Whether you’re out buying a RO filter, a pitcher filter, or even just a shower filter- chances are it’ll include an activated carbon filtration stage. Activated carbon is everywhere these days- widely used in applications in the food, energy and water sectors, to name a few.
In this post I’m going to expand on what activated carbon is, how it’s made and why, specifically, coconut activated carbon is better than the rest.
What is Activated Carbon?
Activated carbon is a carbon based filtration medium with a porous atomic structure. This porosity is why it is called ‘activated’ carbon. Usually made from materials like peat, wood, coal, coconut shells, etc, activated carbon is widely used in water filters for removing organic contaminants, improving taste and removing odors.
How Is Activated Carbon Made?
- Chemical Activation
- Steam Activation
Essentially, the only thing you need to know here is that different activated carbon materials need different processes for activation. For instance, coconut is usually activated through steam, and not chemically. Peat- through chemicals only.
Unless you’re interested in exactly how the process works, you can skip ahead to the next section.
Our carbon based material- say peat, is dipped into a special solution, such as phosphoric acid and left for some time for the activation process, i.e: for pores to open up in the cellular structure. As you’ll learn next, these pores are crucial to it’s filtration capacity.
In a nutshell, this process takes place in two steps. Firstly, the raw material- usually coconut shells or coal- is heated upto 700 degrees Celsius in an inert atmosphere to give un-activated carbon.
Next, this carbonized product is activated with steam at 900-100 degrees Celsius- which basically means that steam is used to chisel out a porous internal structure in the carbonized structure.
How does Activated Carbon Remove Contaminants?
According to Dr. Mukherjee, activated carbon is essentially, an adsorbent media, i.e: contaminants stick to it’s porous surface. It’s internal surface area is huge due to it’s porous structure, which means that it can adsorb a lot of contaminants. In fact, 3 grams of activated carbon have a surface area equivalent to a football field!
Adsorption can occur due to:
- Natural affinity of contaminant to carbon
- Hydrophobic or water-repelling nature of contaminant- such as a lot of organic contaminants, VOCs
What Contaminants does Activated Carbon Remove?
Mainly, activated carbon is great at removing chlorine and it’s byproducts formed in water. The contaminants removed by Activated carbon are:
- Volatile Organic Compounds(VOCs)
- Pesticides and herbicides
- Improves taste
- Removes odors
RELATED: Read more about chlorine and it’s other byproducts in water as well as how to remove them here
What Activated Carbon Cannot Filter Out:
- Dissolved salts
- Heavy metals
- Some bacteria
What is Coconut Activated Carbon?
As the name suggests, it is activated carbon made from coconut shells.
- Is the least dusty, i.e: is more compacted which makes it more efficient than other activated carbons at adsorbing contaminants
- Has a harder structure than other activated carbons which makes it well suited for water filters
- Works at higher temperatures than normal activated carbon filters- which only work for cold water
Additionally, while activated carbon isn’t known for removing heavy metals- This study in Thailand found Coconut shell activated carbon a better bet than simple activated carbon for removing chromium from waste water due to it’s simple structure, efficacy in removing chromium as well as cost-effectiveness
- May become breeding ground for bacteria and fungus as the contaminants get built up inside the ‘sponge like’ filter
- May get clogged quickly if the contaminant concentration is too much- in fact, a lot of consumers in areas of really bad water quality complain of this.
Due to these drawbacks, you’ll find that activated carbon is never used as a single stage filter, rather it is almost always used as a post- filter, mainly to improve taste and chlorine and other organic compounds.
Granular Vs Block Activated Carbon
We know that the best type of activated carbon is coconut shell, but what is the best structure for it?
Structurally, there are two main physical types of activated carbon:
- Granular: Consists of loose granules of activated carbon
- Block: Consists of a block of compressed activated carbon
Granular activated carbon(GAC) has a better life than block carbon, and it can be reactivated as well. However, since it is basically a lot of loose carbon granules together, it isn’t as effective at filtration as block carbon, which consists of even finer carbon particles tightly jammed together.
Also, GAC filters are subject to channeling, i.e: water moves the loose carbons around and forms channels or small paths inside. This reduces the flow rate as well as filtration efficacy.
Thirdly, carbon block filters have a higher surface area than GAC filters, which means that water is in contact with the block filters for a longer time, which in turn means that more contaminants are adsorbed by them than by GAC filters.
Finally, as carbon block filters are small and more compact, they are more suited towards water filtration applications that GACs. Overall, you’ll find that most of the consumer products with activated carbon are coconut based block carbon.
So now you know why a lot of water filters today include activated carbon. If you haven’t noticed this before, do remember to check when you’re buying a new water filter or shower filter. Having coconut activated carbon gives an added layer of protection as well as improves the aesthetics of water.
Before I leave you, a few final recommendation of some popular water filters in the market that use coconut activated carbon:
- Brita-water filter pitcher
- PUR- water filter pitcher
- Aquasana- water filter pitcher and shower filter
Hope you enjoyed the post- questions? Jump into the comments below and I’ll revert ASAP!