Friction properties of vegetable oils

Vegetable oils are a renewable and an environmentally friendly alternative to petroleum-based oils in lubrication and other important application areas. Vegetable oils fall into two broad chemical categories: triesters (or TG) and monoesters. Most vegetable oils are triesters of glycerol with FA, whose characteristics are dependent on the chemistry and composition of the FA residues. A small percentage of vegetable oils are monoesters of long-chain FA and fatty alcohols of varying chemistries. In this work, the free energy of adsorption (ΔG _ads) of safflower (SA), high-oleic safflower (HOSA), and jojoba (JO), methyl oleate (MO), and methyl palmitate (MP) on steel were investigated. SA and HOSA are TG of vegetable oils with FA residues of radically different degrees of unsaturation. JO is a monoester vegetable oil. ΔG _ads is one of the major factors affecting the boundary friction properties of lubricant ingredients. ΔG _ads was found to increase in the order: HOSA≤SA<JO<MO≤MP. The results are consistent with the degree of functionality and other chemical properties of the oils studied.     

Consumption of High-Oleic Soybean Oil Improves Lipid and Lipoprotein Profile in Humans Compared to a Palm Oil Blend: A Randomized Controlled Trial

Partially hydrogenated oils (PHO) have been removed from the food supply due to adverse effects on risk for coronary heart disease (CHD). High-oleic soybean oils (HOSBO) are alternatives that provide functionality for different food applications. The objective of this study was to determine how consumption of diets containing HOSBO compared to other alternative oils, with similar functional properties, modifies LDL cholesterol (LDLc) and other risk factors and biomarkers of CHD. A triple-blind, crossover, randomized controlled trial was conducted in humans (n = 60) with four highly-controlled diets containing (1) HOSBO, (2) 80:20 blend of HOSBO and fully hydrogenated soybean oil (HOSBO+FHSBO), (3) soybean oil (SBO), and (4) 50:50 blend of palm oil and palm kernel oil (PO + PKO). Before and after 29 days of feeding, lipids/lipoproteins, blood pressure, body composition, and markers of inflammation, oxidation, and hemostasis were measured. LDLc, apolipoprotein B (apoB), NonHDL-cholesterol (HDLc), ratios of total cholesterol (TC)-to-HDLc and LDLc-to-HDL cholesterol, and LDL particle number and small LDL particles concentration were lower after HOSBO and HOSBO+FHSBO compared to PO (specific comparisons p < 0.05). Other than TC:HDL, there were no differences in lipid/lipoprotein markers when comparing HOSBO+FHSBO with HOSBO. LDLc and apoB were higher after HOSBO compared to SBO (p < 0.05). PO + PKO increased HDLc (p < 0.001) and apolipoprotein AI (p < 0.03) compared to HOSBO and HOSBO+FHSBO. With the exception of lipid hydroperoxides, dietary treatments did not affect other CHD markers. HOSBO, and blends thereof, is a PHO replacement that results in more favorable lipid/lipoprotein profiles compared to PO + PKO (an alternative fat with similar functional properties).     

Adsorption of amphiphiles at an oil-water vs. an oil-metal interface

Studies were conducted to investigate whether adsorption of amphiphiles from oil onto a degreased metal can be predicted from knowledge about adsorption of the amphiphiles at the oil-water interface. The surface of a degreased metal comprises oxides, hydroxides, and adsorbed water vapor, which form from the reaction of the metal with air and moisture. If the behaviors of amphiphiles at water-oil and metal-oil interfaces are similar, this information can be useful in the development of cheaper and quicker methods of estimating amphiphile adsorption properties on degreased metals. The amphiphiles used were safflower oil (SA) and jojoba oil (JO), both of which are plant-based oils, and methyl palmitate (MP). SA is a triester whereas JO and MP are monoesters. The interfacial tension of water-hexadecane was measured as a function of amphiphile concentration in hexadecane and used to estimate an interfacial-based free energy of adsorption, ΔG _ads. The resulting interfacial-based ΔG _ads values for SA were identical to those reported from friction-based adsorption isotherms. The corresponding values for the monoesters were within the range reported from friction-based adsorption isotherms.     

Kinetic and thermodynamic studies of adsorption of Cu2+ and Pb2+ onto amidoximated bacterial cellulose

Removal of Cu²⁺ and Pb²⁺ from aqueous solutions by adsorption onto amidoximated bacterial cellulose (Am-BC) was investigated. The effects of pH, initial concentration, contact time and temperature were studied in batch experiments. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. The experimental data fits well to the pseudo-second order kinetic model, which indicates that the chemical adsorption is the rate-determining step, instead of mass transfer. The equilibrium adsorption data were described by the Langmuir, Freundlich, and Temkin isotherms. The Am-BC showed a better fit to the Langmuir isotherm. The separation factor (R _L ) revealed the favorable nature of the isotherm. The thermodynamic parameters (ΔH _ads⁰, ΔS _ads⁰, ΔG _ads⁰) for Cu²⁺ and Pb²⁺ adsorption onto Am-BC were also determined from the temperature dependence. The values of enthalpy and entropy indicated that this process was spontaneous and exothermic. The experimental studies indicate that Am-BC would be a potential effective adsorbent to remove the metal ions from wastewater.     

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.     

Adsorption Isotherms for Bleaching Soybean Oil with Activated Attapulgite

Activated attapulgite was characterized and used as bleaching clay (adsorbent) for soybean oil. Adsorption isotherms for bleaching soybean oil were determined to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of oil on activated attapulgite. The Freundlich model was found to provide a better fit with the experimental data than the Langmuir model. The larger Freundlich constant, K _F at higher temperature indicated more effective adsorption. The heat evolved for oil bleaching increased as the levels of activated attapulgite increased from 0.5 to 3%, due to the increase in adsorptive sites with increasing attapulgite levels as well as multilayer adsorption driven by van der Waals’ forces at smaller amounts of adsorbents. There are enough adsorptive sites with 3% attapulgite to adsorb the pigments associated with soybean oil bleaching. The amount of attapulgite has no effect on ΔH _a when it is >3%, and ΔH _a is about 32 kJ/mol.     

Equilibrium adsorption studies on removal of diclofenac sodium from aqueous solution using sawdust–polyaniline (SD–PAn) composites

In this work, equilibrium adsorption studies were carried out for the removal of antiinflamatory drug diclofenac sodium (DS) from aqueous solutions using sawdust–polyaniline(SD-PAn) composite as a potential sorbent at 20, 30, and 40°C. The composite sorbent was characterized by FTIR and SEM analysis. The particles exhibited porous and rough surface. The equilibrium uptake data was interpreted by the Langmuir, the Freundlic, the Temkin, and the Dubinin–Redushkevich (D -R) isotherm models. The maximum adsorption capacity was found to decrease with increase in temperature, thus indicating exothermic nature of the adsorption process. The thermodynamic parameters were evaluated using Langmuir, Flory–Huggins, Frumkin, and modified-Frumkin models. The negative values of ΔG_ads⁰ and ΔH⁰ indicated spontaneous and exothermic nature of the adsorption process, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125:1382–1390, 2012     

Corrosion inhibition of mild steel in acidic media by Basic yellow 13 dye

The inhibition performance of Basic yellow 13 dye on mild-steel corrosion in hydrochloric acid solution was studied at 25 °C using weight loss and electrochemical techniques. The effect of inhibitor concentration on inhibition efficiency has been studied. Inhibition efficiency increased with increase of Basic yellow 13 concentration. The results showed that this inhibitor had good corrosion inhibition even at low concentrations (95% for 0.005 M Basic yellow 13) and its adsorption on mild-steel surface obeys Langmuir isotherm. ΔG _ads was calculated and its negative value indicated spontaneous adsorption of the Basic yellow 13 molecules on the mild-steel surface and strong interaction between inhibitor molecules and metal surface. The value of ΔG _ads was less than 40 kJmol⁻¹, indicating electrostatic interaction between the charged inhibitor molecules and the charged metal surface, i.e., physical adsorption.     

Cooperative adsorption behavior of fatty acid methyl esters from hexadecane <Emphasis Type="Italic">via</Emphasis> coefficient of friction measurements

The frictional behaviors of methyl oleate (MO), methyl palmitate (MP), methyl laurate (ML), and methyl stearate (MSt) as additives in hexadecane have been examined in a boundary lubrication test regime using steel contacts. It was found that the transient attributes of coefficient of friction (COF)-time spectra are a sensitive measure of adsorption equilibria. Critical additive concentrations were defined and used to perform novel and simple Langmuir analyses that provide an order of adsoprtion energies: MSt>MP>MO≥ML. Application of Langmuir, Temkin, and Frumkin-Fowler-Guggenheim adsorption models via nonlinear fitting of a general cooperative model demonstrates the necessary inclusion of cooperative effects in the applied model. In agreement with the qualitative features of steady-state COF-concentration plots, MSt modeling requires minimal cooperative interaction terms. However, MO, MP, and ML data require large attractive interaction terms to be adequately fitted. Primary adsorption energies calculated via the cooperative model are necessarily decreased, whereas total adsorption energies correlate well with values obtained via critical concentration analyses. These results and comparisons with previous adsorption studies of MO and MSt suggest that primary (ester-surface) and secondary (alkyl-surface) adsorbate-adsorbent, adsorbate-adsorbare, and (free-additive) adsorpt-adsorpt interactions collectively determine both the calculated primary and the cooperative interaction energies.     

Application of Full Factorial Design for Removal of Polycyclic Aromatic Dye from Aqueous Solution Using 4A Zeolite: Adsorption Isotherms,Thermodynamic and Kinetic Studies

In this study, removal of the cationic dye acridine orange (AO) from aqueous solution using 4A zeolite was studied. The adsorption experiments were performed using batch system, and full factorial design was employed for investigating the condition of removal efficiency of dye. The four most important operating variables were the initial pH of the solution, the concentration of dye, the contact time, and the temperature. The 18 experiments were required to investigate the effect of variables on removal of the dye. The results were statistically analyzed to define important experimental variables and their levels using the analysis of variance (ANOVA). A regression model that considers the significant main and interaction effects was suggested and fitted the experimental data very well. Model predictions were found to be in good agreement (R² = 99.99%, adjusted R² = 99.86%) with experimental data. The optimized conditions for dye removal were at initial pH 3.0, 20.0 mg L^?1 dye, temperature 298.0 K and 80.0 min adsorption time. The experimental data were analyzed by the Langmuir, Freundlich, Temkin and Sips adsorption models. The maximum predicted adsorption capacities for AO was obtained as 29.851 mg g^?1. The adsorption thermodynamic parameters, namely ΔH°_ads, ΔG°_ads and ΔS°_ads, were determined. Furthermore, the kinetic of AO adsorption on the 4A zeolite was analyzed using pseudo-first- and second-order kinetic models and the results showed that the removal was mainly a pseudo-second-order process.     

Inhibition of mild steel corrosion in acidic medium using starch and surfactants additives

The corrosion inhibition of mild steel in 0.1M H₂SO₄ in presence of starch (polysaccharide) was studied using weight loss and potentiodynamic polarization measurements in the temperature range of 30–60°C. Starch inhibits the corrosion rates of mild steel to a considerable extent; the maximum inhibition efficiency (%IE) being 66.21% at 30^oC in presence of starch concentration of 200 ppm. The effect of the addition of very small concentration of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide on the corrosion inhibition behavior of starch was also studied. The IE of starch significantly improved in presence of both the surfactants. The effect of surfactants on the corrosion inhibition behavior of starch appears to be synergistic in nature. Starch alone and in combination with surfactants is found to obey Langmuir adsorption isotherm from the fit of the experimental data of all concentration and temperature studied. Phenomenon of physical adsorption is proposed from the trend of IE with temperature and also the values E_a, ΔG_ads, and Q_ads obtained. The results obtained by potentiodynamic polarization measurements are consistent with the results of the weight loss measurement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Adsorption and inhibition effect of vanillin on cold rolled steel in 3.0 M H3PO4

The adsorption and inhibition effect of vanillin (4-hydroxy-3-methoxy-benzaldehyde) on cold rolled steel (CRS) in 3.0 M H₃PO₄ at 30–60 °C was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The results show that inhibition efficiency increases with the inhibitor concentration, while decreases with temperature. The adsorption of vanillin obeys Temkin adsorption isotherm. The thermodynamic parameters (adsorption enthalpy ΔH_ads, adsorption free energy ΔG_ads and adsorption entropy ΔS_ads) have been calculated and discussed in detail. Polarization curves show that vanillin acts as a mixed-type inhibitor. EIS shows that charge transfer resistance increases while the capacitance of double layer decreases with the inhibitor concentration, confirming the adsorption process mechanism. The adsorbed film on CRS surface containing vanillin was examined by atomic force microscope (AFM). Quantum chemical calculation was applied to elucidate the adsorption mode of the inhibitor molecule onto steel surface. Depending on the results, the inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

An investigation of some Schiff bases as corrosion inhibitors for austenitic chromium–nickel steel in H2SO4

The corrosion inhibition of austenitic chromium–nickel steel by two Schiff bases, N-(1-toluidine)salicylaldimine and N-(2-hydroxyphenyl)salicylaldimine, was investigated in sulphuric acid medium. The effect of concentration and temperature on inhibition properties was determined. It was found that when the concentrations of inhibitor were increased the inhibition efficiencies () and surface coverage () increased. Some thermodynamic parameters such as free energy of adsorption, G _ads, and enthalpy, H, were determined for the Schiff bases. Experimental results agree with the Temkin isotherm for N-(1-toluidine)salicylaldimine, but the Langmuir isotherm is more appropriate for N-(2-hydroxyphenyl)salicylaldimine.     

Adsorption of some anionic surfactants on barite and at solution/Air interfaces

The adsorption behavior of synthesized anionic surfactants with the chemical structure RO-Ph-N=N-Ph-SO₃Na, where R is an octyl, dodecyl, or cetyl group, was analyzed by using a modified version of the Frumkin adsorption isotherm. The values of thermodynamic parameters (including free energy of micellization, ΔG _mic, and of adsorption, ΔG _ads) at the solution/air interface and the solid/liquid interface were calculated, and the relation between the adsorption of the surfactants at these interfaces was investigated. Studies of the surface properties of these synthetic surfactants showed that the length of the hydrocarbon chain of these surfactants plays a major role in determining their surface and thermodynamic properties and that there is a good relationship between the effectiveness of adsorption of the surfactant and its efficiency as a collector.     

Use of liquid carbon dioxide to remove hexane from soybean oil

Liquid carbon dioxide (L-CO₂) was investigated as a means to separate hexane from the mixture of soybean oil (SBO) and hexane resulting from the hexane extraction of soybeans. Using a fractionation tower, 5 vol of CO₂ (i.e., 100, 200, 300, 500, and 1000 L expanded gas) were passed through 50 mL of two concentrations of n-hexane (i.e., 10 and 25% w/w) in SBO. After passing through the hexane/SBO mixture, the expanded CO₂ was passed through a chilled collection flask to capture extracted hexane and SBO. The raffinate SBO was removed from the column and analyzed for residual hexane using International Organization for Standardization Method 9832:2002. Residual hexane decreased as the amount of L-CO₂ used increased and was less than 20 ppm after 200 L of CO₂. The amount of SBO extracted increased with the volume of CO₂ used. Significantly more SBO and hexane were collected from the 25% sample than the 10% sample. During the extraction of the mixture, the CO₂ selectively carried over TG with lower M.W. This research demonstrates the ability to use L-CO₂ to remove haxane from mixtures of hexane and SBO at both low pressures and temperatures.     

Saturated fatty acid adsorption by acidified rice hull ash

Rice hull ash (RHA) was treated with 1.0 M HNO₃ (RHA-A1) and another batch was treated with 14.0 M HNO₃ (RHA-A14). RHA-A1 and RHA-A14 had a pH of 6.58 and 6.13, respectively. Adsorption of saturated fatty acids (C₈, C₁₀, C₁₂, C₁₄, C₁₆, and C₁₈) was carried out on RHA-A1 and RHA-A14 at 32±1°C. The adsorption data conformed to the Langmuir isotherm. The specific surface area of RHA-A1 was 183.84 m² g⁻¹ while that of RHA-A14 was 174.67 m² g⁻¹. The specific pore volume of RHA-A1 was 0.216 cm³ g⁻¹ while that of RHA-A14 was 0.234 cm³ g⁻¹. The acid-treated ash, RHA-A14 (q _m =0.43±0.03 mmol g⁻¹ where q _m is the amount of adsorbate adsorbed to form a monolayer coverage on the ash particles) showed a twofold increase in the adsorption of fatty acid per gram ash compared to RHA-A1 (q _m =0.25±0.03 mmol g⁻¹). The free energy of adsorption, ΔG° _ads, was determined to be −7.06±0.10 and −6.75±0.11 kcal mol⁻¹ for RHA-A1 and RHA-A14, respectively. The reduced ΔG° _ads values observed for RHA-A14 were attributed to the electrostatic repulsion of the hydrophobic chain of the fatty acid adsorbed on adjacent sites and brought into close proximity of each other. The ΔG° _ads values showed that the process of adsorption took place through physisorption on both RHA.     

Electrochemical characterization of the protective film formed by the unsymmetrical Schiff's base on the mild steel surface in acid media

The corrosion inhibition efficiency of a newly synthesized Schiff's base for the corrosion of mild steel was studied in 1.0 M HCl and 0.5 M H₂SO₄ solutions. The results of weight loss measurements, electrochemical impedance and potentiodynamic polarization measurements consistently demonstrated that the Schiff's base synthesized is a good corrosion inhibitor with an inhibitory efficiency of approximately 92% at an optimum inhibitor concentration of 600 mg/L. The inhibition in both of the corrosive media was observed to be a mixed type. The potential of zero charge (PZC) at the metal–solution interface was determined for both the inhibited and uninhibited solutions to provide the mechanism of inhibition. The inhibitor formed a film on the metal surface through chloride or sulfate bridges depending upon the medium. The temperature dependence of the corrosion rate was also studied in the temperature range from 27 to 50 °C. The value of the activation energy (E_a) calculated showed that the inhibition film formation on the metal surface occurred through chemisorption. The thermodynamic parameters such as the adsorption equilibrium constant (K_ads) and the free energy of adsorption (ΔG_ads) were calculated and discussed. Several adsorption isotherms were tested and the experimental data fit well with the Langmuir adsorption isotherm.     

Composition and oxidative stability of soybean oil in mixtures with jojoba oil

Improvement of the oxidative stability of soybean oil (SBO) by blending with jojoba oil (JO) was investigated. SBO in the presence of 5, 10, 15 and 20 wt‐% of JO was subjected to accelerated storage at 60 °C. Peroxide values (PV), anisidine values (AV), UV absorption characteristics (K₂₃₂ and K₂₇₀ values), and headspace volatiles were determined to monitor the oxidative stability of oil samples. JO was effective in reducing the formation of hydroperoxides and volatile compounds in SBO. The effect was remarkable in SBO/JO blends containing 15 and 20% JO, which showed significant reductions in PV, AV and volatile content with respect to pure SBO. The increased oxidative stability of SBO/JO blends could not be attributed to JO tocopherols, since the addition of JO to SBO significantly reduced the tocopherol content of SBO. Besides the tocopherol content and unsaturation degree of SBO and JO, the effect of the JO ester structure on the oxidative stability of the blends is discussed. The enhanced chemical and flavor stabilities of SBO/JO blends with respect to pure SBO may make a significant contribution to improve the shelf life of SBO by reducing the deterioration reactions related to lipid peroxidation.     

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.