1) In concentration polarisation flux decline occurs due to
Reaction between membrane and permeate stream
Accumulation of solute molecules on the membrane surface
High bulk concentration
None of these
2) What happens to the membrane surface concentration as time progresses?
Increases
Decreases
Increases and reaches a constant value
Remains constant throughout
3) Which side of the membrane the osmotic pressure is higher?
Solution side
Solvent side
Equal both sides
4) The effective pressure driving force for solvent flow from solution side to solvent side is(∆P is external pressure difference given)
∆P-∆∏
∆∏
∆P
∆P+∆∏
5) The pore size range for a reverse osmosis membrane is
0.1-1 nm
10 nm
1000 nm
100 µm
6) A UF membrane has a pore-size range of
1-100 A
1-100 µm
1-100 nm
7) A Nanofiltration membrane has a pore-size range of
1nm
10nm
1µm
100µm
8) The concentration of NaCl in sea water is
0.5 molal
0.5 molar
5 molar
9) What is effect of increasing pressure on flux?
Increases
Decreases
Remains constant
10) When bulk concentration increases what happens to flux?
Increases
Decreases
Constant
11) What is effect of decreasing membrane resistance on flux?
Increases
Decreases
Constant
12) Some methods to increase flux through the membrane?
Backwashing of membrane
Stirring in the feed compartment
Increasing bulk concentration
Both a and b
13) The effect of concentration polarisation is least important in which of the following processes?
Gas separation
Haemodialysis
Reverse Osmosis
14) What is the explaination for your choice of answer in Q13 above?
Diffusivity is low in gas phase
Concentration boundary will not form
Diffusivity is very high in gas phase
Both b and c
15) If polarisation modulus in a Reverse Osmosis module is unity, the feed side mass transfer coefficient of the solute is
Very large
Very small
Is equal to the diffusinal resistance of the membrane
16) If reflection coefficient sigma is zero, an osmotic membrane is
Fully permeable
Impermeable
Partially permeable to the solute
17) How does the selectivity of separation change with the increasing membrane thickness?
Increases
Decreases
Remains unchanged
18) In membrane filtration, the solute molecules are carried to the membrane surface by
Knudsen diffusion
Fickian diffusion
Convection
19) How are the rejected solute molecules carried from membrane surface to the bulk?
Convection
Diffusive transport
Knudsen diffusion
20) With increased concentration polarisation on a Reverse Osmosis membrane at a constant applied pressure difference, the solvent flux decreases. What happens to the solute flux?
Increases
Decreases
Remains unchanged