Probs in Med

BMED%2210%Conservation%Principals%in%Biomedical%Engineering%
Name:%_______________________________%
Spring%2013,%Quiz%4%%%%
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Instructor:%Botchwey%
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1.% To%generate%the%biodegradable%polymer,%poly%(lacticLcoLglycolic%acid)%(PLGA),%a%continuous%production% method% is% used% including% an% aluminum% isopropoxide% catalyst.% % Since% the% catalyst% is% potentially% toxic% to% human% cells,% it% needs% to% be% rinsed% from% the% polymer% solution.% After% processing,% the% polymer% stream% is% washed%into% a%single%wash%unit% with%the%solvent%methylene%chloride.%% Assume%the%unprocessed%polymer% solution%contains% 40.0%wt%%polymer,%10.0%wt%%catalyst,%and% 50.0%wt%%solvent.%Assume%also%that% 80%%of% the% catalyst% fed% to% the% unit% leaves% in% the% waste% solution% (which% contains% only% solvent% and% catalyst),% and% that% the% catalyst% concentration% in% the% waste% solution% is% the% same% as% the% catalyst% concentration% in% the% product%stream.%The%unit%is%operated%such%that%the%output%stream%has%65.0%wt%%polymer.% %
A. Draw%the%system%used%in%the%purification%of%PLGA.%
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B. Write% a%mass%conservation%equation%for%each%of%the%three%constituents%(solvent,%catalyst,%polymer)% in%the%system.% %
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C. Determine%mass%flow%rates%and%weight%percent%of%the%three%constituents%in%each%stream.%
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2.#Based#on#your#answer#in#question#1,#design#a#new#system#involving#2#wash#units#placed#in#sequence#to# further# reduce# the# mass# of# catalyst# in# the# recovered# polymer# stream.# The# system# should# operate# such# that#there#is#a#reduction#of#an#order#of#magnitude#(factor#of# 20)#in#the#wt%#of#catalyst# in#the#recovered# polymer#stream#after#processing#by#the#second#wash#unit.#Assume#the#product#stream#leaving#wash#unit# 2#has#90.0#wt%#polymer.##
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A. What#is#the#catalyst#weight#percent#in#the#final#outlet#polymer#product#stream?##
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