(562ay) Degradation of N-Containing Pollutants By a Fenton-like Reaction with Cu-Based Catalysts

12.0pt;line-height:125%;font-family:" times new roman>Fenton reaction,
which can generate hydroxyl radical (•OH) with strong oxidative capacity to
decompose bio-refractory contaminants, is attracting more and more attention.
Comparing with conventional homogeneous Fenton reaction (Fe²⁺/H₂O₂),
Cu based heterogeneous catalyst is a more promising candidate for practical
application for no iron sludge and wider operation pH range.

12.0pt;line-height:125%;font-family:" times new roman>In this work,
Cu@SiO₂ with a plum pudding-like core shell structure was designed
and reduced at different temperature to identify the catalytic roles of Cu⁰,
Cu⁺ and Cu²⁺ species. Cu@SiO₂ reduced at 200
¡ãC (Cu@SiO₂-R200) exhibited the highest performance, and showed a
100% rhodamine B (10 ppm) removal within 30 min. Meanwhile, the
characterization results of CO-DRIFTS, UV-vis DRS, XPS and XANES suggested that
Cu⁺ concentration on the catalysts surface reached its maximum after
reducing at 200 ¡ãC, which indicated that the Cu⁺ was the primary
active site and produced ·OH.

12.0pt;line-height:125%;font-family:" times new roman>Comparing with Cu
based catalysts supported on SiO₂, Cu/Al₂O₃
could exhibit higher degradation efficiency at the same reaction condition.
However, Cu-doped mesoporous alumina showed almost no degradation effect on
nitrobenzene, which is an important material in chemical industries related to
pesticides, explosives, dyes and paper. We found that bimetallic
Fe-Cu catalysts could exhibit high performance in degradation of nitrobenzene. 5Fe2.5Cu-Al₂O₃
showed a 100% nitrobenzene (100 ppm) removal within 1 h, which was superior to
the nitrobenzene degradation efficiency over monometallic Fe and Cu catalysts_.
With combination of the catalytic performance and the characterization results
of XPS (Fig. 1) and H₂-TPR, we proposed that the synergistic effect
between Fe and Cu species played a vital role in promoting the reduction of Fe³⁺
to Fe²⁺, thus enhancing the generation of hydroxyl radicals (•OH)
and the degradation efficiency (Fig. 2).

Fig. 1. XPS spectra of synthesized
samples. (a) Fe 2p, (b) Cu 2p, (c) Cu LMM.

Fig.
2. The concentration of generated •OH using different catalysts (Reaction
conditions: 323 K, 1000 ppm H₂O₂, 1 g·L^-1
catalyst, 1500 ppm benzoic acid).

12.0pt;line-height:125%;font-family:" times new roman>Since the
Fenton-like reaction is usually followed by biological treatments, the
biocompatibility and biodegradability of the intermediate is of vital
importance in the whole remediation process. To clarify the reaction pathway,
we carried out an on-line analysis of the intermediate during NB degradation in
30 min using a GC-MS system. Combining our results with previous works, a
plausible reaction pathway for NB degradation for the Fe-Cu bimetallic
Fenton-like system was illustrated by Fig. 3. The electrophilic attack on the
benzene ring of NB was the predominant step. Besides, UV-Vis spectra (Fig.
4)and GC-MS results confirmed that no stable highly toxic 1,3-dinitrobenzene
existed throughout the reaction, indicating that this catalytic system can also
be readily coupled with a biodegradation process in the practical application.

Fig.
3. Proposed possible mechanism of NB degradation over 5Fe2.5Cu-Al₂O₃
in the presence of H₂O₂.

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Fig.
4. UV-Vis absorption spectra over 5Fe2Cu-Al₂O₃ during the
reaction time

12.0pt;line-height:125%;font-family:" times new roman>This work is
supported by National Natural Science Foundation of China under grant No.
21676157.