What’s The Difference Between Solvent Distillation And Solvent Extraction?

Navigating the complexities of hazardous waste management can become particularly challenging if your business is seeking environmentally friendly solutions for handling spent solvents. 

Finding the right disposal solution for the solvents your manufacturing process generates is critical, not only to minimize your environmental impact but to save economic resources as well.

You may have come across solvent distillation and solvent extraction as methods for mitigating the environmental impact of spent solvents while efficiently managing your disposal. Is there a difference between the two methods, and which is better?

What Are Solvents And Solutes?

To understand how solvent extraction and solvent distillation work, it’s best to begin by exploring solvents and solutes and the role they play in the process.

A solvent is a molecule that can dissolve other molecules. These molecules are 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 homogenous mixture cannot be separated physically. High temperatures or another chemical process must be applied to the solution in order to separate the solvent from the solute. 

Some examples of solvents include:

• Water: Often considered the universal solvent, water is commonly used as a solvent in many processes.
• Ethanol: Used as a solvent in the pharmaceutical, cosmetic and food industries. It is also a common solvent for herbal extractions.
• Acetone: A widely used solvent in the paint and nail polish remover industry.
• Methanol: Used as a solvent in the production of formaldehyde and other chemicals.
• Hexane: Commonly used in the extraction of vegetable oils from seeds and nuts.
• Chloroform: Historically used as an anesthetic and in the production of certain pharmaceuticals.
• Toluene: Found in paints, thinners, and adhesives. It is also used as a solvent in the production of some plastics.
• Diethyl Ether: Used as a solvent in laboratories and in the pharmaceutical industry.
• Petroleum Ether: A mixture of hydrocarbons used as a solvent in various processes.
• Dimethyl Sulfoxide (DMSO): Commonly used as a solvent in pharmaceutical and chemical applications.

These are just a few examples, and the choice of solvent depends on the specific application and the properties of the substances being dissolved or processed.

What Is Solvent Extraction?

Now, let’s take a closer look at the solvent extraction process. Solvent extraction is a separation technique where a solute is transferred from one phase (usually a liquid) to another by using a solvent. The solute is dissolved in the solvent, and the resulting solution allows for the selective extraction and separation of specific components based on their solubility properties.

Solvent extraction is commonly used in industries such as food processing for the extraction of oils, mining for the extraction of metals, and pharmaceuticals for the isolation of active ingredients.

Now, let’s take a look at solvent distillation and whether this common process can benefit your manufacturing business.

What Is Solvent Distillation?

Solvent distillation involves taking a liquid or vapor mixture of two or more substances and separating it into its component fractions of desired purity. 

This process separates the solvents from other substances through the application of heat. The basic principle is to heat a liquid mixture containing solvents, causing the solvent to vaporize. The vapor is then condensed back into a liquid form, resulting in the separation and recovery of the solvent.

The general steps in solvent distillation include:

• Heating: The liquid mixture, which includes the solvent and other components, is heated to increase the temperature of the solvent.
• Vaporization: As the temperature rises, the solvent undergoes a phase change from liquid to vapor, leaving behind the non-volatile components.
• Condensation: The solvent vapor is then cooled and condensed back into a liquid form, resulting in the separation of the solvent from the original mixture.
• Collection: The condensed solvent is collected, and the remaining substances (residues) are left behind.

The use of heat is essential in driving the separation process by providing the energy needed to vaporize the solvent. The specific temperatures and conditions employed in solvent distillation can vary based on the solvents' properties and the separated substances.

Many solvents can be recycled, reprocessed and reused. Some of the most commonly recycled solvents include: 

• Aliphatic, such as mineral spirits and naphthas
• Aromatics, like toluene and xylene
• Halogenated hydrocarbons, such as fluorocarbons, methylene chloride, perchloroethylene and trichloroethylene
• Alcohols, such as isobutyl alcohol, isopropyl alcohol, n-butyl alcohol and methanol
• Ketones, like acetone, methyl isobutyl ketone and methyl ethyl ketone
• Esters, such as ethyl acetate

Solvent distillation is also widely used across many industries, from chemical manufacturing to pharmaceuticals, paints and coatings, electronics and waste management.

What Is The Difference Between Solvent Distillation And Extraction?

In solvent extraction, a solvent is used to selectively dissolve and extract specific components from a mixture. The solute is transferred from one phase (usually a solid or liquid) to the solvent phase. This is why solvent extraction is typically used to extract specific compounds or components from a mixture, such as oils from seeds or metals from ores.

In solvent distillation, this process separates the solvents from a mixture through the process of vaporization and condensation. The solvent is heated to produce vapor, which is then condensed back into a liquid, resulting in the separation of the solvent from other components. The primary purpose is to recover and purify solvents from mixtures, which can then be recycled and used in various industrial processes. 

One of the biggest differences between these two processes is that solvent extraction can purify a substance that is either in the liquid or solid phase. On the other hand, solvent distillation purifies a substance that is only in a liquid mixture.

Solvent extraction also operates at ambient or moderate temperatures without the need for high temperatures, whereas solvent distillation involves the application of heat to raise the temperature of the solvent for vaporization.

As we’ll dive into below, the solvent distillation process reduces waste and helps your business achieve cost-effective solvent recovery.

How Does Solvent Distillation Achieve High Sustainability?

As part of the solvent recycling process, solvent distillation is extremely environmentally friendly and sustainable. 

When halogenated and non-halogenated solvents are distilled and ultimately recycled, economic resources are saved by reducing the purchasing of virgin raw materials. This process also reduces the generation of waste through a strategic solvent recovery plan and further prevents that waste from being generated in the form of pollution. 

At Samex, our solvent recycling process further minimizes our impact on the environment through the use of highly energy-efficient technology that also results in a high recovery volume. This closed solvent distillation process ultimately reduces volatile organic compound (VOC) emissions and enables the recycling and sustainable processing of chemicals. 

In today’s strict regulatory landscape, environmental compliance is critical if your business generates hazardous waste. Solvent distillation allows your business to comply with these regulations by responsibly managing and minimizing your solvent waste. 

In the process, your business can meet your sustainability goals, mitigate the risks that come with hazardous waste disposal and position your company for long-term viability in the marketplace.