The Uses of Activated Carbon
Humans have been using activated carbon for thousands of years. For example, ancient Egyptians used wood char in the bronze manufacturing process. Around 400 BCE, Hippocrates recommended filtering water with wood char to prevent diseases and eliminate unpleasant taste and odor. During the late 18th century, activated carbon saw its first use in the industrial world as a decolorizing agent. Today, a variety of industries commonly use activated carbon, from gold mining to water purification. If you are new to the world of activated carbon, you likely have questions about specific applications and how activated carbon works. In this post, we will explore activated carbon and some of the ways various industries employ this highly versatile and cost-effective material.
In this article you will learn:
What is activated carbon
Activated carbon is a material produced from carbon-rich materials such as coal, wood, and nutshells. The carbon medium gets activated by exposure to steam and high heat without oxygen. This process opens up millions of pores between carbon atoms. The large network of pores in activated carbon provides an exceptionally large surface area. For example, a pound of carbon has over 35 acres, or almost 100 football fields, of surface area. The highly porous surface area adsorbs contaminants from gases or liquids. After the carbon is activated, it then gets crushed or pulverized. This process creates more particles with a greater outside surface to remove more contaminants.
The two most commonly used types of activated carbon are granular activated carbon (GAC) and powdered activated carbon (PAC). PAC offers incredible flexibility because users can easily adjust dosages to suit process conditions. PAC makes up about half the total production of activated carbon. It sees the most use in wastewater treatment, as well as in the food and pharmaceutical industries.
GAC has a larger particle size than PAC, resulting in more surface area. GAC plays a significant role in continuous processes in gas and liquid phase applications, such as gas purification, solvent recovery, air filtering, gold extraction, and drinking water treatment.
Unlike PAC, it's possible to regenerate GAC and use it more than once. Activated carbon works via adsorption, which is the process of attracting gas or liquid molecules to the surface of a solid substance.
During adsorption, molecules adhere to the pores in activated carbon like magnets. This process allows activated carbon to collect contaminants as streams of fluid or gas pass through.
Activated carbon has the best adsorption power of any material known to humankind. It is a cost-effective way to remove contaminants in a variety of applications, and it can also recover solvents and precious metals.
The many uses of Activated Carbon in the water treatment industry
Activated carbon often plays a role in the removal of organic compounds and chemicals, and it is common in water and wastewater treatment facilities.
For example, activated carbon removes the following contaminants from water to improve safety, taste, color, and odor:
THE DIFFERENCE BETWEEN STANDARD CARBON AND ACTIVATED CARBON
Activated carbon is commonly distributed in the United States for a wide range of industries. Activated carbon differs from standard carbon.
Activated carbon has been processed to create extremely tiny pores between the carbon atoms, thereby increasing surface area. Finer pores increase the surface area and improved the absorption of the activated carbon compound.
Industries that use Activated Carbon
Although activated carbon is an essential component of water treatment processes, it has many more applications. We will look at the various ways industries use activated carbon and its strong adsorptive properties, including its use in the water treatment industry.
Industrial air treatment processes use activated carbon to adsorb volatile organic compounds (VOCs) and air toxins in landfills, manufacturing facilities, and chemical processing plants. Activated carbon is one of the most commonly used and effective adsorbent materials to control VOCs or recover volatile solvents. A well-designed carbon adsorption unit can remove gas with over 95% efficiency. One study, published in the Journal of Hazardous Materials, found GAC achieved the maximum percentage of 90% removal of toluene. Toluene is a byproduct in the making of gasoline and other fuels. The study proves GAC can play a role in air cleaning filters.
It's common to see carbon adsorption systems arranged as bed units or moving bed units. In stationary systems, the polluted air enters from the top and passes through a bed of activated carbon. The air then exits through the bottom, leaving pollutants behind. In moving systems, the activated carbon moves down through channels as the polluted air passes through in a cross-current flow.
Areas of a manufacturing or processing facilities that may need to control hazardous emissions or odors include:
- Oil-water separators
- Process vents
- Drainage and collection manholes
- Vapor recovery units
- Vacuum filter exhausts
Activated carbon helps industries exceed strict air quality regulations set by the Clean Air Act (CAA). Under the CAA, factories and chemical plants must install pollution control equipment and meet emission limits. Cement manufacturing plants, for example, are the third-largest industrial source of air pollution and emit over 500,000 tons per year of sulfur dioxide, nitrogen oxides, and carbon monoxide. For cement plants and many other facilities across the globe, activated carbon offers a reliable solution for reducing air pollution.
GAC often removes residual disinfectants like chlorine from water supplies. It improves water taste and increases water safety. It also helps protect other treatment units from potential damage due to organic fouling or oxidation. The water treatment industry prefers activated carbon because it does not add anything hazardous to the water, and it is multifunctional.
Activated carbon can remove and destroy chlorine through a catalytic reduction reaction. A catalytic reduction reaction involves transferring electrons from the activated carbon surface to the chlorine. It then reduces chlorine to a non-oxidative chloride ion. It is a rapid process that takes place in the first few inches of the activated carbon bed. One pound of new activated carbon can hold one pound of chlorine.
Pharmaceutical plants and beverage manufacturers use activated carbon to remove chlorine for better taste and to offer purer products. Wastewater and power plants use the process of dechlorination to remove residual chlorine from effluent, which can harm aquatic life. Households can use faucet-mounted filters with carbon cartridges to remove residual chlorine and improve water taste.
Synthetic dyes used in textiles, plastics, printing, cosmetics, and rubber industries can be hazardous to the environment and need removal from wastewater. Experts estimate textile and manufacturing industries use over 10,000 commercially available dyes, about 15% of which get discharged into wastewater as effluents during the dyeing process. Out of the various methods used to remove color from wastewater, adsorption is the least expensive and the most effective.
Activated carbon is an effective material for removing color from wastewater through the process of adsorption. For example, one study found activated carbon successfully removed methylene blue and methyl orange dyes from wastewater. To remove colors and other pollutants, water treatment facilities dose PAC directly into the stream or holding tank and filter it out later. Businesses might choose GAC instead because it is recyclable, unlike PAC, and may be a more economical option.
Activated carbon can also remove color from water during the water treatment process.
Activated carbon, mainly in GAC form, reduces air pollutants to tiny concentrations. It has a wide range of applications in gas and exhaust air treatment in many different industries. Gas processing plants and manufacturers use activated carbon to remove impurities and catch mercury compounds that could damage processing equipment. Gas purification is the start of the process to produce fuel for consumers, to further process and sell impurities, or to reduce air pollution. Raw natural gas contains carbon dioxide, hydrogen sulfide, nitrogen, water, and other impurities that need removal before it can meet customer requirements. Many gas purification systems use activated carbon to remove impurities, especially hydrogen sulfide, from natural gas.
Activated carbon has several other uses to purify gas beyond processing natural gas. For example, it serves the following purposes:
- To remove hydrogen sulfide from biogas stream in landfills or wastewater treatment plants
- To remove trace amounts of lubrication oil from air streams in compressors
- To control carbon dioxide and ethylene in scrubber systems
- To remove pollutants in air conditioning, ventilation, and exhaust systems
Industrial gas filtration systems often use several vertical beds of activated carbon several inches thick to ensure adsorption as the effluent gas passes through.
Activated carbon removes organic materials from public water supplies and wastewater. Organic material comes from decaying plant life that becomes more water-soluble over time. It exists as organic acids. There can be almost endless amounts of organic acids in water, but activated carbon and its powerful adsorptive qualities make a reliable choice for removing organic materials. Activated carbon adsorbs organic molecules because the forces between the carbon and contaminants are stronger than the forces keeping the material dissolved in the water. However, the activated carbon must be close to the organic material. One factor that increases accessibility to the pores and improves adsorption includes using a carbon filter with a bed depth of three feet.
According to a study published in Water Science and Technology, researchers tested GAC as part of pretreatment technology for wastewater to see its effectiveness at removing organic materials and turbidity. The GAC tested reached a minimum of 80% turbidity removal.
Activated carbon is an essential tool in the gold mining industry. With the help of cyanide, activated carbon extracts gold. Gold gets broken down with a cyanide solution, and the ions then get exposed to GAC absorbers. The GAC pores concentrate the gold complex. Once the carbon absorber has become loaded with gold ions, it gets stripped of the gold.
The gold industry uses activated carbon made from the hard shell of coconuts, due to its exceptional adsorption properties and inherent durability. Today, the gold mining industry uses activated carbon mostly in carbon-in-pulp and carbon-in-leach methods. These techniques allow the industry to maximize extraction rates from ores and reduce processing and operating costs. They can reuse the absorbent in the extraction process, making it the standard for gold mining operations around the world.
Various industries, such as petrochemical, synthetic fibers, paint, printing, rubber, adhesives, and coating manufacturers, use carbon materials to recover and reuse solvents. Activated carbon is the main method for recovering solvents from air streams. The recovery process involves passing solvent vapors through an absorber with activated carbon. The activated carbon layers adsorb the vapor until desorption recovers the solvent. Common solvents recovered with activated carbon include benzene, ethanol, acetone, and xylene — just to name a few.
Activated carbon is one of the most cost-effective methods for controlling VOC emissions because it allows for reuse of VOCs. It is a practical process for any industry that uses large quantities of valuable solvents. Overall, solvent recovery helps protect the environment while offering economic benefits for various industries.
Activated carbon commonly removes taste and odor compounds during the water treatment process. Water treatment plants use PAC full-time or as needed to control taste and odor. They add PAC using either dry feed equipment or by mixing PAC with water to create a slurry and use a metering pump. Facilities typically use dry feed systems for smaller doses or where PAC doesn't often come into the process. Slurry systems are common when PAC is involved, and facilities need high doses. Usually, PAC gets added early in the treatment process and eventually removed. This method generates a sludge containing contaminants, and it requires safe disposal. Although it's possible to reuse GAC, PAC is a better option for taste and odor removal because it allows for timely and optimized dosage.
CONTACT BRENNTAG NORTH AMERICA FOR YOUR ACTIVATED CARBON NEEDS
For hundreds of years, activated carbon has been a cost-effective solution to water and gas purification. Because of activated carbon, businesses can comply with environmental laws and serve customers quality products. From gas purification to gold mining, activated carbon is a critical component for industries around the world.
If you need a reliable source for high-quality activated carbon, we can help. Brenntag North America is a top specialty and chemical distributor, with 190 distribution locations and over 100 years of experience. We thrive on helping our clients succeed, whether they operate a manufacturing facility or just started a cosmetics business. To learn more about the benefits and applications of activated carbon, or to order a supply of activated carbon to meet your business requirements, contact us today!
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