Adlai shell (Coix lacryma-jobi L.) adsorbents (ASA) were used to remove copper ions from aqueous solutions under batch conditions. The effect of physical and chemical modification of ASA on Cu(II) removal was evaluated. Results showed that the high coefficients of determination for the pseudo-second order (R-2 > 0.9999) and for the intraparticle diffusion (R-2 > 0.9843) equations indicate that the rate-determining step is a combination of pore diffusion and chemisorption at low Cu(II) concentration and boundary layer, pore diffusion and chemisorption at high Cu(II) concentration. At 298 K and 100 mg L-1 Cu(II), the computed q(e) and k(2) values were 17.2 mg g(-1) and 0.012 g mg(-1) min(-1), respectively. The Freundlich model (R-2 > 0.9636) adequately describes the experimental data indicating heterogeneous adsorption. Overall, the results of the study demonstrate the potential of adlai shell adsorbents for the removal of heavy metals from aqueous solutions. (C) 2015 Elsevier Ltd. All rights reserved.
