End-group protection as a novel strategy to prepare silica-gel supported diethylenetriamine with high adsorption capacities for metal ions

Four kinds of silica-gel supported diethylenetriamine adsorbents with different structures were prepared by so-called heterogeneous-direct-amination, homogeneous-direct-amination, heterogeneous end-group protection and homogeneous end-group protection methods, respectively. Our objective was to use a novel strategy of end-group protection to prepare the adsorbents with high adsorption capacities for metal ions. The structures of the resulting adsorbents were characterized by infrared spectroscopy (FT-IR), porous structure analysis and elemental analysis. Hg(II), Cu(II), Ni(II) and Pb(II) were chosen as representatives to assess their adsorption capability and the utilization ratio of N. The experimental results indicated that the adsorbents prepared by heterogeneous end-group protection and homogeneous end-group protection methods possessed lower contents of diethylenetriamine (DETA), while their adsorption capacities and the utilization ratios of N were much higher than the corresponding counterparts prepared by heterogeneous-direct-amination and homogeneous-direct-amination methods. The end-group protection method exhibited its advantage in preparation of effective adsorbent for metal ions uptake compared to the direct-amination method.