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Explain how microscopic membrane filters purify contaminated waters, in terms of their design and composition. - HSC - SSCE Chemistry - Question 26 - 2013 - Paper 1
Question 26
Explain how microscopic membrane filters purify contaminated waters, in terms of their design and composition.
Worked Solution & Example Answer:Explain how microscopic membrane filters purify contaminated waters, in terms of their design and composition. - HSC - SSCE Chemistry - Question 26 - 2013 - Paper 1
Step 1
Composition and Design of Membrane Filters
Answer
Microscopic membrane filters are typically composed of thin polymer materials, such as polypropylene or polyethersulfone. These materials are engineered to create membranes with tiny pores, usually measuring around 0.2 µm in diameter. The structure of these membranes allows them to effectively separate contaminants from water.
The polymer is processed and rolled into a thin film, which is then formed into a tube shape. This design maximizes the surface area available for filtration while facilitating the flow of water through the membrane. The arrangement of numerous tubes, often bundled together, increases efficiency and capacity in filtering larger volumes of contaminated water.
Step 2
How Membrane Filters Purify Water
Answer
The purification process occurs as contaminated water passes through these filters under pressure. Small particles, including water molecules, ions, and some microorganisms, can easily pass through the membrane pores. However, larger particles, such as bacteria and protozoa, are trapped on the surface or within the membrane material.
This selective filtration ensures that the output water is significantly cleaner, removing harmful contaminants and pathogens. The effectiveness of this purification method is largely attributed to the size exclusion mechanism that relies on the specific pore size of the membrane.