Flotation Frothers Research Articles

Co-flotation of effluents from detergent and marble processing industries in Denver and dispersed air flotation systems

Suspended solids in the marble processing wastewater (MPWW) have the potential to pollute receiving media. Likewise, detergent production wastewater (DPWW) needs treatment prior to discharge as they include surfactants and others. Flotation and its modifications are common for separation purposes in various engineering solutions. To increase flotation performance by changing the surface tension some collector and frother chemicals, surfactants are utilized. Detergents are among important surfactants and they may act as both frother and collector in flotation. Therefore, the purpose of this study was to determine the effectiveness of DPWW in co-flotation with MPWW. Two effluents were mixed at varying ratios and dispersed air (DISP) and Denver (DEN) flotation co-treatment were applied to the mixtures. Volume ratio, time and air flow rate on treatment performance were investigated. Turbidity, solids, COD, phosphate removals were achieved at varying levels when the flotation was applied to the mixture. The highest treatment performance was achieved at 90%MPWW-10%DPWW mixture. 10 min flotation time and 2 L min−1 air flow rate for the DEN system, and 20 min and 6 L min−1 for the DISP system were recommended. Under these conditions turbidity, SS, COD, phosphate and alkalinity residuals (and removal efficiencies) were 2400 NTU(82%), 1720 mg.L−1(89%), 313.6 mg.L−1(10%), 20 mg.L−1(20%) and 600 mg.L−1CaCO3(92%) in the DEN system, respectively. Whereas, in the DISP system, under the same conditions, final values of 1880 NTU(86%), 1540 mg.L−1(91%), 262 mg.L−1(17%), 21 mg.L−1(20%) and 470 mg.L−1(94%) were obtained, respectively. The highest SludgeSS concentration increased up to 19300 mg.L−1 in the 90%–10% mixture. In all samples, dewaterable sludge was obtained. By this study, co-flotation of these two effluents was recommended. Within SDGs, this approach will replace frother chemical usage. The process performance can further be enhanced via flotation modifications and technology can be developed as further study.

Frothers in flotation: A review of performance and function in the context of chemical classification

The significance of frothers in the context of mineral flotation is widely recognized, particularly in relation to their impact on bubble size and dispersion, coalescence inhibition, as well as the structure and stability of the froth. All these parameters hold substantial importance in determining the feasibility of the process including the overall recovery of valuable minerals and concentrate grade in flotation process. This review aims to offer a comprehensive overview of the importance of frothers in the flotation process focusing on their performance and function in the context of their chemical classification. The characterisation of flotation frothers is discussed, focusing on the most often used parameters including molecular weight, hydrophilic-lipophilic balance (HLB), dynamic frothability, and interfacial tension measurement. Additionally, the importance of advanced characterisation techniques such as single rising bubble experiments, high-speed video microscopy and infrared reflection absorption spectroscopy (IRRAS) is highlighted. Finally, the application of biodegradable and environmentally friendly biosurfactants such as rhamnolipids as “green frothers” in enhancing flotation rates is outlined.

Evaluation of lactate esters as novel biobased and environmentally friendly flotation frothers within PGM ore processing

As the mining industry moves towards more sustainable processing practices, the consideration of environmentally friendly reagents becomes important. Lactate esters are produced from renewable feedstock and considered green reagents because of their benign toxicological and environmental impact. Lactate esters may be considered to be suitable as flotation frothers owing to their heteropolar nature and the fact that they contain similar functional groups as commonly used industrial frothers. The most promising lactate ester, PURASOLV® BL, developed a stable froth with a lower level of entrainment than the commonly employed PPG frother, resulting in good metal recoveries and grades thereof. Utilizing lactate esters as novel green flotation frothers will attribute to the desired and mandatory shift towards greener reagents in PGM ore processing.

Interactions of NaCl with frother surfactants in producing microbubbles through modifying air/water interfacial energy and interfacial charge

The interactions of NaCl with flotation frothers (i.e., weak surfactants) were investigated in the production of microbubbles at low frother concentrations far below their critical micelle concentrations. Two widely used flotation frothers, methyl isobutyl carbinol (MIBC) which is an alcohol-based frother and Dowfroth 250 (DF250) which is a polyglycol ether-based frother were studied. While in-situ measurements of microbubble number and size distribution were carried out to indicate the production of microbubbles, interfacial energy and interfacial charge were determined to understand the generation and stabilization of microbubbles. It was found that a synergy occurred between NaCl and the tested frothers in producing microbubbles. However, the significant synergistic effect was only observed at a low frother concentration. In the case of MIBC, the synergistic effect was weakened at the tested high MIBC concentrations of 16 and 40 mg/L. In the case of DF250, the synergy turned antagonistic as the addition of NaCl slightly enlarged the bubble size and significantly reduced the number of microbubbles at the tested high DF250 concentrations of 16 and 40 mg/L. The effects were explained through possible interactions of NaCl with interfacial water molecules and with the tested frothers as well as through the NaCl’s effect of compressing the electrical double layers of air bubbles.

Effect of pine oil on the adhesion and biofilm formation of Acidianus manzaensis on chalcopyrite

Pine oil, commonly used as a flotation frother, could affect the bioleaching process. The attachment and biofilm development of acidophiles on metal sulfides were essential for bioleaching. This study focused on the role of pine oil in the early adhesion and biofilm development by Acidianus manzaensis YN-25 on the chalcopyrite surface. It was revealed that pine oil had a negative effect on the adhesion amount of A. manzaensis on the chalcopyrite surface. After having reached adhesion equilibrium, the percentage of attached cells decreased as the concentration of pine oil increased. The addition of pine oil was found to decrease the negative charge of chalcopyrite and cells, resulting in a higher attraction of acid-base interaction energy and total interaction force. This ultimately led to a stronger adhesion force between chalcopyrite and A. manzaensis. While the addition of pine oil initially delayed the formation of cell microcolonies during the first stage of biofilm formation, which ultimately resulted in larger biofilm coverage compared with the control group. The microcolonies on the mineral surface were also larger and the corrosion pits were bigger with the addition of pine oil. Furthermore, the addition of pine oil weakened the passivation effect and promoted the biological dissolution of chalcopyrite. This study offers a better understanding of the effect of pine oil on the bioleaching of chalcopyrite.

Electrostatic Forces in Control of the Foamability of Nonionic Surfactant

Can the DLVO theory predict the foamability of flotation frothers as MIBC (methyl isobutyl carbinol)? The flotation froth is a multi-bubble system, in which the bubbles collide, thus either coalescing or rebounding. This scenario is driven by the hydrodynamic push force, pressing the bubbles towards each other, the electrostatic and van der Waals forces between the bubbles, and the occurrence of the precipitation of the dissolved air between the bubbles. We studied the foamability of 20 ppm MIBC at constant ionic strength I = 7.5 × 10−4 mol/L at different pH values in the absence and presence of modified silica particles, which were positively charged, thus covering the negatively charged bubbles. Hence, we observed an increase in the foamability with the increase in the pH value until pH = 8.3, beyond which it decreased. The electrostatic repulsion between the bubbles increased with the increase in the pH value, which caused the electrostatic stabilization of the froth and subsequently an increase in the foamability. The presence of the particles covering the bubbles boosted the foamability also due to the steric repulsion between the bubbles. The decrease in the foamability at pH > 8.3 can be explained by the fact that, under such conditions, the solubility of carbon dioxide vanished, thus making the aqueous solution supersaturated with carbon dioxide. This caused the precipitation of the latter and the emergence of microbubbles, which usually make the bubbles coalesce. Of course, our explanation remains a hypothesis.

Influence of pH‐value and ionic concentration on the dynamic foamability index of flotation frothers

Influence of pH‐value and ionic concentration on the dynamic foamability index of flotation frothers

Improving the flotation recovery of Cu from flash smelting slags by utilizing cellulose-based frother formulationss

• First published study using polymer-surfactant mixes as frothers in Cu slag flotation. • Using the PS-mix improved overall Cu recovery compared to commercial frother. • PS-mix significantly increased productivity, i.e. similar froth product in less time. • PS-mix demonstrated superior tolerance in performance when reducing xanthate dosage. Froth flotation is an operation currently used for the recovery of Cu from pyrometallurgical smelting slags due its simple operation and relatively low operational costs. While it has been utilized for many decades, it may be necessary to develop strategies that improve Cu recovery from slags, as the unprecedented increase in Cu demand has made industrial waste and side streams economically relevant sources of metals. This study presents a novel chemistry-based approach for the flotation of Cu from smelting slags by utilizing an amphiphilic cellulose-surfactant mixture as a flotation frother, hereby referred to as CellFroth. The present work pursues two main objectives: i) to improve the performance of flotation for the treatment of smelting slags and ii) to accomplish a first proof of concept for frothers produced from renewable sources in the context of industrial waste treatment. The flotation performance of CellFroth was compared with a commercially available additive (i.e., DowFroth250) and hydroxypropyl methyl cellulose (HPMC). The results showed significant advantages in performance for CellFroth. At the highest collector concentration, Cu recovery was higher with CellFroth compared to DowFroth 250 and pure HPMC (73%; 62% and 65% respectively). A 75% reduction in xanthate concentrations had negligible effects on Cu recovery for CellFroth (70%), while recoveries decreased drastically with DowFroth250 (47%) and pure HPMC (50 %). Finally, CellFroth consistently reached comparable concentrate productivity (grade and recovery) as DF250 within significantly shorter flotation times. The use of CellFroth thus offers the possibility of increasing the Cu recovery from flash smelting slags, while reducing the environmental impact of the process by using a frother produced from sustainable sources and simultaneously reducing xanthate consumption.

Frother concentration measurement with a benchtop NMR spectrometer

In the present study, the previously developed frother concentration analysis technique based on the solid phase extraction process and the cryogen-free benchtop NMR is extended. We demonstrate that this technique can accurately quantify the concentrations of the most widely used flotation frothers such as methyl isobutyl carbinol (MIBC) and polypropylene glycol (PPG) type frother within 30 min even in presence of residual flotation collectors (e.g., diesel or ethyl xanthate) and inorganic electrolytes. It was also found that the present technique can determine the concentrations of individual frothers in frother blends in the simulated process water sample even in the presence of background chemicals. This technique has great potential for real-time measurement of frother concentration on-site as the whole process can be fully automated and does not require specialist staff to operate and maintain.

Degradation of novel mineral flotation reagent 8-hydroxyquinoline by superparamagnetic immobilized laccase: Effect, mechanism and toxicity evaluation

• The effect of main constituents of MPW on 8-HQ degradation was evaluated. • Favorable 8-HQ degradation efficiency was achieved in real lead–zinc mine water. • The biocatalyst exhibited efficient recyclability and reusability. • Degradation predominantly generated various structural 8-HQ oligomers/polymers. • TOC and toxicity were effectively reduced with the degradation of 8-HQ. The environmental impact of the mining industry requires efficient and eco-friendly technologies to mitigate the presence of mineral flotation reagents (MFRs) in mineral processing wastewater (MPW) prior to their discharge into the environment. In this work, for the first time, a robust, easily separable and reusable biocatalyst, Fe 3 O 4 @SiO 2 -NH 2 -Lac, was used for the degradation of a novel mineral flotation reagent 8-hydroxyquinoline (8-HQ). Under optimized conditions, Fe 3 O 4 @SiO 2 -NH 2 -Lac achieved 89.2% 8-HQ degradation efficiency within 6 h. The effect of the main constituents of MPW on 8-HQ degradation, including metal ions, organic solvents, surfactant, metal chelator and flotation frother was evaluated. The Fe 3 O 4 @SiO 2 -NH 2 -Lac also displayed favorable degradation efficiency of 8-HQ in real lead–zinc mine water. The biocatalyst could be easily recovered and had a satisfactory reusability, retaining 64.5% of 8-HQ degradation efficiency in the sixth reaction cycle. Identification of intermediate products revealed that Fe 3 O 4 @SiO 2 -NH 2 -Lac mediated reaction predominantly generated various structural 8-HQ oligomers/polymers. A potential degradation pathway for 8-HQ was speculated as follows: Fe 3 O 4 @SiO 2 -NH 2 -Lac initially catalyzed the oxidation of 8-HQ to yield the corresponding reactive radical intermediates, which subsequently undergone self-coupling reaction via C − C and C − O − C covalent coupling at their ortho and/or para positions, finally forming oligomers and polymers. The inhibition assays of marine bacterium ( Vibrio fischeri ) demonstrated that the toxicity of 8-HQ and its intermediate products was effectively reduced after Fe 3 O 4 @SiO 2 -NH 2 -Lac treatment. The results of this study might present an alternative immobilized laccase-based clean biotechnology for the clean-up and detoxification of 8-HQ contaminated MPW.

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.

Nano-Silica based mineral flotation frother: Synthesis and flotation of Platinum Group Metals (PGMs)

We report the synthesis and application of nanomaterials in the field of mineral processing. Nanotechnology is a potentially disruptive technology with a huge potential to open up new avenues of enhancing mineral recovery and grades in the domain of mineral froth flotation. In this investigation a solid, nano-silica (NS) based frother was synthesized using the sol–gel method for test works involving Platinum Group Metals (PGMs) and associated base metals. The nano flotation reagent was characterized using Fourier Transform Infrared Spectroscopy for chemical structure analysis (FTIR), Powder X-Ray Diffraction (P’XRD) for structural analysis and Field Emission Scanning Electron Microscopy (FESEM) for surface morphology and particle size distribution, Energy Dispersive Spectroscopy (EDS) for elemental analysis. X-ray fluorescence (XRF) was used for mineral assaying after flotation. The generated nano-silica had an average particle size distribution of 35–41 nm. The flotation performance of the nano-frother was benchmarked with a commercial conventional frother (SasFrother). At an optimum nano-frother dosage of 20 g/t a recovery of 73.8%, 77.0%, 84.0% and 78.2% platinum, palladium, nickel and copper respectively was realized. However, the associated grades were lower when compared with the conventional frother. On the other hand, increasing nano-silica dosage above the optimal dosage resulted in a reduction of the actual recovery for all the metals. Interestingly, the dosage requirement for the nano-frother required for optimal mineral recover was much lower than that of the conventional frother. Based on these findings, opportunities at nano scale can proffer numerous novel materials with exceptional properties for application in mineral froth flotation.

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

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

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

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

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.

Influence of Terpenic Oil on Flotation Behavior of Sphalerite and Implication for the Selective Separation

Terpenic oil (TO) is commonly used as a flotation frother for the selective separation of sulfide minerals. As a frother, most reports have mainly focused on its effect on froth stability and froth entrainment, whereas its influence on the floatability of sulfide minerals has received little attention. In this work, the influence of TO on the flotation behavior of sphalerite was investigated by using microflotation tests, contact angle and zeta potential measurements, and FT-IR and SEM-EDS analyses. Microflotation tests conducted in a modified Hallimond tube indicated that compared with the collector potassium butyl xanthate (KBX), the flotation recovery of sphalerite was significantly increased when TO was added to the pulp, but the recovery of Cu-activated sphalerite with the addition of TO was lower than that with the addition of KBX. Contact angle measurements demonstrated that the contact angle of sphalerite was distinctly increased by the addition of TO, but the contact angle of sphalerite treated with TO was lower than that treated with KBX after Cu activation. Zeta potential measurements demonstrated that the zeta potential of sphalerite particles was slightly decreased when treated with TO, and the isoelectric point (IEP) was decreased from 3.3 to 3.1 due to the interaction of TO with sphalerite particles. FT-IR and SEM-EDS confirmed that TO could be adsorbed on the sphalerite surface on the formation of the oil film due to its low solubility, thereby increasing the surface hydrophobicity of the sphalerite. In addition, the TO absorbed on the surface acts as a bridging role and promotes the hydrophobic agglomeration of sphalerite particles. These results suggest that except for froth entrainment, the influence of TO on the flotation behavior of sphalerite may be another reason for the misreporting of sphalerite in concentrates.

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.

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.

A recipe of surfactant for the flotation of fine cassiterite particles

Salicylhydroxamic acid (SHA) has been widely used as collector in cassiterite flotation, and α-terpineol (AT) and methyl isobutyl carbinol (MIBC) are common frothers in mineral flotation. The effects of AT and MIBC on cassiterite flotation have rarely been reported, which severely limits our understandings of the role of frother in cassiterite flotation. Here, comparative studies between AT and MIBC in affecting cassiterite flotation using SHA as collector were conducted through micro-flotation tests. Micro-flotation tests showed that the averaged value of the recovery of cassiterite with AT was 10% higher than that with MIBC at the same concentration. To unveil the mechanisms of enhancement effects of AT on the flotation of fine cassiterite particles, zeta potential measurements, contact angle measurements and surface tension measurements were conducted. Zeta potential of cassiterite surface shifted to more negative value in the presence of SHA, and the nonionic reagents, AT and MIBC, could not affect the surface potential of cassiterite. Contact angle measurements showed AT could adsorb on the surfaces of cassiterite particles, and therefore the hydrophobicity of particles was increased. In addition, there was a synergistic behavior between SHA and AT on cassiterite surface due to co-adsorption, and the cassiterite surface was more hydrophobic in the SHA/AT solution. Less surface tension and smaller bubble size were obtained in the SHA/AT solution compared to SHA/MIBC solution. These two combining effects, i.e. increasing the hydrophobicity of cassiterite particles and reducing the single bubble size, are beneficial to the flotation of cassiterite, which explains higher recoveries in cassiterite flotation when AT is used as frother and SHA as collector.

The effect of aliphatic alcohol frothers on the dispersion of oily collector

There has been perception that flotation frothers, a type of surfactants, can disperse oily collectors in water, promoting oil attachment on mineral particles. In this study, the effect of aliphatic alcohol frothers (including MIBC, 1-hexanol and diacetone) on the dispersion of dodecane in de-ionised water and NaCl solution was studied. It turned out that these frothers actually inhibited the dispersion of dodecane in de-ionised water, but promoted the dispersion in NaCl solution. The underpinning mechanism was then investigated to decouple the effect of these frothers on the subprocesses of dodecane dispersion, emulsion formation controlled by the interfacial tension between oil and water, and emulsion stabilisation controlled by zeta potential and rheology of oil droplets. It was found that these frothers could decrease the interfacial tension of dodecane/water interface to facilitate the formation of dodecane droplets in water, but they were unable to form stable protective coatings around dodecane droplets in de-ionised water, resulting in the coalescence of dodecane droplets. In NaCl solution, the presence of Na+ can improve the strength of protective coatings formed by frother molecules around dodecane droplets and therefore the stability of dodecane emulsion.