measurement at six different locations across an industrial coal flotation circuit. The measured MIBC distribution was in good agreement with that obtained using the colorimetric method developed by Finch and coworkers at McGill University. The implications of the established MIBC distribution in the coal flotation circuit for frother dosing and water reuse were discussed.

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.

Effect of Diesel Oil and Mixture of Alcohol-Glycol Ether on Colombian Ultrafine Coal Cleaning Using a Test-Rig Closed-Loop Flotation Column

A test-rig closed-loop flotation column was used to observe the effect of diesel oil (collector) and Flomin F-425 (frother) on mass yield and ash content for two Colombian coals: Caypa (northern zone) and Guachinte (southwestern zone). The coal samples of less than 38 µm (-400 M) were processed in a collector concentration range of 0,32 to 1,60 kg/ton of coal, as well as a frother concentration range of 10 to 50 ppm. The response surface methodology was used for the experimental test runs. The results showed that the maximum mass yield obtained by Caypa coal was 98,39% at 1,28 kg of collector/ton of coal and 40 ppm of frother concentration, whereas Guachinte coal obtained a maximum mass yield of 94,71% at 0,96 kg of collector/ton of coal and 30 ppm of frother concentration. In general, for Caypa coal, the mass yield tends to increase (low ash removal) with the collector and frother concentration increase; while the mass yield tends to decrease (high ash removal) for Guachinte coal when the collector concentration increases (low ash removal) at high frother concentrations. It is worth highlighting that the ash content of 0,65% obtained for Caypa coal is the lowest value reported in the literature while employing a test-rig loop flotation column in a single stage, which is considered to be an ultra-clean coal obtained by a physical cleaning process.

The interaction of a bubble with a particle-laden interface in frother solutions

Spherical glass particles of varying degrees of hydrophobicity were studied for their monolayer formation and compression behavior on an aqueous subphase containing different frothers at various concentrations. A Langmuir trough was modified to mimic the coalescence between two bubbles by forming a single bubble just below the particle layer. The change in the layer following the film failure between the bubble and the particle-laden particles was captured visually. The movement of particles and the behavior of the ripple formed during the coalescence were also investigated to characterize the interface oscillation under the effect of frothers. The results showed that the surface pressure isotherms of both hydrophobic particles were more sensitive to PPG 425 than 1-pentanol and MIBC and that a small increment in the concentration of PPG 425 in the subphase led to a significant increase in surface pressure. Both 1-pentanol and MIBC behaved like a dispersant in terms of interaction with the particle monolayer. The coalescence of bubbles caused the release of excess energy which was dissipated through the expansion and contraction of the newly formed interface. The speed of the waves (ripples) was found to reduce in the presence of the particle monolayer. While frother types did not have a significant effect on the speed of wave spreading, the increase in the frother concentration reduced the wave speed compared to water.

Adsorption Kinetics of Various Frothers on Rising Bubbles of Different Sizes under Flotation Conditions

This paper studies the effect of the type and concentration of selected frothers, the gas flowrate, and the pore size of the porous frit on the bubble sizes (Sauter mean diameter, SMD) of bubbling flow produced in a micro-flotation cell, and the determination of bubble size distribution (BSD) in the presence of the frothers. The commercial frothers polypropylene glycols (PPG 200, 400, and 600), tri propylene glycol (BTPG), triethylene glycol (BTEG), dipropylene glycol (BDPG), and Methyl Isobutyl Carbinol (MIBC) were used in the present investigation. The frother concentration varied from 1 to 1000 ppm. The flow rate varied in the range of 25 to 100 cm3/min. The pore sizes of the frit were selected as 10–16 μm, 16–40 μm, and 40–100 μm. Each frother exhibited its own unique ability in preventing coalescence of the bubbles in the order of BTEG &lt; BDPG &lt; PPG 200 &lt; MIBC &lt; BTPG &lt; PPG 400 &lt; PPG 600. The factorial experiments established that the type of the frother and its concentration have a major effect on the size of the bubbles. The bubbles decreased twice their size when the frother concentration was increased from 1 ppm to 1000 ppm. The pore size of the frit is a significant factor as well. The size of the bubbles can be reduced from about 10% to about 40% by decreasing the pores from 40–100 μm to 10–16 μm but the level of this decrease depends on the type of the frother. The increase of the flowrate from 25 cm3/min to 100 cm3/min produced bubbles smaller by 25% to 50% for the case of BTEG, BDPG, PPG 200, MIBC, BTPG, while a minimum of the bubble sizes was reached for the case of PPG 400 and PPG 600, beyond which the bubbles enlarged their size. The BSD in the presence of PPG 600 varied around 0.3 mm, whereas BTEG gave a wider BSD which indicated that the type of frother affected the bubble production. Our analysis shows that the first group of frothers adsorbs instantly on the bubbles, once they leave the porous frit, thus reaching equilibrium. PPG 400 and PPG 600 adsorb significantly slower on the bubbles, possibly not reaching equilibrium during their resident time.

Interfacial Tension Sensor for Low Dosage Surfactant Detection

Currently there are no available methods for in-line measurement of gas-liquid interfacial tension during the flotation process. Microfluidic devices have the potential to be deployed in such settings to allow for a rapid in-line determination of the interfacial tension, and hence provide information on frother concentration. This paper presents the development of a simple method for interfacial tension determination based on a microfluidic device with a flow-focusing geometry. The bubble generation frequency in such a microfluidic device is correlated with the concentration of two flotation frothers (characterized by very different adsorption kinetic behavior). The results are compared with the equilibrium interfacial tension values determined using classical profile analysis tensiometry.

Can small air bubbles probe very low frother concentration faster?

The existing literature on the rise velocities of air bubbles in aqueous surfactant solutions adsorbing at the water-air interface focuses mainly on large bubbles (D > 1.2 mm). In addition, due to the way the bubbles in rising bubble experiments are formed, their size is dependent on interfacial tension (the lower the interfacial tension the smaller the bubble). In this paper, smaller air bubbles (D < 505 ± 3 μm) are used to investigate the effect of the bubble size on the detection of two flotation frothers of different adsorption kinetics via bubble rise velocity measurements. We use an alternative method for bubble generation, allowing us to compare the rise velocity of bubbles of the same size in solutions of frothers of varying bulk concentration. The approach taken (ensuring consistent bubble size) ascertains that the buoyancy force component is kept constant when comparing the different solutions. As a consequence, any variations in the bubble rise velocity can be related to changes in the hydrodynamic drag force acting on a rising bubble. The interfacial behavior of frothers, i.e. the adsorption kinetics, interfacial activity and the maximum amount of molecules adsorbed at the interface, are determined from interfacial tension measurements and adsorption isotherms. The differences in the degree of tangential immobilisation caused by two different frothers are discussed in the context of differences in the structure of the dynamic adsorption layer, which is formed during the bubble rise.

Effect of frother strength on gas dispersion in a cavitation sparger measured by electrical resistance tomography

Axial dispersion in column flotation is critical for optimizing particle-bubble interaction and maximizing recovery. The effect of different flotation frothers on axial gas dispersion rates in a column flotation cell were measured using electrical resistance tomography (ERT). Gas holdup can be measured using ERT and utilized in the determination of axial gas dispersion rate in the column. The ERT is constructed with two sensor planes making it possible to simultaneously capture gas holdup values at and immediately above the cavitation sparger. Three frothers of varying strengths were used to investigate axial dispersion rates. Experimental conditions were modified by altering the superficial gas rate, frother concentration, and sparger pump speed. Utilizing a two-phase (gas–liquid) system, the effects of varying experimental conditions were captured and are represented using concentration tomograms. There is a strong positive correlation between axial dispersion rate, frother strength, and machine operating parameters.

Application of statistical analysis for optimizing of column flotation with pine oil for oil shale cleaning

ABSTRACT Oil shale must have a large quantity of kerogen to be of economic benefit, but oil shale with about 30% kerogen is a low-quality ore. Thus, the column flotation technique has been utilized to increase its quality, and the results were analyzed by a reduced two-level factorial design to optimize the interaction effects of seven parameters by response surface modeling. The perturbation plots were used to identify the optimum conditions leading to a predicted maximum kerogen concentration of 53.2% and kerogen recovery of about 81% at estimated optimum conditions of 15% solid concentration, 0.36 cm/s superficial wash water flow rate, 0.28 cm/s superficial feed flow rate, 10 ppm frother concentration, 10 cm froth depth, 1.5 cm/s superficial air flow rate, and 1.5 kg/t pine oil collector dosage. Whereas, the validation experiments under these optimum values gave similar kerogen concentration and recovery of about 52.9–53.6% and 80–82%, respectively.

Hydrophilic modification of polycarbonate surface with surface alkoxylation pretreatment for efficient separation of polycarbonate and polystyrene by froth flotation

Waste polystyrene (PS) and polycarbonate (PC) are crucial components arising from mixtures of plastic products, whose recycling is significantly limited by separation efficiency. In this work, to assist the flotation separation of PC and PS, we proposed a novel modification technology of surface alkoxylation pretreatment (SAP) where PC surface reacted with glycerol and urea. The SAP could selectively transform the hydrophobic PC into hydrophilic plastic, while the PS remained its hydrophobic surface owing to the exclusion from SAP process. Benefiting from the hydrophilic PC, the separation efficiency of PS and PC could reach the maximum of 99.34% under optimum conditions (urea dosage of 5 g, pretreatment temperature of 130 °C, pretreatment time of 10 min, flotation time of 2.5 min, frother concentration of 16.5 mg/L, and airflow rate of 7.2 mL/min). The mechanism of SAP was systematically analyzed by wettability, surface morphology, molecular weight, and chemical reactions. Compared with PS plastic, the pretreated PC presented better wettability, rougher surface, and significantly reducing molecular weight. The improvement of PC hydrophilicity can be attributed to the cleavage of ester bonds on backbone chains and the introduction of hydrophilic hydroxyl groups. The effective SAP process proves that chemical recycling of waste plastic can provide a novel strategy for surface modification and flotation separation of PS and PC.

Microwave treatment combined with wetting agent for an efficient flotation separation of acrylonitrile butadiene styrene (ABS) from plastic mixtures

Acrylonitrile butadiene styrene (ABS), as a main component of plastics of waste electrical and electronic equipment (WEEE), shows high potential for recycling, which is restricted by the absence of an efficient separation method. Herein, a novel surface treatment method, microwave treatment combined with a wetting agent, was proposed to selectively change the hydrophilicity of the mixed waste plastics, which efficiently separated ABS from the WEEE plastics by flotation. The results of this approach provided the following optimal conditions, i.e., microwave power 700 W, microwave irradiation time 3 min, concentration of wetting agent carboxymethylcellulose sodium (CMC) 25 mg/L, treatment time with CMC 5 min, stirring rate 1800 rpm, frother concentration 40 mg/L, and flotation time 4 min. Under these optimal conditions, the recovery and the purity of ABS reached 97.70% and 99.86%, respectively. The mechanism of the surface treatment was examined by means of contact angle, Fourier transform infrared spectroscopy (FT-IR), and adsorption kinetics. The results showed that the selective wetting mechanism can be attributed to the physisorption of CMC on the surface of plastics. In conclusion, this surface treatment method is expected to provide technological insights for the separation and recovery of waste ABS from WEEE plastics.

Optimization of gas parameters in a three-phase fluidized bed flotation column

The gas parameters, including gas holdup, bubble diameter and bubble specific surface area flux, of a three-phase fluidized bed flotation column (TFC) have been systematically studied. According to the characteristics of each stage of flotation the TFC is designed into three parts, the fluidized mineralization area, the buffer zone and the circulation section, and the solid particles are introduced into the fluidized mineralization area as regulatory factor. The gas holdup was calculated by measuring bed pressure drop, and the bubble diameter was measured by the conductivity probe method. Experimental parameters, including superficial gas velocity, superficial liquid velocity, solid particle type, frother concentration and initial static bed height, were studied. Experimental results show that the gas parameters can be optimized by changing experimental parameters. The models of gas parameters of the TFC have been derived. Experimental results have been compared with those in the relevant literature.

Application of froth flotation in the separation of polyvinyl chloride and polycarbonate for recycling of waste plastic based on a novel surface modification

The complicated stream of waste plastic impedes the recycling of polyvinyl chloride (PVC) and polycarbonate (PC), which can be settled by flotation separation. We proposed a novel chlorine dioxide (ClO2) pretreatment to assist the separation of PVC and PC by froth flotation, and clarified possible surface reactions of hydrophilic PC by contact angles, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The hydrolysis and further rearrangement of carbonic esters (O(CO)O) may be deemed as the main reason for hydrophilic PC, introducing oxygenated functional groups, such as hydroxyl groups (COH), carboxyl groups (COOH), and tiny acyl chloride (ClCO), on PC surfaces. The robustness of this process was proved by efficient flotation separation of PVC and PC under various conditions of size fractions, frother concentration, mass ratio, and flotation time. The optimal pretreatment conditions for flotation separation of PVC and PC are temperature of 70 °C, ClO2 concentration of 0.5 g/L, and treatment time of 70 min. The optimal recovery and purity of PC in sunken plastic can stably maintain 97% and 99%, respectively. Compared with waste plastic, raw PC embraces a high floatability after ClO2 pretreatment, revealing that ageing is conducive to surface modification.

Flotation separation of polyethylene terephthalate from waste packaging plastics through ethylene glycol pretreatment assisted by sonication

The recycling of packaging plastics is hindered by the various plastic mixtures and their similar surface properties. Plastic separation is a key step to improve recycling efficiency of waste plastics. We proposed a simple and efficient protocol to separate polyethylene terephthalate (PET) from polycarbonate (PC), acrylonitrile–butadienestyrene copolymer (ABS), and polyvinyl chloride (PVC) by converting PET surface from hydrophobicity to hydrophilicity. PET surface was modified by potassiumhydroxide (KOH)and ethylene glycol ((CH2OH)2) with the aid of sonication. Contact angle, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to research the reactions on PET surface. It can be confirmed that the reaction of base-catalyzed transesterification occurs, leading to a hydrophilic PET plastic. We investigated the effects of ultrasonic power, ultrasonic time, (CH2OH)2 dosage, KOH dosage, flotation time, and frother concentration on the flotation separation. The flotation recovery and purity of PET are 98.8% and 100%, respectively when (CH2OH)2 dosage is 10 mL, KOH dosage is 2 g, ultrasonic time is 5 min, ultrasonic intensity is 160 W, flotation time is 4 min, and frother concentration is 52.7 mg/L. This study provided a novel surface modification with reliable mechanisms for the flotation of PET from plastic mixtures.

Convection heat transfer and friction characteristics of liquid CO2-N2 foam fracturing fluid using C4F9OCH3 as frother

The liquid CO2–N2 foam fracturing fluid containing C4F9OCH3 causes no damage to formation, similar to dry CO2 fracturing, can be used to stimulate water sensitivity and low-permeability gas reservoirs. The main objective of this experimental study was to ascertain the convective heat transfer and frictional characteristics of this modified dry fracturing fluid system. A foam fracturing fluid test system was adopted in this study. The results showed that the viscosity of the liquid CO2–N2 foam fracturing fluid with C4F9OCH3 added was significantly higher compared with the liquid CO2–N2. The optimum frother concentration was 0.65%. The shear rate had the most significant effect on the convective heat transfer. The pressure had a significant effect on the frictional characteristics of the complex foam fluid due to the compressibility of the internal and external phases. When the flow velocity was greater than 1.4 m/s, the frictional resistance coefficients for foams of different qualities were similar. The velocities in the expression of the generalized Reynolds number, Re′, and the generalized Prandtl number, Pr′, were not sufficient to describe the influence of the shear rate on the heat transfer. When fitting the convection heat transfer coefficient, the effect of shear rate on coefficient of thermal conductivity was also considered. These results can be used to calculate the temperature field and predict the friction pressure drop in the use of this foam fracturing fluid.

Development of a laboratory-scale flotation column with inlet bubble size measurement

This paper presents the development of a small-scale (1 in.) laboratory flotation column with online measurement of bubble size. In contrast to the systems that use sampling-for-image techniques and have the viewing chamber located at the top of the flotation device, the system employed here measures the bubble size via image analysis using a bubble size analyzer located at the bottom of the column using a well-referenced sloped viewing chamber. The main advantage of this configuration is that it allowed the measurement and monitoring of the bubble size during flotation experiments (three-phase system). This was possible because the sizes of the bubbles were determined before they entered the column; moreover, the “cloudy effect” caused by fine particles in the bubble viewing chamber was minimized owing to the use of an expansion chamber (named the bubble injection chamber). The image capture, processing, and analysis were automated, which rendered it possible to determine the bubble size distribution and mean bubble size (D32) of consecutive images every 5 s using a simple image analysis procedure. Two-phase experiments conducted to evaluate the system showed that the mean bubble size (D32) and gas holdup were within the ranges found in the literature. As expected, the holdup was dependent on the bubble size, which was strongly dependent on the frother concentration. Finally, some exploratory experiments were conducted to test the apparatus in a three-phase system. Recovery-particle size curves for different bubble sizes showed that mass recovery increases as the mean bubble size decreases, and the coarser the particles, the greater is the effect of the bubble size on the recovery.

Efficient Dye Removal from Aqueous Solutions Using Rhamnolipid Biosurfactants by Foam Flotation

Methylene blue was efficiently removed from aqueous solution by foam flotation using a rhamnolipid biosurfactant as a dye collector. The effects of four parameters, namely, pH (1.5–11.5), frother concentration (5–65 ppm), aeration rate (2–6 L/min) and rhamnolipid to methylene blue weight ratio (0.5–6.5), on dye removal were studied and optimized using response surface methodology. Results showed that dye removal increases by increasing of all parameters; however, the nonlinear trend was observed for the effects of frother concentration and rhamnolipid to methylene blue ratio. Optimum removal conditions, resulting in about 93% dye removal, was achievedat pH value of 11.5, methyl isobutyl carbinol (MIBC) concentration of 35 ppm, airflow rate of 4 L/min, and rhamnolipid to methylene blue ratio of 3.5, after only 10 min flotation. Investigations also showed that the presence of electrolyte can significantly decrease the removal efficiency. Kinetics study revealed that the process follows the first-order model with a rate constant of about 0.288 sec- This study demonstrates that rhamnolipid could be considered as a potentially efficient and environment-friendly collector for the treatment of dye contaminated wastewater.

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.

Statistical analysis of Egyptian oil shale column flotation

ABSTRACT Evaluation possibility of a low-quality Egyptian oil shale from Wadii El-Nakhil, Red sea region as an alternative clean fuel by advanced flotation technique via column flotation was investigated. XRD analysis showed that the non-clay minerals associated with the oil shale sample include; quartz, siderite, apatite, anhydrite, and calcite. Column flotation experiments were carried out and results were analyzed according to screening designs which are used when numerous parameters would affect a particular process. Reduced three-factor interactions (3 FI) two-level factorial experimental design were employed to evaluate the effects of the seven independent parameters. Besides, the contour plots were used to summarize the optimum reaction factors leading to a predicted maximum kerogen grade of 52.35% and kerogen recovery of 78.41%. The calculated optimum parameters were 15% solid concentration, 0 cm/s superficial wash water velocity, 0.49 cm/s feed superficial velocity, 40 ppm frother concentration, 40 cm froth depth, 0.67 cm/s superficial air velocity and 0.5 kg/ton kerosene collector dosage. The confirmation tests, at optimum conditions as predicted from the contour plots, gave approximately the same grade and recovery of about 54% and 80%, respectively.

Separation of polyvinylchloride and acrylonitrile-butadiene-styrene combining advanced oxidation by S2O82−/Fe2+ system and flotation

A combining technology of advanced oxidation by S2O82−/Fe2+ system and flotation was proposed for separating polyvinyl chloride (PVC) and acrylonitrile butadiene styrene (ABS). In this research, sodium persulfate was activated by heating and ferrous ions. The separation efficiency of PVC/ABS oxidized by S2O82−/Fe2+ was higher than that by sodium persulfate. The mechanism of this process was investigated through contact angle, Fourier transform infrared spectroscopy (FT-IR) inductively coupled plasma (ICP), nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The floatability of ABS reduced owing to the introduction of oxygen-containing functional groups such as carbonyl (OCO) and hydroxyl (OH), which was a result of oxidation by sulfate radicals (SO4·-). The optimal conditions for separating PVC and ABS were: Na2S2O8 concentration 0.1 M, molar ratio (S2O82−/Fe2+) 200, treatment time 10 min, flotation time 4 min, frother concentration 14.7 mg L−1 and airflow rate 6.8 mL min−1. Novel kinetics of pretreatment time and flotation were proposed and researched in this work. The max rate constant of PVC/ABS flotation was 0.64 min−1. In addition, the pretreatment solution can be reused for three times with superior performance. The recovery and purity of PVC reached 100% and 99.7%, respectively. According to reasonable evaluation, the combination of S2O82−/Fe2+ advanced oxidation and flotation is a practical and efficient technology for separating PVC and ABS.