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FOSC302 > Solid-liquid Extraction > Flashcards

Solid-liquid Extraction Flashcards

1
Q

separation techniques

A

centrifugation
distillation
crystallization
filtration
extraction
chromatography
electrophoresis

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2
Q

solid-liquid extraction process

A

-preparation of extraction material
-separation and recovery of the solvent extraction
-separation and recovery of solvent from extraction residual

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3
Q

what is SPE and how does it work

A

solid phase extraction
solubilised material is passed through a solid medium which traps all the unwanted material and purifies the solution

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4
Q

what is raffinate

A

liquid in which impurities have been removed

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5
Q

to improve extraction efficiacy the solvent must be provided with large _______ ________ and ______ ______ pathways

A

exchange surfaces
diffusion pathways

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6
Q

How can large exchange surfaces and short diffusion pathways be achieved

A

pulverising the solid to be extracted

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7
Q

if the solute is ground too small what can happen

A

agglutination occurs
-makes it difficult for solvent to permeate

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8
Q

How can large exchange surfaces and short diffusion pathways be achieved?

A

pulverizing the solid to be extracted

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9
Q

three aspects that make a SCF effective

A

density similar to liquid
diffusion coefficent higher than liquid
viscosity similar to gas

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10
Q

what is solvating power dictated by

A

density
polarity of SCF

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11
Q

how do density and temperature affect power of SCf

A

power increases with density at a given temp
power increases with temp at a given density

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12
Q

what effect does increasing the pressure of SCF

A

higher solubility due to increase density

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13
Q

what can too much pressure do

A

plateau the increase in solubility due to increased viscosity and reduced diffusivity

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14
Q

SCF characteristics

A

low viscosity
diffusion coefficient between liquid and gas
almost no surface tension
small change in P = large density change = higher solvating power

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15
Q

how does an increae in T effect SCF

A

increase dynamic viscosity therefore diffusivity

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16
Q

why id CO2 such a good SCF

A

best diffusivty
lowest viscosity
reasonable density
-cheapish and safe

17
Q

at what point on a phase diagram does a SCF appear

A

after critical point

18
Q

how can the fractionation phase be advantageous for SCF

A

allows unwanted products to be selectively removed
-short-chain fatty acids
-caffeine

19
Q

applications of SCF

A

-extraction of hops
-remove cholesterol from butter
-perfumes and flavours
-residual monomers and solvent from polymer formulations
-unsaturated fatty acids from fish oils

20
Q

temp and P CO2 becomes a SCF

A

31 C
72.9 bar

21
Q

how does the dielectric constant affect SCF

A

affects the solubility of solutes

22
Q

physical properties that change at critical point

A

-partial molar volume of SCF decreases
-thermal conductivity
-heat capacity

23
Q

describe what modifiers of SCF are

A

-molecules that cluster around solute molecules
-used in small amounts
-assist in dissolving polar solutes which are not normally highly soluble in SCF CO2

24
Q

frequently used modifiers

A

methanol
ethanol
propanol

25
Q

what is the hildebrand parameter

A

measures solvating power

26
Q

what does a high hildebrand parameter mean

A

wider range of solutes can be dissolved

27
Q

general rule for hildebrand parameter

A

solubility increases as density and temperature increases

28
Q

if a solute is a liquid where is it drained from?

A

the bottom of the seperator

29
Q

if the solute is a solid how is it drained?

A

extraction is halted and the solute is removed from the vessel

30
Q

describe butterfat fractionation

A

50-60C, 100-250 bar
shorter chains are more soluble in SCF
-requires multiple stages

31
Q

what is rho in equation

A

density

32
Q

________of cholesterol increases as ____ increases but ____________ is reduced

A

solubility
rho
selectivity

33
Q

real world application examples of SCF

A

cholesterol
pepper oil
butterfat fractionation
ginger
jasmine
coffee
seed oil

34
Q

how is pepper oil tradiitonally extracted and how much better is SCF

A

steam distillation of sequiterpenes
normal: 26%
SCF: 39% @ 40C, 49% @ 60C

35
Q

how is jasmine traditionally extracted

A

using ethanol

36
Q

what type of organic solvents are used to decaffeinate coffee beans

A

methylene chloride
trichloroethylene
ethyl acetate

37
Q

why is methyl chloride bad

A

has contirbuted to ozone hole

38
Q

describe the swiss water process

A

soak green beans in hot water
strip caffiene using activated charcoal
re soak beans in water
roast

39
Q

why is de-gumming not required in SCF od seed oils

A

phospholipids are not co-extracted

FOSC302 (14 decks)

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