Sorption of Pb(II) on carboxymethyl chitosan-conjugated magnetite nanoparticles: application of sorbent dosage-dependent isotherms.

Carboxymethyl chitosan (CMCS)-conjugated magnetite (FeO) nanoparticles (MNPs), which are denoted as CMCS-MNPs, were synthesized by covalently binding CMCS onto the surface of the MNPs via carbodiimide activation in a paraffin-acetic acid medium. The CMCS-MNPs exhibited a high level of CMCS binding (∼24.7 wt.%) and a spherical morphology with a mean diameter of 15 nm. In particular, they showed good water dispersity and a strong magnetic response. The sorption of Pb(II) on the CMCS-MNPs in aqueous solutions at different sorbent dosages ( C ), pH, electrolyte (NaNO) concentrations ( C ), and temperatures ( T) was investigated. The CMCS-MNPs showed high sorption capacity for Pb(II). The equilibrium amount increased with increasing pH but decreased with increasing C or T. In addition, a significant C -effect was observed in the sorption equilibria. Two C -dependent models, the Langmuir-SCA and Freundlich-SCA isotherms that were derived from a surface component activity (SCA) model, could describe the C -effect observed. The changes in pH, C , and T have no obvious influence on the C -effect. In addition, the changes in the thermodynamic parameters, ∆ G°, ∆ H°, and ∆ S°, for sorption were estimated, showing that the sorption process is spontaneous and exothermic. [ABSTRACT FROM AUTHOR]