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Activated Charcoal is a Proven Water Filtering Agent

December 26, 2009

Berkey Filter Comparison

Many force fed water filters and most gravity fed water filters use a charcoal filter. What is charcoal? It is the solid residue resulting from the process of the destructive distillation of wood. This process also yields acetic acid, several burnable gases, wood alcohol, and some other products.

Charcoal is an odorless and tasteless solid, porous, black, and brittle.  Charcoal is normally too dense to float in water, yet sometimes it does. How can this be? It is because charcoal has the remarkable ability to adsorb solids and gases. Charcoal does this so well that it can adsorb enough gases to 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.

Charcoal is used in filters because of its ability to adsorb. This is not absorption but adsorption. “Adsorption is the concentration of a gas, liquid, or solid on the surface of a liquid or solid with which it is in contact.” One cubic centimeter of charcoal has the ability to adsorb 90 cc of ammonia gas. Charcoal adsorbs other substances even 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.”

Though this is very technical, it can be summarized by saying molecular forces bind some compounds to the charcoal. Activated carbon does not bind all chemicals equally well. It does not do as well with ammonia, alcohols, strong acids and bases, glycols, metals and most inorganics, such as fluorine, lithium, iron, sodium, lead, arsenic, and boric acid.

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.

The best line of activated charcoal filter we are aware of is the Berkey Filter. Whether you choose their Big Berkey Water Filter or another model, each set of filters they ship with can be re-cleaned to purify up to 6,000 gallons of water.

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