Studies on Preparation of Composite Chelating Material Poly(amidoxime)/SiO2 with Grafting-Type

Abstract

Micron-sized silica gel particles were first surface-modified with a coupling agent, γ-methacryloylpropyl trimethoxysilane (MPS), so polymerizable double bonds were introduced onto the surfaces of silica gel particles. Then, acrylonitrile (AN) was graft polymerized on the surfaces of the modified particles in the manner of “grafting from”, resulting in the grafted particles PAN/SiO2. In succession, the grafted PAN was transformed into the grafted poly (amidoxime) (PAO) via aminoximation transformation reaction with hydroxylamine hydrochloride as a reaction reagent, and the composite chelating particles PAO/SiO2 with graft-type were obtained. In this work, the effects of main factors on the graft polymerization of AN and on the aminoximation transformation reaction were investigated in depth. At the same time, the chelating adsorption property of PAO/SiO2 particles for heavy metal ions and rare ions was preliminarily examined. The experiments results show that: (a) In graft polymerization, the reaction temperature and the used amount of initiator should be controlled to obtain the grafted particles with high grafting degree; (b) It is feasible to transform the grafted particles PAN/SiO2 into the functional particles PAO/SiO2 via aminoximation reaction, and the nitrile groups conversion can get up to 78%; (c) In aminoximation transformation reaction, the reaction temperature and the pH value of the medium should be selected as 70°C and pH=6-7, respectively. The experiment results also indicate that PAO/SiO2 particles possess a very strong chelating adsorption ability for heavy metal ions, Pb2+and Cu2+, and rare earth ions, Eu3+ and Sm3+, by right of the strong chelating action of amidoxime groups.