New nanoadsorbent based on magnetic iron oxide containing 1,4,7,10-tetraazacyclododecane in outer chain (Fe₃O₄@SiO₂-cyclen) for adsorption and removal of selected heavy metal ions Cd²⁺, Pb²⁺, Cu²⁺

Magnetic Fe₃O₄@SiO₂-cyclen nanoparticles were prepared and used as adsorbent for Cd²⁺, Pb²⁺ and Cu²⁺ from aqueous solution removal process controlled with differential pulse anodic stripping voltammetry (DPASV) and hanging mercury drop electrode (HDME). Nanomaterial was synthesised in three-step process co-precipitation of Fe₃O₄ core, coating with silane and N-(3-(triethoxysilyl)propyl)-1,4,7,10-tetraazacyclododecane-1-carboxamide silane functionalisation. The effectiveness of each step of the synthesis was confirmed using scanning electron microscopy (SEM), high-resolution X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (pXRD) and fourier-transform infrared spectroscopy (FT-IR) techniques. The Fe₃O₄@SiO₂-cyclen nanoparticles were employed for Cd²⁺, Pb²⁺ and Cu²⁺ ions elimination from individual and mixed solutions by carrying out titration with a suspension of nanocomposites. The binding level for all ions both in the individual solutions and in the mixture was very similar at high levels. For Cd²⁺ and Cu²⁺ ions sorption efficiency level was from 83% to 89%, while for Pb²⁺ ions it was slightly lower at the level over 73%. In all cases, the equilibrium adsorption capacity parameter was over 1 mg/g and reached definitely higher values for individual ions solutions. The research results revealed that Fe₃O₄@SiO₂- cyclen nanoparticles can be a promising adsorbent for magnetic heavy metal ions water treatment agents.