Batch Foam Fractionation Research Articles

Precipitation of proteins from soybean whey wastewater by successive foaming and defoaming

To remove whey soybean proteins (WSP) from soybean whey wastewater (SWW), a continuous technology of successive foaming and defoaming was developed to precipitate WSP based on the foam fractionation of WSP from SWW. The roles of foaming and elevated temperature in precipitation of WSP were firstly investigated. The results show that foaming played the critical role in the precipitation of WSP, particularly the precipitation of lipoxidase, β-amylase and lectin, and elevating temperature enhanced the foaming-induced precipitation. Based on these results, the technology was optimized by studying the effects of temperature, pore diameter of gas distributor, superficial air flowrate and retention time on the removal yield of WSP. Under the conditions of length of foam column 700 mm, temperature 60.0 °C, pore diameter of gas distributor 120 ± 20 μm, superficial air flowrate 2.55 mm/s and retention time of 5.0 h, a high removal yield of 88.4 ± 3.9% was obtained. A SDS-PAGE analysis of the variation of WSP composition with retention time further confirmed the effective removal of WSP from SWW, and lectin was found to be the only soluble protein in the residual SWW. Compared with batch foam fractionation, the current technology was more effective in separating WSP from SWW.

Separation of anionic surfactant in paste form from its aqueous solutions using foam fractionation

Foam fractionation is an effective method for the removal and recovery of a surfactant from water. In this work, removal of an anionic surfactant (i.e. sodium dodecylbenzenesulfonate) was studied, at high concentrations, in a batch foam fractionation column. The anionic surfactant could be separated in a solid/paste form near the top of the column by using this process. High surfactant removal from water was achieved for surfactant concentrations varying from approximately near its critical micelle concentration to six times this concentration. The removal efficiency was reduced in the presence of salt (i.e. NaCl). The surfactant separation was enhanced by increasing the air flow rate. The recovery of surfactant was reasonably good. The recovery of water was good as well. The volume of foam and its age played important roles in the separation efficiency and the surfactant recovery. The adsorption of surfactant and the electric charge at the air–water interface were measured and analyzed to explain the separation efficacy. The bubble size increased with increasing air flow rate, and decreased with increasing surfactant and salt concentrations.

Modified β -CD-Cu ion complex and yam mucilage assisted batch foam fractionation for separating puerarin from Ge-gen ( Radix puerariae )

Abstract At present, the large scale application of batch foam fractionation is still in confrontation with many problems and difficulties, especially for the enrichment of non-surface-active materials. It is difficult to select a suitable surfactant as the collector when a non-surface-active material can only form a stable association with the expensive surfactants or has not any interactions with the commercially available surfactants. The objective of this work was to investigate the feasibility of batch foam fractionation for recovering such a non-surface-active material, puerarin. Yam mucilage, an abundant byproduct from the manufacture of yam starch, was used to generate a stable foam phase based on its good foamability. According to the properties of puerarin and yam mucilage, β -cyclodextrin ( β -CD) was selected as a basic material to establish an association between them. The results of fluorescence sensitization experiments indicated that puerarin could form an equimolar inclusion complex with β -CD and the inclusion constant was 405.8. Subsequently, β -CD was modified by introducing carbon disulfide and copper (Cu) ion. Then, puerarin could be adsorbed on the gas-liquid interface in the form of ternary complex with modified β -CD-Cu ion complex and glycoprotein molecules (see Fig. 7). Batch foam fractionation was carried out by using the crude extracting solution as the initial feeding solution, in which the concentration of puerarin was as high as 4.6 g/L. Under the suitable conditions of temperature 50 °C, pH 6.0, loading volume of feed solution 400 mL, the pore diameter of gas distributor 0.450 mm, additive volume of yam mucilage 30 mL and volumetric air flow rate 100 mL/min, the enrichment ratio and the percent recovery of puerarin were 4.3 and 82.3%, respectively. This strategy could be generalized to the separation of various non-surface-active materials due to the low cost and the diversiform cavity dimension of cyclodextrins.

The separation of catechol and phenol with each other by two-stage batch foam fractionation

Abstract A great amount of phenolic compounds are considered as carcinogens even at low concentrations and they are highly toxic and widely coexist in effluent discharges. It is a very meaningful work to respectively separate a few trace phenolic compounds from their aqueous solution by foam fractionation. The studies of surface activity and surface excess revealed that catechol had a stronger competitive adsorption on the bubble surface than phenol by using cetyltrimethyl ammonium bromide (CTAB) as a collector. A two-stage batch foam fractionation technology was developed for the respective separation of catechol and phenol from their diluted aqueous solution. In the first stage batch foam fractionation, catechol was effectively separated with a high enrichment ratio of 32.2 and a high removal percentage of 90.25% while the removal percentage of phenol was only 2.32% under the suitable operating conditions. A high selectivity coefficient of catechol over phenol could reach 35.25. Then, phenol existed in the residual solution, which was used as the feeding solution in the second stage. In the second stage batch foam fractionation, the small bubbles were used to enhance the adsorption of phenol. At the same time, the foam fractionation column of an inclined foam phase was used to enhance foam drainage and then phenol was effectively removed with a high enrichment ratio of 44.4 and a high removal percentage of 90.23% under the suitable operating conditions. The results indicated that it was practicable to successfully and respectively separate catechol and phenol from their aqueous solution by using the two-stage batch foam fractionation.

A novel process intensification approach of recovering creatine from its wastewater by batch foam fractionation

Foam fractionation is a cost-effective water treatment technology and it uses bubbles as the media for separating surfactants or non-surface materials from their aqueous solutions, where non-surface materials can be attached to the gas–liquid interface by using a surfactant as the collector. A novel two-stage batch foam fractionation was developed for recovering creatine from its wastewater. The objective of the first stage was to concentrate creatine from its wastewater and sodium dodecyl sulfate (SDS) was used as the collector. Under the suitable operating conditions, the enrichment ratio and the recovery percentage of creatine were 3.1 and 70.6%, respectively. Subsequently, the second stage was performed for isolating SDS from creatine by using the first stage foamate as the feeding solution. Under the suitable operating conditions, the recovery percentage of SDS reached 76.2% and creatine was massively remained in the residual solution because the complexation between creatine and SDS was eliminated through adjusting pH to 8.0. So, the total recovery percentage of creatine reached 59.3% and SDS in the second stage foamate could be reused for recovering creatine from its wastewater.

Separation of Bovine Serum Albumin by Foam Fractionation with Sieve Tray Column

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.

Isolation of soy whey proteins from isoflavones in the concentrated solution using foam fractionation

The isolation of whey soy proteins (WSP) from isoflavones in the concentrated solution using foam fractionation was studied, where the concentrated solution was the foamate of foam fractionation. It has been indicated that isoflavones existed in the form of complex with WSP in the foamate. The result of batch dissociation experiments showed that isoflavones were dissociated from WSP through adjusting temperature and pH. Foam fractionation was performed by using the foamate as the feeding solution under the conditions of temperature 50°C, pH 10.0, volumetric air flow rate 40mL/min and loading liquid height 400mm. The enrichment ratio and the recovery percentage of WSP reached 9.24 and 89.43%, respectively. The retention percentage of isoflavones in the residual solution was 90.02%. A two-stage batch foam fractionation was developed for successively achieving the enrichment of isoflavones from the soy whey wastewater using WSP as the collectors and the isolation of WSP from isoflavones.

Pilot study of recovery of whey soy proteins from soy whey wastewater using batch foam fractionation

For industrializing foam fractionation of whey soy proteins (WSP) from soy whey wastewater, a pilot study of 120L in liquid loading volume was conducted. Firstly the effects of sodium bisulfite concentration, superficial gas velocity and temperature were investigated for increasing the WSP recovery. Furthermore the protein composition of WSP before and after foam fractionation was analyzed. Then the effects of foam fractionation, thermal sterilization and spray-drying on the fraction of soluble proteins, foaming properties, and emulsifying properties of WSP were examined. Finally the up-scaling effect of foam fractionation was analyzed. The results show that the end product of WSP with an effective recovery of 30.6±1.5% had Kunitz trypsin inhibitor (the major ingredient), lipoxidase, β-amylase and lectin. The processing procedures, particularly foam fractionation and thermal sterilization, resulted in about 40% decrease in the levels of the food-related properties. The up-scaling effect slightly decreased the WSP recovery and intensified their denaturation.

Recovery of Isoflavones from the Soy Whey Wastewater Using Two-Stage Batch Foam Fractionation

The feasibility of recovering bioactive substances without surface activity from their aqueous solutions was studied using biosurfactants as collectors. For recovering the isoflavones from the soy whey wastewater, a two-stage batch foam fractionation was developed using the soy proteins as collectors. The results showed that when the conditions of the first stage were temperature of 60 °C, pH of 5.0, volumetric air flow rate 80 of mL/min, and loading liquid volume of 400 mL, a high isoflavones enrichment ratio of 4.05 was obtained and the residual solution could be used as the feeding solution of the second stage. When the conditions of the second stage were temperature of 25 °C, pH of 5.0, and volumetric air flow rate of 150 mL/min, the soy proteins concentration in the residual solution could decrease to 622 mg/L. By reusing the foamate of the second stage as the feeding solution of the first stage, the total isoflavones recovery percentage reached 87.72%.

Effect of invertase on the batch foam fractionation of bromelain

Foam fractionation can be used to enrich a hydrophobic protein such as bromelain from an aerated dilute protein solution because the protein foams. On the other hand, a protein such as invertase, which is hydrophilic, is not likely to foam under similar aerated conditions. While a foam fractionation process may not be approapriate for recovering a hydrophilic protein alone, it is of interest to see how that non-foaming protein affects the foaming protein when the two are together in a mixture. The bromelain enrichment, activity and mass recovery were observed as a function of the solution pH in order to explore how invertase can affect the recovery of bromelain in a foam fractionation process.

Effect of External Reflux on Foam Fractionation of Poly(Vinyl Alcohol).

The potential of foam fractionation for intra-process recycling of surface active materials is investigated. Batch foam fractionation of poly(vinyl alcohol) (PVA) was carried out with and without external foamate reflux. The effect of PVA concentration on foam fractionation without reflux was firstly investigated. The foam fractionation of PVA without reflux is possible only at initial PVA concentrations below 200 mg/l. At initial PVA concentrations above 300 mg/l, foam fractionation is impossible because almost all the water and PVA are discharged as foamate, of which PVA mean concentration is almost equal to that of the initial solution. Effects of external foamate reflux and temperature on foam fractionation of PVA were then investigated at initial PVA concentration of 1000 mg/l. With rising temperature, the enrichment and separation factor increases, while the removal factor is almost constant. The enrichment and separation factors at 363 K are about 11 and 90, respectively. External foamate reflux is essential for foam fractionation when treating a highly foaming solution.

Preserving the activity of cellulase in a batch foam fractionation process.

Foam fractionation is one of the low operating-cost techniques for removing proteins from a dilute solution. The initial bulk solution pH and air superficial velocity play an important role in the foam-fractionation process. Denaturation of proteins (enzymes) can occur, however, during the foam-fractionation process from the shear forces resulting from bursting air bubbles. At the extreme bulk solution pHs (lower than 3.0 and higher than 10.0), the enzymatic activity of cellulase in the foamate phase drops significantly. Within these two pH bounds an increase in the air superficial velocity, V0, and a decrease in the bulk solution pH leads to a decrease in the separation ratio (SR), defined as the ratio of the protein concentration in the foamate to the protein concentration in the residue. On the other hand, an increase in V0 provides a higher foamate-protein recovery. The process efficiency is defined as the product of foamate-protein recovery times the SR times the cellulase activity. The optimal operating condition of the cellulase foam-fractionation process is taken into account at the maximum value of the process efficiency. In this study, that optimal condition is at an air superficial velocity of 32 cm/min and a bulk-solution pH of 10.0. At this condition, the recovered foamate is about 80% of the original protein mass, the SR is about 12, and the enzymatic activity is about 60% of the original cellulase activity.

Quantitative investigations of cell-bubble interactions using a foam fractionation technique.

Previous work by the authors and others has shown that suspended animal cell damage in bioreactors is caused by cell-bubble interactions, regardless whether the bubbles are from bubble entrainment or direct gas sparging. As approach to measure the adsorptivity of animal cells to bubbles, a modified batch foam fractionation technique has been developed in this work and proven to be applicable. By using this technique, the number of cells absorbed per unit bubble surface area and the adsorption coefficients have been measured to quantify hybridoma cell-bubble interactions, and the preventive effects of serum and Pluronic F68 on these interactions. It was demonstrated quantitatively that the hybridoma cells adhere to bubbles spontaneously and significant numbers exist in the foam, and that both the serum and Pluronic F68 provide strong prevention to these cell-bubble interactions. The results obtained provide criteria for bioreactor operation and medium formulation to prevent cell-bubble interactions and cell damage in the culture processes.

Studies on Separation of Heavy Metals from Acidic Solutions by Foam Fractionation with Respect to an Application on Acidic Soil Extracts

An experimental investigation is presented on the batch foam fractionation of the heavy metal cations Pb2+, Cd2+, Cu2+, Sb3+ and As5+ from diluted aqueous solutions with hexamethylenedithiocarbamate (HMDC) as complexing agent and sodiumdodecylsulfate (SDS) as surfactant. Among the considered pH-values of 2,4 and 7 the pH 2 experiments allow a direct application of foam fractionation on acidic extracts from heavy metal contaminated soil. The experiments at pH 2 and pH 4 show better results than those at neutral pH. Although a simple device was used, a maximum enrichment factor of 13.8 and a minimum removal factor of 0.01 have been measured. The flotation with weak organic acids like citric acid (CA) and acetic acid (AA) show about 50–70% smaller enrichment factors than those acidified with hydrochloric acid. The dissolution and mixing of the reacting components as well as the concentration of the detergent and the gaseous volume flow can be regarded as basic parameters of foam fractionation.

Foam fractionation of cyanide complex anions of Zn(II), Cd(II), Hg(II) and Au(III)

An experimental investigation is presented of the batch foam fractionation of the cyanide complex anions of Zn(II), Cd(II), Hg(II) and Au(III) from 1.0 × 10 −5 M (metal concentration) alkaline aqueous solutions, with the cationic surfactant hexadecyltrimethylammonium chloride. The effects are established of the presence of CN − over the concentration range 2.5 × 10 −5M−1.0 M, of the presence of NO 3 − over the concentration range 0.05–0.75 M, and of interferences to metal foam fractionation provided by 0.50 M concentrations of NO 3 −, Br −, CN −, Cl − or SO 4 2−. Results are discussed in terms of the complex cyanide species of each metal that may have been present and in terms of the extent of hydration of the complex cyanide anions and of the potentially-interfering simple anions. The selectivity sequence, Au(CN) 4 −Hg(CN) 4 2−Cd(CN) 4 2−Zn(CN) 4 2− is established, both from data for single-metal solutions and for solutions containing equimolar concentrations of all four metals. A partial separation of the metals can be achieved in the presence of high concentrations of NO 3 −, which can be improved by taking maximum advantage of flotation rate differences.

Foam fractionation of solutions containing two surfactants in stripping and reflux columns

AbstractAn experimental and theoretical investigation was undertaken in order to examine the effect of concentration, foam flow rate and feed flow rate on the separation of sodium dodecylbenzene sulfonate and sodium lauryl sulphate from solutions containing the two surfactants, in stripping and reflux columns. The experimental results indicated the conditions under which a stripping foam fractionation column behaves according to the model of an infinite column. Within the present experimental range reflux columns behaved always according to the model of an infinite column. Using this model it is possible to predict relative separation of surfactants in stripping and reflux columns from experimental data obtained in simple columns. Experiments with modified total reflux columns indicate great potential for batch foam fractionation.

Foam Fractionation Rates

Abstract An empirical model enables the relation of the batch foam fractionation rate as a power function of the air rate and of the instantaneous residual surfactant concentration, eliminating the bubble size which is difficult to control and to measure. For the cationic surfactant, ethylhexadecyl-dimethylarnmonium bromide, the batch foam fractionation rate is directly proportional to the residual surfactant concentration to the first power, except for dilute (>45 mg/liter) solutions, and including suspensions containing colloidal ferric oxide and polynucleated, complexed cyanider Constants obtained from batch data can be used in the analogue equation for continuous operation to predict accurately the continuous foam fractionation rate, for a single air rate but over a substantial range of feed rates and feed surfactant concentrations. Continuous data from an entirely different column can be fit by a power function equation of the same form, with the power on the effluent or bottoms surfactant concentrat...