Surfactant Concentration Research Articles

Emulsion liquid membrane technique for optimal separation of Ni (II) and Sm (III) using response surface methodology and Box–Behnken experimental setup

ABSTRACT This study evaluated the reliability of the emulsified liquid membrane (ELM) extraction technique for recovering and separating metals, focusing on Nickel (Ni(II)) and Samarium (Sm(III)), both used in electrochemical devices. Key contributions include determining optimal conditions for creating a stable water-in-oil (W/O) emulsion. The optimal conditions were found to be a 5-minute emulsification time, 4 wt.% Span 80 surfactant concentration, a 1.6 volume ratio of the internal phase to the organic phase, 1 M H2SO4 concentration for the internal phase, a 40/160 volume ratio of the emulsion to the external phase, and kerosene as the diluent. Factors affecting the separation of Ni(II) and Sm(III) included the concentrations of the internal aqueous phase, surfactant, and extractant. Under these conditions, an equimolar mixture of Ni(II) and Sm(III) was extracted within 15 min. The study emphasized the importance of phase volume ratio and surfactant concentration for emulsion stability and extraction efficiency. The response surface method (RSM) and Box–Behnken design were used to optimize influential factors, with a modified quadratic model predicting extraction yields of 83.81% for Sm(III) and 15% for Ni(II). The study demonstrates that effective separation of Ni(II) and Sm(III) ions is achievable using this technique, providing valuable insights into efficient and selective metal ion extraction, contributing to the broader field of metal recovery and recycling technologies.

HSPiP and QbD oriented optimized stearylamine-elastic liposomes for topical delivery of ketoconazole to treat deep seated fungal infections: In vitro and ex vivo evaluations

The study explored stearylamine containing cationic elastic liposomes to improve topical delivery and efficacy of ketoconazole (KETO) to treat deeply seated fungal infections. Stearylamine was used for dual functionalities (electrostatic interaction and flexibility in lipid bilayer). Hansen solubility program (HSPiP) estimated Hansen solubility parameters (HSP) based on the SMILE file and structural properties followed by experimental solubility study to validate the predicted values. Various formulations were developed by varying phosphatidylcholine and surfactants (tween 80 and span 80) concentration. To impart cationic properties, stearylamine (1.0 %) was added into the organic phase. Using quality by design (QbD) method, we optimized the formulations and evaluated for vesicle size, polydispersity index, zeta potential, morphology (scanning electron microscopy), in vitro drug release (%), and ex vivo permeation profiles. Result showed that there is a good correlation (0.65) between HSPiP predicted and actual experimental solubility of KETO in water, chloroform, S80, and tween 80. Spherical OKEL1 showed an established correlation between the predicted and the actual formulation parameters (size, zeta potential, and polydispersity index) (259 nm vs 270 nm, +2.4 vs 0.21 mV, and 0.24 vs 0.27). OKEL1 was associated with the highest value of %EE (83.1 %) as compared to liposomes. Finally, OKEL1 exhibited the highest % cumulative permeation (49.9 %) as compared to DS (13 %) and liposomes (25 %). Moreover, OKEL1 resulted in 4-fold increase in permeation flux as compared to DS which may be attributed to vesicular mediated improved permeation and gel based compensated trans epidermal water loss in the skin. The drug deposition elicited OKEL1 and OKEL1-gel as suitable carriers for maximum therapeutic benefit to treat deeply seated fungal infections.

Effect of Surfactants on Eliminating Stable Ultrafine Chalcopyrite Froth.

Chalcopyrite is a primary source of copper in nature. However, with the increasing need to process low-grade and complex chalcopyrite ores, overly stable froth is becoming more and more common and poses operational and safety challenges. No reliable strategy has been developed to address the issue. As a new initiative, this study investigated three different structured surfactants, sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and pentadecafluorooctanoic acid (PFOA), which vary in hydrophobic group, aiming to modify the surfaces of ultrafine chalcopyrite particles and adjust the interfacial tension at the gas-liquid interface to eliminate stable ultrafine chalcopyrite froth. The fundamental hypothesis was that an ideal surfactant structure could adjust the particle surface wettability and interfacial tension to eliminate overly stable froth. Based on contact angle measurements and interfacial tension measurements using a Theta Flow tensiometer by the pendant drop method and the sessile drop method, it was demonstrated that the contact angle played a dominant role in defoaming, while the reduction of gas-liquid interfacial tension had an adverse effect. Additionally, defoaming tests indicated that SDBS had lower defoaming effectiveness than SDS at low surfactant concentrations due to the steric hindrance in its structure, whereas the addition of SDBS could achieve a froth reduction efficiency as high as 93.75% at higher surfactant concentrations due to its stronger hydrophobicity and adsorption capacity to chalcopyrite particles, which could reduce the contact angle from 70 to 37.62°. However, PFOA exhibited lower defoaming effectiveness than both SDS and SDBS due to its lipophobic fluorocarbon tail of PFOA and weaker adsorption capacity to chalcopyrite particles, making it unsuitable for eliminating stable ultrafine chalcopyrite froth.

A numerical model for the simulation of complex planar Newtonian interfaces

We present a numerical model for the simulation of complex planar interfaces at which moving solid objects can be immersed, reproducing a wide variety of experimental conditions. The mathematical model consists of the Navier-Stokes equations governing the incompressible viscous flow in the liquid subphase, the transport equation for the evolution of the surfactant concentration at the interface, and the interfacial stress balance equation. The equations are simplified by treating the problem as isothermal and the surfactant as insoluble. The bulk flow equations are discretized using a collocated finite volume method, while the interfacial flow equations are discretized using a finite area method. The Boussinesq-Scriven interface constitutive model and a variant form accounting for extensional viscosity are used to describe the extra surface stress tensor. The coupling between surfactant concentration, interfacial velocity, and bulk velocity is treated implicitly by solving the interfacial and bulk equations sequentially at each time step until a stopping criterion is satisfied. The motion of the solid is treated by an arbitrary Lagrangian-Eulerian method. The model has been implemented in the OpenFOAM framework and allows the incorporation of new interface models and solvers, making the developed new package a versatile and powerful tool in the field of computational rheology. Applications of the model include the numerical simulation of flow around objects, such as probes, immersed at a complex interface, reproducing given experimental conditions, and its use as a tool in the analysis and design of interfacial stress rheometers. Several test cases have been performed to validate the model by comparing the results obtained with analytical solutions and with numerical and experimental results available in the literature.

Substrates with Tunable Hydrophobicity for Optimal Cell Adhesion.

Electrospinning is a technique used to create nano/micro-fibrous materials from various polymers for biomedical uses. Polymers like polycaprolactone (PCL) are commonly used, but their hydrophobic properties can limit their applications. To enhance hydrophilicity, nonionic surfactants such as sorbitane monooleate (Span80) and poloxamer (P188) can be added to the PCL electrospinning solution without altering its net charge density. These additions enable the successful production of PCL/P188 and PCL/Span80 fibrous substrates. In this study, P188 and Span80 are incorporated into the PCL solutions; they are successfully electrospun into PCL/P188 and PCL/Span80 substrates, respectively. PCL/P188 substrates show that until a specific P188 concentration, fiber and pore sizes are similar to PCL substrates. However, exceeding 0.30% P188 concentration enlarges fibers, impacting fiber uniformity at higher concentrations. Conversely, higher concentrations of Span80 result in thicker, less uniform fibers, indicating potential disruptions in the electrospinning process. Notably, both surfactants significantly improve substrate hydrophilicity, enhancing the adhesion and proliferation of fibroblasts, endothelial cells, and smooth muscle cells. P188, in particular, shows superior efficacy in promoting cell adhesion and growth at concentrations optimized for different cell types. Therefore, precise surfactant concentrations in the electrospinning solution can lead to the optimization of electrospun substrates for tissue engineering applications.

Self-assembly of mixed surfactants sodium dodecylsulfate and polyethylene glycol dodecyl ether in aqueous solutions

The thermodynamic behavior of mixed systems containing the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant polyethylene glycol dodecyl ether (Brij L4) in aqueous solutions was investigated. Electrical conductivity and interfacial tension measurements were employed to investigate the concentration-dependent properties of these surfactant mixtures. Two main experiments were conducted: i) constant ratio experiment: the overall surfactant concentration was varied while maintaining a fixed ratio between SDS and Brij L4. It was shown that the critical micelle concentration (CMC) determined from electrical conductivity measurements does not indicate the formation of the first mixed micelles as observed using tensiometry, but the point from which the adsorption of counterions by the existing micelles became important. By using the Regular Solution Theory (RST), it was found that the interaction between SDS and Brij L4 is synergistic, driven by dipole-ion interactions of the hydrophilic regions of the two surfactants. ii) Fixed SDS concentration while increase the Brij L4 concentration: the resulting electrical conductivity exhibited non-trivial behavior which complexity arose from simultaneous phenomena of incorporation of free SDS molecules into the micelles as Brij L4 concentration increased, leading to a decrease in electrical conductivity; liberation of some adsorbed counterions from the mixed micelles to the solution, which increases the conductivity and increase of viscosity due to Brij L4 further addition that leads to a sequential decrease in electrical conductivity.

Physiological impact of perfluorooctanoic acid (PFOA) on the cyanobacterium Microcystis aeruginosa

ABSTRACT Perfluorooctanoic acid (PFOA) is a surfactant that is detected in small quantities across various environments away from its manufacturing zones. Despite the widespread detection of PFOA in aquatic ecosystems, the impact of this compound on phytoplankton populations remains poorly understood. This study aimed to determine the physiological effects of PFOA on Microcystis aeruginosa. The cyanobacterium was exposed to 1‒10 000 μg l‒1 PFOA for 7 days under controlled laboratory conditions. The EC50 of PFOA for the test species after 7 days of exposure was 30.03 μg l‒1. Cell density significantly decreased at all PFOA concentrations (1‒10 000 μg l‒1). Chlorophyll a and carotenoid concentrations increased on day 1 (except for 1 μg l‒1, the lowest PFOA treatment) but then decreased across all treatment concentrations on day 7 of the experiment. When M. aeruginosa was exposed to PFOA, the total lipid, protein and carbohydrate content generally increased across all treatment concentrations. The concentration of intracellular hydrogen peroxide increased with increasing surfactant concentrations. In different treatments, lipid peroxidation increased, with 100 μg l‒1 PFOA producing the highest malondialdehyde content. Peroxidase and glutathione S-transferase activities increased across all treatment concentrations, demonstrating progressive changes consistent with the increase in reactive oxygen species observed. Total microcystin concentration increased in cultures exposed to 1000 and 10 000 µg l‒1 PFOA. These findings suggest that PFOA can adversely affect the survival of M. aeruginosa populations in contaminated aquatic ecosystems, with potential cascading effects on the general health of the environment.

Emulsion liquid membrane pertraction of soap from crude biodiesel using activated carbon and glycol based deep eutectic solvents

Soap removal from crude biodiesel is considered as one of the most challenging biorefinery processes. This study reports a new technique for soap removal incorporating activated carbon (AC) in an emulsion liquid membrane (ELM) system based on deep eutectic solvents (DES-AC-ELM). These DESs were prepared from two salts, namely tetramethylammonium chloride (TMAC) and choline chloride (ChCl), with different hydrogen bond donors (HBDs) such as ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG). COSMO-RS modelling was performed in the evaluation of the activity coefficients and capacity at infinite dilution of DESs. The COSMO-RS simulation shows that the DESs with TEG as the HBD are the most effective stripping agents for soap removal which is in accordance with the experimental results. In addition, the σ-profile and σ-potential were used to investigate the interactions between the soap molecules in each phase. The impact of various process parameters on the soap removal such as the salt: HBD ratio, DES:biodiesel ratio, span-20 concentration, mixing speed, extraction time and dosage of AC were evaluated. The proposed technique achieved a soap extraction efficiency of 99.1% (6.856 ppm) and 97.5% (18.773 ppm) for TMAC:TEG(DES3) and ChCl:TEG(DES6), respectively, with a salt: HBD molar ratio of 1:4, DES:biodiesel ratio of 1:1, 2 wt% surfactant concentration, 10 min extraction duration, 400 rpm mixing speed, 0.5 treatment ratio and 0.5 wt% AC dosage. The transport mechanism of soap conforms to a first-order mass transfer behaviour, with a kinetic rate constant of 0.64 min−1 and 0.43 min−1, for DES3 and DES6, respectively. This study illustrated a new cleaner and simple route for purification of crude biodiesel.

A Study of Micellar Catalyses on Oxidation of Glycine by QDC in the Presence of Sodium Dodecyl Sulphate (SDS) in Aqueous Perchloric Acid Medium

Aims: To study the micellar effect of SDS on the oxidation of glycine by Quinolinium Dichromate (QDC) in perchloric acid medium. Background: Among the amino acids, glycine plays a major role in multiple metabolic reactions, such as glutathione synthesis and one-carbon metabolism. The oxidation of glycine has received importance because it is the major neurotransmitter inhibitor in the spinal cord and brainstem. In the oxidation process of amino acids, highly toxic chromium (VI) compounds are converted into non-toxic chromium (III) by quinolinium dichromate (QDC) oxidant in an appropriate pH value medium. Objective: 1. To study the catalytic role of anionic surfactant (SDS) on the oxidation of glycine by QDC through micellization, evaluation of critical micelles concentration (CMC) in the presence and absence of glycine and other surface properties along with thermodynamic quantities. 2. Determination of rate constant and order of reaction with respect to QDC, glycine, acid and surfactant which will help to study the kinetics of the reaction 3. Analysis of oxidation product by FT-IR and calculation of activation parameters. 4. Synthesis of oxidant (QDC) and its characterization by UV-Visible spectrophotometer and NMR spectroscopy. Results: First-order kinetics was observed with respect to oxidant, glycine and hydrogen ions. The rate of reaction increased remarkably with an increase in the concentration of surfactant (SDS). The kinetic results show that the ionic strength variation does not have any significant effect on the rate whereas the increase in the dielectric constant of the medium shows a remarkable effect on the rate constant. From stoichiometry study, it was found that 2 moles of oxidant (QDC) consumed 3 moles of glycine to produce aldehyde (Formaldehyde). Conclusion: The observed negative value of (ΔS) entropy of activation and positive (ΔH) enthalpy of activation suggests a more ordered activated complex formation and highly solvated transition state. The kinetics of the reaction in a perchloric acid medium is found to be accelerated in the presence of surfactant (SDS). The kinetics of the reaction follow pseudo first-order decay of Cr(VI) species (QDC), a unity dependence of rate on glycine and perchloric acid. The oxidation product formaldehyde was identified by FTIR. NMR spectrum analysis of synthesized QDC shows a resemblance with pure QDC.

Phytochemical screening, antioxidant, anti-diabetic, and anti-obesity activities, formulation, and characterization of a self-nanoemulsion system loaded with pomegranate (Punica granatum) seed oil

Pomegranate (Punica granatum) is a tree of the Punicaceae family that is widespread all over the world and has several types and therapeutic uses. The current study aimed to investigate the phytochemical compounds by GC analysis and carried out physical characterization of the pomegranate seed oil and its self-nanoemulsifying system. Then antioxidant, anti-diabetic, and anti-lipase activities were investigated for both.The pomegranate seed oil was extracted, and its self-nanoemulsifying system was then prepared. Phytochemical compounds were analyzed by GC, and physical characterization was established of the pomegranate seed oil and its self-nanoemulsifying system. Then antioxidant, anti-diabetic, and anti-lipase activities were investigated for both.The GC–MS analysis revealed that punicic acid, β-eleosteric acid, catalpic acid, α-eleosteric acid, and oleic acid were the most predominant compounds in pomegranate seed oil. Other active compounds like linoleic acid, palmitic acid, stearic acid, and α-linolenic acid were detected in trace percentages. The self-nanoemulsifying system was prepared using various concentrations of surfactant (Tween 80), co-surfactant (Span 80), and pomegranate seed oil. The selected formulation had a PDI of 0.229 ± 0.09 and a droplet size of 189.44 ± 2.1 nm. The free radical scavenging activity of pomegranate seed oil, the self-emulsifying system, and Trolox was conducted using DPPH. The oil-self-nanoemulsifying system showed potent antioxidant activity compared to Trolox. Also, pomegranate oil inhibited α-amylase with a weak IC50 value of 354.81 ± 2.3 µg/ml. The oil self-nanoemulsifying system showed potent activity compared to acarbose and had a weaker IC50 value (616.59 ± 2.1 µg/ml) and a potent IC50 value (43.65 ± 1.9 µg/ml) compared to orlistat.Pomegranate seed oil self-nanoemulsifying system could be applied in the future for the preparation of possible oral medications for the prevention and treatment of oxidative stress, diabetes, and obesity due to its high activity against free radical, amylase, and lipase enzymes compared to pomegranate seed oil itself and the references used. This study reveals that self-nanoemulsion systems can enhance oil drug formulations by improving pharmacokinetics and pharmacodynamics, acting as drug reservoirs, and facilitating efficient oil release.

Surfactant-enhanced mobilization of polycyclic aromatic hydrocarbons from an historically contaminated marine sediment: Study of surfactants’ concentration effect and continuous test for sediment flushing simulation

Contamination of marine sediments by polycyclic aromatic hydrocarbons (PAHs) poses a significant environmental threat, necessitating effective remediation strategies. This paper investigates the application of surfactants, both synthetic and natural, for the remediation of PAH-contaminated sediments, providing a systematic guideline for the preliminary selection of surfactants for flushing/washing operations, the optimal operative conditions, and the technical approach for PAH mobilization, especially in the context of a real aged contamination scenario. The study included a batch configuration test to evaluate the effect of surfactant concentration on PAH mobilization. Subsequently, a continuous configuration column experiment was performed to simulate a flushing operation of contaminated sediment. The study of process conditions highlighted that the increase in surfactant concentration led to a significant increase in PAH removal from the sediment, reaching almost 30 % efficiency using a 5 % wt surfactant solution. The column test showed great efficiency of the investigated surfactants in PAH mobilization through the flushing process of the contaminated matrix, resulting in 30 times greater efficiency than water within a much smaller pore volume range.

Green fabrication and efficiency of activated biochar-layered double hydroxide (LDH) nanocomposites against toxic Pink-XFG dye

Removal of dyes has been a matter of great interest for researchers because of health and toxicity issues. In this research work, green biochar was produced using precipitation technique, and by the adsorption process, it was supported on layered double hydroxide (LDH). Biochar/LDH composites were synthesized from Neem, Amaltas, and Keekar stems, eggshells, and Eucalyptus (N, A, K, Egg, and Eu’s biochar/LDH-composite). These composites were employed to remove synthetic dyes from an aqueous solution. Recent studies have identified optimal conditions for LDH-composites under various parameters: pH 9 or 10 with a dosage of 0.05 g/50 mL yields higher adsorption capacities across different LDH composites, ranging from 40.74 to 48.30 mg/g at a reaction time of 90 min using a Pink-XFG dye concentration of 10 ppm, which is favorable. Temperatures of 303–308 K are suitable. Second-order kinetics, along with the Langmuir and Freundlich adsorption isotherms, along with exothermic reactions, presented good-fit results on adsorption kinetics and equilibrium data. The adsorption potential was significantly affected by various concentrations of electrolytes, surfactants, detergents, and heavy metal ions. 0.5 N hydrochloric acid was determined to be the most efficient agent for the process of desorption. These methods are very cost-effective, eco-friendly, and easy to manufacture.

Thermoresponsiveness Across the Physiologically Accessible Range: Effect of Surfactant, Cross-Linker, and Initiator Content on Size, Structure, and Transition Temperature of Poly(N-isopropylmethacrylamide) Microgels.

The influence of surfactant, cross-linker, and initiator on the final structure and thermoresponse of poly(N-isopropylmethacrylamide) (pNIPMAM) microgels was evaluated. The goals were to control particle size (into the nanorange) and transition temperature (across the physiologically accessible range). The concentration of the reactants used in the synthesis was varied, except for the monomer, which was kept constant. The thermoresponsive suspensions formed were characterized by dynamic light scattering, small-angle X-ray scattering, atomic force microscopy, and rheology. Increasing surfactant, sodium dodecyl sulfate content, produced smaller microgels, as expected, into the nanorange and with greater internal entanglement, but with no change in phase transition temperature (LCST), which is contrary to previous reports. Increasing cross-linker, N,N-methylenebis acrylamide, content had no impact on particle size but reduced particle deformability and, again contrary to previous reports of decreases, progressively increased the LCST from 39 to 46 °C. The unusual LCST trends were confirmed using different rheological techniques. Initiator, potassium persulfate, content was found to weakly influence the outcomes. An optimized content was identified that provides functional nanogels in the 100 nm (swollen) size range with controlled LCST, just above physiological temperature. The study contributes chemistry-derived design rules for thermally responsive colloidal particles with physiologically accessible LCST for a variety of biomedical and soft robotics applications.

Thin-film flow due to an asymmetric distribution of surface tension and applications to surfactant deposition

Thin-film equations are utilised in many different areas of fluid dynamics when there exists a direction in which the aspect ratio can be considered small. We consider thin free films with Marangoni effects in the extensional flow regime, where velocity gradients occur predominantly along the film. In practice, because of the local deposition of surfactants or input of energy, asymmetric distributions of surfactants or surface tension more generally, are possible. Such examples include the surface of bubbles and the rupture of thin films. In this study, we consider the asymmetric thin-film equations for extensional flow with Marangoni effects. Concentrating on the case of small Reynolds number $ Re $ , we study the deposition of insoluble surfactants on one side of a liquid sheet otherwise at rest and the resulting thinning and rupture of the sheet. The analogous problem with a uniformly thinning liquid sheet is also considered. In addition, the centreline deformation is discussed. In particular, we show analytically that if the surface tension isotherm $\sigma = \sigma (\varGamma )$ is nonlinear (surface tension $\sigma$ varies with surfactant concentration $\varGamma$ ), then accounting for top–bottom asymmetry leads to slower (faster) thinning and pinching if $\sigma = \sigma (\varGamma )$ is convex (concave). The analytical progress reported in this paper allows us to discuss the production of satellite drops from rupture via Marangoni effects, which, if relevant to surface bubbles, would be an aerosol production mechanism that is distinct from jet drops and film drops.

Artificial neural networks-based modelling of effects of cryogenic electrode treatment, nano-powder, and surfactant-mixed dielectrics on wear performance and dimensional errors on superalloy machining

In the present era dominated by Industry 4.0, the digital transformation and intelligent management of industrial systems is significantly important to enhance efficiency, quality, and the effective use of resources. This underscores the need for a framework that goes beyond merely boosting productivity and work quality, aiming for a net-zero impact from industrial activities. This research introduces a comprehensive and adaptable analytical framework intended to bridge existing gaps in research and technology within the manufacturing sector. It encompasses the essential stages of using artificial intelligence (AI) for modelling and optimizing manufacturing systems. The effectiveness of the proposed AI framework is evaluated through a case study on electric discharge machining (EDM), concentrating on optimizing the electrode wear rate (EWR) and overcut (OC) for aerospace alloy Inconel 617. Utilizing a comprehensive design of experiments, the process modelling through an artificial neural network (ANN) is carried out, accompanied by careful fine-tuning of hyperparameters throughout the training process. The trained models are further assessed using an external validation (Valext) dataset. The results of the sensitivity analysis indicated that the surfactant concentration (Sc) has the highest level of influence, accounting for 52.41% of the observed influence on the EWR, followed by the powder concentration (Cp) with a contribution of 33.14%, and the treatment variable with a contribution of 14.43%. Regarding OC, Sc holds the highest percentage significance at 72.67%, followed by Cp at 21.25%, and treatment at 6.06%. Additionally, parametric optimization (PO) shows that EWR and OC overcome experimental data by 47.05% and 85.00%, respectively, showcasing successful performance optimization with potential applications across diverse manufacturing systems.

Enhanced removal of toxic Disperse Blue 35 dye through cloud point extraction: influence of parameters and solvent regeneration

Abstract The release of the dye Disperse Blue 35 (DB35) into water has serious environmental and health consequences, due to its toxicity and resistance to degradation. This paper investigates the effectiveness of cloud point extraction (CPE) to remove this industrial dye from aqueous solution by Lutensol AO7 and Triton X-114, two environmentally friendly nonionic surfactants. First, the partial phase diagrams of the water–surfactant binary systems are constructed. Then, the effects of pollutants, sodium sulfate and cetyltrimethylammonium bromide on the cloud point temperature (T c) are determined. The experimental results are expressed by four responses: Extraction efficiency (E), residual concentrations of solute and surfactant in the dilute phase (X s,w and X t,w, respectively) and the volume fraction of coacervate (Ф c). An empirical smoothing method was applied. For each parameter, the results obtained were modeled using the response surface methodology (RSM) and represented on three-dimensional diagrams. The results show that the efficiency of dye extraction with Lutensol AO7 and Triton X-114 at a concentration of 6 wt% is about 95 % and 82 %, respectively. The influence of salt and ionic surfactant on the effectiveness of CPE for the removal of DB 35 dye was determined. The regeneration of surfactant was only achieved by pH adjustment.

Comparison of Machine Learning Approaches for Prediction of the Equivalent Alkane Carbon Number for Microemulsions Based on Molecular Properties.

The chemical properties of oils are vital in the design of microemulsion systems. The hydrophilic-lipophilic difference equation used to predict microemulsions' phase behavior expresses the oils' physiochemical properties as the equivalent alkane carbon number (EACN). The experimental determination of EACN requires knowledge of the temperature dependence of the microemulsion system and the effects of different surfactant concentrations. Thus, the experimental determination is time-intensive and tedious, requiring days to months for proper separations. Furthermore, the experiments require high purity of chemicals because microemulsions are sensitive to impurities. Our work focuses on the quick and reliable predictions of the EACN with machine learning (ML) models. Due to the immaturity of ML chemical predictions, we compare three graph neural networks (GNNs) and a gradient-boosted tree algorithm, known as XGBoost. The GNNs use the molecular structures represented as simplified molecular-input line-entry system (SMILES) codes for the initial input, which allows us to assess whether geometry optimization is necessary for reliable results. The XGBoost model also begins with the SMILES representations of the molecules but uses molecular descriptors instead of geometry optimizations. The best model tested (crystal graph convolutional neural network with Merck molecular force field-94) has an error of 1.15 EACN units of the true EACN for unknown data with the errors skewed toward zero and an R2 score of 0.9.

Association in Like-Charged Surfactant-Nanoparticle Systems: Interfacial and Bulk Effects.

The association of similarly charged surfactant molecules and nanoparticles in an aqueous solution remains unresolved, and the understandings reported in the literature are conflicting. To address this issue, we undertake a fundamental study to investigate bulk and interfacial phenomena in binary mixtures of (i) positively charged nanoparticles and cationic surfactants and (ii) negatively charged nanoparticles and anionic surfactants. We find that the surfactant molecules adsorb on the surface of the nanoparticle despite similar charge, leading to supercharging of particles and simultaneously driving more surfactant molecules to the air-dispersion interface. Hence, the properties of the dispersed species, such as the size and zeta potential, and the interfacial properties, such as the surface tension and surface excess concentration, change significantly. This effect is more pronounced at a low surfactant concentration and is observed irrespective of the size of nanoparticles and surfactant-particle combination. Further, we elucidate the important role of electrostatic interactions in the surfactant-particle complexation process by varying the pH of the dispersions. Contrary to changes in the properties of the dispersed species and interface, the presence of particles does not appreciably change the bulk property, such as the critical micelle concentration.

Investigation of micellization and thermodynamic properties of cationic gemini surfactant (12-2-O-2-12) in the presence of organic solvents

The micellization behaviour and thermodynamic properties of synthesized cationic gemini surfactant (12-2-O-12-12), N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-(oxybis(ethane-2,1-diyl))-diammonium dibromide were studied in the presence of organic solvents for four different temperatures (25, 30, 35 and 40 °C). Aqueous solutions of 10 % and 20 % methanol (MeOH), ethanol (EtOH), isopropanol (IPOH) and dimethyl sulfoxide (DMSO) were used as solvents. The critical micelle concentration (CMC) of cationic gemini surfactant and the degree of counterion dissociation (α) were determined by the conductometric method. Using the CMC and α values for each of the four temperatures, the values of the standard Gibbs free energy (ΔGmo), Gibbs free energy of transfer (ΔGm,transo), enthalpy (ΔHmo), and entropy (ΔSmo) of micellization were calculated. It was observed that the CMC and α values increased with increasing solvent percentage and temperature. It was found that in all cases, the standard Gibbs free energy and enthalpy values were negative while both the micellization entropy and the standard Gibbs free energy of transfer are positive. Negative Gibbs free energy values indicated that micellization was a spontaneous situation, while positive entropy values indicated the existence of a disordered situation. The positive ΔGm,transo values show that the presence of solvents makes the environment unfavorable for micelle formation.

A novel approach to produced water management using surfactants for water-wise energy production

Evaporation can become a prominent solution for management of the large volumes of contaminated water produced each year in the energy industry. However, improvements to the evaporation rates are needed which can be accomplished through the use of surfactants. In this paper, organic and inorganic compounds commonly found in produced water were studied in a controlled, laboratory oven to understand their effect on water evaporation rate. Organic compounds were classified in three ways: as either miscible or immiscible, as having a density less than or greater than water for immiscible compounds, and by their volatility. For each sample, the evaporation rate and surface tension were measured, and correlations were made between the two. As the cationic charges of salts added to water increased from +1 to +3, the evaporation rates decreased and the surface tension increased. Monovalent cationic charges were 60% higher than solutions containing divalent or trivalent cations. From the organic compounds tested, the addition of surfactants to deionized water increased evaporation rates by more than 50% while the addition of immiscible organic compounds hindered these rates. Surfactants reduced the surface tension of these samples thus positively affecting the evaporation rates. Applying surfactants to basic salt solutions showed evaporation rates increased with the greatest being that of sodium chloride, the most common salt in produced water. Increases in salt concentrations lowered evaporation rates and increased surface tension while increases in surfactant concentrations did not necessarily continue to reduce surface tension and increase evaporation rates. When surfactants were added to produced water samples, up to a 27% increase in the rates of evaporation were observed. The quality of produced water varies from region to region and therefore some surfactants may have a greater effect in one type of water than another.