Activated Charcoal is a Proven Water Filtering Agent
A charcoal filter is a common part of most gravity fed and many force-fed water filters. Charcoal is the product of the destructive distillation of wood. This process yields wood alcohol, acetic acid, several burnable gases, and a few other products. The solid residue that results from this process is what we know as charcoal.
Charcoal is a black, brittle solid that is very porous. It is also odorless and tasteless. Though denser than water, charcoal can float! It does this because it is able to adsorb solids and gases so well. When charcoal has the opportunity to adsorb enough gases, they make it float.
Activated charcoal, coal, or carbon is charcoal that has been processed to make it extra porous. Because of this, just one gram of activated carbon has a surface area of approximately 500 m2 but this could be as much as 1500 m2! Considering that it takes 454 grams to make a pound and that a tennis court has 260 m2, it is easy to see just how porous it is! This increased surface area means that more impurities will touch the charcoal as they pass by.
The secret of charcoal’s filtering ability is in the fact that it is so good at adsorbing (not absorbing). “Adsorption is the concentration of a gas, liquid, or solid on the surface of a liquid or solid with which it is in contact.” Just one cubic centimeter of charcoal is able to adsorb 90 cc of ammonia gas though it adsorbs other substances far better.
Pollutants that are dissolved in the water as it passes through the filter come in contact with the activated charcoal. These substances are actually attracted to the charcoal by van der Waals forces. Wiki explains these forces this way. “In physical chemistry, the van der Waals force is the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral molecules.”
Putting it simply, molecular forces bind some compounds to the charcoal. Not all substances are equally attracted to the activated carbon. Substances such as alcohols, glycols, ammonia, strong acids and bases, metals and most inorganics, such as boric acid lithium, sodium, iron, arsenic, lead, and fluorine are not filtered as well.
This is good in some ways. The minerals in water are needed in the body; drinking distilled water all the time would deplete the body of needed substances. So it is good that they are not filtered out. Also, some do not want fluorine removed from the water because of claims that it aids in dental health. However, others of these chemicals are unwanted and the filters must have other substances in them to remove these.
In conclusion, water and contaminants pass through the activated charcoal filter and, because of the filter?s porosity, the substances will likely come in contact with the carbon. The van der Waals forces will cause the substances to be attracted to the charcoal where they will remain until the filter is washed or replaced. For the contaminant, it is dead end road. For the person drinking the water, it is refreshing and healthy.
Berkey Filters are the best line of activated charcoal filter we are aware of. Check out the Fluoride Filter or another model. One amazing feature is that each set of filters they ship with can be re-cleaned to purify up to 6,000 gallons of drinking water.