Tetradecyltrimethylammonium Bromide Research Articles

Enhanced heat stability and storage modulus in novel PTMO-intercalated clay platelets/PTMO-based polyurethane nanocomposites

Amine-telechelic poly(tetramethylene oxide) (PTMO) was trimethylated to a quaternary ammonium (QA)-capped PTMO as a bivalent organic macrocation. This QA-capped PTMO (QAPTMO) was used for intercalation of montmorillonite (MMT) platelets with 69 % ion exchange yield and 4.03 nm d-spacing. Then, segmented polyurethanes (SPU) with PTMO soft segments were synthesized in the presence of the QAPTMO-intercalated MMT filler in different contents. According to the X-ray and SEM analyses, the polyaddition reaction could result in a full exfoliation of the clay platelets. Two model composites including SPU polymer loaded by unmodified MMT and tetradecyltrimethylammonium bromide (TTAB)-intercalated MMT were also synthesized analogously. The SPU/QAPTMO-MMT composites possessing 5.0 and 7.0 wt.% of the filler obviously showed a better thermal behavior in comparison with SPU/TTAB-MMT and SPU/Na-MMT composites. In addition, a significant increase in the storage moduli of the polyurethane matrices occurred due to the QAPTMO-MMT particles, particularly in the 5.0 wt.% loading content of the filler.

Influence of octanohydroxamic acid on the association behavior of cationic surfactants: Hydrolytic cleavage of phosphate ester

The surface properties and mixed micellization behavior of cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DTAB) with octanohydroxamic acid (OHA) have been investigated by means of conductivity and surface tension measurements in aqueous solution and borate buffer at 300K. The critical micelle concentration (cmc), surface properties such as maximum surface access (Γmax), surface pressure at the cmc (Πcmc) and minimum surface area per molecule (Amin) has been determined. The standard Gibbs free energy of micellization (ΔGm0), standard Gibbs free energy of adsorption (ΔGad0), and standard Gibbs free energy of micellization per alkyl chain (ΔGm,tail0) of cationic surfactant with OHA have been evaluated. The fluorescence quenching technique was used to estimate the aggregation number (Nagg) and packing parameter (P) for determining the structural feature of cationic surfactants in the presence of octanohydroxamic acid. The hydrolytic reaction of paraoxon with octanohydroxamic acid was studied under a cationic micellar system by using OHA− at 9.2pH and 300K. The variations of surface properties from aqueous medium to the reaction condition have also been discussed. Pseudophase model (PPM) has been fitted for the quantitative treatment of the data.

Extraction of ultratrace amounts of nelfinavir from biological samples and pharmaceutical formulations using surfactant-modified magnetite nanoparticles followed by spectrophotometric determination

A new sensitive, selective, rapid, and simple magnetic solid phase extraction (MSPE)/spectrophotometry method was proposed for extraction and determination of nelfinavir in biological samples and pharmaceutical formulations using tetradecyltrimethylammonium bromide (TTAB)-coated Fe3O4 nanoparticles (Fe3O4 NPs) as an efficient adsorbent. The synthesized Fe3O4 NPs were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Fourier transform infrared (FT-IR) spectrometry was used for confirmation of TTAB-coated Fe3O4 NPs. The influence of various parameters affecting the extraction of nelfinavir has been investigated. The maximum extraction efficiency for extraction of 100.0μg nelfinavir from aqueous solution was obtained with 18.6mg Fe3O4 NPs and 9mg TTAB at pH=9. The analyte was desorbed by 2.5mL acetonitrile (AN) prior to the absorbance measurement. Under optimized conditions, quantitative extraction recoveries of nelfinavir were observed with the sample volumes up to 600mL and hence an enrichment factor of 240 was obtained. This method was so rapid and complete recovery was obtained in 5s. By applying this method for determination of nelfinavir in sample volume of 600mL, the calibration curve was linear in the range of 15.4–500μgL−1 (r2=0.994) and the detection limit was obtained 0.83μgL−1. Also, the relative standard deviations (RSD) for determination of 100.0 and 300.0μgL−1 of nelfinavir were 1.20% and 2.4% (n=7), respectively. This method was successfully applied for determination of nelfinavir in serum samples, urine samples, and pharmaceutical formulations. The recoveries of spiked serum and urine samples were between 98.7% and 102.4%. All the obtained results are indicative of a convenient, fast, and economic method for extraction and determination of nelfinavir from biological samples and pharmaceutical formulations.

Effect of electron density on the catalysts for copolymerization of propylene oxide and CO2

Copolymerization of propylene oxide and carbon dioxide (CO2) has been studied using different R-salophenCoOBzF5 (OBzF5 = pentaflorobenzoate, R = CH3, H, Cl, Cl2) based catalysts. The central moiety of the catalysts R-salophenCoOBzF5 has been kept the same and effect of the catalyst electron density on the copolymerization reaction has been studied. It has been observed that introduction of an electron withdrawing group (like Cl, Cl2) on the o-phenylenediamine backbone moiety of the catalyst makes it more selective for poly(propylene carbonate) synthesis. On the other hand, introduction of an electron donating group (like CH3) makes the catalyst selective for cyclic carbonate conversion. The effect of different type of co-catalysts has also been investigated using tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, [PPN]+Cl− ([PPN]+ = bis(triphenylphosphine)iminium), DMAP and tetrabutyl ammonium bromide.

Effect of 1-ethyl-3-methylimidazolium bromide on interfacial and aggregation behavior of mixed cationic and anionic surfactants

Aggregation behavior and interaction of sodium dodecyl sulfate (SDS), tetradecyl trimethyl ammonium bromide (TTAB) and their mixtures with an excess of anionic surfactant in the presence of imidazolium-based ionic liquid, 1-ethyl-3-methylimidazolium bromide (EMIm Br) were investigated using surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscopy (TEM) and cyclic voltammetry measurements. Different physicochemical properties such as critical micelle concentration (CMC), degree of counterion dissociation (αdiss), interfacial properties, the standard Gibbs energy of adsorption and the size of aggregates were determined. The effects of ionic liquid (IL) as additive on the interactions between the surfactants; TTAB, SDS and their mixtures were analyzed on the basis of regular solution theory, both for mixed monolayers at the air/liquid interface (βδ) and for mixed micelles (βM). Interaction parameter values suggested that the formation of aggregates is due to the synergistic interactions in the case of SDS/TTAB systems and becomes more affected by adding IL. It was shown that an excess of cationic surfactant and IL resulted in an increase in the nano-aggregate sizes. The synergism observed for three component systems (surfactant–water–IL) revealed the effect of attractive electrostatic interaction, formation of a three-dimensional hydrogen bond network and hydrophobic forces on mixed micelle formation.

Kinetics, isotherm, and thermodynamic studies of the adsorption of reactive red 195 A dye from water by modified Switchgrass Biochar adsorbent

A method is described for efficient decolorization of reactive red 195 A dye (RR-195A) from aqueous and wastewater samples using modified Switchgrass Biochar (SB) by tetradecyltrimethyl ammonium bromide (TTAB) as a cationic surfactant for the formation of a novel SB-TTAB adsorbent. The different controlling experimental conditions such as solution pH, initial dye concentration, contact time, adsorbent mass, interfering ions and temperature have been investigated and optimized. Adsorption equilibrium using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models have been also studied and the best fit was related to the Langmuir adsorption isotherm. Adsorption kinetics have been tested and illustrated using pseudo first-order, pseudo-second-order, intraparticle diffusion and Elovich models. The collected results confirmed that the pseudo-second order kinetic model exhibited the best fit with the experimental data. Thermodynamic parameters were calculated and the results referred to an exothermic nature and spontaneity of the adsorption process. Improved decolorization of reactive red 195 A dye from textile industrial wastewater and other water samples were successfully established. Excellent recovery values of RR-195A dye by SB-TTAB adsorbent were determined in the ranges of 96.61–98.76%, 97.79–99.26%, 94.24–100.0% and 90.98–92.96% (±1.0–4.0%) from tap water, raw water, wastewater and sea water, respectively.

Release of outer membrane vesicles in Pseudomonas putida as a response to stress caused by cationic surfactants.

Pseudomonas putida A (ATCC 12633), a degrader of cationic surfactants, releases outer membrane vesicles (OMVs) when grown with tetradecyltrimethylammonium bromide (TTAB) as the sole carbon, nitrogen and energy source. The OMVs exhibit a bilayer structure and were found to be composed of lipopolysaccharides, proteins and phospholipids (PLs) such as cardiolipin, phosphatidylcholine, phosphatidic acid and phosphatidylglycerol (PG). The OMVs showed a marked increase in the PG content, approximately 43 % higher than the amount registered in the parent cells from which the vesicles were derived. After growth of P. putida with TTAB, the amount of lipoprotein covalently cross-linked to the peptidoglycan showed a twofold decrease when compared with values found after growth without the surfactant [16 ± 2 and 28 ± 3 μg (mg cell envelope protein)- 1, respectively]. This decrease in the amount of lipoprotein can be related to areas of loss of contact between the outer membrane and the peptidoglycan and, therefore, to OMV production. In addition, due to its amphiphilic nature, TTAB can contribute to OMV biogenesis, through a physical mechanism, by induction of the curvature of the membrane. Taking into account that OVMs were produced when the cells were grown under external stress, caused by the surfactant, and that TTAB was detected in the vesicles [48 nmol TTAB (nmol PL)- 1], we concluded that this system of TTAB elimination is a mechanism that P. putida A (ATCC 12633) would utilize for alleviating stress caused by cationic surfactants.

Bare and cationic surfactants capped tungsten trioxide nanoparticles based hydrazine chemical sensors: A comparative study

Herein, we report the fabrication and characterization of electrochemical sensors based on bare- and cationic surfactants with different chain lengths and counter ions capped-tungsten trioxide (WO3) nanoparticles. Four different cationic surfactants, i.e., tetradecyltrimethyl ammonium bromide (TTAB),cetylpyridinium chloride (CPyC), cetylpyridinium bromide (CPyB) and hexadecyltrimethyl ammonium chloride (HTAC) were used for the capping of WO3 nanoparticles. The prepared bare and capped WO3 nanoparticles were characterized in terms of their morphological, structural and compositional properties which revealed that the prepared nanoparticles possess mono-dispersity, spherical shape and monoclinic crystal phases. Finally, the prepared nanoparticles were used to fabricate electrochemical sensors for the detection of hydrazine. Our report describes massive comparison of current responses, monitored through cyclic voltammetry for bare and surfactant capped-WO3nanoparticles (NPs). The sensitivity values of the fabricated amperometric sensors range from 3.38 to 10 (μA/μMcm2) with limits of detection ranging from 29 to 59μM.

Surface adsorption of sulfonated poly(phenylene sulfone)/C14TAB mixtures and its correlation with foam film stability.

Polyelectrolyte/surfactant mixtures of rigid monosulfonated poly(phenylene sulfone) (sPSO2-220) and tetradecyl trimethylammonium bromide (C14TAB) were investigated by surface tension, surface elasticity and foam film stability measurements. The results were compared to former measurements of polyelectrolyte/surfactant mixtures containing more flexible polyelectrolytes (PAMPS or PSS and C14TAB). For all polyelectrolyte/surfactant mixtures an increased surface adsorption in comparison to the pure surfactant was detected. Moreover, sPSO2-220/C14TAB mixtures showed a much higher surface activity and foam film stability than mixtures with more flexible polyelectrolytes. The results presented give insight into the surface adsorption and foam film formation of rigid polyelectrolyte/surfactant mixtures. Therefore, this study helps to understand the role of polyelectrolyte backbone rigidity in the formation and stabilization of foam films made from polyelectrolyte/surfactant mixtures.

Kinetics and Mechanism of Cationic Flexible Nanoparticles (CFN) - Catalyzed Piperidinolysis of Anionic Phenyl Salicylate: CFN = TTABr/MX/H2O with MX = NaCl, NaBr; CnH2n+1CO2Na, n = 4, 5, 6 and 7.

The present study is focused on the effect of the TTABr/MX/H2O-nanoparticles on the rate of piperidinolysis of ionized phenyl salicylate where TTABr represents tetradecyltrimethylammonium bromide and MX = NaCl, NaBr and CnH2n+1CO2Na with n = 4, 5, 6 and 7. Pseudo-first-order rate constant for the piperidinolysis of ionized phenyl salicylate at 35°C and constant concentration [PSa(-)]T = 0.2 mM, [Pip]T = 0.1 M, [NaOH] = 30 mM, [TTABr]T and different [MX] follow an empirical relationship which gives two empirical constant, (X)kcat and K(X/S). The value of relative counterion (X) binding constant, RX(Br) were calculated from the relationship; RX(Br) = (X)kcat/(Br)kcat. The values of RX(Br) for X = C4H9CO2(-), C5H11CO2(-), C6H13CO2(-), and C7H15CO2(-) are increasing with increase in the number of alkyl chain of counterion X.

Interactions in the mixed micelles of monomeric and gemini surfactants: Influence of some co-solvents as a function of temperature

Mixed micellar behavior of a series of m-2-m cationic gemini surfactants (where m=10, 12 and 14) with monomeric surfactants (dodecyltrimethylammonium bromide, tetradecyltrimethyl-ammonium bromide and cetyltrimethylammonium bromide) has been studied in aqueous and in aqueous n-propanol, n-butanol, tertiary butanol, propylene glycol and glycerol solutions using conductivity, surface tension, viscosity and dynamic light scattering techniques at 298.15, 308.15 and 318.15K, respectively. In mixtures of 10–2–10 with monomeric surfactants, the synergistic interactions increase with the chain length of monomeric surfactants whereas the mixtures with 12–2–12 and 14–2–14 exhibit the opposite trends. However, the synergistic interactions decrease with the increase in temperature of all the mixtures. The thermodynamic and surface parameters have been evaluated and the influence of the variations in hydrophobic chain length of the surfactants and the type of the co-solvent on these parameters has been discussed. The hydrodynamic diameter increases with the chain length of the surfactants.

Surfactant functionalized tungsten oxide nanoparticles with enhanced photocatalytic activity

Herein, we report the facile synthesis, detailed characterizations and environmental remediation applications of surfactant functionalized tungsten oxide (WO3) nanoparticles (NPs). Different cationic surfactants with different chain lengths and counter ions such as cetylpyridinium chloride (CPyC), cetylpyridinium bromide (CPyB), hexadecyltrimethyl ammonium bromide (HTAC) and tetradecyltrimethyl ammonium bromide (TTAB) were used. These templates served a dual purpose: firstly, functionalization of the nanoparticles and secondly, control the stoichiometry, thus preventing the agglomeration in the nanoparticles. The as-synthesized nanoparticles were characterized in detail to check the morphological, structural, compositional, optical and photocatalytic properties. The detailed characterizations revealed the mono-dispersity of spherical shaped nanoparticles that are grown in high density, possessing monoclinic phase. Further, the functionalized WO3 nanoparticles were used as efficient photocatalysts for the photocatalytic degradation of highly toxic but immensely used azo dye, i.e. congo-red (CR). The photocatalytic degradation reaction conditions were optimized by carrying out various concentration dependent experiments (both photocatalyst and initial dye concentration) and also optimizing irradiation time. The detailed photocatalytic experiments revealed that the photo-degradation followed second order kinetics and the degradation efficiency was over 95% for all the surfactant functionalized WO3 nanoparticles. Importantly, this paper presents the comparison of the photo-degradation activities of prepared functionalized WO3 nanoparticles towards the differences in the chain length, counter-ions and arrangement or orientation of surfactants on the nanoparticle surfaces.

The thermal signature of wormlike micelles

The variations in enthalpy (ΔfHWLM) and critical concentrations associated with the formation of wormlike micelles (WLMs) from combinations of tetradecyltrimethylammonium bromide (C14TAB) and various aromatic co-solutes were determined using isothermal titration calorimetry (ITC). Three groups of aromatic molecules were investigated: neutral (phenol), benzoate derivatives and cinnamate derivatives. In addition, the thermal stabilities of the WLMs (of hexadecyltrimethylammonium bromide, C16TAB) and the aromatic co-solutes of the three groups were investigated by measuring the temperatures at which the WLMs break and lose their ability to produce hydrodynamic drag reduction. A comparison of the results was used to establish correlations between the spontaneity of WLMs formation, their thermal stability and the molecular structure of the aromatic co-solutes. A characteristic thermal pattern with four steps was observed when WLMs are formed, that depended on the co-solute structure. Micellar growth was found to be an exothermic process, related to the fusion of the end caps allied with the incorporation of more co-solutes. The co-solutes that had negative charge and were able to maintain planar configuration demonstrated stronger interactions and also showed higher thermal stability through drag reduction.

Aggregation and microenvironmental properties of gemini and conventional mixed surfactants systems: A fluorometric study

Aggregation behavior of cationic gemini (hexanediyl-1,5-bis(dimethylcettylammonium bromide) (16-5-16)) surfactant with conventional single chain surfactants cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) were studied with the help of fluorescence measurements. Fluorescence probe is a proficient technique for examining the surfactant-surfactant interaction and aggregation. The micelle aggregation number (Nagg) was measured using steady-state fluorescence quenching method. The micelle aggregation numbers of binary combinations fall between those of constituent surfactants. The micropolarity (I1/I3), binding constant (Ksv) and dielectric constant (Dexp) of mixed systems were determined from the ratio of peaks intensity in the pyrene fluorescence spectrum. The I1/I3 values were found to be more than >1, showing more polar environment around pyrene in the mixed micelle as compared to the pure micelles.

Influence of surface capping on oxygen reduction catalysis: A case study of 1.7 nm Pt nanoparticles

Organic and polymer capping agents are prevailingly used in the synthesis of metal nanocrystals to render size and shape controls for desirable catalytic properties. A general assumption in the electrocatalysis field is that the capping agents block active sites and hinder catalytic turnover. However there have been a number of experimental results suggesting otherwise. Investigation of the fundamental correlations between the surface capping and the catalytic kinetics of metal nanoparticles is of paramount importance yet still remains challenging in large part due to structural changes induced by capping agent removal or synthesis using different capping agents. Our approach involves a unique catalyst system comprising of 1.7nm Pt nanoparticles with and without various surface capping. We find that surface capping affects both activity and selectivity of electrocatalytic oxygen reduction reaction. The influences can be positive, neutral or negative. The five capping agents studied fall into three groups. Polyacrylic acid (PAA) and polyvinylpyrrolidone (PVP) cappings do not change the onset potential or product selectivity, but increase the catalytic current density. Sodium dodecyl sulfate (SDS) and tetradecyltrimethylammonium bromide (TTAB) cappings do not change the onset potential or product selectivity, but slightly decrease the catalytic current density. Oleylamine (OA) capping significantly decreases the onset potential and the catalytic current density as well as change the product selectivity by favoring a high percentage of 2-electron reduction.

A Solid Phase Vibrational Circular Dichroism Study of Polypeptide-Surfactant Interaction.

We studied the interaction of poly-l-lysine (PLL) and poly-l-arginine (PLAG) with sodium dodecyl sulfate (SDS) surfactant and the interaction of poly-l-glutamic acid (PLGA) and poly-l-aspartic acid (PLAA) with tetradecyltrimethylammonium bromide (TTAB) surfactant using vibrational circular dichroism (VCD) spectroscopy in the region of C-H stretching vibration and in the Amide I region both in solution and in mulls. A chirality transfer from polypeptides to achiral surfactants was observed in the C-H stretching region, where measurements in solution were impossible. This observation was enabled by a special sample treatment technique using lyophilization and the preparation of mulls. This technique demonstrated itself as an interesting and beneficial tool for VCD measurements. In addition, we observed that SDS changed the secondary structure of PLL to the β-sheet and of PLAG to the α-helix. TTAB disrupted the PLGA and PLAA structure. These results were obtained in the mull but were confirmed by the VCD spectra measured in solution and by electronic circular dichroism. The chirality transfer from the polypeptides to SDS was caused by polypeptides ordered into a specific conformation during the interaction, while in the TTBA system it was induced primarily by the chirality of the amino acid residues.

Understanding thermodynamics of drug partitioning in micelles and delivery to proteins: Studies with naproxen, diclofenac sodium, tetradecyltrimethylammonium bromide, and bovine serum albumin

The use of surfactants in drug delivery has offered several advantages. Quantitative knowledge of the interactions of drugs with micellar systems is essential for deriving guidelines to design efficient drug delivery systems. In this work we have quantitatively addressed the mechanism of interaction of naproxen and diclofenac sodium with the micelles and monomers of tetradecyltrimethylammonium bromide (TTAB) based on thermodynamic studies by using isothermal titration calorimetry. The mechanism of interaction of the drugs with TTAB is based on identification of the nature of interactions of the former with the surfactant micelles and monomers. The values of partitioning constant (which is same as equilibrium constant for the reaction of drugs with the surfactant micelles), enthalpy, entropy and stoichiometry of partitioning have been determined and discussed in terms of possible intermolecular interactions. Further, the interaction of the drug naproxen with bovine serum albumin, when delivered from the micellar media has also been addressed in terms of binding constant, enthalpy and entropy of binding. The results are important in developing improved strategies for effective drug delivery systems.

TTABr 미셀 용액속에서 2-알킬벤즈이미다졸 음이온에 의해 추진되는 디페닐-4-니트로페닐 포스페네이트(DPNPIN)의 탈인산화반응

This study is mainly focused on micellar effect of tetradecyltrimethyl ammonium bromide(TTABr) solution including alkylbenzimidazole(R-BI) on dephosphorylation of diphenyl-4-nitrophenylphosphinate(DPNPIN) in carbonate buffer(pH 10.7). Dephosphorylation of DPNPIN is accelerated by <TEX>$BI^{\Theta}$</TEX> ion in <TEX>$10^2$</TEX> M Carbonate buffer(pH 10.7) of <TEX>$4{\times}10^{-4}$</TEX> M TTABr solution up to 80 times as compared with the reaction in Carbonate buffer by no benzimidazole(BI) solution of TTABr. The value of pseudo first order rate constant(<TEX>$k_{\psi}$</TEX>) of the reaction in TTABr solution reached a maximum rate constant increasing micelle concentration. The reaction mediated by <TEX>$R-BI^{\Theta}$</TEX> in micellar solutions are obviously slower than those by <TEX>$BI^{\Theta}$</TEX>, and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of <TEX>$R-BI^{\Theta}$</TEX> in Stern layer of micellar solution. The surfactant reagent, TTABr, strongly catalyzes the reaction of DPNPIN with R-BI and its anion(<TEX>$R-BI^{\Theta}$</TEX>) in Carbonate buffer(pH 10.7). For example, <TEX>$4{\times}10^{-4}$</TEX> M TTABr in <TEX>$1{\times}10^{-4}$</TEX> M BI solution increase the rate constant(<TEX>$k_{\psi}=99.7{\times}10^{-4}1/sec$</TEX>) of the dephosphorylation by a factor ca. 28, when compared with reaction(<TEX>$k_{\psi}=3.5{\times}10^{-4}1/sec$</TEX>) in BI solution(without TTABr). And no TTABr solution, in BI solution increase the rate constant(<TEX>$k_{\psi}=3.5{\times}10^{-4}1/sec$</TEX>) of the dephosphorylation by a factor ca. 39, when compared with reaction (<TEX>$k_{\psi}=1.0{\times}10^{-5}1/sec$</TEX>) in water solution(without BI).

Surfactant modified montmorillonite as a low cost adsorbent for 4-chlorophenol: Equilibrium, kinetic and thermodynamic study

Chlorophenols are toxic, mutagenic and carcinogenic compounds that must be removed before discharging into the environment. In this study, montmorillonite (Mt) modified with two cationic surfactants (hexadecyl trimethyl ammonium bromide, HDTMA, and tetradecyl trimethyl ammonium bromide, TTAB) was used to remove 4-chlorophenol (4-CP) from aqueous solutions. The influence of various factors such as surfactant loading rate, contact time, pH, adsorbate content, solution ion strength and temperature was investigated on the sorption. The sorption uptake of 4-CP was increased by increasing the surfactants loaded onto the Mt up to 150% CEC (cation exchange capacity) of the clay. The contact time of 10 min and 45 min and pH of 11 were found to be as the optimum for the sorption of 4-CP by HDTMA-Mt and TTAB-Mt, respectively. The sorption capacity of 4-CP by the sorbents at the equilibrium was 29.96 mg/g for HDTMA-Mt and 25.90 mg/g for TTAB-Mt. The results also indicated that the Freundlich isotherm model and pseudo-second order kinetic model well described the sorption process than other models. It is obvious that the surfactant modified montmorillonite, especially HDTMA type, in comparison with raw Mt was more efficient sorbent to remove 4-CP from aqueous solutions.

Investigation of bovine serum albumin-surfactant aggregation and its physicochemical characteristics

Abstract The mechanism of the formation of aggregates between a protein, bovine serum albumin (BSA), and alkyltrimethylammonium bromides of varied hydrocarbon chain lengths, namely, cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB) in an aqueous solution and the physicochemical characteristics of the aggregates were systematically investigated by surface tensiometry, fluorimetry, UV–vis spectrometry, dynamic light scattering, zeta potential, and differential scanning calorimetry (DSC). The surface tension and fluorimetry data indicate a steady decrease in the critical micelle concentrations of the surfactants with an increase in the amount of BSA in the mixture. The evolution of an additional nonpolar segment in the backbone of BSA was indicated by the fluorescence of pyrene and the intrinsic fluorescence of BSA as well. The decrease in the aggregation number, increase in the area per molecule of the surfactant at the interface with a concomitant increase in the hydrodynamic radius of the aggregate were attributed to the formation of BSA–surfactant mixed aggregate and the induction of the unfolding of BSA by the surfactants. The DSC study and nature of the denaturation curves of BSA indicate that the stability of the BSA–surfactant complex follows the order: CTAB > TTAB > DTAB. The neutralization of the negatively charged surface of BSA by the positively charged surfactants is evident from the zeta potential measurements. Both the head group and nonpolar moiety of the surfactants affected the surface charge of the aggregates and the studied surfactants denature and unfold BSA; the extent of denaturation is predominately decided by the hydrocarbon chain length of the former. The in situ unfolding of the protein and the subsequent formation of the aggregates are proposed. The characteristic parameters of the aggregates were determined.