Filtration

Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness). Filtration is also used to describe some biological processes, especially in water treatment and sewage treatment in which undesirable constituents are removed by absorption into a biological film grown on or in the filter medium as in slow sand filtration.
Decantation is a process for the separation of mixtures, by removing a top layer of liquid from which a precipitate has settled. Usually a small amount of solution must be left in the container, and care must be taken to prevent a small amount of precipitate from flowing with the solution out of the container. It is frequently used to purify a liquid by separating it from a suspension of insoluble particles (e.g. in redwine, where the wine is decanted from the potassium bitartrate crystals). For example, to obtain a sample of clear water from muddy water, muddy water is left in a container until the mud settles, and then the clear water is poured into another container.
Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which, instead, occurs within the entire mass of the liquid and can also take place when the vapor phase is saturated, such as when steam is produced in a boiler. Evaporation that occurs directly from the solid phase, as commonly observed with ice or moth crystals (napthalene or paradichlorobenzine), is called sublimation.
Distillation is the technique of heating a liquid to create vapor which is collected when cooled separate from