Filtration is the process through which a filter allows suspended solid particles to be removed from a liquid. The term filtration can involve a filter being either mechanical, biological or physical.
The filtrate is the term used for the liquid that passes through the filter, it is by far the most common separation technique we might use in our day-to-day lives.
Whether it is from a morning tea or coffee to a soothing shower before bedtime, we encounter a plethora of processes of filtration in our lives on a daily basis.
It could be paper, fabric, cotton-wool, asbestos, slag- or glass-wool, unglazed earthenware, sand, or any other porous material that is used to act as a filter.
In formal terms, the diameter of the pores in the porous membrane really should be only lower than the impurities one would like to remove.
In general terms, the size of the filter can be selected based on the size of the impurities or the size of the required filtrate, but it is not necessarily correct to define filtration as sieving, where separation takes place through a single perforated membrane/screen/sieve.
More specifically, a sieve provides a threshold calibration in which all undersize materials, being of the same kind or phase as the undersized sieving material, are free to pass through, whereas a filter will segregate based on materials properties such as size, phase, reactivity and polarity.
Because of these properties, filtration is incredibly useful and allows us to easily apply these techniques through our everyday lives. Let us explore some examples:
Examlpes of Filtration
1. Coffee Filter
Coffee is one of the most appreciated beverages in the world. It is a beverage made by brewing ground or roasted coffee beans which are highly regarded for their taste and aroma, and also for caffeine, a key factor for coffee’s popularity.
When we think about coffee, people mainly think about its ability to give a energy boost. But studies have also known coffee to have multiple effects that relate to human health. With this in mind, it is recommended to consume filtered coffee.
Coffee filters are coffee-brewing products, made of disposable paper most times, that help to hold the coffee grounds while allowing liquid coffee to flow through the equipment.
Filtered coffee has been related to a lower probability of dying from cardiovascular diseases, ischemic heart disease, or stroke when compared to unfiltered coffee. Unfiltered coffee contains compounds that have positive influences on blood cholesterol.
By using a filter, we receive filtered coffee, which could lessen the risk for heart concerns and premature death.
In addition, filtered coffee through a paper filter was seen to be healthier for you than not drinking coffee at all.
Compared to not drinking coffee, filtered coffee is related to lower risk of death that includes a 12% lower risk of death from cardiovascular diseases in men, and a 20% lower risk of death from heart diseases for women.
2. Tea-bags
Humanity has known the relaxing, refreshing and mood-changing effects of tea for countless ages.
Tea has calming properties from the leaves of Thea sinensis that are used for meditation and to calm the nerves, and it contributes to a better state of mind.
Tea has become a staple in our lives and, in order for tea to keep pace within the confines of modernity, we have streamlined the preparation of tea to make consuming it in our busy lives a possibility.
When the tea leaf and the tea liquid was first separated, it was done by means of a tea-infuser; this has now been replaced with the now popular and much more convenient tea-bag.
A tea bag is a small porous sealed bag or packet commonly containing dried tea leaves that act as a filter as it is submerged into a liquid to extract the tea leaf for the infusion.
Tea-bags originated as strictly for tea (thea sinensis) and it is now possible to find tea-bagged varieties of a large number herbal and other tea-leaf varieties as well.
3. Water Filters
Currently, due to an increase in population, an increase in industrial development, and an increase in environmental pollution, pure and clean drinking water is not readily available.
While water is known to function as its own purifying product, there are still some pollutants or impurities that cannot be remedied through natural means. Fortunately, there is technology available that provide several varieties of water filters along with our water supply systems.
A water filter is an appliance that removes impurities below the level of contamination using a fine physical barrier, a chemical process, or a biological process.
Water filters can reduce impurities in water by different levels based on many purposes such as agricultural irrigation systems, accessible drinking water, public and private aquariums, and safe usage of ponds or swimming pools.
At the home level, water filters are available in several varieties, including granular-activated carbon filters (GAC), depth filters, metallic alloy filters, microporous ceramic filters, and carbon block resin (CBR) filter, with microfiltration and ultrafiltration membranes. Some filters include more than one filtration method as a multi-barrier system.
4. Sand Filtration
Sand filtration is a means by which the treatment of the water is performed by ‘porous’ nature of a sand layer, where particles are captured in the water to treat it.
This technology is used in wastewater management facilities all over the world. There are generally three types of sand filters, rapid (gravity) sand filters, upward flow sand filters, and slow sand filters.
The first two types use flocculant chemicals to work properly, while slow sand filters produce very high-quality water – 90 % to >99 % pathogen removal (depending on strains) – without chemical aids.
The key remaining difference between slow and fast sand filters is that the top layer of sand is biologically involved with microbial species in slow sand filters. It is recommended and widely done, that the filter depth is 0.9 to 1.5 meters.
In 10–20 days in process, a microbial layer forms that removes pathogens from the water.
After a period of time, the filter will be saturated with particles, and must be cleaned to prevent that complete blockage.
5. HEPA Air Filters
HEPA stands for high-efficiency particulate air. A HEPA filter is a type of mechanical air filter that works by forcing air through a fine mesh that collects hazardous particles such as pollen, pet dander, dust mites, and tobacco smoke.
Actually, high energetic ultraviolet light systems or anti-microbial layer panels often incorporate HEPA filtering systems to kill existing live bacteria and viruses that can become trapped on filter media.
The most efficient HEPA systems have a performance rating of 99.995 %, ensuring high levels of safety against the spread of airborne diseases.
using a HEPA filter in the home can help to eliminate most airborne particles that may worsen your allergies. However, the particles that are airborne aren’t the only concern, there are far more contained in rugs, bedding, drapes and resting on countertops and tables.
This technology is also implemented in building vacuum cleaners. In order to work properly, HEPA filters in vacuum cleaners are designed to circulate only air from outside the machine, rather than the contaminants.
6. Automotive Filters
Filters are critical to a vehicle’s life span in that they safeguard vehicles from early wear. Usually a fibrous material, an automotive filter stops the contaminant from entering vehicles and causing damage.
Most vehicles come with mainly four types of filters: (1) Air Filter, (2) Fuel Filter, (3) Cabin Filter, and (4) Oil Filter. It is a complicated landscape to navigate, but the important consideration is to know what each filter does to vehicle shapes.
- Air Filter: Air filters make sure the vehicle has clean air for each combustion event; much like humans need oxygen to breathe, a car must have oxygen for combustion. An air filter makes sure insects, dirt, sand, and rubbish never get to the engine while providing a good air to fuel mixture and helping with vehicle performance. Car air filters come in many shapes in terms of the vehicle design like panels, circular. or cylindrical.
- Cabin Filter: The cabin air filter is a filter that filters the air entering the cabin of your vehicle. When the cabin air is turned on, the air travels from outside the vehicle into the vehicle, past the filter into the cabin. If you do not replace your vehicles cabin air filter, you may have lower HVAC efficiency, and can contribute to inside the vehicle airborne pollution.
- Fuel Filter: As fuel leaves a refinery, fuel is clean. However, it must travel on trucks to a gas station where it can be contaminated. A fuel filter does its job by keeping dirt, rubbish, and water out of the engines combustible fuel. The fuel filter is a cartage located in the fuel line, it has a screen to collect dirt, rust, and rubbish from inside the fuel before it enters the fuel injector.
- Oil Filters: Another common automotive filter type, the oil filter removes contaminates from inside the engine oil. As engine oil travels from the drip pan into the engine, the engine oil will travel through a filter that removes debris, contaminates, or foreign objects. Unlike the ordinary person, any mechanic or auto shop will replace the oil filter every time they change your vehicles engine oil.
Over time filter can block flow of air or liquid. The boxes that may be dust on the filter fill over time, and can cause blockages that decrease the performance of your vehicle.
7. Belt Filters
The belt filter, also known as a belt press filter or belt filter press, is an industrial machine intended for solid/liquid separation processes. It is often used for the dewatering of sludges in the chemical industry, but can also be found in mining and water treatment.
The filtration process occurs when the filtering cloths and belts are passed through a roller system which separates a sludge or slurry taken as a feed into a filtrate and a solid cake.
The filter cloths are made from synthetic materials, such as polypropylene or polyester, with either mono or multifilament yarns, and a variety of complex weaves and layers. Belt filters can also be used for manufacturing apple cider vinegar, as well as the winemaking industry.
8. Dialysis
Healthy kidneys filter your blood, remove waste fluids as urine, and provide chemicals (or substances) needed to keep your body healthy.
Dialysis is a way of approximating some of the kidney’s functions when your kidneys can no longer work due to unfortunate medical circumstances.
Dialysis involves the diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane. A semi-permeable membrane is a thin layer of material with holes or pores of various sizes.
Smaller solutes and water pass through and upsize objects such as red blood cells and large proteins do not. Your blood is carried from your body to the dialyzer in blood tubing as part of a catheter system.
In the dialyzer, filters more like kidneys remove the waste materials from your blood, and your blood is returned to you through another catheter. The entire process closely resembles having an artificial kidney.
9. RO Filters
If you live in an urban environment, you might know about the RO devices involved in water filtration.
The reverse osmosis filtration system works by applying pressure, through a semi-permeable membrane, to water to separate chemically the components that you can’t see.
Water passes through a series of filters in RO systems, which include: sediment filter, carbon filter, RO membrane filter, UV lamp, UF membrane filter, and post-carbon filter. Each one has the ability to attract and filter out a certain type of impurity.
A Reverse Osmosis membrane has tiny pores that in some applications can allow water molecules to pass through but can also keep contaminants like sodium and chlorine out.
Osmosis involves crossing semi-permeable membranes from a less concentrated side (no impurities) to the water with a higher concentration of impurities.
Reverse osmosis reverses the flow using external pressure; when pressure is applied to a certain volume of saltwater during reverse osmosis, the salt is left behind and only clean water pushes through.
Reverse osmosis membranes are typically synthetic plastics that can block sodium and chlorine while blocking even larger impurities like bacteria, urethra, and viruses.
These reverse osmosis drinking water systems are very effective at removing lead, arsenic, copper, chrome, selenium, fluoride, etc.
10. Aquarium Filters
Maintaining an aquatic pet can be a very dirty job. To manage the cleanliness of their environment, aquarium filters are used in the tank or aquaria. The aquarium filter is an important system of both freshwater and marine aquaria.
In general, aquatic animals in the aquarium excrete waste through excretion, respiration, and through uneaten food or plants.
The waste materials that are produced in the tanks accumulate in the tanks and ultimately pollute the water. As the pollution increases, the health risk of the aquaria also increases, hence why removing the pollution is important.
The filtration of aquarium water has three processes that include mechanical filtration, biological filtration, and chemical filtration.
- Mechanical Filtration: Mechanical filtration, physical filtration, or particulate filtration, is achieved by pushing water through some sort of filter media that serves as a strainer. In this case, the water column has impurities physically removed by some filter media. This can be done using a sponge or foam, very fine mesh or net (often referred to as a “sock” in certain designs), the gravel in your tank (for under gravel filtration), or some other similar means. The water moves through it, and any larger impurities are trapped. You can remove these by replacing or cleaning the filter media or they can breakdown and be removed via some other means.
- Biological Filtration: Biological filtration is the process by which beneficial bacteria breakdown ammonia and nitrite and change it to nitrate which is far less harmful. Beneficial bacteria need oxygen-rich water, and the beneficial bacteria need a surface to which bacteria can attach to, like rocks or sand. All aquariums should have some means of biological filtration, and with very few fish, that in itself may be enough to provision the aquarium.
- Chemical Filtration: Chemical filtration is provided by carbon or chemical resins that remove toxins from the water. Activated filter carbon will remove chemicals from your water until it is saturated. Any activated filter carbon in your filtration system must be changed regularly.
11. Büchner funnel
If you have had an opportunity to be in a chemistry lab, you may have noticed a cylindrical piece of lab equipment known as the Büchner funnel.
It is the most popular piece of equipment to use for vacuum filtration in the lab. Traditionally the Büchner funnel is made from porcelain, but glass and plastic versions can also be found around the lab.
The top of the funnel is a cylinder with a fritted glass disk/perforated plate that separates it from the funnel. The filtration process in a Büchner funnel is somewhat similar to that of the Hirsch funnel or a simple funnel with filter paper.
However, the main advantage the Büchner funnel has over the others is that the filtration proceeds much more rapidly (several orders of magnitude) compared to simply relying on the force of gravity to let the liquid drain through the filter medium.
Along with that, the vacuum suction to allow the wet recrystallized compound to dry out pressing it against the filter medium, one must use caution when working with the vacuum as it may also extract the undesired liquid.
It is primarily used in organic chemistry labs to assist in the collection of recrystallized compounds. There is also a more advanced type of funnel, called the Nutsche Filter, that is used mainly outside of academic labs in industry, which can filtrate under vacuum or pressure.
