In short, filtration is the removal of impurities from liquids or gases through media. However, the definition of chemical filtration is not that simple.
Not only are the filtration methods of the two substances different, but the filtration methods themselves also have many different conditions. It appears frequently in your and my daily life.
Let’s learn about chemical filtration together.
Filtration in chemistry definition
Filtration is a process that separates solid particles from liquid or gas, which requires the filtered liquid or gas to pass through a filter medium with a specific pore size, thereby separating suspended solid matter.
The pore size of the filter medium is designed to only allow solvent particles to pass through, while blocking solute particles so that the solution does not contain insoluble solutes, thereby achieving the purpose of filtration.
Common filtration processes for liquids
First of all, before performing liquid filtration, you must first understand that liquids are divided into two categories: homogeneous and heterogeneous.
The solute particles in a homogeneous mixture are evenly distributed, so it is also called a solution.
A common example is salt water; the solute particles in a heterogeneous mixture are unevenly distributed, and eventually sediment will appear at the bottom of the bottle.
The filtration of liquids uses particle size. differences to separate these mixtures.
In filtration, the filter media is passed through, allowing particles of a specific size to pass through. For example, to separate sand and water, you can use a muslin cloth at the mouth of the container and let the solution pass through the muslin cloth.
The water will pass through, while the sand will be blocked on the muslin cloth. In this way, water and sand are separated.
Filtration theory about gases
Although it was mentioned in the previous paragraph that both gases and liquids can be filtered and separated from solid particles, the principle of gas filtration is not the same as that of liquids. It is not just separation through filter media:
Further reading : How to choose the right chemical filter?
What are the commonly used filtering methods?
There are many types of filtration methods. Using the correct filtration method at the right time depends first on whether the impurities are suspended in liquid or gas, or dissolved in liquid or gas. Therefore, there are the following common filtration methods:
general filtering
This is the most common form of filtration, which uses gravity to pour the mixture into the filter media, causing the liquid to flow downward and the solids to remain on the filter. This is how coffee machines filter.
vacuum filtration
Vacuum filtration is suitable for small batches of solutions. The purpose is to quickly dry the filtered impurities. This method requires a Buchner flask and a hose to generate a vacuum, and uses the pressure difference to suck the solution into the filter, usually with the help of gravity; the other Vacuum filtration uses a pump to create a pressure difference on both sides of the filter.
This filter has no restrictions on vertical placement because gravity is not the main factor affecting the filtration effect.
cold filtration
The purpose of cold filtration is to quickly cool the solution and promote the formation of small crystals so that they can be collected on the filter.
This filtration method can usually be seen in the laboratory. The solution will first be placed in an ice bath to quickly Cooling, to speed up crystallization, will be too slow through room temperature and is also a common method used when solids are initially dissolved.
hot filter
In contrast to cold filtration, the purpose of using hot filtration is to minimize the formation of crystals to facilitate the separation of solid particles from high-temperature solutions.
A funnel is used in this process to prevent crystals from growing and clogging the funnel during the filtration process. The stemless funnel has a smaller surface area, which effectively prevents crystals from forming in the funnel and also prevents crystals from clogging the funnel.
Common filtering method applications
Although these filtering methods sound complicated and troublesome, you can actually see these filtering methods all around you and are applied to many things that are very close to daily life:
brewing coffee
In the process of brewing coffee, hot water flows through the coffee powder and separates the coffee grounds from the coffee. This is a very common general filtration method. The principle of making tea is also very similar, except that it is filtered through tea bags or tea bags. Balls are used to separate tea leaves and tea water, and these two items used to separate tea leaves are a type of filter media.
mask
Masks reduce the release of pathogens from infected people and the inhalation of external particles by filtering particles. The pore size and thickness are important factors that affect the filtering efficacy.
kidney
As the most important decomposition factory in the organism, the kidneys filter particles in the blood through the glomerulus. In the process, water and necessary nutrients are reabsorbed. Unwanted particles are decomposed or encapsulated and excreted from the body.
air purifier
The air purifier uses a HEPA filter to remove suspended particles in the air. It can even block PM 2.5 to avoid harm to the human body. The furnace also uses a filter, but the purpose is to prevent the particles produced after combustion from contacting the parts and causing damage.
water
Water itself is actually a filtering liquid. For example, an aquifer is a natural water filter. It is usually located when water flows through sand and permeable rocks. It can filter out large particles and pathogens, and also remove pollutants through ion exchange.
oil filter
The oil filter is one of the key parts of the automobile engine. Its main function is to filter impurities in the engine oil and protect the engine from pollution. During the operation of the engine, various impurities may be produced, such as small metal chips, sludge, water, etc. These pollutants will affect the lubrication, cleaning and heat dissipation functions of the engine oil, accelerate engine wear, reduce performance and increase fuel consumption.
belt filter
Also known as a belt press filter, it is a filter equipment that uses two endless filter belts to wrap around a series of rollers arranged in sequence to remove moisture from the slurry through the squeezing and shearing effects between the filter belts. It has It has the advantages of simple structure, high dehydration efficiency, large processing capacity, low energy consumption, low noise, high degree of automation, continuous operation, and easy maintenance.
Belt filters are mainly used in papermaking, printing and dyeing, pharmaceuticals, mining, steel, coal, tanning and other industries, especially in urban sewage treatment and industrial sludge dehydration.
aquarium
Aquariums use fiber filters to allow the water to continuously provide enough oxygen for fish and shrimp to survive. Although the fiber filter itself has a loose structure, it is very easy to clean. It is also proud of its structure. The different densities inside allow water to flow in the direction of the denser fiber bundles and obtain good filtration.
Myth busted: The difference between filters and sieves
People often regard the sieve as a type of filter and compare it with many devices. In fact, the sieve is a device for separating materials. Although it is also called a filter, the principle is similar to filtration, but it only has a simple A common related application is the flour sifter in the kitchen, but some people call it a surface filter because it does not actually produce any chemical effects.
What are some alternatives to filtering?
All gases or liquids do not have to pass through the media before they can be filtered. In fact, there are two methods that can achieve the same purpose of filtration, but the effect is not necessarily 100% the same.
Decantation
This is a method of separating liquids and solids, provided that the solid must be denser than the liquid and insoluble in the liquid. Pour the mixture into a container and tilt it slightly so that the liquid flows out and the solids remain in the container. This method will leave a small amount of residual liquid in the container and is very easy to operate. Normally, rice is washed using decantation.
The principle of decantation is to use gravity to guide denser solids to slowly settle to the bottom of the mixture to achieve solid-liquid separation. It can also be used to separate two mutually immiscible liquids, but the effect is not as good as using a separatory funnel.
centrifuge
This is a method of separating liquids and solids, provided that the solid must be denser than the liquid and insoluble in the liquid. Pour the mixture into a container and tilt it slightly so that the liquid flows out and the solids remain in the container. This method will leave a small amount of residual liquid in the container and is very easy to operate. Normally, rice is washed using decantation.
Centrifugation is a way to use centrifugal force to separate different particles from a solution. The particles have different separation conditions based on factors such as size, shape, density, medium viscosity, and rotational speed. Higher-density ingredients will be closer to the outside of the centrifuge, while lower-density ingredients will be closer to the inside.
What is the filtration in chemistry definition?｜FAQ
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