Membrane Transport Phenomena Quiz

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson
Download our mobile app to listen on the go
Get App

Questions and Answers

What is the role of the gel-layer resistance next to the membrane in ultrafiltration units?

  • Decreases the concentration gradient
  • Facilitates solvent flux
  • Enhances solute back diffusion
  • Increases resistance to solvent flux (correct)

In the gel-polarized regime, what determines the solvent flux in ultrafiltration units?

  • Pressure difference
  • Concentration gradient
  • Back diffusion equation (correct)
  • Gel-layer resistance

What type of solutions have experimental data confirmed the use of Eq.(24.5-6) for in ultrafiltration units?

  • Dilute solutions only
  • Macromolecular and colloidal solutions (correct)
  • Homogeneous solutions
  • Inorganic solutions

What does a reverse osmosis membrane allow to pass through while impeding the passage of other substances?

<p>Solvent only (B)</p> Signup and view all the answers

Which factor plays a critical role in determining the volume of pure solvent water associated with a certain amount of solute in reverse osmosis?

<p>Temperature (D)</p> Signup and view all the answers

What size of suspended materials can be removed using reverse osmosis according to the text?

<p>Smaller than 1 micron (D)</p> Signup and view all the answers

Which membrane configuration has the highest ratio of membrane area per unit volume?

<p>Hollow-fiber (D)</p> Signup and view all the answers

What is the typical pressure drop range for ultrafiltration units?

<p>5-100 psi (A)</p> Signup and view all the answers

In the flux equation for ultrafiltration, what can be neglected?

<p>Osmotic pressure (D)</p> Signup and view all the answers

What phenomenon occurs when the solute concentration builds up at the membrane surface?

<p>Concentration polarization (C)</p> Signup and view all the answers

What happens to the solvent flux as the pressure drop increases?

<p>It increases (B)</p> Signup and view all the answers

What is the primary effect of a higher convective transport of the solute to the membrane?

<p>The concentration of the solute increases at the membrane surface (A)</p> Signup and view all the answers

What is the relationship between the convective flux and the diffusion flux at steady state?

<p>The convective flux is equal to the diffusion flux (D)</p> Signup and view all the answers

What is the effect of further increases in pressure drop on the ultrafiltration process?

<p>It decreases the solvent flux through the membrane (C)</p> Signup and view all the answers

Which equation describes the relationship between the mass-transfer coefficient and the solute concentration at the membrane surface?

<p>$N_w/ = k_c <br /> (c_s/c_p)$ (A)</p> Signup and view all the answers

What is the effect of concentration polarization on the ultrafiltration process?

<p>It decreases the solvent flux through the membrane (D)</p> Signup and view all the answers

Flashcards are hidden until you start studying

Study Notes

Convective Transfer and Gel-Layer Resistance

  • In the gel-polarized regime, the net flux of solute by convective transfer equals the back diffusion of solute into the bulk solution due to the polarized concentration gradient.
  • The added gel-layer resistance next to the membrane causes an increased resistance to solvent flux, which is determined by 𝑁𝑤 = ∆𝑃 1 𝐴𝑤 + 𝑅𝑔.
  • The solvent flux in this regime is independent of pressure difference and is determined by the back diffusion equation.

Reverse Osmosis Membrane Process

  • In reverse osmosis, a spontaneous transport of solvent occurs from a dilute solute or salt solution to a concentrated solute or salt solution across a semipermeable membrane.
  • The osmotic pressure is given by the equation π = nRT / Vm, where n is the number of kg mol of solute, Vm is the volume of pure solvent water, R is the gas law constant, and T is temperature in K.

Ultrafiltration

  • In ultrafiltration, the membrane does not allow passage of the solute, which is generally a macromolecule.
  • The flux equation for ultrafiltration is 𝑁𝑤 = 𝐴𝑤(∆𝑃), since the osmotic pressure is very low and can be neglected.
  • Ultrafiltration units operate at a lower pressure drop (5-100 psi) compared to reverse osmosis (400-2000 psi).

Concentration Polarization

  • In ultrafiltration, the solute is rejected by the membrane and accumulates at the surface of the membrane, leading to concentration polarization.
  • As pressure drop increases and/or concentration of the solute increases, concentration polarization occurs, which is more severe than in reverse osmosis.
  • The convective flux equals the diffusion flux at steady state: 𝑁𝑤𝐶 ρ = − 𝐷𝐴𝐵 𝑑𝑐 / 𝑑𝑥.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

More Like This

Biology Chapter 11: Membrane Transport
5 questions
Biology Chapter 5: Membrane Transport
26 questions
Membrane Transport Concepts
6 questions
Cell Biology Quiz: Membrane Transport Processes
45 questions
Use Quizgecko on...
Browser
Browser