Four different kinds of peels as adsorbents for the removal of Cd (II) from aqueous solution: Kinetics, isotherm and mechanism

In this paper, the four agricultural wastes of litchi peel (LP), orange peel (OP), pomegranate peel (PP) and banana peel (BP) were used as the adsorption material, their adsorption properties on Cd (II) were studied. The materials were characterized by SEM, FT-IR, Zeta and BET. Structural characterization indicated that the peels can be used as adsorption material containing a variety of functional groups, rough and porous surface. The maximum adsorption capacities were up to 230.5, 170.3, 132.5, 98.4 mg/g for LP, OP, PP and BP respectively. The adsorption ability of the four peels for Cd (II) was: LP>OP>PP>BP. The adsorption isotherms of the four peels were best described by the Langmuir model, and their adsorption kinetics followed the pseudo second-order kinetic equation. After 10 cycles of adsorption-desorption experiments, there was no significant change in the adsorption capacity. These findings suggest that the agricultural wastes could be potentially applied to the efficient removal of heavy metal ions from waste water. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.