Fabrication of phosphate-imprinted PNIPAM/SiO 2 hybrid particles and their phosphate binding property

Abstract

A SiO 2 microsphere imprinted by phosphate ions was prepared with the use of phosphate ion as the template molecule and tetraethoxysilane as the precursor. Thereafter, the imprinted SiO 2 microspheres were modified with 3-(trimethoxysilyl)propyl methacrylate (TMSPMA@SiO 2 ), followed by introducing the double bond. In the presence of TMSPMA@SiO 2 , using N-isopropylacrylamide as monomer, and potassium persulfate as initiator, polymer/inorganic hybrid particles (PNIPAM/SiO 2 ) were prepared. Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption-desorption test, and transmission electron microscope were employed for the characterization of molecular imprinted SiO 2 microspheres and PNIPAM/SiO 2 hybrid particles. The effects of phosphate concentration, pH value, and adsorption temperature on the phosphate binding properties of PNIPAM/SiO 2 hybrid particles were studied by UV-vis spectrophotometer. The experimental results shed light on the fact that the PNIPAM structure is beneficial for the improvement of the adsorption ability of phosphate-imprinted SiO 2 microspheres. With the increase in the initial phosphate concentration, the adsorption capacity of hybrid particles to phosphate ions increased to 274 mg/g at pH = 7 and 15 °C. The acid condition and the temperature below the low critical solution temperature (LCST) of PNIPAM are favorable to the adsorption of phosphate ions by PNIPAM/SiO 2 hybrid particles, and the maximum adsorption capacity can reach 287 mg/g (at pH = 5 and 15 °C). The phosphate imprinted polymer/inorganic hybrid material is expected to be put to use in the fields of phosphate ions adsorption, separation, and recovery.