Blog post about activated carbon

What exactly is activated carbon

Activated carbon is a highly porous, dust-fine, sponge-like carbon, with an immense inner surface.
The inner surface and its porous structure for adsorption (i.e., adhesion to the surface) predestine the activated carbon to remove unwanted substances from vapors or liquids.

Activated carbon filters out heavy metals such as lead, zinc, copper, nickel or cadmium, etc.
Also, chlorine, pesticides, trihalomethanes, drug residues, hormones, odors, colors or flavors are removed. That is why it is not only used in waste water and drinking water treatment, but also in medicine, cosmetics, chemistry, and in ventilation and air conditioning technology.

How is activated carbon produced?

Activated carbon is made from several carbonaceous materials, such as peat, wood, bone, lignite, hard coal and coconut shell.
Firstly, the starting material is carbonized below 800 ° C. Subsequently, the material is exposed to a manufacturing process which produces an extremely large internal surface, the so-called "activation" (hence the name "activated carbon").

Incredibly large surface area of activated carbon
The inner surface of 1 g of base coal is only about 10 m2. After activation, 1 g of activated charcoal, e.g. made of coconut shell, have an inner surface of 1000 m2 or more.
For example, 4 to 5 grams of charcoal (one teaspoon), if you unfold them, can cover a whole football field.

Activation of the activated carbon

The activation takes place at temperatures of 700 - 1000 ° C using water vapor and carbon dioxide, sometimes with air. This activation converts some of the carbon into carbon dioxide, creating additional pores and increasing the surface area.

One distinguishes between chemical activation and gas activation. In chemical activation, a mixture of uncarburated starting material is treated with chemicals, mainly with dehydrating agents, such as zinc chloride or phosphoric acid, at temperatures of 500-900 ° C. In gas activation, charred materials such as charcoal, peat coke, coconut shell coke, coal or lignite are used as starting materials.

Types of activated carbon

There are three types of activated carbon: powder, granular, and extruded. In the case of the granular carbon, the particles have a size of about 1 mm, while in the case of powder
the size is about 0.1 mm.

In both cases the inner surface is the same size. In the case of the extruded activated carbon, the charred semifinished product is pulverized, activated and then mixed with an adhesive, and extruded or sintered as needed.
One difficulty with the extruded carbon is that water pressure must be exerted to allow the water to flow through the charcoal because the adhesive prevents the passage of the water.

                                                                    Coal / glued coal

It is immensely more efficient to use granular carbon, where gravity alone is enough to cause the flow.
So the water has the opportunity to develop naturally. Such an activated carbon is used in the water filters of Acala.

In addition, the size of the particles may influence the rate of adsorption, but not the amount adsorbed, since this depends only on the internal surface area. According to this finding, the granular activated carbon is considered to be more efficient for water treatment than the powder.

Structure of the atoms

Activation activates the charcoal to form an irregular disordered crystalline structure of carbon atoms.
This disordered structure has a large porosity where the substances to be filtered can be bound.
These pores are classified according to their sizes: macropores (> 50 nm *), mesopores (2-50 nm *), micropores (1-2 nm)
and minimal micropores (<1 nm *).
Micropores are suitable for smaller molecules. Coconut shell grain has a larger internal surface area
and a larger proportion of micropores.
* (1 nm (nanometer) is one millionth of a millimeter)

Retention of the activated carbon

The extent to which activated carbon adsorbs a substance depends on several factors, such as the size of the molecules, the solubility of the substance, its affinity for activated charcoal, and the pH of the water, which influences these variables.
Activated carbon is particularly suitable for the removal of organic matter, such as trihalomethanes, pesticides or hormones, because these substances have a greater affinity for activated carbon.

Can Activated Carbon Filter Out microplastics or nanoplastics?

Plastic particles can also be classified according to their size. They are commonly known as microplastics, but also get different names according to their size. Mesoplastic (500 mm - 5 mm *), microplastics (50 mm - 500 mm *) and nanoplastics of less than 50 mm * (some authors set the limit at 100 nm **). Although they are referred to as nanoplastics, their size is actually greater than 1 nm **

In order for nanoplastics to develop from microplastics, time is a decisive factor. It has been estimated that 320 years are needed, so that a 100 mm nanoplastic particle is formed from a 1 mm microplastic particle.

In addition, a group of scientists investigated the clumping of 30 nm ** polystyrene particles (a type of plastic) in seawater and found a rapid formation of 1000 nm ** aggregates within 16 minutes. Thus, it appears that even if nanoparticles are in the water, they tend to clump together to form particles of microplastics.

The question is: can activated carbon filter out microplastic? The answer is a very clear yes.
It should be clear that nanopores less than 2 nm in size ** adsorb the largest mesoplastics and microplastics. This is also the case with nanoplastics, only in extreme cases of nanoplastic particles with a size of less than 2 nm ** could these particles pass through the pores. Thus, the filtration of microplastic particles by activated carbon is guaranteed in almost all cases.
In addition, the plastic is not dissolved in water, so you can assume that it is hydrophobic and it feels better on the carbon than in the water.
Plastic is organic and therefore has an increased affinity for activated carbon.

Why is plastic organic?
Organic molecules are complex molecules made of carbon and other substances, in plastics we are dealing with polymers (chains). Depending on the type of plastic, plastic consists of carbon, hydrogen, oxygen, sulfur and nitrogen, while the organic refers to the carbon content in plastic.
* 1mm = (microns) is one-thousandth of a millimeter
** 1 nm (nanometers) is one millionth of a millimeter

Activated carbon unhealthy?

You should not worry about your water coming into contact with activated carbon. Activated carbon is a natural product, especially if it is made from coconut shell. You get the same activated charcoal from the family doctor when you have diarrhea.
Coal is even used to dye ice cream and other foods. Coal has many different uses, and also in cosmetics its excellent properties are used to the advantage of the skin.
This will ensure your health and thus protect the water and the environment.

Bread with activated carbon                                       Ice-cream dyed with charcoal

   Hamburger with mixed coal                                     Coal tablets against diarrhea

 Coal in cosmetics

The use of activated carbon in its present form has only a short history.
However, coal, mostly as charcoal, has been used since antiquity by the Egyptians, Indians, Greeks and Romans.
In Egypt, for example, it was used in the embalming of the deceased and in the sealing of ship hulls.
The ancient Greeks used charcoal as an antidote to food poisoning.
In India, it was used for drinking water treatment for the first time, as a Sanskrit text from around 200 BC. reported.
In the 15th century, in the time of Christopher Columbus, sailors discovered that drinking water stays fresh longer during the voyages, when the wooden containers were "carburized" inside.
The first scientific study on activated carbon was carried out by Karl Wilhelm Scheele, a Swedish chemist, at the end of the 18th century.
The first industrial application took place at the beginning of the 20th century.



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