Types of Liquid Liquid Extraction Units: Mixer-Settlers vs. Columns

Are you struggling to choose the right liquid-liquid extraction system for your industrial process?

If so, you’re not alone! 

Whether you’re extracting copper from ore, purifying pharmaceuticals, or refining biofuels, one critical decision can make or break your efficiency:

Mixer-settlers or extraction columns?

Both separate liquids, like oil and vinegar. 

But one operates like a series of washing machines, while the other works like a high-rise elevator for molecules. 

Pick wrong, and you could face costly bottlenecks in high-volume production or wasted floor space in compact facilities.

In this guide, we’ll cut through the confusion with a side-by-side comparison of these two extraction workhorses. 

Here’s what we’ll cover: 

• How mixer-settlers dominate mining (and when their flexibility backfires).
• Why columns rule oil refineries but aren’t suited to delicate separations.
• 5 key decision factors (including the hidden cost most engineers miss).

By the end of the blog, you’ll be able to identify which liquid-liquid extraction unit is best suited to your requirements.

Let’s dive in!

Mixer-Settlers vs. Column Liquid-Liquid Extraction Units: Table of Contents

• Mixer Settlers vs Column Liquid-Liquid Extractors: Table of Comparison
• What is Liquid-Liquid Extraction?
• What are Mixer-Settler Units in Liquid-Liquid Extraction?
• What are Column Units in Liquid-Liquid Extraction?
• Key Differences Between Mixer-Settler and Column Units
• Procure Precision Liquid-Liquid Extraction Units from Kjhil
• Mixer-Settlers vs. Column Liquid-Liquid Extraction Units: FAQs

Mixer Settlers vs Column Liquid-Liquid Extractors: Table of Comparison

Need a quick answer on which liquid-liquid extractor is best for you?

No problem – here’s a detailed overview of the key differences between the two types of LLE extractors:

Also Read: What to Consider When Choosing a Liquid-Liquid Extraction Unit?

What is Liquid-Liquid Extraction?

Liquid-liquid extraction (LLE) is a chemical process that separates components of a liquid mixture to help you separate a desired chemical from impurities or other undesirable materials. 

To do so, the LLE process uses a solvent that selectively dissolves the target compound and separates it from all other compounds and particles you don’t need.

You can see the basic principle of the LLE process in the shaking of oil and vinegar: they mix temporarily but separate naturally due to differing densities!

Let us quickly explore the three important components and aspects of the liquid-liquid extraction process: 

• Feed: The original liquid, such as penicillin broth containing impurities.
• Solvent: The added liquid (e.g., methanol) that “grabs” the desired material (pure penicillin).
• After mixing, the liquids separate, leaving behind two components:
• Extract: Solvent + extracted material (like methanol and penicillin).
• Raffinate: Depleted feed (like flavorless oil or impure water left behind).

Let me quickly show you how liquid-liquid extraction is used in different industries: 

Industrial Applications of Liquid-Liquid Extractions

• Mining: LLE helps extract copper from lower-grade ores.
• Medicine: Purifying penicillin from fermentation broth.
• Food & Beverage: Decaffeinating coffee/tea or refining vegetable oils.
• Wastewater: Removing pollutants like phenol.

As you can see, LLE has a wide range of industrial applications and is a very important scientific technique that allows us to separate and extract useful chemical compounds from undesirable ones.

What are Mixer-Settler Units in Liquid-Liquid Extraction?

Mixer-Settler units are like a series of washing machines (mixers) connected to settling tanks. 

Each “wash cycle” mixes the liquids thoroughly, then lets them separate completely before moving to the next stage. 

They’re especially used in mining and chemical industries for running industrial-grade and heavy-duty liquid-liquid extraction processes.

Working Mechanism

Mixer-settler extraction is divided into three distinct phases

1. Mixing Stage: A motor-driven impeller blends feed and solvent.
2. Settling Stage: The mixture flows into a calm tank where liquids separate by gravity (like oil/vinegar settling).
3. Multi-Stage Setup: Multiple mixer-settlers can be linked for higher purity (like repeating a wash cycle).

Let me show you why industrial-grade users prefer mixer-settler units over Column LLE processors. 

Advantages of Mixer Settler Units in Liquid-Liquid Extraction

• Flexibility: You can easily adjust the mixing time of Mixer Settlers and simply add more stages of mixing whenever you need to. 
• Reliability: Mixer Settlers act as an assembly line of liquid-liquid extraction, so it come with a simple design and minimal moving parts.
• High Recovery: Given its extremely precise and high recovery rate, mixer settler units are very effective for difficult separations like uranium processing.

Limitations of Mixer Settler Units in Liquid-Liquid Extraction

While it has several advantages, mixer settlers also come with their own set of limitations: 

• Large Footprint: Mixer settlers require more floor space than columns.
• Slower LLE Processes: Batch-wise processing isn’t ideal for high-throughput needs.

Industry Use Cases

With its unique combination of strengths and weaknesses, mixer settlers are primarily used in the following industries:

• Mining, especially copper refining (70% of global copper is separated using mixer-settlers).
• The nuclear energy industry uses mixer settlers to extract uranium from ore.
• The chemical industry uses LLE to recover acetic acid from water.

Next, let’s find out what column separators are and when they’re better than mixer settlers. 

What are Column Units in Liquid-Liquid Extraction?

Picture a tall, vertical pipe where the two liquids flow in opposite directions – like an elevator going down while another goes up. 

As they pass each other, materials transfer from one liquid to the other.

That’s exactly how a Liquid-Liquid Extraction process works through column units!

They are especially common in the petroleum and food processing industries.

Working Mechanism of Column Extractors

Unlike mixed-settlers that use a stage-wise process for separating compounds, column separators work continuously through a flow-based process.

The process consists of three main components.

• Heavy liquid (feed): Enters at the top, moves down.
• Light liquid (solvent): Enters at the bottom, rises up.
• Internal Structures (e.g., trays, packing) whose job is to maximize the contact between the two liquids.

Column Types

Column extractors also have three different types: 

1. Packed Columns: Filled with inert materials (like ceramic rings) to increase surface area.
2. Pulsed Columns: Use vibrations to enhance mixing (e.g., nuclear fuel processing).
3. Rotating Disc Columns: Mechanical discs boost efficiency (e.g., petrochemicals).

When Columns Outperform Mixer-Settlers

Column processors outperform mixer settlers in two different situations: 

• High-Volume Processing: Continuous flow suits large-scale operations (e.g., oil refineries).
• Space Constraints: Since column separators are vertically designed rather than horizontally spread out, they’re perfect for constrained spaces.

Typical Applications

Column separators are typically used in three main industries:

• The petroleum industry uses column separators to remove sulfur compounds from fuel.
• The food and beverage industry relies on supercritical CO2 columns to extract caffeine from coffee and tea.
• The pharmaceutical industry leverages column separators to extract compounds like penicillin and purify antibiotics.

Key Differences Between Mixer-Settler and Column Units



1.Footprint

• Column Separators: Tall and vertical, so they require minimal floor space but significant headroom (ideal for compact facilities).
• Mixer-Settlers: Wide and horizontal, so they need more floor area but no height constraints (suits sprawling industrial plants).

2. Separation Principle

• Column Separators: Continuous countercurrent flow: liquids move in opposite directions, with gradual separation along the column height.
• Mixer-Settlers: Discrete stage-wise contact: liquids are mixed and separated repeatedly in distinct compartments.

3. Residence Time

• Column Separators: Shorter contact time (seconds to minutes), suited for rapid, high-throughput processes.
• Mixer-Settlers: Longer residence time (minutes to hours), better for slow or complex separations.

4. Flexibility

• Column Separators: Once built, column separators will limit your flexibility since they can’t be moved very easily. Plus, they’re optimized for specific flow rates and chemistries.
• Mixer-Settlers: These are highly adaptable and can accommodate different mixing intensities and stages. You can even adjust the solvents very easily.

5. Maintenance

• Column Separators: Since they have complex internal parts like trays and packing equipment, column separators require specialized maintenance. However, they also have fewer moving parts compared to mixer settlers!
• Mixer-Settlers: These have relatively simple mechanics with agitators and pumps, but more components to service across multiple stages. So, even routine maintenance might require more time.

6. Best For

• Column Separators: Large-scale, continuous operations, such as petroleum refining and high-volume chemical production.
• Mixer-Settlers: Batch processing, sensitive materials (pharmaceuticals, mining), or when you need precise control over the extraction process.

Procure Precision Liquid-Liquid Extraction Units from Kjhil

Liquid-liquid extraction is the invisible hero behind everything from clean fuel to life-saving drugs, but the real magic happens when you pair the right extraction unit with your specific process.

As we’ve seen:

• Mixer-settlers extraction is suited to precise, multi-stage separations (like mining or pharmaceuticals).
• Columns dominate high-volume, continuous operations (think oil refineries or food processing).

Still unsure which system fits your goals? Here’s how you can pick the one that best suits your requirements: 

1. Benchmark: If your competitors use one system, their results might hint at the right choice.
2. Experiment: Pilot both methods with our experts to compare performance in your facility.
3. Optimize: Customize your unit for peak efficiency—whether it’s a compact column or a flexible mixer-settler array.

At Kjhil, we engineer industrial extraction equipment to make the most of the advantages of liquid-liquid extraction units. 

So, if you need a solution tailored to your throughput, space, or budget, why not connect with us?

We’ll help you audit your current process, recommend the ideal extraction tech, and deliver a system built exclusively for your operational demands.

Reach out to us, share your objectives, and get high-quality LLE units for your production facilities!

Mixer-Settlers vs. Column Liquid-Liquid Extraction Units: FAQs

1. Which extraction unit is better for high-volume production?

Extraction columns are ideal for high-volume, continuous processes (like petroleum refining). Their vertical design and countercurrent flow handle thousands of liters per hour efficiently. Mixer-settlers, while precise, operate in batches and can’t match this scale.

2. When should I choose mixer-settlers over columns?

Pick mixer-settlers over columns if you:

• Need multi-stage precision (e.g., uranium extraction).
• Handle sensitive materials (pharmaceutical intermediates).
• Require flexible adjustments (solvent ratios, mixing time).

Columns struggle with these scenarios due to their rigid designs!

3. Can I combine mixer-settlers and columns in one system?

Yes, you can combine mixer-settlers and columns! Hybrid setups are common in industries like mining:

• Use mixer-settlers for initial rough extraction.
• Pass the intermediate to a column for final purification.
  This balances flexibility and throughput.

4. Which unit is more cost-effective for small-scale operations?

Mixer-settlers typically win for small-scale or batch processes because:

• Lower upfront costs (simple design).
• Easier maintenance (no specialized parts).

Columns become cost-effective only at large scales.

5. How do I prevent emulsions or poor separation in these units?

For mixer-settlers:

• Reduce agitator speed to minimize stubborn emulsions.
• Add coalescers to settling tanks.

For columns:

• Optimize internal trays/packing for your solvent pair.
• Control flow rates to avoid flooding or “channeling.”

Still unsure? Consult Kjhil’s engineers to diagnose your specific challenges!