While watching movies, you might have seen men pouring wine from a fancy piece of glassware called a decanter. Apart from providing a luxurious eye-catching look, a decanter also holds a scientific purpose to it. Decantation is one of the many processes for the separation of mixtures of immiscible liquids or a liquid and a solid mixture such as a suspension. In simple terms, decantation is a process of carefully pouring a solution from a container, leaving the precipitate (sediments) at the bottom of the container, or in the case of two liquids, the less dense of the two is poured off, leaving the more dense liquid behind. 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. In laboratory conditions, small volumes of mixtures are often decanted in test tubes. If time is not an issue, the test tube is kept in a test tube rack at a 45-degree angle for proper decantation to take place.
This causes the heavier particles to slip down the side of the test tube while allowing a path to the lighter liquid to rise. The heavier mixture part could block the test tube if the test tube was held vertically and not allow the lighter liquid to move as it rises. Let’s discuss a few decantation examples in everyday life:
1. Wine Bottles
When it comes to a new bottle of wine, there is one important step between corkage and enjoying a glass, decantation. This is necessary because over a period, after processing, the wine throws sediments due to the fermentation process. These sediments can make the taste of the wine undesirable. To address this issue, a decanter is used to perform the process of decantation. A decanter is a glass vessel with an easy-pour neck that comes in various sizes, designs, and shapes. The most common variation of the wine decanter has a wide base and a narrow neck. This structure lets the sediment stay in the base of the decanter when the wine is poured. The precipitate of the wine is usually the crystals of potassium bitartrate. Besides preserving the taste of wine, decantation also helps in enhancing its flavor by a process called aeration. Aeration is the process of introducing oxygen to a liquid. This process is also called “allowing a wine to breathe.” Storing a liquor in a decanter encourages oxidation, which allows the liquor to develop flavors faster.
2. Separation of Glycerin from Biodiesel
Glycerol is generated as a by-product of biodiesel synthesis. The traditional method of removing glycerol is mainly by decantation or centrifugation. This method incorporates crude glycerol, which may contain impurities such as methanol, oil, soap, salt, and other organic materials at ppm levels. In order for biodiesel to be used in its pure state, it is necessary to decant it from the glycerin derived from it. Biodiesel is a biodegradable and renewable fuel produced by transesterification of renewable sources such as soybean, microalgae, palm cooking oil, and jatropha. Crude glycerol is the main byproduct produced during the transesterification process in the biodiesel plant, with the generation of 10% (by weight) glycerol of the biodiesel. The analysis shows that about 1 kg of crude glycerol is generated with every 10 kg of biodiesel production. Since biodiesel is less dense than glycerol, it can be separated from biodiesel by decantation. However, this method compromises the purity of the glycerol obtained, and therefore, other methods such as acidification and ion exchange are preferred.
3. Decontamination of Mercury
Crude oil and natural gas are predominantly composed of hydrocarbon atoms, water, and a wide spectrum of elements at low levels, such as arsenic, vanadium, and mercury. In each stage of the extraction and transformation process, the presence of mercury in crude oil and natural gas varies depending on pressure and temperature that distributes mercury unequally between the vapour, condensate, and aqueous phase. Mercury causes a wide range of problems for refiners, for example, equipment degradation, toxic waste generation, health impacts, and the poisoning of catalysts. It is removed by the process of decantation as mercury is denser than other liquids present in the extracted solution.
4. Milk Cream
Many of us enjoy cuisines that have cream as a major ingredient, and some of us even use it for skincare. The saturated fat content of cream has several uses for humankind. To prepare cream from milk, it goes under several processes including decantation. In most of the separation techniques based on decantation, gravity plays an important role. The centrifugation method is used in dairies to simulate gravity via acceleration. The milk to be skimmed is placed into a large centrifuge machine in a closed jar. The milk starts spinning at a very high speed in this container when the centrifuge machine is turned on. Because of this, the milk is split into a cream and skimmed milk. The lighter cream floats over the skimmed milk and can be extracted by decantation. The extracted cream further goes under centrifugation to be separated in butter and butter-milk, which can be separated by physical filtration.
5. Sugar Beet Processing
Sugar beet is a plant whose root contains a high concentration of sucrose, and it is grown commercially for sugar production. The root of the beet contains 75% water, about 20% sugar, and 5% pulp. In the processing of sugar beets into granular sugar, many liquid-solid separations are encountered. After they are harvested, beets are transported to a factory where they are washed, mechanically sliced into thin strips called cossettes, and passed to a machine called a diffuser to extract the sugar content into a water solution, a process known as leaching. The liquid exiting the diffuser is called raw juice. After going through several processes such as carbonation, evaporation, and crystallization, the raw juice is converted to a thick syrup which has around 95% of sugar concentration. The resulting sugar crystal and syrup mix are then processed by a centrifugal decanter to provide pure sugar crystals.
6. Nanotechnology
TRANSPARENT ELECTRODES
Technologies like photovoltaics, displays, touch panels, and many other devices widely use transparent electrodes in the sector of nanotechnology. For optoelectronic applications, silver nanowires (AgNWs) tend to be an extremely promising option for transparent conductive oxides. Transparent electrodes suffer from several drawbacks such as an expensive manufacturing process and brittleness. Silver nanowires are very attractive as they can be easily generated in high quantities and offer results that are best, particularly with regard to quality figures. The synthesis of AgNWs includes the tedious and lengthy purification process, which is hardly reproducible. The common purification technique is decantation and washing to remove co-produced nanoparticles and organics. This technique allows easy production of high quantity nanowires in a single run.
7. Blood Fractionation
If you have ever donated blood to save someone’s life, it is not necessary that the blood is used as a whole by the patient. Blood has many lifesaving elements, including red blood cells, platelets, and plasma. When you give whole blood, it is sent to the laboratory, where it is spun down and divided into various components. Each portion, red blood cells, platelets, and plasma, has specific medical uses, shelf life, and storage conditions. Blood fractionation is the process of fractionating whole blood or separating it into its component parts. Plasma proteins are separated by using centrifuge decanters. A centrifuge spins your blood to separate your red blood cells, platelets, and plasma. As the blood is separated, the heavier red cells sink to the bottom, and the liquid plasma rises, which is then carefully separated via decantation.
8. Cooking
It is always advised to wash the food before eating or cooking. While washing vegetables is an easy task, washing whole grains, such as rice, pulses, and lentils can be tricky. Decantation comes in handy while washing these edibles. For instance, after harvesting and processing paddy, the rice should be clean from impurities like husk and dirt before cooking. This can be done by rinsing a bowl of rice with water and then thoroughly cleaning it; so that the lighter dust particles and husk can float on the water while rice settles down. The impure water, then, can be separated by decantation.
9. Manufacture of Vinegar
Vinegar has been a frequent part of the human diet for thousands of years, and at the same time, it has a variety of other uses such as domestic, medical, and industrial. It plays an important role as an ingredient in salad dressings, ketchup, hot sauce, and other sauces. Vinegar typically contains 5–8% acetic acid by volume. Usually, acetic acid is produced by the fermentation of ethanol or sugars by acetic acid bacteria. Various fruits, grains, alcoholic drinks, and other fermentable materials are used to provide several flavours to vinegar. During the process of manufacturing and refining vinegar from vegetable material, it is usual to use the decanting process to remove the heavier fats derived from the raw material in the process.