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Lecture Notes 5

Lecture Notes 5 - Concept Question(s for filtration series...

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Concept Question(s) for filtration –series B
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V max lab testing 2 Use authentic feed stream and filter. Do linear least squares fit to data. Can end test when filtrate flowrate falls to ¼ or ½ of initial value = faster testing with less volume. t / V (hr/L) t (hr) y-intercept = J i lab
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Some photomicrographs of UF and MF membranes Asymmetric UF membranes = higher flux + mechanical strength 3 Lumen (interior) of hollow fiber UF membrane. Lumen diameter is 100 -1000 um Surface of a polysulfone hollow-fiber MF membrane. Surface pore diameter is 0.2–0.4 mm.
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Concept Question 1 – Molecular weight cutoff Your bioprocess uses ultrafiltration to concentrate a recombinant hemoglobin solution (MW = 65000 Da) by 10X, and then diafilter it to remove > 99 % of the EDTA (MW = 400 Da), in the starting solution. Based on the figure below, which UF membrane do you select for your process? On the graph, R refers to the rejectivity of the membrane for a solute, where R = (solute conc in feed – solute conc in permeate) / solute conc in feed Note: 0 R 1 MW of test dextran R 0.9 1.0 0.1 0.0 0.3K 1K 3K 10K 30K 100K 300K A B C D E
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Answer to Q1 – B or C B and C both appear to retain hemoglobin (65 kDa) to a very high degree, necessary for a low yield loss. B and C also allow the 0.4 kDa EDTA to leave with minimal rejection by the membrane, necessary for the diafiltration to be effective at removing the EDTA. A retains too much EDTA D and E fail to retain hemoglobin well enough. MW of test dextran R 0.9 1.0 0.1 0.0 0.3K 1K 3K 10K 30K 100K 300K A B C D E
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6 Rejectivity of real UF membranes is a “band” not a single line MW of test dextran R 0.9 1.0 0.1 0.0 0.3K 1K 3K 10K 30K 100K 300K
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Concept Question 2 – Diafiltration Diafiltration (DF) removes small solutes from a solution using a UF membrane, while maintaining a constant solution volume. Pick the operating line that best describes how the concentration, C, of a freely sieving solute (rejectivity, R = 0) will change as DF proceeds. (In the graph, C 0 is the solute conc at the start of DF. )
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Ans to Question 2 = B For the ideal case where R = 0, the DF operating line obeys the simple equation: ln(C/C 0 ) = - N . So, when N = 1, ln(C/C 0 ) = -1; when N=2, ln(C/C 0 ) = -2 ; and so forth.
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Concept Question 3 – Non-ideal Diafiltration Pick the operating line that best describes how the concentration of a partially rejected solute with rejectivity, R = 0.1 will change as DF proceeds.
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Ans to Question 3 = C For the non-ideal case where a solute is partially rejected, R > 0 , the DF operating
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Lecture Notes 5 - Concept Question(s for filtration series...

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