Filtration is a process of separation or removal of unwanted substances from a fluid. Such unwanted particles can be oils, suspended solids, or vapours. Various types of filter mediums are used to carry out the filtration process. Filters are essential to subtract the impurities that may exist in solid, liquid or gas.
Depending upon the nature of contaminants and driving force, there are many filtration techniques that are widely used in industries. A few common types of filtration techniques are:
Gravity filtration is the simplest form of filtration, which is also known as General filtration. It utilizes gravitational force to filter out the insoluble solid particles from a solution. This technique involves filter paper and a glass or polyethene funnel fixed on an iron ring. The solution to be filtered is poured into the funnel, which will travel down due to gravity. The liquid will be collected in the beaker below, while solid particles larger than the pores of filter paper will get trapped in the paper.
The solution is forced through the filter paper by applying a vacuum in vacuum filtration. Normally, this filtration technique is rapid and more efficient than gravity filtration. But for this, you need a ‘Buchner’ flask to collect the filtrate. This flask is connected to a vacuum with the help of a tube. The solution is forced into the flask via filter paper while insoluble particles stay on paper upon turning the vacuum on. However, using the right size of filter paper is very important in this technique.
As the name indicates, centrifugal filtration employs centrifugal force to perform filtration. This force is experienced when an object is moving in a circular path, which drives it away from the centre of rotation. The assembly for centrifugal filtration consists of a rotary drum into which fluid is pumped. The rapid rotation of the drum forces the insoluble solid particles to travel away from the centre and get trapped onto the walls while the liquid is forced out. This technique is used in a number of different industries to clarify waste oil or remove small particles of metal from liquids. Moreover, centrifugal filtration provides efficient results with minimal liquid loss.
Hot filtration is beneficial in the systems where crystallization of fluid during filtration is concerned. Crystallization halts the filtration process and often result in product loss. So, such fluids must be filtered rapidly at high temperatures to prevent crystallization. The funnel is allowed to get hot, while the fluid to be filtered brought to boiling. Afterwards, the boiling fluid is then poured through the filter paper in portions. Usually, fluted filter paper and stemless filter funnel are recommended for this technique.
Cold filtration is totally reverse of hot filtration. In this filtration technique, the ice bath is used to rapidly cool down the fluid to expedite the formation of the crystals. This technique results in the formation of very small crystals rather than large crystals, which are formed by cooling the fluid at room temperature. Some substances, such as fatty acid particles, become suspended in the fluid at low temperatures, which makes it easy to filter them out. This process is also useful in the beer industry to create clumps of protein which can then be eliminated.
Granular Media Filtration
Granular Media Filtration is one of the conventional and simplest filtration techniques which has been in use for ages. The fluid is made to pass through the beds of granular media like gravel, sand, or activated carbon. This results in the gradual accumulation of entrapped solids particles within the granular media, which needs intermittent removal through a filter backwash cycle. Moreover, this technique is common in water treatment and wastewater management plants.
A mechanical Filtration is an up-to-date approach that is extensively used in industrial filtration. It involves forcing the fluid through an industrial filter element to get rid of contaminants. While a pump or the line pressure produces such force. Bag filters, cartridge filters, porous sintered metal elements, filter pads, and filter cloth are commonly used filter elements for mechanical filtration.
Filtration is the best way to obtain clean and pure liquid. Some most common filtration techniques are discussed above. All of them are highly utilized by all kinds of industries.