Cationic Hexadecyltrimethylammonium Bromide Research Articles

Comparison of atomic force microscopy and dynamic light scattering on the size characterization of surfactant-modified WC/Co nanoparticles dispersed in aqueous media

Tungsten carbide cobalt nanoparticles (WC/Co NPs) are extensively employed to fabricate wear-resistant parts, cutting tools, and rock drills. The colloidal stability of the WC/Co NP suspension plays a vital role in determining the mechanical properties of WC/Co-based products. In this work, dispersion of WC/Co NPs in aqueous media was conducted using surfactants (cationic, anionic, nonionic) with different concentration conditions. The z-average hydrodynamic diameters measured using dynamic light scattering (DLS) revealed the optimal surfactant for WC/Co NP dispersion: cationic hexadecyltrimethylammonium bromide (CTAB) which induces interparticle electrostatic repulsion forces at a concentration of 2 g/L. The capping behavior of CTAB was demonstrated using Zeta-potential analysis, Fourier transform infrared spectroscopy, and X-ray diffraction measurements. The mean size measurement of immobilized WC/Co NPs was also conducted using atomic force microscopy (AFM). We demonstrate a comparative protocol between number-weighted mean sizes measured using AFM (dAFM) and DLS (dDLS) in relation to the relative standard deviation (RSD) from AFM measurements. A highly linear correlation was demonstrated between dDLS/dAFM and RSD. We indicate that for polydisperse (RSD > 0.1) and non-spherical NPs, the highest correlation between dDLS and dAFM exists when the RSD is 0.37, where dDLS/dAFM is close to 1.

Effects of static magnetic field on the surface tension of surfactant solutions

AbstractThe magnetic field (MF) effects resulting from water or solution treatments are still of significant interest. However, a relatively small number of papers have been published dealing with the pure surfactant solutions alone. On the other hand, surfactants are applied in many industrial processes as well as in everyday life and are also present in different waste waters. Therefore, it seemed interesting to investigate whether some effects would appear after the MF treatment of pure aqueous surfactant solutions. In the earlier published papers after MF action the changes in water evaporation rate and the surface tension were found for both the cationic dodecyltrimethylammonium bromide (DTAB) and anionic sodium dodecyl sulfate (SDS) solutions. The gradient MF originated from three connected ring magnets inside which the solutions were placed. The objective of this paper is to study whether using the same magnets but in a different position the effects of the MF are observed. The given surfactant solution in a closed vessel was placed in an uniform MF when the magnets were in the “lying” position. The investigated solutions on the magnet surface remained for 24 h. In this paper, despite SDS and DTAB also the cationic hexadecyltrimethylammonium bromide (CTAB) and nonionic Triton X‐100 solutions were applied. It appeared that in the uniform MF the surface tension of cationic and anionic surfactant solutions changes. However, larger changes were observed in the gradient MF. Generally, the changes of surface tension depend on the surfactant kind and its concentration. Stronger MF influence was found for the cationic surfactant and almost no changes were observed for nonionic Triton X‐100.

Effects of cationic and anionic surfactants on the stability, rheology and proppant suspension of nanoparticle-stabilized fracturing foams at elevated temperature

Much attention has been paid to applying liquid foams in hydraulic fracturing in the past few years due to their significant benefits, including minimal formation damage. In the current literature, the combination of anionic surfactants and nanoparticles (NP) has been thoroughly studied to improve foam-based fracturing fluids' thermal stability and viscosity. However, very little research has focused on the synergy between cationic surfactants and NP, which results in a limited understanding of the effects of this mixture on enhancing the properties of fracturing foams, especially at reservoir temperature. This paper investigates and compares the synergy between cationic/anionic surfactant and silica nanoparticles (SNP) in improving the fracturing foams' stability, rheology and proppant-carrying capacity under ambient and elevated temperature conditions. The experiments involved foamability, bulk static stability, viscosity measurement and proppant settling tests at fixed NP concentration and varied surfactant concentrations. The results showed that the foams' properties were gradually enhanced with increasing surfactant concentration until reaching a peak at around 0.05–0.1 wt%. At ambient and elevated temperatures, the foams stabilized by SNP and cationic hexadecyltrimethylammonium bromide (CTAB) surfactant had higher half-life, apparent viscosity, and better proppant-carrying ability than those stabilized by SNP and anionic sodium dodecyl benzene sulfonate (SDBS) surfactant. The properties of CTAB/SNP foams were found most outstanding at medium CTAB concentration; however, they declined dramatically at very low or very high surfactant concentration. This study enhances our understanding of the influences of surfactant type and concentration on the stability, rheology and proppant suspension behaviour of nanoparticle-stabilized foams, which directly contributes to developing an effective foam system for high-temperature fracturing application.

Surface complexation model theory application in NaOL and CTAB collector adsorption differences of diaspore and kaolinite flotation

Although the relevant direct and revers flotation mechanism has been discussed a lot in diaspore and kaolinite separation, the quantitative analysis of surface-active sites and their reaction descriptions during flotation have not been reported yet. In this study, the hydration and collector adsorption reactions of anionic sodium oleate (NaOL) and cationic hexadecyl trimethyl ammonium bromide (CTAB) onto diaspore and kaolinite were quantized. Surface complexation model (SCM) was referred to obtain intrinsic reaction equilibrium constants. It can be found that for NaOL adsorption, the equilibrium constant of diaspore (1013.55) was obviously bigger than that of kaolinite (1011.76 and 1010.35 for ≡AlOH and ≡SiOH, respectively), corresponding to direct flotation of bauxite. While the interaction (103.90 for ≡XNR) between the permanent negatively charged site ≡X− and CTAB was much stronger than other sites. Besides, the single adsorbed amount in mixed minerals were successfully predicted at ratios of 1:2, 1:1 and 2:1. Finally, the fitted potential curves were also acceptable to zeta potential tests. These conclusions from SCM calculation can provide strong supports for collector adsorption differences and then help for separation much more efficiently and economically through saving preliminary exploration cost.

Sodium dodecyl sulfate (SDS)-assisted preparation of homogeneous monodisperse MnCO3 microspheres and its application to the synthesis of LiMn2O4

In recent years, there has been increasing interest in the morphological design of lithium manganese oxide (LiMn2O4), but little attention has been paid to the agglomeration and mono-dispersion characteristics of the particles. In the present study, a facile co-precipitation method was used to synthesize manganese carbonate (MnCO3) microspheres. Their effects on the dispersion of microspheres were investigated by introducing three different types of surfactants: anionic sodium dodecyl sulfate (SDS), cationic hexadecyl trimethyl ammonium bromide (CTAB), and nonionic polyethylene glycol (PEG). The extent of MnCO3 dispersion was analyzed by scanning electron microscopy (SEM) and laser particle size analysis. The results demonstrated that the addition of 50 wt% SDS enabled the effective synthesis of homogeneous monodisperse MnCO3 microspheres with superior tap density. Additionally, LiMn2O4 cathode material was synthesized by solid-phase sintering utilizing spherical MnCO3 as the template. Electrochemical tests indicated that the homogeneous monodisperse LiMn2O4 exhibited superior electrochemical performance, with a first-cycle Coulombic efficiency of 92.29% and a specific discharge capacity of 110.73 mAh·g–1 at 5 C and 128.49 mAh·g–1 after 100 cycles at 1 C.

Treatment of polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions by flotation using colloidal gas aphrons

Aqueous solutions contaminated with polycyclic aromatic hydrocarbons (PAHs) pose severe environmental risks, making their removal necessary. Flotation with colloidal gas aphrons (CGAs) has recently demonstrated high removal efficiencies for various pollutants present in aqueous solutions. This study determined the efficacy of CGAs in removing low-ring PAHs (naphthalene, fluorene, and phenanthrene) from aqueous solutions. CGAs were produced from different surfactants, such as anionic sodium dodecylbenzene sulfonate (SDBS), cationic hexadecyl trimethylammonium bromide (HTAB), and natural surfactant obtained from the leaves of Ziziphus spina-christi (ZSC). PAHs removal efficiency was studied by varying different parameters, such as type of surfactant, PAHs solution pH, CGAs flow rate, and PAHs and CGAs solution temperature. Results showed that at pH 5.6 and 25 °C, fluorene and phenanthrene were fully removed using CGAs (flow rate of 100 mL/min) derived from cationic HTAB surfactant, while naphthalene was removed to the extent of approximately 88.4% under similar conditions. These findings suggest that CGAs derived from cationic HTAB surfactant have a greater capacity for extracting low-ring PAHs from aqueous media.

Thermodynamics of the micellization of quaternary based cationic surfactants in triethanolamine-water media: a conductometry study

Abstract The effect of triethanolamine, a solvent with wide technical and industrial benefit on the micellization of an aqueous mixture of cationic surfactants, dodecyltrimethylammonium bromide (DETAB) and hexadecyltrimethylammonium bromide (HATAB) was studied to examining the stability of the mixed micelles at 298.1, 303.1, 308.1 and 313.1 K using the electrical conductance method. The values of the critical micelle concentration (C*) were found to decrease with an increase in the concentration of triethanolamine (TEA). The values of the free energy of micellization (ΔGm) were negative at a particular temperature, and the extent of spontaneity was discovered to increase when the concentration of TEA was increased. However, an increase in temperature was observed to have a negative linear relationship with the spontaneity of the process. The formation of the mixed micelles was an exothermic process, and it was also TEA and temperature-dependent with a trend similar to those observed in the free energy of micellization (ΔGm). The degree of disorderliness of the system was also found to be entropy driven at a higher concentration of TEA. The synergistic interaction between the molecules of DETAB–HATAB in the presence of TEA (0.4% v/v) and the spontaneity of the system was at the maximum at 0.1:0.9 mol fraction ratio and the energetics of the system was discussed based on hydrophobic–solvophobic interaction of the monomers in TEA at elevated temperatures.

Microalgae harvesting using colloidal gas aphrons generated from single and mixed surfactants

Harmful algal blooms (HABs) caused by microalgae are becoming increasingly common and pose serious threats to human health, aquaculture, and marine environments and, therefore, their removal is becoming essential. Colloidal gas aphrons (CGAs), a recent technology adapted in flotation, showed promise in removing several contaminants from aqueous solutions. This study aimed to investigate the potency of CGAs in removing several microalgae strains (Spirulina platensis, Nannochloropsis oculata, and Chlorella vulgaris) from aqueous solutions. Surfactants, including cationic hexadecyl trimethyl ammonium bromide (HTAB), anionic sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and their mixes, were used to prepare stable CGAs. The effect of different environmental parameters like algae concentration, pH, and salinity, on removing Spirulina platensis was thoroughly investigated. Operating conditions, including surfactant type, flotation time, flowrate, and solution temperature, were optimized. At pH 5 and 50 °C, Spirulina platensis, Chlorella vulgaris, and mixed microalgae were fully removed using CGAs produced from cationic HTAB surfactant. About 95% removal of Nannochloropsis oculata was achieved using mixed surfactant CGAs. The results obtained from this work demonstrated the promising potential of CGAs produced from both single and mixed surfactants in harvesting various microalgae from aqueous media.

Effect of pH and surfactants on the electrokinetic properties of nanoparticles dispersions and their application to the PET fibres modification

This paper presents the effect of surfactants, pH and electrolyte (0.1 × 10−3 M KCl) on the stability of the aqueous dispersions of commercial ZnO and AgCu nanoparticles. As the surfactants cationic hexadecyltrimethylammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS), and nonionic 4-(1,1,3,3-tetramethylbutyl)phenyl polyethylene glycol (Triton X-100) at concentrations of 0.5 × 10−3, 1.0 × 10−3, and 0.1 × 10−3 M, respectively, were used. The zeta potential values, z-average hydrodynamic diameter and long-term stability of ZnO and AgCu nanoparticles were examined by means of the dynamic light scattering (DLS) technique. It was found that the presence of ionic surfactants reduced the tendency of nanoparticles for agglomeration/aggregation and improved their colloidal stability. They were characterized by high (>|70| mV) and pH-independent zeta potential values. In addition, ZnO nanoparticles in the presence of ionic surfactants showed a better long-term stability than AgCu nanoparticles. Their z-average hydrodynamic diameters in CTAB and SDS were 195 ± 2 nm and 295 ± 5 nm, respectively, and remained almost unchanged for 5 days. The addition of KCl improved the stability of aqueous and containing nonionic surfactant dispersions of nanoparticles, what was reflected in the zeta potential values > 30 mV in almost the entire pH range. The stability of nanoparticles dispersion significantly affects the uniformity of nanoparticles distribution on the fibres surface. The uniformity of distribution of the ZnO and AgCu dispersion on the surface of polyester (PET) fibres was carried out by means of microscopic methods (SEM/EDS).

Fluorinated silica–modified anti–oil-fouling omniphobic F–SiO2@PES robust membrane for multiple foulants feed in membrane distillation

Direct–contact membrane distillation (DCMD) can be eminent solution for oily wastewater treatment if the membrane provided is slippery and tolerant to low surface tension complex solutions. This study describes preparation of an anti–oil–fouling omniphobic polyethersulfone membrane using fluorinated silica nanoparticles (F–SiO2@PES) combined with perfluorodecyl triethoxysilane and polydimethylsiloxane for application against oil–In–water (o/w) emulsions. Feed solutions consist of different concentrations of oil (hexadecane), different charge surfactants (anionic sodium dodecyl benzenesulfonate, non-ionic Tween 20, and cationic hexadecyltrimethylammonium bromide, and salt (NaCl). The hierarchical re-entrant micro structured surface of the omniphobic F–SiO2@PES membrane and functional groups are confirmed by atomic force microscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The anti–oil-fouling and anti–wetting performance of omniphobic F–SiO2@PES membranes are investigated using contact-angle, sliding angles, DCMD tests with multiple foulants of surfactants. Omniphobic F–SiO2@PES membrane exhibited effective anti–oil–fouling and anti–wetting performance against emulsions as no severe fouling and a conductivity rises were evident regardless of surfactant charge and the concentration of components. Flux reduction and rejection rates for the omniphobic F–SiO2@PES membranes are in a range of 5–15% (only) and >99%, respectively, for various combinations of feed solution components.

Role of surfactants in spontaneous displacement of high viscosity oil droplets from solid surfaces in aqueous solutions

HypothesisDisplacement of oil droplets receding from solid surfaces in aqueous solutions plays a critical role in many household activities and industrial operations. Surfactants are often involved in these activities to control the displacement process. We hypothesize that the influence of surfactants on the displacement process of oil is highly dependent on the type and dosage of surfactants, with the mechanisms being elucidated by the analysis using appropriate dynamic wetting models. ExperimentsWe systematically investigated the spontaneous displacement of a high viscosity oil on curved hydrophilic glass surfaces in aqueous solutions of anionic sodium dodecylbenzene sulfonate, cationic hexadecyl trimethyl ammonium bromide, and nonionic TritonTM X-100 over a wide range of concentrations. FindingsThe rather different oil displacement behaviors were observed with different surfactant additions. The displacement dynamics of the receding oil droplet was found to be inhibited by surfactant additions and followed two distinct models quantitatively: the power-law model describing the temporal evolution of early-stage displacement, and the molecular kinetic model describing the dependence of the three-phase contact line displacement velocity on the dynamic contact angle at the late stage of oil displacement. The model-based data analysis provided insights on the role of surfactants in controlling the oil displacement dynamics.

Surfactant-mediated dispersions of carbon nano-onions in aqueous solution

In this work, we investigate the ability of different surfactants to form homogeneous and stable dispersions of carbon nano-onions (CNOs) in water via non-covalent interactions. For our purposes, we select three ionic surfactants, namely the cationic hexadecyltrimethylammonium bromide (CTAB) and the two anionic deoxycholic acid sodium salt (DCAS) and sodium dodecylbenzenesulfonate (SDBS). We examine the dispersing efficacy at dispersing CNOs and long-term stability by UV–vis absorption spectroscopy, dynamic light scattering and zeta-potential. Among the three surfactants, the anionic surfactants show the best ability to create stable CNO dispersions, with SDBS exhibiting superior efficacy. Our non-covalent strategy provides a valuable approach to enhance the solubility features while preserving the unique properties of CNOs.

Dual-template hydrothermal synthesis of multi-channel porous NiCo2O4 hollow spheres as high-performance electromagnetic wave absorber

Dual-template hydrothermal method was adopted for the synthesis of NiCo2O4 materials. The D-glucose acted as the hard template and the three kinds of soft templates, i.e., nonionic polyvinylpyrrolidone (PVP), anionic sodium dodecyl benzene sulfonate (SDBS) and cationic hexadecyl trimethyl ammonium bromide (CTAB) were selected to synthesize NiCo2O4 materials. We found that the species of the soft templates play significant role in the determination of products’ morphologies. Flower-like, flower-like spherical and multi-channel porous hollow spheres structured NiCo2O4 could be obtained by utilization of PVP, CTAB and SDBS, respectively. When employed as the electromagnetic (EM) wave absorbers, the multi-channel porous NiCo2O4 hollow spheres possessed the best EM wave absorption performance. The reflection loss (RL) value lower than −10 dB was up to 5.44 GHz and could be achieved at thin thickness of 1.8 mm. The minimum RL value corresponding to this thickness reached to −31.1 dB as well. The outstanding EM wave absorption performance was ascribed to the unique multi-channel porous hollow spheres structure, which could provide abundant interfaces between absorbers-air thus promoting the interfacial polarization. Additionally, the multiple reflections and scattering, dipole polarization and eddy current loss conjointly accounted for the superior attenuation behavior. The facile synthetic route and the high EM wave absorption performance of multi-channel porous NiCo2O4 hollow spheres may offer a novel strategy for the preparation of high-performance ferrite EM wave absorbers.

Study of mechanical properties of alkaline earth hydroxide nanoconsolidants for lime mortars

This research intends to study and optimize successful preparative strategies of nano to sub-micro limes, and to improve their efficiency in the inhibition of the degradation process and in the consolidation of wall renders. In this article we report the synthesis and characterization of nanoparticles based on alkali-earth metal hydroxides, precisely calcium and magnesium hydroxides nanoparticles (Ca(OH)2 and Mg(OH)2) dispersed in ethanol and 2-propanol, for cultural heritage restoration. We discuss the tests conducted to assess the mechanical properties’ alteration of lime mortar specimens treated with these nanolimes (superficial hardness, dynamic elastic modulus, compressive and flexural mechanical behaviour). Particularly, the influence of the dispersions’ concentration, number of applications (layers) and the slope of the treated surface during the dispersions application on the mechanical properties has been studied. The treatment with nanolime resulted in an improvement of the mechanical properties of the treated specimens. This effect is proportional to the number of layers applied and to the concentration of the alcohol dispersion applied. We also report our attempt to achieve better particles morphology by the addition of surfactants: the non-ionic t-octylphenoxypolyethoxyethanol (Triton X-100) in the synthesis of Ca(OH)2 and the cationic hexadecyltrimethylammonium bromide (CTAB) in the synthesis of Mg(OH)2.

Surfactant specific ionic strength effects on membrane fouling during produced water treatment

Membrane filtration is a technique that can be successfully applied to remove oil from stable oil-in-water emulsions. This is especially interesting for the re-use of produced water (PW), a water stream stemming from the petrochemical industry, which contains dispersed oil, surface-active components and often has a high ionic strength. Due to the complexity of this emulsion, membrane fouling by produced water is more severe and less understood than membrane fouling by more simple oil-in-water emulsions. In this work, we study the relation between surfactant type and the effect of the ionic strength on membrane filtration of an artificial produced water emulsion. As surfactants, we use anionic sodium dodecyl sulphate (SDS), cationic hexadecyltrimethylammonium bromide (CTAB), nonionic Triton TMX-100 (TX) and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS), at various ionic strengths (1, 10, 100 mM NaCl). Filtration experiments on a regenerated cellulose ultrafiltration (UF) membrane showed a pronounced effect of the ionic strength for the charged surfactants SDS and CTAB, although the nature of the effect was quite different. For anionic SDS, an increasing ionic strength leads to less droplet-droplet repulsion, allowing a denser cake layer to form, resulting in a much more pronounced flux decline. CTAB, on the other hand leads to a lower interfacial tension than observed for SDS, and thus more deformable oil droplets. At high ionic strength, increased surfactant adsorption leads to such a low oil-water surface tension that the oil droplets can permeate through the much smaller membrane pores. For the nonionic surfactant TX, no clear effect of the ionic strength was observed, but the flux decline is very high compared to the other surfactants. For the zwitterionic surfactant DDAPS, the flux decline was found to be very low and even decreased with increasing ionic strength, suggesting that membrane fouling decreases with increasing ionic strength. Especially promising is that at lower surfactant concentration (0.1 CMC) and high ionic strength no flux decline was observed, while a high oil retention (85%) was obtained.From our results, it becomes clear that the type of the surfactant used is crucial for a successful application of membrane filtration for PW treatment, especially at high ionic strengths. In addition, they point out that the application of zwitterionic surfactants can be highly beneficial for PW treatment with membranes.

Molecular simulation study on the rheological properties of a pH-responsive clean fracturing fluid system

The rheological properties of a pH-sensitive clean fracturing fluid system formed by the anionic surfactant N-hexadecyl iminodiacetic acid (HIA), which has two carboxyl groups, and salt-free cationic hexadecyl trimethyl ammonium bromide (CTAB) have been carefully studied. Viscoelastic wormlike micelles (WLMs) were prepared in a HIA/CTAB hybrid system. The increased electrostatic interactions between the heads of HIA and CTAB lead to a structural transition from spheres to WLMs as a function of pH. Large-scale coarse-grained molecular dynamics (CGMD) revealed that the formation of WLMs can be described in three stages: “oligomer-to-sphere” fusion; “sphere-to-rod” fusion; and “'rod-to-rod” fusion. The simulation results show that electrostatic repulsion occurs among the carboxyl groups of HIA and that HIA is screened by the positively charged heads of CTAB, which leads to an increase in solution viscosity. The excellent rheological properties and pH sensitivity of the clean fracturing fluid significantly improve the seaming capacity and reservoir protection of the fracturing fluid, thus helping to increase the productivity of the well after fracturing and control the construction cost.

Separation and enrichment of micro and nano sized particles from aqueous solutions by flotation using colloidal gas aphrons

The aim of this work was to investigate the separation and enrichment of micro and nano sized particles by batch and column flotation using colloidal gas aphrons (CGAs). The CGAs were produced using anionic sodium dodecylbenzenesulfonate (SDBS) and cationic hexadecyltrimethylammonium bromide (HTAB) surfactants. The physical properties of the surfactant solutions, formation of CGAs, liquid drainage from the foam as well as liquid rise and bubble size of CGAs were measured. In the batch process, carbon particles showed that the CGAs produced with HTAB enhanced the performance of separation ratio 1.45 and enrichment ratio 1.14. The % removal of carbon was found to be 77% for 100 μm particles while it was 82% using 45 μm particles. By using SDBS, 91% removal was achieved for 400 mg/L concentrated iron particles having size 500 nm. In the column flotation, the % removal of carbon particles was 54% while it was 42% for iron particles. Thus, CGAs generated from anionic SDBS and cationic HTAB surfactants were proved to be effective in separating micro and nano sized particles based on electrostatic interactions.

Quantifying Double-Layer Potentials at Liquid-Gas Interfaces from Vibrational Sum-Frequency Generation.

Vibrational sum-frequency generation (SFG) spectroscopy is demonstrated as a fast method to quantify variations of the electric double-layer potential ϕ0 at liquid–gas interfaces. For this, mixed solutions of nonionic tetraethyleneglycol-monodecylether (C10E4) and cationic hexadecyltrimethylammonium bromide (C16TAB) surfactants were investigated using SFG spectroscopy and a thin-film pressure balance (TFPB). Derjaguin–Landau–Verwey–Overbeek analysis of disjoining pressure isotherms obtained with the TFPB technique provides complementary information on ϕ0, which we apply to validate the results from SFG spectroscopy. By using a single ϕ0 value, we can disentangle χ(2) and χ(3) contributions to the O–H stretching modes of interfacial water molecules in the SFG spectra. Having established the latter, we show that unknown double-layer potentials at the liquid–gas interface from solutions with different C16TAB/C10E4 mixing ratios can be obtained from an analysis of SFG spectra and are in excellent agreement with the complementary results from the TFPB technique.

Kinetics and thermodynamic of reaction of oxydiacetate copper(II) complex with 2,2′-bipyridine and 1,10-phenanthroline in anionic and cationic surfactant solutions

The oxydiacetate complexes of copper(II) with 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen) have been investigated towards their kinetic and thermodynamic stability. The kinetics of the substitution reactions of the oxydiacetate complex of Cu2+ with bipy and phen have been studied in two types of surfactant solutions - anionic dodecyl sulfate sodium (SDS) and cationic hexadecyl trimethyl-ammonium bromide (CTAB). The values of the observable rate constants for the studied reactions have been determined using the “Glint” program. Moreover, the thermodynamic stability of the copper(II) complexes with oda, phen and bipy in aqueous solutions has been investigated using potentiometric titration method (PT). The concentration distributions of the studied complexes as a function of pH calculated based on the values of log βpqrs have been determined. Additionally, the antioxidant activities of the oxydiacetate complexes of copper(II) with bipy and phen have been studied by the nitro blue tetrazolium (NBT) test and the cyclic voltammetry (CV) technique.

Enhanced foamability and foam stability of polyoxyethylene cholesteryl ether in occurrence of ionic surfactants

The micellization and foam studies of binary surfactant mixtures assembled of nonionic polyoxyethylene cholesteryl ether (ChEOn; where n = 30), cationic hexadecyltrimethylammonium bromide (CTAB) and anionic sodium dodecylbenzenesulfonate (SDBS) was investigated by surface tension, foaming behavior and viscosity measurements. As an exceptional outcome it was observed that foam stability and foamability of nonionic surfactant ChEO30 in mixtures with ionic surfactants is much superior to the individual ChEO30, CTAB or SDBS components. Moreover, the mixed surfactant systems (ChEO30+CTAB) and (ChEO30+SDBS) have much lower critical micellar concentrations (CMCs) than corresponding sole surfactants. The negative values of interaction parameter (β) estimated from Rubingh’s theory specify synergism amongst mixed ChEO30+CTAB and ChEO30+SDBS surfactants systems.