Cationic Gemini Surfactants Research Articles

The Synergistic Effect of NaHSO4 and NaCl Salts on Corrosion Inhibition Performance of Two Gemini Cationic Surfactant Ionic Liquids

In this study, two imidazolium-based ionic liquid surfactants (TSIL and EFAIL) were first synthesized, and then investigated the synergistic effects of NaHSO4 and NaCl salts on corrosion inhibition performance of TSIL and EFAIL inhibitors on low carbon steel samples in 1M HCl solution. For this aim, the electrochemical techniques of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), surface morphology analyses, and quantum chemical calculations were employed. Results showed that adding salts to acidic solutions containing EFAIL and TSIL increased their inhibition efficiency. Furthermore, addition of NaHSO4 to TSIL-containing solution could further increase the inhibition efficiency compared to other mixtures of the salts and the inhibitors. The DFT results also revealed that the energy gap of TSIL is lower than that of EFAIL, implying that TSIL has more chemical reactivity and less kinetic stability than EFAIL.

Removal of Phenol from Wastewater Using Micellar-Enhanced Ultrafiltration with Quaternary Ammonium Salt Cationic Gemini Surfactants

Micellar-enhanced ultrafiltration (MEUF) as a surfactant-based separation process is promising for the treatment of low concentration organic wastewater. Gemini surfactant becomes the focus of the field of MEUF increasingly due to its excellent performance in MEUF. In order to investigate the effect of operational factors on the effectiveness of MEUF process, quaternary ammonium salt Gemini surfactants were used for the removal of phenol. The critical micelle concentration (CMC) values of cationic gemini surfactants (CG12, CG14, and CG16) were analyzed. Then the influence of various factors, include CG concentration, phenol concentration, electrolyte concentration and operating pressure, on the removal performance was investigated. Finally, BBD experimental design was carried out to identify optimal operational conditions. The results showed that hydrophobic chain length of Gemini surfactant s have significant effect on its CMC value and the MEUF process. The longer the hydrophobic chain length, the higher phenol rejection. However, it can result in membrane fouling. CG concentration has significant influence on phenol rejection and permeation flux. And phenol concentration has a direct impact on its removal. In addition, the optimal operational condition is that CG12 concentration at 10 CMC, phenol concentration at 1 mM, and NaCl concentration at 25 mM. The corresponding optimal phenol rejection is 91.16%, the optimal permeate flux is 29.33 L/m2 h.

Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties and antibacterial activity

Nine novel cationic gemini surfactants containing both amide and ester groups were synthesized through a three-step reaction. These surfactants have the general formula of CnH2n+1OOCCH2N+(CH2)2-(CH2)3-NHOC-(CH2)m-CONH-(CH2)3-N+(CH2)2CH2COOCnH2n+1 (with n = 8, 10, 12 and m = 2, 3, 4), named BEQA-n, PEQA-n and HEQA-n (B, P, H correspond to surfactants of m = 2, 3, 4 and n = 8, 10, 12, respectively). Chemical structures, surface activity, cleavable properties, electrolytes tolerance, foam properties and antibacterial activity of these surfactants were successively investigated. The results show that the surfactants have lower critical micelle concentration (CMC) than traditional monomer surfactants. The values of CMC and the degree of counter ion dissociation (α) depend on the lengths of hydrophobic chain and spacer. The values of Krafft temperatures (Kt < 0 °C) and the standard Gibbs free energy (∆G0mic < 0) indicate that all surfactants have good water solubility and micelle-forming ability. The simultaneous presence of the amide and ester groups makes these surfactants have good hydrolytic ability in both basic and the acidic solutions. In addition, the surfactants exhibit greater electrolyte tolerance to NaCl than CaCl2. It is worth mentioning that EQA-8 and PEQA-12 have 200 g/L NaCl tolerance. Moreover, all of the surfactants have certain antibacterial activity against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922), and the surfactants with hydrophobic chain length n = 10 have the strongest antibacterial activity.

The Synthesis, Self-Assembled Structures, and Microbicidal Activity of Cationic Gemini Surfactants with Branched Tridecyl Chains

Cationic gemini surfactants with polymethylene spacer and linear alkyl chains containing an even number of carbon atoms have been extensively studied in the recent past, with the emphasis put on the determination of their aggregation behaviour in aqueous solution and their biological properties. However, the information on the aggregation of branched gemini surfactants with an odd number of carbon atoms in their alkyl chains is only sparsely reported in the literature. To help cover this gap in the research of cationic gemini surfactants, a series of branched bisammonium cationic gemini surfactants with an odd number of carbon atoms in alkyl chains (tridecane-2-yl chains) and a polymethylene spacer with a variable length ranging from 3 to 12 carbon atoms have been synthesized and investigated. Critical micelle concentration, which was determined by three methods, was found to be in the order 10−4 mol/L. A comparison of the obtained data of the novel series of tridecyl chain geminis with those of gemini surfactants with dodecyl chains and an identical spacer structure revealed that structural differences between both series of gemini surfactants result in different aggregation and surface properties for surfactants with 6 and 8 methylene groups in the spacer (N,N’-bis(tridecane-2-yl)-N,N,N’,N’-tetramethylhexane-1,6-diaminium dibromide and N,N’-bis(tridecane-2-yl)-N,N,N’,N’-tetramethyloctane-1,8-diaminium dibromide) with the cmc values 8.2 × 10−4 mol/L and 6.5 × 10−4 mol/L, respectively, as determined by surface tension measurements. Particle size analysis showed the formation of small stable spherical micelles in the interval between 2.8 and 5 nm and with zeta potential around +50 mV, which are independent of surfactant concentration and increase with the increasing spacer length. Microbicidal activity of 13-s-13 gemini surfactants was found to be efficient against Gram-positive, Gram-negative bacteria and yeast.

Synthesis and characterization of gemini ester surfactant and its application in efficient fabric softening

Cationic surfactants with ester groups are considered as an important class of hydrolyzable and biodegradable materials utilized in multiple fields. In this work, a new type of gemini cationic surfactant containing two ester groups, N1,N1,N4,N4-tetramethyl-N1,N4-bis(2-(hexadecanoyloxy)ethyl)butane-1,4-diammonium bromide (TBDB), an 18-4-18 type gemini surfactant, has been successfully synthesized in a three-step reaction from natural palmitic acid, thionyl chloride, N,N-dimethylethanolamine and 1,4-dibromobutane. The maximum yield reaches about 94% under the optimum reaction conditions. The structures of the final product were characterized by FT-IR, 1H NMR and mass spectra. The critical micelle concentration (CMC) and surface tension of its aqueous solution are ~3.09 × 10−5 M and 38.4 mN/m at 25 °C, respectively, and the gemini ester surfactant shows high benzene solubilization capacity. When treating cotton fabric, it can effectively retain the whiteness and surface hydrophilicity of the fabric while exhibiting a higher fabric-softening ability than the corresponding monomeric surfactants, due to its more efficient adsorption onto the fabric surface. The discovery suggests that this kind gemini ester surfactant is promising with potential applications in the fields of surfactants and coatings.

Formation of carboxymethylchitosan/gemini surfactant adsorption layers at the air/water interface: Effects of association in the bulk

The surface properties of mixed solutions containing an anionic polyelectrolyte, carboxymethylchitosan (CMCH), and a cationic gemini surfactant, 1,2-bis(dodecyldimethlyammonio)hexane dibromide (C12C6C12), were studied by measuring the surface tension and the dynamic surface elasticity. The association behaviors in the solutions were also measured by fluorescence probe technique. The results showed that the adsorption layer transformed from pure elastic 2D layer to visco-elastic 3D layer with increase in surfactant concentration. The microparticles in the 3D layer were adsorbed from the adjacent bulk to the surface but not formed directly in the surface layer as it was sometimes assumed in other polyelectrolyte/surfactant systems. The stress relaxation mechanism were supposed to be the mass exchange between the unstructured thinner film surrounding the microparticles and the adjacent bulk during the surface compression or expansion. These surface properties of CMCH/C12C6C12 solutions were influenced strongly by the association in the bulk solution.

Cationic gemini-surfactants based on waste cooking oil as new ‘green’ inhibitors for N80-steel corrosion in sulphuric acid: A combined empirical and theoretical approaches

The objective of this report is to investigate the inhibition of cationic gemini-surfactants based on waste cooking, as a green source of inhibitors against acidic corrosion of N80-steel. Two Gemini cationic surfactants have been prepared based on waste frying oil with full characterization by different spectral tools (FTIR, 1H NMR and 13C NMR), and investigated as sustainable inhibitors for N80-steel corrosion in 1.0 M sulphuric acid. The activities of the prepared Gemini cationic compounds were evaluated from the surface-tension studies. The corrosion protection capacity was evaluated by utilizing electrochemical tools namely; LPR corrosion rate, electrochemical impedance-spectroscopy (EIS) and potentiodynamic-polarization (PDP) methods. The PDP findings demonstrated that these surfactants behaved as mixed-typed inhibitors. The surfactants prohibited N80-steel corrosion at a lower [inhibitor] and supplied an inhibition capacity of 96.48–97.86% in 1 × 10−3 mol/l. The protection power increased with increasing both [surfactant] and alkyl group length. The surfactants adsorb on N80-steel in the studied corrosive medium through chemisorption interactions and their adsorption followed the adsorption model of Langmuir. Surface morphology observations (FE-SEM and FTIR) suggest that the surfactant species formed a defensive layer on the N80-steel interface. The electronic properties of the prepared surfactants were examined by using DFT calculations (density functional theory). Theoretical findings are consistent with the empirical outcomes.

Lanthanum/Gemini surfactant-modified montmorillonite for simultaneous removal of phosphate and nitrate from aqueous solution

La3+-exchanged bentonite (Phoslock®) is a well-known adsorbent for phosphate, but it is incapable of simultaneously removing nitrate from aqueous solution. In this study, montmorillonite (Mt) was modified stepwise by lanthanum and a cationic gemini surfactant for co-adsorption of phosphate and nitrate. X-ray diffraction patterns revealed that lanthanum existed as LaCO3OH and the gemini surfactant intercalated into the interlayer space of Mt. The contents of lanthanum and gemini surfactant in obtained nanocomposite (LaOMt) were estimated using energy dispersive X-ray spectroscopy and elemental analysis, which are 0.163 and 0.435 mmol/g, respectively. Based on Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, uptake of phosphate was attributed to ligand exchange with hydroxyl and electrostatic attraction on positively charged LaCO3OH, and that of nitrate mainly resulted from the ion exchange with bromide ion and interactions with –R4N+ groups released from Mt layers. The estimated adsorption capacities of LaOMt to nitrate and phosphate were 0.84 and 0.39 mmol/g, respectively. Adsorption of phosphate was negligibly affected by nitrate, but the presence of phosphate facilitated the hydration of LaOMt and improved nitrate uptake. Compared with commercial Phoslock®, LaOMt demonstrated comparable adsorption performance in terms of phosphate removal. Considering the simultaneous uptake of nitrate and stable adsorption performance when ubiquitous anions coexisted, LaOMt is a promising adsorbent for remediation of phosphate and nitrate contaminated wastewater.

Use of Gemini surfactant as emulsion interface microreactor for the synthesis of nitrogen-doped hollow carbon spheres for high-performance supercapacitors

A series of N-doped porous carbon materials with open interconnected mesoporous shells and various mesoscopic morphology were synthesized by using the cationic Gemini surfactant pentane-1,5-bis(dimethylcetyl ammonium bromide) as the soft template through a sol-gel method and the mechanism of interfacial reaction was explored. The controllable morphological structure (particle size, shell thickness and interconnected structure of internal cavities in carbon nanospheres) can be easily achieved by simply adjusting the volume of ethanol and the amount of cationic Gemini surfactant. The synthesized N-doped mesoporous hollow carbon spheres (NMHCSs) exhibit the characteristics of small and tunable particle size (30–140 nm), ultrahigh surface area (1215–1517 cm2 g−1) and large pore volume (1.12–3.22 cm3 g−1), open interconnected hierarchical mesoporous (5–20 nm), high proportion doping of heteroatoms N (4.16–6.74 at.%) and O (6.17–8.68 at.%). The representative NMHCSs as electrical double layer capacitors electrodes in 6 M KOH electrolyte display an excellent electrochemical specific capacitance (240 F g−1 at 0.2 A g−1), superb capacitance retention (161 F g−1 at 20 A g−1), and excellent cycle stability (92% capacitance retention at 10 A g−1 after 5000 cycles). This research develops a simple synthesis strategy for a series of N-enriched carbon materials which exhibit promising application prospects for high-performance supercapacitors.

Effect of chain length and counter-ion on interaction study of mixed micellar system of isoquinoline-based surface active ionic liquid and cationic surfactants in aqueous medium

In the present study, we have investigated the effect of nature of surfactant, chain length and counter-ion on the mixed micellization behaviour ofvarious cationic surfactants, tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylammonium chloride (DTAC) and cationic gemini surfactant, bis(tetradecyldimethylammonium)hexane dibromide(C14-6-C14,2Br) with surface active ionic liquid (SAIL) tetradecylisoquinolinium bromide [C14iQuin][Br]. The interactions and mixed micellar behaviour of cationic surfactants and SAIL in aqueous medium have been studied by employing conductometry measurements and 1H NMR technique. The critical micelle concentration (cmc) and various thermodynamic parameters like standard Gibbs free energy of micellization (ΔGm0), change in standard enthalpy (ΔHm0) and entropy of micellization (ΔSm0) have been calculated from conductometry measurements. Mixed micellar parameters such as ideal cmc (cmc*), micellar mole fraction (X1m), micellar interaction parameter (βm) and activity coefficients, (f1 and f2) have been evaluated by applying Clint, Rubingh and Motomura theoretical models. Synergistic and non-ideal interactions have been found between SAIL and surfactants.

Investigation of Mixing Behavior of both a Conventional Surfactant and Different Inorganic Salts with a Cationic Gemini Surfactant in Aqueous Solution

AbstractN,N′‐bis [3‐(dodecanoylamino)propyl]‐N,N,N′,N′‐tetramethylhexane‐1,6‐diaminium dibromide is a cationic Gemini surfactant including quaternary ammonium salt with amide groups. Critical micelle concentration (CMC) and some thermodynamic parameters of the cationic Gemini surfactant were investigated using surface tension and conductivity methods. Mixed micellization of binary mixtures of the cationic Gemini surfactant with a conventional surfactant cetyl trimethylammonium bromide (CTAB) was investigated using the conductometric method at five different temperatures ranging from 303.15 to 323.15 K. CMC, micellar ionization degree (αm), counterion binding constant (g1), interaction parameter (β), and activity coefficients ( and ) of mixed systems were found out from data of conductivity at different mole fractions for all studied temperatures. Additionally, the effects of some inorganic salts with different concentrations on the surface properties of cationic Gemini surfactant were examined by surface tension measurements. Some surface properties of the pure cationic Gemini surfactant and mixed salts systems were calculated using the data of surface tension.

Inclusion Complexes of Melphalan with Gemini-Conjugated β-Cyclodextrin: Physicochemical Properties and Chemotherapeutic Efficacy in In-Vitro Tumor Models.

β-cyclodextrin (βCD) has been widely explored as an excipient for pharmaceuticals and nutraceuticals as it forms stable host–guest inclusion complexes and enhances the solubility of poorly soluble active agents. To enhance intracellular drug delivery, βCD was chemically conjugated to an 18-carbon chain cationic gemini surfactant which undergoes self-assembly to form nanoscale complexes. The novel gemini surfactant-modified βCD carrier host (hereafter referred to as 18:1βCDg) was designed to combine the solubilization and encapsulation capacity of the βCD macrocycle and the cell-penetrating ability of the gemini surfactant conjugate. Melphalan (Mel), a chemotherapeutic agent for melanoma, was selected as a model for a poorly soluble drug. Characterization of the 18:1βCDg-Mel host–guest complex was carried out using 1D/2D 1H NMR spectroscopy and dynamic light scattering (DLS). The 1D/2D NMR spectral results indicated the formation of stable and well-defined 18:1βCDg-Mel inclusion complexes at the 2:1 host–guest mole ratio; whereas, host–drug interaction was attenuated at greater 18:1βCDg mole ratio due to hydrophobic aggregation that accounts for the reduced Mel solubility. The in vitro evaluations were performed using monolayer, 3D spheroid, and Mel-resistant melanoma cell lines. The 18:1βCDg-Mel complex showed significant enhancement in the chemotherapeutic efficacy of Mel with 2–3-fold decrease in Mel half maximal inhibitory concentration (IC50) values. The findings demonstrate the potential applicability of the 18:1βCDg delivery system as a safe and efficient carrier for a poorly soluble chemotherapeutic in melanoma therapy.

Role of Counterions and Nature of Spacer on Foaming Properties of Novel Polyoxyethylene Cationic Gemini Surfactants

Application of foam in various upstream operations, such as in enhanced oil recovery, has gained significant attention in recent years. A good foaming agent should generate a stable foam, must be thermally stable (&gt;90 °C, typical reservoir temperature), must have a high tolerance to salinity, and should have low adsorption on the reservoir rock. In view of this, four thermally stable and salt-tolerant polyoxyethylene cationic gemini surfactants were synthesized with different spacers (mono phenyl and biphenyl) and different counterions (Br− and Cl−). Foaming properties were evaluated using initial foam generation, foam volume stability at a given time, bubble count, and average foam bubble radius. The effect of counterions and nature of spacers, with and without the presence of salts, on foaming properties was evaluated. It was found that number of phenyl rings (mono phenyl and biphenyl) had no significant effect on foamability and foam stability in the presence or absence of salts. However, the effect of counterions was prominent in deionized water. In deionized water, foam generated by gemini surfactants with bromide as a counterion was more stable compared to the foam generated using the surfactant containing chloride as the counterion. In saline solution, the type of counterion had no effect on the foamability or foam stability of the foam generated using synthesized cationic gemini surfactants. The foam volume stability decreased by the addition of salts; however, a further increase in salt concentration enhanced the foam volume stability. The synthesized surfactants showed good thermal stability, salt tolerance, and foaming properties and can be an attractive choice for upstream applications.

Removal of ethyl, isobutyl, and isoamyl xanthates using cationic gemini surfactant-modified montmorillonites

Xanthate is a widely used collector in the flotation of sulfide minerals and discharge of xanthate-bearing solution could cause detrimental effects on ecological balance. In this study, the cationic gemini surfactant, butane-1,4-bis(dodecyl dimethyl ammonium bromide) (gBDDA), was applied to modify montmorillonite (Mt) for removal of ethyl, isobutyl, and isoamyl xanthates from aqueous solution. Different amounts of gBDDA that were stoichiometrically equivalent to 0.5 and 1.0 times the cation exchange capacity of Mt were used to investigate the effects of gBDDA dosage on xanthates removal by the obtained products (gOMt). Characterization results of gOMt by X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis showed the successful intercalation of gBDDA into the interlayer space and the higher content of gBDDA on the external surface of gOMt-1.0. Ion exchange and hydrophobic interaction accounted for the similar adsorption capacities of gOMt-1.0 for three xanthates (ca., 0.6 mmol/g), regardless of the molecular structure of xanthates. The rapid adsorption rate and high selectivity of gOMt to xanthates were obtained as supported by the complete removal within 60 min and the stable uptake in the sulfate-coexisting system, respectively, suggesting that gOMt could be a promising adsorbent for removal of xanthates from aqueous solution.

Study on a Class of Cationic Gemini Surfactants

Abstract Four cationic Gemini surfactants with different length of the hydrophobic chain (abbreviated as C12-CGB, C14-CGB, C16-CGB and C18-CGB) have been synthesized. The structures were confirmed by MS and 1H NMR. Their basic surface chemical properties and antistatic properties were investigated. The result indicated that upon increasing the number of carbon, the critical micelle concentration (CMC) and the equilibrium surface tension (γ CMC) decreased initially and then increased. The products' Krafft points were all below 0°C except that of C18-CGB, it was 16.5°C. Emulsifying properties were determined by the water separation time method. The data show that the emulsifying capability increased gradually with the increase of concentration and then stabilized. In addition, the static voltage and static half period values of the calicoes treated with the four products were measured. These products exhibited excellent antistatic properties.

Effect of the number of ethylene oxide units on the properties of synthesized tailor-made cationic gemini surfactants for oilfield applications

The solubility and heat stability of the surfactants are the most prominent features required for oilfield applications. Commercial surfactants such as petroleum sulfonate, polyoxyethylene ether, and alkyl benzyl sulfonate suffer because of stability issues under high salinity and high-temperature conditions. Herein, two new cationic amido-amine type poly(ethylene oxide) gemini surfactants containing lower and higher degree of ethoxylation were synthesized. It was observed that the addition of a sufficient number of ethylene oxide groups between the hydrophobic tail and the ionic head group of the cationic gemini surfactant significantly enhanced their solubility. The surfactant containing a higher degree of ethoxylation was found to be soluble in formation water and seawater. However, the surfactant with a lower degree of ethoxylation precipitated in formation water and seawater and hence was not studied further. Thermogravimetric analysis results of the surfactants containing a higher degree of ethoxylation exhibited degradation temperature above 300 °C that was greater than the typical reservoir temperature (90 °C). The structure characterization results of the aged sample of surfactant at 90 °C for 90 days demonstrated the survival of the original chemical structure, revealing a high long-time heat stability. The reduction in critical micelle concentration (CMC) was observed upon enhancing salt concentration, and the minimum CMC was noticed in seawater (3.91 × 10−5 mol/L). Rheological investigations revealed that the viscosity, as well as storage modulus, was reduced upon increasing the concentration of surfactant. The surfactant also exhibited superior foaming properties compared to the commercial surfactants. The cationic amido-amine type poly(ethylene oxide) gemini surfactants showed excellent surface and thermal properties and are potential candidates for oilfield applications such as enhanced oil recovery in harsh reservoir conditions.

Study on mechanism of Gemini surfactant inhibiting acid rock reaction rate

Inhibiting acid-rock reaction rate is an important key in the field of acid fracturing. Based on the acid-rock reaction mechanism and the performance characteristics of surfactant, the surfactant is applied to cover the rock surface for forming an adsorption layer, which can keep H+ from contacting the surface of rock during acid fracturing. In this paper, a series of cationic Gemini surfactants with different hydrophobic chain length are synthesized (Cn-4-Cn, n = 12, 14, 16).The surface tension, adhesion work, and AFM are used to investigate the effect of hydrophobic chain length and concentration of surfactant on surface activities, adsorption morphology and adsorption capacities. The static acid-rock reaction rate is measured and the surface of the rock plate is digitally characterized by 3D scanning. The results show that Gemini surfactants have the high surface activities. It can be recognized from AFM that as the length of the carbon chain increases, the aggregation of Gemini surfactants on the surface to form micelles becomes more and more obvious, resulting in a decrease in the density and area of the adsorption. However there are few differences for adsorption capacities. Therefore, 12-4-12 can restart H+ most efficiently. This conclusion is proved by static acid-rock reaction. In addition, H+ only reacted with the rock from the micro fractures of the adsorption layer formed by 12-4-12, the surface morphology of the rock plate after etching is the best rugged. In conclusion, it is believed that using the Gemini surfactant to form an adsorption layer on the rock surface is a new approach for inhibiting acid rock reaction rate and has great potential in oil field application.

Effects of a counter-ion salt (potassium chloride) on gemini cationic surfactants with different spacer lengths

Gemini cationic surfactants, which have two cationic surfactant molecules connected by a spacer, have received increased attention in recent years as very good thickeners for clean fracturing fluids. We synthesized four Gemini cationic surfactants with three, four, five, and six methylene groups in the spacers. Salts can promote micelle aggregation of viscoelastic surfactants (VESs) and affect their performance and we used potassium chloride (KCl) to study the performance differences of the surfactants with different spacer lengths. The results showed that the surfactant with three methylene groups in its spacer had the lowest critical micelle concentration, and when combined with KCl in solution, it had the best salt tolerance and apparent viscosity in KCl concentrations ranging from 0.2 wt% to 2.6 wt%. In addition, the solution also exhibited an excellent viscoelasticity and a tighter network microstructure, which was confirmed by SEM observation and oscillatory measurement. We conducted rheological measurements for the four Gemini cationic surfactant fracturing fluid formulations with a shear rate of 170 s−1 at up to 100 °C. The solution with KCl and the surfactant with the shortest spacer had distinctly superior rheological properties, and its viscosity could be maintained above 58 mPa.s after 120 min. Finally, we did proppant suspension tests, gel breaking property tests, and core matrix permeability damage rate tests on the four optimized fracturing fluid systems. The solution prepared by KCl and the surfactant with the shortest spacer was found to have the most favorable properties for fracturing fluids. These results demonstrate that decreasing the spacer length of a Gemini cationic surfactant leads to better performance in fracturing fluids.

Cationic gemini surfactant as corrosion inhibitor for mild steel in 1 M HCl and synergistic effect of organic salt (sodium tosylate)

Synergistic result of cationic gemini surfactant (GS) 1,2-bis(N-hexadecyl-N,N-dimethylammonium) ethane dibromide (16-2-16) and organic salt (Sodium tosylate; NaTos) on mild steel corrosion in 1 M HCl solution at various temperatures (30, 40, 50 and 60 °C) has been examined using gravimetric, electrochemical and surface morphology measurement. Investigational result shows that the inhibition efficiency (η) of 16-2-16 GS enhanced in the existence of a set quantity of NaTos. The synergism parameter (Sθ) values are larger than unity, representing large inhibition efficiency, generated via the accumulation of NaTos to 16-2-16 GS is owing to adsorption supportive. The electrochemical results revealed that the 16-2-16 GS in the absence and presence of NaTos act as mixed-type inhibitors. The inhibitor adsorption on the mild steel surface in 1 M HCl solution obeys Langmuir adsorption isotherm. Surface morphology was studied using scanning electron microscopy (SEM).

Gemini histidine based surfactants: Characterization; surface properties and biological activity

New gemini cationic surfactants bearing imidazolium groups as polar heads and alkyl chains of various lengths were prepared using the amino acid histidine as starting material. These surfactants were found to have very low cmc values and reduced the surface tension of water solutions with high efficiency.Their biological properties, antimicrobial and hemolytic activities, depended on the alkyl chain length. These surfactants are active against a wide range of bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Moreover, these gemini surfactants have good DNA binding capacity. These new gemini surfactants show a great potential in cosmetic, food and pharmaceutical industries.