Uptake of heavy metal cations by chitosan-modified montmorillonite: Kinetics and equilibrium studies

The adsorption of Cu2+ and Ni2+ by chitosan-modified montmorillonite (CTS-modified MMT) was investigated. Kinetic analyses suggested that the adsorption of Cu2+ and Ni2+ by MMT, CTS, and CTS-modified MMT can be modeled using a pseudo-second-order kinetic equation. The adsorption isotherms clearly indicate that the adsorption follows the Langmuir equation. The adsorption of metal cations by CTS-modified MMT is thought to be attributable to the cation adsorption capacity of MMT and the ability of CTS to form complexes with metal ions. Desorption and re-adsorption experiments were also conducted to determine the possibility of reusing the synthesized adsorbent. Using a 100-mmol/L HNO3 solution, a desorption rate of approximately 90% was achieved for the CTS-modified MMT. The CTS-modified MMT obtained after desorption could achieve the same level of adsorption as fresh the CTS-modified MMT, indicating that this adsorbent can be reused.