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Solid-Liquid Extraction
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Introduction
• Defnition: Methods o removing oneconstituent rom a solid by means oa liquid solvent
• !enerally also "no#n as leaching$lixiviation or #ashing
• %idely used #hen thermal ormechanical method is not &ossible
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Introduction
• Solid liquid extraction &rocedures includes – 'ontact a&&ro&riate solvent to transer the
soluble constituent into solvent
–Se&aration and #ashing o solution rom theresidual solid
• Exam&les: – Extraction o sugar rom sugar beets
– Extraction o oil rom oil bearing seeds
– Extraction o coconut mil" rom coconut
– Extraction o oil rom soy bean (a"es
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'om&arison )et#een LLEand SLE
• *igure +: Liquid-Liquid Extraction
• *igure ,: Solid Liquid Extraction
Source: htt&:..###guntde.do#nload.extraction/english&d
http://www.gunt.de/download/extraction_english.pdfhttp://www.gunt.de/download/extraction_english.pdf
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Equi&ments used orextraction
• Se&arator *unnel
• Soxhlet Extractor
*igure 0: *igure 1:
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• )ollman Extractor
• 2otocel Extractor
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'345I4636S '3645E2'622E45LE7'8I4!
• 5he solid is not moved &hysically rom stage to stage
• 5he liquids is being moved rom stage to stage
*igure:9: 'ountercurrent leaching &rocess
; &hase < the liquid &hase =rom stage 4 to stage +>
L &hase < the liquid carried #ith the solid =rom stage + tostage 4>
Exhausted solids leave Stage 4
'oncentrated solution over(o# rom Stage +
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'345I4636S '3645E2'622E45LE7'8I4!
• Solution retained by entering solid$ x a
• Solution retained by leaving solid$ x b
• Fresh solvent entering the system$ y b
• Concentrated solution leaving the system$ y a
Equilibrium 2elationshi&• Equilibrium is attained #hen the solute is com&letely dissolved
and the concentration o the solution so ormed is uniorm
• 5he concentration o the liquid retained by the solid leavingany stage is the same as that o the liquid over(o# rom thesame stage
• 5he equilibrium relationshi& is sim&ly x b= y.
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3&erating line
• 6se Mc'abe 5hiele Method i the o&eratingline is straight
• In leaching$ the o&erating line is al#ays
straight• 5he equilibrium line is on 19oline
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Exam&le:
3il is to be extracted rom meal by means o ben?eneusing a continuous countercurrent extractor 5he unit isto treat +$@@@ "g o meal =based on com&letely
exhausted solid> &er hour 5he untreated meal contains1@@ "g o oil and is contaminated #ith ,9"g oben?ene 5he resh solvent mixture contains +@"g o oiland A99 "g o ben?ene 5he exhausted solids are tocontain A@"g o unextracted oil Ex&eriments carried
out under conditions identical #ith those o the&roBected battery sho# that the solution retainedde&ends on the concentration o the solution$ as sho#nin the ollo#ing table
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Concentration, kgoil/kg
solution
Solutionretained,
kg/kg solid@ @9
@+ @9@9@, @9+9@0 @90@1 @99@9 @9C+@A @99
@C @A,
*ind:=a> the concentration o thestrong solution$ or extract=b> the concentration o the
solution adhering to the
extractedsolids=c> the mass o solution
leaving #ith the extractedmeal=d> the mass o extract
=e> the number o stagesrequired7ll quantities are given onan hourly basis
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Solution:
Let x and y be the mass ractions o oil in the under(o# and
over(o# solutions 7t the solvent inlet$
Determine the amount and com&osition o the solution in thes&ent
solids by trial I x b= 0.1$ the solution retained$ rom 5able$
is @9@9 "g."g 5hen
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Solution:
*rom 5able $the solutionretained is @9@C "g."g:
)en?ene in the under(o# at Lb
is 9@C - A@ < 11C "g.h7t the solid inlet$
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Solution
e> Determine the inlet and exit concentrations or the frststage and locate the o&erating line or the remainingstages
Since x+ < ya< @A@$ solution retained is @99 "g."g solid
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5he &oints xn $ xnF+ $xa $ ya and xb$ yb defne a slightlycurved o&erating line
*our ideal stages are required