What is the Difference Between Cation Exchange Capacity and Anion Exchange Capacity

The key difference between cation exchange capacity and anion exchange capacity is that cation exchange capacity shows the quantity of negative charge available to attract cations, whereas anion exchange capacity shows the positive charge that is available to attract anions in a solution.

Resins are important substances in the field of analytical chemistry. There are two types of resins as cationic resins and anionic resins. These are the two most common resins that are useful in ion exchange processes. Accordingly, we can name the processes consisting of this resin as cation exchange or anion exchange processes.

CONTENTS

1. Overview and Key Difference
2. What is Cation Exchange Capacity 
3. What is Anion Exchange Capacity
4. Cation Exchange Capacity vs Anion Exchange Capacity in Tabular Form
5. Summary – Cation Exchange Capacity vs Anion Exchange Capacity

What is Cation Exchange Capacity?

Cation exchange capacity can be defined as the measurement of the number of cations that can be retained on soil particle surfaces. Usually, negative charged atoms or molecules on the soil surface can bond with positive charged atoms or molecules, allowing the exchange of these ions with other positively charged particles in the soil water that surrounds the soil particles.

The cation exchange is a method from which solid materials in the soil can alter the chemistry of the soil. It can affect many aspects of soil chemistry. Moreover, we can use it as a measurement of soil fertility. This is because it can indicate the capacity of the soil to retain several nutrients in plant-available form. Furthermore, cation exchange capacity can indicate the capacity of the soil to retain pollutant cations such as lead cations.

Basically, cation exchange capacity is the amount of positive charge that gets exchanged per mass of soil. It arises from various negative charges in soil particle surfaces such as clay minerals and soil organic matter. Moreover, soil pH can affect the cation exchange capacity of the soil.

What is Anion Exchange Capacity?

Anion exchange capacity is the number of negative charges that are retained by 100 grams of soil. We can express this value as 100 grams of soil. It gives the total exchangeable anions that soil can absorb. Additionally, all soil clays and organic matter have comparatively a small amount of positive charge sites that can retain anions in dynamic equilibrium along with the soil solution. The anion exchange capacity can be abbreviated as AEC. The ion exchange capacity of a particular soil is higher when the cation exchange capacity is high.

What is the Difference Between Cation Exchange Capacity and Anion Exchange Capacity?

Cation exchange capacity is the measurement of the number of cations that can be retained on soil particle surfaces. Anion exchange capacity, on the other hand, is the number of negative charges that are retained by 100 grams of soil. The key difference between cation exchange capacity and anion exchange capacity is that cation exchange capacity shows the quantity of negative charge available to attract cations, whereas anion exchange capacity shows the positive charge that is available to attract anions in solution.

The below infographic presents the differences between cation exchange capacity and anion exchange capacity in tabular form for side by side comparison.

Summary – Cation Exchange Capacity vs Anion Exchange Capacity

The key difference between cation exchange capacity and anion exchange capacity is that cation exchange capacity shows the quantity of negative charge available to attract cations, whereas anion exchange capacity shows the positive charge that is available to attract anions in solution.

Reference:

1. “Anion Exchange: Meaning, Factors And Importance | Soil Colloids.” Soil Management India, 2022.

Image Courtesy:

1. “CEC pH” By Kyle MoJo & Kazem Zamanian (CC BY-SA 4.0) via Commons Wikimedia