Tailored activated carbons prepared by phosphoric activation of apricot, date and loquat stones and their mixtures; relation between the pore size and the composition in biopolymer

Activated carbons of various physico-chemical characteristics were prepared from singly apricot, loquat or date stones, and from binary mixtures of them (50/50 mass %) by phosphoric acid activation. The content in each of the three biopolymers was quantified by chemical and thermogravimetric analyses. The surface chemistry of the activated carbons was characterized by elemental analysis, Boehm titrations, point of zero charge measurements and infrared spectroscopy, and their porous texture by adsorption of N2 at 77 K and of CO2 at 273 K. In the studied conditions of impregnation, precursors bearing high hemicellulose contents, such as loquat stones, have afforded highly mesoporous activated carbons, whereas activated carbons stemming from precursors richer in lignin and cellulose (i.e. apricot and date stones) have been found mainly microporous. The adsorption properties of methylene blue on the prepared activated carbons have been compared and tentatively correlated to their porosity and surface chemistry characteristics.