How to Make Activated Charcoal

How to Make Activated Charcoal
Activated charcoal can be made at home by chemical activation process. The requirements for making it are coconut shells, calcium chloride or zinc chloride solution, burning sink, oven and blender.
Activated charcoal is a form of carbon with an increased surface area for adsorption. It is also referred to as activated carbon, active charcoal or at times, activated coal. In order to produce activated charcoal, a carbon source is treated under certain conditions to increase its surface area and/or number of pores. On an average, the estimated surface area for a gram of activated charcoal is about 500 square meter.

The adsorbing characteristic of activated charcoal is used for many purposes. When a compound passes near this charcoal, the latter adsorbs the substance by chemical attraction. It is considered as the most effective poison antidote till date. If administered early, activated charcoal can adsorb about 60 - 70 percent of the ingested poison. Due to its various benefits and multiple applications, it is produced on a large scale. Commercially, it is available in the form of dry powder, liquids and tablets.

Raw Materials that can be Used

Activated carbon can be made from a wide range of carbon-rich materials like wood, coal, bones, coconut shells, nut shells, peat and agricultural residues. The nature of the pores and the adsorption capacity of the activated charcoal depends on the type of raw materials used for its production. It also depends on the method used for its activation. Black bone char is one with the least adsorption capacity whereas grey-brownish bone char is the best. The white char presents a low capacity of removing fluoride. These bone charcoals usually have lower surface areas than activated carbons. However, they have high adsorption for certain metals like copper, zinc and cadmium.

The nut shells and coconut shells produce activated charcoal with the best adsorption capacity and largest surface area. The procedure is the same even if you use hardwood, however using coconut shells will create a superior quality activated charcoal.

Steps to Make Activated Charcoal at Home

Activated charcoal can be made at home by chemical activation procedure, provided you have the required materials and equipment. Though any organic material can be used as a precursor or raw material for producing activated charcoal, you should select a nontoxic carbon source with absorbent properties. Let's discuss in brief how to make activated charcoal by using coconut shells as the raw material.

First of all, keep all the required materials ready for making activated charcoal; you need:
  • Coconut shells (without meat)
  • Burning sink, drum or an elongated iron container to burn the shells.
  • Oven
  • 25 percent concentrated solution of calcium chloride (CaCl2) or zinc chloride (ZnCl2) available in brewing supply shops or drug stores. To make this solution, dissolve 250 g CaCl2 in 1000 ml of water and increase the proportion in the same ratio as per your requirement.
  • Sterilized water
  • Plastic pail
  • Draining tray
  • Zipper bags
  • Blender
Before starting the procedure, you can strip off coconut shells, wash thoroughly with clean water and allow them to dry completely. If drying is not done properly, they will be difficult to burn.

Hoping that the coconut shells are free of moisture, add them in the burning sink (or drum). Measure the temperature and make sure it is adjusted to about 600 - 900 degrees Fahrenheit. Maintain the recommended temperature range and burn continuously for about 4 ½ hours or until the coconut shells turn into ash. For safe handling, you can leave the ash until it cools down.

After the ash has cooled down, take it out carefully from the sink and transfer into a clean plastic pail. Then, pour the 25 percent concentrated solution of calcium chloride or zinc chloride into the plastic pail.

The amount of calcium chloride or zinc chloride solution should be such that the ash is soaked completely into the solution. Cover the pail with a lid and leave for 20 - 24 hours. During this process, the chemicals are impregnated into the ash and it will transform the ash into activated charcoal. This is called as chemical activation which makes it highly porous and adsorbent. The next step is removing the charcoal from the chemical solution and transferring it into a draining tray. Allow the treated charcoal to drain for about 1 hour.

For removal of trace chemicals from the charcoal, you can wash and rinse it repeatedly with sterilized water. Thorough washing is essential in order to get rid of the chemical solution, which otherwise will remain in the charcoal. It is one of the most common problems in the making of activated charcoal by chemical activation procedure. After washing, keep the charcoal in the tray for draining water. Following this, transfer charcoal into an oven, setting the temperature to about 215 - 230 degrees Fahrenheit and bake for about 3 hours.

After baking for the stipulated time, remove the charcoal from the oven and crush it with the help of a blender. You can also grind the charcoal into powder form by using a hammer. For future use, store the powdered charcoal into zipper bags or airtight containers.

Though activated charcoal can be made at home if one has the required materials and equipment, it is readily available in many drugstores as well.