Activated charcoal, also known as activated carbon, is a form of carbon that has been processed to have small, low-volume pores. These pores increase the surface area available for chemical reactions or adsorption, a process where certain particles are attracted to activated charcoal and stick to its surface.

The activation process typically involves treating the carbon source, which can be materials like coconut shells, wood, or coal, with hot gases or certain chemicals. This process 'activates' the charcoal by creating a network of tiny pores on its surface. This expanded network of pores in the activated charcoal gives it a very large surface area. To give you an idea of how large, just one gram of activated charcoal can have a surface area of up to 3000 square meters, which is roughly the size of three Olympic swimming pools.

This high degree of microporosity makes activated charcoal extremely effective at adsorption. It's widely used in a variety of applications, including water purification, air filtration, and in medical treatments to adsorb toxins or poisons from the body. In these applications, unwanted substances stick to the activated charcoal, effectively removing them from air, water, or the body.

The filtration principle of activated carbon, or activated charcoal, is primarily based on a process called adsorption, not to be confused with absorption.

Adsorption is a surface-based process where certain particles are attracted to activated carbon and adhere or stick to its surface. This occurs because activated carbon is extremely porous and has a large internal surface area. This extensive network of pores provides numerous binding sites for a wide range of organic and some inorganic compounds.

When water or air passes over the activated carbon, the pollutants, chemicals, and other impurities present in them are attracted to the carbon particles. These impurities get trapped in the carbon's pores and adhere to the carbon surface, effectively removing them from the medium they were in.

This process can continue until all the available pores or surface sites in the activated carbon are filled up with impurities, at which point the carbon is said to be 'saturated' and needs to be replaced or reactivated.

It's worth noting that activated carbon is particularly effective at removing organic compounds and can also help to remove chlorine, certain types of gases, odors, and even some heavy metals. However, it's not effective at removing all types of pollutants. For example, it cannot remove microbes, sodium, nitrates, fluoride, and hardness from water.

So, the filtration capability of activated carbon is highly dependent on the physical properties of the substances it needs to remove, including their size, shape, and chemical nature.

Activated carbon plays a significant role in the water filtration field due to its excellent adsorption properties. Here are some ways it is used:

Drinking Water Treatment: Activated carbon is commonly used in both household and commercial water filtration systems to remove impurities from drinking water. It can effectively reduce certain organic compounds, chlorine, and unpleasant tastes and odors, thereby improving the water's overall quality and taste.

Wastewater Treatment: In industrial processes, activated carbon is used to remove organic compounds from wastewater before it is released back into the environment. This is particularly important in industries such as pharmaceuticals, chemicals, and food and beverage production, where wastewater can contain a variety of organic pollutants.

Groundwater Remediation: Activated carbon can be used to treat contaminated groundwater by absorbing pollutants, such as volatile organic compounds, pesticides, and other harmful substances.

Aquarium Filtration: In aquariums, activated carbon is used to remove impurities, odors, and discoloration from the water to create a healthier environment for aquatic life.

Swimming Pool Filtration: Activated carbon is also used in swimming pool filters to remove chlorine, organic materials, and other compounds that can affect water clarity and purity.

In all these applications, water is typically passed through a bed of activated carbon (either granular or in block form). As the water flows through, impurities are adsorbed onto the carbon's surface and trapped within its pores, leaving the water cleaner as it exits the filter. Over time, the activated carbon will become saturated with trapped impurities and will need to be replaced or regenerated.

It's important to note that while activated carbon is a powerful filtering agent, it doesn't remove all types of contaminants. For example, it's not effective at removing minerals, salts, and certain types of inorganic compounds. Therefore, it's often used in combination with other water treatment processes to ensure comprehensive water purification.

Activated carbon plays a crucial role in air filtration as well, thanks to its excellent adsorption properties. Here are some of its key applications in this field:

Air Purifiers: Many air purifiers use activated carbon filters to remove volatile organic compounds (VOCs), odors, and other gaseous pollutants from the air. This helps to improve indoor air quality, particularly in spaces where chemicals, smoke, or strong odors are present.

HVAC Systems: In heating, ventilation, and air conditioning (HVAC) systems, activated carbon filters can help to clean the circulated air, removing odors and harmful pollutants. This helps to maintain a healthier indoor environment.

Industrial Air Filtration: In industries where harmful gases are emitted, activated carbon filters can play a crucial role in removing these pollutants from the air, protecting both the environment and workers' health.

Gas Masks and Respirators: Activated carbon is a key component in gas masks and respirators. It can adsorb toxic gases, protecting the wearer from inhaling them.

Kitchen Hoods: Activated carbon filters are also used in kitchen exhaust hoods to remove cooking odors and smoke, helping to keep the kitchen air clean and fresh.

Vehicle Cabin Filters: In vehicles, activated carbon cabin filters can help to remove outside pollutants, odors, and harmful gases from the air inside the cabin, creating a healthier environment for the passengers.

In all these applications, air is passed through an activated carbon filter. The pollutants in the air are attracted to the carbon particles and get trapped in the filter, effectively cleaning the air. Over time, the activated carbon filter will become saturated with these pollutants and will need to be replaced.

While activated carbon is highly effective at trapping certain pollutants, it's important to remember that it doesn't remove all types of air contaminants. For example, it won't remove dust, pollen, and other particulate matter. Therefore, it's often used in combination with other types of air filters to provide comprehensive air filtration.