The surface of the SiO2 nanoparticles was modified with
the synthesized sodium oleate surfactant through the incipient wetness
method46 (link) considering different stock solutions
with surfactant concentrations of 9.0, 4.0, and 2.5% regarding the
mass of nanoparticles. After impregnation, the modified nanoparticles
were washed with deionized water in excess. The absorbance of the
effluent water was followed by UV–vis spectrophotometry using
a 60S UV–Visible Spectrophotometer (Thermo Fisher Scientific,
MA, USA) until the absorbance was the same as before washing. The
nanoparticles were separated by centrifugation using a Hermle Universal
Centrifuge Z360 (Hermle Labortechnik GmbH, Wehingen, DEU). Surface-modified
SiO2 nanoparticles (SNP-Y) will be named
according to the amount Y of surfactant grafted on
the surface. For instance, the SNP-2 material is composed of SiO2 nanoparticles with 2.4 wt % sodium oleate on the surface.
the synthesized sodium oleate surfactant through the incipient wetness
method46 (link) considering different stock solutions
with surfactant concentrations of 9.0, 4.0, and 2.5% regarding the
mass of nanoparticles. After impregnation, the modified nanoparticles
were washed with deionized water in excess. The absorbance of the
effluent water was followed by UV–vis spectrophotometry using
a 60S UV–Visible Spectrophotometer (Thermo Fisher Scientific,
MA, USA) until the absorbance was the same as before washing. The
nanoparticles were separated by centrifugation using a Hermle Universal
Centrifuge Z360 (Hermle Labortechnik GmbH, Wehingen, DEU). Surface-modified
SiO2 nanoparticles (SNP-Y) will be named
according to the amount Y of surfactant grafted on
the surface. For instance, the SNP-2 material is composed of SiO2 nanoparticles with 2.4 wt % sodium oleate on the surface.