Solubilization and micellarenhanced ultrafiltration ofo-cresol by Sodium Dodecyl Sulfate Micelles

The solubilization and the micellar-enhanced ultrafiltration (MEUF) of o-cresol were investigated by using an anionic surfactant, sodium dodecyl sulfate (SDS). In order to study the solubilization behaviour of the solute, the semiequilibrium dialysis (SED) method was employed and stirred-cell ultrafiltration experiments were performed for the test of MEUF. The analysis of the results supported that approximately two surfactant molecules provide a location for the solubilized solute within micelle. In the removal of o-cresol by MEUF, as long as high SDS concentrations in the retentate (>0.2 M) are avoided, relatively good rejection of o-cresol (85 %) could be obtained under the conditions used (initial concentration ratio:[o-cresol]/[SDS]=0.2 and 0.6). Furthermore, the ultrafiltration processes were nearly at equilibrium, so that the permeate concentrations of o-cresol could be predicted from the SED results. The separation efficiency was greater at lower o-cresol concentrations when the SDS concentrations were fixed in the feed, while the rejection increased with increasing the SDS concentrations at constant intramicellar mole fraction of the solute Xc. In addition, as the o-cresol loading of retentate increased, the less SDS in the retentate permeated through ultrafiltration membranes. On the other hand, the higher o-cresol loadings reduced the fluxes of MEUF runs.     

Micellar enhanced ultrafiltration: A comparative study

A pilot plant study was carried out to evaluate the performance of continuous cross flow micellar enhanced ultrafiltration (MEUF) method for the simultaneous separation of phenol and ortho‐cresol from the aqueous phase using a cationic surfactant, cetyltrimethyl ammonium bromide. The membranes used in this study are polysulfone tubular hollow fibre membrane with 6 kDa and a ceramic membrane having pore diameter 50 nm with an active layer of microporous zirconia (ZrO₂) supported on α‐alumina, respectively. The work includes comparing the effectiveness of membranes based on pollutants structural parameters, membrane properties and membrane modules. The characteristic parameters such as the distribution coefficient (D), micelle binding constant (K_p) and micelle loading (L_m) were obtained at optimal experimental conditions. High initial rejections were observed (above 95%) for both the membranes and the permeate flux remained almost constant at 17 LMH. It was found that the polysulfone material membrane suited better for MEUF with higher and steady rejections over a period of time. High micelle leakage was observed in ceramic membrane. The energy consumption for hollow fibre polysulfone membrane was less than the ceramic membrane. © 2011 Canadian Society for Chemical Engineering     

Use of Micellar-Enhanced Ultrafiltration to Remove Dissolved Organics from Aqueous Streams

Abstract

Traditional ultrafiltration is ineffective at removing dissolved low molecular weight organics from water. In micellar-enhanced ultrafiltration (MEUF), surfactant is added to the water at concentrations well above the critical micelle concentration. Almost all of the organic originally dissolved (the solute) solubilizes in the micelles formed by the surfactant. The solution then passes through an ultrafiltration membrane with pores small enough to block micelle passage. The permeate contains (at most) only the unsolubilized solute and the surfactant monomer, both at very low concentrations. In this work, the criteria for selecting a surfactant are considered and MEUF is tested on an aqueous stream containing 4-tert-butyl-phenol with hexadecylpyridinium chloride as the surfactant. At high surfactant concentrations (0.25 M) in the retentate, rejections decrease, probably owing to the formation of n-mers (e.g., dimers, trimers, etc.) which are able to pass through the pores along with some solubilized solute. Also under these conditions, the viscosity increases while fluxes decline sharply. So long as these high surfactant concentrations are avoided, MEUF is an extremely effective separation technique, resulting in an average solute rejection of 99.7%, a permeate/feed ratio of 87%, and good fluxes under the conditions studied.     

Dynamic Analysis and Optimization of Surfactant Dosage in Micellar Enhanced Ultrafiltration of Nickel from Aqueous Streams

Abstract

The micellar enhanced ultrafiltration of Ni(II) ions from the aqueous solution was studied for the dead end system using 20KD Polysulfone membrane. Dynamic behavior of the system was studied with respect to the rejection, yield, and normalized flux. The effect of feed metal ion concentration, surfactant concentration, pH, transmembrane pressure, and S/M ratio was investigated and the optimization of S/M ratio was done. The optimum S/M ratio was 10 while the critical S/M ratio was 5. The effect of monovalent salts was studied on the rejection of metal ions for the salt concentration between 10 mM to 500 mM.     

Influence of feed concentration and transmembrane pressure on membrane fouling and effect of hydraulic flushing on the performance of ultrafiltration

Micellar-enhanced ultrafiltration (MEUF) is a promising technology developed for treating the wastewater containing metal ions or organic pollutants. One of the greatest problems in MEUF is membrane fouling which is mainly caused by concentration polarization, gel layer or cake formation caused by the deposition of surfactant micelles on the membrane surface and surfactant adsorption in the membrane interior. In this study, surfactant sodium dodecyl sulfate (SDS), which was used in membrane separation as colloidal particles, caused the flux decline. The transmembrane pressure (TMP) and feed concentration of SDS had significant influences on the flux. This paper presented that the lower TMP had a smaller effect on membrane fouling, and when SDS concentration was around the critical micelle concentration (CMC), lower permeate flux and higher additional membrane fouling resistance were obtained. The effects of three kinds of hydraulic flushing methods on membrane permeate flux were investigated, including periodic forward flushing, periodic backwashing and forward flushing followed by backwashing. It was found that when the periodic combined flushing interval was 10 min, forward flushing and backwashing phase times were 150 s and 90 s, respectively, and that combined flushing was more conductive to permeate flux recovery in this study.     

Concentration Polarization Effects in the Use of Micellar-Enhanced Ultrafiltration to Remove Dissolved Organic Pollutants from Wastewater

Abstract

Micellar-enhanced ultrafiltration (MEUF) is used to remove 4-tert-butylphenol (TBP) from aqueous solution, a separation for which traditional ultrafiltration is ineffactive. A micelle—forming surfactant is added to the solution. The micelles solubilize a high fraction of the TBP. The stream is then forced through an ultrafilter. Overall rejection of TBP was greater than 99%. under all conditions studied and did not decrease with increasing pressure drop. Micelles were completely rejected by membranes with pore size 10 000 Dalton MWCO and below. Concentration polarization affects MEUF fluxes under conditions of interest. Bel polarization theory does not completely explain MEUF flux behavior. Selection of optimum operating parameters in MEUF application are discussed.     

Interactions Between a Sulfobetaine-Type Zwitterionic Gemini Surfactant and Fatty Acid Alkanolamide in Aqueous Micellar Solution

The critical micelle concentration (CMC) of 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]-ethane betaine (GCS12) was measured using a tensiometric method in the presence of inorganic salts. Inorganic salt has a little impact on the surface tension and CMC of zwitterionic gemini surfactant. The CMC value of GCS12 is 0.07 mmol/L in distilled water, while all CMC values are around 0.04–0.05 mmol/L in the presence of 0.5 % NaCl, 2 % NaCl, and 2 % NaCl + 0.05 % CaCl₂. The interactions between GCS12 and non-ionic surfactant lauric acid diethanolamide (CDA) were investigated by measuring the CMC of their mixtures at different molar ratios. CDA and GCS12 form mixed micelles and exhibit synergism when the mole fraction of CDA is higher than 0.25. Both the steric effect of the head group and GCS12 charge affect the formation and stability of the mixed micelles. Small amounts of GCS12 with a lower CMC penetrate into the micelle of nonionic surfactant with a higher CMC and reduce its degree of hydration inducing an attractive interaction between the two surfactants.     

Modulation of Aggregation Behaviour of Anionic Surfactant in the Presence of Aqueous Quaternary Ammonium Salts

The self-aggregation of sodium dodecylsulphate (SDS), an anionic surfactant, in aqueous solutions of tetraalkylammonium bromide salts (R₄NBr, where R = propyl, butyl and pentyl) was determined at various temperatures in the range 288.15–318.15 K. The critical micelle concentration (CMC) determined from conductivity data was used to study the thermodynamics of the surfactant. The presence of bromide salts was found to affect the micellization of SDS in accordance with the hydrophobicity of the tetraalkylammonium cations, thus the CMC values follow the order no additive > Pr₄NBr > Bu₄NBr > Pen₄NBr. The results from conventional conductivity methods were combined with those of spectroscopic techniques like fluorescence and UV–Vis studies.     

Membrane Characteristics and Fouling Study in MEUF for the Removal of Chromate Anions from Aqueous Streams

Abstract

Micellar‐Enhanced Ultrafiltration (MEUF) of the chromate anions from aqueous solutions has been studied at room temperature (28±2°C) using cationic surfactants, cetyltrimethylammonium bromide (CTAB), and cetylpyridinium chloride (CPC), micelles of which adsorb the chromate ions by electrostatic interactions. The solution is processed by ultrafiltration, using a membrane with a pore size small enough to block the passage of the micelles and the adsorbed ions. The process is highly efficient in removing the chromate ions. In the absence of other electrolytes, chromate ion rejections up to 99% were observed at optimal conditions of pH, pressure, temperature, feed chromate, and surfactant concentrations. The presence of added NaCl reduces the chromate rejection, but it was still considerable (up to 82%), even in the presence of 100 mM NaCl. The rejection rate of chromate was found to be highly dependent on the pH of the feed solution. The influence of membrane characteristics on the chromate ion removal was also studied. Various resistances like fouling resistance, concentration polarization resistance, and membrane resistance were also estimated to quantify their effects on the removal efficiency and on the flux behavior.     

Synthesis of Thumba,Castor and Sal Fatty Ethanolamide-Based Anionic Surfactants

The study involved the preparation and evaluation of anionic surfactants from non-edible oil based thumba (containing unsaturated-rich fatty acids, 80.9 %), castor (containing ricinoleic acid, a hydroxy fatty acid 89.3 %) and sal (containing saturated-rich fatty acids, 56.5 %). The oils extracted from these seeds (using Soxhlet) were reacted with monoethanolamine and diethanolamine to get corresponding fatty mono- and diethanolamides. The ethanolamides were sulfated using chlorosulfonic acid and the sulfated sodium salts were evaluated for surfactant properties namely surface tension, critical micelle concentration (CMC), emulsifying property, wetting, foaming power and calcium tolerance. The properties were compared with sodium dodecyl sulfate (SDS) a well known anionic surfactant. Among the different sulfated sodium salts of ethanolamides, thumba showed superior surfactant properties compared to castor and sal. Sulfated sodium salt of thumba monoethanolamide showed better properties (CMC, 0.035 mmol/L, surface tension 30.2 mN/m and calcium tolerance >1,000 ml, 0.5 % calcium acetate solution) compared to sulfated sodium salts of thumba diethanolamides, followed by sulfated sodium salts of castor monoethanolamide (CMC 0.037 mmol/L, surface tension 35.3 mN/m and calcium tolerance >1,000 ml, 0.5 % calcium acetate solution). Sal being saturated rich was not properly soluble in water and showed poor surfactant properties compared to the other two. Also the sulfated sodium salts of thumba and castor ethanolamides exhibited superior properties compared to SDS.     

Optimization of lead removal from aqueous solution by micellar-enhanced ultrafiltration process using Box-Behnken design

The main objective of this research was to use Box-Behnken experimental design (BBD) and response surface methodology (RSM) for optimization of micellar-enhanced ultrafiltration (MEUF) to remove lead ions from synthetic wastewater using spiral-wound ultrafiltration membrane. The critical factors selected for the examination were surfactant concentration, molar ratio of surfactant to metal (S/M) and solution pH. A total of 17 experiments were accomplished towards the construction of a quadratic model for both target variables. The experimental results were fitted with a second-order polynomial equation by a multiple regression analysis, and more than 95%, 93% of the variation could be predicted by the models for lead rejection and permeation flux, respectively. The optimum condition was found by using the obtained mathematical models. Optimization indicated that in C _SDS =2mM, pH=6.57 and S/M= 9.82 maximum flux and rejection efficiency can be achieved, simultaneously.     

Analysis of fouling mechanisms and membrane cleaning during ultrafiltration of bee venom

ABSTRACT

The knowledge about permeate flux decline regarded to apitoxin can be a useful tool to allow industrial fractionation of the mixture. Hermia’s models were used to predict the fouling mechanisms during cross-flow ultrafiltration of bee venom in 10 kDa regenerated cellulose membrane. Three different apitoxin concentrations (0.2 to 1 g/L) were tested at 1 bar and 0.08 m/s. Fouling mechanisms varied as a function of feed content. Membrane cleaning with sodium dodecyl sulphate was effective. Phospholipase A₂ rejection coefficients were a function of membrane fouling, varying from 35 to 93%.     

Micellar Enhanced Ultrafiltration of Organic Dyes

At a critical micelle concentration, surfactant micelles attract oppositely charged metal ions on their surface by columbic force and organic dyes can be entrapped by the micellar core via hydrophobic-hydrophobic interaction. Methylene Blue (MB) and Reactive Black 5 (RB5) dyes were removed by ultrafiltration with the help of oppositely charged surfactants SDS and CTAB. Simultaneous separation of Alizarin Red S (ARS) and zinc ions was accomplished by chelation and micellization. Thermodynamics of micellar enhanced ultrafiltration (MEUF) was discussed and the separation performance of the process measured in terms of the rejection percentage and the permeate flux which were evaluated by using the membranes of variable pore sizes.     

Highly efficient removal of phenol from aqueous solutions using graphene oxide/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite membrane

To achieve superior separation performance in the phenol aqueous solutions treatment, a novel graphene oxide/Al₂O₃ composite membrane was prepared by a spin coating process. The microstructure measurement shows that the composite membrane has a multilayer structure and graphene oxide has been tightly coated on the surface of the Al₂O₃ membrane interlayer homogeneously. During the treatment of phenol aqueous solutions, the permeation flux and phenol rejection of the composite membrane were investigated. The results show the permeation flux of the membrane is about 1.153 L m^?2 h^?1 bar^?1 and the phenol rejection of the membrane increases to 99.9% when the phenol concentration is 0.01 g L^?1. The high phenol rejection of the composite membrane is mainly attributed to the physical sieving, the solution–diffusion effect and the hydrophobic nature of graphene oxide. All these results indicate the GO/Al₂O₃ composite membrane is a suitable material for the removal of phenol from aqueous solutions in environmental pollution management.     

Stimulation of Phenol Removal Efficiency of Aspergillus versicolor by Surfactants,a Promising Way to Treat Phenol-Containing Waste Waters

The effect of the cationic surfactant, dodecyl trimethyl ammonium bromide (DTAB), on phenol bioremoval efficiency of an Aspergillus versicolor strain was examined. The strain was grown in mineral salt (MS) medium and the effect of DTAB was investigated as a function of different pH values, phenol and surfactant concentrations. The effect of pH was tested within the range of 4–7 and the maximum bioremoval was found at pH 4. Initial phenol concentrations investigated ranged from 100 to 600 mg/L, and the effects of surfactant concentrations on the removal were tested with 0, 0.25, 0.5 and 1 mM DTAB, which showed that 0.5 mM surfactant was the most effective concentration. The maximum bioremoval rates found after 72 h incubation were 99.48 and 99.15 % in 100 and 200 mg/L initial phenol-containing samples, respectively, where the phenol removal capacity of the fungus was only 142.373 mg/g in the DTAB blank samples. The maximum phenol uptake capacity of 267.162 mg/g was measured in the presence of 0.5 mM DTAB at 200 mg/L initial phenol concentration. These results showed that DTAB considerably increased the bioremoval efficiency of the strain tested at relatively lower phenol concentrations. The feasibility of this bioremoval method for industrial wastewater treatment is discussed.     

Colloid‐Enhanced Ultrafiltration of Chlorophenols in Wastewater: Part V. Simultaneous Removal of a Chlorophenol and a Metal Ion

Abstract

Polyelectrolyte micellar‐enhanced ultrafiltration (PE‐MEUF) is a separation process to remove target solutes from water using a mixture of a surfactant and an oppositely charged polyelectrolyte as a colloid. An organic solute and a metal cation can simultaneously associate with the colloid, which is subsequently ultrafiltered from solution. An organic solute solubilizes in the surfactant micelle‐like aggregates whereas an inorganic cation binds onto the oppositely charged polyion chains. The solution is then passed through the membrane having pore sizes small enough to block the passage of the surfactant‐polymer aggregates. In this work, PE‐MEUF has been applied to mixtures containing dichlorophenol (DCP) and magnesium ion (Mg²⁺), using cetylpyridinium chloride (CPC) and sodium poly(styrenesulfonate) (PSS) mixtures. It was observed that the presence of Mg²⁺ does not affect DCP rejection. The [CPC] to [PSS] ratio and colloid concentration have a significant effect on both DCP and Mg²⁺ rejections. Increased ionic strength from added salt increases the gel point (colloid concentration at which flux is zero). The viscosity of the colloid solution is inversely related to the gel point.     

Separation of Liquiritin from Glycyrrhizic Acid in Licorice Root Extract by Nanofiltration Membrane

The aim of this work was to study the separation of liquiritin (LQ) from glycyrrhizic acid (GA), in licorice aqueous solutions using nanofiltration (NRT-7450) membrane. The LQ and GA components are the main active ingredients of licorice root extract with various pharmacological effects, The effects of transmembrane pressure, feed temperature, feed pH, and cross-flow velocity on permeate flux and recovery were determined. A lab scale cross-flow set up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the fouled surface during operating time. The applied transmembrane pressure, feed temperature, feed pH, and cross-flow velocity were varied from 4 to 10 bars, 30 to 40°C, 3 to 9, and 0.8 to 3.1 m s^?1 respectively. The obtained recoveries for GA and LQ varied between 0.65 to 1.86% and 16.89 to 41.65%, respectively. The optimum operating conditions for separation LQ from GA in licorice aqueous solutions using NRT-7450 nanofiltration membrane were 1.8 m s^?1cross-flow velocity, 8 bars transmembrane pressure, 40°C of feed temperature and pH 7.     

Cloud Point Extraction of Nitrobenzene using TX-100

Cloud point extraction (CPE) is carried out to extract nitrobenzene (NB) from aqueous solution using TX-100 as a nonionic surfactant. The effects of different operating parameters, like concentration of the feed mixture (both NB and surfactant), pH, temperature, and the presence of mono- and di-valent salts on the extraction of both the NB and surfactant have been studied in detail. The solubilization behavior of the NB in the surfactant micelle has been observed in the temperature range of 75°C to 90°C. Concentrations of surfactant and NB have been considered in the range of 0.03 M to 0.25 M and 100 mg/L to 400 mg/L, respectively. An optimum set of surfactant concentration, temperature, and salt concentration is obtained for the removal of NB from aqueous medium. The effects of temperature and concentrations of surfactants and NB on various thermodynamic parameters, like change in Gibbs-free energy (ΔG ⁰), change in enthalpy (ΔH ⁰), and change in entropy (ΔS ⁰) are observed and explained well. Experimental investigations have also been carried out for the recovery of the surfactant from the dilute phase applying solvent extraction (SE) in batch condition using heptane and hexane as the extracting medium.     

Rejection of As(III) and As(V) from arsenic contaminated water via electro-cross-flow negatively charged nanofiltration membrane system

A specially designed electro-cross-flow nanofiltration (NF) membrane system was used for this investigation. To enhance the rejection of arsenic ionic species like H₂AsO₄⁻, a NF membrane having a negative surface charge was fabricated via the interfacial polymerization process. The membrane was characterized by SEM, AFM, surface charge density, molecular weight cut-off (MWCO), total and skin thickness and pure water flux. The parameters that affected the rejections of As(III) and As(V) were studied; they included the initial arsenic concentration, the applied potential, pH of the feed, the cross-flow filtration pressure and the presence of different salts in the feed. Among those parameters, the pH of the feed greatly affected As(V) rejection; As(V) ([As(V)]_o = 1000 ppb) rejection was increased from 72.3 to 98.5% when pH of the feed was changed from 3.0 to 10.0. This might be due to the fact that higher pH enhanced the formation of negative divalent anion like HAsO₄²⁻ which should be rejected more effectively by the negative surface charge of the NF membrane. Beside the effect of the negative surface charge of the membrane, applied potential increased the As(V) rejection by 48.2% when the applied potential was increased from 0 to 2.0 V for a feed containing 1000 ppb initially. For the same change of applied potential rejection of As(III) was increased from 52.3 to 70.4%; this might be the result of the formation of anionic species like H₂AsO₃⁻ from the neutral molecule of H₃AsO₃ by the applied potential.     

Modification of Some Hyperbranched Polyols with Oligo (Ethyleneoxide) Units on the Way to New Applications

Three different hyperbranched polymers (H₁, H₂, and H₃) were prepared. The H₁ and H₂ are hyperbranched polyesteramide polymers; however, H₃ is a poly(urea-urethane) hyperbranched polymer. The three polymers were treated with Br-ended surfactant units, which were prepared via simple reaction of Tergitol Np-50 (S) as surfactant with bromoisobutyrylbromide. New ended polymers resulted as H₁S, H₂S, and H₃S with new ethyleneoxide units. Critical micelle concentration (CMC) was studied for the newly prepared polymers (H₁S, H₂S, H₃S) and was compared with the original ones (H₁, H₂, H₃) on the way to involve the new modified polymers in various industrial applications. The CMC was determined by the surface tension technique employing the platinum ring method. It was found that CMC could be arranged in the following ascending order: H₃S < H₂S < H₁S < H₃ < S < H₂ < H₁.