Surfactant-modified chitosan beads for cadmium ion adsorption.

Cadmium is one of the most toxic heavy metals, which has been classified as human carcinogen and tetratogen. In the present study chitosan (CS) beads are modified, in a novel way, using sodium dodecyl sulfate (SDS), a well known anionic surfactant. The concentration of SDS has been judiciously selected to form surfactant bilayers on CS surface. These modified beads are designated as surfactant-modified chitosan (SMCS) beads. The adsorbent has been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The SMCS beads are used as an adsorbent for Cd ion removal (in the initial concentration range of 10-100mg/L) from aqueous medium. The removal follows pseudo-second order kinetic model. SMCS beads show adsorption capacity three times higher than normal CS beads. Adsorption isotherm data fits well to the Langmuir model. The maximum adsorption capacity obtained is 125mg/g. Removal efficiency reached to almost 100% at SMCS dosage of 0.45g/L for lower concentration (10-30mg/L) of Cd ion in 10h, whereas, for higher concentration (40-100mg/L) the removal was ca. 50%.