What is Liquid–Liquid Extraction?

Liquid-liquid extraction (LLE), also known as solvent extraction or partitioning, is a fundamental method in analytical chemistry used to separate compounds based on their relative solubilities in two different immiscible liquids. Usually, these liquids consist of water (aqueous phase) and an organic solvent (organic phase).

This calculator utilizes the Nernst Distribution Law. The key factor is the Partition Coefficient (K_d), which defines the ratio of concentrations of a solute in the two phases at equilibrium. When multiple extractions are performed with smaller volumes of solvent, the process is significantly more efficient than a single extraction with a large volume of solvent.

How to Use the Calculator

To calculate your extraction efficiency, follow these steps:

• Initial Amount (W₀): Enter the total mass or concentration of the solute currently in the aqueous phase.
• Volume of Aqueous Phase: The volume of the liquid currently holding the solute.
• Volume of Organic Solvent: The volume of fresh solvent used for each extraction step.
• Partition Coefficient (K_d): Defined here as [Concentration in Organic Phase] / [Concentration in Aqueous Phase].
• Number of Extractions: How many times you repeat the process with fresh solvent.

FAQs

Why is multiple extraction better?

Mathematical derivation shows that for a fixed volume of organic solvent, dividing it into several portions and performing successive extractions removes more solute than using the entire volume at once. This is because each new portion of solvent shifts the equilibrium again.

What does a high K_d mean?

A high partition coefficient indicates that the solute prefers the organic solvent. This makes the extraction much easier and requires fewer steps to achieve high purity or recovery.