Activated charcoal

Activated charcoal, also called activated carbon, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that increase the surface area available for adsorption.

Uses

Activated carbon is used in methane and hydrogen storage; air, gold and water purification; capacitive deionization, supercapacitive swing adsorption, solvent recovery, decaffeination, metal extraction, medicine, sewage treatment, air filters in respirators, filters in compressed air, production of hydrogen chloride, edible electronics, and many other applications.

Industrial

One major industrial application involves use of activated carbon in metal finishing for purification of electroplating solutions. For example, it is the 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, among others. Organic additives generate unwanted breakdown products in solution. Their excessive build up can adversely affect plating quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level.

Medical

Activated charcoal for medical use

Activated carbon is used to treat poisonings and overdoses following oral ingestion. Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence. However, activated charcoal shows no effect on intestinal gas and diarrhea, and is, ordinarily, medically ineffective if poisoning resulted from ingestion of corrosive agents, boric acid, petroleum products, and is particularly ineffective against poisonings of strong acids or bases, cyanide, iron, lithium, arsenic, methanol, ethanol or ethylene glycol. Activated carbon will not prevent these chemicals from being absorbed into the human body. Incorrect application (e.g. into the lungs) results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not initiated.

Environmental

Carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as:

• Spill cleanup
• Groundwater remediation
• Drinking water filtration
• Air purification
• Volatile organic compounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes
• Volatile organic compounds recovery (solvent recovery systems, SRU) from flexible packaging, converting, coating, and other processes.

Activated carbon is also used for the measurement of radon concentration in air.

Agricultural

Activated carbon is an allowed substance used by organic farmers in both livestock production and wine making. In livestock production it is used as a pesticide, animal feed additive, processing aid, nonagricultural ingredient and disinfectant. In organic winemaking, activated carbon is allowed for use as a processing agent to adsorb brown color pigments from white grape concentrates.It is sometimes used as biochar.

Fuel storage

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 gases. 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 pressure tanks in vehicles.

Gas purification

Filters with activated carbon are usually used in compressed air and gas purification to remove oil vapors, odor, 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 carbon filters are used to retain radioactive gases within the air vacuumed from a nuclear boiling water reactor turbine condenser. The large charcoal beds adsorb these gases and retain them while they rapidly decay to non-radioactive solid species. The solids are trapped in the charcoal particles, while the filtered air passes through.

Chemical purification

Activated carbon is commonly used on the laboratory scale to purify solutions of organic molecules containing unwanted colored organic impurities. Filtration over activated carbon is used in large scale fine chemical and pharmaceutical processes for the same purpose. The carbon is either mixed with the solution then filtered off or immobilized in a filter.

Mercury scrubbing

Activated carbon, often infused with sulfur or iodine, is widely used to trap mercury emissions from coal-fired power stations, medical incinerators, and from natural gas at the wellhead. However, despite its effectiveness, activated carbon is expensive to use. Since it is often not recycled, the mercury-laden activated carbon presents a disposal dilemma.

Crafting instructions

Activated charcoal can be activated in one of two common methods of production.

Materials needed

Either

• Charcoal
• Sieve
• Furnace
• A source of steam or pure oxygen

or

• Charcoal
• Acid or Strong base

Physical activation:

1. Crush the Charcoal
2. Screen the pieces such that they are small enough that a gas can penetrate the entire piece, but not so small that their packing density prevents gasses from reaching each piece (as may be the case with dust). When finished, all pieces should be roughly the same size.
3. Heat the charcoal between 600-1200°C in the presence of steam or pure oxygen. This can be done by sending the gas through to one side of a container of and exhausting the gas through the other side. Practically, an intake pipe can be fed into a mostly-sealed furnace, in through an open bottom of a container of charcoal and up to the top of the charcoal. Exhaust gasses are free to escape through the bottom of the charcoal and through an exhaust port of the furnace.
4. As this process is endothermic, it is recommended the process is stopped, allowed to heat back up and restarted a number of times.
5. remove the charcoal from the furnace and let cool.

Chemical activation

1. Crush the Charcoal
2. Mix with an acid or strong base. Typical solutions include lemon juice 25% bleach 25% calcium chloride 25%, potassium hydroxide 5%, sodium hydroxide 5%, potassium carbonate 5%, and zinc chloride 25%. The charcoal should be wet, but not saturated.
3. Let sit for 24 hours.
4. Boil for 3 hours. This is the activation step.
5. Once cooled, rinse the charcoal to remove any leftover reagents and let dry.

Dependencies

• Carbon
  • Activated charcoal
    • Water

See also

• Charcoal
• Coal

References

This article uses material from the Wikipedia article Activated_carbon, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License (view authors).