| Because iminodiacetic acid chain section is typical of tridentate ligand group, which contains two carboxyls and one amino group, so this composite chelating particles have a strong adsorption action towards a variety of rare earth and heavy metal ions. In the paper, glycidyl methacrylate (GMA) was grafted on micron-sized silica gel particles, obtaining the grafted particles PGMA/SiO2. Subsequently, the ring-opening reaction of the epoxy groups of the grafted PGMA was carried out with iminodiacetic acid (IDAA) as reaction reagent, resulting in the bonging of IDAA groups and the preparing of the composite chelating particles IDAA-PGMA/SiO2. In this work, the adsorption behavior and adsorption thermodynamics of IDAA-PGMA/SiO2 for heavy metal ions and rare earth ions were mainly investigated, and the adsorption mechanism was researched in depth. The research of this paper is of obviously scientific significance and has referenced values,especially in the field of environmental protection.Glycidyl methacrylate (GMA) was grafted on micron-sized silica gel particles in a manner of"grafting from"in a solution polymerization system by right of the mediation of the coupling agentγ-methacryloxypropyl trimethoxysilane (KH570), resulting in the grafted particles PGMA/SiO2.Subsequently, the ring-opening reaction of the epoxy groups of the grafted PGMA was carried out with iminodiacetic acid (IDAA) as reaction reagent, resulting in the introducing of IDAA groups and obtaining the composite chelating particles IDAA-PGMA/SiO2.The two kinds of particles were characterized with FTIR methods. The amount of the epoxy groups and the bonding ration of IDAA group were tested by chemical analysis and weighing method, respectively. The exper- imental results show that in the graft polymerization process, the grafting degree of PGMA can get up to 23.55g/100g under a proper reaction condition. The suitable reaction conditions are as follows: temperature is 70℃, the amount of monomer is 11 mL , concentration of initiator is 1.4% and reaction time=20h. The ring-opening reaction of the epoxy groups of the grafted PGMA should be processed under higher pH conditions,when pH=12.5, the bonding ration of IDAA group can reach 70%.In this work, the chelating adsorption behaviours of IDAA-PGMA/SiO2 towards several heavy metal ions were examined, the adsorption mechanism and adsorption thermodynamics were mainly studied. The experimental results show that the composite-type chelating adsorption material IDAA-PGMA/SiO2 has strong chelating adsorption ability for heavy metal ions by right of the synergy of electronic interaction and coordination chelation between iminodiacetic acid groups of IDAA-PGMA/SiO2 and heavy metal ions. Especially, IDAA-PGMA/SiO2 possesses very strong chelating adsorption ability for Pb2+ ion, and the adsorption capacity can get up to 24g/100g at 30℃. The adsorption process of IDAA-PGMA/SiO2 towards heavy metal ions is exothermic, and it is a process driven by enthalpy, leading to the decrease of the adsorption capacity with raising temperature. In a pH range in which the hydrolysis of heavy metal ions can be inhibited, to increase pH value of the medium will strengthen the chelation adsorption ability of the composite-type chelating adsorption material IDAA-PGMA/SiO2 towards heavy ions. For the different metal ions, IDAA-PGMA/SiO2 exhibits different adsorption abilities, and the order of the adsorption capacity is Pb2+>Cd2+>Ni2+.In this work,we also examined the chelating adsorption behaviours of IDAA-PGMA/SiO2 towards several rare earth ions, the adsorption mechanism and adsorption thermodynamics were mainly studied. The experimental results show that the composite-type chelating adsorption material IDAA-PGMA/SiO2 also has strong chelating adsorption ability for rare earth ions, the adsorption capacity of IDAA-PGMA/SiO2 can get up to 9.5g/100g at 30℃.The adsorption process of IDAA-PGMA/SiO2 towards rare earth ions is endothermic, and it is a process driven by entropy, leading to the increase of the adsorption capacity with raising temperature. Because of the similitude of physicochemical properties of lanthanide elements, the adsorption capacity of IDAA-PGMA/SiO2 towards several rare earth ions is very close . From here we see that the composite-type chelating adsorption material IDAA-PGMA/ SiO2 lacks the selectivity of adsorbents towards rare earth ions.
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