Higher Surfactant Concentrations Research Articles

The lamellar MOFs@polymer networks hybrids fabricated in reversed microemulsion for efficient CO2 capture

AbstractZIF‐8@polymer networks hybrids (ZIF‐8@PNs), consisting of the flexible CO2 responsive polymer and rigid ZIF‐8 crystals, were fabricated using DMAPMA as the monomer and BIS as the cross‐linker by the reversed microemulsion polymerization, and characterized by the powder XRD, SEM, TEM, DLS, FT‐IR, and TGA. Monomers and cross‐linkers were initiated by AIBN to form polymer networks which coated ZIF‐8 crystals. The shape of ZIF‐8@PNs was modulated by the micelles of surfactant in the reversed microemulsion. In particular, the lamellar ZIF‐8@PNs hybrids with the regular thickness of 50–70 nm in which ZIF‐8 crystals were wrapped by the flexible polymer networks and still retained the crystal skeleton, were fabricated at the high concentration of surfactant in the reversed microemulsion. Additionally, the adsorption capacity of ZIF‐8@PNs hybrids for CO2 has been evaluated. Under the higher initial pressure at the lower temperature, the adsorption of ZIF‐8@PNs for CO2 was higher than that of the pure ZIF‐8, and was an increasing of 180%. The adsorption kinetic models of ZIF‐8@PNs for CO2 indicated that CO2 was efficiently captured in the pores of ZIF‐8 in the internal and the flexible polymer networks on the surface of ZIF‐8@PNs. Moreover, ZIF‐8@PNs had good regeneration of CO2 adsorption, and remained more than 90% after 6 cycles.

β‐Cyclodextrin‐based macroporous monoliths: One‐pot oil‐in‐oil emulsion templating and adsorption

AbstractThe ability of β‐cyclodextrin (β‐CD) to form a host–guest complex with relatively hydrophobic molecules such as bisphenol A (BPA), a common wastewater contaminant, has inspired the development of β‐CD‐containing polymers for adsorption applications. For the most part, these polymers are powders, which can limit their applicability. Here, low‐density (~0.1 g cm−3), macroporous monoliths based on unmodified β‐CD were synthesized using emulsion templating. The relatively simple, one‐pot, polyurethane synthesis took place within the external phase of oil‐in‐oil (o/o) high internal phase emulsions (HIPEs) that contained β‐CD and a diisocyanate. The combination of o/o emulsions and a polyurethane reaction enabled the incorporation of relatively high β‐CD contents (up to 63 wt%) and limited the occurrence of the water–isocyanate urea reaction. The resulting open‐cell porous structures varied from an average pore size of 5.0 μm (lower surfactant content) to the typical structure associated with polyHIPEs (higher surfactant content), voids of ~50 μm and interconnecting holes ranging from submicrometer to ~2 μm. The compressive mechanical behaviors of the easily handled monoliths were similar to those of flexible foams, reaching strains of 70% without failure. The BPA adsorption capacities, up to 117.7 mg g−1, may make these monoliths advantageous for adsorption applications.

Potential of ceramic ultrafiltration membranes for the treatment of anionic surfactants in laundry wastewater for greywater reuse

Decentralized greywater treatment is gaining increasing recognition as an alternative for natural water supplies. Laundry wastewater in relatively large amounts of greywater is considered as a valuable resource with high reuse potential. However, organic pollutants with low molecular weights (e.g., anionic surfactants) that originate from laundry additives should be effectively removed. Because anionic surfactants are widely used to produce detergents, the retention of sodium dodecylbenzene sulphonate (SDBS; a typical anionic surfactant in laundry wastewater) was evaluated with a bench-scale ceramic ultrafiltration (UF) membrane filtration system. The results demonstrate that SDBS can be successfully retained with a ceramic UF membrane with a nominal pore size of 1 kDa (~4.0 nm) by carefully controlling several operating parameters. The dynamic phase changes of the surfactant that depend on its concentration affect the SDBS retention performances regardless of the operating parameters. At a high transmembrane pressure (TMP) and room temperature, the SDBS micelles that form on the membrane surface cause a pre-sieving effect induced by concentration polarization, thereby increasing the SDBS retention. As the solution pH increased, electrostatic repulsion between the solute and membrane surface induced higher SDBS retention rates. The retention rate also increased significantly with increasing ionic strength, which was especially pronounced with divalent ions than with monovalent ions because higher ion specificity could reduce the charge repulsion and induce their micellization. These electrostatic and adsorptive interaction could demonstrate a better understanding of surfactant retention mechanisms. Consequently, ceramic UF membranes have the potential of treating laundry wastewater attaining moderately high concentrations of surfactants.

Synthesis, cytotoxicity assay, pharmacokinetics, biodistribution and modeling study of cabazitaxel-dextran nanoconjugates: targeted vs non targeted delivery

Cabazitaxel (CTX) is an anti-neoplastic agent of second-generation taxane derivatives, characterized by very low water solubility. The currently marketed formulation of CTX contains high concentrations of surfactant and ethanol, which causes severe hypersensitivity reactions in patients. To deal with aforementioned side effects, our previous study attempted to develop the prodrugs of CTX with dextran. Here our approach differs through synthesizing folate containing prodrug and also investigating cytotoxicity and pharmacokinetics parameters obtained with dextran and dextran-folate nanoconjugates versus free CTX. MCF-7 with medium folate receptor expression and MDA-MB-231 as high folate receptor expression cell lines were selected for cytotoxicity assay. Pharmacokinetics properties were studied by injecting prodrugs and CTX to Wistar rats, analyzing serum and selected tissue samples and the obtained results were sibjected to data modeling study. The size of synthesized prodrugs was mostly less than 90 nm. Folate conjugates provided higher toxicity in comparison with dextran conjugates on both cell lines. In vivo non-compartmental pharmacokinetics analysis revealed enhanced area under the curve (about 3–5 fold for different samples) and longer half-life (approximately 1.3–1.8 fold higher) which led to increased serum residence time of prodrugs in comparison to free CTX. Tissue accumulation data showed that liver was the major organ with high accumulation of CTX. The accumulation of folate conjugates was remarkably higher than dextran samples (p < 0.05 in samples of 2, 10 and 24 h). Data modeling by Principal Component Analysis (PCA) and Hierarchical Cluster models showed a significant difference between pharmacokinetics properties of CTX and prodrugs. In summary, prodrugs seem to be proper and promising CTX delivery systems as substitution for the current market formulation.

Research on morphological control and temperature regulation of phase change microcapsules with binary cores for electronics thermal management

Phase change materials (PCM) has become one of the research hotspots for electronics thermal management owing to its high latent heat, low cost, simple structure, and other merits. In this study, a novel PCM with encapsulating binary paraffin cores and calcium carbonate shell has been proposed, the morphological control and temperature regulation strategies are investigated in detail. The apparent morphologies of resultant microcapsules could be controlled from spherical to spindle ones by comparatively high surfactant concentrations and reaction temperature. The DSC tests indicated the phase change temperature could be optionally adjusted within 20∼48 °C by the binary core ratio, phase change enthalpy can reach 103 J/g. TEM results showed the achieved microcapsules with typical core-shell structure about 1∼6 μm. In addition, the thermal conductive performance was greatly improved of 2.25∼2.63 times compared to the pristine paraffin, the main reason was not only the spindle morphology with superior heat transfer area but also the presence of conductive calcium carbonated shell. It should be noted that the microcapsules-graphene hybrid film developed by this work exhibited great thermal conductivity enhancement along with the appropriate temperature regulation and micro-size, exhibiting excellent prospect in the electronics thermal management and other energy storage fields.

A newly synthesized ionic liquid as an effective corrosion inhibitor for carbon steel in HCl medium: A combined experimental and computational studies

Surfactants present exciting adsorption chemistry due to their dual nature, i.e the present of the hydrophobic and hydrophilic parts in their structures. However, the inhibition performance of surfactants is influenced by their chemical structure as well as the nature of the electrolyte. In acidic media, high concentration of tri-cationic surfactants is required for effective surface protection. Herein, we report the synthesis of a novel tri-cationic surfactant containing three quaternized nitrogen atoms and its corrosion inhibitive effect for carbon steel in 1 M aqueous HCl medium. The molecular structure of the surfactant was elucidated by 1H NMR and 13C NMR spectroscopic techniques and its anti-corrosion activity was investigated by electrochemical impedance spectroscopy, potentiodynamic polarization and dynamic electrochemical impedance spectroscopy methods. The results obtained from the corrosion studies show that the synthesized surfactant is quite effective against the low carbon steel corrosion and at low inhibitor concentration. The inhibition efficiency obtained at 5 mg/L concentration is above 90%, showing that the anti-corrosion effect of the synthesized surfactant on the metal surface is strong even at low inhibitor concentration. Moreover, some physicochemical parameters namely, the critical micelle concentration, surface tension, micelle formation free energy, and emulsion stability have been calculated and used to explain the correlation with the corrosion inhibition mechanism. Additionally, to support the results from the electrochemical measurements, surface morphological examination using energy dispersive X-ray spectroscopy (EDAX) and scanning electron microscope (SEM) methods have been performed. The EDAX and SEM results prove the adsorption of the tri-cationic surfactant molecule on the metal surface. The adsorption followed the Langmuir adsorption isotherm and calculated Kads (equilibrium constant of the adsorption process) value reflects strong interaction. More so, density functional theory (DFT) results corroborate the experimental results. The synthesized tri-cationic surfactant is a potential candidate for the formulation of acid corrosion inhibitor for acid cleaning applications.

Foamability of surfactant solutions: Interplay between adsorption and hydrodynamic conditions

The foamability of surfactant solutions depends strongly on the adsorption properties of the surfactants, their concentrations, and the foaming test used for foam generation. The aim of the current study is to analyse the subtle interplay between the hydrodynamic conditions and the surfactant adsorption layers formed during foaming. We compare the results from three foam tests, characterized with very different hydrodynamic conditions. The Bartsch test (fast-foaming method) is characterized by a very short time, of the order of milliseconds, allowed for surfactant adsorption before the newly generated bubbles collide with each other. The other two “slow-foaming” tests, the planetary mixer and the foam rise method, are very different from this viewpoint – the characteristic time for surfactant adsorption before the bubble collisions is much longer, of the order of seconds. Surfactants of two different types, nonionic and anionic, with different chain-lengths are compared. The obtained results reveal that the long-chain nonionic surfactants with 16 carbon atoms are unable to stabilize the foams in the fast-foaming test, even at very high surfactant concentrations (50 mM), due to their relatively slow adsorption. Interestingly, the same surfactants are excellent foam stabilizers in the slow-foaming tests. On the other hand, the medium-chain anionic surfactants with 12 carbon atoms are very suitable for stabilization of the gas bubbles in the fast-foaming test, even at relatively low concentrations, due to their rapid adsorption and inherent electrostatic repulsion. In slow-foaming tests, however, the anionic surfactants show lower foamability to the nonionic ones. All results from the foam tests are explained in a unified approach which accounts explicitly for the rate of surfactant adsorption and for the characteristic time-scales of the various foaming tests.

Investigation of the Kinetic Regularities of the Process of Biodegradation of Betaine Surfactant by Bacteria of the Genus Pseudomonas

Surfactants are extremely common organic compounds that enter the environment in large quantities in the form of household and industrial wastewater. The toxicity of surfactants for biological systems, the high concentration of substances and the duration of the bioremediation process of polluted ecosystems requires improving the biotechnology of microbial wastewater treatment for surfactants. The purpose of this work is to study the kinetic laws of the reaction of the biological decomposition of betaine surfactants. Pseudomonas bacteria were used as bio-destructors of the surfactants. Kinetic data were obtained to create the possibility of further optimization of research on the biodegradation of toxic organic substances. The strains that were promising destructors of cocamidopropylbetaine were selected. The toxicity of high concentrations of surfactants in relation to microorganisms of the genus Pseudomonas was proven. Safe values of the surfactant concentration for conducting biodegradation tests were found. A kinetic model of the biodestructive process was constructed. It proves that the processes of biodegradation are described by a kinetic equation of the first order. With the derived equation, it is possible to determine the time interval of biodegradation of cocamidopropylbetaine to the specified values by means of mathematical calculations.

Influence of surfactant contaminations on the lift force of ellipsoidal bubbles in water

The shear-induced lift force is known to influence the lateral distribution of gas bubbles in bubbly flows. Although the hydrodynamic behavior of a bubble can be greatly affected by surfactants that are present in the liquid bulk, their influence on the lift force has only been investigated to a limited extent. In our previous work we investigated the influence of impurities on the lift force in air-water flows and could reveal non-negligible changes even without a modification of the bubble drag or shape. To bring further insight on changes caused by higher surfactant concentrations, the lift coefficient of single ellipsoidal bubbles of different sizes, which rise in water with varying degree of contamination are experimentally determined in this work. For this purpose, different amounts of 1-Pentanol as well as Triton X-100 were added to the flow. The results reveal a strong dependency of the lift coefficient on the bubble shape, where different findings in the literature for bubbles with lower Reynolds numbers could also be observed for ellipsoidal bubbles in water.

Management and kinetics of methane production from anaerobic batch reactors treating PET bottle washing wastewater

The study evaluated the methanogenic potential of anaerobic sludge in Wastewater from the Washing of PET (Polyethylene terephthalate) bottles sent for Recycling (WWPR). The bioreactors were inoculated with sludge from an upflow anaerobic sludge blanket reactor treating poultry waste. The operation occurred under anaerobic conditions at 35 °C and 150 rpm for three bioreactors in triplicate with the initial COD concentration of 2000 mg L−1 (C1), 5000 mg L−1 (C2), and 10,000 mg L−1 (C3). The inhibition in the anaerobic biological treatment caused by high surfactant concentration impaired the wastewater biodegradation. COD removals were 67.8 ± 0.4% (C1), 67.6 ± 2.7% (C2), and 59.1 ± 2.9% (C3), indicating a process inhibition in the latter condition. The modified Gompertz model indicated a cumulative methane production of 290 mL for condition C1 with an adjustment coefficient of 99.11%. The methane potential for the production of electricity revealed a maximum annual production of 188,292 MWh. Annual thermal energy from condition C1 could produce 1.01 × 108 PET bottles. Therefore, the anaerobic treatment of WWPR is an alternative to wastewater management, avoiding greenhouse gases emission and potentiating the generation of electrical and thermal energy.

Effect of Surfactants on the Molecular Structure of the Buried Oil/Water Interface.

The oil/water interface, for instance in emulsions, is often stabilized by surfactants. Hence, the co‐existence of oil, water, and surfactant molecules at the buried oil/water interface determines macroscopic properties such as surface tension or emulsion stability. Utilizing an inherently surface sensitive spectroscopic method, sum frequency generation (SFG) spectroscopy, we show that adsorption of an anionic surfactant to the buried oil/water interface increases the magnitude of the interfacial electric field. Meanwhile, the degree of ordering of the interfacial oil molecules increases with the surfactant concentration owing to the intercalation of aliphatic chains of interfacial oil and surfactant molecules. At sufficiently high surfactant concentrations, the interfacial charge reaches a maximum value and the interfacial oil molecules arrange in a fully ordered conformation, a state which coincides with the significant decrease in interfacial tension and increased emulsion stability.

Probing the Effect of Wettability on Transport Behavior of Foam for Enhanced Oil Recovery in a Carbonate Reservoir

Foam for enhanced oil recovery in carbonate reservoirs is generally challenging because the oil-wet formation is not favorable for generating and stabilizing the lamellae. With an alkyl-polyglucoside surfactant, a series of foam core flooding experiments both in the absence and in the presence of crude oil were performed on Estaillades limestone, a dual porosity and heterogeneous carbonate presenting reasonable similarities with the reservoir formation. The effects of wettability, surfactant concentration, and foam quality on foam strength were systematically investigated. It is found that the foam strength in the presence of oil is generally smaller than that in the absence of oil, and the foam strength in the oil-wet condition is typically lower than that in the water-wet condition. However, for the water-wet condition, the foam strength can be greatly improved by increasing the surfactant concentration, which is getting closer to that in the absence of crude oil at a sufficiently high surfactant concentration. The combined effect of a high remaining oil saturation and the disadvantageous wettability can further destabilize foam, thereby greatly reducing the foam strength at oil-wet conditions. As a result, the foam flooding under the water-wet condition outperforms that at the oil-wet condition. Furthermore, it is found that the foam behavior at a high gas fraction is more sensitive to the wettability of rock and the foam hysteresis effect.

Supersaturation and Solubilization upon In Vitro Digestion of Fenofibrate Type I Lipid Formulations: Effect of Droplet Size, Surfactant Concentration and Lipid Type.

Lipid-based formulations (LBF) enhance oral drug absorption by promoting drug solubilization and supersaturation. The aim of the study was to determine the effect of the lipid carrier type, drop size and surfactant concentration on the rate of fenofibrate release in a bicarbonate-based in vitro digestion model. The effect of the lipid carrier was studied by preparing type I LBF with drop size ≈ 2 µm, based on medium-chain triglycerides (MCT), sunflower oil (SFO), coconut oil (CNO) and cocoa butter (CB). The drop size and surfactant concentration effects were assessed by studying MCT and SFO-based formulations with a drop size between 400 nm and 14 µm and surfactant concentrations of 1 or 10%. A filtration through a 200 nm filter followed by HPLC analysis was used to determine the aqueous fenofibrate, whereas lipid digestion was followed by gas chromatography. Shorter-chain triglycerides were key in promoting a faster drug release. The fenofibrate release from long-chain triglyceride formulations (SFO, CNO and CB) was governed by solubilization and was enhanced at a smaller droplet size and higher surfactant concentration. In contrast, supersaturation was observed after the digestion of MCT emulsions. In this case, a smaller drop size and higher surfactant had negative effects: lower peak fenofibrate concentrations and a faster onset of precipitation were observed. The study provides new mechanistic insights on drug solubilization and supersaturation after LBF digestion, and may support the development of new in silico prediction models.

Aqueous solution thickening of amino acid‐based surfactant by alkylpyrrolidone

AbstractThe thickening behaviors in aqueous solution of mixed surfactant mixtures containing an amino acid‐based surfactant, sodium lauroyl sarcosinate (SLSar), and a nonionic surfactant, N‐dodecylpyrrolidone (C12P) were investigated using the rheological methods of steady‐shear and frequency sweep. The results varying the added C12P concentration and the mass ratio of SLSar and C12P indicate that the addition of C12P can promote the formation of wormlike micelles and hydrogels, resulting in viscosity enhancement in the mixed aqueous solution of SLSar and C12P. Viscosity maxima in SLSar/water/C12P systems are sensitive to pH, temperature, the concentration of added C12P, and the mass ratio of SLSar and C12P. In the high concentration of total surfactant (30–39 wt%), the enhancement of viscosity obviously occurs by adding 6 wt% C12P, whereas in the low concentration of total surfactant (15 wt%), the C12P must be added more than 9 wt% in 15 wt% mixtures of SLSar and C12P. Moreover, during the solution pH lowered from SLSar' natural pH of 7.2 to the mixture's pKa 5.2, the intermolecular forces between SLSar acid, SLSar anionic salt, and C12P gradually reduce the overall headgroups areas and contribute to the formation of wormlike micelles, hydrogels, and the thickening behaviors.

Molecular insight into the reversible dispersion and aggregation of graphene utilizing photo-responsive surfactants

Reversible dispersion and aggregation of graphene with photo-stimuli response have exhibited enormous potential in electrochemical and biomedical fields owing to its green and efficient characteristics. However, the molecular mechanism of photo-controllable dispersibility of graphene is still limited. Herein, the reversible dispersion and aggregation of graphene in the existence of photo-responsive surfactant (2-(4-(4-butylphenyl)diazenylphenoxy) ethyltrimethylammonium bromide, AzoTAB) is investigated by molecular dynamics simulation. Analysis of structural features indicates that the adsorption configurations of trans-AzoTAB and cis-AzoTAB show different evolutions with increasing concentration. At high surfactant concentrations, exceed trans-AzoTAB molecules move away from the graphene surface and generate second adsorption layer, while cis-AzoTAB molecules prefer to lift a benzene ring to obtain an “L-shaped” configuration, which responsible for the larger saturated adsorption capacity of cis-AzoTAB molecules. Subsequently, the potential of mean force (PMF) provides comprehensive direct evidence for the influence of adsorption configurations on the dispersibility of graphene. It is observed that the transition between the π-π stacking structure formed by three trans-AzoTAB layers and the “L-shaped” configuration of cis-AzoTAB molecules can achieve the reversible dispersion and aggregation processes of graphene. Thus, the photoisomerization of AzoTAB triggered by exposure to UV/visible light could be utilized to realize reversible dispersion and aggregation of graphene.

The effect of C12E6 nonionic surfactant on the solubilization of Eosin Y in unmodified- and hydrophobically modified poly(Acrylic acid) solutions

The effect of the hexaethylene glycol mono-dodecyl ether (C12E6) on the solubilization of Eosin Yellow (2,4,5,7-tetrabromofluorescein, disodium salt) in 0.1 % wt. solution of unmodified and hydrophobically modified poly(acrylic acid) (PAA) was investigated by steady-state and dynamic fluorescence. To this end, firstly the poly(acrylic acid) was hydrophobically modified with 3 % mol and, respectively, 10 % mol linear C16 alkyl chain graft. The behavior of the obtained polymers and that of the parent one in the appropriate solvents were investigated by several methods. It was revealed that the grafts associated with the formation of intra-coil hydrophobic nano-domains and that the polyacrylic acids had lower viscosity than their sodium polyacrylates counterparts, although the c*s were almost similar. The effect of C12E6 nonionic surfactant on 0.1 % wt. polymers solution was also investigated. In water, the addition of C12E6 to polyacid solution leaded to the decrease of the critical aggregation concentration (CAC or T1). On the contrary, in the water–ethanol mixture the interaction was delayed, thus the CAC increased. At the addition of Eosin Y to the surfactant or surfactant-polymer solutions, the dye interacted with each species present in the system, no matter the solvent was. It was also shown that, at higher surfactant concentration, the dye solubilized into bound or free micelles. Therefore, it was considered the nonionic surfactant helped the anionic dye Eosin Y to be incorporated in poly(acrylic acid) based polymers.

A modified premix method for the emulsification of spearmint essential oil (Mentha spicata) by ceramic membranes

A versatile and innovative membrane emulsification system that utilizes a modified premix method was investigated for preparing oil/water emulsions from spearmint essential oil. The modified method (forced-air premix, FAP) is based on flowing air in parallel to the surface of the ceramic membrane at the permeate side, and it was compared to a traditional premix method (conventional premix, CVP) in which pressure was applied only to the feed stream. The influence of membrane pore size, transmembrane pressure, and airflow velocity on the oil emulsion properties was evaluated. In the FAP method, the air stream forces the early shearing and detachment of oil droplets right after the premix permeates the membrane. The results showed that the increase in the operating pressure resulted in the reduction of droplet size and span values for all membranes and methods evaluated. The higher surfactant concentration and presence of forced airflow influenced the reduction of the droplet size and dispersion of emulsions in the FAP method. Stable emulsions were obtained which 28 days of storage.

Molecular investigation on the desorption process of alkane contaminant from fused silica surface in nonionic surfactant solution

In this article, the molecular level investigation on the detachment process of the alkane contaminant from the fused silica surface in nonionic surfactant solution is performed by using molecular dynamics simulation. Three important cleaning parameters including surfactant molecule structure, temperature and surfactant concentration are discussed. We found that the hydrophilic tail of the nonionic surfactant molecule plays a leading role in the desorption process of the oil droplet. The activated chemical activity in surfactant solution with the increasing temperature of solution facilitates the desorption of alkane contaminant. The critical surfactant concentration is vital for cleaning in a real situation. High surfactant concentration can facilitate the desorption of oil droplet in a static solution. The efficiency of water flooding decrease, when the concentration of surfactant is high. Our study can help to understand the cleaning mechanism in surfactant solution and is important for its application in industrial cleaning.

Formation and stability of oil‐laden foam: Effect of surfactant and hydrocarbon solvent

AbstractOil‐laden (OL) foams could serve an important role in various processes, particularly in enhanced oil recovery; however, OL foams are less studied than aqueous foams. In this work, the formation and stability of OL foam, by either sodium dodecyl sulphate (SDS) or Triton X‐100 (TX‐100) in water‐pentane mixture, was evaluated. We first constructed a diagram of good and poor foaminess against pentane content in the mixture and aqueous surfactant concentration. It was shown that surfactant onset concentration for good foaming was increased with increasing pentane content. The result was fitted using a mathematical model that considers the surfactant dilution and adsorption effects by pentane. Foam height decay profiles were also monitored. Results indicated that SDS resulted in a more stable foam than TX‐100 at the same critical micelle concentration (CMC). Depending on surfactant concentration, OL foams exhibited strikingly different stability behaviours. Pentane acted as an anti‐foamer at surfactant concentrations at the CMC or lower. However, very high foam stability was displayed at high surfactant concentration (e.g., 3× CMC) and medium to high pentane contents; this is a result contradictory to the predication of entering, spreading, and bridging coefficients in the classic theory. The stable OL foams of this study could be attractive to potential foam applications.

Transport of an Eco-friendly L70-c Bio-based Sucrose Ester Surfactant: Implication for Soil Remediation Purposes

Due to their biodegradability and low toxicity bio-based surfactants are very promising for use in remediation technologies, particularly for hydrocarbon contaminated soils. To enhance the application of surfactant-based technologies for remediation of organic contaminated sites, it is important to have a better understanding of the surfactant transport and retention mechanisms involved in this process, as they will impact the remediation efficiency. In this work, transport and retention mechanisms of an industrial bio-based nonionic sucrose ester surfactant were investigated through batch and column experiments, carried out on sandy porous media under saturated steady state flow conditions. Column transport experiments were conducted at surfactant concentrations ranged from 1 to 10 CMC (critical micellar concentration), for two distinct Darcy flow rates (0.35 and 0.70 cm.min-1). Surfactant transport and retention parameters were estimated by fitting a convection-diffusion transport model (implemented on HYDRUS-1D code) to the observed transport breakthrough curves, in order to provide an adequate description and understanding of the mechanisms involved in the transport and adsorption of these compounds through porous media. The results obtained from column experiments performed under high flow rate combined with high surfactant concentration provided the best conditions for high surfactant recovery in the effluent and low surfactant adsorption rate onto the sand. Numerical HYDRUS-1D simulations permitted to quantify surfactant transport behavior and provided attachment coefficients several order of magnitude greater than detachment coefficients, indicating that surfactant retention was an irreversible process.