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Foam fractionation is a well-developed technology used to separate surface-active compounds from solution by exploiting their affinity for the air–water interface. The technology was founded in the 1940s and has since evolved into a key technology for treatment of many different pollutants from a variety of different industries such as textiles and dyes, heavy metals, proteins in food processing waste and even per- and poly-fluoroalkyl substances (PFAS). The technology has even progressed from a standard batch process to a continuous process with an applied reflux to being presently used as an in-situ groundwater remediation and soil remediation process. This review provides a snapshot of the historical evolution of foam fractionation, a discussion of the mechanism behind foam fractionation, the effect of key operating variables on the performance parameters, identification of the key transport processes that take place within a foam fractionation system, a review of the modeling of foam fractionation as a water treatment technology and a review of the applications of foam fractionation as a water treatment technology. [ABSTRACT FROM AUTHOR]

A multi-stage continuous bubble cap foam fractionation column was developed to achieve high separation performance using cetyltrimethyl ammonium bromide (CTAB) as a model surfactant. The effect of design and operating parameters on the overall performances was investigated at a steady state. The results illustrated that with increasing the airflow rate, the enrichment ratio of CTAB was decreased and its recovery percentage increased. When the feeding concentration of CTAB was greater than 0.2 g/L, the adsorption of CTAB at the gas-liquid interface was closed to equilibrium. Based on mass balances and equilibrium relationships, a new method of the number of theoretical stages by stage-to-stage calculation and graphics were presented on the foam fractionation column. [ABSTRACT FROM AUTHOR]

In this work, copper (Cu) was recovered from the discarded printed circuit board (PCB) of personal computer through foam fractionation. The discarded PCB was treated by acid leaching. The leaching yield of Cu ion reached 97.61% under the conditions of temperature 40ºC, nitric acid concentration 6 mol/L and leaching time 60 min. A novel foam fractionation column was developed to strengthen foam drainage. Under the suitable conditions of pH 4.0, volumetric airflow rate 70 mL/min, SDS concentration 0.12 g/L and loading liquid volume 500 mL, enrichment ratio and recovery percentage of Cu ion were 29.1% and 90.2%, respectively. [ABSTRACT FROM AUTHOR]

Foam fractionation for recovering leaf protein from alfalfa (Medicago sativa L.) has been investigated. The extraction yield of alfalfa leaf protein (ALP) from the dried alfalfa leaves reached 71.90% under the extraction conditions of pH 8.0, temperature 70°C, and extracting time 40 min. For strengthening foam drainage at room temperature, a novel foam fractionation column with a cross-internal component covered superhydrophobic coating was developed. By using the extraction liquor as the feeding solution, a two-stage foam fractionation had been performed. Under the suitable operation conditions, the enrichment ratio and the recovery percentage of ALP were 4.33 and 89.0%, respectively. [ABSTRACT FROM AUTHOR]

In this study, the kinetics study and separation mechanism of zinc ion removal from synthetic wastewater were investigated using the foam separation process. With increasing the pH, Zn(II) recovery increased, in which foam fractionation occurred at pH 1.5, 3 and 5.5 and ion flotation at pH 8. The kinetics study was also used to determine separation mechanism. The order of Zn(II) foam fractionation was n = 1, while the order of Zn(II) ion flotation was n = 2 at the first stage and n = 0 at the second stage. Water recovery kinetics also increased with increasing ionic strength. [ABSTRACT FROM AUTHOR]

In order to recovery whey protein from yak whey wastewater effectively, a facile method of foam separation to be suitable for the local nomadic herdsmen in Qinghai-Tibet Plateau has been established in this research. The effects of the four factors, protein concentration, gas velocity, temperature and pH, on the performance of foam separation were investigated. Based on the single factor experiments, the response surface software was adopted to optimize and to investigate conditions of foam separation for whey protein, and the optimal conditions were found to be protein concentration of 120 μg/mL, gas velocity of 310 mL/min, temperature of 41°C and pH of 3.8, respectively. The as-obtained results of verification experiments, recovery percentage 88.3% and enrichment ratio 9.25 showed that foam separation technique was a simple equipment and environmental compatibility method to separate whey protein from yak whey wastewater. [ABSTRACT FROM AUTHOR]

In this paper, a novel membrane-assisted fermentation coupling with foam separation (M-FCFS) technology was developed to separate polymyxin E from its broth immediately. The effects of starting aeration time, membrane, volumetric airflow rate in foam column, and nitrogen source (i.e. peptone, also known as foam stabilizer) on the production of polymyxin E were studied. Under the optimal conditions, the total titer (TT) of polymyxin E reached 1.29 × 106IU, resulting in a 50.4% improvement compared with the uncoupling experiment (8.60 × 105IU). This work combined the advantages of foam separation and membrane filtration, and provided a promising technology for the production of polymyxin E. [ABSTRACT FROM PUBLISHER]

Microalgae biomass has great potential for being used as feedstock for the sustainable production of biodiesel, as it is able to produce 7–31 times more oil than the top terrestrial crop. It is a green alternative to the currently utilized energy sources as it can reduce CO, CO2and hydrocarbon emissions. However, downstream processing costs for the dilute biomass are a major challenge. Foam flotation has been recently investigated for the recovery of microalgae cells from dilute liquid suspensions. A number of variables on the effectiveness of foam flotation for microalgae have been investigated, which include surfactant type and concentration, cell concentration, pH, hydrophobicity, time, growth stage, flow rate, ionic strength, alkalinity, temperature, bubble size, and column size. It appears to be a promising method for the recovery of algae for biofuel production, as a result of the high removal recoveries, good enrichment ratios, ability to process large volumes of biomass, and its ease of operation. However, literature on this subject is scarce, and there are research gaps that should be investigated including characterization of microalgae cells and impact on foam separation and the effect of surfactant as a treatment prior to lipid extraction. [ABSTRACT FROM AUTHOR]

A batch foam fractionation column with sieve trays was developed for enhancing the foam drainage. Effects of feeding concentration, air flow rate, number of stages, and sieve pore size on foam fractionation performances were investigated. The results indicated that the sieve trays enhanced the foam drainage effectively and improved enrichment ratio. At the liquid loading volume 490 mL, feeding concentration 0.1 g L−1, and air flow rate 300 mL min−1, the enrichment ratio reached 7.56 by using 10 stages of sieve trays with opening ratio of 38.25%, which was 1.84 times of that obtained by the control column. [ABSTRACT FROM PUBLISHER]

The present investigation was carried out to study the feasibility of foam separation for simultaneous removal of two types of inorganic hazardous contaminants, nickel(II) cations and chromium(VI) anions, from aqueous solutions and simulated wastewaters. The effects of pH of the solution, Ni/Cr ratio, collector and frother concentrations, induction and flotation time, and solution ionic strength on the co-removal efficiency of nickel(II) and chromium(VI) were studied. At the optimum conditions, removals more than 99.5% were obtained for nickel(II) and chromium(VI). The concerned contaminants were effectively removed when they coexisted at low as well as at high concentrations. Coflotation of nickel(II) and chromium(VI) from tap water and simulated electroplating wastewater resulted in removal percentages higher than 99.5% with residual concentrations below their permissible limits in potable water. High removal percentages, DFs, ERs, and VRs were achieved for their radionuclides,63Ni(II) and51Cr(VI), from simulated radioactive process wastewater. The results obtained in this study suggest the feasibility of the developed foam separation process for treatment, in a single-step, of wastewaters contaminated with cationic and anionic inorganic pollutants. [ABSTRACT FROM PUBLISHER]

In this study, an inclined foam separation column was designed to effectively recover protein from sweet potato starch wastewater. The effects of the influent protein concentration, pH, air flow rate, influent volume, foaming time, and inclined column angle on foam separation performance were assessed. The optimum foam separation conditions consisted of influent protein concentration 4.51 mg/mL, pH 4, air flow rate 0.15 mL/min, influent volume 500 mL, foaming time 100 min, and inclined column angle 30°. In these conditions, protein recovery percentage and enrichment ratios were 84.1% and 1.3, respectively. The biochemical oxygen demand (BOD5) and chemical oxygen demand (CODCr) of the residual solution (620 and 950 mg/mL, respectively) were lower than those of the original (influent) solution. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the use of foam fractionation to recover saikosaponins. First, the solvent extraction method was applied for the extraction of saikosaponins from radix bupleuri using ethanol or deionized water. Then, the foam fractionation technique in batch mode was used for the recovery of the total saikosaponins from the extract. The effects of initial concentration, air flow rate, liquid loading volume, pH, and operating time on the process performance were investigated. The recovery percentage 77.2% and an enrichment ratio 3.68 of total saikosaponins with one-stage separation were obtained under the optimal conditions of initial saikosaponin concentration 0.18 mg/mL, air flow rate 50 mL/min, liquid loading volume 200 mL, pH 5.5, and operating time of 2 h. A two-stage foam fractionation technology was also designed, which was effective for improving both the recovery percentage and enrichment ratio simultaneously. [ABSTRACT FROM PUBLISHER]

Sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, was removed from its aqueous solution by foam fractionation in an emulsion venturi, a gas-liquid contactor functioning in self-aspiration. The performance of the reactor was evaluated by measuring the self-aspired gas flow and the mass transfer coefficient in the presence and the absence of SDBS. Data confirmed that both the gas flow self-aspired and the mass transfer coefficient increased with increasing the recirculated liquid flow. However, the presence of SDBS decreased the mass transfer capacity of the reactor influencing self-aspiration capacity in a positive manner. The percentage removal of SDBS in the emulsion venturi increased with increasing the recirculated liquid flow; at the highest liquid flow value used in this work (1.4 m3/h), 96% of SDBS was removed from the solution after 20 min of foam operating. The process was dependant on initial surfactant concentration. Neutral pH and temperature of 25°C were the optimal conditions for the foam separation of SDBS in the emulsion venturi. [ABSTRACT FROM PUBLISHER]

A continuous multistage foam fractionation column with bubble caps was used for surfactant recovery from mixed surfactant solutions containing polyethylene glycol tert-octylphenyl (OPEO10) and cetylpyridinium chloride (CPC) and the effects of air flow rate, foam height, and feed flow rate were investigated under a steady state of conditions. For the mixed surfactant system, the effect of synergism in the surfactant adsorption density was found. For separation efficiency, the total residual factor remained unchanged with an increasing feed molar fraction of OPEO10(α), suggesting that the addition of OPEO10does not increase the total separation efficiency. The residual factor of CPC increased with an increasing molar fraction of OPEO10(α), while the residual factor of OPEO10was lower for the mixed surfactant systems. A competitive removal was found in that the OPEO10can compete with CPC for the bubble surface. The total separation factors and enrichment ratio of mixed surfactant systems were in-between the two single surfactant systems at a long foam residence time and, in contrast, showed antagonism at short foam residence. This is due to the difference in liquid entrainment in foam at long and short foam residence times. [ABSTRACT FROM PUBLISHER]

The foam fractionation method was applied for nanocellulose. Experiments were carried out with enzymatically pretreated nano-fibrillated cellulose (NFC) from softwood, as well as commercial products. Narrow channels (plateaus) between bubbles prevent the flow of coarse particles along the water, so that foam acts like a filter. The advantage of the method is no risk of clogging, which could be a big problem for conventional filters or screens. Mean particle size (effective size by means of dynamic light scattering measurement) was reduced by foam fractionation, and the reduction range depended on the cellulose grade and the type of surfactant. The yield turned out to be low, probably because of particle aggregation due to the interaction with surfactant. [ABSTRACT FROM PUBLISHER]

A recent publication of a method for the intensification of the foam fractionation of a protein by reducing the pressure in the column is examined. It is demonstrated by invoking the original experimental results and by a theoretical analysis that the proposed method has no inherent advantage over a conventional foam fractionation column operated under normal conditions. Possible methods for valid process intensification are also discussed. [ABSTRACT FROM AUTHOR]

A system for the removal of Cu2+ and crystal violet from aqueous solution by foam separation was used. The goal of this work was to explore a method for simultaneous desalination and decolorization by foam separation. In the aqueous solution of this work, Cu2+ was used for studying desalination and crystal violet was used for studying decolorization, respectively, and dodecyl benzene sulfonic acid (DBSA) (C18H29SO3H) was used as a surfactant. The effect of surfactant concentration, pH, superficial velocity, and foam height on the removal percentage and the enrichment ratio were studied to optimize the conditions. Under the optimum conditions, the removal percentage of Cu2+ and crystal violet were 96.5% and 96.3%, respectively, and the enrichment ratio of Cu2+ and crystal violet were 3.7 and 3.6, respectively. [ABSTRACT FROM AUTHOR]

A novel method to intensify the foam fractionation process by operating the column under reduced pressure was reported in this paper. It was found that a poorer foam stability, a bigger mean bubble size and a wider bubble size distribution in the foam layer, a less upward liquid flux and volumetric liquid fraction at the top of the foam layer, and a higher enrichment ratio but a lower mass recovery of the foam fractionation process were obtained under reduced pressures compared to the ones under atmospheric pressure. The most important effect of the reduced pressure on the foam layer during the foam fractionation process is the encouraged bubble coalescence process which was exhibited by those unusual foam properties discussed above. The limitations of this new method were also discussed. [ABSTRACT FROM AUTHOR]

Foam fractionation is a promising technology for protein concentration or purification. However, the presence of an antifoam agent in fermentation broth restricted direct application of the technology. A preliminary approach of the surfactant-assisted foam process was conducted with a simulated system consisting of targeted protein bovine serum albumin (BSA), and a mixed antifoam agent (AF520, silicon oil/PGE mixture). The effects of all three classes of surfactants (anionic SDBS, cationic CTAB, and non-ionic Tween-20) on BSA foam fractionation were examined respectively. Also, the influences of solution pH, PGE, BSA, and NaCl were taken into account. The results revealed that all three classes of surfactants could stabilize foam film, so that the foam process could be operated, while the ionic surfactant exhibited excellent performance on condition that it was allowed to firmly interact with BSA to form a more hydrophobic complex, especially for cationic CTAB. When solution pH was adjusted to 7.5 and CTAB was 20 mg · mL-1, 90% of BSA could be extracted from a previous non-foaming system containing 100 mg · mL-1 BSA and 4 mg · mL-1 AFA, and the enrichment reached 7.42. A higher enrichment of BSA could be obtained with increasing addition of AFA but at the expense of the recovery. On the contrary, increasing BSA concentration gave rise to an opposite performance. The experiments also showed that the foam stability of the system was substantially enhanced by NaCl, significantly lowering the enrichment. [ABSTRACT FROM AUTHOR]

The work investigates the separation of proteins from whey waste collected from a local confectionery by the foam fractionation technique in batch mode. The purpose of this work was to evaluate performance criteria of protein separation. The effects of pH, the concentration of initial feed solution, the nitrogen flow rate, the % gas hold up, the bubble diameter, the breaking time of foam, and the optimization of the protein-surfactant ratio (1.5:1) were investigated in detail. Maximum enrichment ratio (48.189), %Rp (96.378) were observed at a gas flow rate of 330 ml/min and pH 5 that is closest to isoelectric point of observed proteins (Bovine serum albumin, β-Lactoglobulin, α-lactalbumin). [ABSTRACT FROM AUTHOR]

The feasibility of foam separation as a technique was assessed for the recovery of streptomycin sulfate from the waste solution by using an anionic surfactant sodium dodecyl sulfate (SDS). The experimental parameters examined were SDS concentration, superficial gas velocity, initial pH, and liquid loading volume. The results showed that sodium dodecyl sulfate as the surfactant for foam separation had good foaming quality and could effectively concentrate streptomycin sulfate of the aqueous solution by technology of foam separation. The enrichment ratio and the recovery rate of streptomycin sulfate were 4.0 and 85%, respectively under the best operating conditions of sodium dodecyl sulfate concentration 0.4 g/L, superficial gas velocity 300 mL/min, liquid loading volume 300 mL and initial pH 6.0 when streptomycin sulfate concentration was 0.5 g/L. [ABSTRACT FROM AUTHOR]

A batch recovery of riboflavin via foam separation from industrial simulative wastewater was studied using a cationic surfactant, cetyltrimethyl ammonium bromide (CTAB). The experimental parameters examined were the surfactant concentration, air flow rate, pH, and foam height. Under optimal operating conditions obtained through an orthogonal experiment, the maximum enrichment ratio of 48.7 was achieved for riboflavin along with 99.3% removal efficiency. The optimal operating conditions had the concentration of CTAB at 0.3 g/L, air flow rate at 400 ml/min, foam height at 90 cm, and pH at 12. Therefore foam separation proved to be an effective method to recover the riboflavin in terms of the good enrichment and removal efficiency. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the recovery of surfactants using a multistage foam fractionator for three types of surfactants: cationic (cetyl pyridinium chloride, CPC); anionic (sodium dodecyl sulfate, SDS); and nonionic (polyoxyethylene(20) sorbitan monolaurate, Span80). The studied system was operated at a constant temperature of 25°C with a surfactant concentration in the range of 50 to 100% of CMC (critical micelle concentration). For any surfactant system, the enrichment ratio of surfactant increased with increasing foam height and number of stages but decreased with increasing effects of the air flow rate and feed concentration. For all studied surfactants, the removal efficiency of the surfactant was not significantly affected by changing the air flow rate, foam height, and feed concentration in the studied ranges. An increase in the number of stages showed a great improvement of both the enrichment ratio and the removal fraction for all three types of surfactants. In a comparison among the three studied surfactants, the separation performance, in terms of the enrichment ratio and removal was found to lie in the following order: CPC >Span80 > SDS, which can be explained by the foamability and foam stability of each surfactant. [ABSTRACT FROM AUTHOR]

To prevent the spread of acute gastroenteritis, which prevails during winter and is called the winter vomiting disease, it is necessary to develop a technology for the detection and removal of noroviruses (NVs) from contaminated water. In this study, the removal from municipal wastewater and concentration in foam of NVs using dispersed bubbles and milk casein as a surface-active protein were examined. Real-time reverse transcription loop-mediated isothermal amplification (RT-LAMP) as a new nucleic acid amplification method was used for NV detection. Although NV-GII was detected in two wastewater samples, NV-GI was not detected. By foam separation using dispersed bubbles, NV-GII was removed from wastewater and concentrated into the generated foam. The concentration of NV-GII in the collapsed foam water was more than approximately 8-fold higher than that in the wastewater. Because the generated foam can be analyzed by real-time RT-LAMP, it is possible to sensitively monitor NV pollution in aqueous environments. Here, we show for the first time the removal from aqueous solution and concentration of NVs in foam using dispersed bubbles and a surface-active substance. [ABSTRACT FROM AUTHOR]

Adsorptive bubble separation was used to remove polyvalent ion colligends Zn(II), Mn(II) and Cu(II) from aqueous solutions, for which optimum parametrical values that influenced the recovery of these ions were scrutinized. Additionally, the effect of some auxiliary ligands (malic acid, maleic acid, and EDTA) on the recovery was investigated. Sodiumdodecylsulphate (SDS) was used as a collector. The pH was measured as 5.5 and 4.0 for the solutions, which include metal∶SDS and metal∶SDS∶auxiliary ligand, respectively. In the metal : SDS mixtures, SDS has retained metal ions at pH 5.5, which was exactly the value of the membrane filtered water. Therefore, no further pH adjustment was necessary throughout the experiments. The metal ions were determined by inductively coupled plasma optical emission spectroscopy (ICP‐OES). The optimum experimental conditions (run time, SDS concentration, and the concentration of feed solution) on the recovery and enrichment of metal ions were also discussed. The maximum recovery rate was reached within 60 min. The optimum molar ratio between metal and SDS was found to be 1∶5, and it was shown that the recovery of metal ions increased with increasing concentration of SDS. The most suitable initial concentration of metal ions was 2×10 -5 M. The recovery rates for Zn(II), Mn(II) and Cu(II) in the presence of SDS was found to be 90.5, 99.8 and 73.4%, respectively. By adding malic acid, and maleic acid as auxiliary ligands, higher recovery rates were achieved, even in a shorter foaming time. For optimal recovery, the best molar ratio between metal:SDS:auxiliary ligand was 1∶5∶5. [ABSTRACT FROM AUTHOR]

A new method of emulsified oil separation for oily wastewater incorporating simple operation and shortened treatment time is necessary for improved wastewater treatment in some manufacturing plants. In the present study, the removal of emulsified oil from water by coagulation and foam separation using poly aluminum chloride (PAC) and milk casein was examined. By adding casein before the foam separation process, the oil removal was dramatically improved. By using surfactant (LAS) as a frother, the dosage of casein was drastically reduced. Furthermore, for processing actual oily water, LAS was unnecessary because a sufficient amount of surfactants for foaming was included in the wastewater. For treatment of the actual oily wastewater collected from a steel manufacturing plant, the optimum condition for PAC and casein was 30 mg‐Al/L and 10 mg/L, respectively, and the oil concentration decreased from 170 mg/L to 2.2 mg/L. After examining several types of oily wastewater, 96–99% of oil removal efficiency was obtained by adjusting the dosages of PAC and casein. Coagulation and foam separation using casein has shown a high potential as an alternative method to dissolved air flotation (DAF) for processing emulsified oil water. [ABSTRACT FROM AUTHOR]

Foam fractionation has the potential to be an inexpensive alternative to current protein drug concentration or separation methods; however, it has a few drawbacks. One is the fact that not all proteins form a foam layer when aerated at low concentrations. The other is the possible protein denaturation caused during the foaming process. Adding a detergent to the nonfoaming protein solution causes it to foam when aerated. Here, cellulase and lysozyme are studied as model proteins in this process. By themselves, both cellulase and lysozyme solutions hardly form a foam layer when aerated at concentrations below 1000 mg/L (1000 ppm). The addition of 100 mg/L of cetyltrimethylammonium bromide (CTAB) to a 200 mg/L cellulase solution increases the foam volume and makes it possible to almost quadruple (relative to the initial bulk concentration) the concentration of the resulting cellulase foam solution. The foaming, however, reduces the cellulase activity. Diluting the foam with β‐cyclodextrin regains some of the lost activity because β‐cyclodextrin strips CTAB away from the cellulase, which allows the cellulase to refold to its native state. CTAB detergent does not work well with lysozyme, but the addition of SDS detergent leads to a tripling of the concentration of lysozyme solution without any reduction in enzymatic activity. [ABSTRACT FROM AUTHOR]

Surfactants can be present at low concentrations in wastewater from many industries, such as papermaking or detergent manufacture. The surfactant must sometimes be reduced in concentration in order to meet environmental standards before discharging these wastewaters to the environment. Also, recovery of the surfactant for reuse is sometimes economical and desirable. Foam fractionation has been shown to be an effective method of removing anionic and cationic surfactants from water in a single stage in our previous work. In this study, the recovery of a cationic surfactant (cetylpyridinium chloride or CPC) from water by multistage foam fractionation in a bubble‐cap trayed column was investigated with one to four stages operated in steady‐state mode for surfactant concentrations less than or equal to the critical micelle concentration. In comparison with a single‐stage foam fractionator, CPC was found to be removed from water by the multistage foam fractionator much more effectively. Both enrichment ratio and surfactant removal fraction increase with increasing feed flow rate, foam height, and number of stages, but they decrease with increasing CPC feed concentration and air flow rate. This study has demonstrated that the multistage foam fractionator used in this study can achieve almost quantitative removal of the surfactant with high enrichment ratio and short residence time. Multistage foam fractionation is demonstrated to be an extremely effective method of reducing surfactant concentrations from low to even lower concentrations in wastewater. [ABSTRACT FROM AUTHOR]