Synthesis and some studies on fluorinated cationic surfactants: surface and biocidal activities

Three fluorinated cationic surfactants were prepared by condensing N-(2-bromoethyl)perfluoroalkylamides with stoichiometric amounts of pyridine, triethanolamine, and triethylamine to produce three quaternary ammonium salts. The surface and biocidal properties of these surfactants were investigated to find the relation between the structure of the hydrophilic portion of the compounds and their efficiency as biocides. The properties studied included critical micelle concentration (CMC), effectiveness (II_CMC), surface excess concentration (T_max), and area occupied by a molecule (A_min). Free energies of micellization (ΔG _mic ^o) and adsorption (ΔG _ads ^o) of the surfactants in aqueous solution were calculated. The minimal inhibitory concentrations of the prepared compounds were tested against five strains as representative group of microorganisms.     

Oxidation of unsaturated and hydroxy fatty acids by ruthenium tetroxide and ruthenium oxyanions

The reactions of ruthenium VIII tetroxide (RuO₄) and the ruthenium VII and VI oxyanions, perruthenate (RuO₄ ⁻) and ruthenate (RuO₄ ⁼) with hydroxy substituted and unsaturated fatty acids have been studied. At a 1:1 molar ratio, ruthenium tetroxide (RuO₄) and both oxyanions (RuO₄ ⁻ and RuO₄ ⁼) oxidized 12-hydroxystearic acid to 12-ketostearic acid. With 9, 10-dihydroxystearic acid, the type of oxidation products obtained depended on the amount of ruthenium oxidant used. At high ratios of oxidant to substrate, cleavage to pelargonic and azelaic acids occurred whereas at lower ratios, partial oxidation to diketo and acyloin derivatives predominated. The oxidation of oleic acid with excess ruthenium tetroxide (RuO₄) or perruthenate anion (RuO₄ ⁻) gave the cleavage products pelargonic and azelaic acid through the intermediate formation of dihydroxy and diketo intermediates. Ruthenate anion (RuO₄ ⁼) did not react with the double bond of oleic acid. Agricultural Research Service, U.S. Department of Agriculture.     

Application of arrhenius kinetics to evaluate oxidative stability in vegetable oils by isothermal differential scanning calorimetry

In this study, 10 different vegetable oils were oxidized at four different isothermal temperatures (383, 393, 403, and 413 K) in a differential scanning calorimeter (DSC). The protocol involved oxidizing vegetable oils in a DSC cell with oxygen flow. A rapid increase in evolved heat was observed with an exothermic heat flow appearing during initiation of the oxidation reaction. From this resulting exotherm, the onset of oxidation time (T _o) was determined graphically by the DSC instrument. In our experimental data, linear relationships were determined by extrapolation of the log (T _o) against isothermal temperature. The rates of lipid oxidation were highly correlated with temperature. In addition, based on the Arrhenius equation and activated complex theory, reaction rate constants (k), activation energies (E _a), activation enthalpies (ΔH ^‡), and activation entropies (ΔS ^‡) for oxidative stability of vegetable oils were calculated. The E _a′, ΔH ^‡, and ΔS ^‡ for all vegetable oils ranged from 79 to −104 kJ mol⁻¹, from 76 to −101 kJ mol⁻¹, and from −99 to −20 J K⁻¹ mol⁻¹, respectively. Based on the results obtained, differential scanning calorimetry appears to be a useful new instrumental method for kinetic analysis of lipid oxidation in vegetable oil.     

Preparation,surface-active properties,and antimicrobial activities of bis-quaternary ammonium salts from amines and epichlorohydrin

A series of new cationic surfactants, bis-quaternary ammonium salts, were prepared from tert-alkylamine and a product of the reaction of epichlorohydrin with decyl- and dodecylamine, and their surface-active properties were measured. Specifically, the critical micelle concentration (CMC), effectiveness of surface tension reduction (γ_CMC), surface excess concentration (Γ), area per molecule at the interface (A), and standard free energies of adsorption (ΔG _ads ^o) and of micellization (ΔG _mic ^o) were determined. All these surfactants showed good water solubility and low CMC, more than one order of magnitude lower than those of corresponding mono-alkylammonium salts. They also showed good foaming properties but worse wetting capabilities. Many of these compounds had antimicrobial activities against gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and yeast (Candida albicans), but they were not active against molds.     

Synthesis and study of the surface properties of long-chain alkylnaphthalene sulfonates

Long-chain alkylnaphthalene sulfonates were synthesized by means of a Wurtz-Fittig reaction, and the basic properties were studied in water at 30°C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC). The following values were calculated: area per molecule at the CMC (A_CMC), standard free energy change of micellization (ΔG _mic ^o ), standard free energy of adsorption (ΔG _ad ^o ), and the “efficiency” of a surfactant in reducing surface tension (pC₂₀). The micelle aggregation numbers were measured through steady-state fluorescence-quenching methods. As the chain length of the hydrocarbon of n-alkylnaphthalene sulfonate increased, the Krafft temperature increased, the surface tension decreased, the value of CMC decreased, pC₂₀ increased, ΔG _ad ^o and ΔG _mic ^o became more negative, and the micelle aggregation number increased. The results showed that sodium α-(n-decyl)naphthalene sulfonate (DNS) had a high pC₂₀, low Krafft temperature, and lower CMC than other surfactants in this study. Thus, DNS and the other n-alkylnaphthalene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency, oil recovery, and dyes.     

Synthesis and physicochemical studies of methyl-12-[1′-β-d-lactosyl]-octadec-9-ene-1-oate: A novel biosurfactant analog

Synthesis of a new glycolipid and biosurfactant analog, methyl-12-[1′-β-d-lactosyl]-octadec-9-ene-1-oate (LOD), has been done from easily accessible renewable resources, namely, lactose and ricinoleic acid from castor oil. Surface and thermodynamic properties at the air/water interface including critical micelle concentration (CMC), aggregation number (<N>), maximal densities (Γ_max), minimal area per molecule (A _min), surface pressure at the CMC (Π_CMC ) free energy of adsorption (ΔG _ad ⁰), and free energy of micelle formation per mole of monomer unit (ΔG _m ⁰) were investigated. The results indicate that this particular glycolipid, because of branching in the hydrophobic chain, has a comparatively large A _min value and hence a very low CMC, aggregation number, and less free energy of micellization and adsorption at the air/water inter-face than molecules with a straight hydrophobe, for example, n-dodecyl-β-d-maltoside. The effects of electrolytes (NaCl, KCl, CaCl₂, and AlCl₃) of the same ionic strength and of increasing ionic strength on the interfacial microenvironment of LOD were also investigated. For the same anion, Cl⁻, and the same ionic strength, different cations were found to have different effects on the CMC of LOD. With increasing ionic strength, different electrolytes were found to have different effects on the interfacially located, highly hydrated aqueous layer of the LOD micelle. The water structure-making or-breaking ability of different cations from the interfacial microenvironment of LOD was found to depend on the charge/radius ratio of the cations.     

Ferrocene-Based Cationic Surfactants: Surface and Antimicrobial Properties

A novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO₃ ^{− +}NH₃(CH₂) _n CH₃]₂, where n = 9, 11, or 15 and Fc[SO₃^{− +}NH(CH₃)₂(CH₂) _n CH₃]₂, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and ¹H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface tension. Furthermore, air/water interface parameters including effectiveness (π _CMC), efficiency (Pc₂₀), maximum surface excess (Г_max), and minimum surface area (A _min) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial agents against different bacterial and fungal organisms.     

The effect of poly(vinyl caprolactone-co-vinyl pyridine) and poly(vinyl imidazol-co-vinyl pyridine) on the corrosion of steel in H<Subscript>3</Subscript>PO<Subscript>4</Subscript> media

The inhibiting effect of two organic copolymers namely poly(vinyl caprolactone-co-vinyl pyridine) (PVCVP) and poly(vinyl imidazol-co-vinyl pyridine) (PVIVP) on the corrosion of steel in phosphoric acid was investigated at various temperatures. The study was carried out by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. Inhibition efficiency (E %) increased with polymer concentration to attain 85% at 10⁻⁴ M for PVIVP. Adsorption of polymers on the steel surface in 2 M H₃PO₄ followed the Langmuir isotherm model. EIS measurements show that the dissolution of steel occurs under activation control. Polarisation curves indicate that the tested polymers functioned as cathodic inhibitors. E % values obtained from various methods used are in good agreement with each other. The temperature effect on the corrosion behaviour of steel in 2 M H₃PO₄ in the presence and absence of the inhibitor was studied in the temperature range 298–338 K. The adsorption free energy (ΔG ^o _ads) and the activation parameters (E _a, , ΔS ^o _a) for the steel dissolution reaction in the presence of polymer were determined.     

Bleaching kinetics of sunflowerseed oil

The bleaching process for sunflowerseed oil follows a rate formula, log (A/A ₀)=−κ , according to absorbance measurements. The dark color of crude oil converts to a light color as the absorbance value decreases. The activation energy E _a was calculated from the Arrhenius equation as 3 kJ, and other activation thermodynamic parameters were determined as ΔS ^⊄=−4.4 J K⁻¹, ΔH ^⊄=−31.2 J mol⁻¹, and ΔG ^⊄=1.6 kJ mol⁻¹. The study showed that the bleaching process was exothermic, presented a decrease of entropy, and was a nonspontaneous process during activation.     

Kinetics and thermodynamics of water adsorption onto rice husks ash filled polypropene composites during soaking

The kinetics and thermodynamics of water adsorption onto rice husks ash filled polypropene composites during soaking were studied at different temperatures, quantities and nature of fillers. Raw rice husk, “white” and “black” rice husks ash and Aerosil were used as fillers of polypropene. The increase of fillers contents in the polymer matrix was found to result in non-linear increase of the amount of adsorbed water. The highest adsorption capacity showed the samples filled with raw rice husks, while the lowest—those filled with black rice husks ash. The adsorption kinetics was limited by intra-particle diffusion in plane sheet particles. The values of the diffusion coefficients D, diffusion constants D ^o, activation energy of the diffusion process Е _а, changes of free energy ΔG ^≠, enthalpy ΔH ^≠ and entropy ΔS ^≠ for the formation of the activated complex from the reagent were calculated. A compensation effect between D ^o and Е _а was observed. Based on the Van’t Hoff equation, the values of the changes of standard free energy ΔG ^o, enthalpy ΔH ^o and entropy ΔS ^o of water adsorption were calculated. The sorption process is exothermal in nature and accompanied with decrease of the entropy. The values of the sorption coefficient S and permeability coefficient P were calculated at 25 and 90 °C.     

Micellar and Surface Properties of Some Monomeric Surfactants and a Gemini Cationic Surfactant

The physicochemical and interfacial properties of the monomeric surfactants cetyltrimethyl ammonium bromide (CTAB), cetyltriphenyl phosphonium bromide (CTPB), tetradecyl triphenyl phosphonium bromide (TTPB), cetyldiethylethanol ammonium bromide (CDEEAB), cetyltrimethyl ammonium chloride (CTACl), tetradecyltrimethyl ammonium bromide (TTAB), and a gemini surfactant (C₁₆-3-C_16, 2Br⁻) at different pH (3.1, 7.0, and 7.75) have been investigated by conductivity and surface tension measurements at 300 K. The critical micellar concentration (CMC), degree of micellar ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A _min), Gibbs free energy of micellization (∆G _m⁰), surface pressure at the CMC (π _CMC), and the Gibbs energy of adsorption (∆G _ads⁰) of the monomeric surfactants have also been determined. The CMC, α and Г_max, increase with increasing pH whereas A _min decreases.     

Kinetic Studies on Oxirane Cleavage of Epoxidized Soybean Oil by Methanol and Characterization of Polyols

The kinetics of the oxirane cleavage of epoxidized soybean oil (ESO) by methanol (Me) without a catalyst was studied at 50, 60, 65, 70 °C. The rate of oxirane ring opening is given by k[Ep][Me]², where [Ep] and [Me] are the concentrations of oxiranes in ESO and methanol, respectively and k is a rate constant. From the temperature dependence of the kinetics thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), free energy of activation (ΔF) and activation energy (ΔE _a) were found to be 76.08 (±1.06) kJ mol⁻¹, −118.42 (±3.12) J mol⁻¹ k⁻¹, 111.39 (±2.86) kJ mol⁻¹, and 78.56 (±1.63) kJ mol⁻¹, respectively. The methoxylated polyols formed from the oxirane cleavage reaction , were liquid at room temperature and had three low temperature melting peaks. The results of chemical analysis via titration for residual oxiranes in the reaction system showed good agreement with IR spectroscopy especially the disappearance of epoxy groups at 825, 843 cm⁻¹ and the emergence of hydroxy groups at the OH characteristic absorption peak from 3,100 to 3,800 cm⁻¹.     

The relationship of the environmental effect of surfactants to their interfacial properties

In an investigation of possible relationships between interfacial properties of surfactants and their environmental effect, using several anionic and nonionic surfactants, a linear correlation was found between the parameters, ΔG ⁰ _ad/A _min, and rotifer toxicity. ΔG ⁰ _ad is a standard free energy of adsorption at the air/aqueous solution interface, and A _min is the minimal hydrated cross-sectional area of the surfactant molecule. Both quantities were evaluated from surface tension data. This correlation is much better than attempted correlations of the toxicity with the negative logarithm of the critical micelle concentration (−log CMC) or with ΔG ⁰ _ad or A _min alone. The ΔG ⁰ _ad/A _min correlation with rotifer toxicity is also better than the correlation with the analogous parameter, Δ _s ^| G _ads ^0| A_min, obtained from adsorption isotherms of the surfactants on a solid immobilized membrane simulating a cell membrane. The data support our hypothesis that toxicity is determined both by adsorption tendency and ease of cell membrane penetration.     

The effect of supercooling on crystallization of cocoa butter-vegetable oil blends

The solid fat content (SFC), Avrami index (n), crystallization rate (z), fractal dimension (D), and the pre-exponential term [log(γ)] were determined in blends of cocoa butter (CB) with canola oil or soybean oil crystallized at temperatures (T _Cr) between 9.5 and 13.5°C. The relationship of these parameters with the elasticity (G′) and yield stress (σ^*) values of the crystallized blends was investigated, considering the equilibrium melting temperature (T _M ^o) and the supercooling (i.e., T _Cr ^o−T _M ^o) present in the blends. In general, supercooling was higher in the CB/soybean oil blend [T _M ^o=65.8°C (±3.0°C)] than in the CB/canola oil blend [T _M ^o=33.7°C (±4.9°C)]. Therefore, under similar T _Cr values, higher SFC and z values (P<0.05) were obtained with the CB/soybean oil blend. However, independent of T _Cr TAG followed a spherulitic crystal growth mechanism in both blends. Supercooling calculated with melting temperatures from DSC thermograms explained the SFC and z behavior just within each blend. However, supercooling calculated with T _M ^o explained both the SFC and z behavior within each blend and between the blends. Thus, independent of the blend used, SFC described the behavior of G′_eq and σ^* and pointed out the presence of two supercooling regions. In the lower supercooling region, G′_eq and σ^* decreased as SFC increased between 20 and 23%. In this region, the crystal network structures were formed by a mixture of small β′ crystals and large β crystals. In contrast, in the higher supercooling region (24 to 27% SFC), G′_eq and σ^* had a direct relationship with SFC, and the crystal network structure was formed mainly by small β′ crystals. However, we could not find a particular relationship that described the overall behavior of G′_eq and σ^* as a function of D and independent of the system investigated.     

Phosphorus transformation in a soybean-cropping system in Andosol: effects of winter cover cropping and compost application

Understanding phosphorus (P) transformation is necessary to develop sustainable P management practices on Andosol with large P-fixing capacity. This study was conducted during 2005–2007 in northeastern Japan to determine how the amounts of inorganic P (P_i) and organic P (P_o) fractions change in a Silandic Andosol under soybean production [Glycine max (L.)]. Two treatments were examined: application of composted cattle manure (0 (P0), 61 (P1), and 122 or 183 (P2) kg P ha⁻¹ year⁻¹) and winter cover cropping (no cover crop, rapeseed [Brassica napus], and cereal rye [Secale cereale L.]). Compost was applied before soybean seeding; cover crops were seeded after soybean harvest without further fertilization. Soil P was extracted sequentially with anion exchange resin (P_i), 0.5M NaHCO₃ (P_i, P_o), 0.1M NaOH (P_i, P_o), and 0.5M H₂SO₄ (P_i). Soybean removed 42.3 and 48.5 kg P ha⁻¹ (only 23 and 10% of the added P), respectively, in P1 and P2. In the P2 soil, 64% of excess P was distributed into P_i fractions, mainly resin-P_i and NaOH–P_i (29 and 19%, respectively). In P0, despite no P addition, soybean removed 41.5 kg P ha⁻¹ concurrently with a decrease in NaOH–P_i, suggesting its potential contribution to soybean P uptake. Neither of cover crops had significant effect on soil P fractions during the 3 year period.     

Supercapacitive properties of composite electrodes consisting of polyaniline, carbon nanotube, and RuO2

Three types of composite supercapacitor electrodes were prepared; electroactive polyaniline (PANI), PANI/multi-walled carbon nanotube (CNT), and PANI/CNT/RuO₂. Specifically, the PANI and PANI/CNT were prepared by polymerization, and PANI/CNT/RuO₂ was prepared by electrochemical deposition of RuO₂ on the PANI/CNT matrix. Cyclic voltammetry between −0.2 and 0.8 V (vs. Ag/AgCl) at various scan rates was performed to investigate the supercapacitive properties in an electrolyte solution of 1.0 M H₂SO₄. The PANI/CNT/RuO₂ electrode showed the highest specific capacitance at all scan rates (e.g., 441 and 392 F g⁻¹ at 100 and 1,000 mV s⁻¹, respectively). In contrast, the PANI/CNT electrode demonstrated the best capacitance retention (66%) after 10⁴ cycles. Additional analysis including morphology and complex impedance spectroscopy suggested that with small loading of RuO₂, an increase in capacitance was observed, but dissolution and/or detachment of RuO₂ species from the electrode might occur during cycling to reduce the cycle performance.     

Supercapacitive properties of polyaniline/hydrous RuO2 composite electrode

A composite electrode based on polyaniline (PANI) and hydrous RuO₂ is prepared by electrochemical deposition of PANI onto hydrous RuO₂ (PANI/RuO₂) and its supercapacitive properties are investigated using cyclic voltammetry. The specific capacitances of PANI/RuO₂ and hydrous RuO₂ electrodes are determined to be 708 and 517 F g⁻¹ at 5 mV s⁻¹, respectively. Simple electrodeposition of PANI on the hydrous RuO₂ can achieve comparatively greater capacitance values.     

Corrosion inhibition of mild steel in acidic medium by poly (aniline-co-<Emphasis Type="Italic">o</Emphasis>-toluidine) doped with <Emphasis Type="Italic">p</Emphasis>-toluene sulphonic acid

The corrosion behaviour of mild steel in 0.5 M H₂SO₄ solution containing various concentrations of a p-toluene sulphonic acid doped copolymer formed between aniline and o-toluidine was investigated using weight loss, polarization and electrochemical impedance techniques. The copolymer acted as an effective corrosion inhibitor for mild steel in sulphuric acid medium. The inhibition efficiency has been found to increase with increase in inhibitor concentration, solution temperature and immersion time. Various parameters like E _a for corrosion of mild steel in presence of different concentrations of inhibitor and ΔG _ads, ΔH ⁰, ΔS ⁰ for adsorption of the inhibitor, revealed a strong interaction between inhibitor and mild steel surface. The adsorption of this inhibitor on the mild steel surface obeyed the Langmuir adsorption equation.     

A Thermodynamic Investigation of the Redox Properties of VPO Catalysts

Abstract  

The redox properties of a vanadium phosphorus oxide (VPO) catalyst with a V:P ratio of one were investigated using Coulometric Titration at 873 K. Equilibrium between (VO)₂P₂O₇ and VOPO₄ exists at a P(O₂) of 3 × 10⁻⁴ atm, corresponding to ΔG of −60 kJ/mol O₂. This value for VPO is significantly lower than that measured with other vanadium-containing catalysts that have been studied. Furthermore, compared to other vanadium catalysts, V⁺⁴ was stabilized against further reduction at lower P(O₂). These redox thermodynamics may help to explain the unique catalytic properties of VPO catalysts for partial oxidation of butane to maleic anhydride.     

Electrochemical degradation of Reactive Red 120 using DSA and BDD anodes

Electrochemical oxidation of an azo dye (Reactive Red 120) was studied in acidic media (1 M HClO₄) using DSA type (Ti/IrO₂–RuO₂) and boron doped diamond (BDD) anodes. Ti/IrO₂–RuO₂ exhibited low oxidation power with high selectivity to organic intermediates and low TOC removal (10% at 25 °C and 40% at 80 °C). On the other hand BDD was found to be suitable for total mineralization of the organic loading to CO₂. In both cases, the decoloration of the solution was almost 100% achieved very quickly with BDD (2 Ah L⁻¹) but only after long treatment with Ti/IrO₂–RuO₂ (25 Ah L⁻¹). The instantaneous current efficiency (ICE) was up to 0.13 in the case of Ti/IrO₂–RuO₂ and up to 0.45 in the case of BDD.