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Biodiesel is the most promising bio-based alternative to the large quantity of fossil diesel fuel used in the transportation sectors. However, its corrosive behavior when in contact with the diesel engine and fuel system components is of serious concern. The present work comprehensively reviews the impacts of biodiesel on the corrosion behavior of metal-based parts in diesel engines such as copper and copper-based alloys, aluminum and aluminum-based alloys, cast iron, carbon steel, and stainless steel. The corrosion mechanisms of the mentioned metals in biodiesel are also presented and discussed in detail. Methods applied to study the corrosion phenomenon and its level are also presented. The reasons leading to the higher corrosiveness of biodiesel vs. diesel fuel, including its higher hygroscopicity, higher electrical conductivity, higher polarity, higher solvency, the presence of water and oxygen in biodiesel promoting microbial growth, and finally, its auto-oxidation resulting in the generation of corrosive agents, i.e., monocarboxylic acids, are also detailed. Finally, the use of corrosion inhibitors in biodiesel to enhance metals/alloys resistance to corrosion is reviewed. Future research needs to further expand biodiesel utilization worldwide are also envisioned. [ABSTRACT FROM AUTHOR]

Organophosphorus (OP) compounds are one of the most hazardous chemicals used as insecticides/pesticide in agricultural practices. A large variety of OP compounds are hydrolyzed by organophosphorus hydrolases (OPH; EC 3.1.8.1). Therefore, OPHs are among the most suitable candidates that could be used in designing enzyme-based sensors for detecting OP compounds. In this work, a novel nanobiosensor for the detection of paraoxon was designed and fabricated. More specifically, OPH was covalently embedded onto chitosan and the enzyme–chitosan bioconjugate was then immobilized on negatively charged gold nanoparticles (AuNPs) electrostatically. The enzyme was immobilized on AuNPs without chitosan as well, to compare the two systems in terms of detection limit and enzyme stability under different pH and temperature conditions. Coumarin 1, a competitive inhibitor of the enzyme, was used as a fluorogenic probe. The emission of coumarin 1 was effectively quenched by the immobilized Au-NPs when bound to the developed nanobioconjugates. However, in the presence of paraoxon, coumarin 1 left the nanobioconjugate, leading to enhanced fluorescence intensity. Moreover, compared to the immobilized enzyme without chitosan, the chitosan-immobilized enzyme was found to possess decreased Km value by more than 50%, and increased Vmax and Kcat values by around 15% and 74%, respectively. Higher stability within a wider range of pH (2–12) and temperature (25–90°C) was also achieved. The method worked in the 0 to 1050 nM concentration ranges, and had a detection limit as low as 5 × 10−11M. [ABSTRACT FROM AUTHOR]

Currently, semi-refined and refined vegetable oils are used as a feedstock in biodiesel production. However, criteria such as competition with conventional fossil fuel, economic reasons, shortage supply of food and its social impact on the global scale have somewhat slowed the development of the biodiesel industry. Spent bleaching earth is currently under-utilized by deposition in landfills with no attempt to recover the oil. In this study the waste oil adsorbed on spent bleaching earth, refined soybean oil, and waste cooking oil were evaluated as potential sources of biodiesel production in Iran. Different characteristics of the oil samples, such as fatty acid composition, peroxide, iodine, acid values, etc., were evaluated. A two-step esterification reaction using methanol was conducted to produce biofuel. Subsequently, physicochemical properties of produced biodiesel were analyzed. The oil content in spent bleaching earth was 19.3%, which was lowered to 3.7% using hexane as the solvent. Gas chromatography showed that palmitic, oleic, and linoleic acids were predominantly fatty acids, respectively, and the highest content of saturated acids belonged to waste cooking oil (24%). The acidity of 8.3% was obtained for the oil recovered from spent bleaching earth followed by waste cooking oil (3.6%) and refined soybean oil (0.1%). Totally, the specifications of all biodiesel produced were in the range defined by ASTM D6751 and EN 14214 standards. Since about 2000–3000 tones of spent bleaching earth residual oil is annually dumped and the amount of waste cooking oil produced yearly is 500,000 tones, there is a great potential for Iran to produce biodiesel from waste oils. [ABSTRACT FROM PUBLISHER]

This article considers the application of the sweeping gas membrane distillation process (SGMD) for direct separation of ethanol-water using a flat sheet PTFE membrane. It also studies the effect of operating parameters including feed concentration, feed temperature, feed flow rate, and sweeping gas flow rate on the permeation flux and selectivity of ethanol/water. The results showed that the increase in feed temperature increases in permeate flux and selectivity. Selectivities of 18.5 to 25 were achieved using dilute feeds within the temperature range of 35 to 55°C. However, by increasing the feed concentration by more than 5 wt.%, the selectivity was decreased. The increase in permeation flux and ethanol selectivity at higher feed flow rates was mainly due to the reduction of polarization effects. Moreover, the PTFE membrane was characterized by AFM. The results showed that the present process could be used as a stand-alone technique for bioethanol process integration. [ABSTRACT FROM AUTHOR]

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The synthesis of magnetic nanoparticles (Fe3O4) and their coating with cetyltrimethyl ammonium bromide (CTAB) has been reported in this study. The synthetic iron oxide nanoparticles were characterized using FTIR, streaming current potential (SCP) and X-ray diffraction techniques. Particle size distribution of bare and coated nanoparticles was investigated by dynamic light scattering (DLS) technique and transmission electron microscopy (TEM). The results obtained revealed that the CTAB modification effectively decreased the particle size and enhanced the dispersion of the particles in solution. In addition, simple separation by using a magnetic field was achieved because CTAB did not alter the superparamagnetic properties of particles. [ABSTRACT FROM AUTHOR]

The synthesis of amino-acid-capped gold nanoparticles (GNPs) and their characterization using agarose gel electrophoresis are reported. The GNPs were capped with L-Arginine and L-Glutamic acids at different pH. At the physiological pH, the results obtained revealed that the interactions between L-Arginine, L-Glutamic acid, and GNPs were of the electrostatic and covalent/ coordinate types, respectively. The capped GNPs possessing free amine/carboxylic groups could play an important role in conjugating biomolecules (e.g., proteins) in various nanobiotechnological applications. In addition, if the pH of the target environment is constant, capped GNPs bound electrostatically are preferred and when variable, then amino-acid-capped GNPs bound covalently/ coordinately are recommended. [ABSTRACT FROM AUTHOR]