MAGNETIC METAL IONS IMPRINTED MATERIALS BASED ON HUMIC ACIDS

Selective binding of the traced metals with humic acids (HA) has very important value for the removal of heavy metals and radio-nuclides from migration cycles. To increase the efficacy of the sorbents we have been used the principle of “adjustment” of polymeric complexes by the substrate (template) on the stage of their synthesis. The essence of the method is in the formation of HA complexes with the corresponding cations of metals and the subsequent cross-linking of their chains, that allows to fix the conformations of the molecules favourable for the binding of these ions. It will result in the growth of sorption capacity and the speed and selectivity of sorption on the “adjusted” polymeric sorbents.

A novel magnetic Cu(II)-imprinted nanocomposites (Fe₃O₄ @ Cu (II) IIMs) were prepared by cross-linking humic acids with m-aminophenol (APh). The synthesized nano-composites were characterized by FT-IR, TGA, SEM, N₂ adsorption-desorption, zeta potential measurements and vibrating sample magnetometer. The magnetic solid phase sorption characteristics were studied. The effects of various parameters on the extraction efficiency, such as pH of sample solution, the amount of adsorbent, extraction time, the type and concentration of eluent were systematically investigated. The thermodynamic and kinetic properties of the adsorption process were studied to explore the internal adsorption mechanism.

Removal of the Co (II), Ni(II), Cu(II) from the imprinted material and creation of cavities for hosting Cu(II) was proved by comparison of the response of IIM/HA/APh to template with that of non-imprinted material (NIM/HA/APh). The relative selectivity coefficients of Me-IIM for Cu(II)/Co(II), Cu(II)/Cd(II), Cu(II)/Zn(II), and Cu(II)/Pb(II) were determined. The experimental data fit with the Langmuir adsorption isotherm. The max Co-adsorption capacity obtained from the Langmuir isotherm is 134.09 mg/g for Co(II)-IIM. Co(II)-IIM can remove Co(II) ions with higher 96% from wastewater, which confirms it is good adsorbents for the removal of Co(II).

The developed method was successfully applied to the analysis of Cu (II) in different water samples with satisfactory results, proving its reliability and feasibility in real sample analysis. Another type of imprinted magnetic composites was magnetic composites with a core-inorganic shell structure obtained by immobilization on the surface of magnetite nanoparticles of silicon oxides (Fe3O4 /SiO2) by a sol-gel method, modifying the surface with HA and formalin as a cross-linking agent. As a substrate, Cu (II) was used. According to the data of the XRD analysis, the magnetite phase and average nanoparticle Fe3O4 size have no change after layer-by-layer functionalization.