Many people have no idea what is diffusion. diffusion refers to the movement of something from one area of high concentration to another area of low concentration over a period of time. diffusion is a simple principle used in many industries, but it has only recently come into the focus of interest as an environmental management practice. The principle is used to control how waste is distributed in the production and processing of materials. It also can be used in water management to control the amount that flows from places with high concentration of dissolved pollutants to those with low concentration.
Diffusion can be simplified into a few different forms. The most well known is simple diffusion. Simple diffusion is the movement of molecules from an area of high concentration to an area of low concentration over a period of time. Simple diffusion is actually the movement of most organic molecules in one direction at one point, while avoiding the reverse. There are times when diffusion is facilitated by solutes or other matters that do not move.
Another form of what is diffusion is through what is called osmosis. Osmosis is really a matter of increasing a concentration gradient by forcing solvent molecules through a membrane. This form of diffusion is also facilitated by solute contaminants that do not move under pressure.
A third form of what is diffusion is through what is called mechanical transpiration. Transpiration is the transpiration of water from an area with a high concentration gradient to an area with a lower concentration gradient. This is often necessary when the process involved is that of de-mineralization or the removal of soluble contaminants from water. Mechanical transpiration is commonly done in desalination plants for the production of saltwater. It also is used in a method called electrolysis where water is passed through an electric membrane that is electrically charged.
The fourth type of what is diffusion is via the use of what is called a cell membrane. A cell membrane is made of a layer of an inert material that does not allow the passage of certain chemicals or other substances. Cell membranes are often used as a packing material in which various chemical substances such as salt or detergents are packaged. It is also used as part of the packaging of pharmaceutical drugs. Cells in the cell membrane may also be used as pores through which solutes can diffuse into the solution in order to complete chemical reactions.
One way that a cell membrane can be used to study diffusion is via what is called a field-effect study. In this study, what is diffusion is studied by monitoring the concentration of particular molecules in a solution. A field effect shows where molecules go from an area of high concentration to an area of low concentration with time. For instance, when a molecule such as a sulfate is present in what is usually water, it will diffuse into the lower concentration area. But, if this same molecule is introduced into what is water with a field effect, then where it goes to is where it will stop.
The fifth type of what is diffusion is facilitated diffusion. This is also known as entrained diffusion in which what is diffusion is studied by using something that is semipermeable and what is transport. The semipermeable membrane is a layer of semi-permeable material that allows some molecules to pass through while blocking others. Entrained diffusion uses diffusion processes that are parallel to those used by what is diffusion. For instance, the molecules that make up a solute may be entrained on a semipermeable membrane so that the molecules actually can travel in a chosen direction.
In addition to what is diffusion, another type of what is diffusion is entrained diffusion. With this type of diffusion, a semipermeable membrane is used that causes the diffusion of a compound or solute onto a substrate. What is entrained diffusion does not use a field for transportation. In entrained diffusion, the molecules that are part of the compound are transported on a surface that has a similar concentration gradient to that of the compound.