Microemulsion: An Alternate Technology in

Oil Extraction

By

Ashish Gadhave

•Introduction»Conventional Oil Extraction Method»Microemulsion

Conventional Oil Extraction • Water Distillation, Steam Distillation, Solvent

Extraction, Physical Pressing etc.

• In solvent extraction method, organic solvents (mostly hexane) is preferred.

• Solvent is then recovered after separating the oil by evaporation

Disadvantage of Conventional Methods

• High temperature destroys protein, vitamin E etc.• Lowering temperature (cold pressing) decreases yield

and increases cost.• According to US EPA, Organic compounds are major

emission from vegetable oil industries.• 0.8Kg of hexane per ton of seed is emitted.• Complete removal of hexane is not possible.• Health Problem: Atrophy, nerve damage, muscle

wasting.• Alternate methods need to be developed.

Microemulsion

• A system consisting of oil, water and amphiphile (surfactant+co-surfactant), in liquid state, having thermodynamic stability and isotropic property.

• The key differences between microemulsion and macroemulsion is given in Next Slide.

1) Macroemulsion

Thermodynamically UnstableD= 1.5-100µmOptically Opaque

2) Nanoemulsion

Thermodynamically UnstableD= 10-100 nmTransparent or slightly turbid

3) Microemulsion

Thermodynamically StableD= 3-50 nmTransparent or slightly turbid

Property Microemulsion Macroemulsion

Appearance Transparent Cloudy

Interfacial Tension Ultra Low High

Optical Isotropy Isotropic Anisotropic

Structure Dynamic Static

Droplet Size 3-50nm 1.5-100 µm

Stability Thermodynamically Stable

Unstable

Phases Monophasic Biphasic

Viscosity Low High

Main Components of Microemulsion

• Oil: swells the tail of surfactant.Short chain oils have higher ability to swell the

surfactant than long chain oils. Swelling the tail group lessens the HLB value.

• Surfactant:Lowers the interfacial tension.Produces suitable curvature at interfacial area.HLB< 10 W/O emulsion.HLB>10 O/W emulsion.

Continue…

• Co-surfactant:Polar head group with short alkyl chain.Lowers interfacial tension below CMC.Acts as a spacer between surfactant molecules.e.g. Pentanol, Hexanol etc.

Cross sectional representation of a spherical O/W microemulsion droplet.

Microemulsion Classification

Winsor IO/W microemulsionSurfactant solubilized in water phase

Winsor IIW/O microemulsionSurfactant preferably solubilized in

oil phase

Winsor IIISurfactant rich middle phase

combines with both water and oil

Phase Diagram Study

Role of Microemulsion in Oil Extraction

Principle of microemulsion in oil extraction

• Microemulsion acts as a small vessel for conducting reaction.

• Capacity to solubilize oil and water soluble compounds.

• The extraction of oil from oilseeds by microemulsion (water/surfactant/co-surfactant) system involves solubilization and incorporation of oil into the micelles and builds oil-in-water microemulsion.

Continue…

• Water is the continuum phase.• Oil becomes trapped in the hydrophobic core of

the micelles.• Extent of extraction can be determined by phase

diagram.• When ambient conditions are not favorable for

microemulsion formation by using only extended surfactants, linkers could be incorporated in the system along with them to give better results.

Importance of Linkers

• Linkers help to reduce interfacial tension drastically.

• Facilitate microemulsion formation and hence oil extraction.

• Lipophilic linkers (unlike co-surfactants) segregate near the surfactant tail.

• Hydrophilic linker (short hydrophobe and strong hydrophile) absorb partially to surfactant and expand interfacial area.

Continue…

• Both linkers self-assembled at the interface.

• Surfactant like properties.

• Can replace expensive surfactant.

• Increases the extent of extraction of oil.

Extraction Efficiency

Oil Extracted Microemulsion based on

Linkers/Extended Surfactant

Conclusion

Hexadecane (as a model oil) from

cotton fabric

Surfactant+Linkers Hexyl polyglucoside,

Sorbitan monoleate

Linkers based microemulsion are potential substitute

for VOCs

Corn Oil Extended Surfactant

Sodium linear-alkyl polypropoxylated polyethoxylated

sulfates

>80% extraction with only 0.4%

surfactant

Peanut oil Extended Surfactant

Rhamnolipid, Sophorolipid,

Sodium bis(2-ethyl) dihexyl

sulfosuccinate (SBDHS)

Single step extraction for

10mins with 95% efficiency.

Palm kernel oil Extended surfactantComperlan KD,

Alfaoterra 145-5PO 92% oil extraction

Advantages of Microemulsion• Process avoids use of any hazardous organic solvents for oil

extraction; hence it is a ‘Clean Approach.’• Efficient at room temperatures.• Low surfactant concentrations needed to achieve high

efficiencies.• Less process (extraction) time.• Simultaneous recovery of oil and protein is possible with low

initial costs.• Evaporation is replaced by centrifugation for oil-solvent

separation, therefore decreasing the operating cost to a large extent. Good quality oil without any burnt flavor which is present in solvent extracted product as a result of heating.

Some Important References• Control Of Volatile Organic Emissions From Manufacture Of

Vegetable Oils, EPA-450/2-78-035, U. S. Environmental Protection Agency, Research Triangle Park, NC, June 1978.

• Aboofazeli R, Lawrence CB, Wicks SR, Lawrence MJ (1994) Investigations into the formation and characterization of phospholipid microemulsions III. Pseudo-ternary phase diagrams of systems containing water-lecithin-isopropyl myristate and either an alkanoic acid, amine, alkanediol, poly ethylene glycol alkyl ether or alcohol as co-surfactant. Int J Pharma 111: 63-72.

• Witthayapanyanon A, Do L, Acosta EJ, Harwell JH, Sabatini DA (2005) Advanced microemulsion for solvent replacement. 229th ACS National Meeting. San Diego. CA. United States. IEC-072.

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