Distribution Ratio and Percent Extraction
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Questions and Answers

What is the distribution ratio D of Cu in the given system?

  • 6/8
  • 6 (correct)
  • 1/6
  • 0.17

    • What is the percentage extraction of Cu in the given system?

  • 80%
  • 25%
  • 75% (correct)
  • 50%

    • What is the mass balance equation for multistage extraction?

  • Vo yn+1 = Va xn - Va xo
  • Va xn + Vo y1 = Va xo + Vo yn+1
  • Va xo + Vo yn+1 = Va xn + Vo y1 (correct)
  • Va xo = Vo yn+1 + Va xn

    • What is the assumption made in deriving the operating line equation?

    <p>yn+1 = 0 and xn = 0</p> Signup and view all the answers

    What is the equation for the fraction remaining after n stages of extraction?

    <p>xn / xo = (E - 1)^n</p> Signup and view all the answers

    What is the graphical procedure used to analyze multistage extraction systems?

    <p>McCabe-Thiele Diagram</p> Signup and view all the answers

    What is the definition of the extraction factor E?

    <p>E = D × (Vo / Va)</p> Signup and view all the answers

    What is the relationship between the distribution ratio D and the extraction factor E?

    <p>D = E</p> Signup and view all the answers

    What is the primary advantage of using Counter Current Extraction in industrial leaching processes?

    <p>It can deliver the highest possible concentration in the extract.</p> Signup and view all the answers

    What is the assumption made in the mass balance equation for Single Batch Counter Current Extraction?

    <p>There is no volume change on mixing.</p> Signup and view all the answers

    What is the expression for the extraction factor E in terms of V0 and Va?

    <p>E = V0 y1 / Va x1</p> Signup and view all the answers

    What is the equation for the fraction extracted in a Single Batch Counter Current Extraction process?

    <p>V0 y1 / Va x0 = E (E + 1)</p> Signup and view all the answers

    What is the purpose of the decanting step in the extraction process?

    <p>To allow the phases to coalesce and separate.</p> Signup and view all the answers

    What is the distribution ratio in a Single Batch Counter Current Extraction process?

    <p>y1 / x1</p> Signup and view all the answers

    What is the expression for the mass balance in a Single Batch Counter Current Extraction process?

    <p>Va x0 + V0 y0 = Va x1 + V0 y1</p> Signup and view all the answers

    What is the concentration of Cu in the leach liquor in the worked example?

    <p>4g/l</p> Signup and view all the answers

    What is the main purpose of drawing 'steps' between the operating line and the equilibrium curve in a McCabe-Thiele Diagram?

    <p>To calculate the number of theoretical stages required for extraction</p> Signup and view all the answers

    What is the effect of not attaining equilibrium conditions on the extraction process?

    <p>It requires more stages in practice than the ideal analysis</p> Signup and view all the answers

    What is the main factor that affects the equilibrium curve in a McCabe-Thiele Diagram?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of an extraction isotherm in a McCabe-Thiele Diagram?

    <p>To plot the metal extraction in the aqueous and organic phases</p> Signup and view all the answers

    What is the main advantage of using a mixer-settler or a series of mixer-settlers in solvent extraction?

    <p>It is well established with hundreds of operating units</p> Signup and view all the answers

    What is the effect of partial miscibility of the solvents on the separation process?

    <p>It requires more stages in practice</p> Signup and view all the answers

    What is the main purpose of a McCabe-Thiele Diagram?

    <p>To predict the number of theoretical stages necessary to achieve given levels of extraction</p> Signup and view all the answers

    What is the main advantage of using a column as a solvent extraction equipment?

    <p>It can be agitated or pulsed</p> Signup and view all the answers

    Study Notes

    Solvent Extraction

    • The final concentration of Cu in the oil phase and aqueous phase are 6g/l and 1g/l respectively, with volumes of 4 and 8 litres respectively.
    • The distribution ratio (D) is 6g/l / 1g/l = 6.
    • The percent extraction is 100(6 × 4 / (4 × 8)) = 75%.

    Multistage Extraction

    • Fresh solvent and metal in fresh solvent plus metal in aqueous solution equals metal in loaded phase plus metal in raffinate.
    • Va xo + Vo yn + 1 = Va xn + Vo y1.
    • Assuming metal content in fresh solvent and barren solution is near zero, Va y1 = (xo - xn) / Vo.

    Operating Line

    • y1 = (xo - xn) / Vo.

    Fraction Remaining

    • After n stages, xn / xo = (E - 1) / (E^n + 1).

    McCabe-Thiele Diagram

    • A graphical procedure used to analyze systems, where each phase coalesces and separates by decanting.
    • Rarely used in commercial processes due to large solvent volume and low solute concentration.

    Counter Current Extraction

    • Frequently used in industrial leaching to deliver high concentrations in the extract and minimize solvent needed.
    • The solvent phase becomes concentrated as it contacts the solute-rich solid in a stagewise fashion.
    • The raffinate becomes less concentrated in soluble material as it moves toward the fresh solvent stage.

    Single Batch Counter Current Extraction

    • A process where fresh solvent and fresh feed are used, with equilibrium reached in each stage.
    • A mass balance is calculated as Va x0 + V0 y0 = Va x1 + V0 y1.

    Mass Balance

    • Metal in fresh solvent plus metal in aqueous solution equals metal in loaded phase plus metal in raffinate.
    • Va (xo - x1) = V0 (y1 - y0) = V0 y1 (when y0 = 0).
    • Extraction factor (E) = V0 / Va.D, and fraction extracted = E / (E + 1).

    Worked Example

    • A copper leach liquor containing 4g/l of Cu is subjected to solvent extraction using LIX 84 dissolved in kerosene.
    • The number of theoretical stages (n) is found by drawing steps between the operating line and the equilibrium curve.

    McCabe-Thiele Diagram

    • Consists of an extraction isotherm and the operating line drawn on the same diagram.
    • Enables prediction of the number of theoretical stages necessary to achieve given levels of extraction in a counter-current process.

    Extraction Isotherm

    • Obtained by plotting metal extraction in the aq phase (x-axis) and the organic phase (y-axis).
    • The equilibrium isotherm is specific for every particular system and changes with temperature, pH, and concentrations of extractant or metal.

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    Description

    Calculate the distribution ratio and percent extraction of Cu in an oil and aqueous phase system, given the concentrations and volumes of the phases.

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