Adsorption behavior of Cd ions onto pentaethylenehexamine modified activated carbon

In order to develop an effective adsorbent for Cd ions removal, activated carbon (AC) was prepared with rice husk and modified with pentaethylenehexamine (PEHA). The batch adsorption were studied for AC and AC-PEHA to determine the effect of contact time, initial Cd ions concentration and solution pH on the Cd ions ions uptake. The effect of HCl concentration on desorption efficiency for Cd ions was discussed as well. SEM, FTIR and BET surface area analysis were used to characterize the structure, morphology and properties of AC and AC-PEHA. The results show that the adsorption equilibrium are achieved for both AC and AC-PEHA at react time 60 min, and adsorption kinetics are well described by the pseudo-second-order model. Comparing with AC, The adsorption capacities of AC-PEHA for Cd ions increase from 26.15 mgg^-1 to 53.58 mgg^-1 at initial Cd ions concentration of 10-350 mgL^-1 and pH of 5.0. The adsorption of Cd ions on AC-PEHA is more favourable under alkaline condition (pH=6-8). The maximum Cd ions desorption of 83.8% for AC-PEHA occurs with 30 gL^-1 HCl. Although the total pore volume and average pore width of AC decrease by 21.6% and 7.4% respectively after PEHA modification, the modification add more primary amine groups to AC pores, and it significantly enhances the Cd ions adsorption capacity of AC.