Physicochemical and adsorptive properties of activated carbons from Arundo donax Linn utilizing different iron salts as activating agents

• AC-FeCl3 has the highest surface area and micropore volume.
• AC-FeC6H5O7 has the highest external surface area and total pore volume.
• AC-FeCl3 and AC-FeCl2 contained more acidic groups than AC-FeC6H5O7 and AC-FeC2O4.
• The adsorptive properties of the carbons toward CEX were studied.

Four kinds of iron salts, ferric chloride (FeCl3), ferrous chloride (FeCl2), ferric citrate (FeC6H5O7) and ferrous oxalate (FeC2O4) were employed as activating agents to prepare activated carbons (AC–FeCl3, AC-FeCl2, AC-FeC6H5O7 and AC-FeC2O4) from Arundo donax Linn (AL). The physicochemical properties of the activated carbons were investigated by N2 sorption/desorption isotherms, XRD, SEM, TEM, FTIR and Boehm's titration. The surface area and micropore volume of AC-FeCl3 and AC-FeCl2 were much higher than those of AC-FeC6H5O7 and AC-FeC2O4. Among the four carbons, AC-FeC6H5O7 displayed the highest external surface area and total pore volume. Boehm's titration results showed that AC-FeCl3 and AC-FeCl2 had more acidic oxygen functionalities than AC-FeC6H5O7 and AC-FeC2O4. Batched sorption studies were carried out to study adsorptive properties of the activated carbons toward cephalexin (CEX). The maximum CEX adsorption capacities of AC-FeCl3 (285.714 mg/g) and AC-FeCl2 (238.095 mg/g) were higher than those of AC-FeC6H5O7 (227.273 mg/g) and AC-FeC2O4 (113.636 mg/g), resulting from Lewis acid–base interaction, electrostatic interaction and hydrophobic interaction.