In chemistry, extraction is a procedure that involves separating a material from a matrix. Partition theory describes an equilibrium situation that occurs when a solute is distributed between two phases. There are two forms of extraction: liquid-liquid extraction (also known as solvent extraction) and solid-liquid extraction. Both extraction methods rely on the same principle: the separation of chemicals based on their relative solubility in two separate immiscible liquids or solid matter molecules.
- Liquid-liquid extraction
- Acid-base extraction
- Supercritical fluid extraction
Solid-liquid extraction
Solid-phase extraction
Maceration
Ultrasound-assisted extraction
Microwave-assisted extraction
Heat reflux extraction
Instant controlled pressure drop extraction
Liquid-liquid extraction:
Liquid-liquid extraction, often known as solvent extraction or partitioning, is a method utilized in a variety of industries. This method separates compounds by using two immiscible solutions, usually one aqueous and one organic. Laboratory technicians will move a solute from one solvent to another. To complete this transfer, the two liquids must come into touch and mix. Then comes phase separation, which causes the two immiscible liquids to separate again.
A feed solution containing the solute to be extracted and a solvent are used at the start of the operation. There are a few things to take into account while selecting a solvent in order to enable the most beneficial outcomes. The ease with which the solvent may remove the solute from the feed solution must be taken into account first. A noncorrosive solvent with acceptable recoverability should also be selected. Precise interfacial tension is also necessary between the phases; too little tension makes disengagement more challenging.
A lab technician will next combine the two solutions in a container and shake or swirl them together. This technique permits the molecules to dissolve in the solvent of your choice. Many professionals refer to this as partitioning. The phases can then settle, leaving the solute in the aqueous solvent, which is now known as the extract. The organic solvent, now devoid of the solute, is a raffinate.
As previously said, liquid-liquid extraction has a wide range of uses, resulting in a variety of approaches for the process. In smaller-scale chemical labs, a separator funnel is commonly used to perform batch single-stage extractions. This process typically includes dispersive liquid-liquid micro-extraction and direct organic extraction, processes that are particularly useful in the extraction of proteins and identification of pesticides.
Solid-liquid-extraction
According to the solid-liquid extraction concept, a solvent extracts soluble chemicals from a solid material made up of an inert matrix and an active agent. The extract, either solid or liquid, can be used in the extraction process.
Solid-liquid extraction, also known as leaching, is the process of dissolving a solid solute in a liquid phase and separating it from a solid mixture. Leaching has three primary components: solid solutes, soluble solids, and solvents. In most circumstances, the extraction rate is determined by the diffusion of soluble components inside the particles themselves.
As a result, the procedure is commonly referred to as diffusion extraction. Solid-liquid extraction is widely used in the food (e.g., extracting sugar from sugar cane or sugar beet; isolating vegetable oils from various seeds), pharmaceutical (e.g., extracting active components from medicinal plants), and hydrometallurgy (e.g., leaching metal ions from ores). For mathematical modeling of leaching, an ideal solid-liquid extraction is defined. The solvent added to the dry raw material is partly taken up by the solid material and the soluble ingredients are instantaneously dissolved. Often all the solute is already dissolved (e.g. sugar in sugar beet). The solution is then split into two parts. The external solution is called extract and the internal one raffinate (in the case of plant materials this is cell liquor).
Solid-liquid extraction methods The main methods of solid-liquid extraction are: Stationary solid-bed leaching, Counter-current, Volatile, Moving-bed leaching, Bollman extractor.
Applications
Extraction processes are specially recommended for separation of
• non-volatile components
• mixtures, which cannot be separated by other procedures
• mixtures, whose vapour-liquid-phase equilibria show azeotropic features
• temperature–sensitive components
Important applications of extraction procedures can be found in
• chemical industry (an organics, organics)
• chemical metallurgy (extraction of metallic salts from diluted brines)
• nuclear technology (reprocessing of nuclear fuels)
• environmental technology (waste water treatment)
• food technology (edible oil refining)
• pharmaceutical industry (extraction of agents)