Activated Carbons Developed from a Rapidly Renewable Biosource for Removal of Cadmium(II) and Nickel(II) Ions from Dilute Aqueous Solutions

Abstract

Canes from Arundo donax, a rapid-growing plant, were converted to activated carbons by phosphoric acid activation under four different activation atmospheres, to develop carbons with substantial capability to adsorb Cd(II) and Ni(II) ions from dilute aqueous solutions. The carbons showed surface areas and total pore volumes of around 1100 m2/g and 1 cm3/g, respectively. The content of carbons' polar or acidic surface oxygen functional groups, with their development depending on the atmosphere used, influenced predominantly metal adsorption. Carbons derived under flowing air, possessing the largest total content of these groups (3.3 mequiv/g), showed the best adsorption effectiveness (>90%) for both ions, even superior to that determined for a commercial sample used as a reference. A pseudo-second-order rate model properly described adsorption kinetic data obtained for this sample. Equilibrium isotherms using the same carbon were also determined and modeled by the Langmuir isotherm. The influence of the solutions' pH on metal uptake, adsorption competitive effects between Cd(II) and Ni(II) ions, and desorption from the selected metal-loaded carbon for recovery purposes were additionally investigated.