Synthesis of micro-size magnetic polymer adsorbent and its application for the removal of Cu(II) ion

This study is aimed at the synthesis of micro-size magnetic polymer adsorbent (MPA) coupling with metal chelating ligands of iminodiacetic acid (IDA) and its application for the removal of Cu(II) ion. Firstly, the super-paramagnetic Fe3O4 called magnetite was prepared via the chemical co-precipitation method. The magnetite was then coated with polyvinyl acetate (PVAC) via the suspension polymerization with vinyl acetate (VAC), yielding magnetite-PVAC (denoted as M-PVAC). Several sequential procedures, including alcoholysis, epoxide activation, and coupling of IDA were subsequently employed to introduce functional groups on the surface of super-paramagnetite particles of M-PVAC, without demolishing the magnetite within the particles. The above sequential procedures yielded magnetite-polyvinyl alcohol (M-PVAL), magnetite-polyvinyl propenepoxide (M-PVEP), and magnetite-polyvinyl acetate-IDA (M-PVAC-IDA), respectively. Hence, the micro-size M-PVAC coupling with chelating ligands of IDA (denoted as M-PVAC-IDA) was manufactured with the desired chemical properties. The micro-size of about 1 μm and specified functional groups of metal chelating ligands of M-PVAC-IDA can provide large specific area of external surface and adsorbability of metal ions of adsorbent, respectively, which are essential to the adsorption. Moreover, after the use in adsorption, the exhausted M-PVAC-IDA with super-paramagnetic property can be separated from the solution via the applied magnetic force.As for the illustration of the application of M-PVAC-IDA, adsorption of Cu(II) ion, which can be chelated by the metal chelating ligands of IDA in aqueous solution was performed. Adsorption isotherms with pH values of 1, 2, and 4.5 at 25 °C were established. It was found that the adsorption capacity is highest at pH value of 4.5 while decreases as the pH value decreases. Thus, the exhausted M-PVAC-IDA after removing Cu(II) ion at moderate pH value of 4.5 can be regenerated at low pH value of 1.