Solid-liquid Extraction Flashcards
separation techniques
centrifugation
distillation
crystallization
filtration
extraction
chromatography
electrophoresis
solid-liquid extraction process
-preparation of extraction material
-separation and recovery of the solvent extraction
-separation and recovery of solvent from extraction residual
what is SPE and how does it work
solid phase extraction
solubilised material is passed through a solid medium which traps all the unwanted material and purifies the solution
what is raffinate
liquid in which impurities have been removed
to improve extraction efficiacy the solvent must be provided with large _______ ________ and ______ ______ pathways
exchange surfaces
diffusion pathways
How can large exchange surfaces and short diffusion pathways be achieved
pulverising the solid to be extracted
if the solute is ground too small what can happen
agglutination occurs
-makes it difficult for solvent to permeate
How can large exchange surfaces and short diffusion pathways be achieved?
pulverizing the solid to be extracted
three aspects that make a SCF effective
density similar to liquid
diffusion coefficent higher than liquid
viscosity similar to gas
what is solvating power dictated by
density
polarity of SCF
how do density and temperature affect power of SCf
power increases with density at a given temp
power increases with temp at a given density
what effect does increasing the pressure of SCF
higher solubility due to increase density
what can too much pressure do
plateau the increase in solubility due to increased viscosity and reduced diffusivity
SCF characteristics
low viscosity
diffusion coefficient between liquid and gas
almost no surface tension
small change in P = large density change = higher solvating power
how does an increae in T effect SCF
increase dynamic viscosity therefore diffusivity
why id CO2 such a good SCF
best diffusivty
lowest viscosity
reasonable density
-cheapish and safe
at what point on a phase diagram does a SCF appear
after critical point
how can the fractionation phase be advantageous for SCF
allows unwanted products to be selectively removed
-short-chain fatty acids
-caffeine
applications of SCF
-extraction of hops
-remove cholesterol from butter
-perfumes and flavours
-residual monomers and solvent from polymer formulations
-unsaturated fatty acids from fish oils
temp and P CO2 becomes a SCF
31 C
72.9 bar
how does the dielectric constant affect SCF
affects the solubility of solutes
physical properties that change at critical point
-partial molar volume of SCF decreases
-thermal conductivity
-heat capacity
describe what modifiers of SCF are
-molecules that cluster around solute molecules
-used in small amounts
-assist in dissolving polar solutes which are not normally highly soluble in SCF CO2
frequently used modifiers
methanol
ethanol
propanol
what is the hildebrand parameter
measures solvating power
what does a high hildebrand parameter mean
wider range of solutes can be dissolved
general rule for hildebrand parameter
solubility increases as density and temperature increases
if a solute is a liquid where is it drained from?
the bottom of the seperator
if the solute is a solid how is it drained?
extraction is halted and the solute is removed from the vessel
describe butterfat fractionation
50-60C, 100-250 bar
shorter chains are more soluble in SCF
-requires multiple stages
what is rho in equation
density
________of cholesterol increases as ____ increases but ____________ is reduced
solubility
rho
selectivity
real world application examples of SCF
cholesterol
pepper oil
butterfat fractionation
ginger
jasmine
coffee
seed oil
how is pepper oil tradiitonally extracted and how much better is SCF
steam distillation of sequiterpenes
normal: 26%
SCF: 39% @ 40C, 49% @ 60C
how is jasmine traditionally extracted
using ethanol
what type of organic solvents are used to decaffeinate coffee beans
methylene chloride
trichloroethylene
ethyl acetate
why is methyl chloride bad
has contirbuted to ozone hole
describe the swiss water process
soak green beans in hot water
strip caffiene using activated charcoal
re soak beans in water
roast
why is de-gumming not required in SCF od seed oils
phospholipids are not co-extracted
