The formation of stable water-in-petroleum emulsions is a costly challenge when transporting, processing, and refining heavy crude oil and bitumen. The stability of these emulsions is attributed to interfacial films with well-documented viscoelastic properties that are known to vary with concentration, solvent quality, and asphaltene chemistry. In this study, we explore the impact of aqueous phase pH and salinity on the transient interfacial rheological properties of asphaltenic films. Using two chemically unique asphaltenes, interfacial shear rheology revealed an apparent salt-induced retardation of the interfacial consolidation processes that ultimately engender elasticity to the film. For Hondo asphaltenes at pH 7, a linear dependence of this retardation on the Debye parameter (kappa) suggested that shielding of electrostatic attraction was responsible. Further investigation with dynamic oscillating drop tensiometry at pH 3, 7, and 10 illustrated that intralayer repulsive and attractive electrostatic interactions can significantly influence the evolution of the interfacial structure. More specifically, the transient tension and dilatational modulus profiles indicated several interfacial processes were affected by the addition of salt, including (i) interfacial activity and the extent of adsorption, (ii) interfacial rearrangement and consolidation, and (iii) interfacial transport or displacement or both. Furthermore, the observed asphaltene interfacial behavior was consistent with those published for interfacial structure-forming amphoteric proteins, such as lysozyme and beta-casein.

Lignin fractions with different molecular weight were prepared using a simple and almost green method from switchgrass and pine organosolv lignin. Different proportions of acetone in water, ranging from 30 to 60%, were used for lignin fractionation. A higher concentration of acetone dissolved higher molecular weight fractions of the lignin. Fractionated organosolv lignin showed different molecular weight and functional groups. Higher molecular weight fractions exhibited more aliphatic and less phenolic OH than lower molecular weight fractions. Lower molecular weight fractions lead to more homogeneous structure compared to samples with a higher molecular weight. All fractions showed strong antioxidant activity.

No abstract

No abstract

Livestock and fish farming are rapidly growing industries facing the simultaneous pressure of increasing production demands and limited protein required to produce feed. Bacteria that can convert low-value non-food waste streams into singe cell protein (SCP) present an intriguing route for rapid protein production. The oleaginous bacterium Rhodococcus opacus serves as a model organism for understanding microbial lipid production. SCP production has not been explored using an organism from this genus. In the present research, R. opacus strains DSM 1069 and PD630 were fed three agro-waste streams: (1) orange pulp, juice, and peel; (2) lemon pulp, juice, and peel; and (3) corn stover effluent, to determine if these low-cost substrates would be suitable for producing a value-added product, SCP for aquafarming or livestock feed. Both strains used agro-waste carbon sources as a growth substrate to produce protein-rich cell biomass suggesting that that R. opacus can be used to produce SCP using agro-wastes as low-cost substrates.