Hydrophobic oils

Besides the spontaneous, complete wetting for some areas of application, e.g., washing and dishwashing, the rewetting of a hydrophobic component on a solid surface by an aqueous surfactant solution is of great importance. The oil film is thereby compressed to droplets which are released from the surface. Hydrophobic components on low-energy surfaces (e.g., most plastics) are only re wetted under critical conditions. For a complete re wetting of a hydrophobic oil on polytetrafluoroethylene (PTFE) by an aqueous solution, the aqueous solution-oil interface tension must be less than the PTFE-oil interface tension... 

Washing removes the natural coating of protective oil that gives hair its body and shine. To counter this, shampoos and conditioners contain hydrophobic oils that cling to the surface of hair and remain in place upon rinsing. Dimethicone, shown in our inset, is an artificial oil that contains hydrophobic silicon-oxygen chains and methyl groups. 

A surfactant is a molecule that is characterized as amphiphilic, i.e., containing both a discrete hydrophilic (water-soluble) or polar portion and a well-defined hydrophobic (oil-soluble) or nonpolar fragment. The hydrophilic portion of the molecule is called the surfactant headgroup the hydrophobic portion of a surfac-... 

Figure 4.7 Illustration of the removal of hydrophobic oil from a fibre using detergent.

Hydrophobic oil-soluble block copolymers Emulsion AA (Emulfip 102b, IPE202b), for example, made from polyalkenylsuccinic anhydride with monoether of poly (ethylene glycol) typical block copolymer is made from styrene/ethylene/propylene IFP (Gateau et al., 2004)... 

Surfactant-Enhanced Removal of Hydrophobic Oils from Source Zones... 

Key words hydrophobic oils equivalent alkane carbon number (EACN) surfactant-enhanced remediation... 

Oil contaminants can range in both viscosity and molecular weight. The purpose of this work was to find optimal surfactant formulations to extract low viscosity ( ( 100 cp), high molecular weight (hydrophobic) oils. In surfactant formulation it is common to define the oil molecular weight (hydrophobicity) by virtue of its equivalent alkane carbon number (EACN) aka, how many carbons would there be in an alkane oil of equivalent behavior. Thus, since some crude oils behave similarly to hexane, and since hexane has an alkane carbon number of 6, these crude oils also have an... 

EACN of six. We thus define high molecular weight (hydrophobic) oils as having EACN values >10 and low molecular weight oils (hydrophilic oils) as having an EACN of < 6. 

Thus, surfactant enhanced subsurface remediation is a mature technology for remediating hydrophilic NAPL, as displayed at the field level. These successful field demonstrations provide encouragement for further evaluation of hydrophobic oils with a similar goal of field deployment. To this end, the current research evaluated laboratory batch and column studies for surfactant enhanced remediation of hydrophobic oil contamination, including phase behavior studies, column studies, and evaluating separation... 

The hydrophobic oils evaluated in phase behavior studies were diesel, dodecane, and hexadecane. A commercial Diesel was selected based on its occurrence as a subsurface contaminant and its hydrophobicity. Based on... 

Liquid-liquid extraction of hydrophobic oil-laden surfactant solution was evaluated using counter-flow, porous hollow fiber membranes. Our liquid-liquid extraction experiments were conducted using Liqui-Cel Extra-Flow 2.5x8 Membrane Contactor purchased from Celgard LLC (Charlotte, NC). The dimensions of the column are 6.3 cm diameter and 20.3 cm. length with... 

Table III. EACN determination of several multi-component hydrophobic oils.

The objective of this portion of the research was to experimentally evaluate surfactant effects on the liquid-liquid separation of hydrophobic oils from a surfactant system. For pump-and-treat subsurface remediation in the absence of surfactant, contaminated ground water would be pumped from the subsurface and through a liquid-liquid extraction column where the contaminant partitions from the aqueous phase into an extraction solvent phase. In the absence of surfactant, the driving force for partitioning is a function of the contaminant hydrophobicity. In the presence of surfactants, the contaminant is subject to competitive partitioning (i.e., into the micelles and into the extracting oil). 

By maximizing the contact area between extraction solvent and surfactant-solubilized hydrophobic oil contaminant through the use of state-of-the-art hollow fiber membrane columns, we hypothesize that hydrophobic oil contaminants can be separated from surfactant solutions without macroemulsification. For this research we were interested in the partitioning of the hydrophobic oil from the hydrophobic environment of the micelle via its aqueous concentration into a more preferred extracting solvent. 

SDBS/IPA would have worked for diesel, as was observed experimentally. Neither SDBS/IPA nor AMA/IPA is predicted to exhibit the classical Winsor phase type I <=>III<=>II progression for either the multi-component hydrophobic oils of Hill OU1 or commercial motor oil, both of which exhibited EACNs greater than diesel (Table IV). 

Research on separation processes demonstrated that hydrophobic oilladen surfactant was efficiently regenerated through the use of state-of-the-art hollow fiber membrane columns. Specifically, the hydrophobic oil dodecane was effectively separated from the surfactant system SDBS/IPA/NaCl (Table VI). This separation was accomplished by counterflowing the oil/surfactant solution, comprised of 10.3 ml. dodecane per 100ml. of SDBS/IPA/NaCl solution, with the extraction solvent squalane. These results demonstrate the ability to effectively regenerate and reuse these surfactant systems. 

In summary, research reported in this chapter illustrates not only the complexity of surfactant enhanced remediation of hydrophobic NAPLs, but also demonstrates the ability of properly designed surfactant systems to effectively remediate these hydrophobic oils (EACN of 10-20). Future research will further evaluate this area, including field studies. This research also explored surfactant systems for attacking even more hydrophobic, low viscosity NAPLs (EACNs)20). Addressing the highly hydrophobic oils (EACNs))20) and highly viscous oils may require combined approaches, (i.e., surfactants plus alcohols/solvents and/or temperature) such will also be the focus of future research. 

Clays disperse easily in water, but not with hydrophobic oils. They are particularly suited for use with the hydrolats. 

The rate of Ostwald ripening depends on the size, the polydispersity, and the solubility of the dispersed phase in the continuous phase. This means that a hydrophobic oil dispersed as small droplets with a low polydispersity already shows slow net mass exchange, but by adding an ultrahydrophobe , the stability can still be increased by additionally building up a counteracting osmotic pressure. This was shown for fluorocarbon emulsions, which were based on perfluo-rodecaline droplets stabilized by lecithin. By adding a still less soluble species, e.g., perfluorodimorphinopropane, the droplets stability was increased and could be introduced as stable blood substitutes [6,7]. 

It was found that the nanocapsules are formed in a miniemulsion process by a variety of monomers in the presence of larger amounts of a hydrophobic oil. Hydrophobic oil and monomer form a common miniemulsion before polymerization, whereas the polymer is immiscible with the oil and phase-separates throughout polymerization to form particles with a morphology consisting of a hollow polymer structure surrounding the oil. The differences in the hydro-philicity of the oil and the polymer turned out to be the driving force for the formation of nano capsules. 

The synthesis of nanocapsules can best be obtained in miniemulsion using different approaches [107], One possibility is based on the phase separation process within a droplet during the polymerization [108], Here, vinyl monomers were polymerized in the presence of a hydrophobic oil. During the polymerization, the polymer becomes insoluble in the oil, leading to a phase separation. With properly chosen physicochemical properties of monomer and encapsulated material, a polymeric shell surrounding the liquid core can be formed. 

Gel emulsions were applied successfully for the first time in aldol additions of DHAP to phenylacetaldehyde and benzyloxyacetaldehyde as model aldehydes catalyzed by RAMA [24]. The first interesting observation was that the stability of RAMA in water-in-oil gel emulsions improved by 25-fold compared to that in dimethylformamide/water l/4v/v co-solvent mixture. The reported experimental data concluded that both the highest enzymatic activities and equilibrium yields were observed in water-in-oil gel emulsion systems with the lowest water-oil interfacial tension attained with the most hydrophobic oil component (i.e. tetradecane, hexadecane, and squalane). 

Because nonpolar alkanes are not water soluble, crude petroleum spilled into the sea from a ruptured oil tanker creates an insoluble oil sUck on the surface. The insoluble hydrocarbon oil poses a special threat to birds whose feathers are coated with natural nonpolar oils for insulation. Because these hydrophobic oils dissolve in the crude petroleum, birds lose their layer of natural protection and many die. 

In an inverse emulsion polymerization, an aqueous solution of a hydrophilic monomer is emulsified in a continuous hydrophobic oil phase using a water-in-oil emulsifier. The polymerization is initiated with either oil-soluble or water-soluble initiators. Figure 2 shows a schematic representation of this system. The formation of micelles is uncertain, but is portrayed speculatively. The hydrophilic part of the emulsifier molecule is oriented toward the hydrophilic dispersed phase and the hydrophobic part toward the hydrophobic continuous phase. The initiation of polymerization proceeds by a mechanism analogous to that of the conventional system and submicroscopic particles of water-swollen hydrophilic polymer are generated in the continuous oil phase. 

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