How Does Activated Carbon Work in Water Purification?

Have you ever come across the term “Activated Carbon” in water filter commercials? As a user, it is very important to understand what these terms actually mean. In this article, we’ll provide you some information regarding activated carbons and how they work.

Read on to get detailed coverage of what activated carbon is, how it is formed, the different types of filters along with what impurities it does, or doesn’t cover.

So, let’s get started!

What Is Activated Carbon?

Activated carbon is essentially charcoal. It is full of pores that are ready to absorb a wide variety of impurities. However, absorb may not exactly be the right word. The actual process is adsorption. The basic working mechanism is that the impurities simply attach to the surface of the activated carbon.

Charcoal has a highly porous surface area that makes it perfectly suited for purification. In fact, one gram of activated carbon can boast of a surface area of nearly 3000 square meters. This charcoal can be collected from sources that are high in carbon. These can include any organic materials like wood, bamboo, coconut shells, coal, and so on.

How is Activated Carbon Formed?

So far, we’ve learned that charcoal is derived from carbon-rich sources. However, this still doesn’t form ‘activated’ carbon. While charcoal is naturally absorbent, with activation, it can develop the millions of pores that are required during purification. Activated carbon can be formed any of the two ways listed below:

Thermal Method

This method utilizes steam to turn charcoal into activated carbon. It also requires an inert atmosphere, which is created by using gases like carbon dioxide, argon, or nitrogen. This process includes reducing the moisture present in charcoal. Furthermore, it goes through carbonization and is finally treated with steam.

Chemical Method

In the chemical method, the charcoal is made to react with certain chemicals before carbonization. Carbonization is the process where carbon is heated in the absence of air. The chemicals used are typically high-strength acids, bases, or salt. The end result is a solid and porous activated carbon.

How does Activated Carbon work?

Activated carbon consists of a variety of pores. These can be classified into micropores, mesopores, and macropores. The quantity, as well as the distribution of these pores, determines the quality of any activated carbon. The contaminants then cling to these pores to provide you with clean water.

The ideal activated carbon used in filtration processes would offer a broad range of these pores in order to target a wide range of impurities. Generally, the larger pores target sediments as well as mineral impurities, whereas the smaller ones help remove bad taste and odor.

The adsorption process is aided by the fact that all molecules have an attractive property. This property helps the materials adhere to the carbon more readily. The carbon surface also carries a stronger attractive force than that of the impure water. Usually, organic impurities are more easily absorbed.

The only condition is that the contaminants must be smaller than the pore sizes available in any activated carbon. This condition is crucial as the impurities will need to be trapped and accumulated inside these pores. All of these largely have to do with physical adsorption.

Another way an activated carbon can remove impurities is through a chemical reaction. This reaction is most commonly seen during chlorine filtration. During this process, the incoming chlorine simply reacts with the carbon to form chloride ions. This reaction, thus, helps separate chlorine from water to give pure water.

Types of Activated Carbon Filters

Activated carbon is very commonly used for water purification. Generally, a carbon filter is further coupled with a secondary filter for higher efficiency. This second filter can be silver or a UV lamp to target microorganisms or other impurities, depending on your needs. The most commonly used activated carbon filters for water purification are described as follows:

1. Powdered Activated Carbon (PAC) Filters

These carbon filters tend to have smaller pore sizes than the GAC filters. The powdered activated carbon forms a densely packed block of carbon. This block helps keep the carbon stationary while the impure water flows through. With this, every pore is utilized to adsorb the contaminants. Since the pores on this filter are very fine, it can target even the much smaller molecules of impurities.

The disadvantage of PAC filters is that since the carbon block remains stationary, the purification process can take more time. While it does have higher effectiveness, this carbon filter is not suited for places like large water plants. It has a limit on how quickly water can be filtered and would, thus, be more suited for households.

2. Granular Activated Carbon (GAC) Filters

Instead of a solid block of carbon, these filters sport a loose granule design. These usually come in cylindrical containers. To use it, you have to add water to this cylinder. After this, the loose granules of carbon work to remove the impurities. This method is much efficient as the water does not have to wait to pass through solid pores.

The drawback of this system is that water has a natural tendency to flow in a path of least resistance. This flow means that many of these activated carbon granules may simply be missed. It can, thus, leave many of these granular carbons underused. Similarly, they can also promote some bacterial growth as water remains largely stagnant during this process.

What Impurities Does Activated Carbon Remove?

Activated carbon is excellent at targeting a large variety of impurities. We have heard how it manages to trap all these contaminants into its pores. We know that it can keep your water supply clean and pure. But what exactly are these contaminants?

First and foremost, activated carbon is most effective at removing chlorine. It can remove up to 95% of chloramine compounds, which also includes any by-products and chloride. Activated carbon is known to remove 32 of the most common by-products of chlorine. It boasts of similar effectiveness against lead, zinc as well as copper. Furthermore, a PAC filter keeps you protected against nearly all microplastics.

In terms of metals, it provides a high degree of protection against heavy metals like mercury, fluoride, and nitrate compounds. Activated carbon has been tested to efficiently remove 14 of the most common pesticides. Not only this, but activated carbon can also reduce a large amount of the arsenic and asbestos that may be polluting your water supply. This also includes a large variety of pesticides and herbicides.

If limescale, i.e., calcium build-up, is a common problem for you, then an activated carbon filter has got you covered to some degree as well. Additionally, if these activated carbon filters are paired with other filters, then you should be able to receive the utmost purified water.

Impurities that Activated Carbon Cannot Deal With

As we’ve discussed above, activated carbon covers a large ground when it comes to water purification. However, no filter can be 100% effective against all impurities. As such, the following are the impurities that an activated carbon filter might miss:

Dissolved Materials

Dissolved materials can include salts or metals like iron. These molecules are tiny and can slip through the filter. However, these aren’t typically considered impurities and should not affect your health.


Unlike water ionizers that leave your water utterly devoid of any minerals, activated carbon filters know better. Activated carbon filters will not target the healthy minerals like magnesium, sodium, potassium, or calcium. These minerals are quite essential for your body and should not be considered impurities unless you have any health conditions.

Inorganic Compounds

Activated carbon filters can reduce the amount of inorganic compounds in your water supply. These compounds can include harmful substances like arsenic and asbestos. The carbon filters can target and reduce about 30-70% of these compounds. However, some of it might still be left behind.


Activated carbon filters will usually need a secondary filter to work effectively at removing microorganisms. This means that it is not very good at removing bacteria or viruses from your water supply. If this is a concern, then you might want to consider adding a UV filter.

To summarize,

Activated carbon is highly porous charcoal that removes impurities via adsorption. It can be formed by using a thermal or chemical method. It is used in water purification in the form of Powdered Activated Carbon (PAC) or Granular Activated Carbon (GAC) Filter.

It can remove a wide variety of impurities, including but not limited to chlorine, lead, zinc, microplastics, and so on. It is very effective in water purification and leaves you with clean and fresh water that you need.

Frequently Asked Questions

1. Can activated carbon be reused?

Yes. You can reuse your activated carbon by baking out the odors it has collected. Cleaning out the pores inside this activated carbon at home can be quite tricky. This is why make sure you don’t reuse it more than two or three times.

2. How long do activated carbon water filters last?

It is advised not to use your activated carbon filters for over a year. Once the pores of the filter are full, there is a chance of leakage, which might leave your water worse than before treatment. It can be harmful to your health as well.

3. Can activated carbon filters be washed?

It depends on the brand you are using. Some activated carbon filters are labeled as washable, while others are not. In order to avoid damage to your filters, it is best to check the label for your filter.

4. Does a carbon filter remove bad smells?

Yes, carbon filters can be very effective at removing smells. However, you have to ensure that the filter is the correct size and also make sure that you have sufficient ventilation available.