Understanding and predicting cloud point phenomena is important for the formulation of nonionic surfactant systems, and the design of cloud‐phenomena‐associated separation processes. There have been several approaches to fit and predict the cloud point phenomena, in most cases using bulk thermodynamic approaches. In this work, we introduced the hydrophilic–lipophilic‐difference and net‐average‐curvature (HLD‐NAC) as an interfacial (curvature) approach to predict cloud point values at different surfactant concentrations (cloud point curve). The HLD‐NAC method could fully predict the cloud point of alkyl ethoxylate of pure surfactants, typically within 4 °C of the experimental values, using published HLD constants, and the molecular structure of the surfactants. For commercial (polydispersed) surfactants, the same level of accuracy can be achieved if the experimental cloud point at 1 wt.% is used to adjust the HLD values. One additional benefit of using the HLD framework is the ability to predict changes in the cloud point curve with the introduction of electrolytes. While other models can fit the experimental data within 1 °C, the greater uncertainty of the HLD‐NAC (~4 °C) is a reasonable compromise given the simplicity of the approach.

The hydrophilic–lipophilic-difference framework predicts the oil and salinity required to induce wormlike micelle formation from surfactant–water systems.

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Zero-valent iron nanoparticles (NZVI) were synthesized and dispersed in solutions of sodium oleate (SO), sodium laurate (SL), sodium dodecyl phosphonate (SDP), and sodium dodecyl sulfate (SDS). The reactivity of these dispersions was evaluated to assess the impact of surfactants on the reduction rate of hydrophilic reactive black 5 (RB5) and hydrophobic carbon tetrachloride (CT) model contaminants. SO and SL, used at their critical micelle concentration (CMC), lowered the reduction rate of RB5 by two and three orders of magnitude, respectively. SO and SL also decreased the reduction rate of CT by up to one order of magnitude. SDS and SDP, at their CMC, decreased the reduction rate of RB5 by approximately 50-fold, but increased the reduction rate of CT. The decrease in RB5 reduction rate might be explained by the formation of adsorbed surfactant species on the surface of NZVI that could hinder the transport of RB5 and other hydrophilic species. For SO and SL, the inhibition of RB5 and CT reduction might also be explained by the binding of carboxylates to NZVI. The increase in CT reduction rate with SDS and SDP suggests that providing a non-binding lipophilic environment on the surface of NZVI would improve the reduction rate and selectivity towards the reduction of hydrophobic contaminants.

The purification and collection of various products from oil/water mixtures are routine procedures. However, the presence of emulsifiers that can displace other surface active components in the mixtures can significantly influence the efficiency of such procedures. Previously, we investigated interfacial mechanisms of zein protein-induced emulsification and the opposing surfactant-induced demulsification related to corn oil refinement. In this paper, we further investigated a different class of protein, glutelin, inside corn and proved that glutelin acts as an oil/ water emulsifier in an acidic water environment. Furthermore, an extended surfactant's protein disordering and removal ability was tested and compared with a conventional surfactant. An extended surfactant contains a poly(propylene oxide) or poly(propylene oxide)−poly(ethylene oxide) chain inserted between the hydrophilic head and the hydrophobic tail. In this study, a nonlinear optical spectroscopic technique, sum frequency generation (SFG) vibration spectroscopy, was used to study the behavior of glutelin and extended as well as regular surfactants at the corn oil/water or aqueous solution interface. In most cases, the conventional surfactant shows better protein disordering or removal ability than the extended surfactant. However, with the addition of heat and salt to an extended surfactant solution, the experiment resulted in a substantial increase in the extended surfactant's protein disorder or removal ability.