The unique properties of activated carbon have allowed it to find niche application in many different fields of use. Its stability and potentially very high surface area are the main characteristics, but also the fact that particle size, surface chemistry and other properties can be readily tailored broadens the use of the material.
Gold extraction circuit
Mining
The activated carbon is used to concentrate the gold cyanide complex resulting from treatment of the ground ore in cyanide solution. The complex is adsorbed onto the carbon in agitation tanks, and then the gold recovered from the activated carbon by contact with a heated highly caustic solution. The gold is then finally extracted as the solution is subjected to an electro-winning process and the gold thereby deposited on electrodes. Since the carbon is highly agitated during the process, a hard, attrition resistant carbon is required to prevent losses from the circuit and to allow it to be thermally regenerated for repeated use.
Thermal and acoustic applications
The short range forces acting between gas molecules and the carbon surface, across a large surface area, endow activated carbon with some interesting properties which can be used for thermal insulation and also for altering the acoustic properties in void spaces such as Hi Fi speakers. The acoustic properties, for example, also allow carbon to be used in bass speakers particularly in order to confer the desirable properties of a much larger closed speaker volume.
The future of city transport
Electronic Double Layer Capacitors (EDLC)
One method of storing electrical energy has long been the capacitor, which was, however, somewhat limited. The latest "supercapacitors" again use the surface properties of activated carbon in order to allow the development of high surface area carbon electrodes. These carbon electrodes allow for extremely high electron densities across the electrode surface and thereby give these devices energy densities around 2 orders of magnitude higher than the conventional capacitor.
EDLC devices are often used in conjunction with new technology batteries in electric vehicles, where the battery holds more energy, but can only deliver it slowly, whereas the supercapacitor can deliver a fast burst of energy either to actuate something or provide acceleration.
Gas storage and delivery
Activated carbon can be used to store a variety of volatile gases under pressure. One application for this is in the area of Adsorbed Natural Gas (ANG), where natural gas can be stored on carbon at pressures typically around 35 bar. The advantage is that much more gas can be stored in a fixed volume than with a simple gas cylinder. Another important application for gas storage is for CO2 in the carbonated drinks industry.