FACTORS AFFECTING THE PREPARATION OF ACTIVATED CARBONS FROM COCONUT SHELL CATALYZED BY POTASSIUM

A series of activated carbons was prepared from coconut shell impregnated with potassium solutions of different nature, concentration, and pH, using a CO2 flow as activating gas at 800-degrees-C. All the potassium compounds studied except KCl were effective catalysts for the activation with CO2. Potassium carbonate was found to favor carbonization and to produce gasification even in the absence of CO2 flow. Contrary to the carbonate, potassium phosphate was found, on one hand, to protect the product from excessive burn-off that leads to surface area decrease and, on the other, to promote mesoporosity. A direct correlation was found between pH of the phosphate solution and surface area, indicating an inhibition effect on gasification at low pH. Infrared spectra suggested the possible formation of linear (at high pH) and cyclic (at low pH) polyphosphates as precursor species for the protection and inhibition effects observed.