Difference Between Decantation and Filtration

The key difference between decantation and filtration is that decantation separates two components in a mixture by pouring off one component, whereas filtration separates two components by filtering off one component.

Both decantation and filtration separate two components in a liquid-solid mixture or a mixture of two immiscible liquids, under the force of gravity. However, filtration uses a filter paper or another suitable filter for this separation. But, decantation is just pouring off of the liquid to isolate the solid or the other liquid in the mixture. Therefore, filtration is the most accurate method out of the two, but decantation is also useful in some occasions.

CONTENTS

1. Overview and Key Difference
2. What is Decantation 
3. What is Filtration
4. Side by Side Comparison – Decantation vs Filtration in Tabular Form
5. Summary

What is Decantation?

Decantation is the analytical technique that involves the separation of two immiscible substances via pouring off one substance to isolate the other substance on the container. We can use this process for two immiscible liquids and a mixture of a liquid and a solid (a suspension).

If the mixture of the two immiscible liquids to be separated is in a container, we can simply pour off the less dense liquid layer (on the top of the container). So, this can separate the less dense liquid from the high dense liquid. Similarly, if we are going to separate a liquid from a solid in a suspension, we can pour off the liquid into a different container so that the solid will remain in the container.

However, this separation is generally an incomplete separation; compared to filtration, it is less precise. That is because, there can be liquid still remaining on the solid (or with the other immiscible liquid) and if we are going to pour off the liquid further, the solid (or the other liquid) may also drop into the second container. Examples for decantation includes the separation of liquid and precipitate after a precipitation reaction, cleaning mud water by removing mud from water, etc.

What is Filtration?

Filtration is an analytical technique for the separation of a solid from a liquid. This process helps to remove solids in a fluid via passing the fluid through a barrier that can hold the solid particles via a physical, mechanical or biological operation. Here, the fluid can be a liquid or a gas. The fluid that we get after the filtration is the “filtrate”. The barrier that we use for the filtration is the “filter”. It can be a surface filter or a depth filter; either way, it traps solid particles. Most of the times, we use filter paper in the laboratory for the filtration.

Usually, filtration is not a complete process that leads to purification. But it is precise compared to decantation. That is because some solid particles may go through the filter while some fluid may remain on the filter without going to the filtrate. The different types of filtration techniques include hot filtration, cold filtration, vacuum filtration, ultrafiltration, etc.

The major applications of the filtration process include the followings:

• To separate liquid and solid in a suspension
• Coffee filter: to separate the coffee from the ground
• Belt filters to separate precious metal during mining
• To separate crystals from the solution during the recrystallization process in organic chemistry
• Furnaces use filtration to prevent the furnace elements from fouling with particulates

What is the Difference Between Decantation and Filtration?

Both decantation and filtration separate two components in a liquid-solid mixture or a mixture of two immiscible liquids, under the force of gravity. The key difference between decantation and filtration is that decantation separates two components in a mixture via pouring off one component, whereas filtration separates two components via filtering off one component.

Below infographic provides a more detailed comparison related to the difference between decantation and filtration.

Summary – Decantation vs Filtration

Both decantation and filtration separate two components in a liquid-solid mixture or a mixture of two immiscible liquids, under the force of gravity. However, the key difference between decantation and filtration is that decantation separates two components in a mixture via pouring off one component, whereas filtration separates two components via filtering off one component.

Reference:

1. Helmenstine, Anne Marie. “What Is Decantation and How Does It Work?” ThoughtCo, Oct. 6, 2019, Available here.

Image Courtesy:

1. “Oil & water 2” By bitjungle (CC BY-SA 2.0) via Flickr
2. “Vacuum-filtration-diagram” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia