Tailoring of porous texture of hemp stem-based activated carbon produced by phosphoric acid activation in steam atmosphere

Abstract

A series of activated carbons (ACs) were produced by chemical activation of hemp stem with phosphoric acid in nitrogen and steam atmospheres. The potential of hemp-derived waste for the manufacture of porous carbons with a wide spectrum of porosity, ranging from microporous to mesoporous, has been demonstrated. The influence of the variables, such as the H3PO4/hemp stem impregnation ratio, the soaking time and the gaseous atmosphere, on the porosity development was studied. Depending on the processing conditions, the H3PO4 activation produces ACs with a wide range of textural parameters, reaching surface areas >2,500 m2/g, micropore pore volumes up to 0.89 cm3/g and mesopore volumes up to 1.80 cm3/g. The amount of H3PO4 used in the impregnation step affects the porous texture of the resultant ACs to a greater extent than the soaking time. At low and medium impregnation ratios, a steam atmosphere favors the formation of mesopores during H3PO4 activation.