Role of Asphaltenes in Inhibiting Corrosion and Altering the Wettability of the Steel Surface
Abstract Asphaltenes (heptane insolubles) from a variety of crude oils have been identified previously as contributors to inhibition of internal corrosion of mild steel pipelines. However, the mech...
Asphaltenes and Other Natural Surfactants from Cerro Negro Crude Oil. Stepwise Adsorption at the Water/Toluene Interface: Film Formation and Hydrophobic Effects
The adsorption of asphaltenes and other natural surfactants at the water/toluene interface has been studied here, using both the ring and pendant drop method to measure the interfacial tension (γ). The dependence of γ on the logarithm of the sample concentration (ln C) (represented as the γ(ln C) isotherm) leads to a stepwise isotherm similar to that corresponding to the adsorption of asphaltenes at the toluene/silica interface. As is the case for the toluene/silica interface, the stepwise γ(ln C) isotherm seems to be the result of adsorption at the toluene/water interface of molecules, as well as aggregates formed in solution. Once adsorbed, these aggregates flocculate at the interface, leading to the well-known three-dimensional asphaltene films. In agreement with previous evidence from thermal lens experiments, the onset of asphaltene aggregation was observed near a sample concentration of C = 60 mg/L. Although the presence of aliphatic (acid fraction soluble in heptane, AFSH) and other types of acidic...
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.