How can activated charcoal be cleaned and reused?

Answer 1

Cleaning of Activated Carbon/Charcoal (AC) is actually quite complicated, and can be a bit 'hit and miss'.

For most applications it may be adequate to soak it for 48 hours in 9-10% hydrogen peroxide, stirring regularly, and replenishing the solution several times. Then bake in a hot oven for an hour or two. The peroxide is very reactive and helps break down protein, bacteria, and organic compounds, and the baking drives them off....

This could be adequate for most 'home uses' where the quality of the cleaning is not of high importance (for example: use in home water filters, fish tanks, or to purify distilled alcohol).

Care should be taken when using cleaned or re-charged AC. Without sophisticated testing equipment, measuring the efficiency of the re-charged AC is very difficult. 'Sniff' testing filtered fish tank water and or purified alcohol may be possible for an experienced fish or alcohol aficionados where the removed compounds would otherwise leave some residual odour.

More specifically, the regeneration of AC depends on what the carbon has been removing, and how important it is that it continues to function 100% perfectly. Without a complete understanding of what has been removed by the AC, cleaning is likely to be less than complete. Successive cleanings may reduce the efficiency of the filtration and the AC may cease to adsorb the very materials you are trying to filter.

In many cases, it may be ok to flush it with distilled, de-ionised water, 'bake' the activated carbon in an oven or treat it with super heated steam. Both of these methods can be accomplished at home if you have an oven or a pressure cooker.

Other reactive chemicals are sometimes used to remove the adsorbed substances - resting in a strong solution of hydrogen peroxide, followed by baking may assist with removing more organic contaminants as oxygen liberated from the hydrogen peroxide is very reactive.

The Organic Materials Review Institute (OMRI) has produced a paper on Activated Carbon processing which includes the following:

Carbon can be reused if the adsorbed substances are removed. This process is known as 'regeneration.' Simply heating the spent carbon at a given temperature for an adequate length of time can regenerate activated carbon to the point where it can be reused for tertiary wastewater treatment (thermal regeneration) (Mine Safety Appliance Corp., 1970). Thermal regeneration inevitably results in the loss of carbon (Battelle, 1970). Also, thermal methods may not be the most efficient, inexpensive, or reliable method, so a number of solvents, acids, and alkalis may be employed to remove the adsorbed substances. These include such things as carbon tetrachloride, hydrochloric acid, hydrogen peroxide, potassium hydroxide, sodium hydroxide (Mine Safety Research Corp., 1970). Optimization of the regeneration process depends on the substances adsorbed as well as the structure of the activated carbon

The paper on Activated Charcoal processing linked here:

http:/wwwzperiodzomrizperiodzorg/AC_processing.pdf

Note that a specialist understanding of the process is required if using the cited methods. The chemicals discussed require special handling and treatment to ensure the activated carbon is not left contaminated by acids, alkalis or other chemicals used in the cleaning process.