As
mentioned above, activated carbon is made from varieties of raw
materials. Therefore different raw materials inevitably result
in different properties of activated carbon.
In
general, activated carbon made from coal often uses heated steam
and carbon dioxide as activation agent. Coal based carbon is often
granulated, and its pore distribution is mostly occupied by micropores
which makes the carbon more suitable to adsorb the contaminants
whose molecule size is comparably smaller than others. The adsorption
properties of coal based carbon is often indicated by Methylene
blue adsorption value and Iodine value.
Activated
carbon made from sawdust is often produced by chemical activation
means, and is often powdered. Its pore distribution can be adjusted
flexibly by controlling the concentration of activation agents.
As a result, its pore distribution can be designed to be suitable
to adsorb contaminants with small molecule size, as well as contaminants
with big molecule size.
For
activated carbon made from nut shells, it often uses heated steam
and carbon dioxide as activation agent which is same as coal based
carbon activated with, and is often granulated too. Thanks to
its special material quality, its pore distribution is between
the above-mentioned two types of carbon which makes it suitable
to be used in more areas. The only defect is its high costs. The
sources of nut shells, especially coconut shells, are very limited
in domestic.
