This set of Dairy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Membrane Filter – 2”.
1. Pore size Micro-filtration membrane ranges from _________
a) 0.1- 5µm
b) 0.1- 0.01µm
c) 0.001- 0.01µm
d) 0.0001- 0.001µm
View Answer
Explanation: The pore size on microfiltration membranes ranges from 0.1 – 5 um, and has the largest pore size of the four main membrane types. Its pores are large enough to filter out such things as bacteria, blood cells, flour, talc and many other kinds of fine dust in solution. This can be contributed to its pores which are relatively large compared to other membranes; it can be operated under low pressures and therefore low energy.
2. Pore size Ultra-filtration membrane ranges from ________
a) 0.1- 5µm
b) 0.1- 0.01µm
c) 0.001- 0.01µm
d) 0.0001- 0.001µm
View Answer
Explanation: Ultra filtration has a pore size range of 0.1um to 0.01um. UF membranes reject particles such as silica, viruses, endotoxins, proteins, plastics and smog/fumes such as ZnO. Due to the decrease in pore size, the osmotic pressure required is higher than that of MF.
3. Pore size Nano-filtration membrane ranges from __________
a) 0.1- 5µm
b) 0.1- 0.01µm
c) 0.001- 0.01µm
d) 0.0001- 0.001µm
View Answer
Explanation: Nanofiltration has a pore size range of 0.001-0.01um. NF membranes can filter particles up to and including some salts, synthetic dies and sugars, however it is unable to remove most aqueous salts and metallic ions, as such, NF is generally confined to specialist uses.
4. Pore size RO membrane ranges from _____________
a) 0.1- 5µm
b) 0.1- 0.01µm
c) 0.001- 0.01µm
d) 0.0001- 0.001µm
View Answer
Explanation: Reverse Osmosis has a pore size range of 0.0001 – 0.001. It is by far the finest separation material available to industry. It is used on a large scale for the desalination and purification of water as it filters out everything but water molecules, with pore sizes approaching the radius of some atoms in many cases.
5. The solution to be concentrated or fractionated is called?
a) Feed
b) Flux
c) Membrane fouling
d) Permeate
View Answer
Explanation: Inlet solution which has to be fractionated is called feed. Once feed is injected the membrane filtration process starts.
6. The term for deposition of solids on the membrane, irreversible during processing is?
a) Feed
b) Flux
c) Membrane fouling
d) Permeate
View Answer
Explanation: Membrane fouling is a process whereby a solution or a particle is deposited on a membrane surface or in membrane pores in a process such as in a Membrane bioreactor so that the membrane’s performance is degraded. It is a major obstacle to the widespread use of this technology.
7. The concentrate, the retained liquid is called ___________
a) Permeate
b) Retentate
c) Concentration factor
d) Diafilteration
View Answer
Explanation: Retentate is the matter that is retained by a semi permeable membrane during dialysis; non-dialyzable matter; a substance of this kind.
8. What is the volume reduction achieved by concentration, i.e. the ratio of the initial volume of feed to the final volume of concentrate called?
a) Permeate
b) Retentate
c) Concentration factor
d) Diafilteration
View Answer
Explanation: The concentration factor is the degree that the RO feed water dissolved solids is concentrated in the brine. Concentration Factor = 1/ (1- Y).
9. _________ is a modification of ultra filtration in which water is added to the feed as filtration proceeds in order to wash out feed components which will pass through the membranes, basically lactose and minerals.
a) Permeate
b) Retentate
c) Concentration factor
d) Diafiltration
View Answer
Explanation: Diafiltration is a technique that uses ultra filtration membranes to completely remove, replace, or lower the concentration of salts or solvents from solutions containing proteins, peptides, nucleic acids, and other biomolecules.
10. Which of the following membrane separation technique would be most suitable for dehydration of whey in dairy industry?
a) Reverse osmosis
b) Nano filtration
c) Ultra filtration
d) Membrane filtration
View Answer
Explanation: Reverse osmosis in dairy industry is used for dehydration of whey, UF permeate and condensate.
11. Which of the following membrane separation technique would be most suitable for partial desalination of whey in dairy industry?
a) Reverse osmosis
b) Nano filtration
c) Ultra filtration
d) Membrane filtration
View Answer
Explanation: Nano filtration in dairy industry used when partial desalination of whey, UF permeates or retentate is required.
12. Which of the following membrane separation technique would be most suitable for the concentration of milk proteins in dairy industry?
a) Reverse osmosis
b) Nano filtration
c) Ultra filtration
d) Membrane filtration
View Answer
Explanation: UF in dairy industry is typically used for concentration of milk proteins in milk and whey and for protein standardization of milk intended for cheese, yoghurt and some other products.
13. Which of the following membrane separation technique would be most suitable for the reduction of bacteria in skim milk?
a) Reverse osmosis
b) Nano filtration
c) Ultra filtration
d) Membrane filtration
View Answer
Explanation: MF in dairy industry is basically used for reduction of bacteria in skim milk, whey and brine, but also for defatting whey intended for whey protein concentrate (WPC) and for protein fractionation.
14. What is the Processing temperature in membrane filtration applications?
a) 15℃
b) 25℃
c) 65℃
d) 50℃
View Answer
Explanation: In most cases, the processing temperature is about 50°C for dairy applications. Filtration plants are normally supplemented with a simple cooling system integrated into the internal circulation loop to compensate for the slight rise in temperature that occurs during operation and maintain a constant processing temperature.
15. The separation limit for a membrane is determined by the lowest ___________ that can be separated.
a) Fractional weight
b) Molecular weight
c) Ion weight
d) Mass
View Answer
Explanation: Membranes with a definite separation limit separate everything with a definitely lower molecular weight, while membranes with a diffuse limit let some material with a higher molecular weight through and stop some with a lower molecular weight.
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