The grafting of amine groups onto SiO2foam was carried out as follows. 0.25 g of silica foam was introduced in a three neck flask with 30 ml of ethanol and 10 ml of water and stirred at room temperature for 1 h for complete dispersion, then oxalic acid was dropped in to adjusted the pH of the dispersion to 4, followed by dropwise addition of 0.5 ml of silane coupling agents (KH-550, KH-270) in half an hour.
The dispersion was further stirred at room temperature and then 60 C for 4 h, respectively.
The solid was fil-tered and washed with distilled water and ethanol for two times respectively and dried in vacuum at 80 C.
In the target samples the weight ratio of initial silica foam and that from silane coupling agent component is approximate to 1.
The controlled sample, bulk SiO2 particles were prepared by sol–gel process.
15 ml of ethanol solution containing 7.5 ml of TEOS was added dropwise to 100 ml of ethanol/water mixture (2/1) (con-taining 0.5 mol/l ammonium hydroxide) at a rate of 0.5 ml/min as the solution was heated to 60 C under stirring, where the reaction was continued for 2 h.
SiO2 particles were obtained after subse-quent steps of centrifugation, washing with water, ethanol, and drying in vacuum at 70 C
For clear understanding, bulk SiO2particles, SiO2foam, KH-550 and KH-270 modified SiO2foam were assigned as SiO2, F-SiO2, NH2-F-SiO2and NH-F-SiO2, respectively.