Tereza Neuma de Castro Dantas

Microemulsion systems applied to breakdown petroleum emulsions

Abstract Microemulsion systems obtained using commercial surfactants with demulsifier and emulsion prevention properties have been employed to break down Brazilian crude water-in-oil (W/O) emulsions. These crude oils were supplied by the Brazilian oil company—PETROBRAS—and were characterized by the different Balance sheet of Sediment and Water (BSW) values of 48%, 36%, and 32%. The microemulsion systems formed in this study were composed of an aqueous phase (HCl 5.2% solution); an oil phase (toluene); a cosurfactant/surfactant (C/S) phase (isopropyl alcohol (C)/surfactants (S) with a ratio C/S of 9.0). The microemulsion efficiency to break down oil emulsions was evaluated by a direct contact method between the microemulsions and crude (W/O) emulsions. The Scheffe net statistical planning for mixtures was used to relate the component mass fractions to the relative breakdown of petroleum emulsions. The best composition of the microemulsion system for the complete breakdown of oil emulsions with high BSW values had the lowest C/S phase percentage.

Development of a new propolis microemulsion system for topical applications

Microemulsion systems (MES) offer advantages as drug delivery systems, among them favour drug absorption, being in most case more efficient than other methods in delivering of drug. In this work a new MES was obtained in order to be applied as a pressurized aerosol formulation containing bee propolis ethanolic extract (PEE). For that, pseudoternary phase diagrams were used to characterize the microemulsions boundaries and also to define the Winsor IV microemulsion region of the PEE-MES system containing Tween 80 as surfactant and the cosurfactant ethyl alcohol in small percentage. The obtained results indicated that the best MES was composed by Tween 80 and ethyl alcohol with C/S (cosurfactant/surfactant) ratio equal to 1.0, since it provided a large boundaries in the obtained O/W microemulsion region. This PEE-MES formulation, in which bee propolis consisting as oil phase, is herein designed for topical uses (PEE-MES spraying) in order to treat mouth and throat inflammatory infections. Considering the very large uses of bee propolis in conventional vehicles, MES type of delivery system has to be compatible with achieving the highest drug aim loadings, determined substantially by the specific MES application (drug solubilization in water systems) improving in this case, propolis farmacological aplications. Additionally, PEE-MES antibacterial effect was evidenced and the microemulsion system PEE-MES was also used as newest chemical approach for extraction of bee propolis material from resinous hive.

Counterion Nature and Alkylammonium Halide Adsorption Thermodynamics

Two surfactants were synthesized by reacting hydrogen halides (hydrogen chloride and hydrogen bromide) with 1-dodecylamine. The resultant cationic surfactants, 1-dodecylammonium chloride (DDAC) and 1-dodecylammonium bromide (DDAB), were characterized by NMR spectrometry and FTIR spectroscopy and data related to their adsorption at the fluid liquid/gas interface were obtained employing bubble surface tensiometry, in pure water and in HCl 0.1 M. Data did not fit well to Langmuir isotherm but Frumkin isotherm did adequately describe to process of adsorption. Adsorption isotherms, as well as data related to critical micelle concentration, CMC, indicated that in HCl 0.1 M, the presence of electrolytes and a common ion to DDAC decreased chloride solvation, changing surface packing and adsorption profile for this surfactant.

Preparation and characterization of PAni-PMMA dispersions

Blends of polyaniline (PAni) and poly(methyl methacrylate) (PMMA) have been produced using core‐shell particle synthesis, which is advantageous because it allows changing surface‐related properties of PMMA with relatively small amounts of PAni and without the use of organic solvents. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements indicated that the deposition of polyaniline seems to alter the regular shape of the primary acrylic latex particles. The coverage of PMMA particles by PAni was confirmed by FTIR measurements, where distinct data were obtained from the transmission and diffuse reflectance modes, since the latter is surface sensitive. The zeta potential, which is also a surface‐related property, increased with the contents of PAni, as the shells probably became protonated with PAni in the emeraldine salt form. Coverage with PAni did not affect the thermal bulk properties of the PMMA shells.

Characterization of the Liquid-Gas Interface of Aqueous Systems Containing a Derivative from Castor Oil

An anionic surfactant, synthesized with ricinoleic acid from castor oil, was obtained and its behavior in terms of microemulsion formation (via pseudo-ternary diagram analysis) and liquid-gas surface tension (both for microemulsions and pure surfactant-water systems) was determined as a function of temperature and NaCl concentration in the aqueous phase. Microemulsions were formed by using butanol as co-surfactant and kerosene as the oil phase. Concerning the pseudoternary diagrams, the increase in NaCl concentration resulted in a decrease in the Winsor IV region, which was correlated to a possible occurrence of nonmicellar aggregates, induced by the high concentration of NaCl in the aqueous phase. Surface tension measurements also indicated that at the very high NaCl concentrations used there could be the formation of surfactant aggregates. The oil phase in microemulsionated systems decreased surface tension (but increased CMC): Possible interactions between isolated surfactant molecules and molecules from the oil phase were used to explain these results.

Estudo comparativo da eficiência da difenilcarbazida e do óleo de coco saponificado microemulsionados na inibição da corrosão de aço carbono

The effectiveness of microemulsions (ME) of saponified coconut oil (OCS-ME) and diphenylcarbazide (DC-ME) on a carbon steel corrosion inhibition process was evaluated using an electrochemical method of polarization resistance. The ME was prepared with OCS, butanol, kerosene and saline solutions. OCS-ME and DC-ME showed highest inhibitions effects (77% and 92%, respectively) at lower concentrations (0.5% and 0.48 - 0.50%, respectively). The surfactant OCS (in H2O) showed lower efficiency (63% at 0.20 - 0.25% concentration). The greatest inhibitory effect of DC-ME could be correlated with the chemical structure and the rich O/W ME system, which are very important for adsorption phenomena in interfacial ME systems.

Preparation of Acrylic Latexes with Dispersed Magnetite Nanoparticles

Latexes based on ethyl methacrylate and acrylic acid with dispersed magnetite particles were obtained using the technique of miniemulsion polymerization. The polymerizations were carried out (using AIBN as the initiator) after the dispersion of magnetite particles hydrophobized with oleic acid in the acrylic monomers and miniemulsion formation with sodium dodecyl sulfate. Latex nonvolatile content, as well as thermogravimetric behavior of dry solid particles were a function of oleic acid content. Atomic force microscopy analysis of films formed with these latexes revealed the occurrence of ordered patterns on their surfaces.

Recent Advances on the Use of Surfactant Systems as Inhibitors of Corrosion on Metallic Surfaces

In this chapter, we seek to provide a general overview on the use of surfactant systems, particularly micelle solutions and microemulsions, as corrosion inhibitors on metallic surfaces. In addition to important industrial applications of surfactants, particularly in the petroleum industry, surfactant molecules have been studied and employed as successful corrosion inhibitors due to their ability to adsorb onto surfaces, forming an interfacial film and protecting them from corrosive agents. Several parameters affect the mechanism of corrosion inhibition, such as the type of surfactant, temperature, and composition of the chemical systems used. Different adsorption phenomena are established that determine the ultimate ability of the inhibiting system to impair the development of a corrosion environment. Theoretical aspects of surfactant aggregation are considered to discuss the general features of corrosion inhibition, as in salt- and acid-induced corrosion phenomena. The chemical nature of the surfactant molecule and how it is synthesized or produced are also important aspects that may be accounted for in the formulation of novel systems. Particular emphasis is given to the use of natural, renewable raw material, like vegetable oils such as cashew-nut shell liquid and castor oil, to synthesize surfactants that are precursors of corrosion inhibitors, at lower costs, as part of worldwide concerns regarding the search for environmentally friendly options for science and technology. Aggregation parameters such as surface excess, surface area, and variation of free energy of micellization, together with potentiokinetic and small-angle X-ray scattering measurements, are useful to describe the adsorption mechanism of surfactant molecules on solid–liquid interfaces, explaining the distinct behavior of specific systems on metallic surfaces. Our experimental work involves the use of some anionic and cationic surfactants with special chemical moieties that render them potentially good corrosion inhibitors, like amine and epoxy groups. Some recent advances on their use are also presented and discussed; they are part of a major series of both fundamental and practical research activities that have been undertaken in order to diversify the use of surfactant systems in the industry, particularly as inhibitors of corrosion of metallic surfaces.

Comparative Study of Injection Systems in Vapor Phase in the Remediation of Soils Contaminated by Diesel

Gasoline and diesel leaks in underground storage tanks contaminate soils with petroleum hydrocarbons. Various techniques using surfactants have been proposed to remedy this type of contamination. This study presents the application of different systems containing surfactants in vapor phase. It compares the removal efficiencies of diesel contaminated soils using vapor injection systems: surfactant water solutions, micro-emulsions, and nano-emulsions. The surfactant used in the experiments was ethoxylated alcohol UNTL-90 in aqueous solution, in nano-emulsion, and micro-emulsion systems. Among the systems investigated, the nano-emulsion showed the highest removal efficiency (88%), being environmentally friendly and technically feasible with a system that has a lower content of active matter.

RHEOLOGY OF INVERSE EMULSIONS WITH CHITOSAN, CTAB, AND CYCLOHEXANE

Inverse emulsions consisting of chitosan solution as the dispersed phase and cyclohexane as the continuous phase were obtained, using cetyl trimethylammonium bromide (CTAB) as surfactant. The obtained dispersions clearly presented pseudoplastic character, which was evidenced by an intense drop in apparent viscosity as shear rate was increased. This pseudoplastic behavior was related to the formation of chitosan loops from the micelles to the continuous phase, promoting intermicellar interactions. Apparent shear modulus determination supported the presence of temporary cross‐linking and results from creep experiments were analyzed using Burgers model, in order to separate viscous and elastic intermicellar interactions.