Subcritical Water Extraction: A Versatile and Green Extraction Method

Overview

Subcritical water extraction is an emerging green technology that uses water at elevated temperatures and pressures to extract a wide range of compounds. But how does it work? This guide will cover how subcritical water extraction works, its advantages, and more.

What is Subcritical Water?

Subcritical water is water kept at temperatures between 100°C and 374°C, and pressures high enough (often between 10 and 200 bar) to maintain it in the liquid state. In this phase, water’s physicochemical properties shift significantly.

For example, its surface tension decreases as the temperature rises, and its polarity becomes similar to organic solvents like acetonitrile. These changes allow subcritical water to dissolve a broader range of compounds, including nonpolar and moderately polar substances.

Advantages of Subcritical Water Extraction

Improved Solubility: At higher temperatures, water’s surface tension decreases, making it an excellent solvent for extracting a wide range of compounds, including those that are harder to dissolve (like lipophilic substances). This allows subcritical water extraction to process complex materials efficiently.
Enhanced Mass Transfer: Under subcritical conditions, mass transfer is significantly improved. The higher temperatures increase diffusion rates and reduce the viscosity of the solvent layer around particles, allowing the water to penetrate deeply into the material. This leads to faster processing and better extraction yields.
Reduced Use of Hazardous Solvents: Subcritical water extraction replaces traditional organic solvents with water, reducing the environmental impact and creating a safer, more sustainable extraction method.

Subcritical Water Extraction and Supercritical CO2

Subcritical water extraction integrates seamlessly into sustainable workflows. For example, pairing it with supercritical or near-supercritical CO2 in a drying step enhances the process.

After extraction, introducing CO2 at high pressure helps remove residual moisture, leaving behind high-quality, concentrated extracts. This drying approach eliminates the need for additional solvents, improves efficiency, and reduces environmental impact.

Upgrade Your Extraction Process With extraktLAB

Subcritical water extraction is a breakthrough in sustainable, efficient methods. At extraktLAB, we offer advanced systems and expertise to help you maximize yields and minimize environmental impact. Contact us now to learn more about our solutions.