Synthesis of a nitrogen-rich dendrimer grafted on magnetic nanoparticles for efficient removal of Pb(ii) and Cd(ii) ions

Abstract

Rapid industrialization, urbanization, and human activities in catchments have presented a significant global challenge in removing heavy metal contaminants from wastewater. Here, a study was conducted to synthesize a nano-magnetic dendrimer based on a trimesoyl core that can be easily separated from the environment using an external magnet (Fe₃O₄@NR-TMD-G1, Fe₃O₄@NR-TMD-G2). The synthesized structure was characterized using various conventional techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and Brunauer–Emmett–Teller surface area analysis (BET). The prepared adsorbent showed good binding ability and excellent adsorption efficiency toward Pb(II) and Cd(II) metal ions from aqueous media (98.5%, 93.6%). The effect of different conditions including pH, adsorbate concentration, adsorbent dosage, isotherm, kinetics, and adsorption mechanism was considered. The highest adsorption efficiency was achieved at 25 °C and pH 4 using 0.08 g of Fe₃O₄@NR-TMD-G1, within 25 minutes for Pb(II) and 120 minutes for Cd(II), respectively. Batch adsorption experiments revealed that Fe₃O₄@NR-TMD-G1 was more effective in removing Pb(II) and Cd(II) compared to Fe₃O₄@NR-TMD-G2, with maximum capacities of 130.2 mg g⁻¹ and 57 mg g⁻¹, respectively. The adsorption process followed the Langmuir isotherm with a high correlation coefficient (R² = 0.9952, 0.9817) and non-linear pseudo-second-order kinetic model. Density functional theory (DFT) analysis indicated that the adsorbent transferred electrons to Pb(II) and Cd(II), forming stable chelates on the nanostructure surface. The heavy metal ions could be adsorbed by coordination to the heteroatoms of the nanostructure and also by electrostatic interactions. The recycled hybrid nanomaterial was dried and applied to different adsorption–desorption tests and the desorption efficiency was found to be 98%. So, the newly synthesized dendritic magnetic nanostructure demonstrated significant potential in efficient removal of metal ions from water and wastewater, highlighting its importance in addressing the global challenge of heavy metal contamination.