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Homework Help: Continous liquid-liquid extraction

  1. Feb 23, 2010 #1
    I have just done the lab and quite not sure how to do the write-up. Can any1 give me methods? I am planning to go with intro, procedure, basic diagram of a 3-stage mixer settlers modelling, mass balances, titrattion results (which part should I write the problem statement), observations, discussion, errors and improvements.

    My problem statement says;
    1) given x-y diagram reflecting partition coeeficient is not constant varies with ceoncentration. (we can use graph)

    2) objective to determine the way in which overall extraction efficiency of the 3-stage extraction is affected by degree of mixing. (To my understanding, degree of mixing is less mixed, more mixed, as speed of stirrer increases, mixing increases, reaching equilibrium faster). I think this is correct but clarifications, advice greatly appreciated.

    3) Calculate the significance of residence time in the system and make an estimate as to how long the cascade should be left to reach steady state. (This is done by a mass balance but I don't know how) CONFUSED!

    The raffinate is water, extract is kerosene and propoinic acid. Basically, propoinic aicd is extracted from kerosene via passing through 3 mixer settler stages.

    For titration, 1st part; kerosene feed titrated against NaOH solution (0.2M) using phenolphthalein as indicator. Better to add 10cm3 volume of water to kerosene and agitate it but why do we do this? Also the pippetes we used were 10cm^3.

    Once steady state has reached, titrate the aquous extract(comprimise of what, water/propoinic acid) and kerosene raffinate against caustic soda solution (0.02 mola for product kerosene phase, 0.2 molar for feed water n kerosene pahse). Ok so now I'm confused. "

    Kerosene raffinate is not equal to water abd kerosene phase or is it?" Help.

    These will enable me to draw operating line ( i know how) but how do I get the equilibrium line? Perform mass balance on proipionic acid to check steady state has reached. How do I do that?

    Finally, take samples of both phases, kerosene top phase, water bottom phase from 1 and 2 settler units and titrate these to find actual coditions in these satges (what are the conditions?)

    You can see I'm clueless. After I solve this, I can plot operating line and go on with my lab report.

    YOur help is greatly appreicated.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
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