Solvent Extraction Processes
Liquid Liquid vs Liquid Solid Extractions
Liquid liquid extraction, also known as partitioning, is a separation process of using immiscible (non-mixing) liquids with the end result of isolating components of the mixture based on the differences in solubility.
Solid Liquid Extraction, otherwise known as leaching, is the process of removing a soluble compound from a solid using a liquid solvent.
Both of these extraction methods are commonly used throughout many industries with a wide variety of applications like biotechnology, herbicide isolation, and recovery of organic materials. Another example is extraction of CBD and hemp products. When extracting CBD from hemp plants, seeds, and/or oil, using safe and effective practices is essential. The extraction processes related to CBD and hemp are complex, mainly due to terpenes and cannabinoids are being very sticky and trying to remove from the desired compound like a cannabis plant or seed takes the correct mixture of organic compounds. There are multiple extraction processes available to extract the desired compound which include supercritical CO2, hydrocarbons, and ethanol extractions. All of which have their pros and cons which are later discussed in the article but ultimately result in safe and efficient in CBD/hemp extraction.
Extraction Processes
For liquid liquid extraction, typically, one liquid is a water-based, polar solvent and the other liquid is an organic, carbon-based solvent. These liquids are combined together and added with the desired solute such as cannabinoids. The polarity of the solute will decide which solvent becomes enriched. High polarity solutes will mix better with aqueous solvents like water. Low polarity solvents mix better with organic solvents like acetone, methanol, and benzene. This phenomenon is the basis for the separation technique called separation funnel extraction where compounds are separated based upon their relative affinities for one or the other solvents.
Figure 1 The initial mixture (A+C) and the solvent (B) are introduced and mixed together. The desired compound (A) transfers into the solvent (B). After the mixture, the two phases settle and are obtained.
The process for Solid liquid extraction differs slightly from liquid-liquid extraction but still achieves the same end goal. Solid liquid extraction takes the desired solid phase and grind it down to a biomass. With respect to the extraction of hemp or cannabis the general grounded down material is the cannabis plant. Then a solvent such as hexane, ethanol, or butane is added to the biomass to dissolve and extract the desired molecules from the biomass. The molecules that are dissolved from the biomass are referred to as solutes and are a mixture of the targeted/desired compounds like THC, CBD, or any other cannabinoids.
Figure 2 Before extraction (Left): solvent, extraction material, transition component. After Extraction (right): depleted solid material, solvent with desired component.