If I cannot use homemade charcoal as water purifier, what kind of charcoal can I use?

Question:

Answers:
You need special 'activated' charcoal (these days it's often called 'activated carbon').

Activated charcoal has a huge amount of surface area. 1 gram of it has 500 square meters of surface area! It filters by 'adhesion', meaning the stuff you want to filter out sticks to the surface of the charcoal, so more surface is better.