RESUMEN
Hydration phenomena at cement/water interfaces drive the characteristics of oil-well cement slurries. In this study, new epoxy-modified cement slurries were synthesized. The slurries characterization has suggested the presence of low amounts of portlandite in the slurry with the higher content of polymerized epoxy resin. The hydration processes of the cement slurries were studied by heat-conduction microcalorimetry. The energetic and enthalpic hydration data were all exothermic in nature. The cumulative heat release curves have shown the presence of multilinearity of the kinetic processes. The hydration microcalorimetric data were well fitted to the multistep Avrami kinetic model. It was found that the epoxy-modified cement slurries present a good potential to be used in environmental-friendly oil-well operations.
RESUMEN
Loss of zonal isolation in oilwell cementing operations leads to safety and environmental problems. The use of new cement slurries can help to solve this problem. In this paper, an epoxy-modified cement slurry was synthesized and characterized. The features of the modified slurries were evaluated in relation to a standard cement slurry (w/c=0.50). A kinetic study of HCl interaction with the slurries was carried out using cubic molds. The Avrami kinetic model appears to be the most efficient in describing kinetic isotherms obtained from 25 to 55 degrees C. Type of slurry, HCl concentration and temperature effects were also evaluated in HCl adsorption onto cement slurries considering a 2(3) full factorial design. From the statistical analysis, it is inferred that the factor "HCl concentration" has shown a profound influence on the numerical values of the Avrami kinetic constants. However, the best statistical fits were found using binary and tertiary interactive effects. It was found that the epoxy-modified cement slurry presents a good potential to be used in environmental-friendly oilwell operations.
Asunto(s)
Ciclohexilaminas/química , Compuestos Epoxi/química , Industrias/métodos , Compuestos de Bencidrilo , Ácido Clorhídrico , Cinética , Análisis Multivariante , PetróleoRESUMEN
The three-parameter Sips adsorption model was successfully employed to modeled equilibrium adsorption data of a yellow and a red dye onto a mesoporous aminopropyl-silica, in the presence of the surfactant sodium dodecylbenzenesulfonate (DBS) from 25 to 55 degrees C. The results were evaluated in relation to the previously reported surface tension measurements. The presence of curvatures of the van()t Hoff plots suggested the presence of non-zero heat capacities terms (Delta(ads)C(p)). For the yellow dye, it is observed that the values of Delta(ads)H are almost all positive and they decrease in endothermicity, in the absence and in the presence of DBS, from 25 to 55 degrees C. For the red dye, there is an increase in endothermicity in relation to the temperature increase. The negative Delta(ads)G values indicate spontaneous adsorption processes. Almost all adsorption entropy values (Delta(ads)S) were positive. This suggests that entropy is a driving force of adsorption. The adsorption thermodynamic parameters were also evaluated using a new 2(3) full factorial design analysis. The multivariate polynomial modelings indicated that the thermodynamic parameters are also affected by important interactive effects of the experimental factors and not by the temperature changes alone.
Asunto(s)
Colorantes/química , Colorantes/aislamiento & purificación , Dióxido de Silicio/química , Tensoactivos/química , Temperatura , Termodinámica , Adsorción , Aniones , Estructura Molecular , Porosidad , SolucionesRESUMEN
A 2(3) factorial design was employed to evaluate the quantitative removal of the indigo carmine (IC) dye from aqueous solutions on glutaraldehyde cross-linked chitosan. The variables were chitosan masses of 100 and 300 mg, IC concentrations of 2.0 and 5.0 x 10(-5) mol L(-1) and temperatures of 25 and 35 degrees C. The quantitative and energetic adsorption parameters were analyzed statistically using modeling with bilinear equations. The results indicated that increasing the chitosan mass from 100 to 300 mg decreases the IC adsorption/mass ratio (mol g(-1)) whereas a temperature increase of 25-35 degrees C increases it. The principal effect of the IC concentration did not show statistical significance. The factorial experiments demonstrate the existence of a significant antagonistic interaction effect between the chitosan mass and temperature. The adsorption thermodynamic parameters, namely Delta(ads)H, Delta(ads)G, and Delta(ads)S, were determined for all the factorial design results. Endothermic values were found in relation to the Delta(ads)H. The positive Delta(ads)S values indicate that entropy is a driving force for adsorption. The Delta(ads)G values are also significantly affected by important antagonistic and synergistic effects involving all principal and interactive factors. It is concluded that the thermodynamical spontaneity of the IC adsorption parameters are greatly influenced by the interactive factors and not by the temperature changes alone.