Activated carbon is used in gas purification, gold purification, metal extraction, water purification, medicine, sewage treatment, air filters in gas masks and respirators, filters in compressed air and many other applications.
Recently Activated Carbon filters have gained popularity among recreational users of Cannabis, and other smoking herbs for their use in effectively filtering out "Tar" from the smoke. They are becoming quick competition for Vapourizers as they are only a fraction of the cost and achieve nearly the same thing.
One major industrial application involves use of activated carbon in the metal finishing field. It is very widely employed for purification of electroplating solutions. For example, it is a main purification technique for removing organic impurities from bright nickel plating solutions. A variety of organic chemicals are added to plating solutions for improving their deposit qualities and for enhancing properties like brightness, smoothness, ductility, etc. Due to passage of direct current and electrolytic reactions of anodic oxidation and cathodic reduction, organic additives generate unwanted break down products in solution. Their excessive build up can adversely affect the plating quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level.
Analytical chemistry applications
Activated carbon, in 50% w/w combination with celite, is used as stationary phase in low-pressure chromatographic separation of carbohydrates (mono-, di- trisacchardes) using ethanol solutions (5–50%) as mobile phase in analytical or preparative protocols.
Carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as:
Drinking water filtration
Volatile organic compounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes.
In 2007, West-Flanders University (in Belgium) began research in water treatment after festivals. A full scale activated carbon installation was built at the Dranouter music festival in 2008, with plans to utilize the technology to treat water at this festival for the next 20 years.
Activated charcoal is also used for the measurement of radon concentration in air.
Activated carbon is used to treat poisonings and overdoses following oral ingestion.
It is thought to bind to poison and prevent its absorption by the gastrointestinal tract. In cases of suspected poisoning, medical personnel administer activated charcoal on the scene or at a hospital's emergency department. Dosing is usually empirical at 1 gram/kg of body mass (for adolescents or adults, give 50–100 g), usually given only once, but depending on the drug taken, it may be given more than once. In rare situations activated charcoal is used in Intensive Care to filter out harmful drugs from the blood stream of poisoned patients. Activated charcoal has become the treatment of choice for many poisonings, and other decontamination methods such as ipecac-induced emesis or stomach pumping are now used rarely.
Activated charcoal for medical use.
While activated carbon is useful in acute poisoning, it has been shown to not be effective in long term accumulation of toxins, such as with the use of toxic herbicides.
Mechanisms of action:
Binding of the toxin to prevent stomach and intestinal absorption. Binding is reversible so a cathartic such as sorbitol may be added as well.
It interrupts the enterohepatic and enteroenteric circulation of some drugs/toxins and their metabolites
Incorrect application (e.g. into the lungs) results in pulmonary aspiration which can sometimes be fatal if immediate medical treatment is not initiated. The use of activated charcoal is contraindicated when the ingested substance is an acid, an alkali, or a petroleum product.
For pre-hospital (paramedic) use, it comes in plastic tubes or bottles, commonly 12.5 or 25 grams, pre-mixed with water. The trade names include InstaChar, SuperChar, Actidose, Charcodote, and Liqui-Char, but it is commonly called activated charcoal.
Ingestion of activated charcoal prior to consumption of alcoholic beverages appeared to reduce absorption of ethanol into the blood. 5 to 15 milligrams of charcoal per kilogram of body weight taken at the same time as 170 ml of pure ethanol (which equals to about 10 servings of an alcoholic beverage), over the course of one hour, seemed to reduce potential blood alcohol content. Yet other studies showed that this is not the case, and that ethanol blood concentrations were increased because of activated charcoal use.
Charcoal biscuits were sold in England starting in the early 19th century, originally as an antidote to flatulence and stomach trouble.
Tablets or capsules of activated charcoal are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence. There is some evidence of its effectiveness as a treatment for irritable bowel syndrome (IBS), and to prevent diarrhea in cancer patients who have received irinotecan. It can interfere with the absorption of some medications, and lead to unreliable readings in medical tests such as the guaiac card test. Activated charcoal is also used for bowel preparation by reducing intestinal gas content before abdominal radiography to visualize bile and pancreatic and renal stones. A type of charcoal biscuit has also been marketed as a pet care product.
Research is being done testing various activated carbons' ability to store natural gas and hydrogen gas. The porous material acts like a sponge for different types of gasses. The gas is attracted to the carbon material via Van der Waals forces. Some carbons have been able to achieve bonding energies of 5–10 kJ per mol. The gas may then be desorbed when subjected to higher temperatures and either combusted to do work or in the case of hydrogen gas extracted for use in a hydrogen fuel cell. Gas storage in activated carbons is an appealing gas storage method because the gas can be stored in a low pressure, low mass, low volume environment that would be much more feasible than bulky on board compression tanks in vehicles. The United States Department of Energy has specified certain goals to be achieved in the area of research and development of nano-porous carbon materials. As of yet all of the goals are yet to be satisfied but numerous institutions, including the Alliance for Collaborative Research in Alternative Fuel Technology program, are continuing to conduct work in this promising field.
Filters with activated carbon are usually used in compressed air and gas purification to remove oil vapors, odors, and other hydrocarbons from the air. The most common designs use a 1 stage or 2 stage filtration principle in which activated carbon is embedded inside the filter media. Activated charcoal is also used in spacesuit Primary Life Support Systems. Activated charcoal filters are used to retain radioactive gases from a nuclear boiling water reactor turbine condenser. The air vacuumed from the condenser contains traces of radioactive gases. The large charcoal beds adsorb these gases and retains them while they rapidly decay to non-radioactive solid species. The solids are trapped in the charcoal particles, while the filtered air passes through.
Activated carbon is commonly used to purify homemade non-dangerous chemicals such as sodium acetate.
Distilled alcoholic beverage purification
See also: Lincoln County Process
Activated carbon filters can be used to filter vodka and whiskey of organic impurities which can affect color, taste, and odor. Passing an organically impure vodka through an activated carbon filter at the proper flow rate will result in vodka with an identical alcohol content and significantly increased organic purity, as judged by odor and taste.
Activated carbon, often impregnated with iodine or sulfur, is widely used to trap mercury emissions from coal-fired power stations, medical incinerators, and from natural gas at the wellhead. This carbon is a specialty product costing more than US$4.00 per kg. However, it is often not recycled.
Disposal in the USA after absorbing mercury
The mercury laden activated carbon presents a disposal dilemma. If the activated carbon contains less than 260 ppm mercury, Federal regulations allow it to be stabilized (for example, trapped in concrete) for landfilling. However, waste containing greater than 260 ppm is considered to be in the high mercury subcategory and is banned from landfilling (Land-Ban Rule). It is this material which is now accumulating in warehouses and in deep abandoned mines at an estimated rate of 1000 tons per year.
The problem of disposal of mercury laden activated carbon is not unique to the U.S. In the Netherlands this mercury is largely recovered and the activated carbon is disposed by complete burning.
The regeneration of activated carbons involves restoring the adsorptive capacity of saturated activated carbon by desorbing adsorbed contaminants on the activated carbon surface.
The most common regeneration technique employed in industrial processes is thermal regeneration. The thermal regeneration process generally follows three steps:
Adsorbent drying at approximately 105 °C
High temperature desorption and decomposition (500–900°C) under an inert atmosphere
Residual organic gasification by an oxidising gas (steam or carbon dioxide) at elevated temperatures (800°C)
The heat treatment stage utilises the exothermic nature of adsorption and results in desorption, partial cracking and polymerization of the adsorbed organics. The final step aims to remove charred organic residue formed in the porous structure in the previous stage and re-expose the porous carbon structure regenerating its original surface characteristics. After treatment the adsorption column can be reused. Per adsorption-thermal regeneration cycle between 5–15 wt% of the carbon bed is burnt off resulting in a loss of adsorptive capacity. Thermal regeneration is a high energy process due to the high required temperatures making it both an energetically and commercially expensive process. Plants that rely on thermal regeneration of activated carbon have to be of a certain size before it is economically viable to have regeneration facilities onsite. As a result it is common for smaller waste treatment sites to ship their activated carbon cores to a specialised facility for regeneration, increasing the process' already significant carbon footprint.
Activated carbon used in consumer devices such as oil deep fryers or air and water filters can similarly be reactivated using commonly available heating appliances such as a baking oven, toaster oven, or simply a propane torch. The carbon is removed from any paper or plastic containers that could melt or ignite, and heated to vaporize and/or burn off contaminants.
Other regeneration techniques
Current concerns with the high energy/cost nature of thermal regeneration of activated carbon has encouraged research into alternative regeneration methods to reduce the environmental impact of such processes. Though several of the regeneration techniques cited have remained areas of purely academic research, some alternatives to thermal regeneration systems have been employed in industry. Current alternative regeneration methods are:
Chemical and solvent regeneration
Wet air oxidation