Solvent extraction is a process in which compounds are separated based on their relative solubilities.
This treatment method involves using a solvent - a fluid that has the ability to dissolve another substance.
Solvent extraction is used across multiple industries, including during the processing of perfumes and vegetable oil. It’s also commonly used in petrochemical refining industries.
Solvent extraction is used to separate hazardous contaminants from sludge and sediments as well. This can be especially beneficial for hazardous waste generators since solvent extraction ultimately reduces the amount of hazardous waste that must be treated.
Solvent extraction does not destroy a compound. It instead separates it, a process that can provide several valuable benefits depending on the industry in which the process is used.
What Is A Solvent?
A solvent is a molecule that can dissolve other molecules, known as solutes. A solvent can be solid, liquid or gas.
A solvent’s molecules pull apart the solute’s molecules, and eventually the solute’s molecules become evenly distributed throughout the solvent. This homogeneous mixture cannot be separated physically.
That means heat or another chemical process must be applied to the solution in order to separate the solvent from the solute.
Popular solvents include water and organic compounds like benzene, tetrachloroethylene and turpentine.
What Is Solvent Extraction?
Solvent extraction is the act of removing something or separating it. This must be done through force and this process occurs over the course of two different immiscible phases.
Immiscible liquids (liquids that do not dissolve in one another) form layers when put together. This is because each liquid differs in polarity, or orientations. The order of the phases, whether a particular liquid is on top or on the bottom, is determined by its density.
For example, if you use ether and water during the extraction process, water has a higher density than ether. Therefore, water will be the bottom phase.
Your method for extraction may vary depending on your equipment, but in its most simplistic form, extractions often use some kind of separatory funnel. The liquid mixture that is to be separated is first added to the funnel. When the two extraction solvents are then added to the funnel, they should separate into two phases.
After forcibly shaking the funnel and allowing it to stand for several minutes, the two layers can be collected. In the end, the target molecule for extraction will be located in one of the solvents.
More recently, according to a ScienceDirect report, new separation techniques are combining the solvent extraction process with additional technologies to enhance genetic engineering techniques. These include liquid membrane extraction and super critical fluid extraction.
How Does Extraction Compare To Distillation?
One of the main differences between solvent extraction and solvent distillation is that solvent extraction can purify either a substance that is a liquid or one that is in a solid phase. Solvent distillation purifies a substance that is only in a liquid mixture.
There are various types of distillation techniques, from steam distillation to vacuum distillation. The difference among these is the technique used to separate compounds.
At Temarry Recycling, solvent distillation recovery is based on how the vapor of a boiling mixture will be richer in low boil point components. These include acetones, ketones, aliphatic hydrocarbons and alcohols.
When vapor is cooled and condensed, the liquid condensate becomes a valuable product that can be sold back into industry. The higher boiling point portion of the original mixture that does not vaporize remains in the bottom of the recovery still used on site for the distillation process. One benefit of using this type of distillation process is that the portion remaining in the recovery still is valuable as an alternative fuel source for facilities such as cement kilns.
Solvent recycling offers a more environmentally-friendly way to dispose of hazardous substances, and distillation is the most common method of solvent recycling.
Is Extraction Environmentally Friendly?
Environmentally friendly solvents can be used in the extraction process. Water is the classic example.
In recent years, there has been a higher emphasis as well on developing and using more green solvents. Through the processing of agricultural crops, these green solvents - also known as biosolvents - are derived.
Solvent extraction also has the advantage of low energy consumption, compared to solvent distillation.
However, solvent distillation can provide many environmentally-friendly benefits as well, especially when used as part of a Closed Loop Recycling and Recovery system.
At Temarry Recycling, solvent distillation is part of the circular economy because nothing is wasted and a marriage is created between solvent distillation and waste to energy treatments.
This closed-loop system allows received waste to be treated and turned back into a reusable product. For this to occur, solid wastes received are thermally treated at 1500 degrees F to generate steam. This steam is then used to power our solvent recovery systems.
You can read more about this process in our article, Solvent Distillation And The Energy Recovery Process Explained.