2.2. Surface treatment of PAA and preparation of magnetite/silica/
titania photocatalyst
In order to increase binding capacity, the surface of Fe3O4/SiO2
was modified by flexible polymer chains of PAA. 0.58 g Fe3O4/
SiO2 powder and 20 mL PAA were sonicated in 150 mL dimethylformamide
for 30 min. And then it was filtered, washed with ethanol
and dried in vacuum.
0.334 g PAA-treated Fe3O4/SiO2 powder and 2.5 mL water were
dispersed into 280 mL ethanol with the aid of ultrasonic agitation
and the system was heat to 85 C Celsius. A mixture of several milliliter
of titanium n-butoxide (TBOT) and 50 mL ethanol was introduced
into Fe3O4/SiO2 solution drop by drop and the reaction was
maintained at 85 C for 3 h. The reaction system was sealed to keep
solvent from evaporating. The product obtained by magnetic separation
was washed with ethanol by ultrasonication followed by
magnetic separation several times, and finally annealed at 500 C
in N2 for 2 h in order to improve the crystallinity of the titania.
In order to study the effect of PAA, control experiment without
PAA treatment was also conducted. The sample codes and preparation
parameters are presented in Table 1.