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The addition of specific phospholipids to chocolate was recently shown to direct the crystallization of cocoa butter to the desirable triclinic form V polymorph, thus achieving the most desirable crystal structure in chocolate without the need for shear or complex temperature gradients. However, the mechanism of action of these phospholipids remains unknown. Herein, we determined the structure of self-assembled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in chocolate and its fat phase, cocoa butter, to better understand its effects on the crystallization behavior and polymorphism of cocoa butter. Small-angle neutron scattering studies suggested that DMPC forms a variety of micelles in cocoa butter. A strong interaction between the DMPC micelles and the triglyceride palmitoyl-oleoyl-stearoyl glycerol (POS), the most abundant triglyceride in cocoa butter, which also directs the triclinic crystallization of the cocoa butter, was also observed by small-angle X-ray scattering (SAXS), interfacial tension measurements, and attenuated total reflectance-fourier transform infrared spectroscopy. This suggested that DMPC micelles serve as a seeding surface, templating form V crystal growth via its effects on POS. We propose a mechanism that involves a solid-state polymorphic transition form IV to V POS in the seeding crystals. Crystal strain and defects were observed in the templated nano- and microstructure observed by synchrotron microcomputed tomography and SAXS. These could affect the product’s properties, suggesting that a simple tempering step may still be required.

The water pollutant diisopropylamine (DIPA) creates surfactantless emulsions in water. DIPA droplets bear a negative electrostatic charge, as demonstrated by electrophoretic measurements. Sodium salts (NaCl and Na2SO4) decrease their charge, leading to droplet coalescence and separation into bulk layers, depending on the salt and DIPA percentages. Attenuated total reflectance – Fourier transform infrared spectroscopy (ATR-FTIR) show that the DIPA concentration in the water rich phase is below 10 wt% DIPA when adding 2 wt% Na2SO4(relative to the mixture) to mixtures of 20 wt%, 40 wt% and 50 wt% DIPA (relative to water). The same occurs when adding 2% NaCl to mixtures of 30 wt%, 50 wt% and 70 wt% DIPA (relative to water). DIPA-water mixtures are electrically conductive and can be separated by subjecting them to an electric field (electrokinetic separation). Without salts, the concentration of DIPA in 30 wt% DIPA could be reduced by ≈ 20 wt% after 60 mins treatment using a differential voltage = 12 V. NaCl (0.25 wt% relative to water) improved efficiency. After 15 mins, the percent decrease in DIPA was ≈ 50 wt%. Electrokinetic treatment targets exclusively contaminants dispersed in water. DIPA sorbs onto clay, alumina and iron oxide minerals, whereas it does not sorb onto gypsum and limestone. Therefore, the in situ electrokinetic separation of DIPA can be most successfully applied in aquifers where the dominant minerals are gypsum and limestone.

Fracking is an enhanced oil recovery technology, which uses viscoelastic fluids (fracking fluids) to fracture oil reservoirs and to transport sand within the fractures, to prop them open. This technology enables oil recovery from scarcely permeable formations. Fractured formations release saline water over time. This saline water (called “produced water”) is discarded rather than used to produce fracking fluids because it can decrease fracking fluid viscosity. Nonetheless, it would be advantageous to use produced water to reduce freshwater consumption and wastewater production. Our study analyzes the effect of chloride salts (CaCl2, MgCl2, and Fe(III)Cl) and of sulfate salts (MgSO4and FeSO4) at different concentrations (0.05–1 M) on the viscosity of aqueous guar solutions. All chloride salts tested increase the viscosity of guar solutions in the concentration range analyzed and promote the formation of small guar aggregates. At 0.05 M concentrations, MgSO4has effects similar to chloride salts. In contrast, 1 M MgSO4decreases the viscosity of guar solutions. FeSO4also decreases the viscosity of aqueous guar solutions, at either 0.05 or 1 M concentrations. The decrease in viscosity of guar solutions is attributed to large guar aggregate formation (as opposed to a cohesive network). Sodium cocoyl glutamate (SCG) increases the viscosity of non-cross-linked guar solutions and the shear viscoelastic moduli of guar solutions cross-linked with sodium tetraborate. Specifically, SCG restores the viscosity of guar solutions with MgSO4and increases it above values measured in deionized (DI) water in the presence of MgCl2. Attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy shows that hydrogen bonding was more significant in guar + SCG + 0.7 M MgCl2samples than in guar + SCG + 0.7 M MgSO4, indicating that the formation of a hydrogen-bonded network was correlated to high viscosity. ATR-FTIR also indicates that MgSO4weakened hydrogen bonding of water clusters, whereas SCG restored it, enabling guar hydration even in the presence of MgSO4. Our study highlights which salts are most problematic (e.g., FeSO4) and proposes a potential additive (SCG) to enhance the viscosity of guar in the presence of selected salts (e.g., magnesium salts) by promoting hydrogen bonding.

Nonaqueous phase liquids (NAPL, e.g., hydrocarbons and chlorinated compounds) are common groundwater pollutants. Electrokinetic remediation of NAPLs uses electric fields to draw them toward electrodes and remove them from groundwater. The treatment requires NAPL mobility. Emulsification increases mobility, but at a risk for downstream receptors. We propose using alkaline aqueous solutions of zein and graphene nanoparticles (GNP) to form conductive materials, which could also act as barriers to control NAPL migration. Alkaline zein–GNP solutions can be injected in the polluted soil and solidified by neutralizing the pH (e.g., with glacial acetic acid, GAA). Shear rheology experiments showed that zein–GNP composites were cohesive, and voltammetry showed that GNP increased electrical conductivity of zein-based materials by 3.5 times. Gas chromatography–mass spectroscopy (GC–MS) demonstrated that the electrokinetic treatment of model sandy aquifers yielded >60% and ∼47% removal of emulsified toluene in freshwater and in salt solutions, respectively (with 30 min treatment using a 10 V differential voltage between a zein–GNP and an aluminum electrode. NaCl was used as model salt contaminant. The conductivity of surfactant solutions was lower in saline water than in freshwater, explaining differences in toluene removal. Toluene–water emulsions were stabilized using the natural surfactants lecithin and saponin. These surfactants acted synergistically in stabilizing emulsions in either freshwater or salt solutions. Lecithin and saponin likely interacted at toluene–water interfaces, as indicated by the morphology, interfacial tension and compressional rigidity of toluene–water interfaces with both components (relative to interfaces of either lecithin or saponin alone). The compressional behavior of interfacial films was well-described by the Marczak model. Electrokinetic treatment of saturated model sandy aquifers also decreased the turbidity of emulsions of water and either tricholoroethylene (TCE, by ∼41%) or diesel (by ∼75%), in the presence of a bacterial biosurfactant. This decrease was used as semiquantitative indicator of NAPL removal from water.

A novel sorbent material consisting of a gel made from canola oil and water, emulsified with lecithin, was used to remove two model solvents from water. Sorption capacity was quantified through small-scale batch experiments. The structure and the mechanical properties of the gel were compared with and without added solvent to assess their cohesiveness upon removing contaminants from water. Confocal microscopy showed that the initial gel consisted of water droplets clustered in a canola oil continuous phase. The G′ of the gels increased with solvent absorption to a maximum at 33% (v/v) hexane or 24% (v/v) toluene. Larger absorbed volumes led to decreases in G′ of the gel. G′ for solvent mixtures of 50% toluene and 50% hexane was intermediate between G′ measured for the same volumes of pure solvents. Confocal microscopy suggests that the decrease of G′ upon addition of large solvent volumes was due to a simple dilution effect. It is hypothesized that the initial increase in storage modulus was caused by changes in the structure of the lecithin films formed at the oil–water interfaces. This hypothesis was evaluated through measurements of interfacial tension, visualization of the interface with optical microscopy, force measurements of a single droplet under compression using a cantilevered-capillary force apparatus, compressional isotherm measurements conducted using a Langmuir trough. The cantilevered-capillary force apparatus and Langmuir trough experiments demonstrated that lecithin films at the canola oil–water interface were rigidified by toluene and hexane addition.

Tetrahydrofuran (THF) and water are miscible and interact trough hydrogen (H) bonds. Span 80 (sorbitan ester) is soluble in THF, but not water. Nonetheless, Span 80 H bonds with water, as shown by attenuated total reflectance – Fourier transform infrared spectroscopy. In pure water, species are single (SD) or double (DD) donors, and single (SA) or double (DA) acceptors. In pure water, SD-SA and DD-DA are dominant and have similar abundance. Span 80 and THF alter the distribution of water species. When THF and Span 80 compete for the same water species, THF separation from water is most effective. Span 80 induces a marked shift of SD-SA to higher wavenumbers, which are close to DD-DA. This species intermediate between DD-DA and SD-SA is dominant, indicating that Span 80 mainly interacts with it. This same species is also dominant in THF-water mixtures containing 50–70% THF. Instead, DD-DA is dominant up to 40% THF, while DD-SA dominate at the highest THF percentages. Bottle tests show that Span 80 separates THF and water into bulk phases with 50–70% THF within 1 hr. In contrast, outside this THF range, emulsions are stable for more than 1 hr, as observed by either light scattering or optical microscopy. In mixtures with 50–70% THF, bulk phase separation occurs within 1 hr, because Span 80 competes with THF for the same water species. Separation is poorer outside of this THF range, where Span 80 and THF interact with different water species.

Rhamnolipids are bacterial amphiphiles. In addition to emulsifying hydrophobic solvents, they affect the phase behaviour of miscible solvents. In mixtures of toluene and water, rhamnolipids mediate the migration of metal ions (e.g., iron and copper) from the water to the toluene phase. Also, rhamnolipids phase separate the miscible solvent tetrahydrofuran (THF) from water, yielding emulsions even in the absence of toluene. This is because they compete with THF for hydrogen (H) bonding with similar water species. Water is an ensemble of species, including single donors (SD) or double (DD) donors, and single acceptors (SA) or double (DA) acceptors. In pure water, SD-SA and DD-DA have similar abundance and are dominant, as shown by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). With 50–200 g/L rhamnolipids, a water species intermediate between SD-SA and DD-DA is dominant, indicating that rhamnolipid-water interactions mainly occur through this species. This same species primarily interacts with THF, at 50–80% THF. At lower THF percentages, a similar (albeit not identical) species dominates, namely DD-DA, explaining separation. Emulsions are THF in water, as demonstrated by synchrotron mid-infrared spectro-microscopy and confocal microscopy using a hydrophobic dye. Synchrotron small angle X-ray scattering (SAXS) showed that rhamnolipids self- assemble into micelles, which contain THF. These findings have potential implications for miscible pollutant migration in groundwater, and their toxicity to rhamnolipid-secreting bacteria.

Oxidizing emulsifiers were produced using calcium peroxide and polysaccharides extracted from edible mushrooms. The polysacchardes were mainly glucans, as indicated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Our study investigates the potential application of these oxidizing emulsifiers to remediate and immobilize spills of a model hydrocarbon (toluene) in groundwater. Interfacial tension measurements showed that the oxidizing emulsifiers adsorbed at toluene-water interfaces, producing rigid interfacial films (as demonstrated through Langmuir trough experiments). The oxidizing emulsifiers were particle-like, as observed with scanning electron microscopy (SEM). Emulsification tests and optical microscopy observations showed that the oxidizing emulsifiers stabilized water in toluene emulsions, hence promoting contact between the emulsifying oxidizers and toluene. Therefore, toluene degradation was greater with the oxidizing emulsifiers than with calcium peroxide (used at the same concentrations), as demonstrated through gas chromatography-mass spectroscopy (GC-MS) experiments. Shear rheology tests showed that the water in toluene emulsions stabilized by the oxidizing emulsifiers were gel-like. The gelation of hydrocarbon spills would be useful to immobilize hydrocarbon spills during their remediation, thereby impeding their unwanted migration. Our study describes for the first-time emulsifying oxidizers, which have the potential to enhance the remediation of hydrocarbon spills (compared to traditional oxidizers), while safely immobilizing them.

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