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RSC Advances
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DOI: 10.1039/C5RA07536J
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the absorbance at 554 nm and taken the initial concentration
as C0. After the elapse of a period of time, 4 ml of the solution
was taken and filtered by the 0.22 μm membrane in order to
separate the catalyst powders from the solution, where the
instantaneous concentration of RhB was measured at different
time as C.
In the recycling experiments, the solution was deposited for
about one hour to avoid the loss of the catalyst and the
precipitate was centrifuged to collect the photocatalyst after
the added RhB was almost degraded. It was washed with
deionized water as well as ethanol for several times and then
dried at room temperature. Then the final products were
suspended in a fresh solution of RhB and PMS, followed by
RhB degradation as the second cycle. This process was
repeated as the third cycle.
Scheme 1. Mechanism for RhB degradation by BiFeO3/PMS/Vis system
To confirm the contribution of the oxidizing radical species,
ethanol (EtOH), t-butanol (t-BuOH) and 1,4-benzoquinone (BQ)
were employed as radical scavengers. Quenching experiments
were performed by adding the scavengers into the reaction
solution before the participation of PMS.
better for the degradation of RhB. A suitable mechanism is
suggested to explain the observed photocatalyzed degradation
of RhB. These results demonstrate that BiFeO3/PMS behaves
as an efficient material in photocatalytic oxidation of organic
pollutants.
Catalyst characterization
The crystal structure of dried powders was characterized from
the X-ray powder diffraction (XRD) patterns using a Rigaku
D/MAX 2550 diffractometer with Cu Kα radiation (λ = 1.5418
Å). Scanning electron microscopy (SEM) images were taken by
a JEOL JSM-6700F microscope at 10 kV. The UV-Vis absorption
spectra of the samples were measured using TU-1901
ultraviolet / visible optical absorption spectrometry. UV–Vis
diffuse reflectance spectroscopic (DRS) studies were carried
out using a Shimadzu UV-3600 equipped with an integrating
sphere at the room temperature in air, and BaSO4 was used as
the reference material.
Experiment
Synthesis of BiFeO3
BiFeO3 was fabricated by hydrothermal method. In a typical
synthesis, 0.1 mol Fe(NO3)3·9H2O and 0.1 mol Bi(NO3)3·5H2O
were used as raw materials and were dissolved in 15 mL of
distilled water, the amount of KOH was added as a mineralizer,
after stirring for half an hour, the brown suspension were
transferred into Teflon-lined stainless steel autoclave, the
autoclave was then sealed and heated at 200
℃ for 6 h. After
cooling to room temperature naturally, the precipitates were
collected by vacuum filtration and washed with distilled water
until a pH of 7 was obtained. Then, the produced powder was
dried at room temperature.
Acknowledgements
This work was supported by Open Research Fund Program of
State Key Laboratory of Inorganic Synthesis and Preparative
Chemistry (No. 2014-31) and Youth Foundation of Anhui
University of Technology.
Catalytic degradation experiments
Photocatalytic activities of the samples were evaluated by the
degradation of RhB with a 500 W xenon (Xe) lamp, which
positioned in a quartz cold trap with flowing cold water to
avoid overheat caused by lamp long time irritation. The cutoff
filters (λ ≥ 420 nm) were used to remove radiation below 420
nm. The degradation experiments were carried out in a
cylindrical Pyrex vessel (250 mL). The vessel with 200 mL RhB
(5 mg L-1) solution was put into the thermostatic oil bath
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Chi, Fangli
