A new chitosan biopolymer derivative as metal-complexing agent: synthesis, characterization, and metal(II) ion adsorption studies

In this study, a new chitosan biopolymer derivative (CTSL) has been synthesized by anchoring a new vanillin-based complexing agent or ligand, namely 4-hydroxy-3-methoxy-5-[(4-methylpiperazin-1-yl)methyl] benzaldehyde, (L) with chitosan (CTS) by means of condensation. The new material was characterized by elemental (CHN), spectral (FTIR and solid state ¹³C NMR), thermal (TG-DTA and DSC), structural (powder XRD), and morphological (SEM) analyses. The CTSL was employed to study the equilibrium adsorption of various metal ions, namely, Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II), as functions of pH of the solutions. Its kinetics of adsorption was evaluated utilizing the pseudo first order and pseudo second order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The CTSL shows good adsorption capacity for metal ions studied in the order Cu(II) > Ni(II) > Cd(II) ? Co ? Mn(II) > Fe(II) > Pb(II) in all studied pH ranges due to the presence of many coordinating moieties present in it.