CE 442 Exam 2 questions with
|\ |\ |\ |\ |\ |\
answers
Difference between coagulation and flocculation - |\ |\ |\ |\ |\ |\
CORRECT ANSWERS ✔✔Coagulation is done by adding a
|\ |\ |\ |\ |\ |\ |\ |\
coagulant (alum) that creates small flocs. Flocculation
|\ |\ |\ |\ |\ |\ |\
slowly stirs the treated material and creates larger flocs
|\ |\ |\ |\ |\ |\ |\ |\ |\
that can then be removed
|\ |\ |\ |\
General concept of colloids and origin of surface charge in
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloids. What causes a colloidal suspension to remain
|\ |\ |\ |\ |\ |\ |\ |\
"stable"? - CORRECT ANSWERS ✔✔• In a colloidal
|\ |\ |\ |\ |\ |\ |\ |\ |\
suspension, solid particles will not settle by the force of |\ |\ |\ |\ |\ |\ |\ |\ |\ |\
gravity
• A colloidal suspension remains "stable" when the solid
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloid stays in suspension and does not settle
|\ |\ |\ |\ |\ |\ |\
Draw, define and describe the ion layers surrounding a
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colloid (Figure 8.3). What are zeta potential, shear plane,
|\ |\ |\ |\ |\ |\ |\ |\ |\
diffuse layer, fixed layer? - CORRECT ANSWERS ✔✔• Zeta
|\ |\ |\ |\ |\ |\ |\ |\ |\
potential: It quantifies the magnitude of the electrostatic
|\ |\ |\ |\ |\ |\ |\ |\
repulsion or attraction between particles in a colloidal
|\ |\ |\ |\ |\ |\ |\ |\
suspension
• Shear plane: It represents the transition between the
|\ |\ |\ |\ |\ |\ |\ |\ |\
tightly bound layer of ions (the Stern layer) and the
|\ |\ |\ |\ |\ |\ |\ |\ |\ |\
, diffuse layer of ions surrounding the colloidal particle.
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Where fluid transitions from high velocity to low velocity.
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• Diffuse layer: region adjacent to charged particles
|\ |\ |\ |\ |\ |\ |\ |\
surface that helps to maintain stability|\ |\ |\ |\ |\
• Fixed layer: Contains positive and negative ions and
|\ |\ |\ |\ |\ |\ |\ |\ |\
sticks to the surface of a charged colloidal particle and
|\ |\ |\ |\ |\ |\ |\ |\ |\ |\
forms part of the double layer around the particle
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General concept of Van der Waals force. Concept of Figure
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8.4 (colloidal interparticle forces vs distance). - CORRECT
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ANSWERS ✔✔This force causes particles to attract to |\ |\ |\ |\ |\ |\ |\ |\
teach other. Need a balance betweed VDW forces and
|\ |\ |\ |\ |\ |\ |\ |\ |\
repulsive forces to remain stable. |\ |\ |\ |\
How do coagulants destabilize a colloidal suspension? -
|\ |\ |\ |\ |\ |\ |\ |\
CORRECT ANSWERS ✔✔• Coagulants destabilize colloidal |\ |\ |\ |\ |\ |\
suspensions by destabilizing the colloids and forming a |\ |\ |\ |\ |\ |\ |\ |\
coagulant floc. The zeta potential is greatly reduced. The |\ |\ |\ |\ |\ |\ |\ |\ |\
particles are also aggregated by reactive groups on the
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloids
What is sweep coagulation? - CORRECT ANSWERS
|\ |\ |\ |\ |\ |\ |\
✔✔Sweep coagulation involves the addition of a polymer, |\ |\ |\ |\ |\ |\ |\ |\
usually a high-molecular-weight synthetic polymer, to the
|\ |\ |\ |\ |\ |\ |\
water after the coagulation and flocculation stages. This
|\ |\ |\ |\ |\ |\ |\ |\
polymer helps to further aggregate the flocs formed
|\ |\ |\ |\ |\ |\ |\ |\
during flocculation, increasing their size and density
|\ |\ |\ |\ |\ |\
|\ |\ |\ |\ |\ |\
answers
Difference between coagulation and flocculation - |\ |\ |\ |\ |\ |\
CORRECT ANSWERS ✔✔Coagulation is done by adding a
|\ |\ |\ |\ |\ |\ |\ |\
coagulant (alum) that creates small flocs. Flocculation
|\ |\ |\ |\ |\ |\ |\
slowly stirs the treated material and creates larger flocs
|\ |\ |\ |\ |\ |\ |\ |\ |\
that can then be removed
|\ |\ |\ |\
General concept of colloids and origin of surface charge in
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloids. What causes a colloidal suspension to remain
|\ |\ |\ |\ |\ |\ |\ |\
"stable"? - CORRECT ANSWERS ✔✔• In a colloidal
|\ |\ |\ |\ |\ |\ |\ |\ |\
suspension, solid particles will not settle by the force of |\ |\ |\ |\ |\ |\ |\ |\ |\ |\
gravity
• A colloidal suspension remains "stable" when the solid
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloid stays in suspension and does not settle
|\ |\ |\ |\ |\ |\ |\
Draw, define and describe the ion layers surrounding a
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloid (Figure 8.3). What are zeta potential, shear plane,
|\ |\ |\ |\ |\ |\ |\ |\ |\
diffuse layer, fixed layer? - CORRECT ANSWERS ✔✔• Zeta
|\ |\ |\ |\ |\ |\ |\ |\ |\
potential: It quantifies the magnitude of the electrostatic
|\ |\ |\ |\ |\ |\ |\ |\
repulsion or attraction between particles in a colloidal
|\ |\ |\ |\ |\ |\ |\ |\
suspension
• Shear plane: It represents the transition between the
|\ |\ |\ |\ |\ |\ |\ |\ |\
tightly bound layer of ions (the Stern layer) and the
|\ |\ |\ |\ |\ |\ |\ |\ |\ |\
, diffuse layer of ions surrounding the colloidal particle.
|\ |\ |\ |\ |\ |\ |\ |\
Where fluid transitions from high velocity to low velocity.
|\ |\ |\ |\ |\ |\ |\ |\ |\
• Diffuse layer: region adjacent to charged particles
|\ |\ |\ |\ |\ |\ |\ |\
surface that helps to maintain stability|\ |\ |\ |\ |\
• Fixed layer: Contains positive and negative ions and
|\ |\ |\ |\ |\ |\ |\ |\ |\
sticks to the surface of a charged colloidal particle and
|\ |\ |\ |\ |\ |\ |\ |\ |\ |\
forms part of the double layer around the particle
|\ |\ |\ |\ |\ |\ |\ |\
General concept of Van der Waals force. Concept of Figure
|\ |\ |\ |\ |\ |\ |\ |\ |\
8.4 (colloidal interparticle forces vs distance). - CORRECT
|\ |\ |\ |\ |\ |\ |\ |\ |\
ANSWERS ✔✔This force causes particles to attract to |\ |\ |\ |\ |\ |\ |\ |\
teach other. Need a balance betweed VDW forces and
|\ |\ |\ |\ |\ |\ |\ |\ |\
repulsive forces to remain stable. |\ |\ |\ |\
How do coagulants destabilize a colloidal suspension? -
|\ |\ |\ |\ |\ |\ |\ |\
CORRECT ANSWERS ✔✔• Coagulants destabilize colloidal |\ |\ |\ |\ |\ |\
suspensions by destabilizing the colloids and forming a |\ |\ |\ |\ |\ |\ |\ |\
coagulant floc. The zeta potential is greatly reduced. The |\ |\ |\ |\ |\ |\ |\ |\ |\
particles are also aggregated by reactive groups on the
|\ |\ |\ |\ |\ |\ |\ |\ |\
colloids
What is sweep coagulation? - CORRECT ANSWERS
|\ |\ |\ |\ |\ |\ |\
✔✔Sweep coagulation involves the addition of a polymer, |\ |\ |\ |\ |\ |\ |\ |\
usually a high-molecular-weight synthetic polymer, to the
|\ |\ |\ |\ |\ |\ |\
water after the coagulation and flocculation stages. This
|\ |\ |\ |\ |\ |\ |\ |\
polymer helps to further aggregate the flocs formed
|\ |\ |\ |\ |\ |\ |\ |\
during flocculation, increasing their size and density
|\ |\ |\ |\ |\ |\
