Science Ace done by Chew Weh and How Rui Yang of 1A2

Science Ace done by Chew Weh and How Rui Yang of 1A2

Saturday, 20 August 2011

How is Reverse Osmosis used and can we use it?

Along with the modern technology, Reverse Osmosis is used to filter many impurities and chemicals and has been very useful. Fortunately, one can also install a small set-up capable of filtering one's water at home. This little yet capable technology is called the Reverse Osmosis Unit or Reverse Osmosis Filter System.

  • The Reverse Osmosis Unit actually has many advantages and are good for you, the citizens!
    • The Reverse Osmosis Unit actually filters tap water into pure water.
    • This has many benefits as usually the tap water contains many harmful substances such as chlorine which can seriously damage your health over a period of time.
    • Consumes no energy, which means it is good for the earth and ultimately also prolongs your lifetime! You can also repeatedly use it without worries.
    • It is in your kitchen! You don't need the hassle trying to boil the water which also removes the oxygen which is good for your health!
    • Free, there is no need to pay for filtering the water, however, paying is necessary for the set-up.





Reverse Osmosis is not only used in households but also in factories where they mass filter seawater, which is extremely large in quantity, into pure water for the general public to drink and consume.

Reverse Osmosis is used for many different purposes in factories:
  • The first and most common usage: Water Purification. As said, thousands of plants are constructed so that there will be water supplied to the people.
  • Supply of water to armies. America was the first country to use this technique. This was because they were the country who funded the research of Reverse Osmosis.
  • Supply of water for reef aquariums. Organisms, both plants and animals can obtain detrimental effects from the impurities in the ordinary tap water.
  • Food Industry. Apparently this can reduce costs other than using heat-treatment processes.
To learn how to use the Reverse Osmosis Unit: http://www.youtube.com/watch?v=wvSuBDtz48Q


Who and How was Reverse Osmosis invented?

Reverse Osmosis was actually discovered after the help of many researchers and scientists but the first person to ever even spark off the idea was the people in the University Of California at Los Angeles. Following that was the University of Florida who also helped them to make the idea become reality. 
  • However, these researchers were only planning to investigate on the idea of desalination through the semi-permeable membranes.
  • Although they did succeed, the flux was far too little to be regarded as a way of filtration. This means that their way of Reverse Osmosis was of a very small scale.
  • Therefore, their idea of Reverse Osmosis was not accepted.
  • However, through the years of advancement of technology, the theory of Reverse Osmosis was slowly developed and now, more than 10 thousand desalination plants are around, worldwide.

However, all these were not possible without the discovery of Jane Antoine Nollet. 
  • He had discovered the theory of Osmosis.
  • As Osmosis included semi-permeable membranes, this actually helped the researchers in the University Of California at Los Angeles to be able to think of Reverse Osmosis.
  • As Osmosis actually was a natural process, it was only to be observed as a phenomenon.
  • Thus, the researchers actually wanted to research on desalination using semi-permeable membranes which later on became Reverse Osmosis.

Actually, the researchers in the University of Florida and the University Of California at Los Angeles did not really discover Reverse Osmosis but merely the theory of Reverse Osmosis.
  • The practical method of Reverse Osmosis was actually invented by researchers in the modern world, equipped with modern technology(or at least better) and also funded by the Office of Saline Water in America.
  • They improved the theory of Reverse Osmosis from the researchers in the two Universities.

Why does Reverse Osmosis work?

Reverse Osmosis is widely known for its usefulness and what is the reason why it works so well? Well, it basically helps to remove impurities from a solution.

Looking at a atomic level or a molecular level, it is very evident that it is a great idea.

  • Firstly, we must understand and acknowledge that the water molecules are far smaller than the other kinds of molecules such as ion, etc.
  • Secondly, we must also understand the meaning of semi-permeable membrane:
    • A membrane is a thin piece of sheet that does not allow molecules to pass, be it small or big.
    • Semi means half so semi-permeable membrane means a thin sheet of material that only allows small molecules to pass. 
    • As there is a presence of holes in the membrane, it thus allows smaller molecules to pass through.
    • However, in Reverse Osmosis, it usually only allows water molecules to pass as other molecules are too big for to pass through these holes.
    • Thus, the key reason to why Reverse Osmosis is excellent!


So how does Reverse Osmosis exactly work? Let's observe it through an experiment.

  1. Seawater is pumped into the set-up and force is applied to the seawater. 
  2. Seawater is constantly supplied.
  3. When the seawater contacts the membrane, salt molecules will be trapped and cannot pass through it.
  4. However, water molecules are able to pass through it.
  5. Therefore, the result of Reverse Osmosis will be pure water.

Why does this experiment work in this way?

  • This is mainly because
    • The salt molecules are bigger than the holes in the semi-permeable membrane. 
    • However, the water molecules are smaller and thus are able to smoothly pass through it as the semi-permeable membrane allows so.
  • Thus, one side will have the seawater while the other will have pure water. 

So, Reverse Osmosis is basically the usage of the semi-permeable membrane as a filter and making the solvent purer by means of forcing it through the semi-permeable membrane.

If you feel lost, refer to this picture, it may be better:
However, you may understand Reverse Osmosis better through this video: http://www.youtube.com/watch?v=rG29fwWoNkc&feature=related

Friday, 19 August 2011

What is Reverse Osmosis?

Just a picture of Reverse Osmosis being used in factories for a starter:


Reverse Osmosis was so great and ingenious that it was actually referred as hyper-filtration mainly because of the cheaper and cleaner costs and the much better efficiency in comparison to distillation and membrane filtration.

So what is Reverse Osmosis? Just a quick recap,
Osmosis is

  • The net movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane. 

Reverse Osmosis is

  • Basically the exact reversed way of osmosis.
  • Reverse Osmosis uses pressure and force to push the molecules into the semi-permeable membrane.
  • So, Reverse Osmosis is generally a filtration method to obtain the filtrate which is often pure(not having any solute) and is normally the solvent itself.


However, it is not used for basic filtration but more often used for a bigger purpose and the scale is much bigger than normal filtration. Reverse Osmosis is different from Osmosis because
  • Reverse Osmosis is more of a unnatural flow of the solution, which means that external force is applied so that the natural flow is reversed.
  • Reverse Osmosis also the filtration  of the solvent whereas Osmosis is generally the idea of diffusion of water molecules.
  • However, in both cases, the molecules pass through a semi-permeable membrane.

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