Synthesis and characterization of Schiff-base based chitosan-g-glutaraldehyde/NaMMTNPs-APTES for removal Pb²⁺ and Hg²⁺ ions

In this paper, a new Schiff base based on porous chitosan-glutaraldehyde /montmorrilonite nanoparticles modified with 3-aminopropyl triethoxysilane (PCG/ NaMMTNPs-APTES) nanocomposite was prepared using cationic copolymerization technique. The structure of the biosorbents was characterized using FTIR, SEM, TEM, DSC, TGA/DTG, BET, DLS and Zeta potential analysis. The BET technique is demonstrating the further surface area and porosity of the PCG/NaMMTNPs-APTES in compare to the non-modified porous chitosan-glutaraldehyde, PCG. TGA/DTG and DSC results revealed a clear difference in thermal stability, so that; the nanocomposite exhibited significantly thermal stability in compared to the PCG hydrogel at high temperature. The obtained biosorbent hydrogels were also investigated as the adsorbents for removal of heavy metals and methylene blue dye from the aqueous solution by AAS and UV-vis techniques, respectively. The results showed that the maximum removal percentage of Pb²⁺ and Hg²⁺ ions for PCG/NaMMTNPs-APTES and PCG was achieved 94.16, 85.27% and 80.83, 70.27% in pH 6.5 and pH 6.0 for 40 min, respectively. The obtained results are described using the adsorption kinetics and desorption isotherm models. Furthermore, the thermodynamic parameters on the sorption possess was evaluated.