Freundlich Isotherm Parameters
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Questions and Answers

What is the unit of q in the Freundlich isotherm equation?

  • mg/g (correct)
  • g/mg
  • mg/L
  • L/mg

    • What is the slope of the log C vs log q line in the Freundlich isotherm?

  • n
  • 1
  • KF
  • 1/n (correct)

    • What is the intercept of the log C vs log q line in the Freundlich isotherm?

  • n
  • log KF (correct)
  • 1/n
  • KF

    • What is the unit of C in the Freundlich isotherm equation?

    <p>mg/L</p> Signup and view all the answers

    Which of the following compounds has the highest value of KF?

    <p>Hexachlorobutadiene</p> Signup and view all the answers

    What is the value of 1/n for Acridine yellow?

    <p>0.12</p> Signup and view all the answers

    What is the equation that represents the Freundlich isotherm?

    <p>q = KF C^(1/n)</p> Signup and view all the answers

    What is the purpose of determining the Freundlich isotherm parameters?

    <p>To determine the adsorption capacity of a material</p> Signup and view all the answers

    What is the total amount of carbon used per volume of liquid treated dependent on?

    <p>Equilibrium constant and the level of pollutant in the carbon</p> Signup and view all the answers

    What is assumed to be in equilibrium with each other in each stage?

    <p>The streams leaving each stage</p> Signup and view all the answers

    What is the typical number of stages used in wastewater applications?

    <p>Two or less</p> Signup and view all the answers

    What is the variable 'qo' representative of?

    <p>Level of pollutant already present in the carbon</p> Signup and view all the answers

    What is the equilibrium constant represented by?

    <p>KF</p> Signup and view all the answers

    What is the direction of the wastewater flow in a multistage countercurrent adsorption process?

    <p>Countercurrent to the activated carbon flow</p> Signup and view all the answers

    What do the numbers attached to the streams leaving any stage represent?

    <p>The number of the stage the streams are leaving</p> Signup and view all the answers

    What is assumed to be constant in a multistage countercurrent adsorption process?

    <p>The rate of wastewater and activated carbon moving from stage to stage</p> Signup and view all the answers

    What is the primary method of removing pollutants from spent activated carbon at the end of a cycle?

    <p>Regeneration through stripping</p> Signup and view all the answers

    What is the characteristic of activated carbon that makes it effective in wastewater treatment?

    <p>High surface area per unit volume</p> Signup and view all the answers

    What is the primary use of activated alumina?

    <p>Moisture adsorption</p> Signup and view all the answers

    What is the process of producing activated carbon?

    <p>Pyrolysis and activation</p> Signup and view all the answers

    What is the common material used as a precursor for producing activated carbon?

    <p>Coal</p> Signup and view all the answers

    What is the term used to describe the process of accumulated pollutants at the interface between activated carbon and wastewater?

    <p>Adsorption</p> Signup and view all the answers

    What is the primary mechanism of pollutant removal during adsorption using activated carbon?

    <p>Physical accumulation</p> Signup and view all the answers

    What is the term used to describe the porous synthetic zeolites used in separation processes?

    <p>Aluminosilicates</p> Signup and view all the answers

    What is the primary location where adsorption occurs?

    <p>At the interface between the solid and fluid phases</p> Signup and view all the answers

    What is the term for the material being adsorbed?

    <p>Adsorbate</p> Signup and view all the answers

    What is the driving force behind adsorption?

    <p>The reduction in interfacial tension between the fluid and solid</p> Signup and view all the answers

    What is the definition of interfacial tension, σ?

    <p>The change in free energy, G, resulting when the area between two phases, A, is increased</p> Signup and view all the answers

    What is the difference between adsorption and absorption?

    <p>Adsorption is the removal of a substance by accumulation at the interface, while absorption is the removal of a substance by dissolution</p> Signup and view all the answers

    What is an example of a solid-fluid interface where adsorption can occur?

    <p>Gas-solid interface</p> Signup and view all the answers

    What is the term for the solid material being used as the adsorbing phase?

    <p>Adsorbent</p> Signup and view all the answers

    What is the result of adsorption on the surface or interfacial tension?

    <p>It decreases the surface or interfacial tension</p> Signup and view all the answers

    What is the equation that represents the operating line for a batch adsorption system?

    <p>C = Co - (q - qo) / BV</p> Signup and view all the answers

    What is the unit of the mass transfer coefficient K in the batch adsorption equation?

    <p>m/s</p> Signup and view all the answers

    What is the cumulative surface area of carbon particles represented by in the batch adsorption equation?

    <p>Ap</p> Signup and view all the answers

    What is the pollutant concentration in equilibrium with the concentration q in the particle at time t represented by?

    <p>C*</p> Signup and view all the answers

    What is the integrated form of the mass balance equation for a batch adsorption operation?

    <p>∫(C dC') = -K Ap (C - C*)dt</p> Signup and view all the answers

    What is the surface area of particles per liquid volume represented by in the batch adsorption equation?

    <p>a</p> Signup and view all the answers

    What is the equation that relates the mass balance at a generic time t with the equilibrium isotherm?

    <p>V (Co - C) = B (q - qo)</p> Signup and view all the answers

    What is the condition required for the equation Ceq = Co - (qeq - qo) / BV to be valid?

    <p>The time elapsed is long enough for equilibrium to be established</p> Signup and view all the answers

    Study Notes

    Determination of Parameters in Freundlich Isotherm

    • Freundlich isotherm equation: q = KF C^1/n, where q is the amount of adsorbate per unit weight of adsorbent, KF is the Freundlich constant, C is the equilibrium concentration, and n is the Freundlich exponent.
    • Log C vs. log q plot produces a straight line with slope = 1/n and intercept = log KF.

    Freundlich Parameters at Neutral pH

    • Various compounds with their corresponding KF and 1/n values:
      • Hexachlorobutadiene: KF = 360, 1/n = 0.63
      • Anethole: KF = 300, 1/n = 0.42
      • Phenyl mercuric acetate: KF = 270, 1/n = 0.44
      • p-Nonylphenol: KF = 250, 1/n = 0.37
      • ...and many more compounds listed.

    Definition of Adsorption

    • Adsorption is the process of removing a substance from one phase to another phase by accumulating at the interface between the two phases.
    • Examples of adsorption: gas-solid interface (VOC on activated carbon), liquid-solid interface (organic pollutant on activated carbon).

    Definitions

    • Adsorbate or solute: the material being adsorbed.
    • Adsorbent: the solid material being used as the adsorbing phase.

    Driving Force for Adsorption

    • The driving force for adsorption is the reduction in interfacial (surface) tension between the fluid and the solid adsorbent.
    • Surface or interfacial tension (σ) is defined as the change in free energy (G) resulting from an increase in area between two phases (A).

    Adsorption vs. Absorption

    • Adsorption is the accumulation of a substance at the interface between two phases.
    • Absorption is the removal of a substance from one phase by dissolution in another phase.

    Common Adsorbents

    • Activated carbon: a char-like material with high surface area.
    • Silica gel: a hard, granular, porous material made from sodium silicate solutions.
    • Activated alumina: aluminum oxide activated at high temperature for moisture adsorption.
    • Aluminosilicates (molecular sieves): porous synthetic zeolites used for separation processes.

    Activated Carbon as an Adsorbent

    • Activated carbon is the most common adsorbent used in wastewater treatment.
    • The adsorbing capacity of activated carbon is associated with very high surface area per unit volume.

    Production of Activated Carbon

    • Activated carbon is produced through a two-step process: pyrolysis and activation.
    • Pyrolysis involves heating a raw material to produce a charred, highly carbonaceous solid residue.
    • Activation involves oxidation of the charred residue to form a network of pores and passages with high surface area.

    Unsteady State Mass Balance for Batch Adsorption

    • The unsteady state mass balance equation for batch adsorption is: C = Co - (q - qo) / B * V.
    • The equation can be integrated to give: t = -1 / K * Ap * ∫(C' - C*) / (Co - C') dC'.

    Multistage Crosscurrent Adsorption

    • The total amount of carbon used per volume of liquid treated is a function of initial, intermediate, and final concentrations, equilibrium constant KF, and level of pollutant already present in the carbon.
    • The equation for the total amount of carbon used is: Btot = B1 + B2 / V * (Co - C1) / (KF * C1^1/n - qo).

    Multistage Countercurrent Adsorption

    • The process involves multiple stages where wastewater and activated carbon flow in a countercurrent manner.
    • The streams leaving each stage are assumed to be in equilibrium with each other.
    • The rates of wastewater and activated carbon moving from stage to stage are constant.
    • In wastewater applications, typically no more than two stages are used.

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    Description

    Determine the parameters of the Freundlich isotherm equation from a graph. Understand the relationship between log C and q.

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