Agriculture Reference
In-Depth Information
reactor are as follows: during the treatment, the coil is not energized, and the
catalyst is evenly dispersed, having full contact with the organic matter in the
solution under aeration. After the treatment, the coil is energized and a strong
magnetic field is produced around the coil. As a result, the magnetic photocatalyst is
deposited at the bottom of the container, the treated solution is discharged through
the outlet, and the photocatalyst is left behind for the next batch of degradation.
In our experiments, two different magnetic carriers were prepared by burst
calcining and ultrasonic mixing, and the TiO
2
layer was loaded by the sol-gel
method to obtain photocatalysts with magnetic carrier (MT) and a porous material
(MCT), respectively. Subsequently, their morphologies, structures, and
photocatalytic abilities were investigated by employing characterization methods.
Scanning electron microscopy (SEM) revealed that the MT surface resembled that
of a honeycomb with a diameter of 1.5
m (Fig.
12.5
), whereas the MCT surface
was a piled structure with a specific surface area (BET) of 111.14 m
2
/g, which was
47 % larger than that of MT. Furthermore, X-ray diffraction (XRD) and X-ray
photoelectron spectroscopy (XPS) results showed that Fe and Ti were in the form of
Fe
3
O
4
and TiO
2
, respectively.
Figure
12.6
shows the adsorption and TC degradation curve of MT and MCT
under darkness and UV excitation, respectively. The adsorption capacity of MT was
significantly lower than that of MCT owing to its larger surface area, which was
consistent with the results of SEM and BET. Under the UV lamp, TC was degraded
by MT and MCT within 8 h with a removal rate of 90.0 and 88.7 %, respectively. At
the initial stage of the reaction, the degradation rate of TC by MT was higher than
that by MCT, and the removal rate at 1 h was 43 %, which was 10 % higher than that
exhibited by MCT, possibly because of the higher content of Ti (15.9 %). After 3 h,
the removal rates of TC presented by both MT and MCT decreased, and the
decrease was more prominent with respect to MT. TC was adsorbed onto the
surface of MCT because of its larger specific surface area, and the removal rate
of TC exhibited by MCT at the adsorption stage was 51.7 %, whereas that presented
by MT was only 26.9 %. Furthermore, the close contact between TC and TiO
2
was
more conducive for the catalytic degradation under UV light. In addition, the
overall removal efficiency of TC by MCT (including adsorption and photocatalytic
removal) was higher than that by MT (26.1 %). Subsequently, the photocatalytic
rate constants were calculated from the results: MCT
μ
0.2629 h
1
(
R
2
¼
¼
0.95) and
0.2156 h
1
(
R
2
MT
0.97). It was noted that both the absorption capacity and
photocatalytic activity of MCT were higher than those of MT.
¼
¼
