First we have to start with a solvent, which in this case, is water. We then will add our solute, which we will call sugar. The sugar dissolves in the water to form sugar-water. To show the process of osmosis, we will use the example of a U-shaped tube, with a semi-permeable membrane in the middle. On one side of the tube, we will add the sugar-water solution, and on the other side, we add distilled water. The sugar-water side’s liquids will slowly rise, as water is passing through the membrane in order to balance out the solute to solvent ratio throughout the tube. This happens because water is trying to reach equilibrium. At this same time, pure water is moving to the sugar crowded side to make it equal or until the osmotic pressure is reached Osmosis was first discovered through an experiment by Jena-Antoine Nollet in the 1750s where he put alcohol in a pigs bladder and placed that in a container filled with water. He saw that only water moved through the bladder wall. In the early nineteenth century, Henri Dutrochet used Nollet’s discoveries on cell membranes. While looking at plant and animal cells, he saw the movement of water across the cell membrane, which he named osmosis. But it wasn’t until a couple hundred years that we were able to improve this theory.
Reverse osmosis is the application of pressure to reverse the normal flow of water, making it move from the higher concentrated solution to the less concentrated. It is not a natural process. The semi-permeable membranes are made of polyamide-based materials. Reverse osmosis is used for purification of groundwater and also to desalinate water. Because the pores in the semi-permeable membrane are so small, they don’t let salt or bacteria through. This makes reverse osmosis very good for making clean water. It is more efficient than normal osmosis because opposed to it only weakening the toxins, it rids of them completely, by only letting water through the membrane and leaving all the toxins behind. Osmosis is the process of balancing out the toxins between pure water and ground water so toxins are still present. The toxins that are left behind in reverse osmosis go down the drain. Pictured below is a filter used in reverse osmosis and the components of it. You can see how the pores are structured in the filter, along with membranes that filter it out. The filter is not the only the only thing that is required for the process, it is actually quite elaborate with various valves and pumps all together (as shown on the next page). One may ask how someone thought of all this and why they did when we had a “working” water purification in the first place.