Filtration
Definition and meaning of Filtration in chemistry.
Filtration is a physical separation process that removes solid particulate matter from a fluid by passing it through a porous medium. The fluid that passes through the filter is called the filtrate, while the retained solid particles form the retentate or filter cake.
In more detail
The mechanism of filtration depends on the pore size of the filter medium, which acts as a physical barrier to particles larger than the pores. It can be driven by gravity, applied pressure, or vacuum to increase the flow rate of the fluid through the medium. In laboratory settings, filter paper placed in a funnel is commonly used for gravity filtration, while a Buchner funnel attached to a vacuum flask accelerates the process. Industrial applications often utilize large-scale filter presses, membrane filters, or sand filters to treat wastewater or purify bulk chemicals. Beyond simple size exclusion, some advanced filtration systems incorporate electrostatic capture or active adsorption, such as activated carbon filters removing dissolved impurities.
Key facts
| Field | General Chemistry |
|---|---|
| Filtrate | Fluid passing through the filter |
| Filter cake | Solid material retained |
| Driving forces | Gravity, vacuum, pressure |
| Common media | Filter paper, polymer membranes |
Brewing coffee involves passing hot water through ground coffee beans contained in a paper filter, which retains the solid grounds while allowing the liquid coffee extract to pass through.
Frequently asked questions
How does vacuum filtration differ from gravity filtration?
Vacuum filtration uses a pressure differential created by a vacuum pump to pull the liquid through the filter much faster than gravity alone, making it ideal for isolating solid products from solvents.
Can filtration separate dissolved substances?
Standard physical filtration cannot separate dissolved substances since they exist as individual ions or molecules smaller than the pores; removing them requires techniques like reverse osmosis or distillation.