Activated charcoal, also known as activated carbon, is a highly porous material that is used for a variety of applications due to its ability to adsorb and remove impurities from air, water, and other substances. It is created by carbonizing organic materials like coconut shells, wood, or bamboo, activating the carbonized material with a physical or chemical reaction that increases its surface area and develops a vast network of interior pores, and then combining the resultant material. Numerous sectors, including medicine, environmental cleanup, and the purification of food and water, make extensive use of activated charcoal. Its special qualities make it a useful and adaptable material for a wide range of uses.
Raw materials of activated carbon
Several chemical substances that are high in carbon are used to make activated charcoal. Coconut shells, wood, bamboo, and peat are some of the most typical basic materials used to make activated charcoal. Each of these raw materials has distinct qualities that may have an impact on the end product’s effectiveness and caliber.
One of the most frequently used raw materials for the creation of activated charcoal is coconut shells. They have a significant carbon content, are abundant, and are renewable. Low-ash activated charcoal made from coconut shells is especially good at removing impurities from water and air.
Oak, cherry, and hickory are just a few of the kinds of wood used to make wood-based activated charcoal. Activated charcoal made from wood is frequently used because of its high ability for adsorption.
Bamboo is a quick-growing, environmentally friendly raw material that is widely used in the manufacture of activated charcoal. Because of its distinctive microstructure and large surface area, bamboo-based activated charcoal is especially good at adsorbing impurities from air and water.
In wetlands, vegetation that has partly decomposed forms peat, a dark, organic substance. Due to its high adsorption capability, peat-based activated charcoal is frequently used in solvent recovery and gas purification.
The quality and efficacy of the activated charcoal created depend greatly on the choice of raw material. The pore structure, surface area, and adsorption capacity of the activated charcoal can be influenced by the physical and chemical characteristics of the raw substance. The right raw material must be chosen based on the intended purpose and performance specifications. For instance, activated charcoal made of wood is more effective at purifying gases than activated charcoal made of coconut shell, which is frequently used in water treatment.
Activated carbon production process
In the activated carbon plant, raw materials are first carbonized, and then they are either physically or chemically activated to create activated charcoal. A network of internal pores is formed during the activation process, expanding the material’s surface area and producing a highly adsorbent substance.
Charcoal can be activated in two different ways: physically and chemically.
Physical activation entails heating the organic material in the absence of air, usually at temperatures between 600 and 900 °C. The volatile matter and impurities are forced off during this process, leaving behind a char with a high carbon content. The char is then “activated” by heating it to a higher temperature, usually between 800-1000°C, while being exposed to an oxidizing atmosphere, like steam or carbon dioxide. As a result of the carbon’s reaction with the gas at a high temperature, a network of holes is formed, increasing the surface area.
Chemical activation involves impregnating the organic material with a chemical agent, such as phosphoric acid, potassium hydroxide, or sodium hydroxide, before heating it to a high temperature. The chemical agent reacts with the organic material, creating a network of pores and increasing the surface area.
Activated charcoal is usually produced through a number of steps:
- Raw material selection: The finished product can be impacted by the quality and properties of the raw material. Based on the intended characteristics of the activated charcoal, the raw material is selected.
- Carbonization: To remove volatile matter and impurities, the raw material is heated in the lack of oxygen, leaving behind a char.
- Activation: The char is then given a physical or chemical activation, which results in the formation of an interior pore network that expands the surface area.
- Washing: To get rid of any last-minute impurities, activated charcoal is rinsed.
- Drying: To get rid of any moisture, activated charcoal is desiccated.
Factors that can affect the quality of activated charcoal produced include temperature, activation time, and the type and concentration of the activating agent. High temperatures and longer activation times generally result in higher surface area and pore volume. However, excessive heat or prolonged activation can also lead to decreased adsorption capacity or the formation of a less stable structure. The type and concentration of the activating agent can also affect the pore structure and adsorption capacity of the activated charcoal.
The techniques of physical and chemical activation each have benefits and drawbacks. Compared to chemical activation, physical activation is easier to perform and uses fewer chemicals, but it could produce materials with smaller pore volumes and adsorption capacities. Contrarily, chemical activation can result in activated charcoal with greater pore volume and adsorption capacity, but it also necessitates the use of chemicals, which can be costly and possibly dangerous.
Chemical composition of activated carbon
Carbon makes up the majority of activated charcoal, with typical carbon contents varying from 70% to 95%. Given that carbon is renowned for having a high capacity to adsorb a variety of contaminants, activated charcoal’s high carbon content is a crucial component of this capacity.
Activated charcoal can also hold varying concentrations of oxygen, hydrogen, and nitrogen in addition to carbon. Both the raw material used to make the charcoal and the activation procedure itself may contain these components.
Activated charcoal may contain contaminants as well, and these impurities may affect the material’s characteristics and effectiveness. Ash, which can originate from the raw material or the activation process, and volatile organic compounds (VOCs), which can be created during the activation process, are examples of common impurities. Ash can decrease the activated charcoal’s ability to absorb contaminants, while VOCs can prevent it from doing so.
The surface chemistry of the activated charcoal can also be impacted by the existence of additional components and impurities, which can alter its selectivity for various contaminants. For instance, the surface of activated charcoal may exhibit oxygen-containing functional groups, which may enhance the material’s affinity for polar substances like water and particular gases.
Physical properties of activated carbon
The effectiveness of activated charcoal as an adsorbent substance depends heavily on its physical characteristics. The surface area and porosity, pore size distribution, density and hardness, as well as color and flavor, are a few of the important physical characteristics.
The most crucial characteristics of activated charcoal are its surface area and permeability because these factors directly impact its ability to absorb substances. Activated charcoal has a very porous interior surface area that can be used for adsorption. Depending on the activation procedure and the raw material used, the surface area per gram can vary from a few hundred to several thousand square meters.
Pore size distribution is also an important factor in the performance of activated charcoal. The pores can be divided into different size ranges, including micropores, mesopores, and macropores. The size and distribution of these pores can affect the selectivity of the activated charcoal for different types of contaminants.
Density and hardness are other important physical properties of activated charcoal. The density of activated charcoal can range from 0.2 to 1.2 g/cm³, depending on the raw material and production process. Hardness is a measure of the resistance of the material to breakage or crushing, and is important for ensuring that the material can withstand handling and use in a given application.
Color and odor can also be important physical properties of activated charcoal, depending on the application. Activated charcoal can range in color from black to brown to gray, depending on the raw material and production process. Odor can also vary, depending on the presence of impurities or the raw material used. In some applications, the color and odor of activated charcoal can be important factors to consider.
Applications of activated carbon
Activated charcoal has a wide range of applications across various industries and fields, including medicine, industry, environmental remediation, and more. One of the primary reasons for its versatility is its unique set of physical and chemical properties, which make it suitable for different applications.
In numerous industries and disciplines, including medicine, industry, environmental remediation, and more, activated charcoal is used in a variety of applications. Its distinctive combination of physical and chemical properties, which fit it for a variety of applications, is one of the main causes of its adaptability.
In emergency situations involving poisoning and narcotic overdoses, activated charcoal is frequently used in medicine. It can adsorb toxins and chemicals in the digestive system, preventing them from being absorbed into the bloodstream, thanks to its high surface area and porosity. Additionally, it is helpful in medical uses due to its low toxicity and capacity to bind to specific drugs.
In industry, activated charcoal is utilized in industry as a catalyst support, gas purification, decolorization, and deodorization substance. It is efficient at removing impurities and contaminants from vapors and liquids due to its big surface area and porous structure.
In environmental remediation, activated charcoal is used in environmental remediation to cleanse contaminated earth and water as well as to trap and remove pollutants from the air. It is efficient at removing a variety of contaminants, including heavy metals, volatile organic compounds (VOCs), and other pollutants thanks to its selectivity and adsorption capability.