As shown in Fig. 3, for the non-catalytic system only 3.1% of TOC
was oxidized by H2O2 alone after 120 min. Meanwhile, about 15.1%
of TOC could be removed by the adsorption of FeOx/SBAC. However,
the TOC removal increased acutely to 61.7% with simultaneous
use of H2O2 and FeOx/SBAC, which could be ascribed to thecatalytic activity of FeOx/SBAC in HFO. Some previous studies have
pointed out that surface functional group and surface area are
crucial to heterogeneous catalytic oxidation, and it is generally recognized
that a catalyst with higher pHPZC and huge specific surface
area usually has a higher activity (Duan et al., 2014). Thus, the
strong catalytic activity of the prepared FeOx/SBAC was possibly
attributed to its huge specific surface area (302.5 m2/g) and high
pHPZC (6.39). Additionally, it was concluded that surface reaction
is the mechanism for FeOx/SBAC catalytic reaction since the catalytic
activity highly depends on TOC adsorption on FeOx/SBAC
surface.
In order to further investigate the mechanism, TBA was added
as radical scavenger to examine whether OH is the main oxidant
in the removal of TOC. Fig. 3 shows that TOC removal efficiency
decreased from 61.7% in 120 min without TBA to 15.9% with
50 mg/L of TBA in raw wastewater. This result indicated that the
process was dominated by hydroxyl radical oxidation.