Characteristics of activated carbon from peanut hulls in relation to conditions of preparation

摘要

Powdered dried peanut hulls were treated by one-step procedures to get activated carbon using chemical activation by H_3PO_4, ZnCl_2, KOH and thermal activation by steam pyrolysis. Products were characterized by adsorption of N_2 at 77 K and methylene blue (MB) from aqueous solution. Simple carbonization at 700-900℃ yields low adsorbing microporous carbons. Steam pyrolysis at 600℃ generates porosity in the mesopore range. KOH activation results in carbons of low surface area similar to steam pyrolysis, but with much developed mesoporosity, whereas ZnCl_2 activation yields a moderate adsorbing carbon, essentially microporous. Treatment with H_2PO_4 at increasing impregnation ratios creates abundant microporosity with extended surface area attaining a maximum at a ratio of 1.0. Considerable loss in porosity accompanies additional activating acid indicating the governing action of the amount of activant. A 50% diluted H_3PO_4 acid results in a carbon with considerable reduction in the internal porosity. Highest removal capacity of MB appears with H_3PO_4-activated carbons, whereas KOH-activated carbons show the weakest uptake for the dye.