RESUMO
In the present work, synthesis and characterization of 15 ionic liquids (ILs) derived from quaternary ammonium and carboxylates were carried out in order to proceed to their evaluation as corrosion inhibitors (CIs) of API X52 steel in 0.5 M HCl. Potentiodynamic tests confirmed the inhibition efficiency (IE) as a function of the chemical configuration of the anion and cation. It was observed that the presence of two carboxylic groups in long linear aliphatic chains reduced the IE, whereas in shorter chains it was increased. Tafel-polarization results revealed the ILs as mixed-type CIs and that the IE was directly proportional to the CI concentration. The compounds with the best IE were 2-amine-benzoate of N,N,N-trimethyl-hexadecan-1-ammonium ([THDA+][-AA]), 3-carboxybut-3-enoate of N,N,N-trimethyl-hexadecan-1-ammonium ([THDA+][-AI]), and dodecanoate of N,N,N-trimethyl-hexadecan-1-ammonium ([THDA+][-AD]) within the 56-84% interval. Furthermore, it was found that the ILs obeyed the Langmuir adsorption isotherm model and inhibited the corrosion of steel through a physicochemical process. Finally, the surface analysis by scanning electron microscopy (SEM) confirmed less steel damage in the presence of CI due to the inhibitor-metal interaction.
Assuntos
Compostos de Amônio , Líquidos Iônicos , Corrosão , Aço/química , AdsorçãoRESUMO
Background: Surfactants are one of the most important raw materials used in various industrial fields as emulsifiers, corrosion inhibitors, foaming agents, detergent products, and so on. However, commercial surfactant production is costly, and its demand is steadily increasing. This study aimed to evaluate the performance of typical strains of Bacillus sp. to produce biosurfactants through fermentation. It also included the investigation of the effect of initial glucose concentration and the carbon to nitrogen ratio. Results: The biosurfactant yield was in the range of 12.46 g/L at initial glucose concentrations of 1070 g/L. The optimum fermentation condition was achieved at a carbon to nitrogen ratio of 12.4, with a decrease in surface tension of up to 27 mN/m. Conclusions: For further development and industrial applications, the modified Gompertz equation is proposed to predict the cell mass and biosurfactant production as a goodness of fit was obtained with this model. The modified Gompertz equation was also extended to enable the excellent prediction of the surface tension.
Assuntos
Tensoativos/metabolismo , Bacillus subtilis/metabolismo , Tensoativos/química , Tensão Superficial , Bacillus subtilis/fisiologia , Carbono/análise , Cinética , Fermentação , Glucose/análise , Micelas , Nitrogênio/análiseRESUMO
This study describes the development of an analytical methodology for the separation of quaternary amines using non-aqueous microchip electrophoresis (NAME) coupled with capacitively coupled contactless conductivity detection (C4D). All experiments were performed using a commercial microchip electrophoresis system consisting of a C4D detector, a high-voltage sequencer and a microfluidic platform to assemble a glass microchip with integrated sensing electrodes. The detection parameters were optimized and the best response was reached applying a 700-kHz sinusoidal wave with 14Vpp excitation voltage. The running electrolyte composition was optimized aiming to achieve the best analytical performance. The mixture containing methanol and acetonitrile at the proportion of 90:10 (v:v) as well as sodium deoxycholate provided separations of ten quaternary amines with high efficiency and baseline resolution. The separation efficiencies ranged from 8.7×104 to 3.0×105 plates/m. The proposed methodology provided linear response in the concentration range between 50 and 1000µmol/L and limits of detection between 2 and 27µmol/L. The analytical feasibility of the proposed methodology was tested in the determination of quaternary amines in corrosion inhibitor samples often used for coating oil pipelines. Five quaternary amines (dodecyltrimethylammonium chloride, tetradecyltrimetylammonium bromide, cetyltrimethylammonium bromide, tetraoctylammonium bromide and tetradodecylammonium bromide) were successfully detected at concentration levels from 0.07 to 6.45mol/L. The accuracy of the developed methodology was investigated and the achieved recovery values varied from 85 to 122%. Based on the reported data, NAME-C4D devices exhibited great potential to provide high performance separations of hydrophobic compounds. The developed methodology can be useful for the analysis of species that usually present strong adsorption on the channel inner walls.