Artur Braun , the activated carbon produced from this method has lower surface area compared to the inert gas method, right? I read some article before and they indicate that using air flow produce less surface area. Is that possible that i have high surface area of AC same as inert gas method by using the air flow method?

We soaked the charcoal powder in lemon juice for 24 hours. (Lemon juice as an acid plays a major role in activating carbon.) Then, cook the mixture for 4 hours at 400 degrees Celsius in the absence of oxygen to remove all moisture. The resulting dry powder was reasonably activated carbon and of course inexpensive.

Nice discussion