Highly enhanced adsorption of lead ions on chitosan granules functionalized with poly(acrylic acid)

Cross-linked chitosan granules (denoted as CTS) were surface-functionalized with poly(acrylic acid) (PAAc) and examined for the adsorption of lead ions from aqueous solutions. PAAc was successfully grafted on CTS through a simple two-step reaction in a solution. The PAAc-functionalized chitosan granules (denoted as CTS-PAAc) showed significantly greater adsorption capacities for lead ions than CTS, and the performance improved with the increase of pH in the pH range of 1-6 examined. An adsorption isotherm and kinetic study conducted at pH 4 and room temperature showed a maximum adsorption capacity of 294.12 mg/g and an adsorption equilibrium time of less than 5 h for lead ions on CTS-PAAC, in contrast to only 95.15 mg/g and up to 8 h on CTS. Mechanism study revealed that the excellent adsorption performance of CTS-PAAc for lead ions was attributed to the many carboxyl groups grafted on CTS-PAAc. It was found that adsorbed lead ions on CTS-PAAc can be effectively desorbed and the regenerated CTS-PAAc can be reused almost without any loss of adsorption capacity.