Open AccessEffect of pH on the Catalytic Degradation of Rhodamine B by Synthesized CDs/g-C3N4/CuxO Composites
Author(s) -
Yulian Guo,
Cheng Zhou,
Lijuan Fang,
Zhongda Liu,
Li Wen,
Miao Yang
Publication year - 2021
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.0c05915
Subject(s) - rhodamine b , catalysis , x ray photoelectron spectroscopy , hydroxyl radical , electron paramagnetic resonance , chemistry , nuclear chemistry , citric acid , degradation (telecommunications) , desorption , fourier transform infrared spectroscopy , infrared spectroscopy , materials science , adsorption , radical , photocatalysis , chemical engineering , organic chemistry , telecommunications , physics , nuclear magnetic resonance , computer science , engineering
The narrow pH range of Fenton oxidation restricts its applicability in water pollution treatment. In this work, a CDs/g-C 3 N 4 /Cu x O composite was synthesized via a stepwise thermal polymerization method using melamine, citric acid, and Cu 2 O. Adding H 2 O 2 to form a heterogeneous Fenton system can degrade Rhodamine B (Rh B) under dark conditions. The synthesized composite was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N 2 adsorption/desorption isotherms. The results showed that CDs, Cu 2 O, and CuO were successfully loaded on the surface of g-C 3 N 4 . By evaluating the catalytic activity on Rh B degradation in the presence of H 2 O 2 , the optimal contents of citric acid and Cu 2 O were 3 and 2.8%, respectively. In contrast to a typical Fenton reaction, which is favored in acidic conditions, the catalytic degradation of Rh B showed a strong pH-dependent relation when the pH is raised from 3 to 11, with the removal from 45 to 96%. Moreover, the recyclability of the composite was evaluated by the removal ratio of Rhodamine B (Rh B) after each cycle. Interestingly, recyclability is also favored in alkaline conditions and shows the best performance at pH 10, with the removal ratio of Rh B kept at 95% even after eight cycles. Through free radical trapping experiments and electron spin resonance (ESR) analysis, the hydroxyl radical ( • OH) and the superoxide radical ( • O 2 - ) were identified as the main reactive species. Overall, a mechanism is proposed, explaining that the higher catalytic performance in the basic solution is due to the dominating surface reaction and favored in alkaline conditions.