Foam Flotation Research Articles

Removal of Cadmium(II) from Aqueous Solution by Ion Flotation Using Rhamnolipid Biosurfactant As an Ion Collector

In this research, the potential of cadmium removal from aqueous solution by foam flotation with a rhamnolipid biosurfactant sample was studied. The effects of different major operating conditions, such as rhamnolipid and cadmium concentrations, solution pH, aeration rate, and frother type and concentration, on the cadmium removal were investigated. The selectivity coefficients in the presence of rhamnolipid maintained definite orders as follows: cadmium > zinc, cadmium > copper, and zinc > copper. The selectivity coefficient of cadmium over copper was the highest one. The maximum removals of Cd from clean and Zn- and Cu-contaminated solutions were about 57%, 36%, and 48%, respectively. Kinetic studies indicated that ion flotation of cadmium follows a first-order equation with a kinetic rate of 0.0071 min–1. Although the removals are rather low, it seems that the use of rhamnolipid biosurfactant can be promising in heavy-metal removal from wastewaters by foam flotation with some modifications.

Development of a foam flotation system for harvesting microalgae biomass

The lack of efficient and cost-effective technologies for harvesting bulk quantities of microalgae biomass is a major obstacle to commercialisation of algae-derived biofuels. This article demonstrates the efficacy of a foam harvester that combines dispersed air flotation with foam fractionation to allow harvesting, concentration, and physical separation of particles in suspension. Fractional factorial experiments using polystyrene latex beads were combined with trials using microalgae to determine the relative importance of key design and operational variables (air flow rate, batch run time, foam column height, surfactant concentration, and surfactant type) on the particle concentration factor. The model revealed that highest concentration factors were gained using the following variables and variable interactions: cationic cetyl trimethylammonium bromide (CTAB), lower surfactant concentrations, and CTAB combined with high column heights. Variables that increased foam residence time produced the greatest concentration factors. Analyses of the harvest economics revealed that foam flotation consumes only 0.015kWh/m3 providing an advantageous cost–benefit relationship, and outcompeting many commonly used bulk harvesting technologies.

REMOVAL OF COPPER ION FROM WASTEWATER BY FLOTATION

Several industrial wastewater streams may contain heavy metal ions, which must be effectively removalbefore the discharge or reuse of treated waters could take place. In this paper, the removal of copper( II)by foam flotation from dilute aqueous solutions was investigated at laboratory scale. The effects ofvarious parameters such as pH, collector and frother concentrations, initial copper concentration, air flowrate, hole diameter of the gas distributor, and NaCl addition were tested in a bubble column of 6 cm insidediameter and 120 cm height. Sodium dodecylsulfate (SDS) and Hexadecyl trimethyl ammonium bromide(HTAB) were used as anionic and cationic surfactant, respectively. Ethanol was used as frothers and theoptimal removal conditions have been established. Successful removals about (98%) and (76%) could beachieved for copper ions with SDS and HTAB, respectively. Copper removal reached about 80% underthe optimum conditions at low pH; at high pH it became as high as 98% probably due to the contributionfrom the flotation of precipitated copper. It was found that the presence of NaCl in the solution reducedthe recoveries. Adding ethanol at 1% concentration increased the removal efficiency. From the results therate of flotation was found to be first order.

Influence of Main Flotation Parameters on Detachment of Hydrophilic Particle from Bubble

The influence exerted by free to move wetted perimeter between three aggregative states and by basic parameters of foam flotation on the size of hydrophilic particles extracted by this method is numerically estimated.

Mineralization of Bubbles during Flotation

The study is conducted for the dynamics of thinning of liquid film separating mineral particle and gas bubble at the moment of their collision in foam flotation. It is shown that for floatable and depressed minerals, the values of potentials of particles and the advancing contact angle as well as the values of potentials of bubbles and the surface tension of gas - liquid interface can be obtained by solution of problems on thinning of liquid film and determination of meniscus shape.

Effect of Activators on Cu(II) Removal by Adsorbing Colloid Flotation with Fe(OH)3

Laboratories studies were conducted for the removal of Cu(II) from aqueous solution using adsorbing colloid flotation with Fe(OH)3. The effects of pH, surfactant (sodium lauryl sulfate), and foreign ions (NO3 −, SO4 2−) on the removal efficiency of Cu(II) were investigated. Sodium lauryl sulfate was efficient as a surfactant for the removal of Cu(II) and the optimum pH was found at 8.0. Foreign anions highly inhibited Cu(II) removal efficiency. This limitation of foam flotation on Cu(II) removal at high ionic strength may overcome by the aid of activators. The applicability of activators to improve Cu(II) removal efficiency of foam flotation was verified experimentally. The adsorption and separation mechanisms for the removal of Cu(II) are discussed. The role of activators on Cu(II) removal is also discussed.

Recovery of proteins and microorganisms from cultivation media by foam flotation.

Foaming is often present in aerated bioreactors. It is undesired, because it removes the cells and the cultivation medium from the reactor and blocks the sterile filter. However, it can be used for the recovery of proteins and microorganisms from the cultivation medium. The present review deals with the characterization of model protein foams and foams of various cultivation media. The suppression of foaming by antifoam agents and their effect on the oxygen transfer rate, microbial cell growth and product formation are discussed. The influence of process variables on the recovery of proteins by flotation without and with surfactants and mathematical models for protein flotation are presented. The effect of cultivation conditions, flotation equipment and operational parameters on foam flotation of microorganisms is reviewed. Floatable and non-floatable microorganisms are characterized by their surface envelope properties. A mathematical model for cell recovery by flotation is presented. Possible application areas of cell recovery by flotation are discussed.

The deformation of soap film junctions by applied forces

The equilibrium configuration of soap films in a tetrahedral frame is well known, and a study is reported here of the displacement of the tetrahedral vertex formed at the junction of the Plateau borders between the films. Applying a force to this junction causes an increase in soap film area, and hence surface energy, which is modelled both theoretically and numerically. In the present work, this force is conceived as being due to the displacement of a small particle at the centre of the vertex and the energy dependence of the configuration on both the size of the particle and the magnitude of the displacement is calculated. The results underline the importance of the curvature of the films in any detailed analysis of the suspension of particles in a foam, as, for example, in the industrial process of foam flotation. The results are relevant also to problems of foam drainage and stability.

Improvement of the Removal Efficiency of Cd(II) from the Aqueous Solution by Adsorbing Colloid Flotation

Experimental investigations on the removal of Cd(II) from aqueous solution were carried out through adsorbing colloid flotation with Fe(III). The optimum pH for good removal was found to be 11. The effects of flotation time, pH, surfactant (sodium lauryl sulfate), foreign ions (NaNO3, Na2SO4, and Ca(NO3)2) on the efficiency of Cd(II) removal were discussed. The presence of foreign ions inhibit the Cd(II) removal by foam flotation. It was suggested that the limitation of foam flotation on Cd(II) removal may be overcome by the surface activity of mixed surfactant solutions. The application of the synergistic effect of mixed surfactant solutions to the improvement of the removal efficiency of foam flotation was verified experimentally.

Quantitative measurement of cell-bubble attachment in bubble columns using foam flotation techniques

A simple and convenient system for quantitatively measuring the number of adsorbed animal cells per unit of bubble surface area (Γ, unit: cells/cm2) was developed. The system was successfully applied to recombinant Chinese hamster ovary (r-CHO) suspension cultures to investigate the dynamic cell-bubble attachment in a bubble column. In serum-free medium, Γ values increased with bubble rising height (H) and cell concentration (C) and then became constant (about 1750 cells/cm2) when H and C were sufficiently high. In medium containing protective additives, the trends of Γ values with H were similar to that in serum-free medium. Compared with serum-free medium, polyvinyl-pyrrolidone (PVP) increased the Γ values to 1941 cell/cm2 whereas other tested additives decreased the values of Γ in some different degree.

The Improvement of the Removal Efficiency of Foam Flotation by the Synergistic Effect of Mixed Surfactant Solutions

Experimental investigations on the removal of Cd(II) from aqueous solution were carried out using a foam separation technique with sodium lauryl sulfate and sodium laurate. The effects of pH, surfactant, and foreign ions on the efficiency of Cd(II) removal are discussed. Foam flotation with sodium laurate gave better removal efficiency than with sodium lauryl sulfate. It was found that the presence of ions inhibited the Cd(II) removal by foam flotation. It is suggested that the limitation of foam flotation on Cd(II) removal may be overcome by the surface activity of mixed surfactant solutions. The application of the synergistic effect of mixed surfactant solutions to the improvement of the removal efficiency of foam flotation was experimentally verified in this work.

Review: Treatment and reuse of wastewater from the textile wet‐processing industry: review of emerging technologies

New ecolabels for textile products and tighter restrictions on wastewater discharges are forcing textile wet processors to reuse process water and chemicals. This challenge has prompted intensive research in new advanced treatment technologies, some of which currently making their way to full-scale installations. These comprise polishing treatments such as filtration, chemical oxidation and specialized flocculation techniques and pre-treatment steps including anaerobic digestion, fixed-film bioreactors, Fenton's reagent oxidation, electrolysis, or foam flotation. Though several of these new technologies are promising in terms of cost and performance, they all suffer limitations which require further research and/or need broader validation. A segment of the research deals with the separate handling of specific sub-streams such as dyebath effluents to which membrane filtration is sometimes applied. The main limitation of this approach is the treatment of the concentrate stream. The spectrum of available technologies may, in the future, be further broadened to include fungi/H2O2-driven oxidation, specialized bio-sorptive processes, solvent extraction, or photocatalysis. © 1998 SCI

Colloidal Titanium Dioxide Separation from Water by Foam Flotation

ABSTRACT Colloidal titanium dioxide (TiO2) was separated from an aqueous suspension (1000 ppm) by foam flotation using cationic or anionic surfactants. The effects of surfactant dosage, suspension pH value, suspension ionic strength, and gas flow rate on the dispersed-air flotation of colloidal TiO2 were investigated. TiO2 separation was almost complete in optimum conditions. It was found that the coulombic interaction between charged TiO2 particle surfaces and ionic collectors plays a dominant role in this system. Both flotation rate and foamate volume are dependent upon the gas flow rate. Foam flotation may find application in the separation of submicron TiO2 particles in suspend-photocatalyst systems.

98/00815 Flotation of fine coke particles from fly ash

Fine coke particles were separated from fly ash in a laboratory flotation cell. Almost 90% of particles by number were below 10 µm and one third of them was less than 2 µm. Fly ash was sampled directly from a surge bin in a power plant and from a refuse dump area. Kerosene and Diesel oil were compared as collectors, and MIBC and polyglycol – based agents – were used as frothers. The best separation coefficient of 0.8 was obtained for 18 kg/t of Diesel oil and 9 kg/t of commercial frother based on polyglycol. LITERATURE REVIEW Fly ash from hard coal combustion can contain 20% or even more combustible residue, usually in the form of coke. This coke with low sulphur content may be considered as valuable ecological fuel. On the other hand, commercial application of fly ash as a component in construction materials requires limited coke content. Up until recently fly ash from Gdansk power plants was deposited at dump sites which harmed the environment. Because several million tons of this waste material have been kept in wet condition, foam flotation was selected for coke removal from the fly ash. Literature review pertaining to fine coal and coke flotation is presented in Table 1. Besides of fly ash, fine coal flotation papers are also included because of many similarities in both flotation systems. Values in bold were calculated or estimated from the data provided by authors of the papers. First seven experimental systems, presented in Table 1, pertain to coal flotation. The coefficient of separation (CS), representing process efficiency, in the range of 31%–73% indicates that fine coal particles do not float easily. It is worth to mention that comparable process efficiency was obtained for the ASH and other flotation equipment, but the flotation time for the ASH was many times shorter. Inferior flotation results can also be attributed to the excess of collector causing increased froth viscosity and greater ash particles entrainment to the froth (Clarkson et al. 1994). Although processing results given by Babatchew are very impressive (raw concentrate grade 75–80%) no processing details were provided (Babatchew 1987).

Waste pyritic coal as a raw material for energetic industry

Results are presented of large lab. studies on coal desulfurization with foam flotation method improved by application of bioadsorption of Thiobacillus ferrooxidans bacteria to the modification of superficial properties of pyrite particulates from hydrophobic to hydrophillic ones. Results of coal desulfurization with and without bioadsorption have been compared. Bioadsorption improved pyritic sulfur removal by 30% (for coal from ‘Siersza’ mine; coal size 0.3 to 0.102 mm, S pyritic content 1.69%) after 6-week adaptation of bacteria and 30 min of bioadsorption. Bacteria concentration in 5% water suspension of coal reached 22 μg of biomass cm −3.

Potential for the use of pyrolytic tar from bagasse in industry

Tar from pyrolyzed bagasse was characterized according to its main structural features. Its solubility in NaOH solutions results in an alkaline tar solution (ATS) that exhibits surface active properties. The prepared ATS was successfully used as a foam flotation agent in copper mining, as a foaming agent in foam concrete formation, and as a fluidization agent for Portland cement manufacture. The potentialities of by-products of conventional pyrolysis and carbonization processed are stressed.

Treatment of Textile Wastewater by Foam Flotation

Foam flotation (adsorptive bubble separation) experiments in a packed bed reactor were conducted to investigate the efficiency of this process in reducing the color, turbidity and chemical oxygen demand (COD) of the textile wastewater obtained from a dyeing and finishing plant. Both hexadecyltrimethylammonium bromide (HTA) and sodium lauryl sulfate (NLS) were tested as a potential collector agent for foam flotation. Experimental runs have been extensively performed to determine the effects of the wastewater pH, air flow rate and amount of collector agent employed on the nephalematic turbidity unit (NTU) and color reductions and COD removal. The experimental results were utilized to determine the optimum operating conditions of those variables. Chemical coagulation using polyaluminum chloride (PAC) and organic polymer was also tested to show whether this method has complementary effect on enhancing the treatment efficiency of foam flotation.

Analysis of cell‐to‐bubble attachment in sparged bioreactors in the presence of cell‐protecting additives

To investigate the mechanisms of cell protection provided by medium additives against animal cell injury in sparged bioreactors, we have analyzed the effect of various additives on the cell-to-bubble attachment process using CHO cells in suspension. Cell-to-bubble attachment was examined using three experimental techniques: (1) cell-bubble induction time analysis (cell-to-bubble attachment times); (2) forming thin liquid films and observing the movement and location of cells in the thin films; and (3) foam flotation experiments. The induction times we measured for the various additives are as follows: no additive (50 to 500 ms), polyvinyl pyrrolidone (PVP: 20 to 500 ms), polyethylene glycol (PEG: 200 to 1000 ms), 3% serum (500 to 1000 ms), polyvinyl alcohol (PVA: 2 to 10 s), Pluronic F68 (5 to 20 s), and Methocel (20 to 60 s). In the thin film formation experiments, cells in medium with either F68, PVA, or Methocel quickly flowed out of draining thin liquid films and entered the plateau border. When using media with no additive or with serum, the flow of cells out of the thin liquid film and film drainage were slower than for media containing Pluronic F68. PVA, or Methocel. With PVP and PEG, the thin film drainage was much slower and cells remained trapped in the film. For the foam flotation experiments, a separation factor (ratio of cell concentration in the foam catch to that in the bubble column) was determined for the various additives. In the order of increasing separation factors (i.e., increasing cell attachment to bubbles), the additives are as follows: Methocel, PVA, Pluronic F68, 3% serum, serum-free medium with no additives, PEG, and PVP. Based on the results of these three different cell-to-bubble attachment experiments, we have classified the cell-protecting additives into three groups: (1) Pluronic F68, PVA, and Methocel (reduced cell-to-bubble attachment); (2) PEG and PVP (high or increased cell-to-bubble attachment); and (3) FBS (reduced cell attachment butslower drainage films compared with F68, PVA, and Methocel with some cell entrapment in those films). These phenomena are discussed in relation to the interfacial properties of the media reported in a companion Study (this issue). (c) 1995 John Wiley & Sons Inc.

Foaming and cell flotation in suspended plant cell cultures and the effect of chemical antifoams

Foam development and stability in Atropa belladonna suspensions were investigated as a function of culture conditions. Foaming was due mainly to properties of the cell-free broth and was correlated with protein content; effects due to presence of cells increased towards the end of batch culture. Highest foam levels were measured 11 days after inoculation. Air flow rate was of major importance in determining foam volume; foam volume and stability were also strongly dependent on pH. Foam flotation of plant cells was very effective. After 30 min foaming, ca. 55% of cells were found in the foam; this increased to ca. 75% after 90 min. Polypropylene glycol 1025 and 2025, Pluronic PE 6100, and Antifoam-C emulsion were tested as chemical antifoams. Polypropylene glycol 1025 and Antifoam C at concentrations up to 600 ppm had no adverse effect on growth in shake flasks; Pluronic PE 6100 has an inhibitory effect at all levels tested. Concentrations of polypropylene glycol 2025 and Pluronic PE 6100 as low as 20 ppm reduced foam volumes by a factor of ca. 10. Addition of antifoam reduced k(L)a values in bubble-column and stirred-tank bioreactors. After operation of a stirred reactor for 2 days using Antifoam C for foam control, cell production was limited by oxygen due to the effect of antifoam on mass transfer. Theoretical analysis showed that maximum cell concentrations and biomass levels decline with increasing reactors working volume due to greater consumption of antifoam to prevent foam overflow. The results indicate that when chemical foam control is used in plant cell cultures, head-space volume and tolerable foam levels must be considered to optimize biomass production. (c) 1994 John Wiley & Sons, Inc.

Flotation of powdered activated carbon with adsorbed gold(I)-thiourea complex

In non-cyanide technology gold is often leached by thiourea in acidic medium. Therefore, the potential techniques for recovering gold from thiourea solutions are of interest. A separation technique has been investigated in laboratory scale batch experiments, involving gold adsorption on powdered activated carbon; the latter was compared with granular carbon. Foam flotation was employed for the subsequent solid/liquid separation, using sodium oleate as surfactant. The promising results obtained were further studied by means of electrokinetic measurements. Motivation of this work was the possible application of the process in gold leach solutions, for instance, after heap leaching.